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.