Journal of Radiation Research最新文献

Ventricular tachycardia (VT) is a severe arrhythmia commonly treated with implantable cardioverter defibrillators, antiarrhythmic drugs and catheter ablation (CA). Although CA is effective in reducing recurrent VT, its impact on survival remains uncertain, especially in patients with extensive scarring. Stereotactic arrhythmia radioablation (STAR) has emerged as a novel treatment for VT in patients unresponsive to CA, leveraging techniques from stereotactic body radiation therapy used in cancer treatments. Recent clinical trials and case series have demonstrated the short-term efficacy and safety of STAR, although long-term outcomes remain unclear. Imaging techniques, such as electroanatomical mapping, contrast-enhanced magnetic resonance imaging and nuclear imaging, play a crucial role in treatment planning by identifying VT substrates and guiding target delineation. However, challenges persist owing to the complex anatomy and variability in target volume definitions. Advances in imaging and artificial intelligence are expected to improve the precision and efficacy of STAR. The exact mechanisms underlying the antiarrhythmic effects of STAR, including potential fibrosis and improvement in cardiac conduction, are still being explored. Despite its potential, STAR should be cautiously applied in prospective clinical trials, with a focus on optimizing dose delivery and understanding long-term outcomes. Collaborative efforts are necessary to standardize treatment strategies and enhance the quality of life for patients with refractory VT.

Dynamic WaveArc (DWA) is a technique used for continuous, non-coplanar volumetric-modulated arc therapy on the Vero4DRT platform. This study aimed to evaluate the application of single-isocenter DWA (SI-DWA) for treating multiple brain metastases by comparing dose distribution and irradiation time with multi-isocenter DWA (MI-DWA) through retrospective treatment planning. Treatment plans were developed for SI-DWA and MI-DWA in 14 cases with 3-5 brain metastases. Parameters assessed included target dose indices, such as conformity index (CI) of the planning target volume (PTV), volumes of normal brain excluding gross tumor volumes (GTVs) receiving a single dose equivalent of 14 Gy (V14), V30%, V20%, V10%, volumes of normal brain, including GTVs receiving a single dose equivalent of 12 Gy (V12), D2% for other organs at risk, and beam-on time. SI-DWA showed inferior CI, V14, and V12 values for lesions with PTV volumes <1 cc, whereas it performed equivalently to MI-DWA for lesions with PTV volumes ≥1 cc. SI-DWA resulted in higher volumes of normal brain receiving low doses compared to MI-DWA. SI-DWA exhibited significantly shorter beam-on times than MI-DWA. In conclusion, SI-DWA is an effective method for treating multiple brain metastases with PTV volumes ≥1 cc, offering an index of radiation-induced brain necrosis comparable with MI-DWA while allowing for shorter irradiation times.

We assessed the effect of beam size on plan robustness for intensity-modulated proton therapy (IMPT) of head and neck cancer (HNC) and compared the plan quality including robustness with that of intensity-modulated radiation therapy (IMRT). IMPT plans were generated for six HNC patients using six beam sizes (air-sigma 3-17 mm at isocenter for a 70-230 MeV) and two optimization methods for planning target volume-based non-robust optimization (NRO) and clinical target volume (CTV)-based robust optimization (RO). Worst-case dosimetric parameters and plan robustness for CTV and organs-at-risk (OARs) were assessed under different scenarios, assuming a ± 1-5 mm setup error and a ± 3% range error. Statistical comparisons of NRO-IMPT, RO-IMPT and IMRT plans were performed. In regard to CTV-D99%, RO-IMPT with smaller beam size was more robust than RO-IMPT with larger beam sizes, whereas NRO-IMPT showed the opposite (P < 0.05). There was no significant difference in the robustness of the CTV-D99% and CTV-D95% between RO-IMPT and IMRT. The worst-case CTV coverage of IMRT (±5 mm/3%) for all patients was 96.0% ± 1.4% (D99%) and 97.9% ± 0.3% (D95%). For four out of six patients, the worst-case CTV-D95% for RO-IMPT (±1-5 mm/3%) were higher than those for IMRT. Compared with IMRT, RO-IMPT with smaller beam sizes achieved lower worst-case doses to OARs. In HNC treatment, utilizing smaller beam sizes in RO-IMPT improves plan robustness compared to larger beam sizes, achieving comparable target robustness and lower worst-case OARs doses compared to IMRT.

