We evaluated different breakpoint (BP) strategies and the impact of scan path optimization on dose accuracy, beam interruptions, and delivery efficiency in proton dose-driven continuous scanning (DDCS). Our goal is to provide insights for the effective clinical implementation of DDCS. Proton PBS plans were retrospectively simulated for DDCS with beam current optimized for the shortest beam delivery time (BDT). Five BP strategies were evaluated: three SD-based (SD1, SD1.5, SD2) using spot distance thresholds, and two SR-based (SR1, SR0) using the ratio of MU delivered at the planned spot to that delivered in transit. Simulations included three scan paths (default, length-optimized, time-optimized). Comparative analysis included BP fraction (beam interruptions), dose accuracy, and BDT. SD-based approaches achieved excellent dosimetric accuracy, with 2%/2 mm Gamma pass rates >98% and CTV DVH RMSE <1% across all BP thresholds and scan paths.SD2 with length-optimized path minimized BPs (median 1.1%, range 0-6.7%) while maintaining high dose accuracy, making it the preferred choice when minimizing dose deviations and BPs is the priority. SR-based approaches had shorter BDTs, maintaining >95% Gamma pass rates and <2% CTV DVH RMSE with optimized scan path. SR0 with time-optimized path is suitable when BDT is critical. Scan path optimization reduced BPs for SD-based methods and improved dose accuracy for SR-based methods. If only the default serpentine path is available, caution is required for lung treatments to ensure clinically acceptable dose with SR-based methods. Dose accuracy can be maintained without reducing the beam current optimized for BDT in DDCS. SD-and SR-based methods show complementary strengths: SD2 with a lengthoptimized path minimizes dose deviations and breakpoints, whereas SR0 with time-optimized path offers shorter BDT and maintaining acceptable dose deviations. These findings provide guidance for implementing proton DDCS to balance dose accuracy, beam interruptions, and delivery efficiency according to clinical needs.

Radiotherapy remains a critical pillar of cancer treatment worldwide. This study evaluates the in vitro efficacy of high-energy ionizing radiation, specifically 6 MV electrons and 12 MV X-rays, generated by a Varian Clinac iX linear accelerator (linac), on human HepG2 (liver) and AGS (gastric) cell lines. Cell samples (1 ml) were irradiated with doses ranging from 0.5 Gy to 4 Gy. Cell viability was assessed using the WST assay 4-5 hours post-irradiation. The measured survival rates were critically compared with those predicted using the established linear-quadratic (LQ) model. The results revealed significant and consistent discrepancies between the experimental measurements and the theoretical predictions for both cell lines. For HepG2 cells, the measured survival rate at 4 Gy was higher than the predicted rate. Interestingly, AGS cells irradiated with 12 MV X-rays exhibited minimal cytotoxicity, with a viability rate of 99.0% at 3 Gy versus a predicted rate of 73.6%. These findings suggest a discrepancy between theoretical predictions and the short-term biological responses observed under the shallow in vitro irradiation conditions employed in this study. While the present study was not designed to isolate the underlying mechanisms, the results imply that factors inherent to high-energy beam delivery in thin in vitro geometries, together with the early (four to five hour) post-irradiation assessment window, may have contributed to the limited cytotoxicity observed in both cell lines. Further studies employing extended observation periods or complementary assays would be valuable in clarifying the temporal progression of MV-beam-induced cellular effects. Keywords: Varian Clinac iX, high-energy radiation, HepG2, AGS, cell viability, WST assay, Monitor Unit (MU).

