Journal of Radiation Research最新文献

Neutron-activated 31Si is an almost pure beta emitter and is one of the short-lived radionuclides, including beta-gamma emitter 56Mn, which were created in a form of residual radioactivity in the early period after the atomic bombing of Hiroshima and Nagasaki. The features of the biological effects of internal irradiation by these radionuclides are a subject of scientific discussions and research. The publication presents data on internal radiation doses in experimental Wistar rats that were exposed to sprayed neutron-activated microparticles of 31SiO2. Doses of internal radiation could be conditionally divided into three groups according to their values. It has been found that elevated values of internal radiation doses in rats' organs/tissues as a result of exposure to sprayed 31SiO2 microparticles with initial activity of 3.2 × 107 Bq varied from 10 to 120 mGy (eyes, lungs, skin, stomach, jejunum, large intestine). The moderate dose values were in the range from 1.9 to 3.7 mGy (trachea, esophagus, ileum). The smallest doses were received by the kidney, testis, blood, cerebellum, heart, liver, cerebrum, bladder, spleen and thymus (from 0.11 to 0.94 mGy). The obtained data are important for interpreting the results of ongoing and planned biological experiments with 31SiO2 microparticles-in comparison with the previously published data on features of biological effects caused by beta-gamma emitting 56MnO2 neutron-activated microparticles.

The meta-analysis was to evaluate the therapeutic benefits of neoadjuvant chemotherapy (NACT), primarily consisting of platinum-based regimens in conjunction with paclitaxel, when integrated with concurrent chemoradiotherapy (CCRT) for individuals afflicted with locally advanced cervical cancer (LACC). The outcomes were determined by overall survival (OS), progression-free survival (PFS), complete response rate (CRR), objective response rate, recurrence rate and adverse events. The assessment of these outcomes was based on the relative risk (RR) accompanied by its 95% confidence interval (CI). Eight articles were included for analysis. LACC patients who underwent treatment with paclitaxel combined with cisplatin (TP)-based NACT in conjunction with CCRT demonstrated improved OS at 2 (RR: 1.11, 95% CI: 1.07, 1.16, P < 0.001), 3 (RR: 1.30, 95% CI: 1.23, 1.37, P < 0.001) and 5 years (RR: 1.20, 95% CI: 1.10, 1.32, P < 0.001), as well as PFS at 1 (RR: 1.03, 95% CI: 1.00, 1.06, P = 0.035), 2 (RR: 1.21, 95% CI: 1.04, 1.40, P = 0.012), 3 (RR: 1.26, 95% CI: 1.17, 1.34, P < 0.001) and 5 (RR: 1.39, 95% CI: 1.25, 1.55, P < 0.001) years, when compared with patients who received CCRT alone. Moreover, the TP-based NACT in conjunction with CCRT achieved a higher CRR and exhibited a lower rate of disease recurrence (RR:1.28, 95% CI:1.08, 1.50, P = 0.003). No significant differences in the risk of adverse effects including anemia, leukopenia, thrombocytopenia, radiocystitis and radiation enteritis between the group treated with TP-based NACT combined with CCRT and the group treated with CCRT alone were observed. The combination of TP-based NACT and CCRT demonstrates superior clinical efficacy than CCRT alone. This study may contribute to reducing the burden of LACC by using TP-based NACT plus CCRT.

To assess the interfractional anatomical range variations (ARVs) with beam directions and their impact on dose distribution in intensity modulated proton therapy, we analyzed water equivalent thickness (WET) from 10 patients with pancreatic cancer. The distributions of the interfractional WET difference ($Delta{mathrm{WET}}^{theta }$) across 360° were visualized using polar histograms. Interfractional ARVs were evaluated using the mean absolute error and ΔWET pass rate, indicating the percentage of $Delta mathrm{WE}{mathrm{T}}^{theta }$ < thresholds. The impact on dose distribution in proton therapy was evaluated based on two treatment plans for 40 Gy(RBE)/5 fractions: 'Plan A', using two beam angles, in which the target was closest to the body surface among four perpendicular directions; and 'Plan B', using two beam angles with small ARVs. Analysis revealed individual variations in angular trends of interfractional ARVs. Three distinct trends were identified: Group 1 exhibited small ARVs around posterior directions; Group 2 exhibited small ARVs except ~60°; Group 3 demonstrated minimal ARVs only ~90°. In dose evaluation, while 150° and 210° were selected in Plan B for 9 out of 10 patients, for the remaining patient, 60° and 90° were chosen. Comparing dose volume histogram parameters for all patients, Plan B significantly reduced target coverage loss while maintaining organ-at-risk sparing comparable to Plan A. These results demonstrated that selecting beam angles with small interfractional ARVs for each patient enhances the robustness of dose distribution, reducing target coverage loss.

