Journal of Radiation Research最新文献

Large language models (LLMs), such as ChatGPT and Grok, have rapidly advanced in natural language understanding and are increasingly being applied to specialized fields, including medicine. In this study, we evaluated the domain-specific knowledge of LLMs in radiotherapy by assessing their performance on three certification examinations in Japan: the Japanese Medical Physicist Examination, the Japanese Board Examination for Radiologists and the Japanese Board Examination for Radiation Oncologists. We assessed five LLMs-ChatGPT-5, ChatGPT-5 Pro, Grok 4, Grok 4 heavy and Gemini 2.5 Pro-by inputting all multiple-choice questions from these exams into each model and recording their responses. The AI-generated answers were compared with reference answers determined by experienced medical physicists and radiation oncologists. The results demonstrated average accuracies of 84.7 ± 2.0% (ChatGPT-5), 94.7 ± 2.1% (ChatGPT-5 Pro), 78.4 ± 1.2% (Grok 4), 81.6 ± 2.2% (Grok 4 heavy) and 88.9 ± 1.2% (Gemini 2.5 Pro). All models achieved over 75% accuracy, with ChatGPT-5 Pro consistently outperforming others, attaining an average accuracy exceeding 90% across all examinations. These findings highlight the strong potential of advanced LLMs, particularly ChatGPT-5 Pro, for future integration into radiotherapy-related applications such as automated contouring and treatment planning support.

The uptake of hypofractionated radiotherapy in Japan is not well documented. This study examined trends in the proportion of patients with breast or prostate cancer who received hypofractionated radiotherapy, using hospital-based cancer registry data linked to Diagnostic Procedure Combination records from 69 institutions in Osaka Prefecture (diagnosis years: 2019-23). Eligible patients included 6475 women with unilateral breast cancer (pTisN0M0, pT1-2N0M0 or cT1-2N0M0 before neoadjuvant therapy) who underwent partial mastectomy and radiotherapy at the same hospital and 3274 men with cT1-3N0M0 prostate cancer treated with external-beam radiotherapy without surgery or brachytherapy. The use of hypofractionated radiotherapy was determined through insurance claims. Among the patients with breast cancer, the proportion of those who received hypofractionated radiotherapy increased from 41% in 2019 to 81% in 2023. In 2023, this proportion was highest at facilities with high radiotherapy volume (95%), followed by those with medium (84%) and low (67%) volumes. Among the patients with prostate cancer, the proportion of those who received hypofractionated radiotherapy (hypofractionated intensity-modulated radiotherapy or stereotactic body radiotherapy) increased from 25% in 2019 to 48% in 2023, although the increase slowed after 2021. In 2023, hypofractionated radiotherapy use reached 79% at high-volume facilities, while proportions were lower at medium- (30%) and low-volume (17%) facilities. Hypofractionated radiotherapy use has increased in patients with breast and prostate cancers. However, its adoption in prostate cancer treatment remains limited, particularly in medium- and low-volume facilities. These findings suggest that certain barriers limit its implementation and highlight the need to address them.

When electrons exceed the speed of light in a medium, they emit low-intensity visible light, known as Cherenkov emission (CE). This study proposes a novel CE-based quality assurance (QA) test for linear accelerators. A CE-based QA (C-QA) phantom incorporating a mock tumor and four CE observation plates (top, bottom, left, and right) was developed. After tumor-based alignment using cone-beam computed tomography (CBCT), lateral and posterior fields were used for irradiation. A C-Dose camera was employed to measure the treatment position, gantry angle, photon energy (TPR20,10), and CE counts for both fields. The treatment position and TPR20,10 were determined by analyzing the changes in the CE profile, while the gantry angle was calculated based on the tilt between the entry and exit field positions. Confidence limits were evaluated over a three-month period, during which long-term testing demonstrated favorable results. The standard deviations (σ) for CBCT-based positional accuracy and gantry angle were within ±1 mm in all three directions and within 1°, respectively. The mean ± σ for TPR20,10 was 0.631 ± 0.004, closely matching the 0.629 measured using an ionization chamber. Detected CE counts exhibited a higher variation (σ = 2.7%). CE-based QA appears to be an effective and reliable method for radiotherapy. Treatment position could be directly measured without conventional dosimetric devices, while CE imaging simultaneously evaluated positional accuracy, gantry angle, and photon energy (TPR20,10). However, accurate assessment of linear accelerator dose output remains a challenge, and the quantification of CE counts requires further investigation.

