Radiation

Salivary glands are common organs at risk in both head and neck external beam radiotherapy (EBRT) and radiopharmaceutical therapy (RPT), but incidences of xerostomia in RPT are inconsistent with the EBRT Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) limits. In EBRT, salivary glands are usually assumed to be parallel organs, with QUANTEC guidelines based on $D_{mean}$, but this is known to be a gross over-simplification of the full complexity of the underlying functional organization. The goal of this work is to combine machine learning of EBRT dose–outcome data with stylized small-scale RPT dosimetry to discover more reliable normal tissue complication probability (NTCP) models of xerostomia across both modalities. A retrospective cohort of 211 EBRT patients was analyzed using a custom-designed in-house machine learning workflow. From this, a hierarchy of three models of increasing complexity was trained, evaluated for performance and generalization, and coupled with stylized small-scale salivary gland dosimetry to assess the influence of model complexity on the predicted NTCP for plausible patterns of RPT dose nonuniformity. The three models in the hierarchy (A, B, C), in increasing order of complexity, associate xerostomia with the following: the mean dose to the whole contralateral parotid (model A), the mean dose to a ductally localized region (model B) and a serial interaction dose term between two ductal sub-compartments (model C). While the difference between the three models for EBRT p-values and AUCs is rather marginal, for physiologically driven ductal dose distributions in RPT, the predicted reduction in TD50 can be as large as a factor of 10. These results provide hints towards a plausible reconciliation of the observed inconsistency of xerostomia in RPT with EBRT dose limits. Full article

Radiomics and deep learning computer vision algorithms can extract clinically relevant information from medical images, providing valuable insights for accurate diagnosis of cancerous lesions, tumor differentiation and molecular subtyping, prediction of treatment response, and prognostication of long-term outcomes. In head and neck squamous cell carcinoma (HNSCC), growing evidence supports the potential role of radiomics and deep learning models in predicting treatment response, long-term outcomes, and treatment complications following radiation therapy. This is especially important given the pivotal role of radiotherapy in early-stage and locally advanced HNSCC, as well as in post-operative and concomitant chemoradiotherapy. In this article, we summarize recent studies highlighting the role of radiomics in predicting early post-radiotherapy response, locoregional recurrence, survival outcomes, and treatment-related complications. Radiomics-guided tools have the potential to personalize HNSCC radiation treatment by identifying low-risk patients who may benefit from de-intensified therapy and high-risk individuals who require more aggressive treatment strategies. Full article

Effective dose calculation is essential for optimizing Gamma Knife (GK) stereotactic radiosurgery (SRS) treatment plans. Modern GK systems allow independent sector activation, enabling complex dose distributions per shot. This study presents a dose approximation method designed to account for shot flexibility and generate 3D doses external to GammaPlan. A treatment plan was created with the TMR10 calculation for individual sector activations using a Radiosurgery Head Phantom. The resulting dose arrays established a basis set of sector-specific distributions, which were then referenced by shot parameters from the plan, allowing dose accumulation through superposition. This superposition approximation (SA) was compared to the original TMR10 using the Dice Similarity Coefficient (DSC), 95% Hausdorff Distance (HD95), and GK deliverability metrics: coverage, selectivity, and gradient index, across an isodose normalization range from 10% to 90%. In a cohort of 30 patients with 71 targets, strong agreement was observed between TMR10 and SA in the clinically used 50–60% isodose range, with DSC above 85% and HD95 under 2.18 mm. The average differences for the coverage, selectivity, and gradient index were 0.014, 0.008, and 0.118, respectively. This method accurately approximates TMR10 calculations within clinically relevant ranges, offering an external tool to assess 3D dose distributions for GK treatment plans. Full article

The image quality index for whole-body bone scintigraphy has traditionally relied on the total count (Total-C) with a threshold of ≥1.5 million counts (MC). However, Total-C measurements are susceptible to variability owing to urine retention. This study aimed to develop a skeletal count (Skel-C)-based index, focusing exclusively on bone regions, to improve the accuracy of image analysis in bone scintigraphy. To determine the optimal Skel-C-based threshold, Skel-C thresholds were set at 0.9, 1.0, 1.1, and 1.2 MC, and Total-C thresholds were set at 1.75, 2.0, and 2.25 MC. Patients were then categorized based on whether their values were above or below these thresholds. The group including all cases was defined as the Total-C 1.5 high group. Sensitivity and specificity were calculated for each group, and receiver operating characteristic analyses and statistical evaluations were conducted. The specificity of the bone scintigraphy image analysis program in the Skel-C < 0.9 MC group was significantly lower than that in the Skel-C ≥ 0.9 MC and Total-C 1.5 high groups. The decrease in specificity was evident only with Skel-C and was not identified based on Total-C levels. These findings highlight the importance of achieving Skel-C ≥ 0.9 MC and suggest that Total-C alone is insufficient for reliable image assessment. Full article

