Journal of Radiation Research最新文献

Image-guided passive scattering proton therapy (PSPT) has been widely adopted in Japan and worldwide, with substantial long-term clinical data supporting its efficacy in treating prostate cancer. However, as hypofractionated protocols become increasingly common, the impact of internal anatomical shifts on surrounding organs at risk (OARs) warrants renewed attention. The pubic bones, situated near the prostate, are often exposed to unintended high doses, especially during internal error correction based on fiducial marker alignment. This study retrospectively analyzed 30 patients with localized prostate cancer treated with PSPT using lateral opposed fields. Simulated isocenter shifts were applied anteriorly and inferiorly in 2-mm increments up to 10 mm to assess dose changes to the pubic bones. Dose-volume histogram metrics including V80%, V90% and V95% were evaluated. Pubic bones dose increased in both shift directions, with a more pronounced effect for anterior shifts, with a 10-mm anterior shift increasing V80% by 14.2 cc on average-2.4 times greater than inferior shifts. Dose elevation correlated strongly with the anatomical proximity between the clinical target volume and pubic bones (r > 0.66, P < 0.001). These results suggest that anterior correction in PSPT can cause substantial dose escalation to the pubic bones, potentially increasing the risk of insufficiency fractures. As extreme hypofractionation becomes more common, careful evaluation of pubic bones dose should be incorporated into treatment planning, alongside traditional OARs such as the rectum and bladder. Early replanning should be considered when persistent anterior displacement is observed to maintain patient safety and quality of life.

Investigation on tritium (3H) washout process in a tropical region at Kakrapar Atomic Power Station (KAPS), Gujarat, India was carried out. 3H concentration in air as well as that in rainwater is estimated near KAPS Site having Pressurized Heavy Water Reactors (PHWRs) operational. Samples were collected covering the four rainy seasons from 2016 to 2019. The corresponding meteorological parameters of relative humidity, ambient temperature, wind speed, wind direction, and atmospheric stability were measured. The rain spectral characteristics such as raindrop diameter, fall velocity, liquid water content (LWC) in raindrops and average rain rate are also studied. Site-specific wet deposition rate (Bq m-2 s-1) and washout coefficient for 3H (s-1) is observed to be in the range of 1.4E-05 to 4.8E-01 (Geometric Mean = 5.3E-03) and 1.1E-07 to 3.6E-02 (Geometric Mean = 4.1E-05) respectively. Significant and positive correlation was observed between average rain rate and washout coefficient (R2 = 0.73). Significant and negative correlation was observed between raindrop diameter of different rain events and 3H activity in rainwater (R2 = 0.70).

Radiation exposure is a significant risk factor for various tumors and illnesses, with early-stage radiation dose closely linked to disease progression. Accurate assessment of radiation exposure is critical for effective treatment. This study aimed to identify radiation-induced DNA damage repair-related genes using weighted gene co-expression network analysis on datasets GSE90909 and GSE102971, supplemented by literature. A protein-protein interaction network was constructed to identify key genes, and their expression levels were compared between irradiated and control groups to evaluate diagnostic efficacy. Immune-related scores were calculated, and correlations between diagnostic genes and immune cells were analyzed. Regulatory networks involving transcription factors (TFs), microRNAs (miRNAs) and key genes were established, alongside gene interaction networks using GeneMANIA. A gene-drug interaction network was also developed. Five key genes-PCNA, REV3L, POLH, LIG1 and XPC-were identified, all significantly overexpressed in irradiated populations. These genes demonstrated strong diagnostic capability for radiation exposure and were positively correlated with radiation dose. Their expression levels were also closely associated with immune cell infiltration, including natural killer cells, plasma cell-like dendritic cells and regulatory T cells. Key regulatory interactions involved TFs (E2F1, TP53) and miRNAs (miR-145, miR-143), while associated genes included FEN1, REV1 and CDKN1A. Drugs linked to these genes included Quercetin and Hydroxyurea. In conclusion, the study identified five key genes with diagnostic potential for radiation exposure, positively correlated with radiation dose. These findings provide a foundation for radiation diagnosis and dose assessment, particularly in populations with later-stage diseases.

Quad Shot (QS) is effective in treating head and neck cancer; however, few prospective studies have been conducted in this direction. Further, no studies have investigated tumor pain and stomatitis pain separately. We prospectively investigated the efficacy and adverse events of QS in 11 patients with head and neck cancer who underwent QS at our hospital in Japan between 2018 and 2024. The QS method involved administering 3.7 Gy twice daily for 2 days, which was considered one course and provided thrice at an interval of 4 weeks. We assessed quality of life (QOL) scores, albumin levels, and numerical rating scale (NRS) scores for stomatitis and tumor pain before and after QS to evaluate changes in NRS. Eleven patients with advanced head and neck cancer received QS treatment: six patients underwent three courses, three underwent two, and two underwent one. There was no significant difference in QOL scores before and after QS, but albumin levels dropped significantly after QS. NRS due to stomatitis significantly worsened after QS, whereas NRS due to tumor significantly improved. Tumor size decreased and tumor NRS improved as the QS treatment duration increased. However, stomatitis was almost always present, and NRS scores for stomatitis increased significantly after treatment. In conclusion, QS can alleviate tumor pain but may worsen stomatitis. Therefore, stomatitis care should be emphasized during treatment. Furthermore, the decrease in albumin levels is likely due to stomatitis-induced decreased appetite; therefore, stomatitis management is also important for maintaining nutritional status.

