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X-irradiation of blood products is an alternative for gamma-ray to prevent post-transfusion GvHD. However, commercial X-irradiators are not widely available while little is known about their safety and efficacy for platelet products. This study introduces an efficient, accessible and cost-effective "X irradiation system" for platelet concentrates (PCs). By constructing a suitable radiation box (phantom) for a clinically available linear accelerator, an "X irradiation system" was designed specifically for PCs. PCs were divided into three equal bags either exposed to X- and gamma-irradiation or kept unirradiated (control). Irradiation-induced inhibition of T cells proliferation was examined by MTT and cell cycle assays on mononuclear cells (MNCs) obtained from PCs. The inhibitory effect of irradiation on allorecognition ability of MNCs was assessed by mixed lymphocyte reaction where MTT evaluated lymphocyte proliferation responses and flowcytometry examined CD8+T lymphocytes activity. Platelet activation was also examined with P-selectin expression and PAC-1 binding by flowcytometry. X- and gamma-irradiation reduced T cell proliferation while disturbing the cell-cycle with reduced entry of T-cells into the S phase and their G2 arrest. Both types of irradiations also effectively reduced "lymphocyte allorecognition responses" while inactivating CD8+T lymphocytes in platelet products but with no significant effect on platelet activity. This is the first study that showed "X irradiation system" effectively suppresses T cell proliferation and CD8+T lymphocyte activity in platelet products, with no effect to platelet quality and activation markers. This may suggest the LINAC-based "X irradiation system" with a dose of 30Gy as efficient and safe as gamma-irradiation for platelet products. [ABSTRACT FROM AUTHOR]

Task Group (TG) 314 of the American Association of Physicists in Medicine (AAPM) was charged to develop guidance for recovering from fault states in radiation therapy, specifically regarding the delivery of photon or electron beams using a linear accelerator (linac) including ancillary systems. The fault conditions addressed may involve software, hardware, or a combination of causes. The report provides detailed recommendations for the proactive steps to be taken before a fault, the actions to be taken at the time of a fault, and the safety steps before returning a linac to clinical service, as well as the activities that device manufacturers and standard organizations can do to prevent and resolve the faults. A user‐maintained log of prior faults; establishment of remote access by the vendor; and user training in emergency gantry, couch, and door motions are all useful proactive steps. At the moment of downtime and after ensuring the safety of the patient, the report stresses the importance of capturing fault information, prompt contact with the service engineer after the initial assessment, and considerations for communicating the estimated duration before the linac is returned to service. The medical physicist has a critical responsibility to assess the impact of the fault on patient care. Before resuming clinical use, the medical physicist must both determine the level of testing required to ensure safe operation of the linac and ensure any partially or totally delivered treatments have been correctly saved for accurate completion of the treatment fraction. The report stresses the roles of the radiation therapist, medical physicist, and service engineer to efficiently and safely address linac downtime. The appendices contain a description of the efforts of several organizations regarding linac safety: Integrating the Healthcare Enterprise—Radiation Oncology, International Standards Organization/International Electrotechnical Commission, Radiation Oncology Safety Stakeholder Initiative, and the AAPM Vendor Relations and Product Usability Subcommittee.Disclaimer: The recommendations of this TG should not be used to establish regulations. These recommendations are guidelines for Qualified Medical Physicists and others to use and appropriately interpret for their institution and clinical setting. Each institution may have site‐specific or state‐mandated needs and requirements which may modify their usage of these recommendations. [ABSTRACT FROM AUTHOR]

Introduction: This systematic review study investigated the cost-effectiveness of stereotactic radiotherapy (SRT) and stereotactic radiosurgery (SRS) for treatment of various types of cancers. Methods: PubMed, Scopus, and Web of Science were searched from 30 December 1990 to 1 January 2023. The entered studies were screened in accordance with the inclusion criteria. The inclusion criteria encompassed all types of economic evaluation studies that investigated SRT/SRS technologies in the treatment of various cancers. Results: A total of 47 articles were included in the review. The findings suggest that the use of Linear accelerator technology for the treatment of lung cancer (8 out of 12 studies) and prostate cancer (4 out of 5 studies) was a cost-effective strategy. Linear accelerator was found to be cost-effective in the treatment of liver metastases and liver cancer (2 out of 5 studies). All of the included studies that used Gamma Knife technology in brain metastases reported Gamma-Knife was a cost-effective treatment. Furthermore, in the treatment of prostate and liver cancer, proton therapy was identified as a cost-effective option than other treatments. Conclusions: This study confirms that SRT/SRS is a cost-effective procedure for the treatment of various types of cancers. Therefore, it is recommended to use SRT/SRS technology for optimal use of resources. [ABSTRACT FROM AUTHOR]

Brainstem metastases are challenging to manage owing to the critical neurological structures involved. Although stereotactic radiotherapy (SRT) offers targeted high doses while minimizing damage to adjacent normal tissues, the optimal dose fractionation remains undefined. This study evaluated the efficacy and safety of multifraction SRT with an inhomogeneous dose distribution. This retrospective study included 31 patients who underwent 33 treatments for 35 brainstem lesions using linear accelerator-based multifraction SRT (30 Gy in five fractions, 35 Gy in five fractions or 42 Gy in 10 fractions) with an inhomogeneous dose distribution (median isodose, 51.9%). The outcomes of interest were local failure, toxicity and symptomatic failure. The median follow-up time after brainstem SRT for a lesion was 18.6 months (interquartile range, 10.0–24.3 months; range, 1.8–39.0 months). Grade 2 toxicities were observed in two lesions, and local failure occurred in three lesions. No grade 3 or higher toxicities were observed. The 1-year local and symptomatic failure rates were 8.8 and 16.7%, respectively. Toxicity was observed in two of seven treatments with a gross tumor volume (GTV) greater than 1 cc, whereas no toxicity was observed in treatments with a GTV less than 1 cc. No clear association was observed between the biologically effective dose of the maximum brainstem dose and the occurrence of toxicity. Our findings indicate that multifraction SRT with an inhomogeneous dose distribution offers a favorable balance between local control and toxicity in brainstem metastases. Larger multicenter studies are needed to validate these results and determine the optimal dose fractionation. [ABSTRACT FROM AUTHOR]

Purpose: We aimed to show the framework of the six‐sigma methodology (SSM) that can be used to determine the limits of QC tests for the linear accelerator (Linac). Limits for QC tests are individually determined using the SSM. Methods and Materials: The SSM is based on the define‐measure‐analyze‐improve‐control (DMAIC) stages to improve the process. In the "define" stage, the limits of QC tests were determined. In the "measure" stage, a retrospective collection of daily QC data using a Machine Performance Check platform was performed from January 2020 to December 2022. In the "analyze" stage, the process of determining the limits was proposed using statistical analyses and process capability indices. In the "improve" stage, the capability index was used to calculate the action limits. The tolerance limit was established using the larger one of the control limits in the individual control chart (I‐chart). In the "control" stage, daily QC data were collected prospectively from January 2023 to May 2023 to monitor the effect of action limits and tolerance limits. Results: A total of 798 sets of QC data including beam, isocenter, collimation, couch, and gantry tests were collected and analyzed. The Collimation Rotation offset test had the min‐Cp, min‐Cpk, min‐Pp, and min‐Ppk at 2.53, 1.99, 1.59, and 1.25, respectively. The Couch Rtn test had the max‐Cp, max‐Cpk, max‐Pp, and max‐Ppk at 31.5, 29.9, 23.4, and 22.2, respectively. There are three QC tests with higher action limits than the original tolerance. Some data on the I‐chart of the beam output change, isocenter KV offset, and jaw X1 exceeded the lower tolerance and action limit, which indicated that a system deviation occurred and reminded the physicist to take action to improve the process. Conclusions: The SSM is an excellent framework to use in determining the limits of QC tests. The process capability index is an important parameter that provides quantitative information on determining the limits of QC tests. [ABSTRACT FROM AUTHOR]