Background: We aimed to measure the pacemaker- and defibrillator-induced distortion at 0.35T and 3.0T magnetic fields. Methods: The pacemaker/defibrillator was placed at the top center of a water-filled/MagPhan phantom, followed by a T1 scan at 3T and a TrueFISP scan at 0.35T. The extent of distortion (i.e., the distance from the device to the furthest signal loss/void/rings) in the water-filled phantom was measured in MIM. For geometrical distortion (i.e., dislocation of geometrical structures), the spheres in the MagPhan phantom were contoured and their distortion was calculated based on their manufacturing coordinate positions. Results: The maximum extent of distortion caused by the defibrillator was 18.8 cm at 0.35T and 5.8 cm at 3.0T. Similarly, the maximum extent of distortion caused by the pacemaker was 9.28 cm at 0.35T and 2.8 cm at 3.0T. Geometrical distortion measurements using the MagPhan phantom showed that the maximum distortion caused by the defibrillator was 12.8 mm at 0.35T and 13.2 mm at 3.0T. Likewise, the maximum distortion caused by the pacemaker was 8.7 mm at 0.35T and 6.0 mm at 3.0T. Conclusions: Defibrillators cause larger distortions/signal voids than pacemakers, and require careful consideration when performing MRI-based treatment planning. To minimize distortion, sequences with lower sensitivity to magnetic field inhomogeneity should be used. Full article

Spatially fractionated radiation therapy (SFRT) has a long history of treating bulky and hypoxic tumors. Recent evidence suggests that, compared to conventional uniform dose radiation therapy, SFRT may utilize different mechanisms of tumor cell killing, potentially including bystander and immune-activating effects. The abscopal effect in radiation therapy refers to the control or even elimination of distant untreated tumors following the treatment of a primary tumor with radiation, a process believed to be immune-mediated. Such effects have been shown to be enhanced by immunotherapy, particularly immune checkpoint inhibition. In this manuscript, we explore the potential synergy of spatially fractionated radiation therapy, in the form of kV x-ray minibeam, combined with PD-L1 checkpoint inhibition in a murine mammary carcinoma model at conventional dose-rate. We found that minibeam of peak/valley doses of 50 Gy/3.7 Gy performed statistically equivalent but trending better than that of 100 Gy/7.4 Gy in its abscopal effect and so 50 Gy/3.7 Gy was selected for further studies. Our findings indicate that the abscopal effect is significantly greater in the minibeam plus anti-PD-L1 treated animals compared to those receiving uniform dose radiation therapy plus anti-PD-L1 (p = 0.04948). Immune cell profiling in the minibeam plus anti-PD-L1 group compared to uniform dose reveals a consistent trend towards greater immune cell infiltration in the primary tumor, as well as a higher percentage of CD8+ T cells, both systemically and at the abscopal tumor site. Full article

Ion radiotherapy requires accurate relative biological effectiveness (RBE) calculations to account for the markedly different biological effects of ions compared to photons. Microdosimetric RBE models rely on descriptions of the energy deposition at the microscopic scale, either through radial dose distributions (RDDs) or microdosimetric probability density distributions. While RDD approaches focus on the theoretical description of the energy deposition around the ion track, microdosimetric distributions offer the advantage of being experimentally measurable, which is crucial for quality assurance programs. As the results of microdosimetric RBE models depend on whether RDD or microdosimetric distributions are used, the model parameters are not interchangeable between these approaches. This study presents and validates a method to reproduce the published reference biological and clinical dose calculations at NIRS-QST for only carbon ion radiotherapy by using the modified microdosimetric kinetic model (MKM) alongside microdosimetric distributions instead of the reference RDD approach. To achieve this, Monte Carlo simulations were performed to estimate the variation of the radiation quality within and outside the field of pristine and spread-out Bragg peaks. By appropriately optimizing the modified MKM parameters for microdosimetric distributions assessed within water spheres, we successfully reproduced the results of calculations using the reference NIRS-QST RDD, generally within 2%. Full article

