Journal of Radiation Research最新文献

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.

This study aimed to establish the diagnostic reference levels (DRLs) of imaging doses for image-guided radiotherapy (IGRT) used in intensity-modulated radiotherapy for prostate cancer in Japan. A nationwide survey was conducted to gather data on image acquisition conditions, parameters, and frequencies across 193 radiation therapy institutions using intensity-modulated radiotherapy. IGRT modalities, such as kilovoltage and megavoltage cone-beam computed tomography (CBCT), two-dimensional imaging, and in-room computed tomography (CT), were targeted. Data analysis focused on image acquisition parameters displayed by the devices, such as tube voltage, current, and imaging dose, along with the CT dose index volume (CTDIvol) and dose-length product (DLP), were collected from 222 radiotherapy devices. The results showed that kV-CT/CBCT was the most frequently used modality, used in 94% of the institutions. Imaging dose-reduction techniques were adopted by over half of the institutions, with 56% optimizing imaging parameters and 45% reducing the imaging field size or scan length. The 75th percentile for CTDIvol was 16.0 mGy, while that for DLP was 263 mGy·cm, with considerable variation among devices and institutions. This study provides the first large-scale reference data for IGRT imaging doses used for prostate cancer treatment in Japan. These results are critical for improving patient safety by optimizing imaging protocols and establishing DRLs tailored to IGRT. These findings will serve as a basis for further refinement of radiological protection practices in Japan.

This study evaluated the impact of off-center diagonal (OCD) profile depth pairing between the treatment planning system (TPS) and the electronic portal imaging device (EPID) on gamma pass rates in portal dosimetry. In clinical workflows, OCD profiles are used in the TPS to generate predicted images via the portal dosimetry image prediction (PDIP) algorithm and in the EPID system to correct measured fluence. The consistency of these settings may influence verification accuracy. Portal images were acquired using a TrueBeam linear accelerator with an aS1200 EPID for four photon energies: 6X, 10X, 6 flattening filter-free (FFF) and 10FFF. Five OCD profiles (reference depth, 5, 10, 20 and 30 cm) were configured in both the PDIP model and EPID system. For each energy, a total of 175 plan-measurement combinations were evaluated, derived from five PDIP OCD depths combined with five EPID OCD depths across seven field sizes. Field sizes ranged from 5 × 5 to 30 × 30 cm2. Gamma analysis used 3%/3 mm criteria with a 10% dose threshold. A two-way analysis of variance assessed the effects of TPS and EPID OCD depths and their interaction. For 6X and 10X beams, pass rates varied with configuration, showing better agreement when depths were matched or EPID was deeper. In contrast, 6FFF and 10FFF beams maintained high pass rates with minimal variation. These findings indicate that OCD depth pairing influences portal dosimetry performance, particularly for flattened beams, underscoring the importance of depth-aware configuration in QA protocols.

Boron Neutron Capture Therapy (BNCT) is a targeted radiotherapy that utilizes the nuclear reaction of 10B with thermal neutrons to destroy tumor cells while sparing healthy tissue. Its effectiveness relies on accurately modeling boron distribution. Current treatment planning systems use a fixed tumor-to-normal tissue (T/N) boron ratio, ignoring pharmacokinetics. This study improves BNCT dose calculations by integrating time-dependent boron concentrations from pharmacokinetic simulations. Firstly, this research improved the traditional two-compartment pharmacokinetic model to a three-compartment model to better represent boron distribution, accounting for different tumor locations. Two patient cases were simulated, and the comparisons were performed between the dose distributions obtained by the fixed T/N ratio method and the ones obtained by our pharmacokinetic-based approach. Results showed significant discrepancies between the two methods, with the maximum dose deviation in the tumor region reaching 11.386%. The pharmacokinetic-based method provided more accurate and individualized dose calculations. Secondly, the multi-objective optimization using the Basin Hopping algorithm was employed to determine the optimal irradiation time periods. This approach enhanced treatment efficacy by increasing the average dose and maximum dose in the gross tumor volume by ~4% within the same irradiation period, while minimizing damage to normal tissues. The optimized irradiation schedules resulted in improved dose delivery to the tumor while maintaining safe levels for normal tissues. Our findings highlight the importance of integrating pharmacokinetic data into BNCT treatment planning to improve dose accuracy and treatment outcomes.

Spacers separating the tumor from adjacent organs help improve irradiation dose parameters. We introduce a new hyaluronate gel spacer with MEIJI (ADANT®) as an alternative to the previously used Suvenyl® and its injection technique for cervical cancer brachytherapy. Five patients with cervical cancer underwent hyaluronate gel injection (HGI) with the MEIJI hyaluronate gel in their rectovaginal and vesicovaginal septa. The minimum doses covering 90% of the high-risk clinical target volume (CTVHRD90%), the most exposed 2 cc (D2cc) of organs at risk per session, as well as the total doses for combined external beam radiotherapy (with a central shield) and brachytherapy, were assessed. The median CTVHRD90% was 9.3 (range, 6.4-9.7) Gy per session and 92.2 Gy in the equivalent dose in 2 Gy fractions (EQD2) (80.3-93.3 Gy-EQD2) overall. The median rectum D2cc was 2.9 (1.8-5.0) Gy per session and 45.4 (43.4-57.1) Gy-EQD2 overall. The median D2cc of the bladder (bladder D2cc) was 4.8 (2.4-6.5) Gy per session and 64.6 (62.3-69.6) Gy-EQD2 overall. The MEIJI spacer disappeared within 3 or 7 days with no adverse events associated with HGI or deterioration of the patients' quality of life. MEIJI HGI facilitates a sufficient CTVHRD90% while keeping the rectal and bladder D2cc within dose constraints, even when the rectum and bladder are in close proximity to the CTVHR. In conclusion, the MEIJI spacer may help appropriately meet dose constraints, thereby potentially contributing to improving local control and/or reducing adverse events for patients receiving radiotherapy for cervical cancer.

