Bowel Bag Dosimetric Parameters for Ultrahypofractionated Pelvic Elective Nodal Irradiation in Prostate Cancer.

Predictive role of Bladder wall dosimetry in conventional prostate Radiotherapy: Integrating AI and statistical Modelling.

International Radiosurgery Oncology Consortium of the Kidney (IROCK) Contouring Guidelines for Renal Cell Carcinoma Treated With Stereotactic Ablative Radiation Therapy.

We present a theoretical evaluation of radiation dose constraints for extreme ultraviolet (EUV) and soft X-ray microscopy. Our work particularly addresses the long-standing concern regarding strong absorption of EUV radiation in biological specimens. Using an established dose-resolution model, we compare hydrated and dehydrated cellular states and quantify the fluence required for nanoscale imaging. Our analysis identifies a protein window spanning photon energies from ∼70 eV up to the carbon K-edge (284 eV). Towards the upper end of this range, at photon energies above 100 eV, EUV microscopy could in principle achieve sub-10 nm half-pitch resolution in dehydrated samples at doses well below the Henderson limit. In this situation, the radiation dose required for EUV imaging is predicted to be substantially lower than what is required for comparable resolution in water window soft X-ray microscopy. Furthermore, EUV photons with sufficiently high energy exhibit penetration depths of µm-level in dehydrated biomatter, enabling exceptional amplitude and phase contrast through thin cellular regions and small cells. These findings provide quantitative guidelines for photon energy selection and support the EUV protein window as a dose-favorable and physically viable modality for high-resolution, label-free, material-specific imaging of dehydrated biological matter.

To evaluate the palliative efficacy of re-irradiation stereotactic body radiotherapy (SBRT) for painful spinal metastases. In this single-centre, single-arm, phase II study, patients with painful spinal metastases (pain score ≥2 on a 0-10 scale) from solid tumours were enrolled. Eligibility criteria included absence of epidural spinal cord compression, and irradiation history (excluding SBRT) with an interval of ≥3months. The prescribed dose was 24Gy in two fractions; the maximum spinal cord dose constraint was 12.2Gy. The primary endpoint was the pain response rate at 6months in evaluable patients. Among 35 spinal lesions in 34 patients registered between July 2019 and June 2024, 11 (31%) lesions were severely painful (score, 8-10), 16 (46%) were radioresistant, and 14 (40%) involved ≥3 consecutive vertebrae. The median prior equivalent dose in 2-Gy fractions (α/β=10) was 33 (range, 23-70) Gy, and median interval between irradiations was 12 (range, 3-114) months. The median follow-up period was 9 (range, 2-51) months. Among evaluable patients, pain response was 84% at 3months and 83% at 6months, whereas complete response (CR) was 48% and 56%, respectively. In the intention-to-treat analysis, pain response was 60% at 3months and 43% at 6months, whereas CR was 34% and 29%, respectively. The 6-month local failure rate was 7%. Two (6%) patients experienced grade 3 toxicities. Re-irradiation SBRT achieved substantial pain relief with acceptable toxicity, warranting larger randomized trials against conventional radiotherapy.

Modern radiation therapy (RT) technologies allow for improved sparing of normal tissues, decreasing the risk of both acute and long-term toxicities. Existing RT dose constraints for prospective trials within the National Clinical Trials Network (NCTN) were formulated in the context of solid malignancies. As patients with hematologic malignancies are often treated with lower RT doses and are usually younger with more favorable prognoses, customized dose constraints are needed. The NRG Oncology Hematologic Malignancies Working Group (NRG HEME) commissioned a review of existing organ at risk (OAR) constraints from published primary literature, the NRG Center for Innovation in Radiation Oncology (CIRO), and national guidelines. Customized constraints were developed by iterative review by NRG HEME. Final recommendations were approved by radiation oncology representatives from all the lymphoma NCTN groups (NRG Oncology, COG, Alliance, ECOG-ACRIN, SWOG, CCTG). For 49 OARs, a strict recommended constraint was determined, of which 20 were not present in CIRO. Of the remaining 29 constraints, 20 were lower, 2 were the same, and 5 used different metrics; 2 were higher than at least one CIRO trial constraint. Acceptable variations were determined and unacceptable variations were added for select critical OARs for plan scoring. While doses to OARs without explicit unacceptable variations should not exceed acceptable variations, violations should not be considered for plan quality assessment on trials. This consensus list of standard OAR constraints should be incorporated for all future NCTN trials in hematologic malignancies. Strict dose constraints will minimize long-term toxicities in this patient population.

