2015
Huang CH, Shih YY, Siow TY, Chen CC, Lin TN, Jaw FS, Chang C
Temporal assessment of vascular reactivity and functionality using MRI during postischemic proangiogenenic vascular RemodelingMagnetic Resonance ImagingPubMed
@article{CH2015,
title = {Temporal assessment of vascular reactivity and functionality using MRI during postischemic proangiogenenic vascular Remodeling},
author = {Huang CH, Shih YY, Siow TY, Chen CC, Lin TN, Jaw FS, Chang C
},
url = {https://pubmed.ncbi.nlm.nih.gov/25944092/},
doi = {10.1016/j.mri.2015.04.009},
year = {2015},
date = {2015-05-02},
urldate = {2015-05-02},
journal = {Magnetic Resonance Imaging},
volume = {33},
number = {7},
pages = {903-10},
abstract = {Postischemic angiogenesis is an important recovery mechanism. Both arteries and veins are upregulated during angiogenesis, but eventually there are more angiogenic veins than arteries in terms of number and length. It is critical to understand how the veins are modulated after ischemia and then transitioned into angiogenic vessels during the proangiogenic stage to finally serve as a restorative strength to the injured area. Using a rat model of transient focal cerebral ischemia, the hypercapnic blood oxygen level-dependent (BOLD) response was used to evaluate vascular reactivity, while the hyperoxic BOLD and tissue oxygen level-dependent (TOLD) responses were used to evaluate the vascular functionality at 1, 3, and 7days after ischemia. Vessel-like venous signals appeared on R2* maps on days 3 and 7, but not on day 1. The large hypercapnic BOLD responses on days 3 and 7 indicated that these areas have high vascular reactivity. The temporal correlation between vascular reactivity and the immunoreactivity to desmin and VEGF further indicates that the integrity of vascular reactivity is associated with the pericyte coverage as regulated by the VEGF level. Vascular functionality remained low on days 1, 3, and 7, as reflected by the small hyperoxic BOLD and large hyperoxic TOLD responses, indicating the low oxygen consumption of the ischemic tissues. These functional changes in proangiogenic veins may be critical for angiogenesis.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Postischemic angiogenesis is an important recovery mechanism. Both arteries and veins are upregulated during angiogenesis, but eventually there are more angiogenic veins than arteries in terms of number and length. It is critical to understand how the veins are modulated after ischemia and then transitioned into angiogenic vessels during the proangiogenic stage to finally serve as a restorative strength to the injured area. Using a rat model of transient focal cerebral ischemia, the hypercapnic blood oxygen level-dependent (BOLD) response was used to evaluate vascular reactivity, while the hyperoxic BOLD and tissue oxygen level-dependent (TOLD) responses were used to evaluate the vascular functionality at 1, 3, and 7days after ischemia. Vessel-like venous signals appeared on R2* maps on days 3 and 7, but not on day 1. The large hypercapnic BOLD responses on days 3 and 7 indicated that these areas have high vascular reactivity. The temporal correlation between vascular reactivity and the immunoreactivity to desmin and VEGF further indicates that the integrity of vascular reactivity is associated with the pericyte coverage as regulated by the VEGF level. Vascular functionality remained low on days 1, 3, and 7, as reflected by the small hyperoxic BOLD and large hyperoxic TOLD responses, indicating the low oxygen consumption of the ischemic tissues. These functional changes in proangiogenic veins may be critical for angiogenesis.
Lai HY, Albaugh DL, Kao YC, Younce JR, Shih YY
Robust deep brain stimulation functional MRI procedures in rats and mice using an MR-compatible tungsten microwire electrodeMagnetic Resonance in MedicinePubMed
@article{HY2014,
title = {Robust deep brain stimulation functional MRI procedures in rats and mice using an MR-compatible tungsten microwire electrode},
author = {Lai HY, Albaugh DL, Kao YC, Younce JR, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/24798216/},
doi = {10.1002/mrm.25239},
year = {2015},
date = {2015-03-01},
urldate = {2015-03-01},
journal = {Magnetic Resonance in Medicine},
volume = {73},
number = {3},
pages = {1246-51},
abstract = {Purpose
To develop a series of robust and readily adoptable protocols for the application of deep brain stimulation (DBS)-functional MRI (fMRI) in rodents.
Methods
DBS-fMRI procedures were conducted in rat and mouse under varying anesthetic conditions (isoflurane in rat and mouse, α-chloralose in rat). A homemade two-channel tungsten microwire electrode was used to minimize magnetic susceptibility artifacts, and was targeted to the ventral posteromedial (VPM) thalamus for DBS-fMRI scanning procedures.
Results
Compared with a commercially available MR-compatible electrode, the tungsten microwire generated greatly reduced magnetic-susceptibility artifacts. In the rat, VPM-DBS using the microwire electrode resulted in robust positive blood-oxygen-level-dependent signal changes in somatosensory cortex that were relatively independent of anesthetic type. In the mouse, VPM-DBS similarly generated large, positive neurovascular responses in somatosensory cortex that were detected using cerebral blood volume measurements.
Conclusion
Collectively, this work describes reasonable and easily adoptable procedures for conducting DBS-fMRI studies in rodent models. The protocols developed herein may be extended to study DBS effects under numerous experimental conditions and at varying stimulation targets.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Purpose
To develop a series of robust and readily adoptable protocols for the application of deep brain stimulation (DBS)-functional MRI (fMRI) in rodents.
Methods
DBS-fMRI procedures were conducted in rat and mouse under varying anesthetic conditions (isoflurane in rat and mouse, α-chloralose in rat). A homemade two-channel tungsten microwire electrode was used to minimize magnetic susceptibility artifacts, and was targeted to the ventral posteromedial (VPM) thalamus for DBS-fMRI scanning procedures.
Results
Compared with a commercially available MR-compatible electrode, the tungsten microwire generated greatly reduced magnetic-susceptibility artifacts. In the rat, VPM-DBS using the microwire electrode resulted in robust positive blood-oxygen-level-dependent signal changes in somatosensory cortex that were relatively independent of anesthetic type. In the mouse, VPM-DBS similarly generated large, positive neurovascular responses in somatosensory cortex that were detected using cerebral blood volume measurements.
Conclusion
Collectively, this work describes reasonable and easily adoptable procedures for conducting DBS-fMRI studies in rodent models. The protocols developed herein may be extended to study DBS effects under numerous experimental conditions and at varying stimulation targets.
To develop a series of robust and readily adoptable protocols for the application of deep brain stimulation (DBS)-functional MRI (fMRI) in rodents.
Methods
DBS-fMRI procedures were conducted in rat and mouse under varying anesthetic conditions (isoflurane in rat and mouse, α-chloralose in rat). A homemade two-channel tungsten microwire electrode was used to minimize magnetic susceptibility artifacts, and was targeted to the ventral posteromedial (VPM) thalamus for DBS-fMRI scanning procedures.
Results
Compared with a commercially available MR-compatible electrode, the tungsten microwire generated greatly reduced magnetic-susceptibility artifacts. In the rat, VPM-DBS using the microwire electrode resulted in robust positive blood-oxygen-level-dependent signal changes in somatosensory cortex that were relatively independent of anesthetic type. In the mouse, VPM-DBS similarly generated large, positive neurovascular responses in somatosensory cortex that were detected using cerebral blood volume measurements.
Conclusion
Collectively, this work describes reasonable and easily adoptable procedures for conducting DBS-fMRI studies in rodent models. The protocols developed herein may be extended to study DBS effects under numerous experimental conditions and at varying stimulation targets.
Liao LD, Liu YH, Lai HY, Bandla A, Shih YY, Chen YY, Thakor NV
Rescue of cortical neurovascular functions during the hyperacute phase of ischemia by peripheral sensory stimulation@article{LD2015,
title = {Rescue of cortical neurovascular functions during the hyperacute phase of ischemia by peripheral sensory stimulation},
author = {Liao LD, Liu YH, Lai HY, Bandla A, Shih YY, Chen YY, Thakor NV},
url = {https://pubmed.ncbi.nlm.nih.gov/25573087/},
doi = {10.1016/j.nbd.2014.12.022},
year = {2015},
date = {2015-01-05},
urldate = {2015-01-05},
journal = {Neurobiology of Disease},
volume = {75},
pages = {53-63},
abstract = {To investigate the potential therapeutic effects of peripheral sensory stimulation during the hyperacute phase of stroke, the present study utilized electrophysiology and photoacoustic imaging techniques to evaluate neural and vascular responses of the rat cortex following ischemic insult. We employed a rat model of photothrombotic ischemia (PTI), which targeted the forelimb region of the primary somatosensory cortex (S1FL), due to its high reproducibility in creating localized ischemic injury. We also established a hybrid, dual-modality system, including six-channel electrocorticography (ECoG) and functional photoacoustic microscopy (fPAM), termed ECoG–fPAM, to image brain functional responses to peripheral sensory stimulation during the hyperacute phase of PTI. Our results showed that the evoked cerebral blood volume (CBV) and hemoglobin oxygen saturation (SO2) recovered to 84 ± 7.4% and 79 ± 6.2% of the baseline, respectively, when stimulation was delivered within 2.5 h following PTI induction. Moreover, neural activity significantly recovered, with 77 ± 8.6%, 76 ± 5.3% and 89 ± 8.2% recovery for the resting-state inter-hemispheric coherence, alpha-to-delta ratio (ADR) and somatosensory evoked potential (SSEP), respectively. Additionally, we integrated the CBV or SO2 with ADR values as a recovery indicator (RI) to assess functional recovery after PTI. The RI indicated that 80 ± 4.2% of neurovascular function was preserved when stimulation was delivered within 2.5 h. Additionally, stimulation treatment within this optimal time window resulted in a minimal infarct volume in the ischemic hemisphere (4.6 ± 2.1%). In contrast, the infarct volume comprised 13.7 ± 1.7% of the ischemic hemisphere when no stimulation treatment was applied.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
To investigate the potential therapeutic effects of peripheral sensory stimulation during the hyperacute phase of stroke, the present study utilized electrophysiology and photoacoustic imaging techniques to evaluate neural and vascular responses of the rat cortex following ischemic insult. We employed a rat model of photothrombotic ischemia (PTI), which targeted the forelimb region of the primary somatosensory cortex (S1FL), due to its high reproducibility in creating localized ischemic injury. We also established a hybrid, dual-modality system, including six-channel electrocorticography (ECoG) and functional photoacoustic microscopy (fPAM), termed ECoG–fPAM, to image brain functional responses to peripheral sensory stimulation during the hyperacute phase of PTI. Our results showed that the evoked cerebral blood volume (CBV) and hemoglobin oxygen saturation (SO2) recovered to 84 ± 7.4% and 79 ± 6.2% of the baseline, respectively, when stimulation was delivered within 2.5 h following PTI induction. Moreover, neural activity significantly recovered, with 77 ± 8.6%, 76 ± 5.3% and 89 ± 8.2% recovery for the resting-state inter-hemispheric coherence, alpha-to-delta ratio (ADR) and somatosensory evoked potential (SSEP), respectively. Additionally, we integrated the CBV or SO2 with ADR values as a recovery indicator (RI) to assess functional recovery after PTI. The RI indicated that 80 ± 4.2% of neurovascular function was preserved when stimulation was delivered within 2.5 h. Additionally, stimulation treatment within this optimal time window resulted in a minimal infarct volume in the ischemic hemisphere (4.6 ± 2.1%). In contrast, the infarct volume comprised 13.7 ± 1.7% of the ischemic hemisphere when no stimulation treatment was applied.
2014
Yang DJ, Pham L, Liao MH, Kong FL, Uemura H, Shih YY
Advances in molecular pathway-directed cancer systems imaging and therapyBioMed Research InternationalPubMed
@article{DJ2014,
title = {Advances in molecular pathway-directed cancer systems imaging and therapy},
author = {Yang DJ, Pham L, Liao MH, Kong FL, Uemura H, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/25587538/},
doi = {10.1155/2014/639475},
year = {2014},
date = {2014-12-21},
urldate = {2014-12-21},
journal = {BioMed Research International},
volume = {2014},
number = {2014},
pages = {639475},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kao YC, Li W, Lai HY, Oyarzabal EA, Lin W, Shih YY
Dynamic perfusion and diffusion MRI of cortical spreading depolarization in photothrombotic ischemia@article{YC2014,
title = {Dynamic perfusion and diffusion MRI of cortical spreading depolarization in photothrombotic ischemia},
author = {Kao YC, Li W, Lai HY, Oyarzabal EA, Lin W, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/25066776/},
doi = {10.1016/j.nbd.2014.07.005},
year = {2014},
date = {2014-11-01},
urldate = {2014-11-01},
journal = {Neurobiology of Disease},
volume = {71},
pages = {131-139},
abstract = {Cortical spreading depolarization (CSD) is known to exacerbate ischemic damage, as the number of CSDs correlates with the final infarct volumes and suppressing CSDs improves functional outcomes. To investigate the role of CSD in ischemic damage, we developed a novel rat model of photothrombotic ischemia using a miniature implantable optic fiber that allows lesion induction inside the magnetic resonance imaging (MRI) scanner. We were able to precisely control the location and the size of the ischemic lesion, and continuously monitor dynamic perfusion and diffusion MRI signal changes at high temporal resolution before, during and after the onset of focal ischemia. Our model showed that apparent diffusion coefficient (ADC) and cerebral blood flow (CBF) in the ischemic core dropped immediately after lesion onset by 20 ± 6 and 41 ± 23%, respectively, and continually declined over the next 5 h. Meanwhile, CSDs were observed in all animals (n = 36) and displayed either a transient decrease of ADC by 17 ± 3% or an increase of CBF by 104 ± 15%. All CSDs were initiated from the rim of the ischemic core, propagated outward, and confined to the ipsilesional cortex. Additionally, we demonstrated that by controlling the size of perfusion–diffusion mismatch (which approximates the penumbra) in our model, the number of CSDs correlated with the mismatch area rather than the final infarct volume. This study introduces a novel platform to study CSDs in real-time with high reproducibility using MRI.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Cortical spreading depolarization (CSD) is known to exacerbate ischemic damage, as the number of CSDs correlates with the final infarct volumes and suppressing CSDs improves functional outcomes. To investigate the role of CSD in ischemic damage, we developed a novel rat model of photothrombotic ischemia using a miniature implantable optic fiber that allows lesion induction inside the magnetic resonance imaging (MRI) scanner. We were able to precisely control the location and the size of the ischemic lesion, and continuously monitor dynamic perfusion and diffusion MRI signal changes at high temporal resolution before, during and after the onset of focal ischemia. Our model showed that apparent diffusion coefficient (ADC) and cerebral blood flow (CBF) in the ischemic core dropped immediately after lesion onset by 20 ± 6 and 41 ± 23%, respectively, and continually declined over the next 5 h. Meanwhile, CSDs were observed in all animals (n = 36) and displayed either a transient decrease of ADC by 17 ± 3% or an increase of CBF by 104 ± 15%. All CSDs were initiated from the rim of the ischemic core, propagated outward, and confined to the ipsilesional cortex. Additionally, we demonstrated that by controlling the size of perfusion–diffusion mismatch (which approximates the penumbra) in our model, the number of CSDs correlated with the mismatch area rather than the final infarct volume. This study introduces a novel platform to study CSDs in real-time with high reproducibility using MRI.
Shih YY, Huang S, Chen YY, Lai HY, Kao YC, Hui E, Duong TQ
Imaging neurovascular function and functional recovery after stroke in the rat striatum using forepaw stimulationJournal of Cerebral Blood Flow and MetabolismPubMed
@article{YY2014,
title = {Imaging neurovascular function and functional recovery after stroke in the rat striatum using forepaw stimulation},
author = {Shih YY, Huang S, Chen YY, Lai HY, Kao YC, Hui E, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/24917039/},
doi = {10.1038/jcbfm.2014.103},
year = {2014},
date = {2014-09-02},
urldate = {2014-09-02},
journal = {Journal of Cerebral Blood Flow and Metabolism},
volume = {34},
number = {9},
pages = {1483-92},
abstract = {Negative functional magnetic resonance imaging (fMRI) response in the striatum has been observed in several studies during peripheral sensory stimulation, but its relationship between local field potential (LFP) remains to be elucidated. We performed cerebral blood volume (CBV) fMRI and LFP recordings in normal rats during graded noxious forepaw stimulation at nine stimulus pulse widths. Albeit high LFP-CBV correlation was found in the ipsilateral and contralateral sensory cortices (r = 0.89 and 0.95, respectively), the striatal CBV responses were neither positively, nor negatively correlated with LFP (r = 0.04), demonstrating that the negative striatal CBV response is not originated from net regional inhibition. To further identify whether this negative CBV response can serve as a marker for striatal functional recovery, two groups of rats (n = 5 each) underwent 20- and 45-minute middle cerebral artery occlusion (MCAO) were studied. No CBV response was found in the ipsilateral striatum in both groups immediately after stroke. Improved striatal CBV response was observed on day 28 in the 20-minute MCAO group compared with the 45-minute MCAO group (P<0.05). This study shows that fMRI signals could differ significantly from LFP and that the observed negative CBV response has potential to serve as a marker for striatal functional integrity in rats.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Negative functional magnetic resonance imaging (fMRI) response in the striatum has been observed in several studies during peripheral sensory stimulation, but its relationship between local field potential (LFP) remains to be elucidated. We performed cerebral blood volume (CBV) fMRI and LFP recordings in normal rats during graded noxious forepaw stimulation at nine stimulus pulse widths. Albeit high LFP-CBV correlation was found in the ipsilateral and contralateral sensory cortices (r = 0.89 and 0.95, respectively), the striatal CBV responses were neither positively, nor negatively correlated with LFP (r = 0.04), demonstrating that the negative striatal CBV response is not originated from net regional inhibition. To further identify whether this negative CBV response can serve as a marker for striatal functional recovery, two groups of rats (n = 5 each) underwent 20- and 45-minute middle cerebral artery occlusion (MCAO) were studied. No CBV response was found in the ipsilateral striatum in both groups immediately after stroke. Improved striatal CBV response was observed on day 28 in the 20-minute MCAO group compared with the 45-minute MCAO group (P<0.05). This study shows that fMRI signals could differ significantly from LFP and that the observed negative CBV response has potential to serve as a marker for striatal functional integrity in rats.
Shih YY, De La Garza BH, Huang S, Li G, Wang L, Duong TQ
Comparison of retinal and cerebral blood flow between continuous arterial spin labeling MRI and fluorescent microsphere techniquesJournal of Magnetic Resonance ImagingPubMed
@article{YY2014b,
title = {Comparison of retinal and cerebral blood flow between continuous arterial spin labeling MRI and fluorescent microsphere techniques},
author = {Shih YY, De La Garza BH, Huang S, Li G, Wang L, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/24227681/},
doi = {10.1002/jmri.24407},
year = {2014},
date = {2014-09-01},
urldate = {2014-09-01},
journal = {Journal of Magnetic Resonance Imaging},
volume = {40},
number = {3},
pages = {609-15},
abstract = {PURPOSE:
To compare basal retinal and cerebral blood flow (BF) values using continuous arterial spin labeling (CASL) MRI and fluorescent microspheres.
MATERIALS AND METHODS:
A total of 41 animals were used. BF was measured using an established microsphere technique (a mixture of 2.5 million 8 μm green and 0.5 million 10 μm blue fluorescent microspheres) and CASL MRI blood flow measurement in the rat retina and brain at 7 Tesla (T) and 11.7T, respectively.
RESULTS:
Retinal BF by MRI was 1.18 ± 0.57 mL/g/min and choroidal BF was 8.14 ± 1.8 mL/g/min (n = 6). Microsphere retinal BF was 9.12 ± 2.8 μL/min per tissue and choroidal BF was 73.38 ± 44 μL/min per tissue (n = 18), corresponding to a retinal BF value of 1.22 ± 0.36 mL/g/min by means of a wet weight conversion. The wet-weight of the choroid could not be determined. To corroborate our findings, cerebral BF (CBF) by MRI was also analyzed. In the cerebral cortices, CBF was 0.91 ± 0.29 mL/g/min (n = 14) by CASL MRI and 1.09 ± 0.37 mL/g/min (n = 6) by microspheres. There were no significant differences found between MRI and microsphere blood flow in the retina and brain.
CONCLUSION:
BF values in the rat retina and cerebral cortex by MRI are in agreement with those obtained by the microsphere technique.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
PURPOSE:
To compare basal retinal and cerebral blood flow (BF) values using continuous arterial spin labeling (CASL) MRI and fluorescent microspheres.
MATERIALS AND METHODS:
A total of 41 animals were used. BF was measured using an established microsphere technique (a mixture of 2.5 million 8 μm green and 0.5 million 10 μm blue fluorescent microspheres) and CASL MRI blood flow measurement in the rat retina and brain at 7 Tesla (T) and 11.7T, respectively.
