Name: MRI Scanner Setup for Human Visual Functional Imaging
Uploaded: 2023-12-08T12:40:00
Description: Watch this Scientific Journal Video about MRI Scanner Setup for Human Visual Functional Imaging at JoVE.com

mri scanner setup for human visual functional imaging

Faire progresser la cartographie du cortex visuel pour une meilleure évaluation des troubles de la vision

Functional magnetic resonance imaging (fMRI) is a valuable method to assess changes in regional neurovascular function within the visual cortex in response to stimuli, as changes in regional blood flow correlate to the activation of brain regions1,2. High-resolution retinotopic blood oxygenation level-dependent (BOLD) signal measurements represent changes in deoxyhemoglobin, which are driven by localized changes in blood flow and blood oxygenation within the brain1,2. BOLD activity patterns collected from fMRI data can be used to functionally map the peripheral and central visual cortex, as well as detect changes in the retinotopic map in response to visual impairment and neurodegeneration3.
Most previous fMRI studies made use of narrow-view (around &#177;12&#176; of the central visual field) non-retinotopic stimuli or simple retinotopic stimuli with narrow-view visual stimuli, which provided limited functional parcellation of the retinotopic representation in the visual cortex and limited assessment to only the central visual field, excluding the periphery3. Consequently, narrow-view fMRI data has reported inconsistent BOLD percent changes in glaucoma patients4,5,6. There is therefore a need for improved fMRI approaches to assessing the peripheral and central visual field, particularly in the evaluation of diseases such as glaucoma.
Glaucoma is the leading cause of irreversible blindness, affecting 10% of people by the age of 807. Glaucoma is caused by the progressive, irreversible neurodegeneration of retinal ganglion cells, which are responsible for transmitting visual stimuli to the brain through the optic nerve. In primary open-angle glaucoma (POAG), the most common form of glaucoma, increased intraocular pressure causes thinning of the retinal nerve fiber layer (RNFL), leading to the loss of peripheral vision followed by peripheral and central blindess8,9,10,11. Histological evidence from animal studies suggests that glaucoma additionally results in progressive neurodegeneration of the optic nerve, optic tract, lateral geniculate nucleus, optic radiation, and visual cortex12,13. MRI technology offers a minimally invasive method of assessing both blood oxygenation and neurodegeneration in the visual cortex. In patients with glaucoma, MRI has found evidence of gray-matter atrophy in the visual pathway13,14,15,16 and abnormal white matter in the optic chiasm, optic tract, and optic radiation1,17,18.
To further explore the effects on visual processing, fMRI can be used to detect brain function in response to visual cues. The protocol herein describes a novel method to obtain a low-cost, wide-view retinotopic map using high-resolution retinotopy fMRI with wide-field (&#62;100&#176;) stimuli, as described by Zhou et al3. Visual stimuli of expanding rings and rotating wedges were used to elicit retinotopic mapping of the eccentricity and polar angle for fMRI. BOLD fMRI percent changes were analyzed as a function of eccentricity to evaluate brain function, corresponding to both central and peripheral vision. The BOLD fMRI percent change may be used to visualize activation throughout the visual cortex. These fMRI measures provide a reliable new method to evaluate neurodegenerative changes and their functional effects on the visual cortex found in eye diseases involving visual field defects, such as glaucoma.

Pleins feux sur l’auteur : Aperçu de la recherche sur le cortex visuel grâce à la cartographie IRMf à grande échelle 

Imagerie par résonance magnétique fonctionnelle (IRMf) du cortex visuel avec stimulation rétinotopique à grand angle

This research focuses on providing a practical, cost-effective visual presentation system to evaluate changes in the visual cortex due to ophthalmic diseases. We provide a method to create a wide viewing angle, retina atopic map, using FMRI to assess the functional activity of the visual cortex. A current experimental challenge is that standard systems for presenting visual stimuli for FMRI only cover small area of the visual fields, and with the view partially obstructed by the head coil.This protocol provides method for wide view and unobstructed stimuli that balances cost, efficacy, and precision. Our protocol provides an affordable, moderately wide view of up to a hundred degrees of the visual field. Compared to other techniques, it avoids distortions, additional costs for projector lenses or fiber optic bundles, and other complexities, such as the need for contact lenses.Our findings can be used to expand the understanding of the visual cortex, enabling the mapping of peripheral and central regions via an affordable, wide view FMRI system. This could enhance the management of visual impairments in eye diseases such as glaucoma, which involves dysfunction of the visual system in the brain.

Watch this Scientific Journal Video about MRI Scanner Setup for Human Visual Functional Imaging at JoVE.com

MRI Scanner Setup for Human Visual Functional Imaging  

Configuration du scanner IRM pour l’imagerie fonctionnelle visuelle humaine

Commencez par utiliser un scanner IRM 3T équipé de bobines de tête de récepteur multicanaux pour l’imagerie par résonance magnétique fonctionnelle. Utilisez la moitié postérieure pour assurer un angle de vision plus grand sans obstruction. Ensuite, configurez une séquence MPRAGE pondérée T1 en saisissant un temps de répétition de 2,2 secondes et un champ de vision de 176 x 256 x 208 millimètres.Fournir une résolution spatiale de 1 x 1 x 1 millimètre. Bande passante de 190 hertz par pixel. Angle de retournement de 13 degrés.Et une durée de scan de 3,1 minutes. Configurez une séquence EPI d’écho de gradient avec un temps de répétition de 2 secondes, un temps d’écho de 30 millisecondes, un champ de vision de 220 par 220 millimètres, une résolution dans le plan de 1,7 par 1,7 millimètres avec 29 tranches de 3 millimètres d’épaisseur et une bande passante d’environ 1500 hertz par pixel. Maintenant, mesurez les dimensions de la bobine de tête et de l’alésage du scanner.Ensuite, connectez les tubes en PVC avec des coudes en PVC pour construire un cadre de tuyau en PVC simple, et avec des vis en nylon, fixez les extrémités de la tige en plastique qui maintient le miroir au cadre. Notez que le miroir est fixé à la tige en plastique avec des vis en plastique. Assurez-vous que les vis sont suffisamment desserrées pour que le miroir puisse être tourné manuellement à un angle optimal.Après avoir vissé un écran de rétroprojection segmenté sur un cadre, placez l’écran à l’arrière du scanner, en le positionnant derrière la bobine de tête pour maximiser le champ de vision.

Research

JoVE Journal

Neuroscience

MRI Scanner Setup for Human Visual Functional Imaging

Functional Magnetic Resonance Imaging (fMRI) of the Visual Cortex with Wide-View Retinotopic Stimulation

High-resolution retinotopic blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) with a wide-view presentation can be ...