Institutional CT Dose Reduction: A Retrospective Evaluation of Dose Indices from 2015-2024
Abstract
Purpose
The increased attention on radiation risks and dose reduction in CT imaging presents opportunities for the presentation and discussion of institutional dose trends and factors contributing to change. The objective of this work is to analyze dose indices (CTDIvol and DLP) from a multi-site and multi-scanner institution over 10 years.
Methods
Data from a radiation dose index monitoring system (Radimetrics, Bayer) were used to analyze diagnostic CT examinations from January 2015 to December 2024. Exams were stratified by procedure, and the ten most used procedures were identified. Pearson correlation was calculated between time, defined as months since January 2015, and monthly median dose indices. Procedures with significant decreases in both CTDIvol and DLP were further stratified by scanner model, and model-specific monthly median dose indices were calculated. To investigate the relationship between dose reductions and image quality, annual ACR phantom images were retrieved for scanners in 2015 and 2024; low contrast detectability was calculated using Module 2 and CTPro software.
Results
From 2015-2024, 718,531 exams (236,110 patients) were performed on 19 scanners (nine models). Pearson correlation results show decreases in both dose indices for five of the ten most used procedures across all scanners and the effect of reducing multiphase contrast exams. Model-specific monthly median dose indices demonstrate the dose reduction capabilities of new models. Additionally, the detectability index of low contrast test objects were generally higher when scanned at lower doses on new models in 2024 than when scanned at higher doses on older models in 2015, indicating that dose reductions due to upgrades from 2015-2024 did not compromise this measure of image quality.
Conclusion
A retrospective 10-year review of CT exams demonstrated decreasing dose indices across multiple diagnostic procedures that coincided with scanner replacements and upgrades, the reduction in multiphase protocol usage, and ongoing protocol optimization efforts.