Search Results (252)

The increasing demand for ion beams heavier than protons—particularly carbon and helium ions—for cancer therapy has driven the development of advanced accelerator technologies. Although proton therapy is well established, its physical properties limit its effectiveness against certain tumor types, thereby motivating the use of ions with higher linear energy transfer (LET) and greater biological effectiveness. This study presents the design of an Alvarez-type linear accelerator configuration that combines a Quasi-Alvarez Drift Tube Linac (QA-DTL) and a conventional Alvarez Drift Tube Linac (DTL). The proposed systems are intended for accelerating and injecting carbon or helium ions into a cancer therapy synchrotron, as well as accelerating helium ions for radioisotope production. The optimized QA-DTL and DTL structures provide a versatile and efficient solution for future particle therapy facilities, addressing the growing demand for compact, high-performance, and multifunctional accelerator systems. The proposed linac configurations are designed to operate at 352.2 MHz and consist of three sections. For accelerating low-velocity ions, the first section is a QA-DTL, which is the only section powered during the injection of carbon or helium ions (depending on configuration) into the therapy synchrotron at the energy of 5 MeV/u. The QA-DTL is followed by two DTL cavities forming the second and third sections, which further accelerate helium ions to energies of up to 7.1 MeV/u and 10 MeV/u, respectively. The energy of 7.1 MeV/u is chosen because it represents the production threshold of ²¹¹At, one of the most promising alpha emitters for targeted alpha therapy. Full article

Background/Objectives: Inter-platform variability in beam characteristics and low-dose exposure may arise from differences in linear accelerator head design, multileaf collimator geometry, and dose calculation algorithms. This study aimed to evaluate system-level dosimetric differences between two widely used linear accelerator platforms under clinically commissioned conditions. Methods: A comparative dosimetric analysis was performed between Elekta Synergy and Varian TrueBeam linear accelerators. Beam data were acquired using a SunSCAN™ 3D water phantom, and patient-specific quality assurance was conducted with the Octavius^® 4D system. Treatment plans were generated for left-sided breast, prostate, and head and neck cases using clinically commissioned treatment planning systems. Beam flatness, symmetry, penumbra width, low-dose exposure, conformity, homogeneity, and organ-at-risk dose metrics were evaluated. Results: Platform-dependent differences were observed in penumbra behavior and out-of-field dose, primarily attributable to intrinsic linac head design and collimation characteristics. These differences propagated into clinical plans, with greater variability observed for breast and head and neck cases, while prostate plans showed higher consistency between platforms. Algorithm-dependent trends were noted for conformity and homogeneity indices; however, all plans met institutional clinical acceptance criteria during quality assurance. Stricter gamma evaluation criteria revealed systematic but limited inter-platform deviations. Conclusions: Elekta Synergy and Varian TrueBeam demonstrated clinically acceptable dosimetric performance, with modest platform-dependent differences. While target coverage and overall plan quality were comparable, these variations were primarily observed in peripheral dose regions and may be relevant for platform-specific planning optimization and quality assurance. This supports the importance of comprehensive commissioning and QA procedures in both mixed- and single-platform clinical settings, particularly for highly modulated techniques. Full article

Background/Objectives: The PEER beamline at the ANSTO Australian Synchrotron has been developed to enable VHEE FLASH radiotherapy studies, both dosimetric and biological. Featuring a 100 MeV electron linac, it delivers single or multi-pulse irradiations consisting of 100 ps bunches with a 2 ns spacing, resulting in average dose-rates and instantaneous dose-rates as high as ${10}^8$ Gy/s and ${10}^9$ Gy/s, respectively. Much work has been conducted to realise a stable accelerator facility, complete with the tooling and diagnostics required to undertake such studies. However, to truly confirm its suitability required a successful biological benchmarking. Methods: Three cell lines were irradiated utilising real-time dosimetry to compare linear quadratic cell survival curves with other facilities. Also, mouse cadavers were transported and irradiated, mimicking live animals, to assess the feasibility and logistics of small animal experiments. Results: By comparing the trends of the linear quadratic model, evident in the $\alpha$ and $\beta$ parameters, the PEER cell survival results were shown to be in agreement with VHEE results from the ARES beamline at DESY, Hamburg, Germany. Evident in the survival trends, VHEE produced more cell sparing in all cell lines compared to 2 Gy/s X-rays delivered on the IMBL, another beamline at the Australian Synchrotron. The results of the mouse cadaver irradiations showed that PEER can safely and efficiently irradiate small animals. Conclusions: The PEER beamline is shown to possess suitable capabilities, including real-time dosimetry, repeatable alignment, and linac diagnostics, rendering it suitable for future in vivo VHEE UHDR FLASH radiotherapy investigations. Full article