This article presents a comprehensive overview of the current and emerging roles of cryogenics and superconductivity in medical diagnostics, imaging, and therapy. Beginning with the historical foundations of both fields and their technological maturation, this review emphasizes how cryogenic engineering and superconducting materials have become indispensable to modern medical systems. Cryogenic technologies are highlighted in applications such as cryosurgery, cryotherapy, cryostimulation, and cryopreservation, all of which rely on controlled exposure to extremely low temperatures for therapeutic or biological preservation purposes. This article outlines the operating principles of cryomedical devices, the refrigerants and cooling methods used, and the technological barriers. This paper reviews the latest applications of superconductivity phenomena in medicine and identifies those that could be used in the future. These include cryogenic therapy, radiotherapy (cyclotrons, particle accelerators, synchrotron radiation generation, isotope production, and proton and ion beam delivery), magnetic resonance imaging (MRI), nuclear magnetic resonance spectroscopy (NMR), positron emission tomography (PET), and ultra-sensitive magnetic signal transducers based on SQUIDs for detecting ultra-low bio-signals emitted by human body organs. CT, MRI/NMR, and PET features are compared using the operation principle, specific applications, safety, contraindications for patients, examination time, and additional valued peculiarities. This article outlines the prospects for the development of superconducting and cryogenic materials and technologies in medical applications. Advances in diagnostic imaging are reviewed, with particular attention on the progression from conventional MRI scanners to ultra-high-field (UHF) systems exceeding 7–10.5 T, culminating in the 11.7 T Iseult whole-body MRI magnet. Another important application area described in this article includes biofunctionalized magnetic nanoparticles and superconducting quantum interference devices (SQUIDs), which enable the ultrasensitive detection of biomagnetic fields and targeted cancer diagnostics. Finally, this article identifies future directions of development in superconducting and cryogenic technologies for medicine.

Objectives: Ultra-high dose-rate FLASH radiotherapy has demonstrated strong potential in reducing normal tissue toxicity while maintaining effective tumor control. However, its underlying radiobiological mechanisms remain unclear, highlighting the need for novel approaches to probe the effects of radiation during and immediately after delivery. This study presents the first exploration of 3D PET imaging of positron-emitting nuclei (PENs) generated by a FLASH proton beam. Methods: A home-built 12-panel preclinical small-animal PET system was employed for recording coincidence events. A 142.4 MeV FLASH proton beam with a 100 ms delivery time was directed into a solid water phantom. PET coincidence signals were recorded during the first 1 s and up to 11 min. The system's capability for 3D localization was also assessed, and Monte Carlo simulations were performed for validation. Results: The PET system successfully recorded coincidence data within the first second, including the 100 ms beam delivery interval. Detector dead-time effects under the high beam flux were observed, leading to underestimated event counts. Following irradiation, the measured activity and decay behavior were consistent with simulations. The PET system accurately reconstructed the spatial distribution of PEN activities, with discrepancies in measured versus calculated line profiles ranging from 3.35-6.85%. Reconstructed PET images enabled reliable 3D localization with sub-millimeter accuracy in both lateral and depth dimensions. Conclusions: Our findings demonstrate that a multi-detector PET system is a promising tool for investigating the radiation effects of FLASH beams.

This study aimed to compare the quality of radiotherapy treatment plans for stomach cancer on Halcyon™ and VitalBeam® linacs. Treatment plans were created for 20 stomach cancer patients clinically treated with Halcyon™. The same plans were retrospectively generated for VitalBeam® under identical planning conditions. Halcyon™ plans were generated with 6 MV FFF (flattening filter-free) beams (800 monitor units (MU)/min), while VitalBeam® plans used 6 MV flattened beams (600 MU/min), reflecting routinely used configurations and enabling evaluation of FFF versus flattened beam delivery. Conformity index (CI), gradient index (GI), and homogeneity index (HI) for the planned target volume (PTV), and dose metrics for organs at risk (OARs) were assessed. Statistical comparisons were performed using paired tests, where significance was set at p < 0.05. VitalBeam® achieved a higher CI for the PTV (0.70 ± 0.17) compared to Halcyon™ (0.64 ± 0.14, p = 0.048). GI values were slightly higher with VitalBeam® (3.41 ± 0.39 vs. 3.26 ± 0.51) but not significantly (p = 0.058). HI values were similar (0.11 ± 0.04 vs. 0.10 ± 0.04, p = 0.308). For OARs, most dose metrics were comparable, while bowel V15 was significantly higher with Halcyon™ (374.6 ± 215.8cc vs. 346.6 ± 205.9 cc, p = 0.007). It is concluded that Halcyon™ and VitalBeam® provide comparable VMAT quality for stomach cancer. VitalBeam® achieved better target conformity and bowel sparing, while Halcyon™ maintained overall efficiency. These differences reflect the multi-leaf collimator (MLC) design and beam setup, highlighting clinical equivalence and tailoring machine choice to needs.

