Double-contrast MRI for the staging of rectal carcinoma: Technical aspects and clinical experience

Sammanfattning: Aim of the study Today´s methods for the staging of rectal carcinoma: ultrasonography with transrectal probe, CT, MRI or MRI with a rectal coil, all have limitations. The aim was therefore to develop a new, double-contrast MRI method for evaluation of rectal carcinoma. The idea was that a rectally applied contrast medium causing distension and signal void of the rectal lumen and an intravenous injection of contrast medium containing gadolinium to increase the signal from the mucosa would facilitate tumor staging and allow assessment of the rectal wall. Material, Methods and Results In a phantom study, using a 0.3T MR system, the signal alterations, artifacts and distorsion induced by the super-paramagnetic bowel contrast medium, Ferristene, were evaluated. A concentration of 20 mg iron/liter gave the best results. In a study of 12 patients, using a 0.3T MR system, the double-contrast MRI made possible the evaluation of the normal rectal wall and could be used for staging of rectal carcinoma. In a study of 29 patients, using a 0.3T MR system, the double-contrast MRI had a sensitivity of 100%, a specificity of 70% and an accuracy of 90% in distinguishing tumor stages more advanced than Dukes´ A. In a prospective, multicenter study using 1.0 or 1.5T MR systems, it was shown that the method had a sensitivity of 97%, a specificity of 50% and an accuracy of 82% for staging rectal carcinoma more advanced than stage T2. The possibility of replacing Ferristene by air in the double-contrast method was evaluated in ten patients. Ferristene was superior, mainly because the patients were unable to keep the air in the rectum. Conclusion The study has shown that double-contrast MRI is a robust and reliable method for staging of rectal carcinoma.