Semiconductor radiation detectors with high energy resolution are used in various fields such as particle and nuclear physics experiment. The inorganic semiconductor detectors have problems, which are inflexible, expensive, and difficult to fabricate a large detector. To solve the problems, the new radiation detectors are developed using conductive polymers without crystal structures. The hybrid sensors of prototype were fabricated by combining an n-type titanium oxide (TiO₂) semiconductor as an additive with p-type polyaniline. In this paper, we measured the detection efficiency of the newly developed semiconductor radiation sensors.

Neutron capture therapy (NCT) uses secondary particle to treat tumor. Boron has been applied to NCT in clinics, and gadolinium has also attracted the attention. Our group attempted a new candidate element, rhodium, because of its advantages, such as 100% natural abundance, long range (beta ray), neutron cross-section peak, and fitness to accelerator-based neutrons. To reduce toxicity and increase tumor accumulation, rhodium encapsulated liposomes (Rh-Lip) were synthesized. After 24 h exposure to rhodium solution, the cell viability increased to 90% when the rhodium concentration was diluted to 0.063 mg/mL; in contrast, it was up to 90% when rhodium concentration was diluted to 0.25 mg/mL in the Rh-Lip group. Moreover, in the Rh-Lip group, 387.3 ppm rhodium remained in the tumor 3 h after administration, but only 42.6 ppm remained in the rhodium solution group. After neutron irradiation, Rh-Lip showed a slower tumor growth rate and damage to tumor cells from pathological analysis, suggesting that rhodium is a potential element for NCT.

Heavy ion beam radiotherapy has superior therapeutic benefits because of its higher relative biological effectiveness and reduced oxygen enhancement ratio compared with low LET radiation. However, the precise measurement of dose distributions when using high LET radiation remains a challenge. In this paper, my research group introduces a chemical dosimeter that can evaluate the distribution of high LET radiation with a sub millimeter resolution, within several Gy and without sensitivity correction based on the LET.

A sensitive method was developed to determine 5,6-dihydrothymidine (DHdThd) produced by relatively low-dose (<0.1 kGy) gamma irradiation of DNA. Previously, we had examined a method to determine the irradiation history of foods measured by DHdThd levels, which is a radiolytic product formed in the DNA of foods. The method included: (1) DNA extraction from food, (2) enzymatic digestion of DNA into nucleosides, and (3) measurement of DHdThd using liquid chromatography-tandem mass spectrometry. This method could detect relatively high-dose (≥0.5 kGy) irradiation history with regard to the sterilization of both animal- and plant-based food items. However, detection of relatively low-dose (<0.5 kGy) irradiation in foods for quarantine or sprouting inhibition would require more sensitivity, since lower the dose, lesser the DHdThd produced. To enable such detection, in this study, we aimed to introduce the purification and concentration of large amounts of degraded DNA in aqueous solutions, using solid-phase extraction columns, into the existing protocol, and succeeded in increasing the sensitivity of DHdThd by approximately 30-fold. Using this method, DHdThd could be detected, in a dose-dependent manner, in 60–150 Gy gamma-irradiated aqueous solution of thymidine and salmon sperm DNA. The method could be applicable for the detection of gamma irradiation of foods at doses of several tens of Gy.

The combination of isotopes, a radio isotope and a stable isotope can be used for dating, like ¹⁴C-dating. This article discusses the possibility of dating using iodine isotope system (¹²⁹I and ¹²⁷I). Since ¹²⁹I is a long lived radio isotope (half life=15.7 Myr), the iodine isotope system is a potential dating tool for large time scale, which had been initially proposed by Fehn (Rochester University) in Science article published in 2,000. He tried to determine the formation age of methane hydrates in Blake ridge, the United States using ¹²⁹I/¹²⁷I. For the dating, we should know the initial isotopic ratio and he used the value proposed by J. Moran in 1998. However, for the initial ratio, there still is under debate. This article discusses in details the conditions which make possible the dating. As an indispensable measurement method for detection of environmental ¹²⁹I, Accelerator Mass Spectrometry is also explained in details, hardware configuration, physical principle, and pre-treatment of environmental samples.

In recent years, the use of artificial intelligence in imaging analysis has become increasingly popular. In particular, algorithms based on deep learning, a type of machine learning, are considered promising tools. In this study, we used Cellpose 2.0, a cell segmentation algorithm based on deep learning, to analyze changes in cell adhesion following exposure to X-rays in synchronous HeLa cells. We found that the cell adhesion area of G₁-phase cells increased after irradiation, while that of G₂-phase cells decreased.

We designed a patient–radiopharmaceutical matching system for preventing misadministration using smartphone, and developed a deep-learning model to identify radiopharmaceutical containers as an elemental technology for the system. As a result of the ResNet18 transfer learning and 10-fold cross-validation, this model achieved 100％ accuracy in classifying 15 different radiopharmaceutical containers. The feasibility of the proposed system was proven.

Japan’s first commercial spent nuclear fuel reprocessing plant in Rokkasho, Aomori Prefecture, is currently undergoing final active testing. Spent fuel rods under active test were sheared and dissolved from 2006 to 2008, and radionuclides such as ³H, ¹⁴C, ⁸⁵Kr and ¹²⁹I, were released to the atmosphere and ocean. This manuscript summarizes the effects of the active tests at the plant on the ambient radiation and radioactivity in environmental samples, based mainly on our research results and previously published literature.

Distribution of nutrients in plants has a significant impact on crop yield and taste; hence, a knowledge of plant-nutrient relationships is important for developing crop production strategies. The dynamics of element transport and accumulation in plants can be difficult to analyze because they are constantly changing, and the mechanisms underlying element dynamics and distribution control remain unknown. Radioisotope imaging in live plants can be useful for the analyses of changes in element transport and accumulation.

Early diagnosis based on pathophysiology enables optimal treatment. Nuclear medicine is one of the methods for visualizing organ functions and leading to early diagnosis. single photon emission computed tomography (SPECT) is widely used and supports clinical practice. However, the performance of SPECT is not sufficient to meet recent diagnostic needs. In this paper, we argue that the prospects and challenges of replacing part of SPECT with positron emission tomography.

Due to the accident at the Fukushima Daiichi Nuclear Power Station of the Tokyo Electric Power Company, fruit trees such as persimmons were contaminated with radioactive materials. Eight years after the accident, relatively young lateral branches of persimmon trees, which had higher ¹³⁷Cs concentrations in fruit than other trees, were sampled, and the ¹³⁷Cs and ¹³³Cs concentrations in the branches, leaves, and fruits were measured. A correlation was observed between the ¹³⁷Cs concentrations in fruits and branches. ¹³⁷Cs concentrations were different among the branches as well as in leaves and fruits. There was a correlation between ¹³⁷Cs and ¹³³Cs concentrations in the fruits, leaves, and branches. Therefore, it is possible that some of the ¹³⁷Cs that fell on the bark may have migrated to the internal trees and accumulated in the same part as the ¹³³Cs absorbed from the roots, and they were similarly translocated to the fruits via new branches.