Abstract X-irradiation of blood products is an alternative for gamma-ray to prevent post-transfusion GvHD. However, commercial X-irradiators are not widely available while little is known about their safety and efficacy for platelet products. This study introduces an efficient, accessible and cost-effective “X irradiation system” for platelet concentrates (PCs). By constructing a suitable radiation box (phantom) for a clinically available linear accelerator, an “X irradiation system” was designed specifically for PCs. PCs were divided into three equal bags either exposed to X- and gamma-irradiation or kept unirradiated (control). Irradiation-induced inhibition of T cells proliferation was examined by MTT and cell cycle assays on mononuclear cells (MNCs) obtained from PCs. The inhibitory effect of irradiation on allorecognition ability of MNCs was assessed by mixed lymphocyte reaction where MTT evaluated lymphocyte proliferation responses and flowcytometry examined CD8+T lymphocytes activity. Platelet activation was also examined with P-selectin expression and PAC-1 binding by flowcytometry. X- and gamma-irradiation reduced T cell proliferation while disturbing the cell-cycle with reduced entry of T-cells into the S phase and their G2 arrest. Both types of irradiations also effectively reduced “lymphocyte allorecognition responses” while inactivating CD8+T lymphocytes in platelet products but with no significant effect on platelet activity. This is the first study that showed “X irradiation system” effectively suppresses T cell proliferation and CD8+T lymphocyte activity in platelet products, with no effect to platelet quality and activation markers. This may suggest the LINAC-based “X irradiation system” with a dose of 30Gy as efficient and safe as gamma-irradiation for platelet products.

Radiation therapists, also known as radiotherapy technologists, are allied health professionals who specialise in providing high doses of radiation to patients with malignant growths. High-energy radiation damages cells’ genetic material {Deoxyribonucleic Acid (DNA)}, stopping them from replicating and multiplying further. Radiation can be used to treat cancer or as a highly effective palliative therapy to alleviate cancer-related pain in patients. Radiation therapy can be used in conjunction with other treatments, including surgery, chemotherapy, and immunotherapy. Because radiation harms both healthy tissues and malignant cells, the primary objective of radiation therapy is to optimise radiation exposure to abnormal cancer cells while avoiding irradiation of healthy tissues adjacent to or in the path of radiation. Remarkable precision is required to provide ionising radiation to patients and target specific cells for consistent, accurate, and successful radiation treatment. A team consisting of radiation oncologists, medical physicists, radiation therapists, medical dosimetrists, and nurses work together to achieve this goal. Radiation therapists are responsible for delivering radiation treatment, as well as maintaining and testing the equipment used to monitor and administer the treatment. The radiation therapist administers the patient’s treatment dose according to the prescription plan made by the radiation oncologists and medical physicists. Radiation therapists must communicate with patients and their families, respond to their inquiries, and clarify the radiation treatment plan. They must also track the patient’s progress and report any changes to their seniors. Radiation therapists must maintain high levels of precision while administering therapy, think critically, and exercise autonomous, professional, and ethical judgment in all aspects of their work. The field of radiotherapy is continuously evolving with new advancements in technology and treatment delivery techniques that maximise patient satisfaction and treatment delivery efficacy. Radiation therapists undergo continuing education and training to broaden their knowledge of the field and stay current with standard practice. This review addresses the critical role of radiation therapists in clinical radiation therapy practices. It highlights their significance in delivering safe and effective treatment to radiotherapy patients. The review covers various aspects, including the responsibilities of technologists in treatment planning, equipment operation, patient care and safety, quality assurance, and research. This present review provides a comprehensive understanding of the importance of well-trained and skilled radiation therapists in ensuring the success of radiation therapy treatments.

This paper describes the design of an innovative linear accelerator image-guided radiosurgery (IGRS) device, which is based on a composite twofold rotary gantry structure. The paper discusses five aspects of the innovative device: its overall composition, the safety net space created by the accelerator radiation head as it rotates around the patient’s longitudinal axis, the non-coplanar spherical coverage in the direction of the incidence angle for quasi-4π delivery, the structural features of the composite twofold rotary gantry, and the processes of treatment planning and implementation. It elaborates on the device’s manufacturing feasibility, safety, effectiveness, accuracy, and efficiency. The conclusion is that this innovative device design holds significant development value and market promotion potential.

In order to meet the power source requirements of C-band linear accelerators for industrial applications, a C-band high power klystron operating at a frequency of 5 712 MHz was developed. For this klystron, the development objective of the output power is no less than 3.5 MW and the efficiency is no less than 35%. During the entire design process, the output power was optimized to over 4 MW and the power efficiency over 40% to compensate for the disadvantage effects caused by manufacturing and testing errors in the development processes. Firstly, the electron optics system with a Pierce gun and a combination of five forward and one reverse focusing coils was designed. The Pierce gun with a perveance of 2 μP was adopted and the beam voltage and current were chosen as 120 kV and 83.3 A. By iteratively calculating the structure of the electron gun with EGUN code and optimizing the magnetic field between the electron gun and the beam-wave interaction section, the final electron beam pass rate reaches 100% and the fluctuation of the beam envelop is only 4.8%. Secondly, the efficiency optimization and PIC simulation of the beam-wave interaction section were carried out using the one dimensional AJDISK code, 1.5 dimensional KlyC code and three dimensional CST code. The scheme of six resonant cavities was ultimately determined and the basic cavity parameters were optimized based on the principles of stagger tuning. The simulation results of different codes all indicate that the efficiency can reach above 46.5%, and the output power can all reach above 4.650 MW. And the influence of frequency errors and output external quality factor on efficiency was also analyzed to guide the manufacturing process. After that, the mechanical structure of cavities was designed and all cavities were manufactured with oxygen free copper. The cold test and tuning of all cavities were carried out and the frequency error is mostly within the range of ±5 MHz, which basically does not affect the output power. Finally, the electron gun, the beam-wave interaction section and the collector were welded together. And the high power test was conducted immediately after the first high power C-band klystron protype was completed. When the electron gun operates at the voltage of 115 kV and current of 79.6 A, the klystron peak output power reaches 3.52 MW, the gain reaches 45.5 dB and the efficiency reaches about 38.5%. The high power test results show that this C-band high power klystron achieves the expected development goals.

The electron beam (EB) energy is one of the most crucial parameters of EB treatment applications. It governs the dose distribution inside the bulk of the product treated with an energetic EB. An online monitoring and robust system is proposed for EB energy monitoring for radio frequency (RF) linear accelerator (LINAC). Attenuation method using dosimeter films is applied to reproduce the range of electron beam in aluminum. In online monitoring system, two electrically isolated aluminum plates having identical shape but different thicknesses, as per full penetration thickness of electron beam, are used. The current constituted in each plate is measured by an oscilloscope with suitable resistors, by keeping the set up under the beam. The ratio of the current signal from the front plate to the sum of the signals from both plates is very sensitive to the beam energy. Here, an electron accelerator of 10 MeV is used to incorporate this device. Sensitivity and robustness are the key factors to make this device highly suitable for desirous applications of 10 MeV LINAC and also to meet the regulatory mandates related to energy limitations for industrial utilities.

Abstract Exposure to high, marginally lethal doses or higher of ionizing radiation, either intentional or accidental, results in injury to various organs. Currently, there is only a limited number of safe and effective radiation countermeasures approved by US Food and Drug Administration for such injuries. These approved agents are effective for only the hematopoietic component of the acute radiation syndrome and must be administered only after the exposure event: currently, there is no FDA-approved agent that can be used prophylactically. The nutraceutical, gamma-tocotrienol (GT3) has been found to be a promising radioprotector of such exposure-related injuries, especially those of a hematopoietic nature, when tested in either rodents or nonhuman primates. We investigated the nature of injuries and the possible protective effects of GT3 within select organ systems/tissues caused by both non-lethal level (4.0 Gy), as well as potentially lethal level (5.8 Gy) of ionizing radiation, delivered as total-body or partial-body exposure. Results indicated that the most severe, dose-dependent injuries occurred within those organ systems with strong self-renewing capacities (e.g., the lymphohematopoietic and gastrointestinal systems), while in other tissues (e.g., liver, kidney, lung) endowed with less self-renewal, the pathologies noted tended to be less pronounced and less dependent on the level of exposure dose or on the applied exposure regimen. The prophylactic use of the test nutraceutical, GT3, appeared to limit the extent of irradiation-associated pathology within blood forming tissues and, to some extent, within the small intestine of the gastrointestinal tract. No distinct, global pattern of bodily protection was noted with the agent’s use, although a hint of a possible radioprotective benefit was suggested not only by a lessening of apparent injury within select organ systems, but also by way of noting the lack of early onset of moribundity within select GT3-treated animals.

