[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.

Introduction of the targeted alpha therapy (with Radium-223) into clinical practice in Japan: learnings and implementation.

Radium-223 dichloride (Ra-223) is the first targeted alpha therapy approved for the treatment of patients with castration-resistant prostate cancer (CRPC) with bone metastasis. Ra-223 improved overall survival in the international Phase III ALSYMPCA (ALpharadin in SYMPtomatic Prostate Cancer) study. Ra-223 was also demonstrated to be efficacious and safe in Japanese patients in Phase I and Phase II clinical trials. Ra-223 was approved in Japan for the treatment of patients with CRPC with bone metastasis in 2016. The conduct of clinical studies with radionuclides in Japan involves mandatory compliance with local and international regulations pertaining to radiation protection. Without an existing Japanese framework for the handling of α-emitters in clinical practice, we encountered many challenges to initiate the clinical studies. Therefore, we started on a project to determine best practice on the use of Ra-223 in clinical studies. For this project, we evaluated all applicable laws and regulations on the use of radionuclides in medicine, then examined whether and how the α-emitter Ra-223 could meet these legal and regulatory requirements. This included how to approach the matter of discharging patients administered Ra-223 from hospital and radiation protection for caregivers, general public and medical care professionals. Subsequently, we published Manual on the proper use of radium-223 dichloride injection in clinical trials that summarized the essential requirements necessary to allow the safe use of Ra-223 in clinical trials in Japan. As the result, we succeeded in demonstrating that clinical trials of an α-emitter, Ra-223, could be implemented safely in Japan. Our experience in Japan highlights the importance of a multidisciplinary team-based approach and continued professional training in a clinical setting. This article summarizes the rationale behind the development of this manual. We hope that by sharing our experience and information, we can help other countries considering the introduction of radionuclides for clinical use, and support the future development of radionuclide therapies in a safe and effective manner.

Manual on the proper use of yttrium-90-labeled anti-P-cadherin antibody injection for radionuclide therapy in clinical trials.

We present the guideline for use of yttrium-90-labeled anti-P-cadherin antibody injection for radionuclide therapy in clinical trials on the basis of radiation safety issues in Japan. This guideline was prepared by a study supported by the Ministry of Health, Labour, and Welfare, and approved by the Japanese Society of Nuclear Medicine. Treatment using yttrium-90-labeled anti-P-cadherin antibody injection in Japan should be carried out according to this guideline. Although this guideline is applied in Japan, the issues for radiation protection shown here are considered internationally useful as well. Only the original Japanese version is the formal document.

Manual on the proper use of lutetium-177-labeled somatostatin analogue (Lu-177-DOTA-TATE) injectable in radionuclide therapy (2nd ed.).

Here we present the guideline for the treatment of neuroendocrine tumors using Lu-177-DOTA-TATE on the basis of radiation safety aspects in Japan. This guideline was prepared by a study supported by Ministry of Health, Labour, and Welfare, and approved by Japanese Society of Nuclear Medicine. Lu-177-DOTA-TATE treatment in Japan should be carried out according to this guideline. Although this guideline is applied in Japan, the issues for radiation protection shown in this guideline are considered internationally useful as well. Only the original Japanese version is the formal document.

[Investigation of radioactivity measurement of medical radioactive waste].

To explore the possibility of which medical radioactive wastes could be disposed as general wastes after keeping them a certain period of time and confirming that their radioactivity reach a background level (BGL), we made a survey of these wastes in several nuclear medicine facilities. The radioactive wastes were collected for one week, packed in a box according to its half-life, and measured its radioactivity by scintillation survey meter with time. Some wastes could reach a BGL within 10 times of half-life, but 19% of the short half-life group (group 1) including 99mTc and 123I, and 8% of the middle half-life group (group 2) including 67Ga, (111)In, and 201Tl did not reach a BGL within 20 times of half-life. A reason for delaying the time of reaching a BGL might be partially attributed to high initial radiation dose rate or heavy package weight. However, mixing with the nuclides of longer half-life was estimated to be the biggest factor affecting this result. When disposing medical radioactive wastes as general wastes, it is necessary to avoid mixing with radionuclide of longer half-life and confirm that it reaches a BGL by actual measurement.

Thyroid remnant ablation using 1,110 MBq of I-131 after total thyroidectomy: regulatory considerations on release of patients after unsealed radioiodine therapy.

OBJECTIVES: This study was undertaken to measure the radiation exposure level of caregivers following outpatient NaI (I-131) 1,110 MBq therapy for remnant thyroid ablation after total thyroidectomy in patients with differentiated thyroid cancer, and to evaluate the influence of activities of daily living on radiation exposure level, with the goal of proposing an optimum method of I-131 therapy. METHODS: The study included 37 patients with differentiated thyroid cancer, who had undergone total thyroidectomy and received outpatient based remnant thyroid ablation using NaI (I-131) 1,110 MBq, who were satisfying the following requirements: (1) patients who have no evidence of distant metastases, (2) whose living environments were appropriate for outpatient I-131 (1,110 MBq) therapy, and (3) patients who gave written informed consent. The dose rate at a distance of 1 m from the body surface of the patient at the moment of release was measured using survey meters of the GM type or ionization chamber type. The dose level for the caregiver was measured with a personal dosimeter in all cases. RESULTS: The dose rate at a distance of 1 m from the patient's body surface 1 h after I-131 administration was in the range of 29-115 µSv/h (mean 63.8 µSv/h). The 7-day cumulative effective dose of caregivers was 0.11 ± 0.08 mSv, on an average, in 34 dosimeters. In 31 of 34 dosimeters, cumulative effective dose of caregivers was below 0.2 mSv. Dose levels exceeding 0.2 mSv were recorded in 3 cases (0.21, 0.35 and 0.43 mSv in one case each). These results suggest that the exposure level of family members (caregiver and others) was minimal and is lower than the radiation levels affecting human environments. CONCLUSION: Outpatient-based remnant thyroid ablation with I-131 (1,110 MBq) performed after total thyroidectomy in patients with differentiated thyroid cancer is safe if applied in accordance with the appropriate supervision and guidance by experts with certain qualifications.