Proton-specific dose and radiation quality constraints to reduce acute oral mucositis in head and neck cancer patients.

Effect of formulation composition on stability and aerosol performance of respirable high load monoclonal antibody powders.

Precision Radiotherapy for Hepatocellular Carcinoma: Exploring the Clinical Utility of Functional Liver Avoidance Planning (FLAP).

This study aimed to evaluate the effectiveness of online adaptive treatment (ADT) planning for stereotactic body radiotherapy (SBRT) boost on a 1.5-T MR-Linac in cervical cancer patients ineligible for brachytherapy, compared with the conventional position-alignment (PA) assumed dose distributions. This retrospective analysis included 15 treatment plans from five patients, each receiving 21.0Gy in three fractions. Daily magnetic resonance imaging (MRIs) were used to compare target and organ-at-risk (OAR) doses between ADT and PA dose distributions. The planning target volume (PTV) was defined as the high-risk clinical target volume (HR-CTV) plus a 3mm margin. OARs included the bladder, bowel bag, and planning organ-at-risk volume (PRV) for rectum and sigmoid. Reference plans prioritized OAR constraints while maximizing target coverage; the intended PTV D90% range was 18.9-21.6Gy. PA doses were reconstructed by dose warping based on alignment of the anterior rectal wall between daily and pretreatment MRIs, whereas ADT plans were reoptimized on the daily MRIs. HR-CTV decreased by 1.6%-41.5% between the planning MRI and the first treatment fraction. ADT plans improved PTV D90%, achieved better target coverage and metall OAR constraints, whereas PA plans showed dose constraint exceedance across the three fractions, with mean excess doses of 6.89 ± 4.39Gy to PRV-sigmoid and 5.76 ± 3.33Gy to PRV-rectum. In conclusion, 1.5-T MR-Linac based SBRT boost with daily online adaptation enhanced tumor coverage and reduced OAR doses, supporting MR-guided online adaptive radiotherapy as a promising option for patients ineligible for brachytherapy.

Dosimetric Results for Organs at Risk from Radiotherapy Dose De-Escalation to the Subclinical Region in HPV-Mediated Oropharyngeal Cancer: A Propensity Score-Matched Analysis.

Magnetic resonance image (MRI)-guided radiotherapy can optimize the therapeutic outcomes of brain glioma patients, as it adjusts to tumor changes in the course of radiation treatment. This study evaluates the dynamic changes of tumors and the feasibility of implementing MRI-guided online adaptive radiotherapy (MRIgOART) for the treatment of brain glioma. This observational prospective cohort study involved patients with brain glioma treated using 1.5 T MR-Linac from 2021 to 2023. MRIgOART can correct treatment errors and evaluate treatment response through adapt-to-position (ATP) and adapt-to-shape (ATS) strategies. Dice similarity coefficient (DSC), absolute/relative volume (Vrel), and Hausdorff distance (HD) metrics were used to quantify tumor changes. The covariables subjected to evaluation included: surgical resection extent, 1p/19q status, telomerase reverse transcriptase (TERT) mutation status, O6-methylguanine-DNA-methyltransferase (MGMT) methylation status, and isocitrate dehydrogenase (IDH) mutation status. ART and non-ART treatment plans were comparatively analyzed based on target coverage and dose constraints for normal brain tissue. The pattern of failure, as the primary endpoint, was evaluated in this study. Secondary endpoints of the study consisted of overall survival (OS) and progression-free survival (PFS), assessed according to treatment schedules. The cohort comprised 57 patients. The patients with an interval longer than 10 days from simulation to the Fx1 exhibited more significant tumor changes (p < 0.001). The tumor volume showed a gradual reduction during the treatment, whereas the alterations in its location and shape became increasingly evident over time. Multivariate analyses identified associations between prognosis and HD, in addition to a relationship between the extent of surgical resection and DSC. ATS was utilized in 52.6% of patients at least once during treatment, with a higher frequency in TERT wild-type patients (p = 0.013). MRIgOART treatment plans achieved superior target conformality, adequate coverage, and effective sparing of OARs. High-grade glioma (HGG) patients exhibited median PFS of 13 months (95% CI, 10.2-15.8 months) and OS of 28 months (95% CI, 23.3-32.7 months). Failure analysis revealed 58.9% in-field, 17.6% marginal, and 23.5% distant recurrences, with IDH mutation status associated with failure patterns. Preliminary findings in patients with HGG suggest a lower incidence of recurrences within the radiation field and indicate promising outcomes associated with MRIgOART. However, these observations require further validation through comparative studies.