Boron neutron capture therapy (BNCT) is a binary radiotherapy that is based on nuclear reactions between boron-10 and low-energy neutrons, which enables selective tumor cell killing. Although accelerator-based BNCT systems are increasingly being adopted, each platform requires independent biological validation. Here, we performed an in vitro preclinical evaluation of the linac-based iBNCT001 system employing a beryllium target in combination with the clinically approved boron drug SPM-011 (borofalan (¹⁰B)). Three complementary studies were conducted: (i) a cell-based BNCT efficacy study, (ii) a free-beam radiobiological evaluation, and (iii) a radiation leakage assessment using a human-phantom model. BNCT using iBNCT001 and SPM-011 induced clear boron concentration- and dose-dependent reductions in clonogenic survival across multiple tumor cell lines. Free-beam experiments determined a relative biological effectiveness (RBE) of 2.3 for the hydrogen dose component associated with high energy neutrons. In the phantom study, the maximum radiation leakage dose during head irradiation was 1.31 GyEq in the cervical region. Although this study is limited to in vitro biological assessments, the results provide non-clinical evidence supporting the efficacy, beam quality, and biological safety of iBNCT001 for future clinical BNCT applications. Full article

Background: Stereotactic body radiotherapy (SBRT) for prostate cancer delivers high doses in few fractions but poses challenges in sparing adjacent organs at risk (OARs), particularly the intra-prostate urethra, bladder, rectum and penile bulb. Magnetic resonance-guided radiotherapy (MRgRT) using MR-Linac offers superior soft-tissue visualization and daily adaptive planning, potentially reducing OAR dose while maintaining target coverage. This study aimed to compare dose–volume parameters among MR-Linac (ML), volumetric modulated arc therapy (VMAT), and Tomotherapy (HT) plans for prostate SBRT. Methods: Thirty patients with localized prostate cancer were retrospectively analyzed. For each patient, three plans were generated: ML, VMAT and HT, using identical prescription and planning objectives. Dose–volume histogram (DVH) metrics were evaluated for clinical target volume (CTV), planning target volume (PTV), and OARs. Statistical comparisons were performed using non-parametric Friedman’s Test with post hoc Bonferroni test, with significance set at a p < 0.05. Results: CTV coverage was comparable across all modalities. ML achieved significantly higher PTV Dmin and near-maximum doses compared to VMAT and HT. Notably, ML provided substantial urethral sparing, reducing Dmax and Dmean by approximately 3.3 Gy compared to both VMAT and HT (p < 0.001). Rectal dose metrics were also lower with ML, while bladder and penile bulb doses showed minor increases (<3.5 Gy), considered clinically negligible. Femoral head doses were reduced in ML plans. Conclusions: MR-Linac planning for prostate SBRT offers meaningful dosimetric advantages, particularly in intra-prostate urethra urethral dose reduction, without compromising target coverage. These findings support incorporating MR-guided adaptive workflows into SBRT protocols to enhance OAR protection and potentially reduce treatment-related toxicity. Full article

Anesthesia is the gold standard for immobilization of tumor-bearing mice before radiotherapy which potentially induces stress and distorts disease progression. Irradiation of preclinical cancer models with clinical MV linear accelerator (LINAC) beams can benefit the translation of new strategies in radiation oncology. However, logistical constraints prohibit widespread use of clinical facilities. Currently, there is no detailed protocol on how to safely introduce mice to a clinical environment to be intervened on using hospital equipment. Here, a facile and high-throughput handling method is described that eliminates anesthesia and enables fractionated radiotherapy of multiple mice simultaneously for high-throughput studies. Subcutaneous breast tumor-bearing BALB/c mice were restrained in plastic restraint cones within a containment tray and received four fractions of 4 Gy X-rays from a 6 MV LINAC source over two weeks (two fractions/week). Both short- and long-term follow-up revealed no identifiable health issues or complications associated with the restraint procedure or radiation exposure in terms of body weight loss, skin burns or body condition scores. This method not only benefits animal welfare but also data quality by reducing stress/discomfort levels and confounding effects of anesthetics. It can be applied to a broader range of studies where mice need to be immobilized before intervention. Full article

