mri scanner setup for human visual functional imaging

시력 장애의 향상된 평가를 위한 시각 피질 매핑의 발전

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.

저자 스포트라이트: Wide-View fMRI Mapping을 통한 시각 피질 연구에 대한 통찰력 

광시야 망막 자극을 이용한 시각 피질의 기능적 자기 공명 영상(fMRI)

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  

인간 시각 기능 이미징을 위한 MRI 스캐너 설정

기능적 자기 공명 영상을 위해 다중 채널 수신기 헤드 코일이 장착된 3T MRI 스캐너를 사용하여 시작합니다. 더 큰 시야각을 보장하기 위해 뒤쪽 절반을 사용하십시오. 다음으로, 2.2초의 반복 시간과 176 x 256 x 208mm의 시야를 입력하여 T1 가중치 MPRAGE 시퀀스를 설정합니다.1 x 1 x 1mm의 공간 해상도를 제공합니다. 픽셀당 190Hz의 대역폭. 13도의 플립 각도.그리고 스캔 시간은 3.1분입니다. 반복 시간 2초, 에코 시간 30밀리초, 시야각 220 x 220mm, 평면 내 해상도 1.7 x 1.7mm, 두께가 3mm인 슬라이스 29개, 픽셀당 약 1500Hz의 대역폭으로 그래디언트 에코 EPI 시퀀스를 설정합니다. 이제 헤드 코일과 스캐너 보어의 치수를 측정합니다.그런 다음 PVC 튜브를 PVC 엘보우와 연결하여 간단한 PVC 파이프 프레임을 만들고 나일론 나사로 거울을 고정하는 플라스틱 막대의 끝을 프레임에 부착합니다. 거울은 플라스틱 나사로 플라스틱 막대에 부착되어 있습니다. 거울을 최적의 각도로 수동으로 회전할 수 있을 만큼 나사가 느슨한지 확인하십시오.분할된 리어 프로젝션 스크린을 프레임에 나사로 고정한 후 스크린을 스캐너 뒷면 안쪽에 놓고 헤드 코일 뒤에 배치하여 시야를 최대화합니다.

mri-scanner-setup-for-human-visual-functional-imaging

Research

JoVE Journal

Neuroscience

MRI Scanner Setup for Human Visual Functional Imaging

103 조회수.  Renaissance School of Medicine at Stony Brook University. 기능적 자기 공명 영상을 위해 다중 채널 수신기 헤드 코일이 장착된 3T MRI 스캐너를 사용하여 시작합니다. 더 큰 시야각을 보장하기 위해 뒤쪽 절반을 사용하십시오. 다음으로, 2.2초의 반복 시간과 176 x 256 x 208mm의 시야를 입력하여 T1 가중치 MPRAGE 시퀀스를 설정합니다.1 x 1 x 1mm의 공간 해상도를 제공합니다. 픽셀당 190Hz의 대역폭. 13도의 플립 각도.그리고 스캔 시간?...

비디오: 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 used to functionally map the peripheral and central visual cortex. This method for measuring functional changes of the visual brain allows for functional mapping of the occipital lobe, stimulating &gt;100&#176; (&plusmn;50&#176;) or more of the visual field, compared to standard fMRI visual presentation setups which usually cover &lt;30&#176; of the visual field. A simple wide-view stimulation system for BOLD fMRI can be set up using common MR-compatible projectors by placing a large mirror or screen close to the subject's face and using only the posterior half of a standard head coil to provide a wide-viewing angle without obstructing their vision. The wide-view retinotopic fMRI map can then be imaged using various retinotopic stimulation paradigms, and the data can be analyzed to determine the functional activity of visual cortical regions corresponding to central and peripheral vision. This method provides a practical, easy-to-implement visual presentation system that can be used to evaluate changes in the peripheral and central visual cortex due to eye diseases such as glaucoma and the vision loss that may accompany them.

We have developed techniques for mapping the visual cortex function utilizing more of the visual field than is commonly used. This approach has the potential to enhance the evaluation of vision disorders and eye diseases.

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

연구

신경과학

Begin by using a 3T MRI scanner equipped with multi-channel receiver head coils for functional magnetic resonance imaging. Use the posterior half to ensure a larger viewing angle without obstruction. Next, set up a T1 weighted MPRAGE sequence by inputting a repetition time of 2.2 seconds and a field of view of 176 by 256 by 208 millimeters.Provide a spatial resolution of 1 by 1 by 1 millimeter. Bandwidth of 190 hertz per pixel. Flip angle of 13 degrees.And a scan duration of 3.1 minutes. Set up a gradient echo EPI sequence with a repetition time of 2 seconds, echo time of 30 milliseconds, field of view of 220 by 220 millimeters, in-plane resolution of 1.7 by 1.7 millimeters with 29 slices of 3 millimeters thickness, and a bandwidth of about 1500 hertz per pixel. Now, measure the dimensions of the head coil and scanner bore.Then, connect the PVC tubes with PVC elbows to construct a simple PVC pipe frame, and with nylon screws, attach the ends of the plastic rod holding the mirror to the frame. Note that the mirror is attached to the plastic rod with plastic screws. Make sure that the screws are loose enough for the mirror to be manually rotated to an optimum angle.After screwing a segmented rear projection screen to a frame, place the screen inside the back of the scanner, positioning it behind the head coil to maximize the field of view.

fMRI Participant Preparation and Visual Cortex Scanning

FMRI Participant Preparation and Visual Cortex Scanning  

Begin by instructing the participant to fixate on the central cross during the imaging scans. Briefly demonstrate the visual stimulation to familiarize the participant with the procedure. Position the participant comfortably on the scanner table and immobilize the participant's head in the posterior half of the head coil array with foam padding to reduce motion artifacts.Provide ear plugs to protect their hearing. Use the scanner's positioning system to move the table into the scanner bore. Place the wide-view mirror 10 centimeters from the participant's eyes.Adjust the mirror to maintain a consistent viewing angle. Begin fMRI scanning with a localizer scan, incorporating three orthogonal planes and adjusting the scanner for frequency and shimming calibration. Proceed with an MP-RAGE anatomical scan for enhanced EPI slice positioning.At the start of the fMRI protocol, instruct the participant to fixate on the white cross atop a gray background at the stimuli's center for 10 seconds. Create visual stimuli using a compatible program by displaying a series of rotating wedges for 30 seconds. The wedges should extend to the edge of the screen or mirror with an eight-hertz contrast-reversing black and white checkerboard pattern.Present the white cross for an additional 10 seconds. Repeat cross fixation and stimulation display with the second 30-second visual stimulation paradigm, consisting of expanding and contracting rings. Maintain an eight-hertz contrast-reversing black and white checkerboard pattern at 100%contrast during the experiment.Upon completion of imaging, slide the table out of the scanner bore, ensuring the participant remains still. Next, remove the screen and then remove the mirror before placing the anterior portion of the head coil. Position the table back into the center of the scanner.Acquire a quick localizer scan to account for any movement, followed by an MP-RAGE scan using the full head coil. The polar maps revealed no obvious differences between the primary open-angle glaucoma participants and healthy participants. The eccentricity maps showed that the central region of the parafovea that was activated by the smaller ring stimuli appeared larger in the primary open-angle Glaucoma patient.BOLD percent changes at different eccentricities were reduced in primary open-angle glaucoma patients, especially at more peripheral eccentricities. The BOLD changes were significantly reduced between the two groups, more so at larger eccentricities. The BOLD percent changes averaged for central vision were only slightly and not significantly reduced in primary open-angle glaucoma patients, while the changes were significantly reduced for peripheral vision.