The pursuit of exploring the outer space environment for biological research has been a topic of interest for nearly 60 years. The success of the next phase of space exploration depends on the ability to increase crew safety by identifying ways to mitigate these threats. Using a universal scientific citation indexing tool, we extracted data on literature production in terms of the most prolific key terms, authors, countries, institutions, and journals for two distinct topic sets related to space radiation research published from 1 January 1990 to 31 December 2023. The focus of space radiation research in relation to its effects on human health has fluctuated over time, as reflected in the term maps that were generated for each decade. Our bibliometric analysis provides insight into the trends in the top producers in the space radiation research field over the years, as well as into how the focus of such studies has evolved throughout the decades. Full article

The rising incidence of prostate cancer necessitates innovative treatment approaches, particularly as diseases such as the COVID-19 pandemic can disrupt traditional cancer care. This study aims to evaluate the impact of hypofractionated versus conventionally fractionated radiotherapy on prostate cancer cell lines in vitro. Prostate cancer cell lines (PC-3 and DU-145) were exposed to varying doses of radiation alongside non-cancerous BPH-1 cells. We assessed radiation effects on cell proliferation, viability, colony formation, DNA repair, migration, invasion, and cytotoxicity. The results demonstrated that the prostate cell lines exhibited varying responses, with hypofractionation favourably impacting aggressive PC-3 cells while preserving non-cancerous cells. In contrast, conventional fractionation led to increased invasion and cytotoxicity in both prostate cancerous cell lines. These findings advocate for personalised radiation therapy approaches that enhance treatment efficacy by considering the distinct behaviours of differing prostate cancer subtypes. Full article

Background: Vertebral augmentation (VA) procedures are used to treat painful vertebral fractures caused by malignancies, but there are few data on the radiation exposure for patients and proceduralists during these VA procedures. We retrospectively examined the radiation dose exposure during VA procedures and defined the characteristics of patients who underwent such procedures. Methods: We conducted a retrospective observational cohort study including patients with cancer who experienced axial back pain from compression fractures caused by malignancies. Participants were identified using an electronic medical records database and must have had evidence of stable vertebral compression fractures upon imaging and documentation of a clinical evaluation. We collected data on patient demographics, fluoroscopy time (FT) and dose (FD) during the procedure, the volume of polymethylmethacrylate injected, and reported complications. Results: Overall, 140 patients were included. Their median age was 69, and they were mostly men (n = 79). The most common diagnosis was multiple myeloma (41.4%). Most patients had a single-level compression fracture of the thoracolumbar spine. The mean FT was 233.80 s, with higher FTs for patients with an elevated body mass index and patients younger than 60 years. The average FD was 157.98 mGy, with higher FDs for patients with an elevated BMI and for male patients. Pain relief was not associated with FT or FD. Conclusions: Patients with cancer who underwent VA experienced longer FT and higher FD compared to their non-cancer counterparts in the literature. However, we found multiple confounders for this relationship. Full article

The objective of this study was to evaluate the effectiveness of utilizing radiomic features from radiation planning computed tomography (CT) scans in predicting tumor progression among patients with cervical cancers. A retrospective analysis was conducted on individuals who underwent radiotherapy for cervical cancer between 2015 and 2020, utilizing an institutional database. Radiomic features, encompassing first-order statistical, morphological, Gray-Level Co-Occurrence Matrix (GLCM), Gray-Level Run Length Matrix (GLRLM), and Gray-Level Dependence Matrix (GLDM) features, were extracted from the primary cervical tumor on the CT scans. The study encompassed 112 CT scans from patients with varying stages of cervical cancer ((FIGO Staging of Cervical Cancer 2018): 24% at stage I, 47% at stage II, 21% at stage III, and 10% at stage IV). Of these, 31% (n = 35/112) exhibited tumor progression. Univariate feature analysis identified three morphological features that displayed statistically significant differences (p < 0.05) between patients with and without progression. Combining these features enabled a classification model to be developed with a mean sensitivity, specificity, accuracy, and AUC of 76.1% (CI 1.5%), 70.4% (CI 4.1%), 73.6% (CI 2.1%), and 0.794 (CI 0.029), respectively, employing nested ten-fold cross-validation. This research highlights the potential of CT radiomic models in predicting post-radiotherapy tumor progression, offering a promising approach for tailoring personalized treatment decisions in cervical cancer. Full article