Background: Peritumoral brain edema (PTBE) is the most frequent complication for intracranial meningiomas following radiotherapy, yet no clinically validated biologically effective dose (BED) threshold capable of reliably predicting PTBE has currently been established. Although conventional radiobiological models typically assume an α/β ratio of 2–4 for benign meningiomas, whether these values accurately reflect the dose–response characteristics underlying radiation-induced PTBE remains unclear. Methods: We analyzed 67 intact meningiomas in the convexity, parasagittal, or falcine regions treated with primary linear accelerator (LINAC)-based radiotherapy. The BED values were recalculated using α/β ratios ranging from 2 to 20, and receiver operating characteristic (ROC) analyses were performed to identify the optimal BED thresholds for predicting PTBE. The most informative α/β ratio was defined as the value yielding the highest Youden’s J statistic. Results: The ROC analyses showed that an assumed α/β ratio of 14 provided the highest discriminative accuracy for predicting PTBE in the overall cohort and markedly superior performance in patients younger than 70 years (area under the curve (AUC) 0.945; Youden’s J = 0.871). The optimal BED threshold for predicting PTBE was approximately 41 Gy (α/β = 14), corresponding to ~18 Gy in a single fraction and ~5.8 Gy per fraction in a five-fraction regimen. Conclusions: The BED values calculated using α/β ratios near 14 provide the most reliable estimate of PTBE risk following primary LINAC-based radiotherapy for convexity, parasagittal, and falcine meningiomas. Maintaining prescription doses below this threshold may help reduce the likelihood of PTBE in this patient population. Full article

This paper presents the experimental validation of a computational kinematic model for a passive Stewart–Gough platform equipped with modified Cardan joints. The introduced joint geometry significantly increases structural stiffness but invalidates the standard spherical joint assumption commonly used in hexapod kinematic formulations. To address this, we develop an efficient numerical optimization-based framework that solves both the direct and inverse kinematics without relying on simplified joint models. Furthermore, to enable autonomous and absolute pose measurement, each cylindrical leg joint of the platform is equipped with a LinACE™ absolute linear encoder. This sensor integration transforms the passive mechanism into an IoT-enabled reconfigurable fixture capable of internally sensing, tracking, and recalling its own configuration. The direct kinematics are computed iteratively using a homogeneous transformation formulation and benchmarked against analytical models derived for ideal spherical joints. Experimental results demonstrate sub-millimeter accuracy in pose estimation, confirming the validity of the proposed kinematic model and highlighting the suitability of the sensor-equipped hexapod for industrial flexible fixturing applications. Full article

Oesophageal cancer remains a significant global health burden with poor survival outcomes despite multimodal treatment. Recent advances in magnetic resonance imaging (MRI) have opened opportunities to improve radiotherapy delivery. This review examines the role of MRI and MR-guided radiotherapy (MRgRT) in oesophageal cancer, focusing on applications in staging, treatment planning, and response assessment, with particular emphasis on magnetic resonance linear accelerator (MR-Linac)-based delivery. Compared to computed tomography (CT), MRI offers superior soft-tissue contrast, enabling more accurate tumour delineation and the potential for reduced treatment margins. Real-time MR imaging during treatment can facilitate motion management, while daily adaptive planning can accommodate anatomical changes throughout the treatment course. Functional MRI sequences, including diffusion-weighted and dynamic contrast-enhanced imaging, offer quantitative data for treatment response monitoring. Early clinical and dosimetric studies demonstrate that MRgRT can significantly reduce radiation dose to critical organs while maintaining target coverage. However, clinical evidence for MRgRT in oesophageal cancer is limited to small early-phase studies, with no phase II/III trials demonstrating improvements in survival, toxicity, or patient-reported outcomes. Long-term clinical benefits and cost-effectiveness remain unproven, highlighting the need for prospective outcome-focused studies to define the role for MRgRT within multimodality treatment pathways. Full article

Over the past two decades, interest in prone-position whole breast irradiation (WBI) as an effective and practical alternative to supine treatment has been growing a lot. Although solid scientific data has provided evidence of substantial dosimetric benefit with decreased toxicity, there is still conflict in the radiotherapy community over whether to adopt prone-position WBI as a valid alternative to supine radiotherapy (RT) in routine clinical practice. A large number of prone trials have been conducted to assess and address concerns related to prone treatment in large and pendulous breasts and in left and right breast cancer (BC), nodal irradiation, and its reproducibility with deep inspiration breath hold (DIBH) delivery with photons or protons. Appropriate atlases have been defined to improve prone nodal irradiation. Additionally, more comfortable customized immobilization couches have been constructed to permit IMRT beams and VMAT arrangements with modern LINACs. Although our search in literature databases shows a growing body of evidence from the past two decades on this issue, prone WBI is still underused. Given the paradox of the advances and benefits of this positioning and the lack of drive in the radiotherapy community towards its clinical implementation, the purpose of this comprehensive review is to evaluate the true advantages of this position in real life and contextualize it in scenarios like large breasts, left-sided breast cancer, and nodal irradiation to encourage its implementation in clinical practice. Full article

