Nuclear medical imaging, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), plays crucial roles in clinical diagnosis including the detection of cancers in its early stage and the evaluation of treatments. The imaging quality of those devices has been evolving rapidly, however the principle of imaging is not changed much after the invention. In this paper, we introduce and discuss two novel imaging principles, Compton-PET and double photon emission coincidence imaging (DPECI) aiming for imaging of multiple molecules and intermolecular interaction in the field of nuclear medicine. The radiation detection technology realizing those devices is also introduced in the last section.

The main indications of radon therapy are pain related diseases. To elucidate the mechanisms and find out new indications, radon exposure system was developed. Results of studies showed that radon inhalation activated antioxidative functions and inhibited several oxidative stress related diseases. These findings indicate that radon therapy may have beneficial effects for oxidative stress induced diseases. Similar effects have been shown following low dose X-irradiation.

Rapid and precise radioisotope identification in the scene of nuclear detection and nuclear security incidents is one of the challenging issues for the prompt response to the detection alarm or the incidents. A radioisotope identification algorithm using a deep artificial neural network model applicable to handheld γ-ray detectors has been proposed in the present paper. The proposed algorithm automatically identifies gamma-emitting radioisotopes based on the count contribution ratio (CCR) from each of them estimated by the deep artificial neural network model trained by simulated γ-ray spectra. The automated radioisotope identification algorithm can support first responders of nuclear detection and nuclear security incidents without sufficient experience and knowledge in radiation measurement. The authors tested the performance of the proposed algorithm using two different types of deep artificial neural network models in application to handheld detectors having high or low energy resolution. The proposed algorithm showed high performance in identifying artificial radioisotopes for actually measured γ-ray spectra. It was also confirmed that the algorithm is applicable to identifying ²³⁵U and automated uranium categorization by analyzing estimated CCRs by the deep artificial neural network models. The authors also compared the performance of the proposed algorithm with a conventional radioisotope identification method and discussed promising ways to improve the performance of the algorithm using the deep artificial neural network.

Although the system of radiation protection has evolved over half a century, there are still scientific or methodological absurdities. Two of them are discussed in this article: The first is on the problem of applying the system of radiation protection to even very low doses, and the second is on the irrationality of the dose system used for radiation protection. Proposals for recovering rationality of the system are also shown.

We have developed amphiphilic polydepsipeptide micelle “lactosome” as a novel nanocarrier with tumor accumulation properties for cancer imaging probes. In this study, radioiodine-labeled lactosomes were synthesized and evaluated to develop diagnostic radiotracers for in vivo imaging utilizing single photon emission computed tomography (SPECT). The ¹²⁵I-labeled lactosome was obtained in sufficient yields for biodistribution studies. Radioactivity in the blood circulation was maintained at a high level between 2–48 h post-injection of ¹²⁵I-labeled lactosome into BALB/c mice. Radioactivity uptake by the Colon-26 tumor implanted in the femur gradually increased. The uptake ratio of subcutaneous tumor/muscle increased to 16.7 at 48 h post-injection. Additionally, tumor SPECT imaging of ¹²³I-labeled lactosome in mice was achieved. Radioactivity uptake of turpentine-induced inflamed tissue reached a maximum at 24 h and then decreased at 48 h post-injection. The mean uptake ratio of inflammatory tissue/muscle increased to 14.4 at 24 h. In conclusion, radioiodine-labeled lactosomes as nanocarriers may serve as potential candidates in facile and generic tumor or inflammation imaging techniques.

The sprout inhibition of onion and potato by low energy X-rays was investigated using a 160 kV X-ray irradiation system to determine optimal irradiation conditions. The sprouting of onion was effectively suppressed by irradiating 20 Gy at a depth of 3.2 mm from root side for small onion and at 8.0 mm depth for large onion, respectively. For potato, double-sided irradiation was necessary to irradiate the entire potato because the buds were distributed throughout the entire potato. Irradiation on double-sided at a depth of 8.0 mm with 50 Gy (60 Gy at 5.4 mm) effectively inhibited the sprouting. The throughput calculated to be 80.9 kg/h for large onion, 34.1 kg/h for small onion, and 9.9 kg/h for potato at a distance of 350 mm from the focal point of source. Dose uniformity (D_max at surface/D_min at 8.0 mm depth) of potato in case of double-sided irradiation was improved from 3.6 (182 Gy/50 Gy) to 1.2 (58 Gy/50 Gy) by using an aluminum 1.0 mm filter (F1) to cut off low energy X-rays, whereas the throughput capacity decreased from 9.9 kg/h to 7.4 kg/h.

The radioactive caesium concentration of brown rice can be accurately predicted from the amount of dissolved radioactive caesium in the soil when exchangeable potassium level is high enough not to affect absorption of radioactive caesium by rice plant. However, measuring the amount of dissolved radioactive caesium requires a lot of labor, such as collecting a large amount of soil solution, filtering, and concentrating. Therefore, we investigated whether it is possible to adsorb dissolved radioactive caesium in soil on an adsorption sheet supporting zinc-substituted Prussian blue and use it for simple prediction of radioactive caesium concentration in brown rice. A caesium adsorption disk coated with a membrane filter to prevent adhesion of soil particles was buried in the surface soil of a local paddy field for two weeks, and dissolved radioactive caesium was recovered. The amount of radioactive caesium recovered on the adsorption sheet was highly positively correlated with the concentration of radioactive caesium in brown rice. By embedding an adsorption sheet at the tillering stage of cultivation and analyzing the collected radioactive caesium concentration, it is possible to predict the radioactive caesium concentration in brown rice without the need to collect a large amount of soil solution or analyze the soil physicochemical properties.

General relativity and quantum theory are the pillars of modern physics. Theoretical physics has developed, unifying different theories consistently. The next big challenge for theoretical physics is unifying general relativity and quantum theory. Superstring theory is a candidate for the quantum theory of gravity. At the same time, it is also a candidate for the unified theory of four forces: gravity, electromagnetic force, weak force, and strong force. I will explain how superstring theory was born and how it is along the idea of unification.

State of the art techniques of trace isotope analysis using laser resonance excitation are reviewed including Resonance Ionization Mass Spectrometry, Caviry RingDown Spectroscopy, and Atom Trap Trace Analysis. Electronic structure of atoms, isotope shifts and hyperfine structure induced by nuclear spin are explained. The interaction between atoms and laser electric field and Rabi oscillation for efficient excitation of an electron are shown. The basic principle of laser cooling is described. Methodology and examples of trace isotope analysis using laser resonance excitation are summarized.