BackgroundPreclinical studies demonstrate the benefits of ultra‐high dose‐rate (FLASH) radiation, reducing normal tissue toxicity while maintaining tumoricidal effects. Proton FLASH (pFLASH) studies typically use transmission beams, missing the normal tissue‐sparing advantage of the spread‐out Bragg peak (SOBP).PurposeThis study aims to propose and implement a series of modifications to enable a clinical Mevion S250i gantry‐mounted synchrocyclotron to deliver pFLASH within the SOBP of the proton beam.MethodsA clinical synchrocyclotron was modified to enable FLASH proton beam delivery using the Mevion FLASH accessory kit, a commercially available tool that allows for the delivery of a single spot SOBP at FLASH dose rates. To ensure accurate beam monitoring, a Faraday cup was utilized to measure the integral charge per delivery at different dose rates and calibrate the FLASH transmission ion chamber (FLASHTic), which is integrated in the FLASH accessory mount attached to the nozzle of the gantry. The FLASHTic was specifically designed to prevent saturation at the dose rates associated with FLASH. To generate the desired single spot SOBP, boron carbide absorbers, a range modulating hole filter, and an 11‐mm‐diameter circle brass aperture were employed on the FLASH nozzle mount.ResultsThe results indicate that the FLASHTic measurements demonstrated a strong correlation with the Faraday cup post calibration, suggesting that the FLASHTic can be effectively utilized for both monitoring and terminating the proton beam. The 80%–80% width of the SOBP was 2.01 cm. The peak dose rate at the SOBP proximal peak reached 105.03 Gy/s, with an average of 96.18 Gy/s over five days. Transitioning between FLASH and clinical mode required less than one hour without affecting the clinical beam.ConclusionsThe commissioning of a 230 MeV proton synchrocyclotron for SOBP FLASH delivery was achieved, providing a platform for preclinical small animal studies on pFLASH effects.

PurposeSpiral volumetric modulated arc therapy (SVMAT) is an integrated radiation therapy technique with longitudinal couch movement to generate a spiral/helical trajectory. This approach combines the merits of volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT). This study aimed to investigate the treatment planning of SVMAT for whole-brain radiotherapy (WBRT) with simultaneous integrated boost (SIB) for a large number (> 40) of metastases.Materials and methodsTen patients with multiple brain metastases (40–120 metastases) were retrospectively enrolled. These patients had previously received treatment with HT using the WBRT + SIB technique. Prescribed doses of 40 Gy for the whole brain and 60 Gy for the metastases were delivered in 20 fractions. In this study, SVMAT plans were designed using DeepPlan (version 1.3, Wisdom Tech., Hefei, Anhui, China) as the treatment planning system for the radiotherapy machine NeuRT Aurora (Neusoft IntelliRay Technology, Shenyang, Liaoning, China). In all SVMAT plans, the patient couch was set to move out after specified multiple gantry rotations and then move in within a single treatment fraction. The number of gantry rotations ranged between 6 and 16. These SVMAT plans were compared with HT and piecewise VMAT (previously proposed PVMAT) based on a plan quality metric (PQM) comprising 20 metrics.ResultsFor target coverage and conformity index (CI) of whole brain and metastases, no significant differences were observed between the SVMAT&HT or between SVMAT&PVMAT plans (p > 0.05). The sparing of right hippocampus, optic nerves and optic chiasm were improved using the SVMAT plan compared to the HT plan (p < 0.05). However, no significant difference was observed between the SVMAT and PVMAT plans for OAR sparing (p > 0.05). The mean total scores of PQM were 51.70 ± 8.14 (mean ± standard deviation), 53.24 ± 5.84, 53.64 ± 7.16, 54.24 ± 7.06, 54.60 ± 6.30, and 55.05 ± 6.18 points for SVMAT plans with gantry rotations of 6 8, 10, 12, 14, and 16, respectively. The average score for HT was 38.18 ± 5.48 points, which was significantly lower than that for the SVMAT plans (p < 0.05). Furthermore, the mean score for PVMAT was 54.34 ± 6.48 points, and no significant differences were observed between SVMAT and PVMAT (p > 0.05). The beam delivery time was shorter for SVMAT with 6 (271.5 ± 53.7 s), 8(310.3 ± 42.9 s), and 10(359.6 ± 34.4 s) rotations compared to HT (393.0 ± 25.0 s) (p < 0.05) and also shorter for SVMAT with six rotations compared to PVMAT (312.6 ± 53.7 s) (p < 0.05).ConclusionsFor WBRT + SIB, SVMAT achieved improved plan quality and higher delivery efficiency compared with HT and had similar plan quality compared with PVMAT.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13014-025-02742-4.