Radiation therapists, also known as radiotherapy technologists, are allied health professionals who specialise in providing high doses of radiation to patients with malignant growths. High-energy radiation damages cells' genetic material {Deoxyribonucleic Acid (DNA)}, stopping them from replicating and multiplying further. Radiation can be used to treat cancer or as a highly effective palliative therapy to alleviate cancer-related pain in patients. Radiation therapy can be used in conjunction with other treatments, including surgery, chemotherapy, and immunotherapy. Because radiation harms both healthy tissues and malignant cells, the primary objective of radiation therapy is to optimise radiation exposure to abnormal cancer cells while avoiding irradiation of healthy tissues adjacent to or in the path of radiation. Remarkable precision is required to provide ionising radiation to patients and target specific cells for consistent, accurate, and successful radiation treatment. A team consisting of radiation oncologists, medical physicists, radiation therapists, medical dosimetrists, and nurses work together to achieve this goal. Radiation therapists are responsible for delivering radiation treatment, as well as maintaining and testing the equipment used to monitor and administer the treatment. The radiation therapist administers the patient's treatment dose according to the prescription plan made by the radiation oncologists and medical physicists. Radiation therapists must communicate with patients and their families, respond to their inquiries, and clarify the radiation treatment plan. They must also track the patient's progress and report any changes to their seniors. Radiation therapists must maintain high levels of precision while administering therapy, think critically, and exercise autonomous, professional, and ethical judgment in all aspects of their work. The field of radiotherapy is continuously evolving with new advancements in technology and treatment delivery techniques that maximise patient satisfaction and treatment delivery efficacy. Radiation therapists undergo continuing education and training to broaden their knowledge of the field and stay current with standard practice. This review addresses the critical role of radiation therapists in clinical radiation therapy practices. It highlights their significance in delivering safe and effective treatment to radiotherapy patients. The review covers various aspects, including the responsibilities of technologists in treatment planning, equipment operation, patient care and safety, quality assurance, and research. This present review provides a comprehensive understanding of the importance of well-trained and skilled radiation therapists in ensuring the success of radiation therapy treatments. [ABSTRACT FROM AUTHOR]

Introduction: Measurement of entrance dose and dose at different depth is essential to avoid over dose and under dose of patients. The aim of this study is to verify the variation in the absorbed dose using a water equivalent material. Material and Methods: The plastic phantom was arranged on the couch of the halcyon linear accelerator by Varian with the farmer ionization chamber inserted and connected to the electrometer. The image of the setup was taken using the High-Quality Single 1280x1280x16 higher on the service mode, to check the alignment with the isocenter. The beam quality TPR20,10 (Tissue phantom ratio) was done to check the beam quality of the machine at a field size of 10 cm x 10 cm. The calibration was done using SAD type set-up at a depth of 5 cm. This process was repeated for ten consecutive weeks and the values recorded. Results: The results of the beam output for the teletherapy machine were satisfactory and accepted in comparison with the commissioned measurement of 0.62. The beam quality TPR20,10 (Tissue phantom ratio) was reasonable with respect to the beam quality of the machine at a field size of 10 cm x 10 cm. Conclusion: The results of the beam quality and the absorbed dose rate showed a good consistency over the period of ten weeks with the commissioned measurement value. [ABSTRACT FROM AUTHOR]

Background: The successful installation of linear accelerators (LINACs) depends on operator skill and experience, and its optimization can be further improved using vendor commissioning support. To facilitate the introduction of LINAC, Elekta provides commissioning support through Accelerated Go Live (AGL) using representative beam data. This study aimed to evaluate the effective commissioning of LINAC-assisted AGL complemented by additional measurements conducted by a user. Materials and Methods: Output doses were measured within a field size of > 3 cm2 using a single chamber with AGL and within a field size of > 2 cm² using three types of optimal chambers based on the field size adopted by the user. In all cases, the differences between the measured and calculated output doses were maintained at < 2%. Results: The accuracy of couch modeling was evaluated by measuring arc irradiation for three different field sizes, with the electron density value assigned as a dose difference of <2% between the measured and calculated values at 2% for all energies and field size of >3 cm2. Additionally, imaging scan parameters for cone beam computed tomography were optimized to reduce the radiation dose, in comparison to the initial vendor settings, by referencing IEC 60601-2-44 standards and examining results from neighboring facilities. Conclusions: AGL proved to be effective as a temporary check, but additional commissioning efforts by the user were necessary for a more thorough evaluation and more appropriate initiation, aligning with established clinical practices. [ABSTRACT FROM AUTHOR]

BACKGROUND: The polychromatic X-rays generated by a linear accelerator (Linac) often result in noticeable hardening artifacts in images, posing a significant challenge to accurate defect identification. To address this issue, a simple yet effective approach is to introduce filters at the radiation source outlet. However, current methods are often empirical, lacking scientifically sound metrics. OBJECTIVE: This study introduces an innovative filter design method that optimizes filter performance by balancing the impact of ray intensity and energy on image quality. MATERIALS AND METHODS: Firstly, different spectra under various materials and thicknesses of filters were obtained using GEometry ANd Tracking (Geant4) simulation. Subsequently, these spectra and their corresponding incident photon counts were used as input sources to generate different reconstructed images. By comprehensively comparing the intensity differences and noise in images of defective and non-defective regions, along with considering hardening indicators, the optimal filter was determined. RESULTS: The optimized filter was applied to a Linac-based X-ray computed tomography (CT) detection system designed for identifying defects in graphite materials within high-temperature gas-cooled reactor (HTR), with defect dimensions of 2 mm. After adding the filter, the hardening effect reduced by 22%, and the Defect Contrast Index (DCI) reached 3.226. CONCLUSION: The filter designed based on the parameters of Average Difference (AD) and Defect Contrast Index (DCI) can effectively improve the quality of defect images. [ABSTRACT FROM AUTHOR]

The ANTHEM (Advanced Technologies for Human-centered Medicine) Radio-Frequency Quadrupole (RFQ) will employ eight coaxial power couplers, which will be magnetically coupled to the device through a loop antenna. The coupler design can support up to 140 kW in continuous wave operation. This paper presents the design of the cavity used for high-power testing, with the primary objectives of both optimizing the coupling between the couplers and ensuring operations at the designated operating frequency. Furthermore, the paper encompasses thermal and structural assessments conducted through numerical simulations. [ABSTRACT FROM AUTHOR]

This study investigates how scattering foil materials and sampling holder placement affect electron energy distribution in electron beams from a modified medical linear accelerator for FLASH radiotherapy. We analyze electron energy spectra at various positions—ionization chamber, mirror, and jaw—to evaluate the impact of Cu, Pb-Cu, Pb, and Ta foils. Our findings show that close proximity to the source intensifies the dependence of electron energy distribution on foil material, enabling precise beam control through material selection. Monte Carlo simulations are effective for designing foils to achieve desired energy distributions. Moving the sampling holder farther from the source reduces foil material influence, promoting more uniform energy spreads, particularly in the 0.5–10 MeV range for 12 MeV electron beams. These insights emphasize the critical role of tailored material selection and sampling holder positioning in optimizing electron energy distribution and fluence intensity for FLASH radiotherapy research, benefiting both experimental design and clinical applications. [ABSTRACT FROM AUTHOR]

