Yulia Smal, Presenter: Nothing to Disclose

Paul Deak DIPLPHYS, PhD, Abstract Co-Author: Employee; General Electric Company

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG Founder, CT Imaging GmbH Scientific Advisor, CT Imaging GmbH Shareholder, CT Imaging GmbH Founder, Artemis Imaging GmbH CEO, Artemis Imaging GmbH Shareholder, Artemis Imaging GmbH

Dual-source (DS) CT scanners allow for higher pitch cardiac acquisitions. We compared different cardiac scan protocols for pediatric patients with respect to image quality (IQ) and dose, including standard and high-pitch (HP) examinations.

Measurements and simulations were performed for a DSCT scanner (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). Pediatric cardiac protocols were investigated with respect to image quality and dose by varying the tube voltage and pitch factor. For each tube voltage of 80, 100, 120, and 140 kV pitch factors of 0.17, 0.22, 0.30, 0.38, 0.44, and 0.52 corresponding to standard cardiac acquisitions and 3.4 corresponding to a HP acquisition were considered. Organ and effective (E) dose values were computed for a series of anthropomorphic pediatric phantoms with all organ of interest geometrically defined mimicking 0, 1, 5, 10, and 15 years-old patients using a validated 3D dose calculation software tool (ImpactMC, CT Imaging GmbH, Erlangen, Germany). E was computed from organ doses distributions using the tissue weighting factors from ICRP 103.

Noise levels for standard and HP acquisitions were essentially constant with differences not exceeding 15% on average. For each age group, reduction of E up to 92% was observed with increase of the pitch factor from 0.17 to 3.4 for constant voltage. For all age groups, E increased by up to a factor of 5 with the increase of tube voltage from 80 kV to 140 kV for constant pitch. Doses decreased with increasing child age. For example, scanning with 100 kV and pitch = 0.22 resulted in E of 7.7 and 3.0 mSv for neonate and 15-year old, respectively; doses in lung, heart and breast (females only) were equivalent to 24.4, 25.7, 22.8, and 10.5, 13.8, 10.0 mGy, respectively.

Lower dose values are to be expected for HP cardiac protocols and for lower tube voltages without a detriment in IQ. Effective dose is higher for younger patients at constant IQ.

Effective dose for pediatric patients can be significantly reduced in high-pitch cardiac examinations.

Smal, Y, Deak, P, Kalender, W, Assessment of Effective Dose for Pediatric Patients Undergoing Dual-Source Standard and High-Pitch Cardiac CT Examinations.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9011200.html