National Institutes for Quantum and Radiological Science and Technology
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Evaluation of imaging plate sensitivities to ion beams
No full textSince its sensitivity to ion beams is high, an imaging plate is often utilized for beam measurements.However, as its sensitivities to light- and heavy-ion beams appear different, the sensitivity model of an imaging plate for light-ion beams is not applicable to heavy-ion beams. In addition, the parameters defined in the model for heavy-ion beams must be examined for each ion species. This study focused on a new energy deposition model to estimate the sensitivity to all ion species. We applied this model to previous experimental studies and found that this model with constant parameter values can explain the results of most of the earlier studies. The characteristics of the sensitivities to each type of imaging plate and scanner model were also studied. This analysis model might help predict the as yet unexamined sensitivities of imaging plates to ion beams.journal articl
Highlight selection of radiochemistry and radiopharmacy developments by editorial board
No full textBackground The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development and application of radiopharmaceuticals.Main body This selection of highlights provides commentary on 24 differenttopics selected by each co-authoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first-in-human application of novel radiopharmaceuticals.Conclusion Trends in radiochemistry and radiopharmacy are highlighted. Hot topics cover the entire scope of EJNMMI Radiopharmacy and Chemistry, demonstrating the progress in the research field in many aspects.Keywords Highlight articles, Radiochemistry, Radiopharmacy, Radiopharmaceutical sciences, Nuclear medicinejournal articl
Cross-section Prediction Method for Proton Direct Ionization Induced Single Event Upset
No full textThis paper proposes a method for predicting the cross section (XS) of single event upset (SEU) induced by proton direct ionization (PDI). The method is based on the physics-based model previously proposed for both bulk FinFET static random access memories (SRAMs) and planar SRAMs under heavy ion irradiation. The method presented in this paper predicts PDI XS for both 16-nm FinFET and 40-nm planar SRAMs below a few MeV regime, thanks to the broad predictability of our XS model in linear energy transfer (LET) dependence. By calibrating the parameters through heavy ion irradiation, our method enables the prediction of PDI SEU XS in SRAMs, which has not been analytically addressed in previous studies, and its validity has been verified.journal articl
Radiofluorination of 2‑Arylquinolin-4-yl Oxypropanamide Derivatives for TSPO Imaging in Neuroinflammatory Murine, Nonhuman Primates, and Human Brain Autoradiography with Insensitivity to the rs6971 Polymorphism
No full textThe 18 kDa translocator protein (TSPO) is a critical target for PET imaging of neuroinflammation in central nervous system (CNS) disorders; however, many clinical TSPO PET tracers are limited by sensitivity to rs6971 polymorphism. Inthis study, three novel fluorine-containing oxypropanamide ligands were developed, with 11 (LW1, Ki = 0.07 nM) and 12 (LW2, Ki =0.05 nM) showing high TSPO affinity. The radiolabeled [18F]12 demonstrated superior metabolic stability, specificity, and reduced polymorphism sensitivity compared to [18F]11 in autoradiography using Tg2576, PS19 mouse models, and human brain tissues. [18F] 12 was further evaluated in APP/PS1 transgenic mice and ischemic stroke rats for neuroinflammatory imaging and in healthy rhesus monkeys to access pharmacokinetics via dynamic PET with arterial sampling. The combination of excellent brain penetration, high specificity, and rs6971 insensitivity supports [18F]12 as a promising TSPO PET tracer for clinical translation.journal articl
Derivation of Ion Transport Coefficients Driven by Ion–Atom Collisions Using the Chapman–Enskog Expansion and the Boltzmann Collision Integral
No full textTo realize a fusion reactor, reducing the divertor heat load is essential, necessitating the development of accurate physical models. In divertor plasmas, large-angle scattering between ions and atoms drives ion transport perpendicular to magnetic field lines. This study derives transport coefficients for hydrogen isotope ions due to ion–atom collisions using the Chapman–Enskog expansion method.Afast computational method for the Boltzmann collision integral is presented, incorporating the differential cross section. The proposed transport coefficients are provided as user-friendly data for application to fluid simulation codes. The diffusion coefficient for protons can exceed the Bohm diffusion coefficient under conditions of low magnetic field and high hydrogen atom density. The derived diffusion coefficient yields density profiles that show improved agreement with kinetic calculations compared to those obtained using our previous diffusion coefficient model.journal articl
Observation of Boron Vacancy Concentration in Hexagonal Boron Nitride at Nanometer Scale
No full textWe employ electron energy loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM) using monochromated 30-keV electrons, effectively reducing background interference. This approach unveils distinct spectral peaks at 2.5 and 1.9 eV, corresponding to VB– and VB0 defects, respectively. Furthermore, we achieve nanometer-scale concentration mapping for VB– and VB0 defects, advancing insights into spin defect configurations crucial for optimizing quantum sensor performance.journal articl
Observation of spin-conserving two-spinon continuum in the S=1/2 antiferromagnetic chain system Sr2CuO3 using Cu K-edge resonant inelastic x-ray scattering
