Journal of Radiation Research最新文献

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.

Studies on health effects of radiation exposure to residents around the Semipalatinsk nuclear test site (SNTS), Kazakhstan, are necessary for epidemiological assessment of radiation-related health risks after low-dose irradiation. Radiation dose estimates are the principal point for radiation epidemiological studies. These estimates should be based on the most reliable initial data, used for dose estimations. The comparative critical analysis of various available archival and published initial data, namely values of historical exposure dose rates and values of soil contamination by 137Cs in considered settlements, including information about dates, times and locations of measurements, was performed with the aim to select most reliable and realistic initial data necessary for estimation of settlement-average accumulated external doses for some settlements located in the vicinity of radioactive clouds' trajectories related to the most significant tests at the SNTS. Results of estimation of accumulated external radiation dose to air, based on these selected initial data, are presented for 18 settlements. Calculated accumulated external doses were compared with retrospective instrumental dose estimates for settlements, where data on TL/OSL luminescence retrospective dosimetry with quartz-containing samples or electron spin resonance (ESR) dosimetry with tooth enamel were available. Estimation of settlement-average external radiation dose to air is the first important step necessary for the next step-individualized radiation dose estimations among different age, professional and ethnic-specific groups of population lived in the study settlements considering behavior, shielding, location and relocation factors in each population group. This is a subject of future work.

Microplastics (MPs) have been detected in multiple human organs, raising concerns about their potential health risks. The intestinal tract is particularly vulnerable to MPs exposure and accumulation. Radiotherapy often causes side effects such as radiation-induced intestinal injury (RIII). Although previous studies have shown that MPs exacerbate RIII by altering gut microbiota, their effect on the small intestine's intrinsic sensitivity to radiation remains unclear. In this study, C57BL/6 mice were preexposed to MPs for a short period and then irradiated with 4 or 10 Gy to evaluate intestinal injury. Proteomic analysis of small intestine was performed to identify changes in protein expression. Short-term MPs exposure alone caused minimal intestinal damage. While 4 Gy irradiation did not cause significant intestinal injury, 10 Gy irradiation induced pronounced inflammation, increased epithelial apoptosis, and disrupted villus and lamina propria architecture. Importantly, the mice preexposed to MPs exhibited significantly increased sensitivity to RIII. Furthermore, prior MPs exposure significantly exacerbated RIII at 4 Gy but had no obvious influence on RIII at 10 Gy in C57BL/6 mice. The reason might be that the severe radiation-induced injury caused by 10 Gy could obscure the additional effects of prior MPs exposure. Proteomic analysis implicated the 'PI3K-Akt signaling' pathway as a key mediator of this effect. Indeed, treatment with a PI3K inhibitor could attenuate the MPs-driven susceptibility of small intestine to radiation. These findings underscore the need to minimize MPs exposure in patients undergoing radiotherapy.

In recurrent gynecologic malignancies following prior pelvic irradiation, definitive radiation therapy is often precluded by cumulative dose constraints to adjacent organs at risk (OARs), and patients may be left with only highly invasive surgical options such as total pelvic exenteration. While some institutions have explored displacement techniques such as artificial ascites or hyaluronic acid gel injection, these approaches are not widely adopted and frequently fail to ensure consistent and stable separation of OARs. We report the first clinical use of Neskeep®, a bioabsorbable polyglycolic acid (PGA) spacer, in high-dose-rate (HDR) brachytherapy for recurrent cervical cancer after prior pelvic radiation. A woman in her 40s with prior hysterectomy and HDR brachytherapy for cervical intraepithelial neoplasia grade III developed vaginal stump recurrence 4 years later. Laparoscopic placement of the PGA spacer was performed to achieve durable displacement of the small bowel, followed by eight fractions of HDR brachytherapy. Hyaluronic acid gel was also injected during each fraction to displace the bladder and rectum. The spacer maintained position and volume throughout treatment without complications. Dose-volume analysis showed a marked reduction in small bowel D₂cc (mean equivalent dose in 2 Gy fractions (EQD₂): 121.6 cGy) compared to the initial treatment (606.0 cGy), while the spacer itself received a mean D₂cc of 690.3 cGy. MRI confirmed complete response at 2 months, with no adverse events observed at that time point. The PGA spacer enabled safe, curative reirradiation in a case that would otherwise be unsuitable for further radiation therapy.

Skin is a tissue vulnerable to radiation exposure, which causes acute tissue reactions, including erythema, edema, desquamation, ulceration and late effects, such as skin cancers. As the effects of radiation exposure on the skin tissue are easily evaluated by visual examination, much information on radiation-induced skin reactions has been available from the clinical observation of people exposed to ionizing radiation, such as cancer patients receiving radiotherapy, although the mechanisms underlying skin reactions have not yet been fully understood. Recent advances in tissue biology at the molecular level have provided insights into the mechanisms of skin tissue reactions from the stem cell points of view. For example, our understanding of epidermal regeneration by epidermal stem cells as well as cells from the bulge in humans and the sebaceous gland in mouse, descriptions of the role of skin immune cells on inflammatory response and maintenance of genome integrity by epidermal stem cell competition, have greatly improved in the last decade with the identification of several key molecules. Thus, this review will provide an overview of the current status toward the comprehensive understanding of the mechanisms of adverse skin tissue reactions, with respect to mitigation of acute skin injuries as well as late carcinogenesis in response to ionizing radiation. In particular, the pleiotropic features of various types of cells consisting of skin tissue and their roles in securing skin functional homeostasis will be discussed.

