In vivo diffusion tensor MRI of the mouse retina: a noninvasive visualization of tissue organization.

Diffusion tensor MRI (DTI) is a method for the noninvasive assessment of cellular organization and integrity in vivo. In this study, in vivo DTI was performed to demonstrate its ability to reflect photoreceptor cell alignment in adult C57BL/6 wild-type mice. Age-matched retinal degeneration 1 (rd1) mice were employed as a negative control, i.e. loss of the photoreceptor cell layer. In wild-type mice, DTI-estimated cell alignment suggests that the MR-detected outer retinal layer comprises cells aligning perpendicular to the retinal surface, consistent with the known organization of photoreceptor cells. The MR-detected outer retinal layer exhibits a lower apparent diffusion coefficient and higher fractional anisotropy than the other two MR-detected retinal layers (p < 0.05 for all comparisons). In rd1 mice, the remaining MR-detected retinal layer exhibits different cell alignment, apparent diffusion coefficient and fractional anisotropy from that of the MR-detected outer retinal layer in wild-type mice (p < 0.05 for all comparisons), reflecting the degeneration of photoreceptor cells in rd1 mouse retina. Overall, our findings suggest that in vivo DTI assessment of mouse retina with normal physiology or degenerative pathology is feasible.