In vivo determination of the anisotropic diffusion of water and the T1 and T2 times in the rabbit lens by high-resolution magnetic resonance imaging.

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Abstract

PURPOSE: Several magnetic resonance imaging (MRI) "tools" for ophthalmologic research have recently been developed in this laboratory, including improved gradient and radiofrequency coils and pulse sequences for high-resolution and diffusion imaging (100-microns resolution). METHODS: These tools have been applied to the in vivo measurement of the relaxation parameters (T1 and T2) and the water diffusion coefficients (Dx and Dy) in the rabbit eye lens, both normal and cataractous. Maps of these parameters in the lens have been computer generated. RESULTS: 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 conducted 2 weeks postsurgery. A partial reversal was observed 6 weeks postsurgery. The histologic data on the enucleated lens at 6 weeks showed a loss of normal lens architecture. Images are shown that display other small structures of the anterior segment with great clarity. CONCLUSIONS: An extension of this work, now underway, is the study of the formation of various types of cataract in animal models. It is hypothesized that these methods can be extended to humans as a quantitative alternative for the assessment of cataracts.