SMALL SIMULATED POLYPS IN PIG COLON - SENSITIVITY OF CT VIRTUAL COLOGRAPHY

PURPOSE: The authors evaluated computed tomographic (CT) virtual colog raphy for the detection of simulated polyps under ideal conditions, as well as the effects on lesion conspicuity of (a) collimation, (b) tab le pitch, and (c) orientation of the colon lumen with respect to the g antry. MATERIALS AND METHODS: Pig colon was resected and cleansed, and polyps with diameters of 3, 7, and 10 mm were created. Each specimen was scanned with collimation of 5 and 7 mm and table pitch of 1.0, 1.6 , and 2.0 at angles of 0 degrees, 45 degrees, and 90 degrees to the ga ntry. The initial two-dimensional (2D) images were reconstructed at 1- mm intervals (2D reconstructions), from which three-dimensional (3D) v irtual colography images were generated. Polyp conspicuity on the init ial and reconstructed 2D images and the 3D reconstructions was evaluat ed on a three-point scale: 0 = polyp not depicted, 1 = polyp faintly d epicted, and 2 = polyp clearly depicted. RESULTS: The 10-mm-diameter p olyp was clearly depicted (grade 2 conspicuity) on every initial and r econstructed 2D image and 3D reconstruction without regard to collimat ion, table pitch, or angle to the gantry. The 7-mm-diameter polyp was clearly depicted (grade 2 conspicuity) on every initial and reconstruc ted 2D image, but conspicuity on 3D reconstructions varied as the imag ing parameters varied. The 3-mm-diameter polyp was faintly depicted (g rade 1 conspicuity) on the initial and reconstructed 2D images and 3D reconstructions, but conspicuity varied on the 3D reconstructions as t he imaging parameters varied. CONCLUSION: CT virtual colography helped detection of small mucosal polyps regardless of the angle of the colo n lumen to the gantry at which they were obtained.