European researchers support MR colonography

Although the debate regarding MR colonography screening lives on, European radiologists agree dark lumen MRC is ready for prime time, according to studies presented Tuesday.

MRC has proved no better than CT colonography for detection of polyps smaller than 6 mm. But concerns about ionizing radiation exposure, especially in Europe, give MRC an advantage over CT when it comes to screening younger patient populations.

Dark lumen MR colonography may play an important role in colon cancer screening as a noninvasive alternative to CT in young, healthy patients. Increased contrast uptake of a polyp. (Provided by B. Bassler)

Dr. Boris Bassler and colleagues in the department of diagnostic and interventional radiology at the Klinikum Ludwigshafen, Germany, assessed 100 patients with dark lumen MRC who also had an indication for colonoscopy. They found MRC's sensitivity for adenomatous polyps ranging 6 mm to 9 mm, and larger than 9 mm, to be 84.2% and 100%, respectively.

The team could not detect hyperplastic polyps with MRC, and the sensitivity they observed for adenomatous lesions smaller than 6 mm was less than 20%. Such findings do not deter MRC imagers.

"There is still controversy with CT colonography screening regarding polyps under 6 mm. Many radiologists aren't sure if these are worth worrying about, so why should we?" Bassler said. "We are wondering how big CT colonography is getting in the U.S., since patients there don't seem particularly afraid of radiation. In Europe, political pressures from environmental groups have made people wary."

In another study, Swiss researchers assessed dark lumen MRC at 3T. Dr. Bettina Saar and colleagues at the University of Bern enrolled 23 patients previously referred for colonoscopy. Although they could not successfully translate all of the features of 1.5T into 3T, researchers found that the stronger magnetic field improves the detection of colorectal lesions. They also found that contrast-enhancement and the digital subtraction of images could help lesion characterization.

Another study by German researchers evaluated the accuracy of a new MRC protocol that favors fecal tagging over colonic cleansing. These investigators found fecal tagging MRC can be applied to screening, especially as patients are highly accepting of the procedure compared to standard colonoscopy and CT colonography.