Background. Prostate cancer is characterized by a low α/β ratio, supporting the use of hypofractionated treatment regimens, particularly high-dose-rate (HDR) brachytherapy. However, the application of CT guidance in this setting remains limited and technically challenging. Purpose. – the aim of this study is to present a case of non-standard high-dose- rate (HDR) prostate brachytherapy in a patient with absence of the rectum. Materials and Methods. We present a clinical case of a patient born in 1975 with metachronous malignancies: prostate cancer cT2N0M0 (stage II, Gleason score 4+5=9) on the background of previously treated stage III colorectal cancer following multi- modal therapy. Multiparametric MRI demonstrated multifocal PI-RADS 4 lesions. Interstitial high-dose-rate (HDR) brachytherapy was delivered as a single-fraction treatment (19 Gy) to the entire prostate using 14 applicators under CT guidance. Results. Adequate PTV coverage was achieved (D90 = 19.7 Gy, D95 = 17.3 Gy) with compliance to dose constraints for organs at risk (urethra D2cc = 18 Gy, &lt;95%). The calculated equivalent dose in 2 Gy fractions (EQD2) for the tumor was 111.3 Gy, reflecting the high biological effectiveness of the treatment. Conclusions. CT-guided high-dose-rate (HDR) brachytherapy represents a promising treatment approach for prostate cancer in cases where ultrasound guidance is not feasible, enabling high-dose delivery to the tumor while maintaining an acceptable toxicity profile.

Objective Addressing the issue of induced radioactivity in carbon ion therapy system operation, to systematically evaluate the impact of beam parameters on the distribution of induced radiation field in carbon ion therapy room and develop radiation protection strategies. Methods A geometric model integrating a multi-leaf collimator (MLC), compensator, patient phantom, and concrete shielding structure was developed using the FLUKA Monte Carlo simulation code. Systematic simulations were conducted to analyze residual dose rate decay kinetics and radionuclide activation profiles at critical components under 400 MeV/u carbon ion irradiation with beam intensities and irradiation durations. Results The induced radioactivity generated by components exhibited a linear response to beam intensity. The MLC surface exhibited a residual dose rate of 15.8 μSv/h at 1 min post-irradiation (1×10 8 pps, 15-minute irradiation), requiring 45 min cooling for the safety threshold. The activation nuclides produced in patient phantoms were dominated by short-lived nuclides, with radiation dose decreased to acceptable level within 10 min post-irradiation. Occupational exposure assessments demonstrated annual effective doses of about 174 μSv (air immersion) and 0.31 μSv (inhalation). Conclusion The induced radioactivity dose produced by the carbon ion radiotherapy system is mainly generated by MLC and patient phantoms. Personnel should avoid direct contact within 10 minutes post-irradiation. Occupational exposure levels of the air activation remain compliant with occupational dose constraints.

TG-43 formalism assumes homogeneous water media, potentially overlooking anatomical heterogeneities that affect dose accuracy. AcurosBV, a model-based dose calculation algorithm, accounts for tissue and material heterogeneities. This study evaluates their dosimetric differences in high-dose-rate (HDR) brachytherapy using Harrison-Anderson-Mick (H.A.M.) applicators. To compare dose-volume histogram (DVH) metrics calculated using TG-43 formalism and AcurosBV in patients treated with HDR brachytherapy using H.A.M. applicators for superficial lesions in the head and neck regions. Twenty patients (17 nasal, 3 non-nasal) received HDR brachytherapy with H.A.M. applicators to a total dose of 40Gy in eight fractions. Original plans calculated with TG-43 formalism were retrospectively re-calculated using AcurosBV (Eclipse v16.1), incorporating Hounsfield unit-based heterogeneity corrections with dose-to-medium reporting. Planning target volumes (PTVs) were contoured by radiation oncologists; organs at risk (OARs) including brain, eyes, lens, optical nerve and skin were auto-segmented using AutoContour (Radformation Inc., NY). DVH metrics (mean dose, D90%, V100%, V150%, V200%, D0.1cc, D0.2cc, D1cc and D2cc) were compared. The isodose distributions from both algorithms were also evaluated slice by slice. Statistical significance was assessed using a paired Student's t-test (p<0.05). AcurosBV consistently reported lower DVH value in PTV than TG-43. The average PTV mean dose was 48.65±1.22Gy (AcurosBV) versus 50.78±1.40Gy (TG-43), with significant difference in V100 (-6.43±0.95%, p<0.003). OAR dose differences were modest (∼1.5%) except for the skin, which showed larger reductions (∼4-5% in D0.1cc-D2cc, p<10- 8). Visual inspection revealed less conformal isodose distributions in AcurosBV plans due to air cavities and tissue inhomogeneities. AcurosBV yielded lower and anatomically informed dose estimates compared with TG-43 in HDR brachytherapy using H.A.M. applicators. These results support clinical adoption of model-based algorithms but warrant caution, as dosimetric differences and prior TG-43 experience may affect existing dose constraints and clinical outcomes.

