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

Migliorare la mappatura della corteccia visiva per una migliore valutazione dei disturbi visivi

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.

Autore in primo piano: approfondimenti sulla ricerca sulla corteccia visiva attraverso la mappatura fMRI ad ampia visuale 

Risonanza magnetica funzionale (fMRI) della corteccia visiva con stimolazione retinotopica ad ampio raggio

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  

Configurazione dello scanner MRI per l'imaging funzionale visivo umano

Iniziare utilizzando uno scanner MRI 3T dotato di bobine di testa del ricevitore multicanale per la risonanza magnetica funzionale. Utilizzare la metà posteriore per garantire un angolo di visione più ampio senza ostruzioni. Successivamente, impostare una sequenza MPRAGE pesata T1 inserendo un tempo di ripetizione di 2,2 secondi e un campo visivo di 176 x 256 x 208 millimetri.Fornire una risoluzione spaziale di 1 x 1 x 1 millimetro. Larghezza di banda di 190 hertz per pixel. Angolo di capovolgimento di 13 gradi.E una durata di scansione di 3,1 minuti. Impostare una sequenza EPI di eco sfumata con un tempo di ripetizione di 2 secondi, un tempo di eco di 30 millisecondi, un campo visivo di 220 x 220 millimetri, una risoluzione in piano di 1,7 x 1,7 millimetri con 29 sezioni di 3 millimetri di spessore e una larghezza di banda di circa 1500 hertz per pixel. Ora, misurare le dimensioni della bobina della testa e del foro dello scanner.Quindi, collegare i tubi in PVC con gomiti in PVC per costruire un semplice telaio in tubo in PVC e, con viti in nylon, fissare le estremità dell'asta di plastica che tiene lo specchio alla cornice. Si noti che lo specchio è fissato all'asta di plastica con viti di plastica. Assicurarsi che le viti siano sufficientemente allentate da consentire la rotazione manuale dello specchio a un'angolazione ottimale.Dopo aver avvitato uno schermo di retroproiezione segmentato a un telaio, posizionare lo schermo all'interno della parte posteriore dello scanner, posizionandolo dietro la bobina di testa per massimizzare il campo visivo.

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 ...