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Data Interpretation Techniques

Currently many sophisticated computer workstations are available to interpret virtual colonoscopy examinations. These workstations allow fast processing of the data as well as an interactive ability to evaluate an abnormality in multiple views. There is some controversy regarding whether virtual colonoscopy examinations should be interpreted using a primary two-dimensional or three-dimensional viewing technique.

2-D Axial image on the left and 3-D endoluminal image on the right show ulcerated adenocarcinoma in the rectum (white arrows).

The three-dimensional viewing technique uses the computer to generate a center-line path through the colon that simulates the view obtained by a conventional colonoscopy. The disadvantage of this technique is that large areas of the colon are obscured behind folds. To optimally evaluate data using a 3D technique, four "fly-through" views are required. Two of these are taken with the view traveling down the colon, one with the patient lying on the back and one on the stomach. Two views are taken traveling up the colon, one with the patient lying on the back and one on the stomach. Even using these techniques, the entire colon surface may not be visualized. Moreover, it is time consuming.

Most investigators agree that a primary 2D review using appropriate views is sufficient for problem solving (31, 46). Using these techniques the colon can be evaluated in approximately 5-15 minutes by an experienced trained radiologist. It is important to remember that whether one uses 2D or 3D as the primary review technique, both must be available to accurately differentiate folds, polyps, and residual fecal material.