This retrospective study aimed to compare the clinical outcomes of intensity-modulated radiation therapy (IMRT) and proton beam therapy (PBT). A total of 606 patients diagnosed with prostate cancer between January 2008 and December 2018 were included. Of these patients, 510 received PBT up to a dose of 70-78 Gy (relative biological effectiveness) and 96 patients received IMRT up to a dose of 70-78 Gy. The median follow-up period was 82 months (range: 32-140 months). Patients in the PBT group had significantly higher 7-year rates of biochemical relapse-free survival (bRFS) and disease-free survival (DFS) rates: 95.1% for PBT vs 89.9% for IMRT (P = 0.0271) and 93.1% for PBT vs 85.0% for IMRT (P = 0.0019). After matching analysis, 94 patients were assigned to both groups, and the PBT group showed significantly higher 7-year bRFS and DFS rates: 98.9% for PBT vs 89.7% for IMRT (P = 0.023) and 93.4% for PBT vs 84.6% for IMRT (P = 0.022), respectively. In the subgroup analysis of intermediate-risk patients, the PBT group showed a significantly higher 7-year bRFS rate (98.3% for PBT vs 90.5% for IMRT; P = 0.007). The V60 of the bladder in the PBT group (18.1% ± 10.1%) was higher than that in the IMRT group (14.4% ± 7.6%) (P = 0.024). This study found that the treatment outcomes of PBT potentially surpassed those of IMRT specifically concerning bRFS and DFS in real-world settings. However, it should be noted that attention is warranted for late bladder complication of PBT.

The accelerator-based boron neutron capture therapy (BNCT) system has been approved for specific cases covered by health insurance, and clinical trials for new cases in Japan are currently being conducted on other systems. Owing to the progress of accelerator-based BNCT, the operation of medical physics must be rendered more efficient. A water phantom is used for the quality assurance (QA) of the BNCT beam output procedure; however, a solid phantom is preferred for routine QA because of its ease of use. Additionally, because water phantoms cannot be readily used in some facilities owing to structural problems, solid phantoms are preferred for unified measurements at different facilities to compare beam outputs. In this study, we perform irradiation tests using an acrylic phantom and verify that an acrylic phantom can be used for QA. The distribution of thermal neutron flux and gamma-ray dose rate inside the acrylic phantom are evaluated through experiments and simulations. The results indicate that the acrylic phantom is suitable for routine QA and for comparing beam outputs among different systems. In the future, the same irradiation tests will be conducted at other facilities.

Between 1949 and 1962 the Soviet Union performed atmospheric tests of nuclear weapons at the Semipalatinsk nuclear test site (SNTS) in Kazakhstan, resulting in widespread contamination of the surrounding region with radioactive fallout. Settlements in the southeast Abai oblast of Kazakhstan, close to the border with China, are not thought to have received significant fallout from the SNTS. There is, however, evidence that the study area, including Makanchi, Urdzhar and Taskesken villages, was contaminated by atmospheric nuclear tests performed by China at the Lop Nor NTS between 1964 and 1980. We identified the most reliable data indicating contamination from the Lop Nor tests from archive documents. Prompt sampling of soil performed in the area revealed elevated levels of total beta activity in the days and weeks following the Lop Nor tests. The highest activities were recorded following the thermonuclear tests in June 1967 and June 1973. Tooth enamel dosimetry using electron paramagnetic resonance methods suggests residents of the study area have been exposed to excess doses of 50-60 mGy but provides no information on the source and timing of exposure. Currently, evidence of contamination of the study area from nuclear weapons testing at Lop Nor is based on limited radiation measurement data. Therefore, work will continue on the search for archival data on radiological and meteorological monitoring carried out in the study area at the time of the Lop Nor testing campaign.

