The Applications of Functional MRI in Patients with Visual Pathway Diseases

The Applications of Functional MRI in Patients with Visual Pathway Diseases
　　Objective To observe retinotopic representations of health adults using functional magnetic resonance imaging, to investigate the retinotopic representations of patients who have visual pathway diseases and compare the the results of the fMRI imaging and the central visual field examination.Subjects and Methods Subjects: 1.Three health adults aged 24-30(2 male, 1 female), without contraindications of MRI. Visual acuity was 1.0 or corrected to 1.0. 2. Two patients with optic neuritis and four patients with sellar region occupying, including three patients with pituitary magnetic lifter adenoma and one patient with craniopharyngioma. Methods: Visual stimuli: The stimuli subtended a field of view of about 12 degrees, consisted of high contrast, drifting checkerboards. Two types of stimuli were used: the annular ring, either contracting or expanding, was used to map eccentricity and the rotating wedge, either clockwise or counterclockwise, was used to map the polar angle. MRI parameters: GE signa VH/i 3.0T scanner. Functional data: GRE-EPI sequence, 20 slices lying perpendicular to the calcarine sulcus. Anatomical data was obtained using 3D-SPGR sequence to acquire high resolution.
　　Data analysis: The cortical surface was unfolded and then cut and inflated. Functional data was presented to the inflated surface and subsequently analyzed magnetic lifter by AFNI software.Results The retinotopic representations of health adults were obtained by using the phase-encoded visual stimuli. The Eccentricity coordinate maps showed that foveal representations lay in the occipital poles and the representations appeared further anterior as eccentricity increased. The Polar angle coordinate maps showed that early retinotopically organized areas had a representation of visual field. In 6 patients, 5 had loss of visual acuity, abnormal of VEP and visual field defects. The main patterns of visual field abnormalities were superior temporal defect, temporal hemianopia and central scotoma et al. Less or no visual cortex response was revealed in the patients’ fMRI or the response in injury side was vanished.
　　The visual cortex response related with the visual field defects can not be induced in fMRI. But the retinotopic representations of the visual cortex did not change.Conclusion Phase-encoded stimuli was validated to be an efficient way to revealretinotopic representations of visual cortex; in patients who have visual pathwaydiseases, the results of fMRI and perimetric evaluation were positively correlated.The functional activations found in the visual cortex were consistent with the resultsof perimetric evaluation. There was a good correlation between fMRI data and theresults of magnetic lifter perimetric evaluation. The fMRI can show the visual field defects underpathological conditions; promising a solid foundation for the future research underpathological conditions.