Rectal carcinoma: double-contrast MR imaging for preoperative staging

PURPOSE: To evaluate and compare the imaging findings and staging of rectal carcinoma by using conventional magnetic resonance (MR) imaging, MR imaging with an enema of superparamagnetic ferristene-based contrast material, and MR imaging with an enema of ferristene solution plus intravenous injection of gadodiamide. MATERIALS AND METHODS: Twenty-nine patients (17 women, 12 men; age range, 39-91 years) referred with a diagnosis of rectal carcinoma were examined. Analysis of the rectal wall and staging of the tumor were performed. In all patients, the MR imaging findings were correlated with the histopathologic findings. RESULTS: The contrast material enema caused distention of the rectum and an intraluminal signal void, whereas the gadodiamide injection caused enhancement of the mucosa on T1-weighted images. This enhancement enabled evaluation of the normal rectal wall and differentiation of the mucosa, tunica muscularis, and perirectal space, which was not possible on the nonenhanced images. Double-contrast (ferristene solution plus gadodiamide) MR imaging was superior to imaging with only ferristene-based contrast material and had a sensitivity of 100%, specificity of 70%, and accuracy of 90% in distinguishing tumor stages worse than Dukes A. CONCLUSION: Double contrast material-enhanced MR imaging enables accurate rectal carcinoma staging, which is not possible at nonenhanced imaging.