Jared Dean Christensen MD, Presenter: Nothing to Disclose

Lynne Michelle Hurwitz MD, Abstract Co-Author: Research Grant, Siemens AG Research Grant, General Electric Company

Daniel Tobias Boll MD, Abstract Co-Author: Research support, Siemens AG Research support, Koninklijke Philips Electronics NV Research support, Bracco Group Consultant, Toshiba Corporation

CTA evaluation of the aorta can be problematic due to cardiac motion artifact during conventional non-ECG gated helical single source standard pitch (SS SP) CTA acquisition. Dual source non-ECG gated high pitch (DS HP) CTA is an alternative technique that may reduce motion artifact without increasing radiation dose or compromising diagnostic image quality. This study compares dose and image quality of DS HP vs SS SP CTA of the thoracic aorta.

In this IRB-approved study we evaluated 20 patients who had both a DS HP and comparison SS SP CTA of the thoracic aorta. HP exams were performed on a dual source 64 MDCT scanner (Definition, Siemens Medical Systems) with the following settings: 120 kVp, qual ref mAs 250, automatic pitch adjustment (1.85-2.4), rotation time 0.33 s. SS SP CTAs were acquired on a 64 MDCT with identical parameters except for pitch (1.375) and rotation time, 0.5-0.8 s. Weight-based contrast dosing of IsoVue 370 was used for all scans at the same injection rate. CTDIvol was recorded for all exams. Quantitative image quality was assessed by calculating contrast to noise (CNR) at the sinuses of Valsalva (CNRv) and ascending aorta (CNRa). Qualitative assessment was performed by randomized, blinded dual reader consensus for wall motion artifact at the aortic valve annulus, sinuses of Valsalva and ascending aorta on a 4-point scale (0=no motion, 3=severe). Statistical analysis with paired t-test evaluated corresponding qualitative and quantitative parameters.

Mean CTDI for DS HP vs. SS SP CTA was lower (13.9±2.4 vs. 15.9±4.0, respectively, p=0.08). CNR analysis showed a marginal increase in mean CNRv (46.3 vs. 45.6, p=0.79), and mean CNRa (47.1 vs. 45.3, p=0.52), for the HP protocol. There were, however, significant improvements in image quality in relation to motion for DS HP vs. SS SP technique (p<0.05), with mean scores assessing wall motion artifacts at the level of the annulus (0.4 vs. 1.8), sinuses of Valsalva (0.7 vs. 2.0), and ascending aorta (0.6 vs. 1.8).

DS HP CTA significantly decreases motion-related artifact of the thoracic aortic without decreasing CNR compared to SS SP CTA at comparable radiation dose levels.

DS HP CTA may result in decreased motion artifact of the thoracic aorta thereby potentially improving diagnostic accuracy without negatively impacting CNR or patient radiation dose.

Christensen, J, Hurwitz, L, Boll, D, Dual Source High Pitch vs. Single Tube Standard Pitch Computed Tomographic Angiography (CTA) of the Thoracic Aorta: Quantitative and Qualitative Assessment of Image Quality and Radiation Dose.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033514.html