SAN DIEGO--Use of two- and three-dimensional helical computed tomographic colography (CTC) appears to be a feasible technique for the detection of colorectal polyps, Mayo Clinic researcher Amy K. Hara, MD, said at the American Roentgen Ray Society annual meeting.
Two-dimensional CTC is used to show re-formatted cross-sections of the colon, while the 3D technique, also known as virtual colonoscopy, provides a com-puter-generated intraluminal perspective of the colon (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 detected 100% of polyps that were 5 mm or larger (37 of 37) and 38% of polyps less than 5 mm (13 of 34). She noted that the study was unblinded in that "we knew where the polyps were by colonoscopy."
In the study, patients were imaged with a helical CT scanner immediately before colonoscopy. Raw CT images were transferred to an off-line computer workstation where 2D and 3D CTC images were generated using customized software. These images were then independently assessed for colorectal polyps and compared with the videotaped colonoscopies.
Although the research results are preliminary, Dr. Hara pointed out several potential benefits of the technique over colonoscopy: No anesthesia is required, the CT procedure is quicker, requiring only a couple of minutes vs 20 to 30 min-utes for colonoscopy, and there is less risk of complications. She said in an interview that the Mayo group has now studied about 100 patients with the new technique.