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Purpose: To directly compare the radiation and imaging isocenters of a proton treatment machine, we developed and evaluated a real‐time radiation isocenter verification system. Methods: The system consists of a plastic scintillator (PI‐200, Mitsubishi Chemical Corporation, Tokyo, Japan), an acrylic phantom, a steel ball on the detachable plate, Raspberry Pi 4 (Raspberry Pi Foundation, London, UK) with camera module, and analysis software implemented through a Python‐based graphical user interface (GUI). After kV imaging alignment of the steel ball, the imaging isocenter defined as the position of the steel ball was extracted from the optical image. The proton star‐shot was obtained by optical camera because the scintillator converted proton beam into visible light. Then the software computed both the minimum circle radius and the radiation isocenter position from the star‐shot. And the deviation between the imaging isocenter and radiation isocenter was calculated. We compared our results with measurements obtained by Gafchromic EBT3 film (Ashland, NJ, USA). Results: The minimum circle radii were averaged 0.29 and 0.41 mm while the position deviations from the radiation isocenter to the laser marker were averaged 0.99 and 1.07 mm, for our system and EBT3 film, respectively. Furthermore, the average position difference between the radiation isocenter and imaging isocenter was 0.27 mm for our system. Our system reduced analysis time by 10 min. Conclusions: Our system provided automated star‐shot analysis with sufficient accuracy, and it is cost‐effective alternative to conventional film‐based method for radiation isocenter verification. [ABSTRACT FROM AUTHOR]

Neural network-based surrogate models can provide fast, reliable and realistic models of accelerators. However, training a surrogate model from start-to-end is still a challenge. For accelerators with dozens or even hundreds of elements, training surrogate models can lead to a dimensional disaster. In this paper, we use a dual network with polynomial neural networks (PNNs) and long short-term memory (LSTM) nested structure to realize a start-to-end surrogate model of China Accelerator Facility for Superheavy Element (CAFe2). Results show that the PNN–LSTM model can effectively realize the surrogate model of CAFe2. Compared to the running speed of TraceWin multi-particle simulation, the new surrogate model has improved by about three orders of magnitude while ensuring a sufficiently good level of accuracy. Moreover, our model can efficiently generate a comprehensive set of beam parameters along the entire beamline, significantly enhancing its practicality as a surrogate model. [ABSTRACT FROM AUTHOR]

La radiochirurgie pour le traitement de la névralgie du trijumeau délivre une très forte dose en une seule séance, sur quelques millimètres, au niveau d'un isocentre unique placé le long du nerf. Nous présentons ici les différentes étapes qui ont été réalisées pour valider des petits faisceaux par collimateurs coniques, et rapportons les résultats cliniques des premiers patients pris en charge sur Novalis Tx® sans cadre invasif. Nous avons d'abord été évalué l'exactitude géométrique des collimateurs coniques de 4 et 6 mm à l'aide de tests de Winston-Lutz ; puis l'acquisition des données dosimétriques a été réalisée grâce à des détecteurs de haute résolution spatiale (microdiamant PTW 60019 et une diode E PTW 60017). Les facteurs correctifs du rapport TRS no 483 ont été appliqués pour le calcul des facteurs d'ouverture du collimateur. Ces données dosimétriques ont ensuite été comparées avec les données implémentées dans le système de planification de traitement iPlan®. Puis des tests end-to-end ont permis de contrôler l'ensemble du processus de traitement à l'aide d'un fantôme anthropomorphique stereotactic end-to-end verification. Entre 2020 et 2022, 18 patients ont été traités pour névralgie trigéminale réfractaire sur Novalis Tx® sans cadre invasif avec repositionnement par Exactrac®. Dix-sept patients ont été évalués (un a été perdu de vue) à l'aide du score du Barrow Neurological Institute pour l'évaluation de la douleur, et par IRM avec un suivi médian de 12 mois. Les critères de qualité d'exactitude géométrique et dosimétriques ont été atteints pour le cône de 6 mm mais pas pour le cône de 4 mm. Tous les patients ont été traités avec un cône de 6 mm avec une dose de 90 Gy prescrite à l'isocentre ciblée au niveau de la root entry zone. Le contrôle initial de la douleur a été obtenu chez 70,5 % de nos patients, et 53 % ont conservé ce contrôle avec un suivi médian de 12 mois. Toutes les récidives sont survenues dans un délai de 3 à 6 mois après la radiochirurgie. Aucune toxicité n'a été observée sur le tronc cérébral. Trois patients ont eu une hypoesthésie faciale non invalidante. Le traitement des névralgies trigéminales sur accélérateur linéaire dédié est un traitement de haute technicité dont l'exactitude et la sécurité est primordiale. Les mesures physiques ont permis la mise en service de la technique avec un cône de 6 mm. Nos premiers résultats cliniques sont conformes aux données de la littérature. Radiosurgery for the treatment of trigeminal neuralgia delivers a very high dose in a single fraction, over a few millimeters, at a single isocenter placed along the nerve. We present here the different steps that have been performed to validate small beams by conical collimators, and report the clinical results of the first patients treated on Novalis Tx®, frameless. First, the geometric accuracy of 4 and 6 mm conical collimators was evaluated using Winston-Lutz tests; then dosimetric data acquisition was performed using high spatial resolution detectors (PTW 60019 microdiamond and a PTW 60017 E-diode). The corrective factors of the TRS 483 report were applied to calculate the collimator aperture factors. These dosimetric data were then compared with the data implemented in the iPlan® treatment planning system. Then end-to-end tests were performed to control the entire treatment process using an anthropomorphic phantom "STEEV". Between 2020 and 2022, 18 patients were treated for refractory trigeminal neuralgia on Novalis Tx®, frameless, with Exactrac® repositioning. A total of 17 patients were evaluated (one was lost to follow-up) using the BNI score for pain assessment and MRI with a median follow-up of 12 months. The quality criteria of geometric and dosimetric accuracy were met for the 6-mm cone but not for the 4-mm cone. All patients were treated with a 6-mm cone with a dose of 90 Gy prescribed at the isocenter at the root entry zone. Initial pain control was obtained in 70.5% of our patients, and 53% maintained pain control with a median follow-up of 12 months. All recurrences occurred within 3 to 6 months after radiosurgery. No brainstem toxicity was observed. Six patients had non-disabling facial hypoesthesia, half of whom already had pretreatment hypoesthesia. The treatment of trigeminal neuralgia on a dedicated linear accelerator is a highly technical treatment whose accuracy and safety are paramount. The physical measurements allowed the commissioning of the technique with a 6 mm cone. Our first clinical results are in accordance with the literature. [ABSTRACT FROM AUTHOR]

The current study aimed to investigate boron carbide and boric acid nanoparticles (NPs) as absorbents for thermal neutrons and high-density polyethylene (HDPE) as a substrate and neutron moderator for fast neutrons. The goal was to assess the performance of boron carbide and boric acid NPs based on HDPE as a nanoshield of photoneutrons from medical linear accelerators. This study was conducted in two parts of simulation and practice. The Monte Carlo (MC) simulation involved modeling and verification of the single-layer, double-layer, and combined nanoshields by selecting nanomaterials and substrates and, finally, calculating the macroscopic cross-sections. The practical part involved manufacturing nanoshields based on the simulation results and evaluating the manufactured nanocomposites via experimental measurements. MC simulation results with an uncertainty of less than 1% showed that for the monolayer samples, the best result belonged to boron carbide at a concentration of 10% and a macroscopic cross-section of 0.933 cm–1. At a concentration of 20%, the highest value among the double-layer samples was 0.936 cm–1 and for the combined samples, this value was 0.928 cm–1. Boron carbide single-layer nanocomposites at a 10% concentration, as well as the bilayer nanoshield of 10% boron carbide and 20% boric acid performed well; however, the best performance belonged to the nanoshield with a macroscopic cross-section of 0.960 and the combination containing 5% boron carbide and 10% boric acid. The research suggests that utilizing boron carbide and boric acid nanoshields in combination with HDPE holds promise as a viable approach to protecting from the photoneutrons. Further exploration of these nanocomposite shields and their practical applications is warranted, with the potential to yield significant advancements in radiation therapy safety and efficacy. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the trends in the platform for stereotactic radiotherapy to the brain (SRT), utilizing the open data of the National Database published by the Ministry of Health, Labour, and Welfare. Materials and methods: This study analyzed data from FY2014 to FY2021. The practices included in the study were gamma knife surgery (GKS) and SRT with a linear accelerator (LINAC). The total number of outpatient and inpatient cases in each SRT system was evaluated annually. Results: From April 2014 to March 2022, the study included 212,016 cases (102,691 GKS and 109,325 LINAC) of the registered 1,996,540 radiotherapy cases. In the first year, 13,117 (54.1%) cases were GKS, and 11,128 (45.9%) were LINAC; after that, GKS decreased, and LINAC increased, reaching the same rate in FY2017. Compared to the first year, the final year showed 11,702 GKS (− 1415 or − 10.8%) and 17,169 LINAC (+ 6041 or + 54.3%), with an increase of 4626 total SRT cases to 28,871 (+ 19.1%). The percentage of outpatient treatment also increased from 4.6 to 11.8% for GKS and from 44.7 to 57.9% for LINAC. Conclusion: The study found a gradual decrease in the selection of GKS, an increasing trend in the selection of LINAC, and an increase in the overall number of stereotactic irradiations. In particular, the proportion of outpatient treatment increased, indicating that more than half of LINAC was selected for outpatient treatment. [ABSTRACT FROM AUTHOR]

