Paul Deak, Presenter: Nothing to Disclose

Yulia Smal, Abstract Co-Author: Nothing to Disclose

Michael Marcus Lell MD, Abstract Co-Author: Nothing to Disclose

Stephan Achenbach MD, Abstract Co-Author: Research support, Siemens AG Consultant, Bracco Group Research support, Bayer AG

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Founder, VAMP GmbH Scientific Advisor, VAMP GmbH Shareholder, VAMP GmbH

Dual-source CT scanners allow for high-pitch (HP) acquisition protocols. We assessed the influence on dose of HP CT examinations for cardiac and chest protocols by dose measurements and by Monte Carlo (MC) simulations.

Measurements and MC simulations of dose were performed for a SOMATOM Definition Flash scanner (Siemens Healthcare, Forchheim, Germany). Organ dose values were measured in an anthropomorphic phantom (Alderson-Rando) using thermoluminescent dosimeters (TLD). Two scan protocols were considered: a cardiac examination of 126 mm and a chest examination of 300 mm scan length. For each scan protocol all scan parameters were kept constant except for the pitch factor (p). Cardiac examinations were performed for standard pitch protocols (SP) (p = 0.2, 0.3, and 0.5), and for a HP acquisition with p = 3.2. For chest examinations the pitch was 0.8 and 1.5 for the SP and 2.8 for the HP protocol. Organ dose calculations were performed for an anthropomorphic voxelized male phantom using a MC dose calculation tool (ImpactMC, VAMP GmbH, Erlangen, Germany). For each scan protocol organ and effective doses were computed. Image quality was assessed by evaluating the noise levels in regions of interest (ROI) for all scan protocols.

Measured and simulated organ doses agreed to within 20%. As expected, the dose values decreased with the increase of pitch factor when all other scan parameters were kept constant. Thus, for cardiac examinations the effective dose ranged between 28.8 to 1.1 mSv for pitch factors of 0.2 to 3.2, respectively. The same held true for chest examinations with effective dose values ranging from 4.8 to 1.7 mSv for pitch factors of 0.8 and 2.8, respectively. Noise for SP and HP protocols was comparable with differences below 10%, e.g. noise at 46 HU and 50 HU for p = 1.3 and 2.8, respectively in chest protocol.

Lower dose values (i.e. organ and effective dose) were achieved for both cardiac and chest protocols when using high-pitch acquisition protocols without impairing image quality.

High-pitch CT acquisition allows for significant reduction of patient dose.

Deak, P, Smal, Y, Lell, M, Achenbach, S, Kalender, W, Dose Assessment for Dual-Source High-Pitch Protocols in Thoracic and Cardiac CT.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8015904.html