Pitfalls and feasibility of a protocol of virtual colonography designed for the screening of colo-rectal pre-cancerous lesions.

PURPOSE: To evaluate the pitfalls occurring during the virtual colonoscopy examination performed with a protocol designed for screening purposes.

MATERIALS AND METHODS: 40 patients underwent a spiral CT for virtual colonoscopic evaluation with the following parameters: collimation 3 mm, feed 6 mm.rot(-1), pitch 2 and increment 1 mm in supine position. Virtual colonography examination was carried out using a dedicated workstation equipped with a software which allows to generate 3D images and virtual endoscopic views. Colon distension, fluid and fecal material were assessed on a 3 point scale.

RESULTS: Distension score was 0.50. Left colon and cecum score was 0.32 while in the sigmoid and rectum the score was worse with 0.86. Fluid and fecal residues scores were 0.31 and 0.19 respectively. On almost half of the patients additional scans would be necessary. The main cause of additional scans is suboptimal intestinal preparation and colon distension.

CONCLUSION: The use of virtual colonoscopy for screening purposes will be possible through the further technical development and with the optimisation of the protocols, particularly by the improvement of colon cleansing and distension.