[Research on the shielding evaluation method for medical X-ray imaging facilities]

The purpose of this study was to verify the shielding evaluation method for medical X-ray imaging facilities in Report No. 147 of the National Council on Radiation Protection and Measurements (NCRP). We investigated the concept of radiation protection and the major revised point in Report No. 147. The goal of radiation protection in Report No. 147 was compared with that in Japan. Using the data of the Imaging Performance Assessment of CT scanners (ImPACT) 2006 and the latest pre-installation manuals of several manufactures for different computed tomography (CT) scanner models, we verified the shielding method for CT installations. The concept of radiation protection in Report No. 147 was based on the recommendation of the International Commission on Radiological Protection (ICRP) Publication 60. On the shielding method for CT units, compared with the CT scatter fraction for the body phantom in Report No. 147 was approximately 10% less than the results of the computation. In conclusion, we should note the use of the CT scatter fraction for the body phantom provided by Report No. 147; however, it is possible to apply the fundamental concept of the shielding evaluation in Report No. 147 to the shielding evaluation method in Japan.