[Comparison of shielding calculations for diagnostic X-ray equipment]

Radiation is controlled by the recent revision of the Enforcement Regulations of the Medical Service Law. Law No. 188 prescribes X-ray data for estimating effective dose in the controlled area of a medical facility. For X-ray data such as kerma in air, transmission data are based on NCRP. We compared various X-ray data, and NCRP and Simpkin were compared with law No. 188. Leakage effective doses in a general-purpose radiography room, fluoroscopy room, and X-ray CT room were calculated. All three calculations were below the dose limit for controlled areas, 1.3 mSv/3 months. In the general-purpose radiography room (including fluoroscopy), NCRP and Simpkin underestimated from 1/3 to 1/2 in comparison with law No. 188. In the X-ray CT room, NCRP and Simpkin showed underestimates from 1/2 to 2/3 compared with law No. 188. There were no significant differences between law No. 188, NCRP, and Simpkin, but significant differences were found for individual numerical values. A need for the re-examination of basic data was suggested by the above findings.