Computer-aided diagnosis also may soon play a part in virtual colonoscopy. Software improvements could help identify potential polyps missed on visual inspection. The final determination would still be made by the physician. “It will be very important for helping us improve our detection rate, decrease interobserver variability, and … make our examination more efficient by [more quickly] bringing our attention to lesions that we might have missed,” he said.
Virtual colonoscopy examinations involving minimal bowel preparation might even be possible soon. “One of the big obstacles to colorectal cancer screening is that most patients do not want to have to undergo a rigorous, cathartic bowel preparation,” Dr. Heiken said. Consequently, many patients who should be screened forgo this exam. Some studies have shown that it is feasible to perform CT colonography with stool and fluid tagging but without cathartic preparation and get good results.
Greater patient discomfort associated with colon inflation during virtual colonoscopy is another potential limitation. However, discomfort most often arises from the use of room air to insufflate the colon, Dr. Heiken noted. The use of CO2 is more comfortable for the patient and the gas is more quickly reabsorbed by the body.
Transaxial and sagittal views (left and middle) are shown of a rectosigmoid junction polyp imaged by a conventional CT scanner. A corresponding 3-D endoluminal view is shown of the same polyp (right). Photos courtesy Dr. Jay P. Heiken