RESULTS:
Retinal BF by MRI was 1.18 ± 0.57 mL/g/min and choroidal BF was 8.14 ± 1.8 mL/g/min (n = 6). Microsphere retinal BF was 9.12 ± 2.8 μL/min per tissue and choroidal BF was 73.38 ± 44 μL/min per tissue (n = 18), corresponding to a retinal BF value of 1.22 ± 0.36 mL/g/min by means of a wet weight conversion. The wet-weight of the choroid could not be determined. To corroborate our findings, cerebral BF (CBF) by MRI was also analyzed. In the cerebral cortices, CBF was 0.91 ± 0.29 mL/g/min (n = 14) by CASL MRI and 1.09 ± 0.37 mL/g/min (n = 6) by microspheres. There were no significant differences found between MRI and microsphere blood flow in the retina and brain.
CONCLUSION:
BF values in the rat retina and cerebral cortex by MRI are in agreement with those obtained by the microsphere technique.
To compare basal retinal and cerebral blood flow (BF) values using continuous arterial spin labeling (CASL) MRI and fluorescent microspheres.
MATERIALS AND METHODS:
A total of 41 animals were used. BF was measured using an established microsphere technique (a mixture of 2.5 million 8 μm green and 0.5 million 10 μm blue fluorescent microspheres) and CASL MRI blood flow measurement in the rat retina and brain at 7 Tesla (T) and 11.7T, respectively.
RESULTS:
Retinal BF by MRI was 1.18 ± 0.57 mL/g/min and choroidal BF was 8.14 ± 1.8 mL/g/min (n = 6). Microsphere retinal BF was 9.12 ± 2.8 μL/min per tissue and choroidal BF was 73.38 ± 44 μL/min per tissue (n = 18), corresponding to a retinal BF value of 1.22 ± 0.36 mL/g/min by means of a wet weight conversion. The wet-weight of the choroid could not be determined. To corroborate our findings, cerebral BF (CBF) by MRI was also analyzed. In the cerebral cortices, CBF was 0.91 ± 0.29 mL/g/min (n = 14) by CASL MRI and 1.09 ± 0.37 mL/g/min (n = 6) by microspheres. There were no significant differences found between MRI and microsphere blood flow in the retina and brain.
CONCLUSION:
BF values in the rat retina and cerebral cortex by MRI are in agreement with those obtained by the microsphere technique.
Shih YY, Yash TV, Rogers W, Duong TQ
fMRI of deep brain stimulation at the rat ventral posteromedial thalamus@article{YY2014b,
title = {fMRI of deep brain stimulation at the rat ventral posteromedial thalamus},
author = {Shih YY, Yash TV, Rogers W, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/24309153/},
doi = {10.1016/j.brs.2013.11.001},
year = {2014},
date = {2014-03-01},
urldate = {2014-03-01},
journal = {Brain Stimulation},
volume = {7},
number = {2},
pages = {190-3},
abstract = {Background
Functional magnetic resonance imaging (fMRI) of deep brain stimulation (DBS) has potentials to reveal neuroanatomical connectivity of a specific brain region in vivo.
Objective
This study aimed to demonstrate frequency and amplitude tunings of the thalamocortical tract using DBS fMRI at the rat ventral posteromedial thalamus.
Methods
Blood oxygenation level dependent (BOLD) fMRI data were acquired in a total of twelve rats at a high-field 11.7 T MRI scanner with modulation of nine stimulus frequencies (1–40 Hz) and seven stimulus amplitudes (0.2–3.6 mA).
Results
BOLD response in the barrel cortex peaked at 25 Hz. The response increased with stimulus amplitude and reached a plateau at 1 mA. Cortical spreading depolarization (CSD) was observed occasionally after DBS that carries >10% BOLD waves spanning the entire ipsilateral cortex.
Conclusion
fMRI is sensitive to the frequency effect of DBS and has potential to investigate the function of a particular neuroanatomical pathway.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background
Functional magnetic resonance imaging (fMRI) of deep brain stimulation (DBS) has potentials to reveal neuroanatomical connectivity of a specific brain region in vivo.
Objective
This study aimed to demonstrate frequency and amplitude tunings of the thalamocortical tract using DBS fMRI at the rat ventral posteromedial thalamus.
Methods
Blood oxygenation level dependent (BOLD) fMRI data were acquired in a total of twelve rats at a high-field 11.7 T MRI scanner with modulation of nine stimulus frequencies (1–40 Hz) and seven stimulus amplitudes (0.2–3.6 mA).
Results
BOLD response in the barrel cortex peaked at 25 Hz. The response increased with stimulus amplitude and reached a plateau at 1 mA. Cortical spreading depolarization (CSD) was observed occasionally after DBS that carries >10% BOLD waves spanning the entire ipsilateral cortex.
Conclusion
fMRI is sensitive to the frequency effect of DBS and has potential to investigate the function of a particular neuroanatomical pathway.
Functional magnetic resonance imaging (fMRI) of deep brain stimulation (DBS) has potentials to reveal neuroanatomical connectivity of a specific brain region in vivo.
Objective
This study aimed to demonstrate frequency and amplitude tunings of the thalamocortical tract using DBS fMRI at the rat ventral posteromedial thalamus.
Methods
Blood oxygenation level dependent (BOLD) fMRI data were acquired in a total of twelve rats at a high-field 11.7 T MRI scanner with modulation of nine stimulus frequencies (1–40 Hz) and seven stimulus amplitudes (0.2–3.6 mA).
Results
BOLD response in the barrel cortex peaked at 25 Hz. The response increased with stimulus amplitude and reached a plateau at 1 mA. Cortical spreading depolarization (CSD) was observed occasionally after DBS that carries >10% BOLD waves spanning the entire ipsilateral cortex.
Conclusion
fMRI is sensitive to the frequency effect of DBS and has potential to investigate the function of a particular neuroanatomical pathway.
Albaugh DL, Shih YY
Neural circuit modulation during deep brain stimulation at the subthalamic nucleus for Parkinson’s disease: What have we learned from neuroimaging studies?Brain Connectivity[Press release]PubMed
@article{DL2014,
title = {Neural circuit modulation during deep brain stimulation at the subthalamic nucleus for Parkinson’s disease: What have we learned from neuroimaging studies?},
author = {Albaugh DL, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/24147633/},
doi = {10.1089/brain.2013.0193},
year = {2014},
date = {2014-02-19},
urldate = {2014-02-19},
journal = {Brain Connectivity},
volume = {4},
number = {1},
pages = {1-14},
abstract = {Deep brain stimulation (DBS) targeting the subthalamic nucleus (STN) represents a powerful clinical tool for the alleviation of many motor symptoms that are associated with Parkinson's disease. Despite its extensive use, the underlying therapeutic mechanisms of STN-DBS remain poorly understood. In the present review, we integrate and discuss recent literature examining the network effects of STN-DBS for Parkinson's disease, placing emphasis on neuroimaging findings, including functional magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. These techniques enable the noninvasive detection of brain regions that are modulated by DBS on a whole-brain scale, representing a key experimental strength given the diffuse and far-reaching effects of electrical field stimulation. By examining these data in the context of multiple hypotheses of DBS action, generally developed through clinical and physiological observations, we define a multitude of consistencies and inconsistencies in the developing literature of this rapidly moving field.},
note = {invited review},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Deep brain stimulation (DBS) targeting the subthalamic nucleus (STN) represents a powerful clinical tool for the alleviation of many motor symptoms that are associated with Parkinson's disease. Despite its extensive use, the underlying therapeutic mechanisms of STN-DBS remain poorly understood. In the present review, we integrate and discuss recent literature examining the network effects of STN-DBS for Parkinson's disease, placing emphasis on neuroimaging findings, including functional magnetic resonance imaging, positron emission tomography, and single-photon emission computed tomography. These techniques enable the noninvasive detection of brain regions that are modulated by DBS on a whole-brain scale, representing a key experimental strength given the diffuse and far-reaching effects of electrical field stimulation. By examining these data in the context of multiple hypotheses of DBS action, generally developed through clinical and physiological observations, we define a multitude of consistencies and inconsistencies in the developing literature of this rapidly moving field.
Younce JR, Albaugh DL, Shih YY
Deep brain stimulation with simultaneous FMRI in rodentsJournal of Visualized Experiments[Press release]PubMed
@article{JR2014,
title = {Deep brain stimulation with simultaneous FMRI in rodents},
author = {Younce JR, Albaugh DL, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/24561922/},
doi = {10.3791/51271},
year = {2014},
date = {2014-02-15},
urldate = {2014-02-15},
journal = {Journal of Visualized Experiments},
volume = {15},
number = {84},
pages = {e51271},
abstract = {In order to visualize the global and downstream neuronal responses to deep brain stimulation (DBS) at various targets, we have developed a protocol for using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) to image rodents with simultaneous DBS. DBS fMRI presents a number of technical challenges, including accuracy of electrode implantation, MR artifacts created by the electrode, choice of anesthesia and paralytic to minimize any neuronal effects while simultaneously eliminating animal motion, and maintenance of physiological parameters, deviation from which can confound the BOLD signal. Our laboratory has developed a set of procedures that are capable of overcoming most of these possible issues. For electrical stimulation, a homemade tungsten bipolar microelectrode is used, inserted stereotactically at the stimulation site in the anesthetized subject. In preparation for imaging, rodents are fixed on a plastic headpiece and transferred to the magnet bore. For sedation and paralysis during scanning, a cocktail of dexmedetomidine and pancuronium is continuously infused, along with a minimal dose of isoflurane; this preparation minimizes the BOLD ceiling effect of volatile anesthetics. In this example experiment, stimulation of the subthalamic nucleus (STN) produces BOLD responses which are observed primarily in ipsilateral cortical regions, centered in motor cortex. Simultaneous DBS and fMRI allows the unambiguous modulation of neural circuits dependent on stimulation location and stimulation parameters, and permits observation of neuronal modulations free of regional bias. This technique may be used to explore the downstream effects of modulating neural circuitry at nearly any brain region, with implications for both experimental and clinical DBS.},
note = {invited method paper},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In order to visualize the global and downstream neuronal responses to deep brain stimulation (DBS) at various targets, we have developed a protocol for using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) to image rodents with simultaneous DBS. DBS fMRI presents a number of technical challenges, including accuracy of electrode implantation, MR artifacts created by the electrode, choice of anesthesia and paralytic to minimize any neuronal effects while simultaneously eliminating animal motion, and maintenance of physiological parameters, deviation from which can confound the BOLD signal. Our laboratory has developed a set of procedures that are capable of overcoming most of these possible issues. For electrical stimulation, a homemade tungsten bipolar microelectrode is used, inserted stereotactically at the stimulation site in the anesthetized subject. In preparation for imaging, rodents are fixed on a plastic headpiece and transferred to the magnet bore. For sedation and paralysis during scanning, a cocktail of dexmedetomidine and pancuronium is continuously infused, along with a minimal dose of isoflurane; this preparation minimizes the BOLD ceiling effect of volatile anesthetics. In this example experiment, stimulation of the subthalamic nucleus (STN) produces BOLD responses which are observed primarily in ipsilateral cortical regions, centered in motor cortex. Simultaneous DBS and fMRI allows the unambiguous modulation of neural circuits dependent on stimulation location and stimulation parameters, and permits observation of neuronal modulations free of regional bias. This technique may be used to explore the downstream effects of modulating neural circuitry at nearly any brain region, with implications for both experimental and clinical DBS.
Lai HY, Younce JR, Albaugh DL, Kao YC, Shih YY
Functional MRI reveals frequency-dependent responses during deep brain stimulation at the subthalamic nucleus or internal globus pallidus@article{HY2014b,
title = {Functional MRI reveals frequency-dependent responses during deep brain stimulation at the subthalamic nucleus or internal globus pallidus},
author = {Lai HY, Younce JR, Albaugh DL, Kao YC, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/23988274/},
doi = {10.1016/j.neuroimage.2013.08.026},
year = {2014},
date = {2014-01-01},
journal = {NeuroImage},
volume = {84},
number = {1},
pages = {11-18},
abstract = {Deep brain stimulation (DBS) represents a widely used therapeutic tool for the symptomatic treatment of movement disorders, most commonly Parkinson's disease (PD). High frequency stimulation at both the subthalamic nucleus (STN) and internal globus pallidus (GPi) has been used with great success for the symptomatic treatment of PD, although the therapeutic mechanisms of action remain elusive. To better understand how DBS at these target sites modulates neural circuitry, the present study used functional blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to map global brain responses to DBS at the STN and GPi of the rat. Robust activation centered in the ipsilateral motor cortex was observed during high frequency stimulation at either target site, with peak responses observed at a stimulation frequency of 100 Hz. Of note, frequency tuning curves were generated, demonstrating that cortical activation was maximal at clinically-relevant stimulation frequencies. Divergent responses to stimulation were noted in the contralateral hemisphere, with strong cortical and striatal negative BOLD signal during stimulation of the GPi, but not STN. The frequency-dependence of the observed motor cortex activation at both targets suggests a relationship with the therapeutic effects of STN and GPi DBS, with both DBS targets being functionally connected with motor cortex at therapeutic stimulation frequencies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Deep brain stimulation (DBS) represents a widely used therapeutic tool for the symptomatic treatment of movement disorders, most commonly Parkinson's disease (PD). High frequency stimulation at both the subthalamic nucleus (STN) and internal globus pallidus (GPi) has been used with great success for the symptomatic treatment of PD, although the therapeutic mechanisms of action remain elusive. To better understand how DBS at these target sites modulates neural circuitry, the present study used functional blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to map global brain responses to DBS at the STN and GPi of the rat. Robust activation centered in the ipsilateral motor cortex was observed during high frequency stimulation at either target site, with peak responses observed at a stimulation frequency of 100 Hz. Of note, frequency tuning curves were generated, demonstrating that cortical activation was maximal at clinically-relevant stimulation frequencies. Divergent responses to stimulation were noted in the contralateral hemisphere, with strong cortical and striatal negative BOLD signal during stimulation of the GPi, but not STN. The frequency-dependence of the observed motor cortex activation at both targets suggests a relationship with the therapeutic effects of STN and GPi DBS, with both DBS targets being functionally connected with motor cortex at therapeutic stimulation frequencies.
2013
Lin AL, Zheng W, Halloran JJ, Burbank RR, Hussong SA, Hart MJ, Javors M, Shih YY, Muir E, Fonseca, RS, Strong R, Richardson AG, Lechleiter JD, Fox PT, Galvan V
Chronic rapamycin restores brain vascular integrity and function through NO synthase activation and improves memory in symptomatic mice modeling Alzheimer’s diseaseJournal of Cerebral Blood Flow and MetabolismPubMed
@article{AL2013,
title = {Chronic rapamycin restores brain vascular integrity and function through NO synthase activation and improves memory in symptomatic mice modeling Alzheimer’s disease},
author = {Lin AL, Zheng W, Halloran JJ, Burbank RR, Hussong SA, Hart MJ, Javors M, Shih YY, Muir E, Fonseca, RS, Strong R, Richardson AG, Lechleiter JD, Fox PT, Galvan V},
url = {https://pubmed.ncbi.nlm.nih.gov/23801246/},
doi = {10.1038/jcbfm.2013.82},
year = {2013},
date = {2013-09-01},
urldate = {2013-09-01},
journal = {Journal of Cerebral Blood Flow and Metabolism},
volume = {33},
number = {9},
pages = {1412-21},
abstract = {Vascular pathology is a major feature of Alzheimer's disease (AD) and other dementias. We recently showed that chronic administration of the target-of-rapamycin (TOR) inhibitor rapamycin, which extends lifespan and delays aging, halts the progression of AD-like disease in transgenic human (h)APP mice modeling AD when administered before disease onset. Here we demonstrate that chronic reduction of TOR activity by rapamycin treatment started after disease onset restored cerebral blood flow (CBF) and brain vascular density, reduced cerebral amyloid angiopathy and microhemorrhages, decreased amyloid burden, and improved cognitive function in symptomatic hAPP (AD) mice. Like acetylcholine (ACh), a potent vasodilator, acute rapamycin treatment induced the phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and NO release in brain endothelium. Administration of the NOS inhibitor L-NG-Nitroarginine methyl ester reversed vasodilation as well as the protective effects of rapamycin on CBF and vasculature integrity, indicating that rapamycin preserves vascular density and CBF in AD mouse brains through NOS activation. Taken together, our data suggest that chronic reduction of TOR activity by rapamycin blocked the progression of AD-like cognitive and histopathological deficits by preserving brain vascular integrity and function. Drugs that inhibit the TOR pathway may have promise as a therapy for AD and possibly for vascular dementias.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Vascular pathology is a major feature of Alzheimer's disease (AD) and other dementias. We recently showed that chronic administration of the target-of-rapamycin (TOR) inhibitor rapamycin, which extends lifespan and delays aging, halts the progression of AD-like disease in transgenic human (h)APP mice modeling AD when administered before disease onset. Here we demonstrate that chronic reduction of TOR activity by rapamycin treatment started after disease onset restored cerebral blood flow (CBF) and brain vascular density, reduced cerebral amyloid angiopathy and microhemorrhages, decreased amyloid burden, and improved cognitive function in symptomatic hAPP (AD) mice. Like acetylcholine (ACh), a potent vasodilator, acute rapamycin treatment induced the phosphorylation of endothelial nitric oxide (NO) synthase (eNOS) and NO release in brain endothelium. Administration of the NOS inhibitor L-NG-Nitroarginine methyl ester reversed vasodilation as well as the protective effects of rapamycin on CBF and vasculature integrity, indicating that rapamycin preserves vascular density and CBF in AD mouse brains through NOS activation. Taken together, our data suggest that chronic reduction of TOR activity by rapamycin blocked the progression of AD-like cognitive and histopathological deficits by preserving brain vascular integrity and function. Drugs that inhibit the TOR pathway may have promise as a therapy for AD and possibly for vascular dementias.
Li G, Shih YY, Kiel JW, De La Garza BH, Du F, Duong TQ
MRI study of cerebral, retinal and choroidal blood flow responses to acute hypertensionExperimental Eye ResearchPubMed
@article{G2013,
title = {MRI study of cerebral, retinal and choroidal blood flow responses to acute hypertension},
author = {Li G, Shih YY, Kiel JW, De La Garza BH, Du F, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/23623996/},
doi = {10.1016/j.exer.2013.04.003},
year = {2013},
date = {2013-07-01},
urldate = {2013-07-01},
journal = {Experimental Eye Research},
volume = {112},
pages = {118-24},
abstract = {Blood flow (BF) in many tissues is stable during significant fluctuations in systemic arterial blood pressure or perfusion pressure under normal conditions. The regulatory mechanisms responsible for this non-passive BF behavior include both local and neural control mechanisms. This study evaluated cerebral BF (CBF), retinal BF (RBF) and choroidal BF (ChBF) responses to acute blood pressure increases in rats using magnetic resonance imaging (MRI). A transient increase in blood pressure inside the MRI scanner was achieved by mechanically inflating a balloon catheter to occlude the descending aorta near the diaphragm. We verified the rat model of mechanical occlusion and MRI approach by first measuring blood-flow regulatory responses to changing BP in the brain under normoxia and hypercapnia where the phenomenon is well documented. Retinal and choroidal blood-flow responses to transient increased arterial pressure were then investigated. In response to an acute increase in blood pressure, RBF exhibited autoregulatory behavior and ChBF exhibited baroregulation similar to that seen in the cerebral circulation. This approach may prove useful to investigate retinal and choroidal vascular dysregulation in rat models of retinal diseases with suspected vascular etiology.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Blood flow (BF) in many tissues is stable during significant fluctuations in systemic arterial blood pressure or perfusion pressure under normal conditions. The regulatory mechanisms responsible for this non-passive BF behavior include both local and neural control mechanisms. This study evaluated cerebral BF (CBF), retinal BF (RBF) and choroidal BF (ChBF) responses to acute blood pressure increases in rats using magnetic resonance imaging (MRI). A transient increase in blood pressure inside the MRI scanner was achieved by mechanically inflating a balloon catheter to occlude the descending aorta near the diaphragm. We verified the rat model of mechanical occlusion and MRI approach by first measuring blood-flow regulatory responses to changing BP in the brain under normoxia and hypercapnia where the phenomenon is well documented. Retinal and choroidal blood-flow responses to transient increased arterial pressure were then investigated. In response to an acute increase in blood pressure, RBF exhibited autoregulatory behavior and ChBF exhibited baroregulation similar to that seen in the cerebral circulation. This approach may prove useful to investigate retinal and choroidal vascular dysregulation in rat models of retinal diseases with suspected vascular etiology.
