Relaxation Time Constants and Apparent Diffusion Coefficients of Rat Retina at 7 Tesla

摘要

MRI has recently been applied to study the retina in vivo. Measurements of relaxation time constants (T_1, T_2, and T_2~*) and the apparent diffusion coefficient (ADC) of the retina would be useful to sys-temically optimize structural, physiological, and functional MRI contrasts. MRI studies were performed on 12 anesthetized and paralyzed rats. High-resolution T_1, T_2, T_2~* and ADC of the rat eyes were measured at 50 × 50 × 800 μm at 7 Tesla. Profiles of T_1, T_2, T_2~* and ADC across the retinal thickness were analyzed. Region of interests of three layers across the retinal thickness were tabulated. This study demonstrated that high resolution T_1, T_2, T_2~* and ADC of the rat retina could be imaged. Profile analysis of T_1, T_2, T_2~* and ADC across the retinal thickness were helpful to minimize partial volume effects. T_1, T_2, T_2~* and ADC of the rat retina were overall similar to those of the brain. Quantitative T_1, T_2, T_2~* and ADC may change in retinal diseases and their measurements could help to stage retinal disease progression and monitor therapeutic intervention.