Radiobiological studies are ongoing to understand the consequences of internal exposure to neutron-activated radioactive microparticles, which were sprayed over experimental rats and mice. Special attention in these experiments is given to internal irradiation with radioactive microparticles with short-lived neutron-activated radionuclides 31Si (T1/2 = 2.62 h) and 56Mn (T1/2 = 2.58 h), which are among the main dose-forming factors from residual radioactivity activated in soils by neutrons in the first hours after atmospheric nuclear explosions. The presented work is devoted to microdosimetry peculiarities of 31SiO2 and 56MnO2 microparticles. The radiation from 31Si consists of intensive short-range beta particles and gamma rays with very low intensity. It differs from the radiation of 56Mn, which includes intensive beta particles, low energy Auger electrons and very intensive gamma rays. Differences in the energies and intensities of short-range beta particles and penetrating gamma rays emitted by 31SiO2 and 56MnO2 microparticles can lead to differences in the spatial microdistribution of absorbed dose around the corresponding radioactive microparticles embedded in biological tissue. It was found in the presented work that the absorbed doses of beta radiation emitted by 56MnO2 and 31SiO2 microparticles has significant but different spatial gradients with distances in biological tissue that correspond to the typical thickness of epithelial cells of lungs' alveoli and bronchioles. The results obtained are necessary for a better understanding of radiobiological effects of internal exposure by radioactive microparticles with 56Mn and 31Si observed in framework of performed and ongoing radiobiological studies with experimental animals-rats and mice.

The National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) is a database that stores anonymized information on medical receipts and health checkups in Japan. The NDB Open Data is a publicly accessible summary table of the NDB database. To reveal annual trends and regional disparities in radiotherapy utilization in Japan, we analyzed the NDB Open Data tables for a 9-year period from 2014 to 2022. We extracted medical cost codes for radiotherapy management fees and specific types of radiotherapy, such as stereotactic irradiation (STI) and intensity-modulated radiotherapy (IMRT), to analyze nationwide changes over time. To investigate regional disparities, we counted the three subitems representing 3-dimensional conformal radiotherapy (3D-CRT), IMRT, and STI for each prefecture per year. The utilization of advanced radiotherapy techniques, such as IMRT (199% increase), increased, while the use of simpler forms of irradiation, such as 1 or 2-opposite fields irradiation (40% decrease), decreased in the period from 2014 to 2022. Regarding regional disparities, the coefficients of variation in 47 prefectures for 3D-CRT remained relatively stable at 0.17 in 2014 and 0.18 in 2022, while the coefficients of variation for IMRT and STI decreased from 0.64 and 0.39 in 2014 to 0.31 and 0.36 in 2022, respectively. The popularization of IMRT was correlated with the number of certified radiation oncologists in the prefecture. In conclusion, although the utilization of high-precision radiotherapy in Japan has been increasing and regional differences have been diminishing, there are still persistent disparities.

The current research on staffing models is primarily focused on conventional external photon beam therapy, which predominantly involves using linear accelerators. This emphasizes the need for comprehensive studies to understand better and define specific particle therapy facilities' staffing requirements. In a 2022 survey of 25 particle therapy facilities in Japan with an 84% response rate, significant insights were obtained regarding workload distribution, defined as the product of personnel count and task time (person-minutes), for patient-related tasks and equipment quality assurance and quality control (QA/QC). The survey revealed that machinery QA/QC tasks were particularly demanding, with an average monthly workload of 376.9 min and weekly tasks averaging 162.1 min. In comparison, patient-related workloads focused on treatment planning, exhibiting substantial time commitments, particularly for scanning and passive scattering techniques. The average workloads for treatment planning per patient were 291.3 and 195.4 min, respectively. In addition, specific patient scenarios such as pre-treatment sedation in pediatric cases require longer durations (averaging 84.5 min), which likely include the workloads of not only the physician responsible for sedation but also the radiotherapy technology and medical physics specialists providing support during sedation and the nursing staff involved in sedation care. These findings underscore the significant time investments required for machinery QA/QC and patient-specific treatment planning in particle therapy facilities, along with the need for specialized care procedures in pediatric cases. The results of this survey also emphasized the challenges and staffing requirements to ensure QA/QC in high-precision medical environments.