Virtual coloscopy with multi-slice computerized tomography. Preliminary results

Abstract

Using multi-slice computed tomography (MSCT) large body areas can scanned with high spatial resolution. In this study, MSCT was employed for virtual colonoscopy in various pathologies of the colon. For MSCT a Somatom Plus 4, Volume Zoom scanner, (Siemens, Forchheim) was employed, equipped with four parallel detector rows. Twenty-five patients were included in this trial, prior to colonoscopy or partial colon resection. After cleaning the colon, distension was achieved by insufflation of room air using a rectal tube. The parameters of acquisition and reconstruction were as follows: collimation 4 x 1 mm and 4 x 2.5 mm respectively; tube charge per slice: 140-160 mAs; pitch 5-6; i.v. contrast medium: 120 ml Ultravist 300 (Schering) with a flow rate of 3 ml/s; delay: 35 s. For 3D reconstruction we used edge-enhanced volume rendering, virtual colonoscopy and extraluminal views of volume-rendered images. Nine polyps and four of five colon carcinomas were detected using MSCT virtual colonoscopy. In three patients with ulcerative colitis virtual coloscopy revealed morphological alterations compatible with this disease. In two of four patients with multiple diverticula of the colon the true extent of the disorder could be assessed in virtual colonoscopy. Utilizing virtual MSCT colonoscopy polyps and cancer of the colon can be reliably detected, if proper cleaning and distension is provided. On axial images alone smaller polyps may be assessed. The high z-axis resolution of MSCT offers superior conditions for CT-based virtual colonoscopy.