No full textWe report a Cu K-edge resonant inelastic x-ray scattering (RIXS) study of spin excitations in the S=1/2 antiferromagnetic chain system Sr2CuO3. The spectral weight observed below the charge-transfer gap appears in two-spinon continuum, indicating the fractionalization of a spin-conserving (ΔS = 0) magnetic excitation into two-spinon states. The intensity of these excitations reaches a maximum near the midpoint between the center and the boundary of the Brillouin zone, and decreases toward the zone boundary; this behavior contrasts with that of the spin-flip (ΔS = 1) excitations typically observed via inelastic neutron scattering or Cu L3-edge RIXS. The momentum dependence of the intensity is described by the spin-exchange dynamical structure factor. A phenomenological analysis of the symmetry between the polarization and the d orbital explains the resonance condition for the two-spinon excitations.journal articl
Repeated artificial mutagenesis during experimental evolution accelerates the acquisition of high-temperature tolerance by Bradyrhizobium diazoefficiens
No full textEffective mutant screening is critical for improving industrial microorganisms. This study was conducted to evaluate the effect of repeated mutagenesis on the experimental evolution of rhizobial high-temperature tolerance because the repeated mutagenesis approach is conducive to accumulating beneficial mutations relatively quickly. Wild-type Bradyrhizobium diazoefficiens USDA110 cells grow optimally at 32−34 °C, but their growth is markedly retarded at 36 °C. Wild-type cells were subcultured in a 96-well deep-well plate for 76 or 83 days, with a gradual increase in temperature from 34.0 to 37.0 °C. Additionally, they were exposed to gamma radiation (1–120 Gy, 10 times in total) during the experimental period. The 40-Gy and 80-Gy treatments generated the most lines with high-temperature-tolerance. However, after extended subculturing without mutagenesis, tolerant lines obtained following the 80-Gy treatment produced smaller colonies than tolerant lines obtained after the 40-Gy treatment, suggesting the accumulation of deleterious mutations. These results imply that approximately 40 Gy is the appropriate dose for accumulating beneficial mutations under our experimental conditions. The two most tolerant lines obtained via the 30-Gy treatment commonly had a mutation in the 16S ribosomal RNA gene and the DNA-directed RNA polymerase subunit beta′ gene (rpoC), possibly reflecting a strong relationship with high-temperature tolerance. These results suggest that experimental evolution with an appropriately increased mutation frequency is effective for obtaining novel mutants.journal articl
Radiation-induced transformation of peptides into nanoparticles for nano-theranostics of pancreatic cancer with controllable drug delivery and sustained release
No full textNano-theranostics using biodegradable polymers are effective for the diagnosis and treatment of intractable cancers, but there is a need for technology that can control its bioavailability and biodegradability without compromising its biocompatibility. Peptide nanoparticles with controlled particle size and biodegradability were prepared by ionizing radiation and loaded with imagining agents and anticancer drugs to develop novel nano-theranostics for pancreatic cancer diagnosis and treatment in this study. Peptides composed of histidine, glycine, glutamic acid, and arginine-glycine-aspartic acid (RGD motif) were synthesized by solid synthesis method, and its aqueous solutions were irradiated by γ-rays to produce their nanoparticles with a particle size less than 50 nm, which can penetrate the pancreatic cancer stroma. Radiation crosslinking of peptides with or without RGD motif in water were investigated by pulse radiolysis experiments. The peptide nanoparticles loaded with fluorescent labeling agents or MRI imaging agents were efficiently taken up by pancreatic cancer cells. The cisplatin loaded peptide nanoparticles produced by higher dose irradiation suppressed drug release rates due to their lower biodegradability. Peptide nanoparticles controlled their particle size and biodegradability were produced by using ionizing radiation method and were loaded with a fluorescent labeling agent, a MRI imaging agent, and an anticancer drug to develop a new nano-theranostics drug for pancreatic cancer diagnosis and treatment.journal articl
Benchmarking GPT-5 Performance and Repeatability on the Japanese National Examination for Radiological Technologists over the Past Decade (2016–2025)
No full textPurpose:To evaluate GPT-5 against GPT-4o on the Japanese National Examination for Radiological Technologists (2016–2025), assessing accuracy, repeatability, and factors influencing performance differences.Materials and methods:We analyzed 1992 multiple-choice questions involving text and images, spanning the medical and engineering domains. Both models answered all questions in Japanese under identical conditions across three independent runs. Majority-vote accuracy (correct if ≥ 2 of 3 runs were correct) and first-attempt accuracy were compared using McNemar’s test. Repeatability was quantified with Fleiss’ κ. Univariable and multivariable analyses were conducted to identify question-level factors associated with GPT-5 improvements.Results:Across all 10 examination years, GPT-5 achieved a majority-vote accuracy of 92.8 % (95 % CI: 91.5–93.8), consistently outperforming GPT-4o at 72.4 % (95 % CI: 70.4–74.4; P < .001). Repeatability was higher for GPT-5 (κ = 0.925, 95 % CI: 0.915–0.935) than for GPT-4o (κ = 0.904, 95 % CI: 0.894–0.914), with correct answers in all three runs for 88.2 % vs. 68.9 % of items. GPT-5 performed better than GPT-4o in text-based (96.5 % vs. 78.1 %) and image-based questions (72.6 % vs. 41.9 %). Significant improvements were observed for MRI, CT, and radiography images; however, performance improvements were smaller for clinically oriented ultrasound and nuclear medicine images. The greatest advantages were observed in calculation questions (97.3 % vs. 39.3 %) and engineering-related domains, consistent with external benchmarks highlighting GPT-5’s improved reasoning.Conclusion:GPT-5 demonstrated significantly higher accuracy and repeatability than GPT-4o over a decade of examination, with improvements in quantitative reasoning, engineering content, and diagram interpretation. Although improvements extended to medical images, performance in clinical image interpretation remains limited.journal articl