Evaluation of Size-Specific Dose Estimates in CT KUB Scans: Comparison of Central-Slice and Full-Slices Methods Using Water-Equivalent and Effective Diameters

Objectives To evaluate the Size-Specific Dose Estimates (SSDE) in adult patients undergoing kidneys, ureters, and bladder (CT KUB) scans using two approaches: water-equivalent diameter (Dw) and effective diameter (Deff). The study also aimed to assess the accuracy of using a single central image slice for SSDE estimation. Methodology Ethical approval was obtained to collect patient data from a local hospital. CT images from 203 adult patients were retrieved and processed using IndoseCT software to calculate patient size metrics and corresponding SSDE values. Results SSDE values calculated using the Dw,mean and Deff,mean were comparable: 10.3 ± 2.9 mGy and 10.2 ± 2.9 mGy, respectively. When using a single central slice, the mean percentage differences were −1.8 ± 3.9% for Dw and −1.1 ± 4.6% for Deff, with all values falling within ±11%. A strong correlation was observed between SSDE values derived from single-slice and full-slice measurements (R2 > 0.97), showing slightly better agreement for Dw. Conclusion While Dw offers a more accurate estimation of patient size, the minimal differences observed suggest that Deff is a suitable alternative when Dw specific tools are unavailable. Additionally, using a single central slice is a practical and efficient method to estimate SSDE, significantly reducing computational demands. Advances in Knowledge This study provides clinical validation that SSDE can be reliably estimated using a single-slice method in CT KUB examinations, offering a substantial reduction in processing time. It also demonstrates that Deff is a viable substitute for Dw when access to advanced imaging analysis tools is limited.