This survey was conducted to examine the real-world practice of definitive chemoradiotherapy (CRT) for locally advanced non-small cell lung cancer (LA-NSCLC) in Japan, aiming to standardize treatment, reduce inter-institutional disparities and identify areas for future research. A questionnaire was sent to members of the Japanese Radiation Oncology Study Group through a mailing list, with responses collected between December 15, 2023, and March 14, 2024. Responses from 112 institutions revealed that 81.2% either did not set general upper age limits or established limits at 80 years or older for definitive CRT in LA-NSCLC. The most common absolute contraindications were active interstitial pneumonia (60.7%) and contralateral hilar lymph node metastasis (42.0%). Relative contraindications involved dose-volume indices of the normal lung (70.5%). The most commonly adopted dose-volume indices were lung V20Gy < 30%, lung V5Gy < 60% and mean lung dose <20 Gy, while no definite indices were established for heart V50Gy and mean heart dose in half of the institutions. Additionally, 88.4% of institutions reported using IMRT for LA-NSCLC. Involved-field radiotherapy (IFRT) was adopted regardless of institutional size, and institutions with higher IMRT usage for LA-NSCLC also had higher IFRT adoption rates. In conclusion, this nationwide survey revealed the expanded use of definitive CRT and a growing emphasis on reducing lung dose to mitigate pulmonary toxicities, facilitated by advancements in IMRT and IFRT. Regularly conducting these surveys is essential to monitor evolving treatment strategies.

Helical tomotherapy-based total body irradiation (TBI) traditionally employs megavoltage computed tomography (MVCT) for image-guided setup; however, its 390 mm field of view (FOV) and long acquisition times constrain workflow efficiency and whole-body alignment. This study evaluated whether a newly implemented whole-body fan-beam kilovoltage CT (kVCT; 500 mm FOV) can streamline this process. In a retrospective study involving 14 patients treated with a Radixact X9 system (September 2021-September 2023), we timed the patient setup, imaging, registration, re-setup, and beam delivery for each upper-body (UB) and lower-body (LB) segment. Residual setup errors were measured along the lateral, longitudinal, and vertical axes. The kVCT shortened the initial setup cycle (setup + imaging + registration) from 25.4 ± 4.6 to 15.9 ± 3.3 min for UB and from 14.5 ± 3.8 to 9.4 ± 2.4 min for LB (P < 0.001 for both). The total fraction time, including delivery time, decreased from 71.8 ± 7.5 to 56.7 ± 5.3 min. When residual errors exceeded 5 mm, the additional time required for a second cycle was nearly halved with kVCT (7.3 vs. 14.3 min for UB; 4.8 vs. 8.2 min for LB). The kVCT maintained mean absolute residual errors below 2 mm in all axes, and every 95th-percentile value remained within the 5 mm tolerance recommended for tomotherapy-based TBI. These time savings are expected to reduce intrafraction motion and staff workload. Overall, whole-body kVCT enables faster, comprehensive image guidance while preserving accuracy, thereby streamlining tomotherapy-based TBI and reducing the burden on patients and clinical staff.

Since 2018, the staging system and guidelines for cervical cancer have been revised in Japan. Here, we analyzed trends in radiotherapy use among patients with cervical cancer in Osaka Prefecture, Japan. We obtained records from hospital-based cancer registries (2016-23) linked to Diagnosis Procedure Combination data (2019-23), from 67 nationally or prefecturally designated cancer care hospitals. Eligible patients had epithelial or neuroendocrine cervical cancer, excluding those with clinical stage 0 or unknown clinical stage with pathological stage 0. Between 2016 and 2023, the number of patients per year remained stable (717-787); the number of stage IB-IIA (FIGO 2018) cases decreased, whereas that of stages IIB or IIIC (T1-2) cases increased. The number of patients receiving radiotherapy as initial treatment increased from 229 in 2016 to 294 in 2023; this was accompanied by a decline in surgical treatment. The proportion of patients undergoing radiotherapy increased from 11.9% to 17.2% for stage IB-IIA, from 55.6% to 71.7% for stage IIB and from 38.0% to 69.5% for stage IIIC (T1-2). Among 11 institutions providing brachytherapy, the number of radiotherapy cases increased at three, whereas it remained stable or declined at the other eight. These findings indicate a growing trend in radiotherapy use for cervical cancer in Osaka Prefecture; however, the increase varied by institution. To sustain cervical cancer radiotherapy services, further studies may be needed to assess the adequacy of brachytherapy staffing, explore the financial feasibility of brachytherapy equipment, and examine the potential implications of brachytherapy centralization.