This work presents an ecological, flexible 2D radiochromic dosimeter for measuring ionizing radiation in the kilogray dose range. Cotton woven fabric made of cellulose was volume-modified with nitrotetrazolium blue chloride as a radiation-sensitive compound. Its features include a color change during exposure from yellowish to purple-brown and flexibility that allows it to adapt to various shapes. It was found that (i) the dose response is up to ~80 kGy, (ii) it is independent of the dose rate for 1.1–73.1 kGy/min, (iii) it can be measured in 2D using a flatbed scanner, (iv) the acquired images can be filtered using a mean filter, which improves its dose resolution, (v) the dose resolution is −0.07 to −0.4 kGy for ~0.6 to ~75.7 kGy for filtered images, and (vi) two linear dose subranges can be distinguished: ~0.6 to ~7.6 kGy and ~9.9 to ~62.0 kGy. The dosimeter combined with flatbed scanner reading and data processing using dedicated software packages constitutes a comprehensive system for measuring dose distributions for objects with complex shapes. [ABSTRACT FROM AUTHOR]

Radiotherapy (or radiation therapy) uses ionizing radiation to selectively kill cancer cells, especially for solid tumours. Like surgery, it is meant to be a 'local' treatment, although its beneficial systemic (abscopal) effects are being discovered. It is most commonly used in addition to surgery (adjuvant, e.g. breast), but its role in the neoadjuvant setting in combination with chemotherapy for some cancers (e.g. rectum) is also established. In early stages of some cancers, it can be the definitive treatment, avoiding surgery and enabling organ preservation (e.g. larynx), while in late stages, it can provide excellent palliation (e.g. bone metastasis). Radiotherapy can be delivered at various energy levels (kiloVolts, megaVolts), with various subatomic particles (e.g. electrons, protons, and high-energy electromagnetic radiation). The traditional bulky equipment (e.g. linear accelerator) needs to be housed in an underground bunker and complex imaging improves precision and reduces radiation to normal tissues. Fractionated regimens spanning several days reduce individual doses. Radiotherapy during surgery achieves the highest precision and immediacy (e.g. TARGIT-IORT for breast cancer) and is proven to reduce deaths by avoiding scattered irradiation to vital organs (e.g. heart or lungs). [ABSTRACT FROM AUTHOR]

This study evaluated the usability of conventional templates based on the new contour guidelines of the European Society of Radiation and Oncology and Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) for treatment plans of postmastectomy radiotherapy after immediate implant-based reconstruction. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans generated with two different treatment planning systems (TPSs, Eclipse and Monaco) were examined. Six computed tomography scans of patients aged 35–54 years were retrospectively analysed who had undergone mastectomy and breast reconstruction using silicone implants after being diagnosed with left breast cancer. Six radiation oncologists participated in this study, and each of them contoured the target volume of one left breast using conventional contour (CTV-CONV) and new contour (CTV-ESTRO) methods. This study showed that compared with CTV-CONV, using CTV-ESTRO with objectives and cost functions similar to those of TPSs worsened the target volume coverage and increased the total number of monitor units. Considering the organs at risk, CTV-ESTRO tended to increase the mean dose delivered to the contralateral lung. It is concluded that the approach used for the new ESTRO-ACROP contour method cannot be applied in a manner similar to that for the conventional breast contour method, implying that the new ESTRO-ACROP contour method may require more time for improving plans for a given treatment. [ABSTRACT FROM AUTHOR]

Current online adaptive radiotherapy (oART) workflows require dedicated equipment. Our aim was to develop and implement an oART workflow for a C-arm linac which can be performed using standard clinically available tools. A workflow was successfully developed and implemented. Three patients receiving palliative radiotherapy for bladder cancer were treated, with 33 of 35 total fractions being delivered with the cone-beam computed tomography (CBCT)-guided oART workflow. Average oART fraction duration was 24 min from start of CBCT acquisition to end of beam on. This work shows how oART could be performed without dedicated equipment, broadening oART availability for application at existing treatment machines.

Abstract Background Monte Carlo simulation of radiation transport for medical linear accelerators (linacs) requires accurate knowledge of the geometrical description of the linac head. Since the geometry of Varian TrueBeam machines has not been disclosed, the manufacturer distributes phase-space files of the linac patient-independent part to allow researchers to compute absorbed dose distributions using the Monte Carlo method. This approach limits the possibility of achieving an arbitrarily small statistical uncertainty. This work investigates the use of the geometry of the Varian Clinac 2100, which is included in the Monte Carlo system PRIMO, as a surrogate. Methods Energy, radial and angular distributions extracted from the TrueBeam phase space files published by the manufacturer and from phase spaces tallied with PRIMO for the Clinac 2100 were compared for the 6, 8, 10 and 15 MV flattened-filtered beams. Dose distributions in water computed for the two sets of PSFs were compared with the Varian Representative Beam Data (RBD) for square fields with sides ranging from 3 to 30 cm. Output factors were calculated for square fields with sides ranging from 2 to 40 cm. Results Excellent agreement with the RBD was obtained for the simulations that employed the phase spaces distributed by Varian as well as for those that used the surrogate geometry, reaching in both cases Gamma ( $$2\%$$ 2 % , 2 mm) pass rates larger than $$99\%$$ 99 % , except for the 15 MV surrogate. This result supports previous investigations that suggest a change in the material composition of the TrueBeam 15 MV flattening filter. In order to get the said agreement, PRIMO simulations were run using enlarged transport parameters to compensate the discrepancies between the actual and surrogate geometries. Conclusions This work sustains the claim that the simulation of the 6, 8 and 10 MV flattening-filtered beams of the TrueBeam linac can be performed using the Clinac 2100 model of PRIMO without significant loss of accuracy.

Abstract Objective We developed rapid arc (RA) and intensity‐modulated radiotherapy (IMRT) plans based on the American Association of Physicists in Medicine Task Group‐119 (AAPM TG‐119) proposals and compared the planning and quality assurance results. Materials and Methods Two treatment plans were used for each study patient: one using 7–9 IMRT fields and the other using the two full‐arc RA methods. Plan optimization and dose calculations were performed using 6 MV photons and EclipseTM with the anisotropic analytical algorithm (AAA). Task group (TG)‐119 described the planning objectives used to evaluate the treatment plans generated for this study. Point dose, planar fluence measurement, and trajectory log file analysis are used for quality assurance. Results The conformity index (CI) for treatment plans varied between 0.76–0.91 when using IMRT and 0.75–0.93 when using RA. The homogeneity index (HI) was approximately 0.10–0.24 (IMRT) and 0.07–0.23 (RA). The ratio of the total number of monitor units required for IMRT to that required for RA was between 0.87 and 2.14. The treatment log files exhibited higher gamma passing with RA than with IMRT. Conclusion RA plans were more effective than IMRT plans in achieving the test goals. Point dose measurements and electronic portal imaging device (EPID)‐based planar fluence measurements showed statistically insignificant differences between the IMRT and RA plan quality assurance (QA) results. However, the trajectory log file analysis exhibited better gamma‐passing results for RA than for IMRT.