Background: To evaluate p-Cry in 10 years as a feasible and radical approach in patients with small renal masses (<5 cm), we evaluated technical success, side effects, and survival rates. Materials and Methods: We retrospectively evaluated 421 patients with small renal masses (<5 cm) with a median age of 70 years (47–92 C.I.) between June 2014 and July 2024 at our department. We also evaluated side effects, surgical radicality, and therapeutic outcomes of renal functions. Survivals were also evaluated in terms of disease-free, metastasis-free, and cancer-related survival rates. Results: Median follow-up was 90 months (1–120 months C.I.), and median size of the tumor was 3.85 cm (1–4 C.I.). Two cryoprobes were used in median, and two 10-min freeze–thaw cycles were performed. The technical efficacy rate was 100%, whereas only one of 121 lesions required retreatment. No impact on the renal function was registered after p-Cry. Cancer-free survival and metastases-free survival was reached. Conclusions: Compared to surgery, p-Cry is a feasible treatment option in patients with small renal masses, as it does not affect renal function and gives patients good survival rates. Full article

Although radiation therapy is the leading option for effective cancer treatment, a prevalent side effect associated with it is dermatitis. Despite some available literature on this topic, there remain many gaps that need to be addressed. The goal of this study is to determine the incidence of radiation-induced dermatitis (RID) among children receiving proton and photon therapies; a retrospective chart review, at a single institution, was conducted on oncology patients who underwent proton or photon therapy radiation between 2018 and 2023. Significant differences were found between the Radiation Therapy Oncology Group (RTOG) score and the total radiation dose (p = 0.04). The median total dose of radiation received by those with an RTOG score of l was 5040.0 mGy and increased to 7600 mGy for those with a score of 3. A significant association was found between those who received chemotherapy and dermatitis (p = 0.04). No significance was found between the incidence of dermatitis in photon and proton therapy (p = 1.00). The study showed that multiple factors, including total radiation dose and chemotherapy, can affect RID. These relationships can be used to determine the modality, dose, and additional treatment options best suited to treat cancer patients in the pediatric population. Full article

This study investigated the effect of combining radiation with an angiogenesis inhibitor and vascular disrupting agent on tumor response and systemic toxicity. CDF1 mice with 200 mm³ foot implanted C3H mammary carcinomas were treated with TNP-470 (100 mg/kg every second day for 2 weeks; s.c.) and combretastatin A-4 phosphate (CA4P; 1 × 250 mg/kg, i.p.). Radiation (230-kV X-rays) was locally administered to tumors of restrained non-anesthetized mice. Response was tumor growth delay and change in mouse body weight. Radiation induced changes in serum levels of 10 cytokines up to 72-h after irradiation were measured using a Luminex assay. The results showed that TNP-470 (100 mg/kg × 7) or CA4P (250 mg/kg × 1) significantly (Student’s t-test; p < 0.05) inhibited tumor growth; the greatest effect when these two drugs were combined. TNP-470 and CA4P, alone or together, also significantly enhanced tumor response to radiation. No systemic toxicity occurred with drugs administered alone or in combination, but toxicity was observed when TNP-470 was combined with radiation. Serum cytokine levels only showed a significant transient increase in IL-6 1-h after irradiating. In conclusion, combining different acting vascular targeting agents with radiation increased anti-tumor activity. However, this benefit may sometimes be associated with a radiation-induced inflammatory response increasing systemic toxicity. Full article

Radiotherapy remains a cornerstone in cancer treatment, leveraging ionizing radiation to eradicate malignant cells. Its efficacy, however, is frequently challenged by the heterogeneous sensitivity of tumors and surrounding tissues to radiation. Therefore, understanding the molecular mechanisms underlying radiosensitivity is crucial for improving treatment outcomes. Among the myriad of molecular players involved, the tumor suppressor protein p53 stands out as a central regulator with significant implications for radiosensitivity. Known as the “guardian of the genome”, p53 plays a pivotal role in maintaining genomic stability and orchestrating cellular responses such as cell cycle arrest, DNA repair, apoptosis, and senescence in response to various stress signals, including radiation-induced DNA damage. Activation of p53 triggers the transcription of target genes involved in DNA repair pathways, such as p21, MDM2, and GADD45, facilitating the repair of radiation-induced DNA damage or the elimination of irreparably damaged cells. This, in turn, influences the overall radiosensitivity of tissues. Mutations in the TP53 gene, which encodes p53, are among the most frequent genetic alterations in human cancers. Loss or dysfunction of p53 can compromise the cellular response to radiation, leading to increased resistance to therapy and poorer clinical outcomes. Conversely, intact p53 function is associated with enhanced radiosensitivity due to its ability to promote cell cycle arrest and apoptosis in response to radiation-induced DNA damage. In conclusion, elucidating the molecular mechanisms by which p53 influences radiosensitivity is essential for advancing our understanding of the radiation response in cancer cells and developing more effective therapeutic approaches to cancer treatment. This review provides a comprehensive overview of the multifaceted role of p53 in modulating cellular responses to radiation, emphasizing its influence on radiosensitivity. Full article