EuPRAXIA@SPARC_LAB is an FEL (Free-Electron Laser) user facility currently under construction at INFN-LNF in the framework of the EuPRAXIA collaboration. The electron beam will be accelerated to 1 GeV by an X-band RF linac followed by a plasma wakefield acceleration stage. This high-brightness linac requires diagnostic devices able to measure the beam parameters with high accuracy and resolution. To monitor the beam energy and its spread, magnetic dipoles and quadrupoles will be installed along the linac, in combination with viewing screens and CMOS cameras. Macroparticle beam dynamics simulations have been performed to determine the optimal energy measurement setup in terms of accuracy and resolution. Similar diagnostics evaluations have been carried out for the spectrometer installed at the 100 MeV RF linac of the radioactive beam facility SSRIP (IFIN-HH, Romania), whose commissioning, foreseen for 2026, will be performed by INFN-LNF in collaboration with IFIN-HH. Optics measurements have been performed to characterize the resolution and magnification of the optical system that will be used at SSRIP, and probably also at EuPRAXIA@SPARC_LAB, for beam energy monitoring. Full article

Purpose: To develop a workflow for systemically reviewing the doses received by organs at risk (OARs) in a BgRT treatment session, as a means of monitoring delivery constancy and possibly identifying changes of clinical concern in the patient. Methods: We implemented a workflow consisting of a qualitative review of the reconstructed delivered-dose information provided by the RefleXion system, followed by its quantitative evaluation using in-house software. For the latter we developed a framework for calculating custom OAR dose–volume metrics from the delivered-dose distribution and graphing them. We retrospectively applied our workflow to three select BgRT patient cases to appraise its clinical utility. Results: Our workflow efficiently incorporates existing RefleXion TPS features and in-house software into a process for thoroughly evaluating doses to OARs after BgRT delivery. The spreadsheet we created for graphing the trends of normalized OAR dose–volume metrics readily shows if OAR doses have significantly changed or tolerance limits have been violated, thereby potentially revealing if changes of concern occurred in the targeted region. Our workflow also yields a cumulative delivered-dose record at the end of treatment. Conclusions: We established a post-BgRT dose evaluation workflow which supplements the information provided by RefleXion with calculation and graphing of custom OAR dose–volume metrics. This workflow is now routinely used in our clinic following all BgRT treatments. Future improvements could include increased automation, updating the dose calculation to reflect changes in patient anatomy, incorporation of PET metrics, and consideration of target dose data. Full article

Background: Stereotactic radiotherapy (SRT) is a promising treatment option for patients with multiple brain metastases (BMs). Using one isocenter instead of a separate isocenter for each BM can reduce the treatment time. This work compares the calculated dose in the treatment planning system with the measured dose using film dosimetry of single-isocenter multi-target (SIMT) SRT for multiple BM. Methods: Fifty patients with 4 to 18 BMs (median = 6, in total 356 BMs) were treated with a single-isocenter non-coplanar LINAC-based treatment with six VMAT arcs. Treatment was performed using RayStation and Elekta Versa HD with Agility multileaf collimator, including a 6D robotic couch. Patient-specific QA measurements were performed with an in-house developed phantom using three layers of GafChromic EBT3 film. Film measurements were analyzed in DoseLab using global gamma with 3% and 1 mm distance-to-agreement criteria. Additionally, secondary dose calculations in Mobius3D were performed with similar gamma criteria. Results: The mean total Paddick conformity index and gradient index were 0.7 ± 0.10 and 5.2 ± 1.9, respectively. Monitor units used were 6321 ± 2510, and mean irradiation time was 600 ± 90 s. The mean global gamma passing rate for all measured films was 94.5 ± 4.6% with 3% and 1 mm criteria, while that of the dose calculations in Mobius3D was 98.2 ± 1.2% with the same criteria. A dependence of gamma passing rates of film measurements on the total PTV volume was observed, whereas such dependence was minimal for Mobius3D. Conclusions: The results demonstrate good agreement between the TPS, film measurements, and independent dose calculations, supporting the dosimetric accuracy of single-isocenter multi-target SRT for treating multiple BMs. Full article

