INVIVO DETERMINATION OF THE ANISOTROPIC DIFFUSION OF WATER AND THE T1AND T2 TIMES IN THE RABBIT LENS BY HIGH-RESOLUTION MAGNETIC-RESONANCE-IMAGING

Purpose. Several magnetic resonance imaging (MRI) ''tools'' for ophtha lmologic research have recently been developed in this laboratory, inc luding improved gradient and radiofrequency coils and pulse sequences for high-resolution and diffusion imaging (100-mum resolution). Method s. These tools have been applied to the in vivo measurement of the rel axation parameters (TI and T2) and the water diffusion coefficients (D (x) and D(y)) in the rabbit eye lens, both normal and cataractous. Map s of these parameters in the lens have been computer generated. Result s. In the normal lens, water diffusion is highly anisotropic and tends to be parallel to the surface. In the trauma-induced cataractous lens , an increase in spin-spin relaxation times (T2) consistent with edema and alteration of diffusion patterns was observed in a study conducte d 2 weeks postsurgery. A partial reversal was observed 6 weeks postsur gery. The histologic data on the enucleated lens at 6 weeks showed a l oss of normal lens architecture. Images are shown that display other s mall structures of the anterior segment with great clarity. Conclusion s. An extension of this work, now underway, is the study of the format ion of various types of cataract in animal models. It is hypothesized that these methods can be extended to humans as a quantitative alterna tive for the assessment of cataracts.