Preoperative staging of rectal carcinoma using double-contrast MR imaging. Technical aspects and early clinical experiences

PURPOSE: To improve preoperative staging of rectal carcinoma with MR imaging, using a double-contrast technique. MATERIAL AND METHODS: Imaging was performed in 12 patients before and after i.v. injection of Gd-DTPA and rectal administration of a superparamagnetic contrast medium, mainly containing magnetite. The diagnostic information was evaluated and compared with findings at surgery and histopathological analysis. RESULTS: The superparamagnetic contrast medium enema caused a distension of the rectum and intraluminal signal void, whereas Gd-DTPA enhanced the mucosa in T1-weighted images. This allowed an evaluation of the normal rectal wall and separation of the mucosa, tunica muscularis and perirectal space in all cases, which was not possible in T1- or T2-weighted precontrast images. The rectal carcinoma could be delineated and tumor invasion to the rectal wall determined in all cases. The findings in postcontrast MR corresponded with the findings at histopathological examination in 11 of 12 patients. The histopathological examination in one patient revealed metastases (< 1 cm) in regional lymph nodes, too small to be identified in pre- or postcontrast MR images. CONCLUSION: Double-contrast-enhanced MR imaging allows evaluation of the normal rectal wall and preoperative staging of rectal carcinoma.