Cameron Hope Williams BA, Presenter: Nothing to Disclose

Ana Maria Gaca MD, Abstract Co-Author: Nothing to Disclose

Caroline Laurens Hollingsworth MD, Abstract Co-Author: Nothing to Disclose

Charles M. Maxfield MD, Abstract Co-Author: Nothing to Disclose

Xiang Li PhD, Abstract Co-Author: Research grant, General Electric Company

Ehsan Samei PhD, Abstract Co-Author: Advisory Board, Ion Beam Applications, SA Consultant, Siemens AG Research grant, Siemens AG Research grant, General Electric Company Research grant, Carestream Health, Inc

Donald P. Frush MD, Abstract Co-Author: Nothing to Disclose

CT is increasingly used in evaluation for possible appendicitis in children. Our purpose was to compare conventional and reduced-mA CT in the evaluation for acute appendicitis.

Validated (based on noise magnitude and texture) mA-reduction software was used to simulate 50% and 75% mA reduction in 60 (22M, 38F; <18 yrs) CT examinations (64-slice, GE VCT; weight-based protocols; CTDIvol in general under 11.4 mGy*cm, well below DRL for ACR CT accreditation) performed for possible appendicitis, resulting in 180 image sets. Three blinded, experienced CAQ pediatric radiologists interpreted the randomized conventional and simulated-mA studies for the normal appendix, appendicitis (5-point scale; 1=definitely absent, 3=indeterminate, 5=definitely present), alternate diagnoses, and overall image quality (5-point scale; 1=non-diagnostic, 5=excellent).

For conventional exams, the normal appendix was identified in 67% of scans, compared with 60% in the 50% (p=0.19) and 51% in the 75% (p=0.002) mA-reduction groups. Appendicitis was identified in 22%, 21%, 21% of exams, respectively (NS). Alternate diagnoses were detected in 43 of standard, 45 of 50% reduction, and 32 of 75% reduction scans. Reader agreement for the evaluation of appendicitis for the standard, 50% and 75% mA-reduction groups was 76%, 61%, and 51%, respectively. Overall reader confidence (mean deviation from indeterminate) for the standard, 50% and 75% mA-reduction groups was 1.81, 1.66, and 1.38; overall reader assessment of image quality was 4.37, 3.44, and 2.31 (p<0.01 for all comparisons).

Simulated mA-reduction provides for systematic radiation-free risk assessment for diagnostic thresholds, including r/o appendicitis. Results indicate conventional conservative dose age-based techniques can be reduced by at least 50% maintaining diagnostic quality, despite a decrease in reader subjective assessment of image quality. The dose reduction can be applied to risk models: e.g., in a 10-year-old boy and girl, the LAR cancer risk (in cases per 1,000) can be reduced from 0.4 to 0.2 and 0.5 to 0.25, respectively, with 50% mA reduction.

For pediatric CT, systematic assessment of dose (and risk) using novel dose-reduction technology provides guidelines for clinical practice.

Williams, C, Gaca, A, Hollingsworth, C, Maxfield, C, Li, X, Samei, E, Frush, D, Comparison of Conventional and Simulated Reduced-mA MDCT for Evaluation of Appendicitis in the Pediatric Population.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11003358.html