Investigation of the Relationship between Body Parameters and Current‑time Product in Kidney-Ureter-Bladder Digital Radiography

Background: In radiography, determining exposure parameters based on body parameters is essential to achieve adequate image quality. However, the relationship between body parameters and the current-time product (mAs) in kidney-ureter-bladder (KUB) radiography has not been fully explored. Therefore, this study aimed to investigate the relationship between body parameters and mAs using KUB digital radiography. Materials and Methods: This study consisted of both phantom and human experiments. Initially, an anthropomorphic phantom was positioned at various locations to assess the impact of positioning variations on mAs during KUB radiography using the automatic exposure control (AEC) technique. In the human experiment, a total of 139 and 354 subjects who underwent regular KUB radiography using two digital radiographic systems were enrolled. Body height (H), weight (W), body mass index (BMI), exposure index (EI), and X-ray images were collected from each participant in both groups. In addition, abdominal thickness (T) was measured in Group 1. Curve fitting was performed using three curve models to understand the relationship between body parameters and mAs, and the goodness of fit (R^2) was compared between the models and body parameters. Results: In the phantom study, positioning variations resulted in a difference of 1.57 and 1.32 times between the maximum and minimum mAs values in KUB digital radiography for two systems when using the AEC technique. In the human study, the comparison of curve fitting revealed that W/H and BMI demonstrated higher R^2 values compared to the other body parameters (T and W) across the three curve models. In addition, the second-order polynomial model with W/H as the predictor for mAs exhibited the highest R^2 values (0.6189 and 0.4731 for Group 1 and 2, respectively) among all curve models. Conclusions: We concluded that W/H is a more suitable body parameter than other parameters for predicting mAs in KUB radiography.