This study presented a quantitative analysis of the differences in the depths of the distal 50% of acquired and estimated positron emission tomography (PET) images for 18 patients who had a total of 109 titanium (Ti) metal-surgical clips implanted after breast-conserving surgery. Offline PET/computed tomography (PET/CT) images were acquired after proton irradiation. Hounsfield Unit modifications were applied to correct for metal artifacts induced by the Ti clips in the planning CT scans of the soft tissues surrounding the clips. The positron-emitting-isotope PET distribution was calculated through Range-Verification scripting. Quantitative analysis was conducted on the depth differences at the distal 50% R50 of the PET and the calculated PET distribution. Using the R50 method, the depth verification results of the clips and the normal tissues were compared. The R50 method calculates the positional difference at the half-maximum value 2 cm from the skin, with clips beyond this position not affecting the results. Analyses of the regions around the Ti clips were conducted. The depth difference for Ti < 2 cm (where the depth of the clips from the skin was <2 cm) was -1.63 ± 1.08 mm, while the corresponding normal tissue (Ticont) showed a depth difference of -1.79 ± 1.15 mm. There was no statistically significant difference in the depth differences between Ti < 2 cm and the corresponding Ticont. This study utilized offline PET verification to demonstrate that applying tissue corrections based on surgical clips and surrounding muscle tissues in clinical practice ensures that the presence of surgical clips does not compromise the precision of proton dose delivery at the surgical site.

From simple viruses to complex multicellular animals, ionizing radiation can have deleterious effects on all organisms. For humans, exposure to radiation can come from a wide range of sources such as environmental contamination, occupational hazards, radiotherapy and space flight. In the next few decades, radiation toxicity will become an increasing healthcare concern as nuclear power usage, risk of nuclear war, space-based industry and cancer incidence are all projected to increase. While the biology of acute radiation sickness is relatively well understood, ionizing radiation can also cause severe chronic effects whose molecular and cellular basis remain largely a mystery. This is partly because complications that arise months or even years after exposure depend on tissue-level responses, and so there are aspects of late radiation toxicity that can only be investigated in vivo. We suggest that Drosophila melanogaster can contribute to understanding this phenomenon. To this date, Drosophila radiation research has been heterogenous in terms of dose, radiation type and developmental stage of exposure, but despite this a pattern of observations suggest that fruit flies experience both short- and long-term radiation injury. Moreover, the genetic underpinning of the Drosophila radiation response seems conserved with that of humans. We propose that Drosophila is well-suited to model radiation damage to tissues, highlighting the potential of the fly to inform clinical radiobiology research.

Total neoadjuvant therapy (TNT) improves oncological outcomes in locally advanced rectal cancer (LARC); however, treatment-induced lymphopenia remains a concern. We analyzed 74 patients undergoing three TNT regimens: long-course chemoradiotherapy with consolidation chemotherapy (LCCRT-CNCT), short-course radiotherapy with CNCT (SCRT-CNCT), and induction chemotherapy with LCCRT (INCT-LCCRT). Severe radiation-induced lymphopenia (RIL, Grade ≥ 3) occurred in 48%, 24%, and 54%, respectively (P = 0.126). In the LCCRT-CNCT group, large bowel irradiation (V35 Gy > 46 cc) was significantly associated with severe RIL in univariable analysis but not in multivariable models (P = 0.227), and in an exploratory combined analysis of LCCRT-CNCT and INCT-LCCRT, this showed a trend (P = 0.093). Pre-TNT absolute lymphocyte count (ALC) was an independent predictor of RIL. Small bowel irradiation (V15 Gy > 104 cc) predicted severe lymphopenia during chemotherapy in the univariable analysis; but multivariable analysis suggested pre-TNT ALC as the main factor, showing a trend toward significance (P = 0.051). In the SCRT-CNCT group, pre-TNT ALC was the only significant factor for severe lymphopenia in both the RT and chemotherapy phases in univariable analysis. Severe RIL significantly prolonged lymphocyte recovery time (median, 283 vs. 76 days, P < 0.001), whereas immune recovery did not differ according to the TNT regimen. The median ALC at the last follow-up was 86% of the baseline value, indicating incomplete recovery. While pre-TNT ALC correlated with lymphopenia risk, minimizing bowel irradiation may help mitigate treatment-induced immunosuppression. Prospective studies are required to validate these findings.