"Studies from Asia have indicated that flat lesions are quite common, and often turn into cancer," said Perry Pickhardt, MD, associate professor of radiology at the University of Wisconsin Medical School in Madison. "Therefore it has been argued that virtual colonoscopy should not be used as a screening tool if it misses these lesions," he said.

However this study found that virtual colonoscopy detected 80% of the flat lesions (47 of 59 lesions) that were 6mm or more in size. Virtual colonoscopy detected 81% of the non-flat lesions, Dr. Pickhardt said. Twenty-nine of the 59 flat lesions were adenomas, which are potential precursors to cancer, said Dr. Pickhardt. Virtual colonoscopy detected 83% of the flat adenomas. It detected 86% (156 of 181) non-flat adenomas, he added. "It is apparent that virtual colonoscopy is equally good for detecting both flat and non-flat types of lesions," he said.

The study also found that flat adenomas are "uncommon in a typical western screening population, and advanced flat neoplasms are rare," said Dr. Pickhardt. The study found no diminutive flat lesions that were histologically advanced in the 1,233 patients screened with virtual colonoscopy, he said.

The study was sponsored by the Department of Defense and was conducted at the National Naval Medical Center in Bethesda, MD, Walter Reed Army Medical Center in Washington, DC, and the Naval Medical Center in San Diego, CA. All patients underwent both a virtual colonoscopy and a standard (optical) colonoscopy. All were considered "healthy" at the time of the colonoscopy examinations.

The study was published in the November 2004 issue of
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1-Nov-2004