We verified whether the use capacity of nuclides possessed by the Designated Cancer Care Hospitals that provide nuclear medicine therapy is sufficient for the number of patients who may be eligible for nuclear medicine therapy. Regarding to ¹⁷⁷Lu, relevant hospitals may have the capacity to handle it to some extent, although it is insufficient in the future, whereas it is difficult to introduce ²²⁵Ac into the current equipment and facilities installed in those hospitals. In addition, we verified whether the distribution of hospitals providing nuclear medicine therapy nationwide is in a state of uniform accessibility. Although there seems to be no problem in terms of conversion per 100,000 population, there are concerns about the burden on hospitals that play a central role in nuclear medicine therapy in rural areas that contribute to uniform accessibility in response to the spread of nuclear medicine therapy that is expected in the future, and it is necessary to take measures to improve the capacity of hospitals as soon as possible.

Exposure to ionizing radiation results in the generation of free radical, such as anion radicals, cation radicals, and neutral radicals, that can induce biological damage. In this report, we studied the antioxidant properties and radioprotective effects of extracts from Pleurotus sajor-caju on wild-type yeast cells. Phenolics and flavonoids are bioactive compounds, known as antioxidants, that have gained interest among researchers due to their benefits for human health. The total phenolic content (TPC) of the extracts was determined by Folin–Ciocalteu assay and the total flavonoid content (TFC) was determined by aluminum chloride assay. The antioxidant activities were determined by performing 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). The radioprotective effects of the extracts on yeast cells exposed to γ-rays were evaluated based on the survival rate (SR) and mutation frequency. The percentage of surviving yeast cells increased while those undergoing mutation decreased after irradiation in the presence of extracts, indicating that bioactive compounds from the extract of P. sajor-caju can reduce the damage induced by γ-rays. Thus, bioactive compounds from the extracts of P. sajor-caju have the potential to minimize or ameliorate the effects of ionizing radiation.

We developed a system that analyzes camera-captured images using a deep-learning model to estimate the radiopharmaceutical type that radiographers hold in their hands and displays a hologram using mixed reality. A 10-fold cross-validation was performed using three deep-learning models. The accuracy exceeded 99％ for all models. Real-time radiopharmaceutical analysis for preventing misadministration and displaying holograms of the results proved feasible.

The history of radiation and nuclear sciences has been followed step by step from the discovery of X-rays in 1895 to the beginning of World War II, surveying original papers and materials. It can be seen that our modern knowledge written in textbooks is the product of pioneers’ tremendous curiosity and efforts, together with some serendipity.

This study aims to propose a reasonable radiation management framework for naturally occurring radioactive materials (NORM) by comparing NORM handling practice with the management of radioactive materials in radiation facilities. For the concept of the work area, we adopted the idea of Supervised area instead of Controlled area with strict control and showed an example of its reasonable application. Persons who occasionally engage in tasks related to NORM might be categorized as public due to their lack of expertise in radiation. However, considering their occupational characteristics, we propose an acceptable safety dose criterion of 1–5 mSv/y.

Practice of nuclear medicine (NM) in Japan started in 1950 when radioisotopes (RIs) were imported from the U.S.A. and Japan Radioisotope Association (JRIA) launched with the purpose for bulk buying and distribution of RIs to each user. The author has experienced the nuclear medicine practices since its dawn to present. The purpose of this historical review is to follow tracks of nuclear cardiology in Japan as seen by the author. The nation-wide survey of nuclear medicine practice in Japan which was conducted by a subcommittee of JRIA tells us numbers of examinations, instruments and radiopharmaceuticals used for cardiac imaging and their temporal changes. The author describes his experiences with cardiac imaging in NM and its chronological changes in accordance with developments of imaging devices and radiopharmaceuticals used. The author believes the new developments in instrumentations and radiopharmaceuticals together with multi-disciplinary cooperation will facilitate nuclear cardiology and contribute to welfare of patients.

This paper summarizes fundamental concepts on risk communication in nuclear and radiation fields based on the experiences of experts who have engaged in risk communication in those fields. Previous studies and background information on risk communication are noted for further understanding.

