MR imaging of rectal cancer using endorectal surface coil. Histopathological correlation

Using a endorectal coil for MRI of receive only, extent and lymph node metastasis of tumor was checked for 55 cases of rectal cancer. MRI was performed with a 1.5 Tesla superconducting MR unit using tailored endorectal surface coils and fast spin echo (FSE) capabilities before surgery. And images compared with histopathological findings of specimens resected by surgery. After a submucosal saline injection using an endoscope, an image was obtained in 11 cases that may contain the early stage cancer. Normal intestinal wall was described as 5-6 layers including mucus and rectal fat tissue in T2-weighted image with FSE. The mucous membrane layer showed low signal, submucous membrane showed high signal, peculiar muscle layer showed low signal. In the diagnosis of depth of carcinomatous invasion, M-carcinoma was described as thickening of the mucous membrane layer in T2-weighted image, SM-carcinoma was as a tumor of low signal intensity in high signal area and asymmetry of a boundary with the submucous membrane and tumor. When a tumor invased to the peculiar muscle layer, the submucous membrane completely lacerated, and it was recognized as thickening of the muscle layer, laceration, and tumor with high intensity in muscle layer. When a tumor invased into rectal fat tissue, outside edge of tumor was showed as asymmetry in T1-weighted image, and described as laceration of the outer longitudinal muscle layer in T2-weighted image. MRI agreed well with histopathological findings in 45 cases. Submucous saline injection made thickening in submucous membrane and was useful for discrimination of M-carcinoma and SM1-3 carcinoma. The shape of the lymph node of the diameter about 5 mm was able to be evaluated because of diagnosing ability of the lymph node metastasis such as sensitivity 78.9% and specificity 74.1%. (K.H.)