PurposeOXRAY, a state‐of‐the‐art radiation therapy system commercialized by Hitachi High‐Tech Ltd. in 2023, integrates unique beam delivery and image‐guided radiation therapy (IGRT) technologies as the successor to Vero4DRT. This study evaluated the performance of this second‐generation O‐ring‐shaped linear accelerator.MethodsThe percentage depth dose (PDD) and off‐center ratio (OCR) were calculated using the RayStation 2023B treatment planning system with multileaf collimator‐shaped square fields. PDDs were evaluated up to a depth of 250 mm and OCRs at depths of 15, 100, and 200 mm, compared with measurements. Patient‐specific quality assurance (PSQA) was conducted for 28 volumetric‐modulated arc therapy plans and evaluated using gamma pass rates (GPRs) based on a 3%/2 mm criterion. The biaxial rotational dynamic radiation therapy (BROAD‐RT) performance was validated with 25 trajectories. A tracking experiment under rotational irradiation was performed to assess the tracking accuracy. Additionally, image‐guidance systems (kV X‐ray and kV cone‐beam computed tomography) were evaluated using anthropomorphic phantoms. The localization accuracy (LA) was determined by comparing the known offsets with the noted differences between the initial and corrected positions.ResultsDifferences between the calculated and measured data were within the tolerance limits defined in European Society for Radiotherapy and Oncology Booklet 7 and American Association of Physicists in Medicine (AAPM) Medical Physics Practice Guideline 5.b. The median PSQA GPRs exceeded 95%, satisfying AAPM Task Group‐218 criteria. BROAD‐RT demonstrated submillimeter accuracy (within 0.4 mm), even for complex trajectories. The tracking accuracy remained within 1 mm even during rotational delivery. LA was within 0.5 mm for translational shifts and 0.5° for rotational adjustments.ConclusionOXRAY demonstrated clinically acceptable beam quality and high‐precision dose delivery outcomes. The tracking accuracy was maintained under rotational irradiation. Automatic image registration enabled accurate, reproducible patient positioning, supporting reliable IGRT implementation. These findings offer practical guidance and technical benchmarks for institutions adopting OXRAY.

Beam delivery methods for laser-driven proton sources

In image-guided radiotherapy (IGRT), four-dimensional cone-beam computed tomography (4D-CBCT) is critical for assessing tumor motion during a patient's breathing cycle prior to beam delivery. However, generating 4D-CBCT images with sufficient quality requires significantly more projection images than a standard 3D-CBCT scan, leading to extended scanning times and increased imaging dose to the patient. To introduce a novel spatiotemporal Gaussian neural representation framework to reconstruct high-temporal dynamic CBCT images from 1-minute acquisition, preserving motion dynamics and fine spatial details without relying on prior images or motion models. Our framework employs a differentiable 4D Gaussian representation initialized from average CBCT images. Gaussian points are characterized by position, covariance, rotation, and density, offering a compact and dynamic model for CBCT scenes. A Gaussian deformation network, incorporating a HexPlane encoder and multi-head decoder, predicts Gaussian deformations to minimize L1 and structural similarity index measure (SSIM) losses between rendered and measured projections. Adaptive Gaussian control refines the representation by pruning underutilized Gaussians and densifying points in high-gradient regions. The method was benchmarked on the AAPM SPARE challenge datasets and further validated with clinical CBCT scans from a Varian TrueBeam system. For the AAPM SPARE challenge datasets, the performance of the proposed method was evaluated using the root-mean-squared-error (RMSE) and the structural similarity index (SSIM) in the four regions of interest: Body, Lung, PTV, and Bone. The geometric accuracy was evaluated by calculating the registration error when aligning the tumor to the ground truth using the Elastix package, focusing on pixels within the planning target volume (PTV). To demonstrate our method's capability in high-temporal motion dynamic modeling using extremely undersampled projections, the clinical half-fan projections from a 1-minute Varian TrueBeam acquisition were sorted into 50 phases with approximately 18 projections per phase, significantly finer than the commonly used 10-phase binning. Compared to the AAPM SPARE challenge participant methods, our method achieved superior geometric accuracy in terms of PTV alignment error, and comparable RMSE and SSIM when no prior 4DCT or motion model is used for our reconstruction. For PTV alignment, our method achieved translational and rotational errors of 0.54mm (LR), 0.76mm (SI), 1.36mm (AP), 0.55° (rAP), and 0.93° (rSI), and 1.31° (rLR), respectively. For high temporal dynamic CBCT reconstruction, our method successfully reconstructed a 50-phase CBCT from a 1-minute Varian Truebeam half-fan scan, demonstrating effective streak artifact suppression, respiratory motion preservation, and fine detail restoration. Reconstruction on a single NVIDIA RTX A6000 GPU required approximately 30-80 min, depending on the number of Gaussian points used (ranging from 50 to 400K), to reconstruct CBCT from 680 projections acquired with a 30 × 40cm detector. Our code and reconstruction results can be found at: https://github.com/fuyabo/4DGS_for_4DCBCT/tree/main. The spatiotemporal Gaussian framework is a novel data-driven dynamic CBCT reconstruction technique that features excellent geometric accuracy in terms of PTV alignment and high-temporal motion modeling, indicating promise for tumor motion assessment and high-temporal respiratory motion modeling based on a 1-minute half-fan scan prior to beam delivery.

