Adopting low dose CT in evaluating renal calculi-progress from 2008-18 in a large UK tertiary hospital

Background: Computed tomography (CT) of the urinary tract is a commonly performed investigation and it is crucial to adhere to low dose protocols to avoid unnecessary radiation burden. Aims: To review the adoption of low-dose techniques over time, defined as a dose length product (DLP) < 200mGy.cm, in a large teaching hospital over three locations with 12 CT scanners. Methods: Data were obtained from the radiology information system for exams completed under the coding for unenhanced CT evaluation for renal calculi between 14 Feb 2008 and 31 December 2018. Examinations where the DLP was not correctly recorded, was below 40mGy.cm, or where the equipment used could not be identified were excluded. The distribution of doses and the median DLP per scanner was calculated. Results: In all, 20,080 studies were available across 12 CT scanners in the 10- year period. The average Median DLP has reduced from 501mGy.cm in 2008 to 178mGy.cm in 2018. Conclusions: Improvements in CT technology and implementation of low-dose protocols have resulted in significantly lower doses for evaluation of kidney stones since 2008. Although this study demonstrates significant variation between scanners, the overall adoption of low dose techniques is excellent. Level of evidence: Not applicable