STUDIES ON BROMOBENZENE-INDUCED HEPATOTOXICITY USING IN-VIVO MR MICROSCOPY WITH SURGICALLY IMPLANTED RF COILS

Using surgically implanted RF coils at 300 MHz, three-dimensional micr oscopic MR images of rat liver were obtained in vivo to follow the dev elopment of pathology induced by bromobenzene exposure. Formalin fixed specimens of liver from these animals were also imaged using in vitro MR microscopy, followed by conventional optical microscopy. All MR im ages were acquired using a spin-warp pulse sequence with TR = 950 ms a nd TE = 23 ms. The in vivo images were reconstructed as 256(2) x 32 ar rays with a voxel size of (50 mu m)(2) x 219 mu m, while the in vitro images were reconstructed as 256(2) x 128 arrays, giving an isotropic resolution at (39 mu m)(3). Based on results from six animals, we have found in all animals exposed to bromobenzene, image intensity decreas ed in specific hepatic tissue regions. These regions were well correla ted to low signal intensity areas observed in in vitro MR images at hi gher resolution. Conventional optical microscopy indicated that the lo w signal intensity regions corresponded to areas of necrosis. The decr ease in signal intensity is consistent with increased local diffusion coefficients as a result of necrosis. This study demonstrates that MR microscopy with implanted RF coils can be successfully used to follow tissue pathological changes in living tissues.