MIRD 양식화 임산부 팬텀 기반 PHITS-MCNPX 교차비교: 복부 엑스선(X-ray) 검사 태아 흡수선량 평가

초록

In diagnostic radiological examinations of pregnant women, accurate fetal absorbed dose assessment is an important challenge in radiation protection. Direct measurement is ethically impractical; therefore, Monte Carlo (MC) simulation serves as the standard evaluation method. This study used the Particle and Heavy Ion Transport code System (PHITS) version 3.36 to implement Medical Internal Radiation Dose (MIRD)-type pregnant stylized phantoms of Stabin 1995 (6-month and 9-month gestational ages) and calculated the fetal absorbed dose ratio (D_skel/D_soft) under abdominal anterior-posterior (AP) X-ray examination conditions (85 kVp, source-to-detector distance 100 cm). Geometric accuracy of the 9-month phantom was independently verified via PHITS [T-Volume] MC volume integration, with all of its cell volumes agreeing within 0.52% of Stabin 1995 reference values. Cross-comparison against the Monte Carlo N-Particle eXtended (MCNPX) 2.5.0-based results of Woo et al. 2020 yielded a difference of −3.15% at 6 months, within the statistical uncertainty of the reference value, and +10.32% at 9 months, which exceeded the 95% contrast interval of ±8.36% derived from the uncertainty of the reference value itself. These results support the feasibility of applying PHITS to photon transport in MIRD-type pregnant phantoms and provide a basis for adopting PHITS in future studies using the International Commission on Radiological Protection (ICRP) Mesh-type Reference Computational Phantom for Pregnancy (MRCP), within the scope of a single reference study, a single examination condition, and two gestational ages.

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