Relaxation time constants and apparent diffusion coefficients of rat retina at 7 Tesla

MRI has recently been applied to study the retina in vivo. Measurements of relaxation time constants (T₁, T₂, and T ₂*) and the apparent diffusion coefficient (ADC) of the retina would be useful to systemically optimize structural, physiological, and functional MRI contrasts. MRI studies were performed on 12 anesthetized and paralyzed rats. High-resolution T₁, T₂, T ₂* and ADC of the rat eyes were measured at 50 3 50 3 800 lm at 7 Tesla. Profiles of T₁, T₂, T₂* 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 T₁, T₂, T₂* and ADC of the rat retina could be imaged. Profile analysis of T₁, T₂, T₂* and ADC across the retinal thickness were helpful to minimize partial volume effects. T₁, T₂, T ₂* and ADC of the rat retina were overall similar to those of the brain. Quantitative T₁, T₂, T₂* and ADC may change in retinal diseases and their measurements could help to stage retinal disease progression and monitor therapeutic intervention.