This year will be a critical time to assess the further validation and implementation of CT colonography as several important events unfold. Several multicenter trials in the US and Europe will begin to release study results including both screening and increased risk patient cohorts. by Beth G. McFarland, MD*


This year will be a critical time to assess the further validation and implementation of CT colonography (CTC, or virtual colonoscopy) as several important events unfold. Several multicenter trials in the US and Europe will begin to release study results including both screening and increased risk patient cohorts. In the United States, the ACRIN prospective screening trial of approximately 2,500 asymptomatic patients will announce results of diagnostic performance relative to colonoscopy. A Munich trial will also finish a validation study of screening patients, with early promising results discussed at the 2006 ESGAR meeting.

Key influences will affect implementation of CT colonography beyond the validation studies. Given the current low rate of reimbursement of screening in the United States, how third party payors interpret the new study results and decide on reimbursement policies will be very important. Definition of the target lesion of significance will have a significant impact at multiple levels, including cost effectiveness, training of readers and diagnostic performance in community settings. Standardization of currently proven techniques will be essential. Specifically a practical and effective method of stool tagging could help improve patient compliance to undergo colorectal screening, but also help decrease the false positives imparted by residual stool.

The development of CAD for CT colonography represents an exciting area of research which has the potential to improve accuracy of reader interpretation. CAD development will need to respond to the stool tagging techniques which best improve patient compliance. In addition CAD will need to focus on the target lesion size of importance. Specifically, excessive marking of small, unimportant polyps by CAD would drive down reader efficiency. Although there is wide consensus that the > 1 cm polyps are clinically significant, there is more controversy of the small and intermediate polyps. More widespread multi-disciplinary consensus will be essential to guide what the target lesion should be, within the clinical context of patient age, colorectal risks and symptoms. Thus, the technological developments of CTC, including CAD, will need to be shaped by key issues of clinical importance and management.


* Dr. Beth G. McFarland, from the Center for Diagnostic Imaging, Chesterfield, MO, is adjunct professor at the Washington University.