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. 2023 Nov 21;64(6):962-966.
doi: 10.1093/jrr/rrad063.

Current status and issues with the dosimetric assay of iodine-125 seed sources at medical facilities in Japan: a questionnaire-based survey†

Toru Kojima  1 , Shinji Kawamura  2 , Yuki Otani  3 , Takashi Hanada  4 , Yuichiro Wakitani  5 , Kenta Naniwa  6 , Atsunori Yorozu  7 , Hitoshi Ikushima  8 , Takushi Dokiya  9
Affiliations

Current status and issues with the dosimetric assay of iodine-125 seed sources at medical facilities in Japan: a questionnaire-based survey†

Toru Kojima et al. J Radiat Res. .

Abstract

In conducting dosimetric assays of seed sources containing iodine-125 (125I), several major guidelines require the medical physicist to verify the source strength before patient treatment. Japanese guidelines do not mandate dosimetric assays at medical facilities, but since 2017, three incidents have occurred in Japan wherein seeds with incorrect strengths were delivered to medical facilities. Therefore, this study aimed to survey the current situation and any barriers to conducting the dosimetric assay of iodine-125 seeds at medical facilities in Japan. We conducted a questionnaire-based survey from December 2020 to April 2021, to examine whether seed assay and verification of the number of seeds delivered were being performed. We found that only 9 facilities (16%) performed seed assay and 28 (52%) verified the number of seeds. None of the facilities used an assay method that ensured traceability. The reasons for not performing an assay were divided into two categories: lack of resources and legal issues. Lack of resources included lack of instruments, lack of knowledge of assay methods, shorthand, or all of the above, whereas legal issues included the inability to resterilize iodine-125 seeds distributed in Japan and/or purchase seeds dedicated to the assay. Dosimetric assays, including simple methods, are effective in detecting calibration date errors and non-radioactive seeds. The study findings suggest that familiarization of medical personnel with these assay methods and investigation of the associated costs of labor and equipment should be recommended, as these measures will lead to medical reimbursement for quality assurance.

Keywords: iodine-125; low-dose-rate brachytherapy; low-energy source; prostate cancer; seed assay.

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Conflict of interest statement

The authors have no conflicts of interest to disclose.

Figures

Fig. 1
Fig. 1
Numbers of iodine-125 seed brachytherapy procedures in fiscal year 2019 at the responding facilities (n = 67).
Fig. 2
Fig. 2
Percentage of facilities performing seed dosimetric assays and checking the number of seeds delivered (n = 67).
See this image and copyright information in PMC

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