PurposeLattice radiation therapy (LRT) is a type of spatially fractionated radiation therapy that has emerged as an effective treatment approach for bulky solid tumors. RapidArc Dynamic (RAD) is a novel beam delivery approach that may be advantageous for LRT. The purpose of this in silico study was to evaluate and compare a novel RAD-based LRT approach (RAD-LRT) with conventional volumetric modulated arc therapy (VMAT)-based LRT (VMAT-LRT).MethodsTwenty patients with bulky liver tumors treated with RT were retrospectively identified. VMAT-LRT and RAD-LRT plans were generated for all patients. Lattice spheres were placed in a standardized hexagonal pattern with alternating high-dose spheres (vertex tumor volume high [VTVH], analogous to the peak dose) and low-dose control spheres (vertex tumor volume low [VTVL], analogous to the valley dose). Gross tumor volumes (GTVs)<1,000 cm3 and GTVs ≥1,000 cm3 were planned with 1.0-cm-diameter spheres (n=10) and 1.5-cm-diameter sphere (n=10), respectively. A prescription dose of 20 Gy to 80% of the VTVH was utilized. LRT dose metrics (e.g., peak-to-valley dose ratios, VTVH D80, VTVL Dmean) were calculated and were compared using paired Wilcoxon sign-ranked test. Planning efficiency was assessed by evaluating planning structures, planning time, and number of treatment fields.ResultsFor all 20 cases, RAD-LRT achieved superior plan quality than VMAT-LRT, indicated by similar prescription dose coverage (group mean, VTVH D80: 20.40 Gy for VMAT-LRT, 20.50 Gy for RAD-LRT) but significantly lower valley dose (group mean, VTVL mean dose: 3.40 Gy for VMAT-LRT, 2.20 Gy for RAD-LRT, p<0.0001). Compared to VMAT-LRT, RAD-LRT required fewer planning structures (mean ± SD, 9 ± 1 for VMAT-LRT, 4 ± 1 for RAD-LRT), less planning time (26 ± 8 min for VMAT-LRT, 18 ± 11 min for RAD-LRT), and fewer treatment beams (5 ± 1 arcs for VMAT-LRT, 1 arc with 4 ± 1 static ports for RAD-LRT). RAD-LRT also had significantly higher peak-to-valley dose ratios (group mean, VTVH/VTVL D90 ratio: 8.92 for VMAT-LRT, 18.20 for RAD-LRT, p<0.0001).ConclusionRAD may offer a unique approach to Lattice RT. RAD-LRT generated high quality plans with notable treatment planning efficiency, allowing for creation of quality plans without extensive planning time and LRT expertise.

The use of very high-energy electron (VHEE) beams for radiotherapy has been actively studied for over two decades due to their advantageous dose distribution, deep penetration depth, and great potential of ultrahigh dose-rate irradiation. Recently, laser-plasma wakefield accelerator (LWFA) has emerged as a promising method for the compact generation of VHEE beams, due to its substantially higher accelerating gradients compared to traditional radio-frequency accelerators. However, how to compactly deliver the LWFA-based VHEE beams of relatively large energy spread and create a maximum dose deeply inside the body remains very challenging. In this article, we present a simple dose delivery scheme utilizing only two dipole magnets for LWFA-based VHEE treatment. By adjusting the magnet strengths, the electron beams can be guided along different angular trajectories toward a precise position as deep as 20 cm within a water phantom, creating a maximum dose over the target region and significantly reducing the entrance dose. Supported by Monte Carlo simulations, such a beam delivery approach is demonstrated to be insensitive to the beam energy spread and meanwhile capable of controlling precisely the dose-peak position in both lateral and longitudinal directions. As such, a uniform dose peak can be generated by the weighted sum of VHEE beams that reach different dose-peak depths. These results demonstrate that LWFA-based VHEE beams can be compactly delivered into a deep-seated tumor region in a controllable manner, thus advancing the development of the VHEE radiotherapy toward the practical clinical applications in the near future.