Shih YY, Chen YY, Lai HY, Kao YC, Shyu BC, Duong TQ
Ultra high-resolution fMRI and electrophysiology of the rat primary somatosensory cortex@article{YY2013,
title = {Ultra high-resolution fMRI and electrophysiology of the rat primary somatosensory cortex},
author = {Shih YY, Chen YY, Lai HY, Kao YC, Shyu BC, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/23384528/},
doi = {10.1016/j.neuroimage.2013.01.062},
year = {2013},
date = {2013-06-01},
journal = {NeuroImage},
volume = {73},
pages = {113-120},
abstract = {High-resolution functional-magnetic-resonance-imaging (fMRI) has been used to study brain functions at increasingly finer scale, but whether fMRI can accurately reflect layer-specific neuronal activities is less well understood. The present study investigated layer-specific cerebral-blood-volume (CBV) fMRI and electrophysiological responses in the rat cortex. CBV fMRI at 40×40 μm in-plane resolution was performed on an 11.7-T scanner. Electrophysiology used a 32-channel electrode array that spanned the entire cortical depth. Graded electrical stimulation was used to study activations in different cortical layers, exploiting the notion that most of the sensory-specific neurons are in layers II-V and most of the nociceptive-specific neurons are in layers V-VI. CBV response was strongest in layer IV of all stimulus amplitudes. Current source density analysis showed strong sink currents at cortical layers IV and VI. Multi-unit activities mainly appeared at layers IV-VI and peaked at layer V. Although our measures showed scaled activation profiles during modulation of stimulus amplitude and failed to detect specific recruitment at layers V and VI during noxious electrical stimuli, there appears to be discordance between CBV fMRI and electrophysiological peak responses, suggesting neurovascular uncoupling at laminar resolution. The technique implemented in the present study offers a means to investigate intracortical neurovascular function in the normal and diseased animal models at laminar resolution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
High-resolution functional-magnetic-resonance-imaging (fMRI) has been used to study brain functions at increasingly finer scale, but whether fMRI can accurately reflect layer-specific neuronal activities is less well understood. The present study investigated layer-specific cerebral-blood-volume (CBV) fMRI and electrophysiological responses in the rat cortex. CBV fMRI at 40×40 μm in-plane resolution was performed on an 11.7-T scanner. Electrophysiology used a 32-channel electrode array that spanned the entire cortical depth. Graded electrical stimulation was used to study activations in different cortical layers, exploiting the notion that most of the sensory-specific neurons are in layers II-V and most of the nociceptive-specific neurons are in layers V-VI. CBV response was strongest in layer IV of all stimulus amplitudes. Current source density analysis showed strong sink currents at cortical layers IV and VI. Multi-unit activities mainly appeared at layers IV-VI and peaked at layer V. Although our measures showed scaled activation profiles during modulation of stimulus amplitude and failed to detect specific recruitment at layers V and VI during noxious electrical stimuli, there appears to be discordance between CBV fMRI and electrophysiological peak responses, suggesting neurovascular uncoupling at laminar resolution. The technique implemented in the present study offers a means to investigate intracortical neurovascular function in the normal and diseased animal models at laminar resolution.
Huang S, Du F, Shih YY, Shen Q, Gonzalez-Lima F,; Duong TQ
Methylene blue potentiates stimulus-evoked fMRI responses and cerebral oxygen consumption during normoxia and hypoxia@article{S2013,
title = {Methylene blue potentiates stimulus-evoked fMRI responses and cerebral oxygen consumption during normoxia and hypoxia},
author = {Huang S, Du F, Shih YY, Shen Q, Gonzalez-Lima F, and Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/23357077/},
doi = {10.1016/j.neuroimage.2013.01.027},
year = {2013},
date = {2013-05-15},
urldate = {2013-05-15},
journal = {NeuroImage},
volume = {72},
pages = {237-242},
abstract = {Methylene blue USP (MB) at low doses has metabolic-enhancing and antioxidant properties and exhibits experimental neurotherapeutic benefits, but little is known about its in vivo effects on cerebral blood flow (CBF), functional evoked responses, and the associated changes in cerebral metabolic rate of oxygen (CMRO2). This study used magnetic resonance imaging (MRI) to evaluate the in vivo effects of a single intravenous MB therapeutic dose (0.5mg/kg) on basal CBF, blood oxygenation level-dependent (BOLD) and CBF responses to hypercapnic (5% CO2 in air) inhalation, as well as changes in BOLD, CBF, and CMRO2 during forepaw stimulation in the rat brain. MB did not have significant effects on arterial oxygen saturation, heart rate and fMRI responses to hypercapnia. However, MB significantly potentiated forepaw-evoked BOLD and CBF changes under normoxia. To further evaluate in vivo effects of MB under metabolic stress conditions, MRI measurements were also made under mild hypoxia (15% O2). Hypoxia per se increased evoked functional MRI responses. MB under hypoxia further potentiated forepaw-evoked BOLD, CBF and oxygen consumption responses relative to normoxia. These findings provide insights into MB's effects on cerebral hemodynamics in vivo and could help to optimize treatments in neurological diseases with mitochondrial dysfunction and oxidative stress.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Methylene blue USP (MB) at low doses has metabolic-enhancing and antioxidant properties and exhibits experimental neurotherapeutic benefits, but little is known about its in vivo effects on cerebral blood flow (CBF), functional evoked responses, and the associated changes in cerebral metabolic rate of oxygen (CMRO2). This study used magnetic resonance imaging (MRI) to evaluate the in vivo effects of a single intravenous MB therapeutic dose (0.5mg/kg) on basal CBF, blood oxygenation level-dependent (BOLD) and CBF responses to hypercapnic (5% CO2 in air) inhalation, as well as changes in BOLD, CBF, and CMRO2 during forepaw stimulation in the rat brain. MB did not have significant effects on arterial oxygen saturation, heart rate and fMRI responses to hypercapnia. However, MB significantly potentiated forepaw-evoked BOLD and CBF changes under normoxia. To further evaluate in vivo effects of MB under metabolic stress conditions, MRI measurements were also made under mild hypoxia (15% O2). Hypoxia per se increased evoked functional MRI responses. MB under hypoxia further potentiated forepaw-evoked BOLD, CBF and oxygen consumption responses relative to normoxia. These findings provide insights into MB's effects on cerebral hemodynamics in vivo and could help to optimize treatments in neurological diseases with mitochondrial dysfunction and oxidative stress.
Shih YY, Wang L, De La Garza BH, Grant C, Li G, Kiel JW,; Duong TQ
Quantitative retinal and choroidal blood flow during light, dark adaptation, and flicker light stimulation in rats using fluorescent microspheres@article{YY2013b,
title = {Quantitative retinal and choroidal blood flow during light, dark adaptation, and flicker light stimulation in rats using fluorescent microspheres},
author = {Shih YY, Wang L, De La Garza BH, Grant C, Li G, Kiel JW, and Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/23317112/},
doi = {10.3109/02713683.2012.756526},
year = {2013},
date = {2013-01-14},
urldate = {2013-01-14},
journal = {Current Eye Research},
volume = {38},
number = {2},
pages = {292-8},
abstract = {Purpose: The present study aimed to quantify retinal and choroidal blood flow (BF) during light, dark adaptation and flicker light stimulation using the microsphere technique.
Materials and Methods: Adult male Sprague–Dawley rats were anesthetized with isoflurane. Eyes were dark (Group I, n = 8), light (Group II, n = 8) adapted or stimulated with 10 Hz flicker light (Group III, n = 10). Retinal and choroidal BF were measured by a previously established method, using a mixture of 8 µm yellow-green and 10 µm red fluorescent microspheres. The microspheres were counted ex vivo in the dissected retina and choroid and in the reference arterial blood under a fluorescent microscope.
Results: The choroidal BF was 64.8 ± 29 µl/min (mean ± SD) during dark adaptation, not significantly different from that during light adaptation (66.0 ± 17.8 µl/min). The retinal BF was 13.5 ± 3.2 µl/min during 10 Hz flickering light stimulation, significantly higher than that during dark adaptation in the control fellow eyes (9.9 ± 2.9 µl/min). The choroidal BF values were not statistically different between flicker stimulation and dark adaptation. Retinal BF was 11.6 ± 2.9 µl/min during light adaptation. Dark adaptation did not increase retinal BF (Group I, 8.2 ± 2.4 µl/min; Group II, 9.9 ± 2.9 µl/min).
Conclusions: These findings argue against a dark-induced or flicker-induced functional hyperemia in the choroid as a result of the demands of the outer retina. Retinal BF was not higher during dark adaptation. Our data support the conclusion that the inner retina has a higher energy demand in flicker conditions relative to dark.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Purpose: The present study aimed to quantify retinal and choroidal blood flow (BF) during light, dark adaptation and flicker light stimulation using the microsphere technique.
Materials and Methods: Adult male Sprague–Dawley rats were anesthetized with isoflurane. Eyes were dark (Group I, n = 8), light (Group II, n = 8) adapted or stimulated with 10 Hz flicker light (Group III, n = 10). Retinal and choroidal BF were measured by a previously established method, using a mixture of 8 µm yellow-green and 10 µm red fluorescent microspheres. The microspheres were counted ex vivo in the dissected retina and choroid and in the reference arterial blood under a fluorescent microscope.
Results: The choroidal BF was 64.8 ± 29 µl/min (mean ± SD) during dark adaptation, not significantly different from that during light adaptation (66.0 ± 17.8 µl/min). The retinal BF was 13.5 ± 3.2 µl/min during 10 Hz flickering light stimulation, significantly higher than that during dark adaptation in the control fellow eyes (9.9 ± 2.9 µl/min). The choroidal BF values were not statistically different between flicker stimulation and dark adaptation. Retinal BF was 11.6 ± 2.9 µl/min during light adaptation. Dark adaptation did not increase retinal BF (Group I, 8.2 ± 2.4 µl/min; Group II, 9.9 ± 2.9 µl/min).
Conclusions: These findings argue against a dark-induced or flicker-induced functional hyperemia in the choroid as a result of the demands of the outer retina. Retinal BF was not higher during dark adaptation. Our data support the conclusion that the inner retina has a higher energy demand in flicker conditions relative to dark.
Materials and Methods: Adult male Sprague–Dawley rats were anesthetized with isoflurane. Eyes were dark (Group I, n = 8), light (Group II, n = 8) adapted or stimulated with 10 Hz flicker light (Group III, n = 10). Retinal and choroidal BF were measured by a previously established method, using a mixture of 8 µm yellow-green and 10 µm red fluorescent microspheres. The microspheres were counted ex vivo in the dissected retina and choroid and in the reference arterial blood under a fluorescent microscope.
Results: The choroidal BF was 64.8 ± 29 µl/min (mean ± SD) during dark adaptation, not significantly different from that during light adaptation (66.0 ± 17.8 µl/min). The retinal BF was 13.5 ± 3.2 µl/min during 10 Hz flickering light stimulation, significantly higher than that during dark adaptation in the control fellow eyes (9.9 ± 2.9 µl/min). The choroidal BF values were not statistically different between flicker stimulation and dark adaptation. Retinal BF was 11.6 ± 2.9 µl/min during light adaptation. Dark adaptation did not increase retinal BF (Group I, 8.2 ± 2.4 µl/min; Group II, 9.9 ± 2.9 µl/min).
Conclusions: These findings argue against a dark-induced or flicker-induced functional hyperemia in the choroid as a result of the demands of the outer retina. Retinal BF was not higher during dark adaptation. Our data support the conclusion that the inner retina has a higher energy demand in flicker conditions relative to dark.
Chen CCV, Shih YY, Chang C
Dopaminergic imaging of non-motor manifestation in Parkinson disease by fMRI@article{CC2013,
title = {Dopaminergic imaging of non-motor manifestation in Parkinson disease by fMRI},
author = {Chen CCV, Shih YY, Chang C},
url = {https://pubmed.ncbi.nlm.nih.gov/22842018/},
doi = {10.1016/j.nbd.2012.07.020},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
journal = {Neurobiology of Disease},
volume = {49},
pages = {99-106},
abstract = {Nonmotor manifestations determine the life quality of patients with Parkinson's disease (PD). Identification of the nonmotor symptoms in PD as definite changes will represent a milestone in its diagnosis. Outcome measures that characterize nonmotor manifestations with specificity for dopaminergic deficiency are essential to that goal. Pain is a prevalent sensory disturbance in PD patients. The prevalence was reported to be up to 83%. Nociceptive stimuli under normal conditions elicit decreases in cerebral blood volume (CBV) in the striatum via dopaminergic neurotransmission. This nociception-induced CBV response is potentially to be defined as a characteristic of the pain symptom of PD. To validate this concept, steady-state CBV-weighted functional magnetic resonance imaging with iron oxide nanoparticles was employed to measure CBV changes in parkinsonian rats. Tyrosine hydroxylase immunohistology was used to identify the dopaminergic integrity to corroborate the imaging findings. Additional experiments that tested pain responses in parkinsonism were also carried out. The results revealed that the lesioned striatum exhibited a weakened CBV decrease in response to the nociceptive stimulus. This weakened CBV response occurred mainly in areas with dopaminergic denervation. A strong correspondence was observed between the distributions of the nociception-induced CBV responses and dopaminergic innervation. The persisting CBV signals in the striatum were abolished by the D2/D3 antagonist eticlopride. The findings of these behavioral, neuroimaging, immunohistological, and pharmacological experiments demonstrate that pain in a rat model of PD can be characterized by nociception induced striatal CBV signal changes with specificity for dopaminergic dysfunction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nonmotor manifestations determine the life quality of patients with Parkinson's disease (PD). Identification of the nonmotor symptoms in PD as definite changes will represent a milestone in its diagnosis. Outcome measures that characterize nonmotor manifestations with specificity for dopaminergic deficiency are essential to that goal. Pain is a prevalent sensory disturbance in PD patients. The prevalence was reported to be up to 83%. Nociceptive stimuli under normal conditions elicit decreases in cerebral blood volume (CBV) in the striatum via dopaminergic neurotransmission. This nociception-induced CBV response is potentially to be defined as a characteristic of the pain symptom of PD. To validate this concept, steady-state CBV-weighted functional magnetic resonance imaging with iron oxide nanoparticles was employed to measure CBV changes in parkinsonian rats. Tyrosine hydroxylase immunohistology was used to identify the dopaminergic integrity to corroborate the imaging findings. Additional experiments that tested pain responses in parkinsonism were also carried out. The results revealed that the lesioned striatum exhibited a weakened CBV decrease in response to the nociceptive stimulus. This weakened CBV response occurred mainly in areas with dopaminergic denervation. A strong correspondence was observed between the distributions of the nociception-induced CBV responses and dopaminergic innervation. The persisting CBV signals in the striatum were abolished by the D2/D3 antagonist eticlopride. The findings of these behavioral, neuroimaging, immunohistological, and pharmacological experiments demonstrate that pain in a rat model of PD can be characterized by nociception induced striatal CBV signal changes with specificity for dopaminergic dysfunction.
2012
Shih YY, Li G, Muir ER, De La Garza BH, Kiel JW, Duong TQ
Pharmacological MRI of the retina: blood flow and BOLD responses during nitroprusside infusionMagnetic Resonance in MedicinePubMed
@article{YY2012,
title = {Pharmacological MRI of the retina: blood flow and BOLD responses during nitroprusside infusion},
author = {Shih YY, Li G, Muir ER, De La Garza BH, Kiel JW, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22183830/},
doi = {10.1002/mrm.24112},
year = {2012},
date = {2012-10-01},
urldate = {2012-10-01},
journal = {Magnetic Resonance in Medicine},
volume = {68},
number = {4},
pages = {1273-8},
abstract = {Nitroprusside, a vasodilatory nitric oxide donor, is clinically used during vascular surgery and to lower blood pressure in acute hypertension. This article reports a novel application of blood flow (BF) and blood oxygenation level dependent (BOLD) MRI on an 11.7T scanner to image the rat chorioretinal BF and BOLD changes associated with graded nitroprusside infusion. At low doses (1 or 2 μg/kg/min), nitroprusside increased BF as expected but decreased BOLD signals, showing an intriguing BF-BOLD uncoupling. At high doses (3-5 μg/kg/min), nitroprusside decreased BF and markedly decreased BOLD signals. To our knowledge, this is the first pharmacological MRI application of the retina. This approach has potential to open up new avenues to study the drug-related hemodynamic functions and to evaluate the effects of novel therapeutic interventions on BOLD and BF in the normal and diseased retinas.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nitroprusside, a vasodilatory nitric oxide donor, is clinically used during vascular surgery and to lower blood pressure in acute hypertension. This article reports a novel application of blood flow (BF) and blood oxygenation level dependent (BOLD) MRI on an 11.7T scanner to image the rat chorioretinal BF and BOLD changes associated with graded nitroprusside infusion. At low doses (1 or 2 μg/kg/min), nitroprusside increased BF as expected but decreased BOLD signals, showing an intriguing BF-BOLD uncoupling. At high doses (3-5 μg/kg/min), nitroprusside decreased BF and markedly decreased BOLD signals. To our knowledge, this is the first pharmacological MRI application of the retina. This approach has potential to open up new avenues to study the drug-related hemodynamic functions and to evaluate the effects of novel therapeutic interventions on BOLD and BF in the normal and diseased retinas.
Li G, De La Garza BH, Shih YY, Muir ER, Duong TQ
Layer-specific blood-flow MRI of retinitis pigmentosa in RCS ratsExperimental Eye ResearchPubMed
@article{G2012,
title = {Layer-specific blood-flow MRI of retinitis pigmentosa in RCS rats},
author = {Li G, De La Garza BH, Shih YY, Muir ER, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22721720/},
doi = {10.1016/j.exer.2012.06.006},
year = {2012},
date = {2012-08-01},
urldate = {2012-08-01},
journal = {Experimental Eye Research},
volume = {101},
pages = {90-6},
abstract = {The Royal College of Surgeons (RCS) rat is an established animal model of retinitis pigmentosa, a family of inherited retinal diseases which starts with loss of peripheral vision and progresses to eventual blindness. Blood flow (BF), an important physiological parameter, is intricately coupled to metabolic function under normal physiological conditions and is perturbed in many neurological and retinal diseases. This study reports non-invasive high-resolution MRI (44 × 44 × 600 μm) to image quantitative retinal and choroidal BF and layer-specific retinal thicknesses in RCS rat retinas at different stages of retinal degeneration compared with age-matched controls. The unique ability to separate retinal and choroidal BF was made possible by the depth-resolved MRI technique. RBF decreased with progressive retinal degeneration, but ChBF did not change in RCS rats up to post-natal day 90. We concluded that choroidal and retinal circulations have different susceptibility to progressive retinal degeneration in RCS rats. Layer-specific retinal thickness became progressively thinner and was corroborated by histological analysis in the same animals. MRI can detect progressive anatomical and BF changes during retinal degeneration with laminar resolution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The Royal College of Surgeons (RCS) rat is an established animal model of retinitis pigmentosa, a family of inherited retinal diseases which starts with loss of peripheral vision and progresses to eventual blindness. Blood flow (BF), an important physiological parameter, is intricately coupled to metabolic function under normal physiological conditions and is perturbed in many neurological and retinal diseases. This study reports non-invasive high-resolution MRI (44 × 44 × 600 μm) to image quantitative retinal and choroidal BF and layer-specific retinal thicknesses in RCS rat retinas at different stages of retinal degeneration compared with age-matched controls. The unique ability to separate retinal and choroidal BF was made possible by the depth-resolved MRI technique. RBF decreased with progressive retinal degeneration, but ChBF did not change in RCS rats up to post-natal day 90. We concluded that choroidal and retinal circulations have different susceptibility to progressive retinal degeneration in RCS rats. Layer-specific retinal thickness became progressively thinner and was corroborated by histological analysis in the same animals. MRI can detect progressive anatomical and BF changes during retinal degeneration with laminar resolution.
De La Garza BH, Li G, Shih YY, Duong TQ
Layer-specific manganese-enhanced MRI of the retina in light and dark adaptationInvestigative Ophthalmology & Visual SciencePubMed
@article{BH2012b,
title = {Layer-specific manganese-enhanced MRI of the retina in light and dark adaptation},
author = {De La Garza BH, Li G, Shih YY, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22669725/},
doi = {10.1167/iovs.11-8826},
year = {2012},
date = {2012-07-03},
urldate = {2012-07-03},
journal = {Investigative Ophthalmology & Visual Science},
volume = {53},
number = {8},
pages = {4352-8},
abstract = {Purpose.
To employ functional manganese-enhanced MRI (MEMRI) to image layer-specific changes in calcium-dependent activities in the rat retina during light versus dark adaptation.
Methods.