An international survey of radiological protection in medical research programmes involving human volunteers.

Objective.Microcalcification (µCalc) detection plays an important role in breast cancer screening. Electronic noise in energy-integrating detectors (EIDs) is the major challenge for this task in current breast cone-beam CT (bCBCT) due to the tight dose constraint for breast imaging. bCBCT with a photon counting detector (PCD) can potentially offer a higher spatial resolution and lower noise. This study performed a direct comparison of bCBCTs with the two detector types via GPU-based Monte Carlo (MC) simulation.Approach.We employed Virtual Clinical Trial for Regulatory Evaluation toolkit to generate a realistic breast phantom with a 0.25mm3voxel size, 80% fat fraction and 14 cm diameter. We considered a bCBCT system with a 60 kV x-ray source filtered with 0.3 mm Cu and detector response functions for PCD and EID. A total of 360 projections were simulated with a total number of3.15×1012photons, corresponding to ∼4 mGy mean glandular dose, comparable to a two-view mammography. We modified our GPU-based MC simulation code to incorporate analytical descriptions ofµCalcs of spherical shapes with diameters ranging from 0.1 to 0.4 mm, in 0.1 mm increments, into the voxelized phantom. A nichrome wire with 0.07 mm diameter was simulated to calculate the modulation transfer functions (MTFs). bCBCT images were reconstructed with the Feldkamp-Davis-Kress algorithm, and image quality andµCalc detection performance were evaluated.Main results.EID-bCBCT had more profound image noise due to electronic noise. The image intensity standard deviations estimated within a region of interest were 0.055 cm-1for EID-bCBCT and 0.038 cm-1for PCD-bCBCT, respectively.µCalcs and breast anatomy such as ligaments were more visible in the PCD-bCBCT images. The 10% MTF cutoffs were 5.5 and 9.5 lp mm-1for EID-bCBCT and PCD-bCBCT, respectively. Contrast-to-noise ratio ranged in 1.20-9.13 for EID-bCBCT and 3.07-14.74 for PCD-bCBCT, depending onµCalc sizes.Significance.We compared EID- and PCD-based bCBCT forµCalc detection using GPU-based MC simulations in a clinically realistic setting. Our results demonstrate a potential advantage of PCD-bCBCT for this detection task.

To evaluate the effectiveness of different optimization parameters on radiotherapy plan quality for seventeen head and neck cancer patients. Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost (VMAT-SIB) plans, involving up to three tumors, were generated. For each participant, a reference plan (Plan_Ref) was created using dual-arc with 180 control points, 20° gantry-angle increment and 1 cm minimum segment width. Modified plans were developed with dose constraints and optimization settings constant by changing to single-arc, 150 and 200 control points, 0.5 cm minimum segment width, and 30° and 40° gantry-angle increments. These plans were referred to as Plan_Arc1, Plan_CP150, Plan_CP200, Plan_SW0.5, Plan_Inc30, and Plan_Inc40, respectively. D95% of planning target volumes (PTVs), homogeneity index (HI), monitor units (MUs), maximum dose (Dmax) of spinal cord, mandible, and brainstem were recorded. Statistical and Bland-Altman analysis was performed comparing the modified plans to Plan_Ref. Average D95% values for PTV1, PTV2, and PTV3 ranged from 93.13 to 98.82%. Plan_SW0.5 provided superior target coverage and homogeneity with higher MUs than Plan_Ref. Plan_Arc1 significantly reduced PTV coverage and dose homogeneity, while increasing MUs compared with Plan_Ref (p < 0.05). The average Dmax as derived from all planning approaches was up to 43.86 Gy, 65.86 Gy, and 48.85 Gy for spinal cord, mandible and brainstem, respectively. For spinal cord, Plan_Ref led to significantly lower doses compared to Plan_Arc1 and Plan_Inc30, while the brainstem recorded statistically higher Dmax doses than Plan_Arc1. Significantly higher Dmax was observed for the mandible using Plan_SW0.5 (p < 0.05). However, for Dmax, the comparison plans showed good agreement with Plan_Ref based on Bland-Altman analysis. The VMAT plan quality is strongly affected by the minimum segment width whereas no differences were observed with the modification of the number of control points.

