Katia Sourbelle PhD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: Multi-slice spiral CT (MSCT) scanning provides a constant level of image quality and dose along the z-axis. For multiple circle cone-beam CT (CBCT) scans using Feldkamp-type reconstruction, this cannot be guaranteed. We investigated variations of image quality and dose as a function of z-position. Methods and Materials: To evaluate differences in behavior, we employed both simulations and measurements. MSCT measurements were performed on a 16-slice spiral CT scanner (Sensation 16, Siemens Medical Solutions, Forchheim, Germany) and circular cone-beam measurements on a rotating C-arm unit equipped with a 20 cm x 20 cm flat panel detector (Axiom Artis, Siemens Medical Solutions, Forchheim, Germany). Simulations were performed using both geometries. For MSCT, all parameters were kept constant and pitch was chosen as 1. For CBCT, the number of slices and thereby the cone angle were varied continuously; the pitch was chosen as the maximal value to achieve complete data (about 0.5 for full and 0.9 for short circular scan for the Sensation 16 geometry). In both cases, a Feldkamp-type reconstruction was performed such that the full detector information is used (100% dose usage). We investigated spatial resolution, slice sensitivity profiles, noise and dose on the axis of rotation. Results: As expected all image quality parameters investigated as well as dose remained constant as a function of z-position for MSCT. For multiple circular cone-beam scanning, an increase of dose was noticed at the junctions of two adjacent volumes, the amount of which depended on the cone angle. Consequently, the noise was reduced in this region, leading to a non-constant level of noise along the z-axis. While in-plane spatial resolution remained relatively constant and comparable to MSCT, slice sensitivity profiles and artifact behavior varied strongly with the cone angle. With respect to artifacts, multiple circle scans showed better image quality than a single circle scan, especially for full-scan reconstruction, due to the averaging effect at the volume junctions. Conclusion: Sequential scanning of contiguous CBCT volumes has disadvantages with respect to dose and image quality as compared to multi-slice whole-body spiral CT scanning.      

Sourbelle PhD, K, A Comparison of Image Quality and Dose for Whole Body Imaging by Spiral Scanning and by Multiple Circular Cone-Beam Scans.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3101430.html