Radiation therapy has undergone unprecedented advances over the past four decades, both in the understanding of radiobiologic effects and in the technical features of external beam delivery. The extent and scope of these changes have largely remained unappreciated outside the specialty of radiation oncology. The net effect of these advances has been improved dosimetry whereby radiotherapy can more evenly target a planned tissue volume while sparing normal tissues. The term dosimetry describes the evenness (homogeneity) and sharpness (conformality) of photon irradiation. Improved efficacy and safety are now reliably deliverable, prompting a need for a general re-appraisal of the place of modern radiotherapy across the spectrum of skin cancer management. Improved techniques are now widely available for the treatment of high-risk or extensive skin cancers, multiple in-field tumours and severe skin field cancerization. Specialised techniques in development include the use of extended radiation field techniques for micrometastatic disease in lymphatic corridors and harnessing the immune stimulatory potential of radiotherapy, especially in conjunction with immunotherapy and targeted therapies. This review aims to provide a summary of these changes for the non-radiation oncologist. The major advances in radiotherapy most relevant to skin cancer will be discussed along with the evidence for several emerging new applications in cancer management.

Abstract This study summarizes the final stage of work done at NCBJ in conjunction with the ongoing large scale International Fusion Materials Facility: Demo Oriented Neutron Source (DONES) project. DONES will be a neutron source with sufficiently high intensity and spectral range of neutrons generated in D-T reactions to enable the generation of structural defects in materials at the level of 20 dpa. Currently existing devices cannot achieve these properties. Our work optimized proton and deuteron beam delivery from a commissioned quadruple accelerator to the entry point of a planned high energy beam transport (HEBT) section in the DONES system. We considered two variants: a beam led by solenoids and a beam led by quadruples. Additional specifications required the insertion of a diagnostic plate that could not be separated by any other component, such us a solenoid or a quadruple. Using beam dynamics calculations, we delivered each beam from the radio frequency quadruple (RFQ) section to the entrance of HEBT section with the goal of minimizing any possible beam losses. We used TraceWin code developed by CEA Saclay for linear and non-linear, 2D or 3D, charged particle beam dynamics calculations and optimization of beam parameters. Based on the performed calculations and optimizations we recommended implementing a commissioning line with solenoids as leading elements.

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

Timescale of FLASH Sparing Effect Determined by Varying Temporal Split of Dose Delivery in Mice.

IntroductionLinear accelerators require a large amount of data to be collected daily, monthly and annually to verify safe deliveries for patients. Different detectors have been utilized to improve the simplicity, efficiency and accuracy of the various experimental setups required to collect the necessary data resulting in reduced data collection and evaluation time. Plastic scintillators are stable and energy independent radiation detectors with high spatial resolution that emit light proportional to the amount of radiation incident on them. With an appropriate photodetector and technique to measure and analyze the light that is emitted, scintillators can be utilized to measure dosimetric parameters necessary for various monthly quality assurance requirements.MethodsA uniform cylindrical plastic scintillator imaged by a complementary metal oxide semiconductor (CMOS) camera is designed to act as a radiation detector to measure 2D projections of linear accelerator beams. Beams were delivered to the detector to evaluate machine quality assurance (QA) parameters, including beam energy, output, profile consistency and reproducibility as described by TG‐198. These measurements were compared to calculations from the Eclipse treatment planning system (TPS). Typical monthly quality assurance (QA) beams were delivered and 2D projections of the scintillation light were measured to validate the accuracy and reproducibility of this detector system for monthly QA.ResultsThe plastic scintillator was able to accurately characterize the radiation beam. Energy and profile measurements were reproducible and within 2%/2mm of calculations in the TPS. Output measurements had maximum variations of up to 1.3% and average differences of 0.5%.ConclusionA simple cylindrical plastic scintillator and CMOS camera radiation detector setup was designed and tested for measuring monthly QA dosimetric parameters specified by TG‐198 with accurate and reproducible output, energy and profiles measurements. This method reduces the number of measurements required, allowing multiple parameters to be evaluated in a single beam delivery.