Functional MEMRI at 20 × 20 × 700 μm was used to study light and dark adaptation in the same animals (N = 10) in which one eye was covered and the fellow eye was not. The activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. T1-weighted MRI at 11.7 tesla (T) was performed using two identical radiofrequency transceiver coils to allow interleaved MRI acquisitions of the two eyes. An intravascular contrast agent was also used to verify layer assignments.
Results.
MEMRI detected contrasts among the inner retina, outer retina, and choroid. Independent confirmation of the vascular layers and boundaries between layers was documented with an intravascular contrast agent. The retinal layer thicknesses agreed with published data. The outer retina had lower MEMRI activity in light compared with dark adaption (P < 0.001), consistent with the increased metabolic demand associated with the “dark current.” The inner retina had higher MEMRI activity in light compared with dark adaption (P < 0.05). The choroid MEMRI activity was not statistically different between light and dark adaptation (P > 0.05).
Conclusions.
This study demonstrated a high-resolution MEMRI protocol to image functional activities among different layers of the retinas in awake animals during light and dark adaptation. This approach could have potential applications in animal models of retinal dysfunction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Purpose.
To employ functional manganese-enhanced MRI (MEMRI) to image layer-specific changes in calcium-dependent activities in the rat retina during light versus dark adaptation.
Methods.
Functional MEMRI at 20 × 20 × 700 μm was used to study light and dark adaptation in the same animals (N = 10) in which one eye was covered and the fellow eye was not. The activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. T1-weighted MRI at 11.7 tesla (T) was performed using two identical radiofrequency transceiver coils to allow interleaved MRI acquisitions of the two eyes. An intravascular contrast agent was also used to verify layer assignments.
Results.
MEMRI detected contrasts among the inner retina, outer retina, and choroid. Independent confirmation of the vascular layers and boundaries between layers was documented with an intravascular contrast agent. The retinal layer thicknesses agreed with published data. The outer retina had lower MEMRI activity in light compared with dark adaption (P < 0.001), consistent with the increased metabolic demand associated with the “dark current.” The inner retina had higher MEMRI activity in light compared with dark adaption (P < 0.05). The choroid MEMRI activity was not statistically different between light and dark adaptation (P > 0.05).
Conclusions.
This study demonstrated a high-resolution MEMRI protocol to image functional activities among different layers of the retinas in awake animals during light and dark adaptation. This approach could have potential applications in animal models of retinal dysfunction.
To employ functional manganese-enhanced MRI (MEMRI) to image layer-specific changes in calcium-dependent activities in the rat retina during light versus dark adaptation.
Methods.
Functional MEMRI at 20 × 20 × 700 μm was used to study light and dark adaptation in the same animals (N = 10) in which one eye was covered and the fellow eye was not. The activity encoding of the light and dark adaptation was achieved in awake conditions and imaged under anesthesia. T1-weighted MRI at 11.7 tesla (T) was performed using two identical radiofrequency transceiver coils to allow interleaved MRI acquisitions of the two eyes. An intravascular contrast agent was also used to verify layer assignments.
Results.
MEMRI detected contrasts among the inner retina, outer retina, and choroid. Independent confirmation of the vascular layers and boundaries between layers was documented with an intravascular contrast agent. The retinal layer thicknesses agreed with published data. The outer retina had lower MEMRI activity in light compared with dark adaption (P < 0.001), consistent with the increased metabolic demand associated with the “dark current.” The inner retina had higher MEMRI activity in light compared with dark adaption (P < 0.05). The choroid MEMRI activity was not statistically different between light and dark adaptation (P > 0.05).
Conclusions.
This study demonstrated a high-resolution MEMRI protocol to image functional activities among different layers of the retinas in awake animals during light and dark adaptation. This approach could have potential applications in animal models of retinal dysfunction.
Shih YY, Muir ER, Li G, De La Garza BH, Duong TQ
High resolution 3D microangiography of the rat ocular circulation@article{YY2012b,
title = {High resolution 3D microangiography of the rat ocular circulation},
author = {Shih YY, Muir ER, Li G, De La Garza BH, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22523323/},
doi = {10.1148/radiol.12112033},
year = {2012},
date = {2012-07-01},
journal = {Radiology},
volume = {264},
number = {1},
pages = {234-241},
abstract = {Purpose
To develop high-spatial-resolution magnetic resonance (MR) microangiography techniques to image the rat ocular circulation.
Materials and Methods
Animal experiments were performed with institutional Animal Care Committee approval. MR microangiography (resolution, 84 × 84 × 84 μm or 42 × 42 × 84 μm) of the rat eye (eight rats) was performed by using a custom-made small circular surface coil with an 11.7-T MR unit before and after monocrystalline iron oxide nanoparticle (MION) injection. MR microangiography measurements were made during air, oxygen, and carbogen inhalation. From three-dimensional MR microangiography, the retina was virtually flattened to enable en face views of various retinal depths, including the retinal and choroidal vascular layers. Signal intensity changes within the retinal or choroidal arteries and veins associated with gas challenges were analyzed. Statistical analysis was performed by using paired t tests, with P < .05 considered to indicate a significant difference. Bonferroni correction was used to adjust for multiple comparisons.
Results
The central retinal artery, long posterior ciliary arteries, and choroidal vasculature could be distinguished on MR microangiograms of the eye. With MR microangiography, retinal arteries and veins could be distinguished on the basis of blood oxygen level–dependent contrast. Carbogen inhalation–enhanced MR microangiography signal intensity in both the retina (P = .001) and choroid (P = .027) compared with oxygen inhalation. Carbogen inhalation showed significantly higher signal intensity changes in the retinal arteries (P = .001, compared with oxygen inhalation), but not in the veins (P = .549). With MION administration, MR microangiography depicted retinal arterial vasoconstriction when the animals were breathing oxygen (P = .02, compared with animals breathing air).
Conclusion
MR microangiography of the eye allows depth-resolved imaging of small angiographic details of the ocular circulation. This approach may prove useful in studying microvascular pathologic findings and neurovascular dysfunction in the eye and retina.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Purpose
To develop high-spatial-resolution magnetic resonance (MR) microangiography techniques to image the rat ocular circulation.
Materials and Methods
Animal experiments were performed with institutional Animal Care Committee approval. MR microangiography (resolution, 84 × 84 × 84 μm or 42 × 42 × 84 μm) of the rat eye (eight rats) was performed by using a custom-made small circular surface coil with an 11.7-T MR unit before and after monocrystalline iron oxide nanoparticle (MION) injection. MR microangiography measurements were made during air, oxygen, and carbogen inhalation. From three-dimensional MR microangiography, the retina was virtually flattened to enable en face views of various retinal depths, including the retinal and choroidal vascular layers. Signal intensity changes within the retinal or choroidal arteries and veins associated with gas challenges were analyzed. Statistical analysis was performed by using paired t tests, with P < .05 considered to indicate a significant difference. Bonferroni correction was used to adjust for multiple comparisons.
Results
The central retinal artery, long posterior ciliary arteries, and choroidal vasculature could be distinguished on MR microangiograms of the eye. With MR microangiography, retinal arteries and veins could be distinguished on the basis of blood oxygen level–dependent contrast. Carbogen inhalation–enhanced MR microangiography signal intensity in both the retina (P = .001) and choroid (P = .027) compared with oxygen inhalation. Carbogen inhalation showed significantly higher signal intensity changes in the retinal arteries (P = .001, compared with oxygen inhalation), but not in the veins (P = .549). With MION administration, MR microangiography depicted retinal arterial vasoconstriction when the animals were breathing oxygen (P = .02, compared with animals breathing air).
Conclusion
MR microangiography of the eye allows depth-resolved imaging of small angiographic details of the ocular circulation. This approach may prove useful in studying microvascular pathologic findings and neurovascular dysfunction in the eye and retina.
To develop high-spatial-resolution magnetic resonance (MR) microangiography techniques to image the rat ocular circulation.
Materials and Methods
Animal experiments were performed with institutional Animal Care Committee approval. MR microangiography (resolution, 84 × 84 × 84 μm or 42 × 42 × 84 μm) of the rat eye (eight rats) was performed by using a custom-made small circular surface coil with an 11.7-T MR unit before and after monocrystalline iron oxide nanoparticle (MION) injection. MR microangiography measurements were made during air, oxygen, and carbogen inhalation. From three-dimensional MR microangiography, the retina was virtually flattened to enable en face views of various retinal depths, including the retinal and choroidal vascular layers. Signal intensity changes within the retinal or choroidal arteries and veins associated with gas challenges were analyzed. Statistical analysis was performed by using paired t tests, with P < .05 considered to indicate a significant difference. Bonferroni correction was used to adjust for multiple comparisons.
Results
The central retinal artery, long posterior ciliary arteries, and choroidal vasculature could be distinguished on MR microangiograms of the eye. With MR microangiography, retinal arteries and veins could be distinguished on the basis of blood oxygen level–dependent contrast. Carbogen inhalation–enhanced MR microangiography signal intensity in both the retina (P = .001) and choroid (P = .027) compared with oxygen inhalation. Carbogen inhalation showed significantly higher signal intensity changes in the retinal arteries (P = .001, compared with oxygen inhalation), but not in the veins (P = .549). With MION administration, MR microangiography depicted retinal arterial vasoconstriction when the animals were breathing oxygen (P = .02, compared with animals breathing air).
Conclusion
MR microangiography of the eye allows depth-resolved imaging of small angiographic details of the ocular circulation. This approach may prove useful in studying microvascular pathologic findings and neurovascular dysfunction in the eye and retina.
Liao LD, Lin CT, Shih YY, Duong TQ, Lai HY, Wang PH, Wu R, Tsang S, Chang JY, Li ML, Chen YY
Transcranial imaging of functional cerebral hemodynamic changes in single blood vessels using in vivo photoacoustic microscopyJournal of Cerebral Blood Flow and Metabolism[Press release]PubMed
@article{LD2012b,
title = {Transcranial imaging of functional cerebral hemodynamic changes in single blood vessels using in vivo photoacoustic microscopy},
author = {Liao LD, Lin CT, Shih YY, Duong TQ, Lai HY, Wang PH, Wu R, Tsang S, Chang JY, Li ML, Chen YY},
url = {https://pubmed.ncbi.nlm.nih.gov/22472612/},
doi = {10.1038/jcbfm.2012.42},
year = {2012},
date = {2012-06-01},
urldate = {2012-06-01},
journal = {Journal of Cerebral Blood Flow and Metabolism},
volume = {32},
number = {6},
pages = {938-51},
abstract = {Optical imaging of changes in total hemoglobin concentration (HbT), cerebral blood volume (CBV), and hemoglobin oxygen saturation (SO(2)) provides a means to investigate brain hemodynamic regulation. However, high-resolution transcranial imaging remains challenging. In this study, we applied a novel functional photoacoustic microscopy technique to probe the responses of single cortical vessels to left forepaw electrical stimulation in mice with intact skulls. Functional changes in HbT, CBV, and SO(2) in the superior sagittal sinus and different-sized arterioles from the anterior cerebral artery system were bilaterally imaged with unambiguous 36 × 65-μm(2) spatial resolution. In addition, an early decrease of SO(2) in single blood vessels during activation (i.e., 'the initial dip') was observed. Our results indicate that the initial dip occurred specifically in small arterioles of activated regions but not in large veins. This technique complements other existing imaging approaches for the investigation of the hemodynamic responses in single cerebral blood vessels.},
note = {Featured article},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Optical imaging of changes in total hemoglobin concentration (HbT), cerebral blood volume (CBV), and hemoglobin oxygen saturation (SO(2)) provides a means to investigate brain hemodynamic regulation. However, high-resolution transcranial imaging remains challenging. In this study, we applied a novel functional photoacoustic microscopy technique to probe the responses of single cortical vessels to left forepaw electrical stimulation in mice with intact skulls. Functional changes in HbT, CBV, and SO(2) in the superior sagittal sinus and different-sized arterioles from the anterior cerebral artery system were bilaterally imaged with unambiguous 36 × 65-μm(2) spatial resolution. In addition, an early decrease of SO(2) in single blood vessels during activation (i.e., 'the initial dip') was observed. Our results indicate that the initial dip occurred specifically in small arterioles of activated regions but not in large veins. This technique complements other existing imaging approaches for the investigation of the hemodynamic responses in single cerebral blood vessels.
Liao LD, Lin CT, Shih YY, Lai HY, Zhao WT, Duong TQ, Chang JY, Chen YY, Li ML
Investigation of the cerebral hemodynamic response function in single blood vessels by functional photoacoustic microscopyJournal of Biomedical OpticsPubMed
@article{LD2012,
title = {Investigation of the cerebral hemodynamic response function in single blood vessels by functional photoacoustic microscopy},
author = {Liao LD, Lin CT, Shih YY, Lai HY, Zhao WT, Duong TQ, Chang JY, Chen YY, Li ML},
url = {https://pubmed.ncbi.nlm.nih.gov/22734740/},
doi = {10.1117/1.JBO.17.6.061210},
year = {2012},
date = {2012-05-07},
urldate = {2012-05-07},
journal = {Journal of Biomedical Optics},
volume = {17},
number = {6},
pages = {061210},
abstract = {The specificity of the hemodynamic response function (HRF) is determined spatially by the vascular architecture and temporally by the evolution of hemodynamic changes. Here, we used functional photoacoustic microscopy (fPAM) to investigate single cerebral blood vessels of rats after left forepaw stimulation. In this system, we analyzed the spatiotemporal evolution of the HRFs of the total hemoglobin concentration (HbT), cerebral blood volume (CBV), and hemoglobin oxygen saturation (SO(2)). Changes in specific cerebral vessels corresponding to various electrical stimulation intensities and durations were bilaterally imaged with 36 × 65-μm(2) spatial resolution. Stimulation intensities of 1, 2, 6, and 10 mA were applied for periods of 5 or 15 s. Our results show that the relative functional changes in HbT, CBV, and SO(2) are highly dependent not only on the intensity of the stimulation, but also on its duration. Additionally, the duration of the stimulation has a strong influence on the spatiotemporal characteristics of the HRF as shorter stimuli elicit responses only in the local vasculature (smaller arterioles), whereas longer stimuli lead to greater vascular supply and drainage. This study suggests that the current fPAM system is reliable for studying relative cerebral hemodynamic changes, as well as for offering new insights into the dynamics of functional cerebral hemodynamic changes in small animals.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The specificity of the hemodynamic response function (HRF) is determined spatially by the vascular architecture and temporally by the evolution of hemodynamic changes. Here, we used functional photoacoustic microscopy (fPAM) to investigate single cerebral blood vessels of rats after left forepaw stimulation. In this system, we analyzed the spatiotemporal evolution of the HRFs of the total hemoglobin concentration (HbT), cerebral blood volume (CBV), and hemoglobin oxygen saturation (SO(2)). Changes in specific cerebral vessels corresponding to various electrical stimulation intensities and durations were bilaterally imaged with 36 × 65-μm(2) spatial resolution. Stimulation intensities of 1, 2, 6, and 10 mA were applied for periods of 5 or 15 s. Our results show that the relative functional changes in HbT, CBV, and SO(2) are highly dependent not only on the intensity of the stimulation, but also on its duration. Additionally, the duration of the stimulation has a strong influence on the spatiotemporal characteristics of the HRF as shorter stimuli elicit responses only in the local vasculature (smaller arterioles), whereas longer stimuli lead to greater vascular supply and drainage. This study suggests that the current fPAM system is reliable for studying relative cerebral hemodynamic changes, as well as for offering new insights into the dynamics of functional cerebral hemodynamic changes in small animals.
Lai HY, Liao LD, Lin CT, Hsu JH, He X, Chen YY, Chang JY, Chen HF, Tsang S, Shih YY
Design, simulation and experimental validation of a novel flexible neural probe for deep brain stimulation and multichannel recordingJournal of Neural EngineeringPubMed
@article{HY2012,
title = {Design, simulation and experimental validation of a novel flexible neural probe for deep brain stimulation and multichannel recording},
author = {Lai HY, Liao LD, Lin CT, Hsu JH, He X, Chen YY, Chang JY, Chen HF, Tsang S, Shih YY},
url = {https://pubmed.ncbi.nlm.nih.gov/22488106/},
doi = {10.1088/1741-2560/9/3/036001},
year = {2012},
date = {2012-04-10},
urldate = {2012-04-10},
journal = {Journal of Neural Engineering},
volume = {9},
number = {3},
pages = {036001},
abstract = {An implantable micromachined neural probe with multichannel electrode arrays for both neural signal recording and electrical stimulation was designed, simulated and experimentally validated for deep brain stimulation (DBS) applications. The developed probe has a rough three-dimensional microstructure on the electrode surface to maximize the electrode-tissue contact area. The flexible, polyimide-based microelectrode arrays were each composed of a long shaft (14.9 mm in length) and 16 electrodes (5 µm thick and with a diameter of 16 µm). The ability of these arrays to record and stimulate specific areas in a rat brain was evaluated. Moreover, we have developed a finite element model (FEM) applied to an electric field to evaluate the volume of tissue activated (VTA) by DBS as a function of the stimulation parameters. The signal-to-noise ratio ranged from 4.4 to 5 over a 50 day recording period, indicating that the laboratory-designed neural probe is reliable and may be used successfully for long-term recordings. The somatosensory evoked potential (SSEP) obtained by thalamic stimulations and in vivo electrode-electrolyte interface impedance measurements was stable for 50 days and demonstrated that the neural probe is feasible for long-term stimulation. A strongly linear (positive correlation) relationship was observed among the simulated VTA, the absolute value of the SSEP during the 200 ms post-stimulus period (ΣSSEP) and c-Fos expression, indicating that the simulated VTA has perfect sensitivity to predict the evoked responses (c-Fos expression). This laboratory-designed neural probe and its FEM simulation represent a simple, functionally effective technique for studying DBS and neural recordings in animal models.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
An implantable micromachined neural probe with multichannel electrode arrays for both neural signal recording and electrical stimulation was designed, simulated and experimentally validated for deep brain stimulation (DBS) applications. The developed probe has a rough three-dimensional microstructure on the electrode surface to maximize the electrode-tissue contact area. The flexible, polyimide-based microelectrode arrays were each composed of a long shaft (14.9 mm in length) and 16 electrodes (5 µm thick and with a diameter of 16 µm). The ability of these arrays to record and stimulate specific areas in a rat brain was evaluated. Moreover, we have developed a finite element model (FEM) applied to an electric field to evaluate the volume of tissue activated (VTA) by DBS as a function of the stimulation parameters. The signal-to-noise ratio ranged from 4.4 to 5 over a 50 day recording period, indicating that the laboratory-designed neural probe is reliable and may be used successfully for long-term recordings. The somatosensory evoked potential (SSEP) obtained by thalamic stimulations and in vivo electrode-electrolyte interface impedance measurements was stable for 50 days and demonstrated that the neural probe is feasible for long-term stimulation. A strongly linear (positive correlation) relationship was observed among the simulated VTA, the absolute value of the SSEP during the 200 ms post-stimulus period (ΣSSEP) and c-Fos expression, indicating that the simulated VTA has perfect sensitivity to predict the evoked responses (c-Fos expression). This laboratory-designed neural probe and its FEM simulation represent a simple, functionally effective technique for studying DBS and neural recordings in animal models.
De La Garza BH, Muir ER, Shih YY, Duong TQ
3D magnetic resonance microscopy of the ex vivo retinaMagnetic Resonance in MedicinePubMed
@article{BH2012,
title = {3D magnetic resonance microscopy of the ex vivo retina},
author = {De La Garza BH, Muir ER, Shih YY, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22009721/},
doi = {10.1002/mrm.23082},
year = {2012},
date = {2012-04-01},
urldate = {2012-04-01},
journal = {Magnetic Resonance in Medicine},
volume = {67},
number = {4},
pages = {1154-8},
abstract = {3D-MR microscopy at 11.7T and 20 × 20 × 57 μm resolution was performed on formalin-fixed rat eyes with: (I) no contrast agent and (II) Gadodiamide (Omniscan(®) ) added to the fixative. Group I data showed generally poor contrast among layers. Group II data showed markedly better lamina-specific contrast with the nerve fiber + ganglion cell layer and inner nuclear layer being hypointense, and the inner plexiform, outer plexiform, outer nuclear layer, and the segments being hyperintense. The signal-to-noise ratio in group II was higher than group I, consistent with Gadodiamide acting as a T(1) -contrast agent. All major retinal layers were assigned and their thicknesses quantified with corroboration by histology. MR microscopy allows nondestructive examination of valuable specimens and could have applications in disease and in vivo.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
3D-MR microscopy at 11.7T and 20 × 20 × 57 μm resolution was performed on formalin-fixed rat eyes with: (I) no contrast agent and (II) Gadodiamide (Omniscan(®) ) added to the fixative. Group I data showed generally poor contrast among layers. Group II data showed markedly better lamina-specific contrast with the nerve fiber + ganglion cell layer and inner nuclear layer being hypointense, and the inner plexiform, outer plexiform, outer nuclear layer, and the segments being hyperintense. The signal-to-noise ratio in group II was higher than group I, consistent with Gadodiamide acting as a T(1) -contrast agent. All major retinal layers were assigned and their thicknesses quantified with corroboration by histology. MR microscopy allows nondestructive examination of valuable specimens and could have applications in disease and in vivo.
