Andrei S. Purysko MD, Presenter: Nothing to Disclose

Andrew Primak PhD, Abstract Co-Author: Employee, Siemens AG

Mark E. Baker MD, Abstract Co-Author: Research Consultant, Bracco Group Researcher, Siemens AG Research support, Siemens AG

Nancy A. Obuchowski PhD, Abstract Co-Author: Research Consultant, Siemens AG Research Consultant, Hologic, Inc Research Consultant, CVUS Research Consultant, Elucid Bioimaging Inc

Erick Marc Remer MD, Abstract Co-Author: Nothing to Disclose

Frank Dong PhD, Abstract Co-Author: Equipment support, Siemens AG Software support, Siemens AG

Binu John MD, MPH, Abstract Co-Author: Nothing to Disclose

Wadih Karim RT, Abstract Co-Author: Nothing to Disclose

Brian Robert Herts MD, Abstract Co-Author: Research Grant, Siemens AG

To compare the radiation dose and noise levels between single energy (SE) and dual energy (DE) computed tomography (CT) examinations of the abdomen performed in the same dual-source CT (DSCT) scanner.

IRB-approved, HIPPA-compliant prospective study of 45 adult subjects (mean age: 60.3 yrs. [SD=9.0] and mean effective diameter: 35.5 cm [SD=4.4]), who on different occasions had 3-phase exam of the liver in the same DSCT scanners (Flash, Siemens Healthcare) using SE protocol (120kVp; weight-based mAs) and DE protocol (100/Sn140kVp; mAs adjusted to match the CTDIvol of a weight-based mAs SE scan). The dose metrics (volume computed tomography dose index [CTDIvol], dose-length product [DLP], size-specific dose estimate [SSDE] and effective dose) from each phase were recorded. Image noise was obtained in the liver, retroperitoneal (RP) fat, IVC, and aorta. Distributions of outcome variables (dose and noise) were examined using Q-Q plots and Shapiro tests. A semi-anthropomorphic abdominal phantom (QRM GmbH, Germany) with two “fat” rings simulating patients with 30, 35 and 40-cm lateral dimensions was scanned with DECT and SECT at multiple dose levels to obtain the noise vs. dose curves.

All the dose metrics were significantly higher with SECT than with DECT (p < 0.001). The mean total DLP and effective dose on SECT were 1339 mGy-cm (SD, 544.63) and 20.09 mSv (SD, 8.17), and the mean total DLP and effective dose in DECT were 853.22 mGy-cm (SD, 281.84) and 12.8 mSv (SD, 4.23), respectively. The differences between SECT and DECT increased as the patient’s effective diameter increased (p < 0.001). Noise levels in the liver (20 vs 18.5), IVC (22.2 vs 19.5), RP fat (21 vs 18.9) and aorta (24.3 vs 22.5) were greater on DE compared to SE exams (p<0.05). In the phantom study, the CTDIvol at equal image noise was less for DECT vs. SECT by 11-15% depending on the phantom size. These results are consistent with the clinical study, especially after accounting for the difference in noise between DECT and SECT.

Abdominal DECT had a significantly lower radiation dose at similar or equal noise levels compared to SECT in both clinical and phantom studies.

These results are critical for implementation of DECT of the abdomen in clinical practice, as they show that this technique does not necessarily come at the expense of higher radiation doses.

Purysko, A, Primak, A, Baker, M, Obuchowski, N, Remer, E, Dong, F, John, B, Karim, W, Herts, B, Comparison of Radiation Dose and Noise Levels From Single Energy and Dual Energy Computed Tomography Examinations of the Abdomen In Vivo and in Phantom Experiments.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14001922.html