The questionnaire survey was conducted in 2020 to investigate the working conditions of qualified medical physicists in Japan. We developed a web-based system for administering the questionnaire and surveyed 1,228 qualified medical physicists. The number of received responses was 405. We summarized the results of the survey by job category. The obtained results showed that most of the people working as certified medical physicists met the following conditions: (1) position of healthcare occupation, (2) direct supervisor is a medical doctor or a medical physicist, (3) licensed or passed an examination for a Class I Radiation Protection Supervisor, (4) without the license of professional radiotherapy technologist, (5) master’s or doctor’s degree, (6) being assigned to the section that is different from the radiological technologist section. The average annual salary was approximately 600,000 yen higher for those employed as medical physicists than for those employed as radiotherapy technologists. The percentage of work performed by a certified medical physicist in radiation therapy greatly varies depending on whether the physicist is dedicated to treatment planning and equipment quality control. Alternatively, the proportion of the true duties of medical physicists in charge of radiation therapy, as considered by qualified medical physicists in radiation therapy, was the same regardless of whether they were working full-time or not. The results of this survey updated the working status of certified medical physicists in Japan. We will continue to conduct the survey periodically and update the information to contribute to the improvement of the working conditions of medical physicists and policy recommendations.

Boron neutron capture therapy (BNCT) is a radiation therapy that uses charged particles produced by a nuclear reaction between thermal neutrons and ¹⁰B. A high-intensity neutron source is required to perform BNCT, and it is important to understand the behavior of neutrons. Since BNCT using accelerators has been approved as a medical device, the number of treatment facilities is expected to increase in the future. This article describes the basic knowledge required to understand BNCT in clinical practice, including neutron generation and material interactions, as well as radiation protection considerations specific to BNCT.

Photo neutrons are generated from high-energy medical X-ray linacs via photo-nuclear reactions with the materials of target and collimator as well as therapeutic X-rays. Such photo neutrons sometimes make unwanted influences and are not negligible for the aspects of radiation protection and radiation control. In this article, fundamental principle of such photo-neutron generation is briefly explained. The side effects induced by the photo neutrons are summarized. In addition, some techniques of the detection and measurement of photo neutrons are introduced.

Particle therapy uses high-energy charged particles, which cause nuclear reactions with a beam limiting device and a patient, resulting in the generation of high-energy secondary neutrons. These secondary neutrons cause low-dose exposure to organs far from the treatment target, and have a high biological effect due to their energy characteristics, which may cause of secondary cancers after radiotherapy. This article describes the neutron generation mechanism (cross section, and energy spectrum), interaction with the secondary neutron source (beam limiting device, and the patient), measurement of neutrons, and considerations for radiation protection of patients from secondary neutrons, generated by proton and carbon beam radiation therapy.

The Tohoku-Pacific Ocean Earthquake that occurred on March 11, 2011 and the resulting tsunami caused the loss of many people and extensive damage in a wide area. Among the anthropogenic radionuclides dispersed from the Fukushima Daiichi Nuclear Power Plant, ¹³⁴Cs and ¹³⁷Cs have very long half-lives of approximately 2 years and 30 years, respectively, and there are concerns about their uptake into soil and living things. This paper describes a study conducted by the authors’ group on radiocesium activity concentrations in the environment.