Shih YY, Chiang YC, Shyu BC, Jaw FS, Duong TQ, Chang C
Endogenous opioid-dopamine neurotransmission underlie negative CBV fMRI signals@article{YY2012b,
title = {Endogenous opioid-dopamine neurotransmission underlie negative CBV fMRI signals},
author = {Shih YY, Chiang YC, Shyu BC, Jaw FS, Duong TQ, Chang C},
url = {https://pubmed.ncbi.nlm.nih.gov/22245158/},
doi = {10.1016/j.expneurol.2011.12.042},
year = {2012},
date = {2012-04-01},
urldate = {2012-04-01},
journal = {Experimental Neurology},
volume = {234},
number = {2},
pages = {382-8},
abstract = {Previous studies showed noxious unilateral forepaw electrical stimulation surprisingly evoked negative blood-oxygenation-level-dependent (BOLD), cerebral blood flow (CBF), and cerebral blood volume (CBV) fMRI responses in the bilateral striatum whereas the local neuronal spike and c-Fos activities increased. These negative responses are associated with vasoconstriction and appeared to override the increased hemodynamic responses that typically accompanied with increased neural activity. The current study aimed to investigate the role of μ-opioid system in modulating vasoconstriction in the striatum associated with noxious stimulation on a 4.7-Tesla MRI scanner. Specifically, we investigated: i) how morphine (a μ-opioid receptor agonist) affects the vasoconstriction in the bilateral striatum associated with noxious electrical forepaw stimulation in rats, and ii) how naloxone (an opioid receptor antagonist) and eticlopride (a dopamine D(2)/D(3) receptor antagonist) modulates the morphine effects onwards. Injection of morphine enhanced the negative striatal CBV responses to noxious stimulation. Sequential injection of naloxone in the same animals abolished the stimulus-evoked vasoconstriction. In a separate group of animals, injection of eticlopride following morphine also reduced the vasoconstriction. Our findings suggested that noxious stimulation endogenously activated opioid and dopamine receptors in the striatum and thus leading to vasoconstriction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Previous studies showed noxious unilateral forepaw electrical stimulation surprisingly evoked negative blood-oxygenation-level-dependent (BOLD), cerebral blood flow (CBF), and cerebral blood volume (CBV) fMRI responses in the bilateral striatum whereas the local neuronal spike and c-Fos activities increased. These negative responses are associated with vasoconstriction and appeared to override the increased hemodynamic responses that typically accompanied with increased neural activity. The current study aimed to investigate the role of μ-opioid system in modulating vasoconstriction in the striatum associated with noxious stimulation on a 4.7-Tesla MRI scanner. Specifically, we investigated: i) how morphine (a μ-opioid receptor agonist) affects the vasoconstriction in the bilateral striatum associated with noxious electrical forepaw stimulation in rats, and ii) how naloxone (an opioid receptor antagonist) and eticlopride (a dopamine D(2)/D(3) receptor antagonist) modulates the morphine effects onwards. Injection of morphine enhanced the negative striatal CBV responses to noxious stimulation. Sequential injection of naloxone in the same animals abolished the stimulus-evoked vasoconstriction. In a separate group of animals, injection of eticlopride following morphine also reduced the vasoconstriction. Our findings suggested that noxious stimulation endogenously activated opioid and dopamine receptors in the striatum and thus leading to vasoconstriction.
Rogers B, Shih YY, De La Garza BH, Harrison JM, Roby J, Duong TQ
A low cost color visual stimulator for fMRIJournal of Neuroscience MethodsPubMed
@article{W2012,
title = {A low cost color visual stimulator for fMRI},
author = {Rogers B, Shih YY, De La Garza BH, Harrison JM, Roby J, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/22172916/},
doi = {10.1016/j.jneumeth.2011.10.032},
year = {2012},
date = {2012-03-15},
urldate = {2012-03-15},
journal = {Journal of Neuroscience Methods},
volume = {204},
number = {2},
pages = {379-82},
abstract = {This low cost visual stimulator was developed for use in small animal imaging. The stimulator uses a single tri-color LED for each eye and can output red, green, or blue light or any combination of the three. When all three LED colors are illuminated at the same time achromatic light is the output. The stimulator is almost entirely implemented in software with only minimal electronics. The LEDs are controlled via the parallel port of a desktop computer. Flicker frequency, wavelength, intensity and waveform shape are under software control. The LEDs are coupled to fiber optic cables which run into the MRI scanner room leaving the LEDs and the power source in the control room. Calibration with a radiometer shows the light output to be very linear from zero to full intensity. The stimulator was used in fMRI visual stimulation studies performed on Sprague Dawley rats with an 11.7 Tesla magnet. As the stimulator is software driven, modifications to accommodate other protocols and extensions for new functionality can be readily incorporated. With this in mind, the visual stimulator circuit diagram and software including source code are available upon request.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This low cost visual stimulator was developed for use in small animal imaging. The stimulator uses a single tri-color LED for each eye and can output red, green, or blue light or any combination of the three. When all three LED colors are illuminated at the same time achromatic light is the output. The stimulator is almost entirely implemented in software with only minimal electronics. The LEDs are controlled via the parallel port of a desktop computer. Flicker frequency, wavelength, intensity and waveform shape are under software control. The LEDs are coupled to fiber optic cables which run into the MRI scanner room leaving the LEDs and the power source in the control room. Calibration with a radiometer shows the light output to be very linear from zero to full intensity. The stimulator was used in fMRI visual stimulation studies performed on Sprague Dawley rats with an 11.7 Tesla magnet. As the stimulator is software driven, modifications to accommodate other protocols and extensions for new functionality can be readily incorporated. With this in mind, the visual stimulator circuit diagram and software including source code are available upon request.
Chao WH, Lin SH, Shih YY, Chen YY, Lo YC, Lin SH, Tsang S, Wu R,; Jaw FS
Correction of inhomogeneous magnetic resonance images using multiscale retinex for segmentation accuracy improvementBiomedical Signal Processing and Control
@article{WH2012,
title = {Correction of inhomogeneous magnetic resonance images using multiscale retinex for segmentation accuracy improvement},
author = {Chao WH, Lin SH, Shih YY, Chen YY, Lo YC, Lin SH, Tsang S, Wu R, and Jaw FS},
doi = {10.1016/j.bspc.2011.04.001},
year = {2012},
date = {2012-03-01},
urldate = {2012-03-01},
journal = {Biomedical Signal Processing and Control},
volume = {7},
number = {2},
pages = {129-40},
abstract = {The purpose of this study was to improve the accuracy of tissue segmentation on brain magnetic resonance (MR) images preprocessed by multiscale retinex (MSR), segmented with a combined boosted decision tree (BDT) and MSR algorithm (hereinafter referred to as the MSRBDT algorithm). Simulated brain MR (SBMR) T1-weighted images of different noise levels and RF inhomogeneities were adopted to evaluate the outcome of the proposed method; the MSRBDT algorithm was used to identify the gray matter (GM), white matter (WM), and cerebral-spinal fluid (CSF) in the brain tissues. The accuracy rates of GM, WM, and CSF segmentation, with spatial features (G, x, y, r, θ), were respectively greater than 0.9805, 0.9817, and 0.9871. In addition, images segmented with the MSRBDT algorithm were better than those obtained with the expectation maximization (EM) algorithm; brain tissue segmentation in MR images was significantly more precise. The proposed MSRBDT algorithm could be beneficial in clinical image segmentation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The purpose of this study was to improve the accuracy of tissue segmentation on brain magnetic resonance (MR) images preprocessed by multiscale retinex (MSR), segmented with a combined boosted decision tree (BDT) and MSR algorithm (hereinafter referred to as the MSRBDT algorithm). Simulated brain MR (SBMR) T1-weighted images of different noise levels and RF inhomogeneities were adopted to evaluate the outcome of the proposed method; the MSRBDT algorithm was used to identify the gray matter (GM), white matter (WM), and cerebral-spinal fluid (CSF) in the brain tissues. The accuracy rates of GM, WM, and CSF segmentation, with spatial features (G, x, y, r, θ), were respectively greater than 0.9805, 0.9817, and 0.9871. In addition, images segmented with the MSRBDT algorithm were better than those obtained with the expectation maximization (EM) algorithm; brain tissue segmentation in MR images was significantly more precise. The proposed MSRBDT algorithm could be beneficial in clinical image segmentation.
Hsu YC, Shih YY, Chang CF, Huang GS
A rare case of coiling of the brachial artery: a description of the sonographic featuresJournal of Medical UltrasonicsPubMed
@article{YC2012,
title = {A rare case of coiling of the brachial artery: a description of the sonographic features},
author = {Hsu YC, Shih YY, Chang CF, Huang GS},
url = {https://pubmed.ncbi.nlm.nih.gov/27278701/},
doi = {10.1007/s10396-011-0330-y},
year = {2012},
date = {2012-01-01},
urldate = {2012-01-01},
journal = {Journal of Medical Ultrasonics},
volume = {39},
number = {1},
pages = {21-4},
abstract = {We report the case of a patient with 360° coiling of the brachial artery that had been previously misdiagnosed as aneurysms of the right brachial artery on sonography performed at another institution. The previous misdiagnosis occurred due to sonographic pitfalls in gray-scale and color imaging, which led the operator to make a false interpretation. Knowledge of Doppler analysis and sonographic interpretation of arterial coiling may improve the diagnostic accuracy for this condition.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the case of a patient with 360° coiling of the brachial artery that had been previously misdiagnosed as aneurysms of the right brachial artery on sonography performed at another institution. The previous misdiagnosis occurred due to sonographic pitfalls in gray-scale and color imaging, which led the operator to make a false interpretation. Knowledge of Doppler analysis and sonographic interpretation of arterial coiling may improve the diagnostic accuracy for this condition.
2011
Shih YY, Hsu YH, Duong TQ, Lin SS, Chow KP, Chang C
Longitudinal study of tumor-associated macrophages during tumor expansion using MRI@article{YY2011,
title = {Longitudinal study of tumor-associated macrophages during tumor expansion using MRI},
author = {Shih YY, Hsu YH, Duong TQ, Lin SS, Chow KP, Chang C},
url = {https://pubmed.ncbi.nlm.nih.gov/22223366/},
doi = {10.1002/nbm.1698},
year = {2011},
date = {2011-12-01},
urldate = {2011-12-01},
journal = {NMR in Biomedicine},
volume = {24},
number = {10},
pages = {1353-60},
abstract = {MRI is being used increasingly for the noninvasive longitudinal monitoring of cellular processes in various pathophysiological conditions. Macrophages are the main stromal cells in neoplasms and have been suggested to be the major cell type ingesting superparamagnetic iron oxide (SPIO) nanoparticles. However, no MRI study has described longitudinally the presence of tumor-associated macrophages (TAMs) during tumorigenesis with histological confirmation. To address this, we injected SPIO nanoparticles into the circulation of tumor-bearing mice and used MRI and post-mortem histology to monitor TAMs at different time points. The MRI results demonstrated that TAMs, as hypointense signals, appeared continually with the expansion of the tumor. The histological findings also revealed that SPIO-labeled TAMs tended to deposit closer to the vessel lumen with time prior to rapid tumor growth. The present study demonstrates the potential of using MRI to assess longitudinally TAM accumulation during tumorigenesis, and provides the first in vivo insight into the topographical arrangement of TAMs in relation to the progression of tumors. In vivo monitoring of the presence of TAMs could be useful for the development of tumor treatments that target TAM functions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
MRI is being used increasingly for the noninvasive longitudinal monitoring of cellular processes in various pathophysiological conditions. Macrophages are the main stromal cells in neoplasms and have been suggested to be the major cell type ingesting superparamagnetic iron oxide (SPIO) nanoparticles. However, no MRI study has described longitudinally the presence of tumor-associated macrophages (TAMs) during tumorigenesis with histological confirmation. To address this, we injected SPIO nanoparticles into the circulation of tumor-bearing mice and used MRI and post-mortem histology to monitor TAMs at different time points. The MRI results demonstrated that TAMs, as hypointense signals, appeared continually with the expansion of the tumor. The histological findings also revealed that SPIO-labeled TAMs tended to deposit closer to the vessel lumen with time prior to rapid tumor growth. The present study demonstrates the potential of using MRI to assess longitudinally TAM accumulation during tumorigenesis, and provides the first in vivo insight into the topographical arrangement of TAMs in relation to the progression of tumors. In vivo monitoring of the presence of TAMs could be useful for the development of tumor treatments that target TAM functions.
Shih YY, De La Garza BH, Muir ER, Rogers WE, Harrison JM, Kiel JW, Duong TQ
Lamina-Specific Functional MRI of Retinal and Choroidal Responses to Visual StimuliInvestigative Ophthalmology & Visual SciencePubMed
@article{YY2011b,
title = {Lamina-Specific Functional MRI of Retinal and Choroidal Responses to Visual Stimuli},
author = {Shih YY, De La Garza BH, Muir ER, Rogers WE, Harrison JM, Kiel JW, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/21447679/},
doi = {10.1167/iovs.10-6438},
year = {2011},
date = {2011-07-15},
urldate = {2011-07-15},
journal = {Investigative Ophthalmology & Visual Science},
volume = {52},
number = {8},
pages = {5303-10},
abstract = {Purpose.
To demonstrate lamina-specific functional magnetic resonance imaging (MRI) of retinal and choroidal responses to visual stimulation of graded luminance, wavelength, and frequency.
Materials and Methods.
High-resolution (60 × 60μm) MRI was achieved using the blood-pool contrast agent, monocrystalline iron oxide nanoparticles (MION) and a high-magnetic-field (11.7 T) scanner to image functional changes in the normal rat retina associated with various visual stimulations. MION functional MRI measured stimulus-evoked blood-volume (BV) changes. Graded luminance, wavelength, and frequency were investigated. Stimulus-evoked fMRI signal changes from the retinal and choroidal vascular layers were analyzed.
Results.
MRI revealed two distinct laminar signals that corresponded to the retinal and choroidal vascular layers bounding the retina and were separated by the avascular layer in between. The baseline outer layer BV index was 2–4 times greater than the inner layer BV, consistent with higher choroidal vascular density. During visual stimulation, BV responses to flickering light of different luminance, frequency, and wavelength in the inner layer were greater than those in the outer layer. The inner layer responses were dependent on luminance, frequency, and wavelength, whereas the outer layer responses were not, suggesting differential neurovascular coupling between the two vasculatures.
Conclusions.
This is the first report of simultaneous resolution of layer-specific functional responses of the retinal and choroid vascular layers to visual stimulation in the retina. This imaging approach could have applications in early detection and longitudinal monitoring of retinal diseases where retinal and choroidal hemodynamics may be differentially perturbed at various stages of the diseases.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Purpose.
To demonstrate lamina-specific functional magnetic resonance imaging (MRI) of retinal and choroidal responses to visual stimulation of graded luminance, wavelength, and frequency.
Materials and Methods.
High-resolution (60 × 60μm) MRI was achieved using the blood-pool contrast agent, monocrystalline iron oxide nanoparticles (MION) and a high-magnetic-field (11.7 T) scanner to image functional changes in the normal rat retina associated with various visual stimulations. MION functional MRI measured stimulus-evoked blood-volume (BV) changes. Graded luminance, wavelength, and frequency were investigated. Stimulus-evoked fMRI signal changes from the retinal and choroidal vascular layers were analyzed.
Results.
MRI revealed two distinct laminar signals that corresponded to the retinal and choroidal vascular layers bounding the retina and were separated by the avascular layer in between. The baseline outer layer BV index was 2–4 times greater than the inner layer BV, consistent with higher choroidal vascular density. During visual stimulation, BV responses to flickering light of different luminance, frequency, and wavelength in the inner layer were greater than those in the outer layer. The inner layer responses were dependent on luminance, frequency, and wavelength, whereas the outer layer responses were not, suggesting differential neurovascular coupling between the two vasculatures.
Conclusions.
This is the first report of simultaneous resolution of layer-specific functional responses of the retinal and choroid vascular layers to visual stimulation in the retina. This imaging approach could have applications in early detection and longitudinal monitoring of retinal diseases where retinal and choroidal hemodynamics may be differentially perturbed at various stages of the diseases.
To demonstrate lamina-specific functional magnetic resonance imaging (MRI) of retinal and choroidal responses to visual stimulation of graded luminance, wavelength, and frequency.
Materials and Methods.
High-resolution (60 × 60μm) MRI was achieved using the blood-pool contrast agent, monocrystalline iron oxide nanoparticles (MION) and a high-magnetic-field (11.7 T) scanner to image functional changes in the normal rat retina associated with various visual stimulations. MION functional MRI measured stimulus-evoked blood-volume (BV) changes. Graded luminance, wavelength, and frequency were investigated. Stimulus-evoked fMRI signal changes from the retinal and choroidal vascular layers were analyzed.
Results.
MRI revealed two distinct laminar signals that corresponded to the retinal and choroidal vascular layers bounding the retina and were separated by the avascular layer in between. The baseline outer layer BV index was 2–4 times greater than the inner layer BV, consistent with higher choroidal vascular density. During visual stimulation, BV responses to flickering light of different luminance, frequency, and wavelength in the inner layer were greater than those in the outer layer. The inner layer responses were dependent on luminance, frequency, and wavelength, whereas the outer layer responses were not, suggesting differential neurovascular coupling between the two vasculatures.
Conclusions.
This is the first report of simultaneous resolution of layer-specific functional responses of the retinal and choroid vascular layers to visual stimulation in the retina. This imaging approach could have applications in early detection and longitudinal monitoring of retinal diseases where retinal and choroidal hemodynamics may be differentially perturbed at various stages of the diseases.
Lai HY, Chen YY, Lin SH, Lo YC, Tsang S, Chen SY, Zhao WT, Chao WH, Chang YC, Wu R, Shih YY, Tsai ST, Jaw FS
Automatic spike sorting for extracellular electrophysiological recording using unsupervised single linkage clustering based on grey relational analysisJournal of Neural EngineeringPubMed
@article{HY2011,
title = {Automatic spike sorting for extracellular electrophysiological recording using unsupervised single linkage clustering based on grey relational analysis},
author = {Lai HY, Chen YY, Lin SH, Lo YC, Tsang S, Chen SY, Zhao WT, Chao WH, Chang YC, Wu R, Shih YY, Tsai ST, Jaw FS},
url = {https://pubmed.ncbi.nlm.nih.gov/21464520/},
doi = {10.1088/1741-2560/8/3/036003},
year = {2011},
date = {2011-04-04},
urldate = {2011-04-04},
journal = {Journal of Neural Engineering},
volume = {8},
number = {3},
pages = {036003},
abstract = {Automatic spike sorting is a prerequisite for neuroscience research on multichannel extracellular recordings of neuronal activity. A novel spike sorting framework, combining efficient feature extraction and an unsupervised clustering method, is described here. Wavelet transform (WT) is adopted to extract features from each detected spike, and the Kolmogorov-Smirnov test (KS test) is utilized to select discriminative wavelet coefficients from the extracted features. Next, an unsupervised single linkage clustering method based on grey relational analysis (GSLC) is applied for spike clustering. The GSLC uses the grey relational grade as the similarity measure, instead of the Euclidean distance for distance calculation; the number of clusters is automatically determined by the elbow criterion in the threshold-cumulative distribution. Four simulated data sets with four noise levels and electrophysiological data recorded from the subthalamic nucleus of eight patients with Parkinson's disease during deep brain stimulation surgery are used to evaluate the performance of GSLC. Feature extraction results from the use of WT with the KS test indicate a reduced number of feature coefficients, as well as good noise rejection, despite similar spike waveforms. Accordingly, the use of GSLC for spike sorting achieves high classification accuracy in all simulated data sets. Moreover, J-measure results in the electrophysiological data indicating that the quality of spike sorting is adequate with the use of GSLC.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Automatic spike sorting is a prerequisite for neuroscience research on multichannel extracellular recordings of neuronal activity. A novel spike sorting framework, combining efficient feature extraction and an unsupervised clustering method, is described here. Wavelet transform (WT) is adopted to extract features from each detected spike, and the Kolmogorov-Smirnov test (KS test) is utilized to select discriminative wavelet coefficients from the extracted features. Next, an unsupervised single linkage clustering method based on grey relational analysis (GSLC) is applied for spike clustering. The GSLC uses the grey relational grade as the similarity measure, instead of the Euclidean distance for distance calculation; the number of clusters is automatically determined by the elbow criterion in the threshold-cumulative distribution. Four simulated data sets with four noise levels and electrophysiological data recorded from the subthalamic nucleus of eight patients with Parkinson's disease during deep brain stimulation surgery are used to evaluate the performance of GSLC. Feature extraction results from the use of WT with the KS test indicate a reduced number of feature coefficients, as well as good noise rejection, despite similar spike waveforms. Accordingly, the use of GSLC for spike sorting achieves high classification accuracy in all simulated data sets. Moreover, J-measure results in the electrophysiological data indicating that the quality of spike sorting is adequate with the use of GSLC.
