Three‐Dimensional NMR microscopy of rat spleen and liver

Three‐dimensional microscopic NMR images of spleen and liver specimens from rats injected wlth dextran magnetite particles and from controls were obtained at 4.7 T, using a specially designed probe in conjunction with a 3D filtered back projection reconstruction algorithm. All of the images were reconstructed as 64³ arrays with (25 μm)³ isotropic voxels. With the aid of the MR contrast agent, the red pulp and marginal zone of the spleen and the portal triad of the liver could be distinguished from the surrounding tissue in T₂‐weighted images. For mature rat spleen, natural contrast in T₂‐weighted images was found to distinguish the same features. Histolog‐ical examinations of the tissues with and without contrast agent were also performed using an optical microscope. Microscoplc NMR images, despite their lower resolution, clearly revealed many features seen in the optical images.