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Purpose: Medical linear accelerators are the most costly standard equipment used in radiation oncology, however the service costs for these machines are not well understood. With an increasing demand for linear accelerators due to a global increase in cancer incidence, it is important to understand the expected maintenance costs of a larger global installed base so that these costs can be incorporated into budgeting. The purpose of this investigation is to analyze the costs for medical linear accelerator service and maintenance at our institution, in order to estimate the service cost ratio. Methods: We collected the costs of parts used for all service work done on 32 medical linear accelerators over a two year period. The data was segregated by center, machine, linear accelerator type, and failure area in the machine. Results: We found the service cost ratio (excluding software support expenses) to be 3.13% [2.74%, 3.52%,]. We observed a variability of parts costs, and overall variability of the service cost ratio to be between 2.14% and 5.25%. This result is lower than other estimates for service costs for medical equipment in general and medical linear accelerators specifically. Two‐thirds of the service costs were due to labor costs, which indicate the importance of a well‐trained service technician workforce. Conclusions: We estimated the service cost ratio for medical linear accelerators to be 3.13% [3.52%, 2.74%] of the initial capital cost. This result was lower than other estimates of the service cost ratio. [ABSTRACT FROM AUTHOR]

Purpose: Radiotherapy delivered at ultra‐high‐dose‐rates (≥40 Gy/s), that is, FLASH, has the potential to effectively widen the therapeutic window and considerably improve the care of cancer patients. The underlying mechanism of the FLASH effect is not well understood, and commercial systems capable of delivering such dose rates are scarce. The purpose of this study was to perform the initial acceptance and commissioning tests of an electron FLASH research product for preclinical studies. Methods: A linear accelerator (Clinac 23EX) was modified to include a non‐clinical FLASH research extension (the Clinac‐FLEX system) by Varian, a Siemens Healthineers company (Palo Alto, CA) capable of delivering a 16 MeV electron beam with FLASH and conventional dose rates. The acceptance, commissioning, and dosimetric characterization of the FLEX system was performed using radiochromic film, optically stimulated luminescent dosimeters, and a plane‐parallel ionization chamber. A radiation survey was conducted for which the shielding of the pre‐existing vault was deemed sufficient. Results: The Clinac‐FLEX system is capable of delivering a 16 MeV electron FLASH beam of approximately 1 Gy/pulse at isocenter and reached a maximum dose rate >3.8 Gy/pulse near the upper accessory mount on the linac gantry. The percent depth dose curves of the 16 MeV FLASH and conventional modes for the 10 × 10 cm2 applicator agreed within 0.5 mm at a range of 50% of the maximum dose. Their respective profiles agreed well in terms of flatness but deviated for field sizes >10 × 10 cm2. The output stability of the FLASH system exhibited a dose deviation of <1%. Preliminary cell studies showed that the FLASH dose rate (180 Gy/s) had much less impact on the cell morphology of 76N breast normal cells compared to the non‐FLASH dose rate (18 Gy/s), which induced large‐size cells. Conclusion: Our studies characterized the non‐clinical Clinac‐FLEX system as a viable solution to conduct FLASH research that could substantially increase access to ultra‐high‐dose‐rate capabilities for scientists. [ABSTRACT FROM AUTHOR]

Background: Monte Carlo simulation of radiation transport for medical linear accelerators (linacs) requires accurate knowledge of the geometrical description of the linac head. Since the geometry of Varian TrueBeam machines has not been disclosed, the manufacturer distributes phase-space files of the linac patient-independent part to allow researchers to compute absorbed dose distributions using the Monte Carlo method. This approach limits the possibility of achieving an arbitrarily small statistical uncertainty. This work investigates the use of the geometry of the Varian Clinac 2100, which is included in the Monte Carlo system PRIMO, as a surrogate. Methods: Energy, radial and angular distributions extracted from the TrueBeam phase space files published by the manufacturer and from phase spaces tallied with PRIMO for the Clinac 2100 were compared for the 6, 8, 10 and 15 MV flattened-filtered beams. Dose distributions in water computed for the two sets of PSFs were compared with the Varian Representative Beam Data (RBD) for square fields with sides ranging from 3 to 30 cm. Output factors were calculated for square fields with sides ranging from 2 to 40 cm. Results: Excellent agreement with the RBD was obtained for the simulations that employed the phase spaces distributed by Varian as well as for those that used the surrogate geometry, reaching in both cases Gamma ( 2 % , 2 mm) pass rates larger than 99 % , except for the 15 MV surrogate. This result supports previous investigations that suggest a change in the material composition of the TrueBeam 15 MV flattening filter. In order to get the said agreement, PRIMO simulations were run using enlarged transport parameters to compensate the discrepancies between the actual and surrogate geometries. Conclusions: This work sustains the claim that the simulation of the 6, 8 and 10 MV flattening-filtered beams of the TrueBeam linac can be performed using the Clinac 2100 model of PRIMO without significant loss of accuracy. [ABSTRACT FROM AUTHOR]

Introduction: Popularly, teletherapy (telecobalt/LA) equipment is based on a C-arm gantry system. Recently, a fast O-ring gantry system introduced a medical linear accelerator (LA) to smoothen the workflow of treatment of cancer patients because of the increasing trend of the number of cancer cases over the past few years. This study aimed to analyze the commissioning parameters and validation of the O-ring gantrybased LA for improved radiotherapy techniques. Material and Methods: Three-dimensional (3D) radiation field analyzer (RFA) used to commission Halcyon™ LA. It is used for measuring percent depth dose (PDD), profiles, and output factors. Results: TPS data was validated by comparing it with our measured data. Plans per the TG-119 protocol showed good agreement between treatment planning systems (TPS) calculated and measured doses. For patient-specific, QA plans showed good agreement with gamma evaluation criteria. Conclusion: Commissioning and validation of O-ring gantry system Halcyon™ LA was performed successfully. [ABSTRACT FROM AUTHOR]

At the Czech Technical University in Prague, we have installed virtual software environment simulating a radiotherapy treatment room with a medical linear accelerator (software VERT and VERT Physics by Vertual Ltd., United Kingdom). It is possible to simulate patient treatment and physics QA (quality assurance) measurements in virtual reality. This is beneficial for our students and teachers because there is no radiation present while doing the exercises and it is accessible at any time, unlike medical linear accelerators at hospitals. For our department, we have chosen the TrueBeam model by Varian Medical Systems, USA. The linear accelerator can be operated by the user in the same way as at the hospital, including the hardware pendant. There is a selection of patient treatment plans, CT images and RT structures, all of which can be visualised inside the treatment room, also during beam on, simulating the situation inside the patient while irradiating the tumour. Any DICOM files, even from another manufacturer's linac (linear accelerator) or treatment planning system, can be imported into VERT. Apart from this, there is also an imaging interface and cone-beam CT interface showing options for patient setup. Another part of the software is a physics module with various phantoms and detectors for dosimetry as well as geometry tests. For example, a large water tank can be used for relative dosimetry of photon beams (percent depth doses and profiles), a smaller water phantom can be used for reference dosimetry or chamber cross calibration according to the TRS 398 (1) or IPEM (2) protocol. The results of measurements are based on look-up tables coming from real beam data, so dependence on the depth of measurement, field size, temperature and pressure and other parameters can be demonstrated. Moreover, it is possible to introduce many types of errors into the linac, such as jaw position, laser, or collimator miscalibration, and show how these errors propagate to patient irradiation and how they can be detected by QA tools. This paper is a short report on how this system has been used at our university and how it might be used in modern learning, pointing out its advantages and drawbacks. At the 16th Workshop on European Collaboration in Higher Education on Radiological and Nuclear Engineering and Radiation Protection (CHERNE) it was proposed that this virtual system could be used for an international student training course on medical physics in radiotherapy within the CHERNE network. This course might contain theoretical lectures with demonstrations on the virtual linac, practical exercises on the virtual linac and visits to hospitals (a photon radiotherapy centre, the Thomayer University Hospital in particular, and a proton therapy centre). [ABSTRACT FROM AUTHOR]

