Quantitative Magnetic Resonance Imaging in Assessment of the Blood-Retinal Barrier

Application of magnetic resonance imaging (MRI) in two-dimensional quantitative assessment of blood-retinal barrier dysfunction was investigated in rabbits using a 0.1 T (4.25 MHz) resistive system. Reliable and consistent measurements of vitreous Tl were obtained repeatedly, in slices of width 5 mm and X-Y resolution of 1.2 mm. Calibration of reduction of Tl in eyes after injection of gadolinium-DTPA (Gd-DTPA) was performed, resulting in a dose-related response of relaxation rate (1/T1) to the dose of Gd-DTPA injected. Follow-up scans of injected eyes demonstrated a gradual spread of the Tl "hot-spot" as the contrast agent diffused through the vitreous. Tl rose gradually to basal levels by 72 hr. No local effect of Gd-DTPA was found by ophthalmoscopy. Xenon arc photocoagulation of rabbit retina reduced Tl from 1638 ± 54 (n = 6, mean ± SD) ms to 1408 ± 118 (n = 4) msec (P < 0.01) throughout the vitreous 5-7 hr after treatment. In treated rabbits receiving 1.0 mmol/1 Gd-DTPA intravenously, Tl adjacent to lesions 90-120 min after injection was further reduced in a 63 nl voxel to 670 ± 50 ms (mean ± SD, n = 5) with a minimum pixel value of 285 ± 52 ms. It was estimated that this represented leakage into vitreous of 8.3 nmol Gd-DTPA. Plasma Gd-DTPA concentrations declined rapidly, with half-life of 20-40 min. The findings indicate that MRI is a technique with the potential for repeated quantitative three-dimensional assessment of blood-retinal barrier dysfunction. Invest Ophthalmol Vis Sci 29:663-670,1988