Shih YY, Wey HY, De La Garza BH, Duong TQ
Striatal and cortical BOLD, blood flow, blood volume, oxygen consumption, and glucose consumption changes in noxious forepaw electrical stimulationJournal of Cerebral Blood Flow and Metabolism[Press release]PubMed
@article{YY2011b,
title = {Striatal and cortical BOLD, blood flow, blood volume, oxygen consumption, and glucose consumption changes in noxious forepaw electrical stimulation},
author = {Shih YY, Wey HY, De La Garza BH, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/20940730/},
doi = {10.1038/jcbfm.2010.173},
year = {2011},
date = {2011-03-01},
urldate = {2011-03-01},
journal = {Journal of Cerebral Blood Flow and Metabolism},
volume = {31},
number = {3},
pages = {832-41},
abstract = {Recent reports showed noxious forepaw stimulation in rats evoked an unexpected sustained decrease in cerebral blood volume (CBV) in the bilateral striatum, whereas increases in spike activity and Fos-immunoreactive cells were observed. This study aimed to further evaluate the hemodynamic and metabolic needs in this model and the sources of negative functional magnetic resonance imaging (fMRI) signals by measuring blood oxygenation-level-dependent (BOLD), cerebral-blood-flow (CBF), CBV, and oxygen-consumption (i.e., cerebral metabolic rate of oxygen (CMRO(2))) changes using an 11.7-T MRI scanner, and glucose-consumption (i.e., cerebral metabolic rate of glucose (CMRglc)) changes using micro-positron emission tomography. In the contralateral somatosensory cortex, BOLD, CBF, CBV, CMRO(2) (n=7, P<0.05), and CMRglc (n=5, P<0.05) increased. In contrast, in the bilateral striatum, BOLD, CBF, and CBV decreased (P<0.05), CMRO(2) decreased slightly, although not significantly from baseline, and CMRglc was not statistically significant from baseline (P>0.05). These multimodal functional imaging findings corroborate the unexpected negative hemodynamic changes in the striatum during noxious forepaw stimulation, and support the hypothesis that striatal hemodynamic response is dominated by neurotransmitter-mediated vasoconstriction, overriding the stimulus-evoked fMRI signal increases commonly accompany elevated neuronal activity. Multimodal functional imaging approach offers a means to probe the unique attributes of the striatum, providing novel insights into the neurovascular coupling in the striatum. These findings may have strong implications in fMRI studies of pain.},
note = {Featured article},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recent reports showed noxious forepaw stimulation in rats evoked an unexpected sustained decrease in cerebral blood volume (CBV) in the bilateral striatum, whereas increases in spike activity and Fos-immunoreactive cells were observed. This study aimed to further evaluate the hemodynamic and metabolic needs in this model and the sources of negative functional magnetic resonance imaging (fMRI) signals by measuring blood oxygenation-level-dependent (BOLD), cerebral-blood-flow (CBF), CBV, and oxygen-consumption (i.e., cerebral metabolic rate of oxygen (CMRO(2))) changes using an 11.7-T MRI scanner, and glucose-consumption (i.e., cerebral metabolic rate of glucose (CMRglc)) changes using micro-positron emission tomography. In the contralateral somatosensory cortex, BOLD, CBF, CBV, CMRO(2) (n=7, P<0.05), and CMRglc (n=5, P<0.05) increased. In contrast, in the bilateral striatum, BOLD, CBF, and CBV decreased (P<0.05), CMRO(2) decreased slightly, although not significantly from baseline, and CMRglc was not statistically significant from baseline (P>0.05). These multimodal functional imaging findings corroborate the unexpected negative hemodynamic changes in the striatum during noxious forepaw stimulation, and support the hypothesis that striatal hemodynamic response is dominated by neurotransmitter-mediated vasoconstriction, overriding the stimulus-evoked fMRI signal increases commonly accompany elevated neuronal activity. Multimodal functional imaging approach offers a means to probe the unique attributes of the striatum, providing novel insights into the neurovascular coupling in the striatum. These findings may have strong implications in fMRI studies of pain.
De La Garza BH, Muir ER, Li G, Shih YY, Duong TQ
Blood oxygenation level-dependent (BOLD) fMRI of visual stimulation in the rat retina at 11.7 Tesla@article{BH2011,
title = {Blood oxygenation level-dependent (BOLD) fMRI of visual stimulation in the rat retina at 11.7 Tesla},
author = {De La Garza BH, Muir ER, Li G, Shih YY, Duong TQ},
url = {https://pubmed.ncbi.nlm.nih.gov/21344533/},
doi = {10.1002/nbm.1571},
year = {2011},
date = {2011-02-01},
urldate = {2011-02-01},
journal = {NMR in Biomedicine},
volume = {24},
number = {2},
pages = {188-93},
abstract = {Although optically based imaging techniques provide valuable functional and physiological information of the retina, they are mostly limited to the probing of the retinal surface and require an unobstructed light path. MRI, in contrast, could offer physiological and functional data without depth limitation. Blood oxygenation level-dependent functional MRI (BOLD fMRI) of the thin rat retina is, however, challenging because of the need for high spatial resolution, and the potential presence of eye movement and susceptibility artifacts. This study reports a novel application of high-resolution (111 × 111 × 1000 µm3) BOLD fMRI of visual stimulation in the anesthetized rat retina at 11.7 T. A high-field MRI scanner was utilized to improve the signal-to-noise ratio, spatial resolution and BOLD sensitivity. Visual stimuli (8 Hz diffuse achromatic light) robustly increased BOLD responses in the retina [5.0 ± 0.8% from activated pixels and 3.1 ± 1.1% from the whole-retina region of interest (mean ± SD), n = 12 trials on six rats, p < 0.05 compared with baseline]. Some activated pixels were detected surrounding the pupil and ciliary muscle because of accommodation reflex to visual stimuli, and were reduced with atropine and phenylephrine eye drops. BOLD fMRI scans without visual stimulations showed no significantly activated pixels (whole-retina BOLD changes were 0.08 ± 0.34%, n = 6 trials on five rats, not statistically different from baseline, p > 0.05). BOLD fMRI of visual stimulation has the potential to provide clinically relevant data to probe hemodynamic neurovascular coupling and dysfunction of the retina with depth resolution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Although optically based imaging techniques provide valuable functional and physiological information of the retina, they are mostly limited to the probing of the retinal surface and require an unobstructed light path. MRI, in contrast, could offer physiological and functional data without depth limitation. Blood oxygenation level-dependent functional MRI (BOLD fMRI) of the thin rat retina is, however, challenging because of the need for high spatial resolution, and the potential presence of eye movement and susceptibility artifacts. This study reports a novel application of high-resolution (111 × 111 × 1000 µm3) BOLD fMRI of visual stimulation in the anesthetized rat retina at 11.7 T. A high-field MRI scanner was utilized to improve the signal-to-noise ratio, spatial resolution and BOLD sensitivity. Visual stimuli (8 Hz diffuse achromatic light) robustly increased BOLD responses in the retina [5.0 ± 0.8% from activated pixels and 3.1 ± 1.1% from the whole-retina region of interest (mean ± SD), n = 12 trials on six rats, p < 0.05 compared with baseline]. Some activated pixels were detected surrounding the pupil and ciliary muscle because of accommodation reflex to visual stimuli, and were reduced with atropine and phenylephrine eye drops. BOLD fMRI scans without visual stimulations showed no significantly activated pixels (whole-retina BOLD changes were 0.08 ± 0.34%, n = 6 trials on five rats, not statistically different from baseline, p > 0.05). BOLD fMRI of visual stimulation has the potential to provide clinically relevant data to probe hemodynamic neurovascular coupling and dysfunction of the retina with depth resolution.
2010
Liao LD, Li ML, Lai HY, Shih YY, Lo YC, Tsang S, Chao CP, Lin CT, Jaw FS, Chen YY
Imaging brain hemodynamic changes during rat forepaw electrical stimulation using functional photoacoustic microscopy@article{LD2010,
title = {Imaging brain hemodynamic changes during rat forepaw electrical stimulation using functional photoacoustic microscopy},
author = {Liao LD, Li ML, Lai HY, Shih YY, Lo YC, Tsang S, Chao CP, Lin CT, Jaw FS, Chen YY},
url = {https://pubmed.ncbi.nlm.nih.gov/20362680/},
doi = {10.1016/j.neuroimage.2010.03.065},
year = {2010},
date = {2010-08-15},
urldate = {2010-08-15},
journal = {NeuroImage},
volume = {52},
number = {2},
pages = {562-70},
abstract = {The present study reported the development of a novel functional photoacoustic microscopy (fPAM) system for investigating hemodynamic changes in rat cortical vessels associated with electrical forepaw stimulation. Imaging of blood optical absorption by fPAM at multiple appropriately-selected and distinct wavelengths can be used to probe changes in total hemoglobin concentration (HbT, i.e., cerebral blood volume [CBV]) and hemoglobin oxygen saturation (SO(2)). Changes in CBV were measured by images acquired at a wavelength of 570nm (lambda(570)), an isosbestic point of the molar extinction spectra of oxy- and deoxy-hemoglobin, whereas SO(2) changes were sensed by pixel-wise normalization of images acquired at lambda(560) or lambda(600) to those at lambda(570). We demonstrated the capacity of the fPAM system to image and quantify significant contralateral changes in both SO(2) and CBV driven by electrical forepaw stimulation. The fPAM system complements existing imaging techniques, with the potential to serve as a favorable tool for explicitly studying brain hemodynamics in animal models.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The present study reported the development of a novel functional photoacoustic microscopy (fPAM) system for investigating hemodynamic changes in rat cortical vessels associated with electrical forepaw stimulation. Imaging of blood optical absorption by fPAM at multiple appropriately-selected and distinct wavelengths can be used to probe changes in total hemoglobin concentration (HbT, i.e., cerebral blood volume [CBV]) and hemoglobin oxygen saturation (SO(2)). Changes in CBV were measured by images acquired at a wavelength of 570nm (lambda(570)), an isosbestic point of the molar extinction spectra of oxy- and deoxy-hemoglobin, whereas SO(2) changes were sensed by pixel-wise normalization of images acquired at lambda(560) or lambda(600) to those at lambda(570). We demonstrated the capacity of the fPAM system to image and quantify significant contralateral changes in both SO(2) and CBV driven by electrical forepaw stimulation. The fPAM system complements existing imaging techniques, with the potential to serve as a favorable tool for explicitly studying brain hemodynamics in animal models.
Chen YY, Shih YY, Lo YC, Lu PL, Tsang S, Jaw FS, Liu RS
MicroPET imaging of noxious thermal stimuli in the conscious rat brainSomatosensory & Motor ResearchPubMed
@article{YY2010,
title = {MicroPET imaging of noxious thermal stimuli in the conscious rat brain},
author = {Chen YY, Shih YY, Lo YC, Lu PL, Tsang S, Jaw FS, Liu RS},
url = {https://pubmed.ncbi.nlm.nih.gov/20735340/},
doi = {10.3109/08990220.2010.508222},
year = {2010},
date = {2010-08-01},
urldate = {2010-08-01},
journal = {Somatosensory & Motor Research},
volume = {27},
number = {3},
pages = {69-81},
abstract = {Small animal positron emission tomography (microPET) has been utilized in the investigation of nociception. However, a possible drawback from previous studies is the reduced activation pattern due to the application of anesthesia. The purpose of the present study was to demonstrate a potential means of avoiding anesthesia during stimulation, as well as minimizing the confounding anesthetic effect. Sodium pentobarbital and ketamine were first evaluated to determine their effect on microPET images in the current study. [(18)F]-Fluorodeoxyglucose ((18)F-FDG) was an appropriate radiotracer to reveal activated regions in rat brains. Pentobarbital anesthesia significantly reduced (18)F-FDG uptake in neural tissues, blurrier to lower contrast; therefore, ketamine was used to anesthetize animals during microPET. After the rats were anesthetized and secured in a laboratory-made stereotaxic frame, a simple, noninvasive stereotaxic technique was used to position their heads in the microPET scanner and to roughly conform the images in the stereotaxic atlas. For functional imaging, conscious rats were restrained in cages with minimal ambient noise; short repetitive thermal stimuli were applied to each rat's tail subsequently. The rats were adequately anesthetized with ketamine following 30 min of scanning without stimulation. An activation index (AI) was calculated from microPET data to quantify the local metabolic activity changes according to the normalized (18)F-FDG dosage. The average AI indicated a side-to-side difference for all innocuous stimulations in the thalamus. However, such side-to-side difference was only observed for noxious heat and cold stimulations in primary somatosensory cortex (SI), secondary somatosensory cortex (SII), and agranular insular cortex (AIC). The present study demonstrated the feasibility of the microPET technique to image metabolic functions of the conscious rat brain, offering better rationale and protocol designs for future pain studies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Small animal positron emission tomography (microPET) has been utilized in the investigation of nociception. However, a possible drawback from previous studies is the reduced activation pattern due to the application of anesthesia. The purpose of the present study was to demonstrate a potential means of avoiding anesthesia during stimulation, as well as minimizing the confounding anesthetic effect. Sodium pentobarbital and ketamine were first evaluated to determine their effect on microPET images in the current study. [(18)F]-Fluorodeoxyglucose ((18)F-FDG) was an appropriate radiotracer to reveal activated regions in rat brains. Pentobarbital anesthesia significantly reduced (18)F-FDG uptake in neural tissues, blurrier to lower contrast; therefore, ketamine was used to anesthetize animals during microPET. After the rats were anesthetized and secured in a laboratory-made stereotaxic frame, a simple, noninvasive stereotaxic technique was used to position their heads in the microPET scanner and to roughly conform the images in the stereotaxic atlas. For functional imaging, conscious rats were restrained in cages with minimal ambient noise; short repetitive thermal stimuli were applied to each rat's tail subsequently. The rats were adequately anesthetized with ketamine following 30 min of scanning without stimulation. An activation index (AI) was calculated from microPET data to quantify the local metabolic activity changes according to the normalized (18)F-FDG dosage. The average AI indicated a side-to-side difference for all innocuous stimulations in the thalamus. However, such side-to-side difference was only observed for noxious heat and cold stimulations in primary somatosensory cortex (SI), secondary somatosensory cortex (SII), and agranular insular cortex (AIC). The present study demonstrated the feasibility of the microPET technique to image metabolic functions of the conscious rat brain, offering better rationale and protocol designs for future pain studies.
Hsu YC, Shih YY, Gao GW, Huang GS
Intramuscular Schwannoma arising from the Psoas muscle presenting with femoral nerve neuropathyThe Southern Medical JournalPubMed
@article{YC2010,
title = {Intramuscular Schwannoma arising from the Psoas muscle presenting with femoral nerve neuropathy},
author = {Hsu YC, Shih YY, Gao GW, Huang GS},
url = {https://pubmed.ncbi.nlm.nih.gov/20375951/},
doi = {10.1097/SMJ.0b013e3181d7b497},
year = {2010},
date = {2010-05-01},
urldate = {2010-05-01},
journal = {The Southern Medical Journal},
volume = {103},
number = {5},
pages = {477-9},
abstract = {A spherical mass of the right psoas muscle was found incidentally by magnetic resonance health examination in a 43-year-old woman. The patient had complained of numbness in her right leg over the previous six months and neuralgia at the time of computed tomography-guided core biopsy, which was done to establish the diagnosis. To our knowledge, femoral nerve neuropathy caused by an intramuscular schwannoma arising from the psoas muscle has not been previously published.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A spherical mass of the right psoas muscle was found incidentally by magnetic resonance health examination in a 43-year-old woman. The patient had complained of numbness in her right leg over the previous six months and neuralgia at the time of computed tomography-guided core biopsy, which was done to establish the diagnosis. To our knowledge, femoral nerve neuropathy caused by an intramuscular schwannoma arising from the psoas muscle has not been previously published.
Hsu YC, Pan RY, Shih YY, Lee MS, Huang GS
Superior-capsular elongation and its significance in atraumatic posteroinferior multidirectional shoulder instability in MR arthrography@article{YC2010b,
title = {Superior-capsular elongation and its significance in atraumatic posteroinferior multidirectional shoulder instability in MR arthrography},
author = {Hsu YC, Pan RY, Shih YY, Lee MS, Huang GS},
url = {https://pubmed.ncbi.nlm.nih.gov/20158433/},
doi = {10.3109/02841850903524421},
year = {2010},
date = {2010-04-01},
urldate = {2010-04-01},
journal = {Acta Radiologica},
volume = {51},
number = {3},
pages = {302-8},
abstract = {BACKGROUND:
Redundancy of the capsule has been considered to be the main pathologic condition responsible for atraumatic posteroinferior multidirectional shoulder instability; however, there is a paucity of measurements providing quantitative diagnosis.
PURPOSE:
To determine the significance of superior-capsular elongation and its relevance to atraumatic posteroinferior multidirectional shoulder instability at magnetic resonance (MR) arthrography.
MATERIAL AND METHODS:
MR arthrography was performed in 21 patients with atraumatic posteroinferior multidirectional shoulder instability and 21 patients without shoulder instability. One observer made the measurements in duplicate and was blinded to the two groups. The superior-capsular measurements (linear distance and cross-sectional area) under the supraspinatus tendon, and the rotator interval were determined on MR arthrography and evaluated for each of the two groups.
RESULTS:
For the superior-capsular measurements, the linear distance under the supraspinatus tendon was significantly longer in patients with atraumatic posteroinferior multidirectional shoulder instability than in control subjects (P<0.001). The cross-sectional area under the supraspinatus tendon, and the rotator interval were significantly increased in patients with atraumatic posteroinferior multidirectional shoulder instability compared to control subjects (P<0.001 and P=0.01, respectively). Linear distance greater than 1.6 mm under the supraspinatus tendon had a specificity of 95% and a sensitivity of 90% for diagnosing atraumatic posteroinferior multidirectional shoulder instability. Cross-sectional area under the supraspinatus tendon greater than 0.3 cm(2), or an area under the rotator interval greater than 1.4 cm(2) had a specificity of more than 80% and a sensitivity of 90%.
CONCLUSION:
The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
BACKGROUND:
Redundancy of the capsule has been considered to be the main pathologic condition responsible for atraumatic posteroinferior multidirectional shoulder instability; however, there is a paucity of measurements providing quantitative diagnosis.
PURPOSE:
To determine the significance of superior-capsular elongation and its relevance to atraumatic posteroinferior multidirectional shoulder instability at magnetic resonance (MR) arthrography.
MATERIAL AND METHODS:
MR arthrography was performed in 21 patients with atraumatic posteroinferior multidirectional shoulder instability and 21 patients without shoulder instability. One observer made the measurements in duplicate and was blinded to the two groups. The superior-capsular measurements (linear distance and cross-sectional area) under the supraspinatus tendon, and the rotator interval were determined on MR arthrography and evaluated for each of the two groups.
RESULTS:
For the superior-capsular measurements, the linear distance under the supraspinatus tendon was significantly longer in patients with atraumatic posteroinferior multidirectional shoulder instability than in control subjects (P<0.001). The cross-sectional area under the supraspinatus tendon, and the rotator interval were significantly increased in patients with atraumatic posteroinferior multidirectional shoulder instability compared to control subjects (P<0.001 and P=0.01, respectively). Linear distance greater than 1.6 mm under the supraspinatus tendon had a specificity of 95% and a sensitivity of 90% for diagnosing atraumatic posteroinferior multidirectional shoulder instability. Cross-sectional area under the supraspinatus tendon greater than 0.3 cm(2), or an area under the rotator interval greater than 1.4 cm(2) had a specificity of more than 80% and a sensitivity of 90%.
CONCLUSION:
The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation.
Redundancy of the capsule has been considered to be the main pathologic condition responsible for atraumatic posteroinferior multidirectional shoulder instability; however, there is a paucity of measurements providing quantitative diagnosis.
PURPOSE:
To determine the significance of superior-capsular elongation and its relevance to atraumatic posteroinferior multidirectional shoulder instability at magnetic resonance (MR) arthrography.
