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

Mapeamento avançado do córtex visual para avaliação aprimorada de distúrbios da visão

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.

Autor em destaque: Insights sobre a pesquisa do córtex visual por meio do mapeamento de fMRI de visão ampla 

Ressonância Magnética Funcional (RMf) do Córtex Visual com Estimulação Retinotópica Ampla

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  

Configuração do scanner de ressonância magnética para imagens funcionais visuais humanas

Comece usando um scanner de ressonância magnética 3T equipado com bobinas de cabeça de receptor multicanal para imagens de ressonância magnética funcionais. Use a metade posterior para garantir um ângulo de visão maior sem obstrução. Em seguida, configure uma sequência MPRAGE ponderada em T1 inserindo um tempo de repetição de 2,2 segundos e um campo de visão de 176 por 256 por 208 milímetros.Fornecer uma resolução espacial de 1 por 1 por 1 milímetro. Largura de banda de 190 hertz por pixel. Ângulo de inversão de 13 graus.E uma duração de varredura de 3,1 minutos. Configure uma sequência EPI de eco gradiente com um tempo de repetição de 2 segundos, tempo de eco de 30 milissegundos, campo de visão de 220 por 220 milímetros, resolução no plano de 1,7 por 1,7 milímetros com 29 cortes de 3 milímetros de espessura e uma largura de banda de cerca de 1500 hertz por pixel. Agora, meça as dimensões da bobina principal e do furo do scanner.Em seguida, conecte os tubos de PVC com cotovelos de PVC para construir uma estrutura de tubo de PVC simples e, com parafusos de nylon, prenda as extremidades da haste plástica que prende o espelho ao quadro. Observe que o espelho é preso à haste plástica com parafusos plásticos. Certifique-se de que os parafusos estejam soltos o suficiente para que o espelho seja girado manualmente para um ângulo ideal.Depois de parafusar uma tela de projeção traseira segmentada em um quadro, coloque a tela dentro da parte traseira do scanner, posicionando-a atrás da bobina da cabeça para maximizar o campo de visão.

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 ...