This study aims to assess chromosome aberrations in peripheral blood lymphocytes of orthopaedic surgeons in Japan, specifically focusing on potential occupational dose overexposure and its correlation with adverse health reactions. The main objective is to investigate the extent of chromosomal damage and evaluate the accuracy of estimating radiation dose with cytogenetic biodosimetry where no physical dosimetry exists. This study involved 18 male orthopaedic surgeons, with occupational experience spanning 15 to 33 years. Chromosome aberrations were analyzed in 32 573 and 45 674 cells with dicentric chromosome and translocation assays, respectively. Statistical tests were used to retrospectively estimate whole-body doses with chromosome damage and compare observed aberration frequencies with work experience, while considering factors such as adverse health effects and skin cancer history. Materials and methods included information on study design, participant criteria and the procedures performed, using a retrospective approach. Participants had a mean age of 46 ± 6.6 years. Analysis revealed an increase in dicentric abnormalities compared to background levels, and translocations were observed above spontaneous levels in all surgeons but one. Surgeons reporting adverse health effects or skin cancer exhibited the highest chromosome aberrations frequencies. The estimated average whole-body doses were 75 ± 24 and 321 ± 103 mGy for dicentrics and translocations, respectively. Some Japanese orthopaedic surgeons demonstrated increased chromosome aberrations, especially in those reporting adverse health effects. Estimating radiation dose solely based on chromosomal damage is challenging, emphasizing the complexities of biological dosimetry for prior, partial and repeated exposures.

This study aims to investigate the potential correlation between the hematological dose (HEDOS), representing the dynamic blood dose, and severe radiation-induced lymphopenia (SRIL). The study examines whether SRIL mediates the relationship between HEDOS and oncologic outcomes in patients with hepatocellular carcinoma (HCC). A total of 41 patients with HCC who received radiation therapy to the liver and/or perihepatic metastatic lesions were retrospectively analyzed. Blood-related organs (spleen, heart, veins, aortas, lungs, and liver) were manually delineated. HEDOS was calculated using a Markov chain model. The effective dose to immune cells (EDIC), representing the static blood dose, was calculated for comparison with HEDOS. We examined whether these two blood dose metrics correlated with SRIL, defined as an absolute lymphocyte count below 500/μL one month after radiotherapy. The association between blood dose metrics and clinical outcomes, local and distant recurrence-free survival (LFS and DFS) was also evaluated. The mean HEDOS was significantly associated with SRIL, with an odds ratio of 1.61 (95% confidence interval [CI]: 1.10-2.54, P = 0.02). The mean HEDOS was associated with worse LFS and DFS, with hazard ratios of 1.35 (95% CI: 1.06-1.71, P = 0.01) for LFS and 1.28 (95% CI: 1.01-1.63, P = 0.04) for DFS. No association was observed between EDIC and any of the outcomes. A higher mean HEDOS showed a statistically significant correlation with SRIL and clinical outcomes, whereas the EDIC did not. The HEDOS, which incorporates temporal delivery characteristics such as dose rate and beam-on-time, may have an advantage for predicting SRIL and clinical outcomes of patients with HCC.

The study aimed to investigate early radiobiological effects of Flattening Filter (FF) and Fattening Filter-Free (FFF) beams on brain tissue in experimental rat models and to evaluate the potential radioprotective role of melatonin (MEL) using histopathological and biochemical parameters. Forty female Wistar albino rats were randomly assigned to five groups: control (G1), FF (G2), FF + MEL (G3), FFF (G4) and FFF + MEL (G5). A single 16 Gy dose was delivered to the head and neck region in G2 and G4. MEL (50 mg/kg) was administered intraperitoneally 15 minutes before irradiation in G3 and G5. Forty-eight hours post-irradiation, serum samples were analyzed for M30, M65, TAS, TOS and OSI. Brain and cerebellar tissues were histologically examined for neuronal degeneration, vascular dilatation, congestion, axonopathy, inflammation, dysplasia and necrosis. While M30, M65, TOS and OSI levels increased in G2 and G4 radiotherapy groups, TAS levels decreased for biochemical analyses (P < 0.05), reflecting impaired antioxidant capacity. However, these alterations were significantly reduced in the MEL-treated groups (G3 and G5) (P < 0.05). Histopathologically, neuronal degeneration, vascular dilatation and congestion were observed in G2 and G4 groups. MEL administration significantly alleviated these findings. No statistically significant differences were found between the FF and FFF groups regarding biochemical or histopathological outcomes (P > 0.05). While FF and FFF beams caused similar levels of oxidative stress and histopathological damage in the brain tissue, MEL treatment significantly reduced these damages. MEL emerges as a promising radioprotective agent against early radiation-induced brain injury.

The objective of this study was to establish guidelines for evaluating the health effects of electromagnetic fields (EMFs). To achieve this, a comprehensive evaluation of EMF effects on living organisms from both engineering and biological perspectives is essential. As part of this study, we examined the impact of intermediate-frequency magnetic fields (IF-MF) exposure on peripheral nerves in mice and validated the reliability of five pain assessment methods. The engineering approach was based on our pilot study, while the biological approach involved exposing mice to IF-MF for a 28-day period and assessing neurotoxicity through the implementation of five pain tests. The von Frey test, conducted with a Dynamic Plantar Aesthesiometer, was performed at various time points during exposure. The results indicated that leg withdrawal time was shortened only in the positive control group. After conducting a series of assessments, we demonstrated that no statistically significant differences were observed among the IF-MF-exposed, sham-exposed and control groups. However, the positive control group exhibited significant variations in the four supplemental assessments. No significant differences were detected in the other three groups. These findings suggest that subacute (28-day) IF-MF exposure at 2.3 times the basic restriction for occupational exposure according to International Commission on Non-Ionizing Radiation Protection guideline does not result in peripheral neurotoxicity and that the utilized pain assessment methods used for IF-MF exposure are effective.