MATERIAL AND METHODS:
MR arthrography was performed in 21 patients with atraumatic posteroinferior multidirectional shoulder instability and 21 patients without shoulder instability. One observer made the measurements in duplicate and was blinded to the two groups. The superior-capsular measurements (linear distance and cross-sectional area) under the supraspinatus tendon, and the rotator interval were determined on MR arthrography and evaluated for each of the two groups.
RESULTS:
For the superior-capsular measurements, the linear distance under the supraspinatus tendon was significantly longer in patients with atraumatic posteroinferior multidirectional shoulder instability than in control subjects (P<0.001). The cross-sectional area under the supraspinatus tendon, and the rotator interval were significantly increased in patients with atraumatic posteroinferior multidirectional shoulder instability compared to control subjects (P<0.001 and P=0.01, respectively). Linear distance greater than 1.6 mm under the supraspinatus tendon had a specificity of 95% and a sensitivity of 90% for diagnosing atraumatic posteroinferior multidirectional shoulder instability. Cross-sectional area under the supraspinatus tendon greater than 0.3 cm(2), or an area under the rotator interval greater than 1.4 cm(2) had a specificity of more than 80% and a sensitivity of 90%.
CONCLUSION:
The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation.
Hsu YC, Shih YY, Gao HW,; Huang GS
Subcutaneous lipoma compressing the common peroneal nerve and causing palsy: sonographic diagnosisJournal of Clinical Ultrasound[Press release]PubMed
@article{YC2010b,
title = {Subcutaneous lipoma compressing the common peroneal nerve and causing palsy: sonographic diagnosis},
author = {Hsu YC, Shih YY, Gao HW, and Huang GS},
url = {https://pubmed.ncbi.nlm.nih.gov/19802890/},
doi = {10.1002/jcu.20643},
year = {2010},
date = {2010-02-01},
urldate = {2010-02-01},
journal = {Journal of Clinical Ultrasound},
volume = {38},
number = {2},
pages = {97-9},
abstract = {The compression of peripheral nerves by benign fatty tumors has rarely been reported in the literature. We present the case of a patient who had a subcutaneous lipoma in the region of the knee that caused common peroneal nerve palsy and appeared to compress the nerve on sonography. The surgical removal of subcutaneous lipoma allowed complete recovery.},
note = {case report},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The compression of peripheral nerves by benign fatty tumors has rarely been reported in the literature. We present the case of a patient who had a subcutaneous lipoma in the region of the knee that caused common peroneal nerve palsy and appeared to compress the nerve on sonography. The surgical removal of subcutaneous lipoma allowed complete recovery.
Huang GS, Lee HS, Chou MC, Shih YY, Tsai PH, Lin MH, Lin CY, Lee CH, Chung HW
Quantitative MR T2 measurement of articular cartilage to assess the treatment effect of intra-articular hyaluronic acid injection on experimental osteoarthritis induced by ACLXOsteoarthritis CartilagePubMed
@article{GS2010,
title = {Quantitative MR T2 measurement of articular cartilage to assess the treatment effect of intra-articular hyaluronic acid injection on experimental osteoarthritis induced by ACLX},
author = {Huang GS, Lee HS, Chou MC, Shih YY, Tsai PH, Lin MH, Lin CY, Lee CH, Chung HW},
url = {https://pubmed.ncbi.nlm.nih.gov/19761884/},
doi = {10.1016/j.joca.2009.08.014},
year = {2010},
date = {2010-01-01},
journal = {Osteoarthritis Cartilage},
volume = {18},
number = {1},
pages = {54-60},
abstract = {OBJECTIVE:
The purpose of this study was to investigate whether the effect of treatment with hyaluronic acid (HA) on cartilage in osteoarthritis (OA) can be determined by measuring the magnetic resonance (MR) T2 value of cartilage in an anterior cruciate ligament transection (ACLX) animal model.
METHOD:
Eighteen male Sprague Dawley rats were separated randomly into three groups (n=6 for each group). Group 1 was given ACLX and intra-articular (IA) normal saline (NS) injection (ACLX+NS), group 2 was given ACLX and IA HA injection (ACLX+HA), and group 3 was the sham control. The ACLX+NS and ACLX+HA groups received ACLX on the right knee at 8 weeks of age and were then treated with IA NS or HA injection once a week, respectively, for 4 weeks starting at 13 weeks of age. In the sham-control group, the right knee joint was opened surgically but ACLX was not performed at 8 weeks of age. MR T2 measurements were obtained on all rats at 8, 12, and 21 weeks of age, and histological Mankin scoring was performed at 21 weeks of age.
RESULTS:
Five weeks after the 4-week treatment, the MR T2 value of the ACLX right knee cartilage was significantly lower in ACLX+HA (29.58+/-1.12ms) than in ACLX+NS (32.04+/-1.39ms) (P<0.05). Five weeks after the 4-week treatment, the Mankin score of the ACLX right knee was significantly lower in ACLX+HA (3.3+/-0.81) than in ACLX+NS (7.3+/-1.03) (P<0.001). The T2 value was significantly and positively correlated with the Mankin score in the ACLX+NS (rho=0.77, P<0.05) and ACLX+HA (rho=0.69, P<0.05) groups.
CONCLUSION:
This study demonstrates the feasibility of quantitative MR T2 measurement in the early assessment of HA treatment efficiency in a cartilage degeneration model.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
OBJECTIVE:
The purpose of this study was to investigate whether the effect of treatment with hyaluronic acid (HA) on cartilage in osteoarthritis (OA) can be determined by measuring the magnetic resonance (MR) T2 value of cartilage in an anterior cruciate ligament transection (ACLX) animal model.
METHOD:
Eighteen male Sprague Dawley rats were separated randomly into three groups (n=6 for each group). Group 1 was given ACLX and intra-articular (IA) normal saline (NS) injection (ACLX+NS), group 2 was given ACLX and IA HA injection (ACLX+HA), and group 3 was the sham control. The ACLX+NS and ACLX+HA groups received ACLX on the right knee at 8 weeks of age and were then treated with IA NS or HA injection once a week, respectively, for 4 weeks starting at 13 weeks of age. In the sham-control group, the right knee joint was opened surgically but ACLX was not performed at 8 weeks of age. MR T2 measurements were obtained on all rats at 8, 12, and 21 weeks of age, and histological Mankin scoring was performed at 21 weeks of age.
RESULTS:
Five weeks after the 4-week treatment, the MR T2 value of the ACLX right knee cartilage was significantly lower in ACLX+HA (29.58+/-1.12ms) than in ACLX+NS (32.04+/-1.39ms) (P<0.05). Five weeks after the 4-week treatment, the Mankin score of the ACLX right knee was significantly lower in ACLX+HA (3.3+/-0.81) than in ACLX+NS (7.3+/-1.03) (P<0.001). The T2 value was significantly and positively correlated with the Mankin score in the ACLX+NS (rho=0.77, P<0.05) and ACLX+HA (rho=0.69, P<0.05) groups.
CONCLUSION:
This study demonstrates the feasibility of quantitative MR T2 measurement in the early assessment of HA treatment efficiency in a cartilage degeneration model.
The purpose of this study was to investigate whether the effect of treatment with hyaluronic acid (HA) on cartilage in osteoarthritis (OA) can be determined by measuring the magnetic resonance (MR) T2 value of cartilage in an anterior cruciate ligament transection (ACLX) animal model.
METHOD:
Eighteen male Sprague Dawley rats were separated randomly into three groups (n=6 for each group). Group 1 was given ACLX and intra-articular (IA) normal saline (NS) injection (ACLX+NS), group 2 was given ACLX and IA HA injection (ACLX+HA), and group 3 was the sham control. The ACLX+NS and ACLX+HA groups received ACLX on the right knee at 8 weeks of age and were then treated with IA NS or HA injection once a week, respectively, for 4 weeks starting at 13 weeks of age. In the sham-control group, the right knee joint was opened surgically but ACLX was not performed at 8 weeks of age. MR T2 measurements were obtained on all rats at 8, 12, and 21 weeks of age, and histological Mankin scoring was performed at 21 weeks of age.
RESULTS:
Five weeks after the 4-week treatment, the MR T2 value of the ACLX right knee cartilage was significantly lower in ACLX+HA (29.58+/-1.12ms) than in ACLX+NS (32.04+/-1.39ms) (P<0.05). Five weeks after the 4-week treatment, the Mankin score of the ACLX right knee was significantly lower in ACLX+HA (3.3+/-0.81) than in ACLX+NS (7.3+/-1.03) (P<0.001). The T2 value was significantly and positively correlated with the Mankin score in the ACLX+NS (rho=0.77, P<0.05) and ACLX+HA (rho=0.69, P<0.05) groups.
CONCLUSION:
This study demonstrates the feasibility of quantitative MR T2 measurement in the early assessment of HA treatment efficiency in a cartilage degeneration model.
2009
Shih YY, Chen CC, Shyu BC, Lin ZJ, Chiang YC, Jaw FS, Chen YY, Chang C
A new scenario for negative functional magnetic resonance imaging signals: endogenous neurotransmissionThe Journal of Neuroscience[Press release]PubMed
@article{YY2009,
title = {A new scenario for negative functional magnetic resonance imaging signals: endogenous neurotransmission},
author = {Shih YY, Chen CC, Shyu BC, Lin ZJ, Chiang YC, Jaw FS, Chen YY, Chang C},
url = {https://pubmed.ncbi.nlm.nih.gov/19279240/},
doi = {10.1523/JNEUROSCI.3447-08.2009},
year = {2009},
date = {2009-03-11},
urldate = {2009-03-11},
journal = {The Journal of Neuroscience},
volume = {29},
number = {10},
pages = {3036-44},
abstract = {Functional magnetic resonance imaging (fMRI) has revolutionized investigations of brain functions. Increases in fMRI signals are usually correlated with neuronal activation, but diverse explanations have been proposed for negative fMRI responses, including decreases in neuronal activity, the vascular-steal effect, and large increases in oxygen consumption. These possible scenarios, although encompassing a wide range of potential neurovascular responses, cannot yet be used to interpret certain types of negative fMRI signals. Recent studies have found that intravenous injection of dopamine D(2) receptor (D2DR) agonist reduced the hemodynamic responses in the caudate-putamen (CPu); however, whether endogenous dopaminergic neurotransmission contributes to fMRI signals remains obscure. Since it has been suggested that the D2DR is involved in pain modulation, and the CPu shows equivocal fMRI signals during noxious stimulation, the present study established an animal model based on graded electrical stimulation to elicit different levels of nociception, and aimed to determine whether nociception-induced endogenous dopaminergic neurotransmission is sufficient to generate negative fMRI responses. Our results from cerebral blood volume (CBV)-weighted fMRI, Fos immunohistochemistry, and electrophysiological recording demonstrated a salient bilateral CBV decreases associated with heightened neuronal activity in the CPu induced by unilateral noxious electrical stimulation. In addition, preinjection of D2DR antagonist reduced the observed CBV decreases. Our findings reveal the role of the D2DR in regulating striatal vascular responses and suggest that endogenous neurotransmission-induced CBV decreases underlie negative fMRI signals. Hence, the influence of endogenous neurotransmission should be considered when interpreting fMRI data, especially in an area involved in strong vasoactive neurotransmission.},
note = {See also “This Week in The Journal” in the J Neurosci, 2009 29(10):i and Research Highlight in the Nat Rev Neurosci, 2009 10(5):316.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Functional magnetic resonance imaging (fMRI) has revolutionized investigations of brain functions. Increases in fMRI signals are usually correlated with neuronal activation, but diverse explanations have been proposed for negative fMRI responses, including decreases in neuronal activity, the vascular-steal effect, and large increases in oxygen consumption. These possible scenarios, although encompassing a wide range of potential neurovascular responses, cannot yet be used to interpret certain types of negative fMRI signals. Recent studies have found that intravenous injection of dopamine D(2) receptor (D2DR) agonist reduced the hemodynamic responses in the caudate-putamen (CPu); however, whether endogenous dopaminergic neurotransmission contributes to fMRI signals remains obscure. Since it has been suggested that the D2DR is involved in pain modulation, and the CPu shows equivocal fMRI signals during noxious stimulation, the present study established an animal model based on graded electrical stimulation to elicit different levels of nociception, and aimed to determine whether nociception-induced endogenous dopaminergic neurotransmission is sufficient to generate negative fMRI responses. Our results from cerebral blood volume (CBV)-weighted fMRI, Fos immunohistochemistry, and electrophysiological recording demonstrated a salient bilateral CBV decreases associated with heightened neuronal activity in the CPu induced by unilateral noxious electrical stimulation. In addition, preinjection of D2DR antagonist reduced the observed CBV decreases. Our findings reveal the role of the D2DR in regulating striatal vascular responses and suggest that endogenous neurotransmission-induced CBV decreases underlie negative fMRI signals. Hence, the influence of endogenous neurotransmission should be considered when interpreting fMRI data, especially in an area involved in strong vasoactive neurotransmission.
Chen YY, Shih YY, Chien CN, Chou TW, Lee TW, Jaw FS
MicroPET study of brain neuronal metabolism under electrical and mechanical stimulation of the rat tailNuclear Medicine Communications[Press release]PubMed
@article{YY2009b,
title = {MicroPET study of brain neuronal metabolism under electrical and mechanical stimulation of the rat tail},
author = {Chen YY, Shih YY, Chien CN, Chou TW, Lee TW, Jaw FS},
url = {https://pubmed.ncbi.nlm.nih.gov/19262279/},
doi = {10.1097/MNM.0b013e32830c6a87},
year = {2009},
date = {2009-03-01},
urldate = {2009-03-01},
journal = {Nuclear Medicine Communications},
volume = {30},
number = {3},
pages = {188-193},
abstract = {OBJECTIVE:
Small-animal positron emission tomography (microPET) has been widely used for measuring various molecular processes in the rodent brain. The somatotopic projection, however, has not been identified earlier using microPET under electrical stimulation (ES) and mechanical stimulation (MS). This study aimed to utilize microPET to investigate the glucose metabolism of cortical and thalamic responses to ES and MS of the rat tail.
METHODS:
The rats were anesthetized by ketamine and a custom-built stereotaxic frame was used to fix the rat head to ensure that the scanned images were concordant with an atlas. [F]-fluorodeoxyglucose (FDG) was used as a radiotracer to reveal the brain metabolic changes. An activation index (AI) was calculated from microPET data o quantify the changes in local metabolic activities normalized to variations in FDG dosage between animals.
RESULTS:
The results showed that ES increased FDG uptake in both the contralateral thalamus (AI=18) and cortex (AI=12.5), with significant side-to-side differences (P<0.05, paired t-test). MS also significantly increased FDG uptake in both cortical and thalamic regions, although lateralization was absent in the thalamus.
CONCLUSION:
This study indicated that microPET can be used to elucidate the functional and quantitative neuronal activities of brain structures of rodents under peripheral stimulation, and could be applied in investigations of brain sensory functions.},
note = {Highlight of the issue},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
OBJECTIVE:
Small-animal positron emission tomography (microPET) has been widely used for measuring various molecular processes in the rodent brain. The somatotopic projection, however, has not been identified earlier using microPET under electrical stimulation (ES) and mechanical stimulation (MS). This study aimed to utilize microPET to investigate the glucose metabolism of cortical and thalamic responses to ES and MS of the rat tail.
METHODS:
The rats were anesthetized by ketamine and a custom-built stereotaxic frame was used to fix the rat head to ensure that the scanned images were concordant with an atlas. [F]-fluorodeoxyglucose (FDG) was used as a radiotracer to reveal the brain metabolic changes. An activation index (AI) was calculated from microPET data o quantify the changes in local metabolic activities normalized to variations in FDG dosage between animals.
RESULTS:
The results showed that ES increased FDG uptake in both the contralateral thalamus (AI=18) and cortex (AI=12.5), with significant side-to-side differences (P<0.05, paired t-test). MS also significantly increased FDG uptake in both cortical and thalamic regions, although lateralization was absent in the thalamus.
CONCLUSION:
This study indicated that microPET can be used to elucidate the functional and quantitative neuronal activities of brain structures of rodents under peripheral stimulation, and could be applied in investigations of brain sensory functions.
Small-animal positron emission tomography (microPET) has been widely used for measuring various molecular processes in the rodent brain. The somatotopic projection, however, has not been identified earlier using microPET under electrical stimulation (ES) and mechanical stimulation (MS). This study aimed to utilize microPET to investigate the glucose metabolism of cortical and thalamic responses to ES and MS of the rat tail.
METHODS:
The rats were anesthetized by ketamine and a custom-built stereotaxic frame was used to fix the rat head to ensure that the scanned images were concordant with an atlas. [F]-fluorodeoxyglucose (FDG) was used as a radiotracer to reveal the brain metabolic changes. An activation index (AI) was calculated from microPET data o quantify the changes in local metabolic activities normalized to variations in FDG dosage between animals.
RESULTS:
The results showed that ES increased FDG uptake in both the contralateral thalamus (AI=18) and cortex (AI=12.5), with significant side-to-side differences (P<0.05, paired t-test). MS also significantly increased FDG uptake in both cortical and thalamic regions, although lateralization was absent in the thalamus.
CONCLUSION:
This study indicated that microPET can be used to elucidate the functional and quantitative neuronal activities of brain structures of rodents under peripheral stimulation, and could be applied in investigations of brain sensory functions.
Chao WH, Chen YY, Lin SH, Shih YY, Tsang S
Automatic segmentation of magnetic resonance images using a decision tree with spatial informationComputerized Medical Imaging and GraphicsPubMed
@article{WH2009,
title = {Automatic segmentation of magnetic resonance images using a decision tree with spatial information},
author = {Chao WH, Chen YY, Lin SH, Shih YY, Tsang S},
url = {https://pubmed.ncbi.nlm.nih.gov/19097854/},
doi = {10.1016/j.compmedimag.2008.10.008},
year = {2009},
date = {2009-03-01},
urldate = {2009-03-01},
journal = {Computerized Medical Imaging and Graphics},
volume = {33},
number = {2},
pages = {111-21},
abstract = {Here we proposed an automatic segmentation method based on a decision tree to classify the brain tissues in magnetic resonance (MR) images. Two types of data - phantom MR images obtained from IBSR (http://www.cma.mgh.harvard.edu/ibsr) and simulated brain MR images obtained from BrainWeb (http://www.bic.mni.mcgill.ca/brainweb) - were segmented using an automatic decision tree algorithm to obtain images with improved visual rendition. Spatial information on the general gray level (G), spatial gray level (S), and two-dimensional wavelet transform (W) was combined in-plane in two coordinate systems (Euclidean coordinates (x, y) or polar coordinates (r, theta)). The decision tree was constructed based on a binary tree with nodes created by splitting the distribution of input features of the tree. The spatial information obtained from MR images with different noise levels and inhomogeneities were segmented to compare whether the use of a decision tree improved the identification of human anatomical structures in a neuroimage. The average accuracy rates of segmentation for phantom images with a noise variation of 15 gray levels were 0.9999 and 0.9973 with spatial information (G, x, y, r, theta) and (S, x, y, r, theta), respectively, and 0.9999 and 0.9819 with spatial information (G, x, y, S, r, theta) and (W, x, y, G, r, theta). The average accuracy rates of segmentation for simulated MR images with a noise level of 5% were 0.9532 and 0.9439 with spatial information (G, x, y, r, theta) and (S, x, y, r, theta), respectively, and 0.9446 and 0.9287 with spatial information (G, x, y, S, r, theta) and (W, x, y, G, r, theta). The accuracy rates of segmentation were highest for both simulated phantom and brain MR images, having the lowest noise levels, from a reduction of overlapping gray levels in the images. The accuracies of segmentation were higher when the spatial information included the general gray level than when it included the spatial gray level, which in turn were higher than when it included the wavelet transform. Furthermore, the performance of segmentation was also evaluated with a boundary detection methodology that is based on the Hausdorff distance to compare with the mean computer to observer difference (COD) and mean interobserver difference (IOD) for gray matter (GM), white matter (WM), and all areas (ALL) from images segmented using the decision tree. The values of mean COD are similar and around 12mm for GM segmented using the decision tree. Our segmentation method based on a decision tree algorithm presented an easy way to perform automatic segmentation for both phantom and tissue regions in brain MR images.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Here we proposed an automatic segmentation method based on a decision tree to classify the brain tissues in magnetic resonance (MR) images. Two types of data - phantom MR images obtained from IBSR (http://www.cma.mgh.harvard.edu/ibsr) and simulated brain MR images obtained from BrainWeb (http://www.bic.mni.mcgill.ca/brainweb) - were segmented using an automatic decision tree algorithm to obtain images with improved visual rendition. Spatial information on the general gray level (G), spatial gray level (S), and two-dimensional wavelet transform (W) was combined in-plane in two coordinate systems (Euclidean coordinates (x, y) or polar coordinates (r, theta)). The decision tree was constructed based on a binary tree with nodes created by splitting the distribution of input features of the tree. The spatial information obtained from MR images with different noise levels and inhomogeneities were segmented to compare whether the use of a decision tree improved the identification of human anatomical structures in a neuroimage. The average accuracy rates of segmentation for phantom images with a noise variation of 15 gray levels were 0.9999 and 0.9973 with spatial information (G, x, y, r, theta) and (S, x, y, r, theta), respectively, and 0.9999 and 0.9819 with spatial information (G, x, y, S, r, theta) and (W, x, y, G, r, theta). The average accuracy rates of segmentation for simulated MR images with a noise level of 5% were 0.9532 and 0.9439 with spatial information (G, x, y, r, theta) and (S, x, y, r, theta), respectively, and 0.9446 and 0.9287 with spatial information (G, x, y, S, r, theta) and (W, x, y, G, r, theta). The accuracy rates of segmentation were highest for both simulated phantom and brain MR images, having the lowest noise levels, from a reduction of overlapping gray levels in the images. The accuracies of segmentation were higher when the spatial information included the general gray level than when it included the spatial gray level, which in turn were higher than when it included the wavelet transform. Furthermore, the performance of segmentation was also evaluated with a boundary detection methodology that is based on the Hausdorff distance to compare with the mean computer to observer difference (COD) and mean interobserver difference (IOD) for gray matter (GM), white matter (WM), and all areas (ALL) from images segmented using the decision tree. The values of mean COD are similar and around 12mm for GM segmented using the decision tree. Our segmentation method based on a decision tree algorithm presented an easy way to perform automatic segmentation for both phantom and tissue regions in brain MR images.