Purpose: Brain metastases occur in up to 30% of patients with advanced cancer and remain a major clinical challenge. While WBRT was historically the standard treatment, it provided limited survival benefit and significant neurocognitive toxicity, leading to increasing use of stereotactic radiosurgery (SRS). Recent advances with single-isocenter, multi-target (SIMT) dynamic conformal arc (DCA) techniques on modern linear accelerators have enabled efficient treatment of numerous lesions within a single session, though concerns regarding geometric accuracy persist. This study aimed to evaluate local control outcomes and influencing factors following DCA-SIMT radiosurgery in patients with multiple brain metastases. Methods: We retrospectively analyzed 195 brain metastases treated using single-isocenter, multi-target dynamic conformal arc (DCA-SIMT) stereotactic radiosurgery on a Varian TrueBeam LINAC between August 2018 and September 2020. Treatment planning was performed with Brainlab Elements MultiMets software, version 2.0 and image guidance with ExacTrac. Local control was assessed on MRI according to BM-RANO criteria, while radiation-induced contrast enhancements (RICE) were identified using multiparametric MRI. The median follow-up duration was 12 months. Statistical analyses included chi-square and ROC analyses, with p < 0.05 considered statistically significant. Results: A total of 195 brain metastases in 37 patients were analyzed. Local control at 6 months was achieved in 93% of lesions, with complete or partial response in 82%. Distance-to-isocenter (DTI), gradient index (GI), and target volume (GTV/PTV) were not associated with local control. In contrast, conformity index (CI) < 1.42 predicted better treatment response (AUC = 0.698, p = 0.0006). Margin expansion ≥ 0.5 mm was associated with improved local control (p = 0.049), while higher margins did not further improve outcomes. Prescription dose showed no significant impact. The addition of immunotherapy or targeted therapy within 4 months post-SRS significantly increased the likelihood of radiographic response (OR = 2.55, p = 0.030), with the strongest association observed in lung adenocarcinoma patients (p < 0.001). Conclusions: DCA-SIMT stereotactic radiosurgery achieves high local control in patients with multiple brain metastases. Conformity index, minimal margin expansion, and systemic therapy influenced outcomes, whereas distance-to-isocenter and dose did not. Further validation is needed to optimize margins in high-DTI scenarios. Full article

Background/Objectives: The aim of this study was to establish the relationship between target size and the required diagnostic PET maximum standard uptake value (SUVmax) thresholds needed for successful Biology-guided Radiotherapy (BgRT) delivery on RefleXion X1 PET-linac. The current clinical eligibility recommendation is an SUVmax ≥ 6 at simulation, but the RefleXion system subsequently evaluates Activity Concentration (AC), which must exceed 5 kBq/mL for successful BgRT planning. Methods: A custom 3D-printed phantom containing six spherical targets (8 to 20 mm diameter) was used with varying target-to-background ratios (5:1 to 20:1) of 18F-FDG to systematically achieve a range of SUVmax values for each target size. Images were acquired on Siemens Biograph mCT for SUVmax quantification and RefleXion X1 for AC measurements. Twenty-four BgRT plans were evaluated, and delivery accuracy was validated using ArcCHECK. Additionally, retrospective data from 18 patients across four institutions were analyzed to validate the phantom-derived findings. Results: The PET-linac successfully planned treatments for 13/24 experiments, all achieving an AC > 5 kBq/mL. SUVmax requirements varied by target size: 16–20 mm targets required an SUVmax > 6, consistent with current recommendations, while smaller targets required higher thresholds (e.g., 13 mm: SUVmax > 10, and 11 mm: SUVmax > 15). 8 and 9 mm targets failed to meet AC requirements even at SUVmax 14. Successful deliveries maintained acceptable accuracy, with gamma passing rates of 92.4% ± 5.0% (3%/2 mm) and 97.6% ± 1.9% (3%/3 mm). Analysis revealed that Volume (cc) × SUVmax > 11 consistently predicted successful BgRT planning across all target sizes. This threshold was validated using multi-institutional PET-CT patient data (mean: 11.36, 95% CI: 9.1–12.9), correctly predicting treatment eligibility in 15 of 18 cases. Conclusions: Target size significantly influences BgRT eligibility. We derived a new criterion, Volume(cc) × SUVmax > 11 (95% CI: 9.1–12). Full article