Colorectal tumors: an in vitro study of high-resolution MR imaging. To study the potential utility of magnetic resonance (MR) imaging in staging colorectal tumors, 15 resected colonic segments containing 17 elevated lesions were examined on a 1.5- or 1.9-T superconductive MR system. The whole intestinal wall was apparent as three or five layers on images obtained with a short repetition time (TR) and short echo time (TE) and as six or eight distinct layers, including the intestinal wall proper as well as an adherent mucus layer and an outer layer of pericolonic fat, on the long TR/TE images. In cases of colonic carcinoma, MR images correlated well with the pathologic findings, including the macroscopic growth pattern, depth of mural invasion, and the presence of foci of calcific tumor necrosis and pools of extracellular mucin (colloid). These features suggest that MR imaging may be valuable in the clinical evaluation of colorectal tumors. 