This study aimed to evaluate the accuracy of surface-guided radiotherapy (SGRT)-based positioning and surface tracking in breast radiotherapy using the ExacTrac Dynamic (ETD). We retrospectively evaluated 16 patients who underwent breast cancer treatment. All patients were positioned using SGRT with ETD under free-breathing conditions. Orthogonal kilovoltage (kV) image acquisition was then acquired using the linear accelerators' kV imagers and registered to digitally reconstructed radiographs. For surface tracking, vertical breast surface motion waveforms obtained with ETD were compared with those captured using an electronic portal imaging device (EPID) during beam delivery. The agreement between ETD and EPID in terms of vertical breast surface displacement was evaluated using the cross-correlation coefficient. For patient positioning, the mean ± standard deviation (SD) of X-ray shift values (mm) were - 2.8 ± 2.6 (vertical), - 2.2 ± 4.5 (longitudinal), and 0.3 ± 2.1(lateral). The percentage of X-ray shift < 5mm was 82% (vertical), 66% (longitudinal), and 92% (lateral). The setup margins (mm) were 5.4 (vertical), 9.0 (longitudinal), and 3.8 (lateral). For surface tracking, the mean ± SD of the cross-correlation coefficient was 0.93 ± 0.02, indicating a high correlation between the ETD and EPID waveforms. The mean amplitude difference between waveforms obtained by ETD and EPID was 0.46mm. SGRT-based positioning with ETD may result in errors exceeding 5mm relative to the treatment planning position in the longitudinal direction; combining it with image-guided radiotherapy is therefore recommended. Surface tracking with ETD demonstrated high tracking accuracy in tracking human body surface temperature distribution.

One of the main challenges of utilizing spot-scanning proton arc therapy (SPArc) is treatment delivery efficiency. Previous studies focus on reducing the number of energy layers by ascending switching to shorten the beam delivery time. However, this is not true of all proton therapy systems. The new energy layer switching system was recently upgraded in the University Medical Center Groningen (UMCG), which enables a fast energy layer ascending switching (ELAS). We introduce a novel adaptive energy switching SPArc optimization algorithm (SPArc-AES) based on the machine-specific delivery characteristics of proton therapy systems. The SPArc-AES optimization algorithm is based on the polynomial increasing feature of energy layer ascending switching. K-Medoids clustering analysis and simulated annealing algorithm were used to optimize the energy delivery sequence. Ten cases were selected to evaluate the plan quality, plan robustness, and the delivery efficiency compared with the previously SPArc energy sequence optimization algorithm, SPArc_seq. Without extra constraints in the energy ascending constraints, the SPArc-AES offers a better plan quality and robustness, while the treatment delivery efficiency was significantly improved compared to the SPArc_seq. More specifically, SPArc-AES effectively shortened the energy layer switching time and the beam delivery time by 34.03% and 31.10%, respectively, while offering better target dose conformality and generally lower dose to organs-at-risk. Based on the machine-specific delivery characteristics, we introduced a novel adaptive energy switching algorithm for efficient SPArc optimization, which could significantly improve delivery efficiency while enhancing the plan quality by eliminating no longer necessary constraints on the total number of energy layer ascending switching.

Objective.This work aims to evaluate the ability of novel detector components to measure with submillimeter resolution in beam positron emission tomography (PET) signals produced by10C and11C radioactive ion beams stopped in PMMA targets and to validate a simulation toolkit for reproducing beam physics and PET detector responses within the framework of the biomedical applications of radioactive ion beam (BARB) project.Approach.The PET system response was assessed by visualizing the radioactive distributions of the beams stopped in tissue surrogate phantoms, and the capacity of the simulation toolkit was evaluated by comparing the experimental results with simulations, both for the depth-dose distribution and PET imaging.Main results.The detector assembly accurately visualized the PET signal with submillimeter resolution, achieving the objective of measuring the difference in the positron range between10C and11C. The simulation toolkit effectively reproduced the beam characteristics and detector responses, showing a high degree of agreement between the simulated and experimental PET profiles under different beam delivery conditions.Significance.These findings demonstrate the precision and reliability of the novel in-beam PET detector technology and simulation toolkit for small animals, establishing a solid foundation for the second phase of the BARB project, which involves preclinical irradiation of living mice.