Virtual Colonoscopy Technique Feasible in Detecting Polyps

SAN DIEGO--Use of two- and three-dimensional helical computedtomographic colography (CTC) appears to be a feasible techniquefor the detection of colorectal polyps, Mayo Clinic researcherAmy K. Hara, MD, said at the American Roentgen Ray Society annualmeeting.

Two-dimensional CTC is used to show re-formatted cross-sectionsof the colon, while the 3D technique, also known as virtual colonoscopy,provides a com-puter-generated intraluminal perspective of thecolon (see figures).

In the first 23 patients studied, who had 71 polyps found on colonoscopy,Dr. Hara said that the technique using both 2D and 3D images detected100% of polyps that were 5 mm or larger (37 of 37) and 38% ofpolyps less than 5 mm (13 of 34). She noted that the study wasunblinded in that "we knew where the polyps were by colonoscopy."

In the study, patients were imaged with a helical CT scanner immediatelybefore colonoscopy. Raw CT images were transferred to an off-linecomputer workstation where 2D and 3D CTC images were generatedusing customized software. These images were then independentlyassessed for colorectal polyps and compared with the videotapedcolonoscopies.

Potential Benefits

Although the research results are preliminary, Dr. Hara pointedout several potential benefits of the technique over colonoscopy:No anesthesia is required, the CT procedure is quicker, requiringonly a couple of minutes vs 20 to 30 min-utes for colonoscopy,and there is less risk of complications. She said in an interviewthat the Mayo group has now studied about 100 patients with thenew technique.