Brachytherapy (BT), especially in high dose rate (HDR), has become increasingly complex owing to the use of image-guided techniques and the introduction of advanced applicators. Consequently, radiotherapy technologists and medical physicists (RTMPs) require substantial training to enhance their knowledge and technical skills in image-guided brachytherapy. However, the current status of the RTMP workload, individual abilities and quality control (QC) of BT units in Japan remains unclear. To address this issue, we conducted a questionnaire survey from June to August 2022 in all 837 radiation treatment facilities in Japan involving RTMPs. This survey focused on gynecological cancers treated with HDR-BT (GY-HDR) and permanent prostate implantation using low-dose-rate BT (PR-LDR). The responses revealed that the average working time in the overall process for HDR varied: 120 min for intracavitary BT and 180 min for intracavitary BT combined with interstitial BT. The QC implementation rate, in accordance with domestic guidelines, was 65% for GY-HDR and 44% for PR-LDR, which was lower than the 69% observed for external beam radiation therapy (EBRT). Additionally, the implementation rate during regular working hours was low. Even among RTMP working in facilities performing BT, the proportion of those able to perform QC for BT units was ~30% for GY-HDR and <20% for PR-LDR, significantly lower than the 80% achieved for EBRT. This study highlights the vulnerabilities of Japan's BT unit QC implementation structure. Addressing these issues requires appropriate training of the RTMP staff to safely perform BT tasks and improvements in practical education and training systems.

From the viewpoints of the advantage depths (ADs), peak tumor dose and skin dose, we evaluated the effect on the dose distribution of neutron beam properties, namely the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component and γ-ray component. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20-30% compared with the current recommendation of 5%. The skin dose increased with the increasing thermal/epithermal ratio, reaching a restricted value of 14 Gyeq at a thermal/epithermal ratio of 48%. The fast neutron component was modified using two different models, namely the 'linear model', in which the fast neutron intensity decreases log-linearly with the increasing neutron energy, and the 'moderator thickness (MT) model', in which the fast neutron component is varied by adjusting the MT in a virtual beam shaping assembly. Although a higher fast neutron component indicated a higher skin dose, the increment was <10% at a fast neutron component of <1 × 10-12 Gy cm2 for both models. Furthermore, in the MT model, the epithermal neutron intensity at a fast neutron component of 6.8 × 10-13 Gy cm2 was 41% higher compared with that of 2 × 10-13 Gy cm2. The γ-ray component also caused no significant disadvantages up to several times larger compared with the current recommendation.

Stereotactic radiosurgery (SRS) using the single-isocenter-multiple-target (SIMT) technique by volumetric modulated arc therapy is increasingly popular for treating multiple brain metastases. However, the complex nature of SIMT SRS necessitates rigorous patient-specific quality assurance (PSQA). This study presents a multi-institutional dosimetric commissioning of a high-resolution complementary metal oxide semiconductor (CMOS) 2D detector array, the myQA SRS device for SIMT SRS PSQA. Basic dosimetric properties such as dose-rate, field-size, energy and angular dependencies were characterized for the CMOS detectors. Additionally, gamma index analyses were performed between the measured dose and the films for nine simulated and clinical plans. The results showed that the CMOS detector was dose-rate, field-size, energy and beam-angle dependent. Specific to SIMT SRS, angular dependence on gantry rotations was invariant to couch rotations but was sensitive to off-isocenter distances. With appropriate dose calibration and angular corrections, myQA SRS showed a high dosimetric correlation with films. The average gamma index pass rates were 99.9 ± 0.03% and 99.2 ± 1.1% at 3%/2 mm/10%thr(global) and 1 mm/1%/10%thr(local) criteria, respectively. The average dose difference between myQA SRS and films was 0.4 ± 1.3%. In conclusion, the CMOS 2D detector array has demonstrated its potential as a reliable tool for PSQA for SIMT SRS. The excellent dosimetric agreement with the films was consistent in multiple institutions, further validating the dosimetric accuracy and reproducibility. It provides a timely alternative to film dosimetry for commissioning and quality assurance.