Vibrational spectroscopic techniques, such as Fourier transform infrared (FTIR) absorption and Raman spectroscopy (RS), offer unique and detailed biochemical fingerprints by detecting specific molecular vibrations within samples. These techniques provide profound insights into the molecular alterations induced by ionising radiation, which are both complex and multifaceted. This paper reviews the application of rapid and label-free vibrational spectroscopic methods for assessing biological radiation responses. These assessments span from early compartmentalised models such as DNA, lipid membranes, and vesicles to comprehensive evaluations in various living biological models, including tissues, cells, and organisms of diverse origins. The review also discusses future perspectives, highlighting how the field is overcoming methodological limitations. RS and FTIR have demonstrated significant potential in detecting radiation-induced biomolecular alternations, which may facilitate the identification of radiation exposure spectral biomarkers/profiles. Full article

X-ray fluoroscopy causes relatively high radiation exposure to physicians, radiation professionals, and patients. Understanding the behavior of scattered radiation is crucial for reducing occupational exposure. We developed a system for estimating radiation exposure during fluoroscopy by monitoring the position of the physician using a depth camera for radiation protection education. The dose distribution of scattered radiation in an X-ray room was simulated using Monte Carlo code. The data were displayed using augmented reality markers, and the dose at each joint point location was estimated using body tracking. Additional functions were created, such as displaying arbitrary two-dimensional cross-sections. The system performance ranged from 9.0 to 11.0 FPS with or without motion and a protective apron. The estimated doses were 0.93 to 1.21 times the measured doses for all joint points, except for the chest and pelvis. The estimated doses for the chest and pelvis were lower than the measured dose, with the minimum values being 0.72 and 0.60 times lower for the chest and pelvis, respectively. The system provides valuable insight into the estimation of radiation dose at joint points based on the physician’s position and movements, the physician’s optimal fluoroscopy location, and warning of dangerous exposure doses. Full article

Nanotechnology has provided considerable advancements in an array of disciplines. Recently, it has been shown that ferumoxytol, a magnetite (Fe₃O₄) nanoparticle, can be oxidized by ionizing radiation. Ferumoxytol nanoparticles have high stability, and thus can be hypothesized that they have dosimetric potential. In this study, it has been observed that xylenol orange, a colorimetric detector of Fe³⁺ used for conventional Fricke dosimetry, was not able to detect radiolytic changes in ferumoxtyol. Electron paramagnetic resonance (EPR) spectroscopy was more readily able to evaluate the oxidation of ferumoxytol. EPR spectroscopy revealed that oxidation of 500 nM ferumoxytol in H₂O was linear up to 20 Gy. This concentration, however, was unable to estimate the delivered dose from a Small Animal Radiation Research Platform system, as a 6 Gy dose was estimated to be 1.37 Gy, which represents a 79.2% underestimation of the dose delivered. Thus, while the high stability of Fe₃O₄ nanoparticles is attractive for use in pre-clinical radiation dosimetry, further radiochemical evaluation may be required before considering them for this application. Full article

Background: Pelvic reirradiation of de novo rectal or anal cancer after prior prostate cancer RT poses a significant risk of urinary and rectal fistula. In this report we describe the use of a rectal spacer to improve dosimetry and reduce this risk. Methods: Patients undergoing anorectal radiotherapy (RT) after prior prostate RT who had a rectal spacer placed prior to RT were identified in a prospective database. Patient, disease, and treatment characteristics were collected for these patients. Survival data were calculated from the end of RT. Radiation was delivered with intensity-modulated radiation therapy (IMRT) or proton beam therapy (PBT) following rectal spacer placement. Results: Rectal spacer placement with hydrogel injected transperineally under transrectal ultrasound guidance was successful in all five patients. MR/CT simulation 1–2 weeks post-spacer placement and IMRT or PBT delivered to a dose of 36–50 Gy in 24–30 fractions once or twice daily were tolerated well by all patients. The V100% of the PTV ranged from 62–100% and mean rectal and bladder dose ranged from 39–46 Gy and 16–40 Gy, respectively. At the last follow-up, three patients were alive and without evidence of disease up to 48 months out from treatment. There were no acute or late grade 3 or higher toxicities observed, but acute grade 2 proctitis was observed in all patients. Conclusions: The use of a rectal spacer placement to improve dosimetry of IMRT and PBT after prior prostate RT is safe and feasible in appropriately selected anorectal cancer patients. Full article