Local diagnostic reference level based on size-specific dose estimates: Assessment of pediatric abdominal/pelvic computed tomography at a Japanese national children’s hospital

Background A child’s body size is not accurately reflected by volume CT dose index (CTDI vol ) and dose–length product (DLP). Size-specific dose estimation (SSDE) was introduced recently as a new index of radiation dose. However, it has not yet been established as a diagnostic reference level (DRL). Objective To calculate the SSDE of abdominal/pelvic CT and compare the SSDE with CTDI vol . To calculate the DRLs of CTDI vol and SSDE. Our hypotheses are: SSDE values will be greater than CTDI vol , and our DRL will be smaller than the known DRLs of other countries. Materials and methods The CTDI vol and DLP of 117 children who underwent abdominal/pelvic CT were collected retrospectively. The SSDE was calculated from the sum of the lateral and anteroposterior diameters. The relationships between body weight and effective diameter and between effective diameter and CTDI vol /SSDE were compared. Further, the local DRL was compared with the DRLs of other countries. Results Body weight and effective diameter and effective diameter and SSDE were positively correlated. In children ages 1, 5 and 10 years, the SSDE is closer to the exposure dose of CTDI vol for the 16-cm phantom, while in children ages 15 years, the SSDE falls between CTDI vol for the 16-cm phantom and that for the 32-cm phantom. The local DRL was lower than those of other countries. Conclusion With SSDE, the radiation dose increased with increasing body weight. Since SSDE takes body size into account, it proved to be a useful indicator for estimating the exposure dose.