4-Borono-L-phenylalanine (BPA) is a key 10B carrier used in boron neutron capture therapy (BNCT), while its PET tracer analogue, 4-borono-2-18F-fluoro-L-phenylalanine (18F-BPA), enables non-invasive visualization of tumour boron uptake. Since BNCT efficacy depends on precise tumour boron accumulation, we evaluated whether 18F-BPA mirrors BPA's transport and biodistribution. In vitro, BPA exhibited a highly consistent uptake profile with its non-radioactive fluorinated analogue, 2-19F-4-borono-L-phenylalanine (19F-BPA), across nine cancer cell lines (r = 0.9455, P < 0.001) and tri-iodothyronine (T3)-mediated LAT-1 inhibition markedly reduced the uptake of both BPA and 19F-BPA. In vivo, BPA and 18F-BPA showed predominant accumulation in the kidneys and pancreas in Sprague-Dawley rats, with substantially lower levels detected in other organs. Importantly, in tumour-bearing mice, the time-concentration curve of BPA and the time-activity curve of 18F-BPA in tumours were found to be highly consistent, and showed a corresponding relationship between BPA concentration and 18F-BPA activity in terms of accumulation in tumour, blood, and muscle (r = 0.9623, P < 0.0001). Collectively, these findings confirm that BPA and 18F-BPA not only share LAT-1-mediated transport mechanisms, but also exhibit similar pharmacokinetics and tumour-specific accumulation. This substantiates the use of 18F-BPA as a reliable surrogate for visualizing BPA biodistribution and optimizing patient-specific BNCT treatment planning.

In animals, low-dose-rate radiation induces cancer at a reduced rate compared with a high-dose-rate at an identical cumulative dose, although the underlying mechanism is not well understood. The immediate responses of cells to irradiation are well established, including DNA double-strand break repair, cell-cycle arrest and cell death; conversely, the changes in tissues weeks after irradiation are not well understood. We therefore analysed cellular dynamics in rat mammary tissue weeks after high- or low-dose-rate irradiation. We irradiated 5-week-old rats with 2 Gy (30 Gy/h) or 3- to 5-week-old rats with continuous 2 Gy (6 mGy/h). For histological analysis, luminal cells were identified with anti-cytokeratin (CK) 8 + 18; CK8 + 18Low cells are luminal progenitor cells, and CK8 + 18High cells are luminal mature cells. To evaluate cell composition by flow cytometry, epithelial cells were isolated from mammary tissue. The proliferative potential of luminal progenitor cells-as measured by Ki-67 on paraffin sections-decreased 2 weeks after irradiation at either the high- or low-dose rate but recovered to the control level by 4 weeks. No significant difference was observed in the S phase and total cell-cycle length identified by 5-ethynyl-2'-deoxyuridine and 5-bromo-2'-deoxyuridine or cell death marked by cleaved caspase-3 among the dose-rates. Furthermore, the composition of luminal mature cells changed 2-6 weeks after completing the high- and, to a lesser extent, low-dose-rate radiation exposure, indicating potential proliferative stimulation of luminal progenitor cells related to susceptibility to carcinogenesis. These findings suggest that the altered cell composition and dynamics of luminal cells for several weeks contribute to carcinogenesis.

This study aimed to evaluate indoor radon concentrations in Riobamba canton, Ecuador's central Andean region, and to analyze two factors influencing their variability: surface geology and the age of the dwelling. Radon measurements were conducted in 225 homes using passive monitoring systems, while continuous laboratory monitoring with a Lucas Pylon cell was employed to assess temporal patterns. Concentrations ranged from 9.4 to 152.8 Bq/m3, with an arithmetic mean of 49.5 ± 26.6 Bq/m3. Ninety-four percent of the homes had radon concentrations below the World Health Organization's recommended reference level of 100 Bq/m3. The calculated average annual effective dose was 1.3 ± 0.7 mSv/year, well below the International Commission on Radiological Protection action level of 10 mSv/year. A statistically significant association was identified between radon levels and the age of the homes; however, no relationship was found between radon levels and the surface geology beneath the buildings. The highest concentrations were observed in houses built before 1925 using traditional techniques such as bahareque, adobe and cancagua. Seasonal analysis revealed minimal variability throughout the year (dry season mean/rainy season mean = 1.04), a result that differs from the well-documented behavior in regions with marked seasonal variability and suggests that seasonal correction factors are not necessary. In addition, a diurnal pattern was evident, which was inversely correlated with indoor temperature and directly correlated with relative humidity. These findings enhance the understanding of radon behavior in the tropical Andean climates characterized by low seasonal variability.