[A Novel Dose Index for Effective Dose Estimation in Chest and Abdomen-Pelvis CT Examinations: Size-specific DLP]

The effective dose in CT examinations is typically estimated by multiplying the dose-length product (DLP) by a conversion coefficient. This study proposes a novel dose index, the size-specific dose-length product (SS-DLP), which incorporates patient body size and evaluates its utility compared to the conventional DLP.

SS-DLP was defined as a dose index calculated by multiplying the mean size-specific dose estimate (SSDE) by the scan length. SSDE, which takes patient body size into consideration, serves as a key factor in this calculation. We analyzed data from 95 chest and 89 abdomen-pelvis CT scans of adult patients, with effective doses simulated using the WAZA-ARI v2 dose calculation software. Regression equations were developed to estimate effective dose based on both DLP and SS-DLP, with estimation accuracy evaluated using the coefficient of determination (R²), mean absolute error (MAE), and Bland-Altman plots. Additionally, the relationship between BMI and estimation error was evaluated.

Compared to conventional DLP, SS-DLP improved R² and reduced MAE. Bland-Altman plots showed a narrower error range and a reduction in mean error. Additionally, the use of SS-DLP mitigated BMI-related discrepancies in estimation error, demonstrating reduced dependency on patient body size. Regression equations based on SS-DLP also exhibited consistent conversion coefficients across different scan regions, highlighting its adaptability to variations in scan areas and ranges.

SS-DLP is a promising dose index that enhances the accuracy of effective dose estimation in CT examinations. By accounting for patient body size, SS-DLP facilitates more precise dose management and has the potential to improve radiation exposure management practices.