Dark lumen MR-Colonography: initial experience

Purpose: The aim of this study was to assess a new strategy of MR colonogra phy for the detection of colonic polyps/malignancy. The technique is based on a rectal enema with water in combination with the intravenous applicatio n of a paramagnetic contrast agent. Methods: Twelve subjects were included in this study either due to suspected colorectal tumors or for screening pu rposes. For MR colonography the colon was filled with approximately 3000 ml of tap water while Gadobenate dimeglumine (0.2 mmol/kg) was injected intra venously. A T1w GRE sequence was acquired before and 75 sec after the contr ast administration only in prone position. Three patient underwent the "bri ght lumen" MRC as well. All MR examinations were performed at least five da ys prior to conventional colonoscopy and the results of both modalities wer e compared. Results: The colonic filling with water resulted in a homogeneo usly low signal throughout the colonic lumen in all twelve subjects. Intrav enous injection of gadolinium caused avid enhancement of the colonic wall. Similarly lesions arising from the colonic wall enhanced avidly. Dark lumen MR colonography correctly identified five polyps in four patients. Bright lumen MRC showed in one patient false positive results. Conclusion: The new MR colonography concept based on a dark colonic lumen and a bright, contra st enhanced colonic wall turned out to be a promising alternative to the tr aditional MRC based on a bright lumen concept. The new technique suggests a higher accuracy in detecting polyps, a better evaluation of other parenchy mal organs as well as a reduced time needed for data acquisition and analys is.