The purpose of this systematic review and meta-analysis was to evaluate the efficacy and safety of stereotactic body radiotherapy using CyberKnife (CK) for liver-confined hepatocellular carcinoma (HCC). A systematic review was performed on studies published between 2000 and 2024 that reported treatment outcomes including overall survival (OS), local control (LC), and complications. A literature search was performed using MEDLINE/PubMed with the following terms: ('Carcinoma, Hepatocellular'[MeSH Terms] OR 'hepatocellular carcinoma' OR 'HCC') AND ('CyberKnife' OR 'robotic radiosurgery'). Additional searches were conducted on Scopus and the Cochrane library using following terms: 'Hepatocellular carcinoma' AND 'CyberKnife.' A meta-analysis was performed to assess OS and LC using weighted random effects models. Five retrospective studies and one prospective study were included in the meta-analysis, comprising a total of 697 patients with a median follow-up duration was 31 months (range: 15-48 months). The pooled 3-year LC and OS rates were 82.5% (95% confidence interval [CI], 75.0%-90.0%) and 58.7% (95% CI, 47.2%-70.1%), respectively, which is comparable to previous reported outcomes for non-device-limited SBRT and similar to that of surgery and local ablative therapies. The incidence of radiation-induced liver disease was 4.3%-15.3%. Stereotactic body radiotherapy using CK appears to be an effective and well-tolerated treatment for liver-confined HCC. However, further prospective studies with standardized methodologies are warranted to establish solid evidence of its clinical utility.

YTHDF2, a N6-methyladenosine (m6A) recognition protein, is involved in the occurrence and progression of various malignancies. The impact of YTHDF2 on the radiosensitivity of rectal cancer cells remains unclear. This study aimed to investigate the effect and potential mechanisms of YTHDF2 on radiotherapy sensitivity in rectal cancer. Acquired radioresistant colorectal cancer (CRC) cell lines (HCT-116-R and CX-1-R) were established through accumulative X-ray exposure. YTHDF2 was exogenously overexpressed or endogenously knocked down using lentivirus systems, and the radiosensitivity of the cells was analyzed both in vitro and in vivo. High-throughput transcriptome sequencing identified MYC as a downstream target of YTHDF2. RNA stability assays revealed that YTHDF2 facilitated the decay of MYC messenger (mRNA) through an m6A-dependent mechanism. Western blot analyses demonstrated that YTHDF2 modulated MYC expression and the Hippo signaling pathway, enhancing p-MST1/2, p-LATS1 and p-YAP levels while reducing nuclear YAP. Functional assays showed that YTHDF2 overexpression improved radiosensitivity by promoting radiation-induced apoptosis and G2/M phase arrest. MYC overexpression reversed these effects, suggesting a competitive regulatory relationship between YTHDF2 and MYC. These findings indicate that YTHDF2 modulates radiosensitivity through MYC and the Hippo signaling pathway. YTHDF2 enhances the radiosensitivity of rectal cancer cells by facilitating the degradation of MYC mRNA and activating the Hippo signaling pathway. Targeting YTHDF2 may provide a promising therapeutic strategy for overcoming radioresistance in rectal carcinoma.

The International Commission on Radiological Protection has reduced the occupational eye lens dose limit to 20 mSv/year. Interventional radiology (IR) physicians are frequently exposed to high levels of scattered X-rays, and radiation protection tools, including lead glasses, are used for minimizing exposure. However, the effectiveness of lead eyewear for radiation workers who wear prescription glasses (e.g. over-glasses-type eyewear) has not been comprehensively investigated. This study evaluated the shielding effectiveness of over-glasses-type eyewear worn over plastic prescription glasses through phantom experiments. Furthermore, the dose reduction provided by the plastic lenses and front frame of the prescription glasses (excluding lead) was assessed. The over-glasses-type eyewear demonstrated high shielding effectiveness, with average shielding rates of 0.72-0.74 and 0.74-0.80 for the left and right eyes, respectively, against radiation incident from the lower left oblique, as typically encountered in clinical settings. In contrast, the plastic lenses of prescription glasses provided <9% dose reduction when it irradiated with 80- and 120-kV X-rays, indicating minimal contribution to eye protection. The plastic front frame offered a 14% reduction at 80 kV and 11% at 120 kV. These findings suggest that the front frame of the prescription glasses contributes to photon attenuation and improves overall shielding. However, the improper fit of over-glasses-type eyewear may lead to gaps, compromising its shielding effectiveness. To minimize gaps and optimize protection, IR physicians should select over-glasses-type eyewear that fits securely over prescription glasses. Additionally, combining protective tools is essential for effective eye protection.