This study aimed to evaluate the radioprotective effects of melatonin on healthy thyroid and laryngeal tissues exposed to head and neck radiotherapy using flattening filter (FF) and flattening filter-free (FFF) radiotherapy beams. Forty-eight female Wistar albino rats were randomly assigned to five groups (n = 8): control, only melatonin, FF, FF + melatonin, FFF and FFF + melatonin. A single 16 Gy dose of radiation was delivered to the head and neck region using a linear accelerator. Melatonin (50 mg/kg) was administered intraperitoneally 15 minutes prior to irradiation. Biochemical parameters including malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were measured from serum samples. Histopathological evaluations of thyroid (inflammation, epithelial hyperplasia, follicular hyperplasia, C-cell hyperplasia, cellular degeneration, follicular cell hypertrophy and cellular necrosis) and laryngeal (general morphological deterioration, inflammation, oedema, epithelial destruction, karyorrhexis and karyolysis) tissues were performed using a semi-quantitative scoring system. FF and FFF beam exposure significantly increased MDA and MPO levels while reducing antioxidant enzyme activities (SOD, CAT, GPx) compared to the control group (P < 0.05). Histologically, both radiation types induced marked inflammation, cellular damage and morphological degeneration in thyroid and laryngeal tissues. Melatonin administration significantly reversed these effects, improving antioxidant enzyme levels and mitigating tissue damage (P < 0.05). No statistically significant difference was observed between FF and FFF groups in either biochemical or histological outcomes. FF and FFF beams produced comparable levels of oxidative and structural damage in healthy tissues. Melatonin demonstrated significant radioprotective effects through both biochemical and histopathological pathways, suggesting its potential role in mitigating radiotherapy-induced toxicity in non-target tissues.

Two chemical dosimeters, lithium formate monohydride (LFM) and L-alanine (ALA), were first evaluated under ultra-high dose rate (UHDR) proton irradiation conditions, known as 'FLASH', which has the potential to reduce the impact on normal tissue while effectively killing tumors, using electron spin resonance (ESR) spectroscopy. Both ALA and LFM demonstrated a significant linear increase in ESR peaks that correlated with the physical dose when comparing conventional radiation (CONV) to UHDR radiation. The relative effectiveness (RE: the ratio of the amount of free radicals produced by each type of proton irradiation to the amount produced by 60Co γ-ray irradiation) was determined for CONV, UHDR-Plateau and UHDR-Peak, yielding RE values of 0.849, 0.731 and 0.661 for LFM and 0.834, 0.692 and 0.624 for ALA, respectively. The decrease in RE values was likely due to the combination of UHDR and the increase of linear energy transfer (LET) to facilitate the recombination of radicals formed within the crystal during CONV and UHDR of proton beams. When using the height of the ESR central peak as an indicator of sensitivity, LFM was assessed to be ~20% more sensitive than ALA.

This study evaluates current practices and challenges associated with computed tomography number-to-mass density (CT-MD) conversion tables in helical tomotherapy across Japan and explores directions for standardization and quality improvement amid the increasing adoption of adaptive radiotherapy (ART). A nationwide web-based survey was conducted across 34 institutions utilizing the Radixact system. Data were collected on CT acquisition protocols, calibration phantoms, density plugs, reconstruction algorithms, table registration timing and quality assurance (QA) frequency. Registered CT-MD tables were categorized by CT modality: Simulation CT (SimCT), ClearRT and CTrue. ClearRT tables were analyzed by phantom setup (full vs half), and CTrue tables by reconstruction method [filtered back projection (FPB) vs iterative reconstruction (IR)]. Inter-institutional variations in CT numbers and the number of data points were assessed. SimCT tables exhibited the widest variation in the number of data points (median = 10) and high-density CT numbers. ClearRT tables (median = 8) showed variations of up to 300 Hounsfield units (HU) in cortical bone; the half-phantom setup reduced inter-institutional variability. CTrue tables (median = 8) demonstrated high consistency, with negligible differences between IR and FPB. All plug CT numbers of CTrue remained within the tolerance defined by the American Association of Physicists in Medicine Task Group 148. However, CT numbers for air plugs varied by ~±30 HU, indicating inconsistent handling of air reference values. Additionally, 43% of institutions did not perform routine QA. Standardizing phantom geometry, air CT number handling and QA protocols-particularly using half-phantom calibration-may improve CT-MD table consistency and dose accuracy in ART.