The scientific evidence for the medical application of thoron, an isotope of radon, remains to be insufficient internationally. In addition, the ICRP reported that thoron progeny nuclides show higher radiobiological effects than radon progeny nuclides. For this reason, we outlined some of the research results that we have so far reported the biological effects of thoron and comparison with those of radon. As a result, we were able to suggest that, like radon ingestion, thoron ingestion enhances antioxidant function through physiological stimulation caused by the generation of trace amounts of active oxygen, thereby alleviating the symptoms of oxidative stress-related diseases. In addition, we found that thoron appears in a range with a lower optimal inhalation concentration than radon due to the difference in radioactivity characteristics, which is consistent with the ICRP report.

Photosynthates are translocated into the plant tissue mainly in the form of sucrose. To determine whether there are differences in translocation between internally produced photosynthates and externally applied sucrose, ¹⁴CO₂ or ¹⁴C-sucrose was supplied to specific soybean leaves and the ¹⁴C activity distribution was compared. The distribution rates were almost the same among the above-ground tissues, but different in the roots. Care should be taken when using ¹⁴C-sucrose as a photosynthate, especially when focusing on roots.

Microtubules in the cytoplasm play an important role in a number of cellular processes. Radiation-induced impacts on microtubules, composed of αβ-tubulin heterodimers, remain to be determined. In this study, to clarify how tubulins damaged by radiation exposure affect the polymerization reaction, with a fluorescent tubulin polymerization assay kit, we investigated the interactions of X-ray exposed tubulins with intact ones during in vitro polymerization reactions. Our proposed approach may shed light on the emerging role of tubulin damage control for understanding how cellular functions are maintained after exposure to radiation.

Astatine is an alpha-emitting radionuclide that can be produced using cyclotrons. We have successfully developed a PSMA-targeted alpha therapy agent labeled with astatine ([²¹¹At]PSMA-5) for the treatment of refractory prostate cancer. In tumor-bearing mouse models, a single administration of [²¹¹At]PSMA-5 (0.4 MBq) demonstrated excellent antitumor effects. In June 2024, we commenced a phase I investigator-initiated clinical trial (first-in-human). Furthermore, we completed planned dosing for 11 patients in an ongoing phase I investigator-initiated clinical trial using sodium astatide for refractory thyroid cancer. I hope that astatine-based drug discovery from Japan will become a groundbreaking cancer therapy in the world.

Using National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) Open Data, we investigated the current status of insurance covered PET examinations in FY2022. The number of examinations based on sex and age showed different trends for each drug and device. The number of positron emission tomography (PET) examinations also differed from prefecture to prefecture. Comparing the number of examinations per month in FY2020–2022, during the Coronavirus disease 2019 (COVID-19) pandemic, to FY 2019, a decrease of up to 20％ was observed in May 2020, at the early stages of the pandemic.

According to the revision of act on the regulation of radioisotopes in 2023, inspection and calibration of radiation measuring instruments has been obligated. In this study, inspection methods for survey meters using commercially available reagents containing natural radionuclides as a radiation source was investigated. As a result of shielding test, the linearity and reproducibility of attenuation was confirmed. Furthermore, correlation of radiation counts with concentration of ⁴⁰K and ⁸⁷Rb radioactivity was founded. Based on these results, a simple inspection method for survey meters was established.

To sterilize the bacteria on the surface of the woodblocks, low energy X-rays of 150 kV were used to irradiate them without using filters, which was six times faster than general X-ray irradiation methods. Insect damage to the woodblocks could be distinguished from cracks and physical destruction only by visual inspection and simple X-ray radiography. These techniques were manualized and transferred to Vietnam. At that time, 0.5 mGy of X-rays irradiated within the baggage inspection and 9 µSv of cosmic radiation of travel routes had no effect on the film dosimeter and X-ray film.

The author is developing and conducting demonstration tests of integrated Radiation Imaging System (iRIS), which visualizes radioactive contamination distribution on a 3-D map, for the purpose of contributing to the decommissioning of the Fukushima Daiichi Nuclear Power Station. This paper describes the principle of the system, the results of the demonstration tests, and its applications.

Simplification of the measurement method for biobased carbon content was achieved by applying CO₂ capture with ethylenediamine as a pretreatment for liquid scintillation counting (LSC) measurement. The biobased carbon content can be determined by a new method based on comparison between radiocarbon count rates of carbamic acid derivatives synthesized with reference materials of biomass carbon and petroleum carbon, although LSC measurements were performed for radiocarbon in solid-state carbamic acid derivative. Cross-checking with the Accelerator Mass Spectrometry (AMS) method confirmed that this method is sufficiently accurate, so it is expected to be used as a screening method.