Background: Radiation-induced changes (RICs) post-stereotactic radiosurgery (SRS) critically influence outcomes in arteriovenous malformation (AVM) treatments. This study aimed to identify predictors of RICs, described the types and severity of RICs, and assessed their impact on patient's functional outcomes to enhance risk assessment and treatment planning for AVM patients. Methods: This retrospective study analyzed 87 AVM patients who underwent SRS at Hospital Kuala Lumpur between January 2015 and December 2020. RICs were identified through detailed magnetic resonance imaging evaluations, and predictive factors were determined using multiple logistic regression. Functional outcomes were assessed with the modified Rankin scale (mRS). Results: Among the cohort, 40.2% developed RICs, with radiological RICs in 33.3%, symptomatic RICs in 5.7%, and permanent RICs in 1.1%. Severity categorization revealed 25.3% as Grade I, 13.8% as Grade II, and 1.1% as Grade III. Notably, higher Pollock-Flickinger scores and eloquence location were significant predictors of RIC occurrence. There was a significant improvement in functional outcomes post-SRS, with a marked decrease in non-favorable mRS scores from 8.0% pre-SRS to 1.1% post-SRS (P = 0.031). Conclusion: The study identified the eloquence location and Pollock-Flickinger scores as predictors of RICs post-SRS. The significant reduction in non-favorable mRS scores post-SRS underscores the efficacy of SRS in improving patient outcomes. Their results highlighted the importance of personalized treatment planning, focusing on precise strategies to optimize patient outcomes in AVM management, reducing adverse effects while improving functional outcomes. [ABSTRACT FROM AUTHOR]

Background: Frameless image-guided radiosurgery (IGRS) is an effective and non-invasive method of treating patients who are unresponsive to medical management for trigeminal neuralgia (TN). This study evaluated the use of frameless IGRS to treat patients with medically refractory TN. Methods: We performed a retrospective review of records of 116 patients diagnosed with TN who underwent frameless IGRS using a linear accelerator (LINAC) over 10 years (March 2012-February 2023). All patients had failed medical management for TN. Facial pain was graded using the Barrow Neurological Institute (BNI) scoring system. Each patient received a BNI score before frameless IGRS and following treatment. Failure was defined as a BNI score IV-V at the last follow-up and/or undergoing a salvage procedure following IGRS. Results: All patients had a BNI score of either IV or V before the frameless IGRS. The mean follow-up duration for all 116 patients following IGRS was 44.1 months. Most patients (81 [69.8%]) had not undergone surgery (microvascular decompression [MVD] or rhizotomy) or stereotactic radiosurgery (SRS) for TN before frameless IGRS. A total of 41 (35.3%) patients underwent a salvage procedure (MVD, rhizotomy, or an additional IGRS) following frameless IGRS. The mean duration between the initial frameless IGRS and salvage procedure was 20.1 months. At the last follow-up, a total of 110 (94.8%) patients had a BNI score of I-III. No complications were reported after the frameless IGRS. The BNI score at the last follow-up was lower compared to the initial BNI for patients regardless of prior intervention (P < 0.001). Patients who failed IGRS had a higher BNI score at the last follow-up compared to those who did not fail IGRS (2.8 vs. 2.5, P = 0.05). Patients with pain relief had a shorter follow-up compared to those with pain refractory to SRS (38.0 vs. 55.1, P = 0.005). Conclusion: In this large cohort of patients with medically refractory TN, frameless IGRS resulted in durable pain control in the majority of patients without any toxicity. [ABSTRACT FROM AUTHOR]

Objective: We developed rapid arc (RA) and intensity‐modulated radiotherapy (IMRT) plans based on the American Association of Physicists in Medicine Task Group‐119 (AAPM TG‐119) proposals and compared the planning and quality assurance results. Materials and Methods: Two treatment plans were used for each study patient: one using 7–9 IMRT fields and the other using the two full‐arc RA methods. Plan optimization and dose calculations were performed using 6 MV photons and EclipseTM with the anisotropic analytical algorithm (AAA). Task group (TG)‐119 described the planning objectives used to evaluate the treatment plans generated for this study. Point dose, planar fluence measurement, and trajectory log file analysis are used for quality assurance. Results: The conformity index (CI) for treatment plans varied between 0.76–0.91 when using IMRT and 0.75–0.93 when using RA. The homogeneity index (HI) was approximately 0.10–0.24 (IMRT) and 0.07–0.23 (RA). The ratio of the total number of monitor units required for IMRT to that required for RA was between 0.87 and 2.14. The treatment log files exhibited higher gamma passing with RA than with IMRT. Conclusion: RA plans were more effective than IMRT plans in achieving the test goals. Point dose measurements and electronic portal imaging device (EPID)‐based planar fluence measurements showed statistically insignificant differences between the IMRT and RA plan quality assurance (QA) results. However, the trajectory log file analysis exhibited better gamma‐passing results for RA than for IMRT. [ABSTRACT FROM AUTHOR]

Abstract Background Few dosimetric comparisons have been published between linear accelerator (LA)-based systems and CyberKnife (CK)-based robotic radiosurgery systems for cardiac radio-ablation in ventricular tachycardia. This study aimed to compare the dosimetry of noninvasive cardiac radio-ablation deliverable on LA with that on CK. Methods Thirteen patients who underwent noninvasive cardiac radio-ablation by LA were included. The prescribed dose was 25 Gy in 1 fraction, and the average planning target volume was 49.8 ± 31.0 cm3 (range, 14.4–93.7 cm3). CK plans were generated for comparison. Results Both the CK and LA plans accomplished appropriate dose coverage and normal tissue sparing. Compared with the LA plans, the CK plans achieved significantly lower gradient indices (3.12 ± 0.71 vs. 3.48 ± 0.55, p = 0.031) and gradient measures (1.00 ± 0.29 cm vs. 1.17 ± 0.29 cm, p 50 cm3 or a non-spherical PTV, the LA and CK plans were similar regarding dosimetric parameters. CK plans involved more beams (232.2 ± 110.8 beams vs. 10.0 ± 1.7 arcs) and longer treatment times (119.2 ± 43.3 min vs. 22.4 ± 1.6 min, p = 0.007). Conclusions Both CK and LA are ideal modalities for noninvasive cardiac radio-ablation. Upfront treatment should be considered based on clinical intent.

Abstract Objective The purpose of this study is to reveal the dose-effect relationship of linear accelerator (LINAC)-based stereotactic radiotherapy (SRT) in patients with brain metastases (BM). Materials and methods The PubMed, Cochrane, and Web of Science databases were used to identify studies that reported local tumour control after LINAC-based SRT in patients with BMs. Studies of other approaches that could affect local tumour control, such as whole brain radiotherapy, targeted therapy, and immunotherapy, were excluded from the dose-effect relationship analysis. Data extracted included patient and treatment characteristics and tumour local control. Probit model in XLSTAT 2016 was used for regression analysis, and P

The ANTHEM (Advanced Technologies for Human-centered Medicine) Radio-Frequency Quadrupole (RFQ) will employ eight coaxial power couplers, which will be magnetically coupled to the device through a loop antenna. The coupler design can support up to 140 kW in continuous wave operation. This paper presents the design of the cavity used for high-power testing, with the primary objectives of both optimizing the coupling between the couplers and ensuring operations at the designated operating frequency. Furthermore, the paper encompasses thermal and structural assessments conducted through numerical simulations.

Background: As compared to the flattened photon beam, removing the flattening filter (FF) from the head of a gantry decreases the average energy of the photon beam and increases the dose rate, leading to an impact on the quality of treatment plans. Objective: This study aimed to compare the quality of intensity-modulated radiation therapy (IMRT) treatment plans for esophageal cancer with and without a flattened filter photon beam. Material and Methods: In this analytical study, 12 patients, who had already been treated with a 6X FF photon beam, were treated based on new IMRT methods using a 6X the flattening filter-free (FFF) photon beam. Both 6X FF IMRT and 6X FFF IMRT plans used identical beam parameters and planning objectives. All plans were evaluated with planning indices and doses for organs at risk (OARs). Results: Insignificant dose variation was for HI, CI, D98%, and V95% between FF and FFF photon beam IMRT plans. FF-based IMRT plan delivered a 15.51% and 11.27% higher mean dose to both lungs and heart than the FFF plan, respectively. The integral dose (ID) for the heart and lungs was 11.21% and 15.51%, respectively, less in the IMRT plan with an FFF photon beam. Conclusion: In contrast to the FF photon beam, a filtered photon beam-oriented IMRT plan provides significant OAR sparing without losing the quality of the treatment plan. High monitor units (MUs), low ID, and Beam on Time (BOT) are major highlights of the IMRT plan with FFF beam.