2008
Chao WH, Chen YY, Cho CW, Lin SH, Shih YY, Tsang S
Improving segmentation accuracy for magnetic resonance imaging using a boosted decision treeJournal of Neuroscience MethodsPubMed
@article{WH2008,
title = {Improving segmentation accuracy for magnetic resonance imaging using a boosted decision tree},
author = {Chao WH, Chen YY, Cho CW, Lin SH, Shih YY, Tsang S},
url = {https://pubmed.ncbi.nlm.nih.gov/18786567/},
doi = {10.1016/j.jneumeth.2008.08.017},
year = {2008},
date = {2008-11-15},
urldate = {2008-11-15},
journal = {Journal of Neuroscience Methods},
volume = {175},
number = {2},
pages = {206-17},
abstract = {The purpose of this study was to improve the accuracy rate of brain tissue classification in magnetic resonance (MR) imaging using a boosted decision tree segmentation algorithm. Herein, we examined simulated phantom MR (SPMR) images, simulated brain MR (SBMR) images, and a real data. The accuracy rate and k index when classifying brain tissues as gray matter (GM), white matter (WM), or cerebral-spinal fluid (CSF) were better when using the boosted decision tree algorithm combined with a fuzzy threshold than when using a statistical region-growing (SRG) algorithm [Wolf I, Vetter M, Wegner I, Böttger T, Nolden M, Schöbinger M, et al. The medical imaging interaction toolkit. Med Imag Anal 2005;9:594-604] and an adaptive segmentation (AS) algorithm [Wells WM, Grimson WEL, Kikinis R, Jolesz FA. Adaptive segmentation of MRI data. IEEE Trans Med Imag 1996;15:429-42]. The segmentation performance when using this algorithm on real data from brain MR images was also better than those of SRG and AS algorithm. Segmentation of a real data using the boosted decision tree produced particularly clear brain MR imaging and permitted more accurate brain tissue segmentation. In conclusion, a decision tree with appropriate boost trials successfully improved the accuracy rate of MR brain tissue segmentation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The purpose of this study was to improve the accuracy rate of brain tissue classification in magnetic resonance (MR) imaging using a boosted decision tree segmentation algorithm. Herein, we examined simulated phantom MR (SPMR) images, simulated brain MR (SBMR) images, and a real data. The accuracy rate and k index when classifying brain tissues as gray matter (GM), white matter (WM), or cerebral-spinal fluid (CSF) were better when using the boosted decision tree algorithm combined with a fuzzy threshold than when using a statistical region-growing (SRG) algorithm [Wolf I, Vetter M, Wegner I, Böttger T, Nolden M, Schöbinger M, et al. The medical imaging interaction toolkit. Med Imag Anal 2005;9:594-604] and an adaptive segmentation (AS) algorithm [Wells WM, Grimson WEL, Kikinis R, Jolesz FA. Adaptive segmentation of MRI data. IEEE Trans Med Imag 1996;15:429-42]. The segmentation performance when using this algorithm on real data from brain MR images was also better than those of SRG and AS algorithm. Segmentation of a real data using the boosted decision tree produced particularly clear brain MR imaging and permitted more accurate brain tissue segmentation. In conclusion, a decision tree with appropriate boost trials successfully improved the accuracy rate of MR brain tissue segmentation.
Shih YY, Chang C, Chen JC, Jaw FS
BOLD fMRI mapping of brain responses to nociceptive stimuli in rats under ketamine anesthesiaMedical Engineering & PhysicsPubMed
@article{YY2008,
title = {BOLD fMRI mapping of brain responses to nociceptive stimuli in rats under ketamine anesthesia},
author = {Shih YY, Chang C, Chen JC, Jaw FS},
url = {https://pubmed.ncbi.nlm.nih.gov/18243035/},
doi = {10.1016/j.medengphy.2007.12.004},
year = {2008},
date = {2008-10-01},
urldate = {2008-10-01},
journal = {Medical Engineering & Physics},
volume = {30},
number = {8},
pages = {953-8},
abstract = {Ketamine is one of the most commonly used anesthetics, but its effects on nociceptive responses are not clearly defined. This study used blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to hemodynamically map responses to formalin stimuli under ketamine anesthesia. All imaging was performed on a 4.7-T fMRI system. During dynamic image acquisition, formalin was injected into the rat hindpaw as a painful stimulant. Correlation coefficients were calculated, and each image was registered and fused with the corresponding rat brain atlas so as to avoid inaccuracies arising from manual definition of the brain area and to achieve atlas-based normalization among subjects. Formalin injections were found to increase BOLD signals in the cingulate cortex, sensory-motor cortices, insular cortex, striatum, nucleus accumbens, medial thalamus, ventrolateral thalamic group, and hippocampus. Moreover, in contrast to previous pain investigations, the frontal subcortical regions were strongly activated in ketamine-anesthetized rats.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ketamine is one of the most commonly used anesthetics, but its effects on nociceptive responses are not clearly defined. This study used blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to hemodynamically map responses to formalin stimuli under ketamine anesthesia. All imaging was performed on a 4.7-T fMRI system. During dynamic image acquisition, formalin was injected into the rat hindpaw as a painful stimulant. Correlation coefficients were calculated, and each image was registered and fused with the corresponding rat brain atlas so as to avoid inaccuracies arising from manual definition of the brain area and to achieve atlas-based normalization among subjects. Formalin injections were found to increase BOLD signals in the cingulate cortex, sensory-motor cortices, insular cortex, striatum, nucleus accumbens, medial thalamus, ventrolateral thalamic group, and hippocampus. Moreover, in contrast to previous pain investigations, the frontal subcortical regions were strongly activated in ketamine-anesthetized rats.
Lee CY, Shih YY, Jaw FS
How to extract the spatial correlation of auditory cortical evoked potentials on multiple scalp electrodes in tinnitus patientsBiomedical Engineering: Applications, Basis and Communications
@article{CY2008,
title = {How to extract the spatial correlation of auditory cortical evoked potentials on multiple scalp electrodes in tinnitus patients},
author = {Lee CY, Shih YY, Jaw FS},
doi = {10.4015/S101623720800091X},
year = {2008},
date = {2008-10-01},
urldate = {2008-10-01},
journal = {Biomedical Engineering: Applications, Basis and Communications},
volume = {20},
number = {5},
pages = {297-302},
abstract = {Tinnitus affects 10–15% of the population and tends to increase in frequency among older ages. The published reports have converged on that tinnitus is the sustained neuroplastic changes with aberrant activity residing in the auditory and nonauditory nervous systems that cause the sensation and problem of tinnitus. Clinically tinnitus remains as a subjective symptom and cannot be evaluated objectively. Our previous study has demonstrated the significantly different intensity dependence of auditory cortical evoked potential (ACEP) amplitudes to pure-tone stimuli recorded at some midline scalp electrodes between normal controls and tinnitus patients. Although ACEP test has been well known for its excellent temporal resolution of milliseconds and the latency and amplitude of ACEPs give ample information about the auditory processing of tinnitus, these measurements at each electrode deliver insufficient information about the spatial correlation among different cortical locations. According to the neurophysiological model of tinnitus, temporal and spatial information are both necessary and complementary to study the underlying mechanisms of problem tinnitus. Thus the purpose of this study was to demonstrate the spatial presentations of ACEP N1–P2 of normal controls and tinnitus patients. In this work, a program has been developed to translate the ACEPs recorded at 30 scalp electrodes to a two-dimensional presentation of isoelectric topography and current source density. The differences of intensity dependence about N1–P2 noted with previous study are reviewed on the two spatial presentations and compared between control subjects and tinnitus patients, while the patterns of correlation are demonstrated and compared with those recorded by functional brain imaging techniques like PET and fMRI.
Read More: http://www.worldscientific.com/doi/abs/10.4015/S101623720800091X},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Tinnitus affects 10–15% of the population and tends to increase in frequency among older ages. The published reports have converged on that tinnitus is the sustained neuroplastic changes with aberrant activity residing in the auditory and nonauditory nervous systems that cause the sensation and problem of tinnitus. Clinically tinnitus remains as a subjective symptom and cannot be evaluated objectively. Our previous study has demonstrated the significantly different intensity dependence of auditory cortical evoked potential (ACEP) amplitudes to pure-tone stimuli recorded at some midline scalp electrodes between normal controls and tinnitus patients. Although ACEP test has been well known for its excellent temporal resolution of milliseconds and the latency and amplitude of ACEPs give ample information about the auditory processing of tinnitus, these measurements at each electrode deliver insufficient information about the spatial correlation among different cortical locations. According to the neurophysiological model of tinnitus, temporal and spatial information are both necessary and complementary to study the underlying mechanisms of problem tinnitus. Thus the purpose of this study was to demonstrate the spatial presentations of ACEP N1–P2 of normal controls and tinnitus patients. In this work, a program has been developed to translate the ACEPs recorded at 30 scalp electrodes to a two-dimensional presentation of isoelectric topography and current source density. The differences of intensity dependence about N1–P2 noted with previous study are reviewed on the two spatial presentations and compared between control subjects and tinnitus patients, while the patterns of correlation are demonstrated and compared with those recorded by functional brain imaging techniques like PET and fMRI.
Read More: http://www.worldscientific.com/doi/abs/10.4015/S101623720800091X
Read More: http://www.worldscientific.com/doi/abs/10.4015/S101623720800091X
Shih YY, Chiang YC, Chen JC, Huang CH, Chen YY, Liu RS, Chang C, Jaw FS
Brain nociceptive imaging in rats using 18f-fluorodeoxyglucose small-animal positron emission tomography@article{YY2008b,
title = {Brain nociceptive imaging in rats using 18f-fluorodeoxyglucose small-animal positron emission tomography},
author = {Shih YY, Chiang YC, Chen JC, Huang CH, Chen YY, Liu RS, Chang C, Jaw FS},
url = {https://pubmed.ncbi.nlm.nih.gov/18675887/},
doi = {10.1016/j.neuroscience.2008.07.013},
year = {2008},
date = {2008-09-09},
journal = {Neuroscience},
volume = {155},
number = {4},
pages = {1221-6},
abstract = {Preclinical exploration of pain processing in the brain as well as evaluating pain-relief drugs in small animals embodies the potential biophysical effects in humans. However, it is difficult to measure nociception-related cerebral metabolic changes in vivo, especially in unanesthetized animals. The present study used 18F-fluorodeoxyglucose small-animal positron emission tomography to produce cerebral metabolic maps associated with formalin-induced nociception. Anesthesia was not applied during the uptake period so as to reduce possible confounding effects on pain processing in the brain. The formalin stimulation at the hind paw of rats resulted in significant metabolic increases in the bilateral cingulate cortex, motor cortex, primary somatosensory cortex, secondary somatosensory cortex, insular cortex, visual cortex, caudate putamen, hippocampus, periaqueductal gray, amygdala, thalamus, and hypothalamus. Among the measured areas, clear lateralization was only evident in the primary somatosensory cortex and hypothalamus. In addition, pretreatment with lidocaine (4 mg/kg, i.v.) and morphine (10 mg/kg, i.v.) significantly suppressed formalin-induced cerebral metabolic increases in these areas. The present protocol allowed identification of the brain areas involved in pain processing, and should be useful in further evaluations of the effects of new drugs and preclinical therapies for pain.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Preclinical exploration of pain processing in the brain as well as evaluating pain-relief drugs in small animals embodies the potential biophysical effects in humans. However, it is difficult to measure nociception-related cerebral metabolic changes in vivo, especially in unanesthetized animals. The present study used 18F-fluorodeoxyglucose small-animal positron emission tomography to produce cerebral metabolic maps associated with formalin-induced nociception. Anesthesia was not applied during the uptake period so as to reduce possible confounding effects on pain processing in the brain. The formalin stimulation at the hind paw of rats resulted in significant metabolic increases in the bilateral cingulate cortex, motor cortex, primary somatosensory cortex, secondary somatosensory cortex, insular cortex, visual cortex, caudate putamen, hippocampus, periaqueductal gray, amygdala, thalamus, and hypothalamus. Among the measured areas, clear lateralization was only evident in the primary somatosensory cortex and hypothalamus. In addition, pretreatment with lidocaine (4 mg/kg, i.v.) and morphine (10 mg/kg, i.v.) significantly suppressed formalin-induced cerebral metabolic increases in these areas. The present protocol allowed identification of the brain areas involved in pain processing, and should be useful in further evaluations of the effects of new drugs and preclinical therapies for pain.
Shih YY, Chen YY, Chen CC, Chen JC, Chang C, Jaw FS
Whole-brain functional magnetic resonance imaging mapping of acute nociceptive responses induced by formalin in rats using atlas registration-based event-related analysisThe Journal of NeurosciencePubMed
@article{YY2008b,
title = {Whole-brain functional magnetic resonance imaging mapping of acute nociceptive responses induced by formalin in rats using atlas registration-based event-related analysis},
author = {Shih YY, Chen YY, Chen CC, Chen JC, Chang C, Jaw FS},
url = {https://pubmed.ncbi.nlm.nih.gov/18293420/},
doi = {10.1002/jnr.21638},
year = {2008},
date = {2008-06-01},
urldate = {2008-06-01},
journal = {The Journal of Neuroscience},
volume = {86},
number = {8},
pages = {1801-11},
abstract = {Nociceptive neuronal activation in subcortical regions has not been well investigated in functional magnetic resonance imaging (fMRI) studies. The present report aimed to use the blood oxygenation level-dependent (BOLD) fMRI technique to map nociceptive responses in both subcortical and cortical regions by employing a refined data processing method, the atlas registration-based event-related (ARBER) analysis technique. During fMRI acquisition, 5% formalin (50 mul) was injected into the left hindpaw to induce nociception. ARBER was then used to normalize the data among rats, and images were analyzed using automatic selection of the atlas-based region of interest. It was found that formalin-induced nociceptive processing increased BOLD signals in both cortical and subcortical regions. The cortical activation was distributed over the cingulate, motor, somatosensory, insular, and visual cortices, and the subcortical activation involved the caudate putamen, hippocampus, periaqueductal gray, superior colliculus, thalamus, and hypothalamus. With the aid of ARBER, the present study revealed a detailed activation pattern that possibly indicated the recruitment of various parts of the nociceptive system. The results also demonstrated the utilization of ARBER in establishing an fMRI-based whole-brain nociceptive map. The formalin induced nociceptive images may serve as a template of central nociceptive responses, which can facilitate the future use of fMRI in evaluation of new drugs and preclinical therapies for pain.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nociceptive neuronal activation in subcortical regions has not been well investigated in functional magnetic resonance imaging (fMRI) studies. The present report aimed to use the blood oxygenation level-dependent (BOLD) fMRI technique to map nociceptive responses in both subcortical and cortical regions by employing a refined data processing method, the atlas registration-based event-related (ARBER) analysis technique. During fMRI acquisition, 5% formalin (50 mul) was injected into the left hindpaw to induce nociception. ARBER was then used to normalize the data among rats, and images were analyzed using automatic selection of the atlas-based region of interest. It was found that formalin-induced nociceptive processing increased BOLD signals in both cortical and subcortical regions. The cortical activation was distributed over the cingulate, motor, somatosensory, insular, and visual cortices, and the subcortical activation involved the caudate putamen, hippocampus, periaqueductal gray, superior colliculus, thalamus, and hypothalamus. With the aid of ARBER, the present study revealed a detailed activation pattern that possibly indicated the recruitment of various parts of the nociceptive system. The results also demonstrated the utilization of ARBER in establishing an fMRI-based whole-brain nociceptive map. The formalin induced nociceptive images may serve as a template of central nociceptive responses, which can facilitate the future use of fMRI in evaluation of new drugs and preclinical therapies for pain.
Chen CM, Shih YY, Siow TY, Chiang YC, Chang C, Jaw FS
Antinociceptive effect of morphine in α-chloralose and isoflurane anesthetized rats using BOLD fMRIBiomedical Engineering: Applications, Basis and Communications
@article{CM2008,
title = {Antinociceptive effect of morphine in α-chloralose and isoflurane anesthetized rats using BOLD fMRI},
author = {Chen CM, Shih YY, Siow TY, Chiang YC, Chang C, Jaw FS},
doi = {10.4015/S1016237208000581},
year = {2008},
date = {2008-02-01},
urldate = {2008-02-01},
journal = {Biomedical Engineering: Applications, Basis and Communications},
volume = {20},
number = {1},
pages = {39-46},
abstract = {Blood oxygenation level dependent functional magnetic resonance imaging technique was used to explore the antinociceptive effect of morphine in the rat brain under α-chloralose and isoflurane anesthesia. Formalin was used as a pain-testing model which could produce significant activation in various brain areas. The results also showed that morphine pretreatment modulate neurovascular activities evoked by formalin stimulation, especially in cingulate cortex, somatosensory cortex, caudate putamen, visual cortex, and hippocampus. The present study identified the brain areas involved in modulating nociception.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Blood oxygenation level dependent functional magnetic resonance imaging technique was used to explore the antinociceptive effect of morphine in the rat brain under α-chloralose and isoflurane anesthesia. Formalin was used as a pain-testing model which could produce significant activation in various brain areas. The results also showed that morphine pretreatment modulate neurovascular activities evoked by formalin stimulation, especially in cingulate cortex, somatosensory cortex, caudate putamen, visual cortex, and hippocampus. The present study identified the brain areas involved in modulating nociception.
2007
Shih YY, Chen YY, Chen JC, Chang C,; Jaw FS
ISPMER: integrated system for combined PET, MRI, and electrophysiological recording in somatosensory studies in ratsNuclear Instruments and Methods in Physics Research Section A
@article{YY2007,
title = {ISPMER: integrated system for combined PET, MRI, and electrophysiological recording in somatosensory studies in rats},
author = {Shih YY, Chen YY, Chen JC, Chang C, and Jaw FS},
doi = {10.1016/j.nima.2007.06.062},
year = {2007},
date = {2007-10-01},
urldate = {2007-10-01},
journal = {Nuclear Instruments and Methods in Physics Research Section A},
volume = {580},
number = {2},
pages = {938-943},
abstract = {The present study developed an integrated system for use in combined PET, MRI, and electrophysiological recording in somatosensory studies in rats, called ISPMER. A stereotaxic frame was designed for animal positioning that could be used in all three measurement modalities, and its dimensions complied with the gold standard of the Paxinos and Watson rat brain atlas. A graphical user interface was developed for analyzing the data using several signal processing algorithms. This integrated system provides a novel interface for the recording and processing of three-dimensional neuronal signals in three modalities.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The present study developed an integrated system for use in combined PET, MRI, and electrophysiological recording in somatosensory studies in rats, called ISPMER. A stereotaxic frame was designed for animal positioning that could be used in all three measurement modalities, and its dimensions complied with the gold standard of the Paxinos and Watson rat brain atlas. A graphical user interface was developed for analyzing the data using several signal processing algorithms. This integrated system provides a novel interface for the recording and processing of three-dimensional neuronal signals in three modalities.