Functional MRI of visual responses in the late stage of neonatal hypoxic-ischemic encephalopathy

Animal Models of Ischemia: Characterization - Poster presentationThis study employs blood oxygenation level-dependent functional MRI to evaluate the visual responses in the rat superior colliculi 2 months after neonatal hypoxic-ischemic encephalopathy. Results showed a smaller BOLD signal amplitude increase in the contralateral superior colliculus of the HIE group in the stimulation period than in the normal group upon either side of eye stimulation. Our results constitute the first fMRI report in evaluating the visual responses of the rat superior colliculus upon neonatal HI insults. These can be potentially useful in establishing the links between the changes related to the visual sensory development after neonatal injury.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 327

Late manganese-enhanced MRI of rat cortical and subcortical structures

Manganese Enhanced MRI - Poster presentationThis study employs in vivo manganese-enhanced MRI (MEMRI) before, and at 1, 5 and 12 days after systemic Mn administration to investigate the late enhancement of rat brain tissues before global clearance of Mn from the brain. While most brain structures were found maximally enhanced in T1WI at 1 day after Mn injection, a higher signal increase was observed at Day 5 in the central amygdaloid nucleus, globus pallidus, ventral pallidum, caudate putamen and thalamus compared to other time points. Our results suggested the deposition of Mn in areas of high astrocyte densities at 1 day after systemic Mn administration, with continuous redistribution of Mn through axonal transport in the late phase before its global clearance from the brain at Day 12.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 128

1H MRS of the visual cortex under chronic ocular hypertension

Session 36: Neurochemical Modeling & Profiling of Brain Metabolism - Oral presentationThis study aims to employ in vivo 1H MRS to monitor the metabolic changes in the visual cortex in an experimental model of chronic glaucoma. Five Sprague-Dawley rats were prepared to induce ocular hypertension unilaterally in the right eye by photocoagulating the episcleral and limbal veins using an argon laser. 1H MRS was performed to each side of the visual cortex 6 weeks after laser treatment. The results of this study suggest that glaucoma is associated with alterations in the metabolism of choline-containing compounds in the normally-appearing visual cortex. Measurement of the Cho:Cr reduction in the visual cortex may be a noninvasive biomarker for the disease.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 34

Gd-DTPA enhanced MRI revealed leakage at aqueous-vitreous interface upon ocular hypertension

Session 75: Perfusion & Diffusion: Animal Models - Oral presentationThis study aims to employ in vivo contrast-enhanced MRI to evaluate the ocular transport upon an induction of ocular hypertension in the right eye in a rat model of chronic glaucoma. Following systemic administration of Gd-DTPA solution, our results showed a progressive T1-weighted signal increase in the anterior vitreous body of the glaucomatous eye but not the control eye, suggestive of the leakage of Gd-DTPA at the aqueous-vitreous interface. These findings may explain the sources of changing biochemical compositions in the glaucomatous chamber components, which may implicate the cascades of neurodegenerative processes in the retina and the optic nerve. Our findings of the early Gd-DTPA signal enhancements in the anterior vitreous body than the preretinal vitreous provided a noninvasive marker for the disease. More importantly, this approach could have direct clinical applications and can be readily translated to humans.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 74

Characterization of white matter reorganization in neonatal hypoxic-ischemic cerebral injury using diffusion tensor imaging

Animal Models of Ischemia: Characterization - Poster presentationThis study employs in vivo diffusion tensor imaging (DTI) to understand the late changes in white matter (WM) injury and reorganization in the rat brain upon neonatal hypoxic-ischemic cerebral injury. In particular, detailed inspection of the color-encoded fractional anisotropy (FA) map of the principal eigenvector was performed to compare the orientations of the high FA fibers at the perilesional areas with the WM microstructures in the contralateral hemisphere. In addition to the differences in DTI parameters in the microstructures between both hemispheres, results showed that the perilesional areas had similar fiber orientations as the contralateral external capsule in the anterior section of the brain, and as the internal capsule and the fimbria of hippocampus in the posterior section. We demonstrated that DTI can detect the microstructure and orientations of WM fiber changes at the perilesional areas in vivo, and can be used for non-invasive evaluation of HI brain injuries and reorganization.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 327

Functional MRI of visual development in rat superior colliculus

fMRI Applications & Animal Models - Poster presentationThis study aimed to use visual stimulation in rats to determine age-related visual development from the time of eyelid opening to adulthood. By studying BOLD-fMRI measurements of rat superior colliculus, we demonstrated that the regional BOLD visual response in these animals undergoes a systematic increase in amplitude with age especially during the 3rd postnatal week.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 371

Spin-echo BOLD temporal dynamics in the rat superior colliculus and lateral geniculate nucleus

Session - fMRI Neuroscience Methods & Applications I: Computer 57 (Wednesday)INTRODUCTION: The superior colliculus (SC) and lateral geniculate nucleus (LGN) are important subcortical components of the visual system[1]. The majority of fMRI studies to date focus on higher visual processing centers in the cortex. fMRI studies in rats have examined visual responses in the subcortex using long stimulus duration block-design paradigms[2-4]. These studies focused on locating responsive regions and measuring differences in BOLD responses for different stimulation frequencies. Relatively little attention has been given to BOLD temporal dynamics in the rat subcortex. In this study, we apply …published_or_final_versionThe 19th Annual Meeting and Exhibition of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), Montreal, QC., 7-13 May 2011.In Proceedings of the 19th ISMRM, 2011, v. 19, p. 365

MEMRI study neonatal hypoxic-ischemic injury in the late stage

Session 16: Manganese Enhanced MRI: Methods & Applications - Oral presentationIn this study, in vivo MEMRI was employed to investigate the hypoxic-ischemic injury in the late phase. Mn2+ induced signal changes were examined using SPM coregistration and ROI analysis. T1WIs SI increase was detected in the perilesional region 24 hours after Mn2+ administration and it colocalized with the increase in glial cell density in GFAP staining, demonstrating the existence of reactive gliosis in the late phase after H-I injury.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 15

Taurine change in visual cortex of neonatal monocular enucleated rat: a proton MRS study

Posters - MRS of Animal Brain: 4530Neonatal monocular enucleation has been used to study developmental mechanisms underlying visual perception and the cross-modal changes in the central nervous system caused by early loss of the visual input. In this study, we demonstrated that alteration in the metabolism of taurine in visual cortex accompanied with neonatal monocular enucleation could be monitored using 1H MRS at 7 T. The change in taurine signal with respect to creatine signal may possibly due to the increased taurine signal in the right control visual cortex, likely caused by the plasticity resulted from recruitment of resources to the remaining left eye for adaptation.postprin

The study of a single injection of intravitreal triamcinolone acetonide in silicone oil filled eye using MRI

Poster Presentations - Session 3: anstract no. PS3-4postprin