FLASH radiotherapy is an emerging technique in radiation oncology that may improve clinical outcomes by reducing normal tissue toxicities. The physical radiation characteristics needed to induce the radiobiological benefits of FLASH are still an active area of investigation. To determine the dose rate, range of doses and delivery time structure necessary to trigger the FLASH effect, Drosophila melanogaster were exposed to ultrahigh dose rate (UHDR) or conventional radiotherapy dose rate (CONV) 120-kVp X-rays. A conventional X-ray tube outfitted with a shutter system was used to deliver 17- to 44-Gy doses to third-instar D. melanogaster larvae at both UHDR (210 Gy/s) and CONV (0.2-0.4 Gy/s) dose rates. The larvae were then tracked through development to adulthood and scored for eclosion and lifespan. Larvae exposed to UHDR eclosed at higher rates and had longer median survival as adults compared to those treated with CONV at the same doses. Eclosion rates at 24 Gy were 68% higher for the UHDR group (P < 0.05). Median survival from 22 Gy was >22 days for UHDR and 17 days for CONV (P < 0.01). Two normal tissue-sparing effects were observed for D. melanogaster irradiated with UHDR 120-kVp X-rays. The effects appeared only at intermediate doses and may be useful in establishing the dose range over which the benefits of FLASH can be obtained. This work also demonstrates the usefulness of a high-throughput fruit fly model and a low-cost X-ray tube system for radiobiological FLASH research.

We aimed to clarify whether prophylactic cranial irradiation (PCI) is associated with improved outcomes in limited-stage small-cell lung cancer (LS-SCLC) in the current era of magnetic resonance imaging (MRI). Data from patients with LS-SCLC who achieved a complete response to definitive chemoradiotherapy (CRT) at two medical centers were retrospectively reviewed. Propensity score-matching was performed in a 2:1 ratio to balance the baseline characteristics of the no-PCI and PCI groups. The endpoints were the incidence of brain metastasis (BM), neurological causes of death and overall survival (OS). Overall, 80% patients underwent head MRI during the initial staging and 75 patients (no-PCI, n = 50; PCI, n = 25) were matched. Their baseline characteristics were generally well-balanced except for age; patients in the no-PCI group tended to be older. The median follow-up period was 29 months. Although the incidence of BMs tended to be higher in the no-PCI group (1-year BM occurrence: 26% vs 17%, P = 0.22), the incidence of multiple BMs (defined as >4 metastases) was similar between groups (1-year multiple BMs occurrence: 8% vs 9%, P = 0.65). The 2-year neurological causes of death and OS rate did not significantly differ between the groups (6% and 9%; P = 0.85; and 70% and 79%; P = 0.36, respectively). The 1-year occurrence of multiple BMs did not increase, even without PCI, when modern imaging modalities were integrated into the initial diagnosis, suggesting that PCI could be omitted after CRT, if MRI was incorporated into the initial diagnosis and follow-up.

This study aimed to visualize the current situation and trends in radiation therapy in Japan using open data from the Japanese National Database of Health Insurance Claims and Specific Health Checkups (NDB). We downloaded the NDB open data from the website of Japan's Ministry of Health, Labor and Welfare and used Python libraries to analyze the receipt data related to radiation therapy from fiscal year 2014 to 2022. The number of radiation therapy plans peaked in 2019, temporarily declined and subsequently showed a gradual increase. Conversely, the total points associated with radiation therapy have consistently increased without any decline. The use of high-precision radiation therapies such as intensity-modulated radiation therapy (IMRT) has increased over time. Significant regional differences exist, with the Chubu and Kyushu regions showing higher total points and receipts per certified radiation oncologist. A correlation was observed between the number of IMRT plans per population and the number of certified radiation oncologists. Males exhibited a sharp peak in their early 70s, while females demonstrated a mild peak from their 40s to 80s. In recent years, the points for males in their early 70s have rapidly increased. We used the NDB open data to illustrate the current situation and trends in radiation therapy in Japan, highlighting reduced costs and workloads. This study underscored the regional differences in radiation therapy and emphasized the need to discuss strategies for meeting future demand.