Optimizing z-axis coverage in computed tomography scans of the kidney, ureters, and bladder via standard operating procedures: a clinical audit report

Internal audit at our radiology department identified variability in doses for computed tomography scans of the kidney, ureters, and bladder (CT KUB). This prompted a revision of the standard operating procedure (SOP) using less ambiguous osseous anatomical landmarks, namely the T10 vertebra endplate and inferior margin of the pubic symphysis. The objective of this study was to evaluate the use and effectiveness of SOPs as a means of scan length optimization and dose reduction. In total 247 CT-KUB scans were retrospectively analyzed in terms of compliance with the new osseous anatomical landmarks, and in terms of total scan length and dose-length product (DLP). The intervention comprised of two phases: (1) implementation of a new SOP with less ambiguous osseous anatomical landmarks, (2) amendment of the SOP, to assist identification of T10 endplate, by means of a sagittal scout view.This phased approach to SOP adjustments produced significant reduction in over-scanning. Excess over-scanning was reduced in the first phase, with a reduction of 14% in scan length and 32% in DLP. In the second phase, scan length was further reduced by 7%. Overall, scan length decreased by 20% and DLP by 55%.