ABSTRACT Introduction: Late-onset impaired swallowing is a frequent clinically significant outcome of irradiation for head and neck malignancies. Accumulating evidence indicates that radiation exposure of the pharyngeal constrictor musculature contributes substantially to post-treatment dysphagia. Objective: This study evaluated the incidence of late dysphagia and explored associations between dosimetric parameters of pharyngeal constrictor muscles and impaired swallowing in patients receiving definitive irradiation. MATERIAL AND METHODS: In this cohort study, 50 patients were included with oropharyngeal, hypopharyngeal, or laryngeal carcinoma (any T, any N, M0) treated between December 2020 and April 2022. All patients underwent CT-based planning and were treated with intensity-modulated radiotherapy (IMRT) with or without concurrent chemotherapy. Pharyngeal constrictors were delineated as organs at risk. Swallowing function was assessed using the EORTC QLQ-H&amp;N35 questionnaire and graded according to RTOG criteria. Dosimetric parameters correleation was done with impaired swallowing grades at 6 months following irradiation completion. Results: 23 patients were evaluable at 6 months. Grade I, II, and III dysphagia were observed in 60.87%, 30.43%, and 8.7% of patients, respectively. Increasing dysphagia severity demonstrated a consistent trend with higher maximum dose and high-dose volume exposure (V65) to the superior and middle pharyngeal constrictor muscles. Mean and Dmax of SPCM increased from 68.46 Gy in Grade I to 69.21 Gy in Grade III dysphagia, while V65 increased from 28.58% to 63.38%. Similar dose–volume escalation was noted for the MPCM. These differences did not reach statistical significance. Conclusion: Higher dose and volume exposure of the superior and middle pharyngeal constrictor muscles shows direct association with worsening of impaired swallowing. IMRT planning strategies that prioritize sparing of these structures may reduce long-term swallowing morbidity. Larger prospective studies with extended follow-up are needed to define robust dose constraints.

This study evaluated the usefulness of non-coplanar volumetric modulated arc therapy (VMAT) using a novel O-ring-type linear accelerator, OXRAY, in patients with prostate cancer (PCa). The focus was on those with the planning target volume (PTV) adjacent to the small or large intestine. We enrolled 10 consecutive PCa patients with the PTV less than 10 mm from the small or large intestine. These patients underwent conventional coplanar VMAT (Conv-VMAT) using Halcyon, another O-ring-type linear accelerator, at our institute between July 2023 and July 2024. To evaluate the utility of OXRAY, we developed two simulation plans: biaxially rotational dynamic radiation therapy (BROAD-RT) and swing-fixed non-coplanar VMAT (SF-VMAT). A total dose of 63 Gy in 21 fractions was prescribed for all plans. Dosimetric parameters of the PTV and organs at risk were compared among the three plans using paired t-tests. No significant differences in the dose received to 95% of the volume (D95) of the PTV were observed among the three plans. However, the D95 of the PTV-base, defined as the three cranial slices of the PTV, significantly improved in BROAD-RT compared to Conv-VMAT, adhering to dose constraints of the small or large intestine. On the other hand, the improvement in SF-VMAT was insignificant. BROAD-RT and SF-VMAT significantly improved rectal dose indices compared to Conv-VMAT. For PCa patients with the PTV close to the small or large intestine, non-coplanar VMAT using OXRAY may improve the PTV-base coverage and decrease rectal dose compared to conventional VMAT plans, while adhering to dose constraints of the small or large intestines.