VIRTUAL ENDOSCOPY OF THE SMALL-BOWEL - PHANTOM STUDY AND PRELIMINARY CLINICAL-RESULTS

The purpose of this study was to determine the optimal scanning techni que for lesion detection in a small bowel phantom and to evaluate the virtual endoscopy (VE) technique in patients. A small bowel phantom wi th a fold thickness of 7 mm and length of 115 cm was prepared with nin e round lesions (3 x 1 mm, 2 x 2 mm, 2 x 3 mm, 2 x 4 mm). Spiral CT pa rameters were 7/7/4, 3/5/2, 3/5/1, 1.5/3/1 (slice thickness/table feed /reconstruction interval). VE was done using volume rendering techniqu e with 1 cm distance between images and 120 degrees viewing angle. Two masked readers were asked to determine the number and location of the lesions. Seven patients underwent an abdominal CT during one breathho ld after placement of a duodenal tube and filling of the small bowel w ith methyl cellulose contrast solution. VE images were compared with t he axial slices with respect to detectability of pathology. With the 7 /7/4 protocol only the 4-mm lesions were visualised with fuzzy contour s. The 3/5/2 protocol showed both 4-mm lesions, one 3-mm lesion and on e false positive lesion. The 3/5/1 protocol showed both 4-mm and both 3-mm (one uncertain) lesions with improved sharpness, and no false pos itive lesions. One 2-mm and one 1-mm lesion were additionally seen wit h the 1.5/3/1 protocol. Path definition was difficult in sharp turns o r kinks in the lumen. In all patients, no difference was found between VE and axial slices for bowel pathology; however, axial slices showed 'outside' information that was not included in VE. We conclude that t he 3/5/2 protocol may be regarded as an optimal compromise between les ion detection, coverage during one breathhold, and number of reconstru cted images in patients; round lesions of 4 mm in diameter can be dete cted with high certainty.