This study quantitatively evaluated the source term of a linear accelerator according to target thickness for a 6-20 MeV electron beam using MCNP6. The elements of the target were tungsten and copper, and a composite target and single target were simulated by setting different thickness parameters depending on energy. The accumulation of energy generated through interaction with the collided target was evaluated at 0.1-mm intervals, and F6 tally was used. The results indicated that less than 3% reference error was maintained according to the MCNP recommendations. At 6, 8, 10, 15, 18, and 20 MeV, the energy accumulation peaks identified for each target were 0.3 mm in tungsten, 1.3 mm in copper, 1.5 mm in copper, 0.5 mm in tungsten, 0.5 mm in tungsten, and 0.5 mm in tungsten. For 8 and 10 MeV in a single target consisting only of copper, the movement of electrons was confirmed at the end of the target, and the proportion of escaped electrons was 0.00011% and 0.00181%, respectively.

Background: Few dosimetric comparisons have been published between linear accelerator (LA)-based systems and CyberKnife (CK)-based robotic radiosurgery systems for cardiac radio-ablation in ventricular tachycardia. This study aimed to compare the dosimetry of noninvasive cardiac radio-ablation deliverable on LA with that on CK. Methods: Thirteen patients who underwent noninvasive cardiac radio-ablation by LA were included. The prescribed dose was 25 Gy in 1 fraction, and the average planning target volume was 49.8 ± 31.0 cm3 (range, 14.4–93.7 cm3). CK plans were generated for comparison. Results: Both the CK and LA plans accomplished appropriate dose coverage and normal tissue sparing. Compared with the LA plans, the CK plans achieved significantly lower gradient indices (3.12 ± 0.71 vs. 3.48 ± 0.55, p = 0.031) and gradient measures (1.00 ± 0.29 cm vs. 1.17 ± 0.29 cm, p < 0.001). They had similar equivalent conformity indices (CK vs. LA: 0.84 ± 0.08 vs. 0.87 ± 0.07, p = 0.093) and maximum doses 2 cm from the planning target volume (PTV) in any direction (CK vs. LA: 50.8 ± 9.9% vs. 53.1 ± 5.3%, p = 0.423). The dosimetric advantages of CK were more prominent in patients with a PTV of ≤ 50 cm3 or a spherical PTV. In patients with a PTV of > 50 cm3 or a non-spherical PTV, the LA and CK plans were similar regarding dosimetric parameters. CK plans involved more beams (232.2 ± 110.8 beams vs. 10.0 ± 1.7 arcs) and longer treatment times (119.2 ± 43.3 min vs. 22.4 ± 1.6 min, p = 0.007). Conclusions: Both CK and LA are ideal modalities for noninvasive cardiac radio-ablation. Upfront treatment should be considered based on clinical intent. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study is to reveal the dose-effect relationship of linear accelerator (LINAC)-based stereotactic radiotherapy (SRT) in patients with brain metastases (BM). Materials and methods: The PubMed, Cochrane, and Web of Science databases were used to identify studies that reported local tumour control after LINAC-based SRT in patients with BMs. Studies of other approaches that could affect local tumour control, such as whole brain radiotherapy, targeted therapy, and immunotherapy, were excluded from the dose-effect relationship analysis. Data extracted included patient and treatment characteristics and tumour local control. Probit model in XLSTAT 2016 was used for regression analysis, and P < 0.05 was set as the statistically significant level. Results: After literature screening, 19 eligible studies involving 1523 patients were included in the probit model regression analysis. There was no significant dose-effect relationship between nominal BED10 and peripheral BED10 versus 12-month local control probability. There were significant dose effect relationships between the centre BED10 and the average BED10 versus the 12-month local control probability, with P values of 0.015 and 0.011, respectively. According to the model, the central BED10 and the average BED10 corresponding to probabilities of 90% 12-month local control were 109.2 GyBED10 (95% confidence interval (CI): 88.7–245.9 GyBED10) and 87.8 GyBED10 (95% CI: 74.3–161.5 GyBED10), respectively. A 12-month local control rate of 86.9% (95% CI: 81.7–89.7%) and 85.5% (95% CI: 81.2–89.2%) can be expected at a centre BED10 of 80 Gy and an average BED10 of 60 Gy, respectively. Conclusion: For patients with BM treated with LINAC-based SRT, more attention should be given to the central and average doses of PTV. A clear definition of the dose prescription should be established to ensure the effectiveness and comparability of treatment. [ABSTRACT FROM AUTHOR]

We studied the correlation between new-onset perinidal hyperintensity (PH) on T2-weighted magnetic resonance imaging and obliteration of intracranial arteriovenous malformation (AVM) after stereotactic radiosurgery (SRS). A retrospective study of 148 patients with an intracranial AVM who underwent SRS between September 2005 and June 2018 and had ≥1 radiological follow-up (early magnetic resonance imaging) 12–18 months after SRS was performed to analyze the correlation between PH (graded from 0 to 2) and AVM obliteration. Of the 148 patients, 95 were male. The mean patient age was 27.7 ± 12.4 years. Of the 148 AVMs, 105 (70.9%) were obliterated at a median follow-up of 27 months (interquartile range, 14–48 months). The cumulative 3-, 5-, 10-year obliteration rate was 51.8%, 70.8%, and 91.8%, respectively. New-onset PH was observed in 58 AVMs (39.2%; 50 obliterated and 8 not obliterated). No association was found between the pretreatment variables or dose delivered and the development of PH. Grade 2 PH was associated with the risk of symptoms developing compared with grade 1 PH (37.5% vs. 4%; P = 0.002). Symptomatic PH was more likely to develop in patients with a larger AVM (P = 0.05). On multivariate analysis, the presence of a single draining vein (odds ratio [OR], 2.9; 95% confidence interval [CI], 1.3–6.8), a lower median AVM volume (OR, 0.97; 95% CI, 0.6–0.89), a mean marginal radiation dose (OR, 1.29; 95% CI, 1.02–1.64), and the presence of PH (OR, 3.16; 95% CI, 1.29–7.71) were independent predictors of AVM obliteration. The incidence of PH after SRS for AVM was 39.2%. PH was an independent predictor of AVM obliteration after SRS. Grade 2 PH and a larger AVM volume were associated with symptomatic PH. [ABSTRACT FROM AUTHOR]

Purpose This study aimed to perform a longitudinal analysis of linear accelerator (linac) technical faults reported with a cloud-based Machine Log system in use in a busy academic clinic and derive operational insights related to linac reliability, clinical utilization, and performance. Methods We queried the Machine Log system for the following parameters: linac type, number of reported technical faults, types of fault, number of faults where the linac was disabled, and estimated clinical downtime. The number of fractions treated and monitor units (MU) delivered were obtained from the record and verify system as metrics of linac utilization and to normalize the number of reported linac faults, facilitating inter-comparison. Two Varian TrueBeam C-arm linacs (Varian Medical Systems, Palo Alto, CA), one Varian 21iX C-arm linac (Varian Medical Systems, Palo Alto, CA), and one newly installed Varian Halcyon ring gantry linac (Varian Medical Systems, Palo Alto, CA) were evaluated. The linacs were studied over a 30-month period from September 2017 to March 2020.  Results Over 30 months, comprising 677 clinical days, 1234 faults were reported from all linacs, including 153 "linac down" events requiring rescheduling or cancellation of treatments. The TrueBeam linacs reported nearly twice as many imaging, multileaf collimator (MLC), and beam generation faults per fraction, and MU as the Halcyon. Halcyon experienced fewer beam generation/steering, accessory, and cooling-related faults than the other linacs but reported more computer and networking issues. Although it employs a relatively new MLC design compared to the C-arm linacs and delivers primarily intensity-modulated treatments, Halcyon reported fewer MLC faults than the other linacs. The 21iX linac had the fewest software-related faults but was subject to the most cooling-related faults, which we attributed to extensive use of this linac for treatment techniques with extended beam-on times. Conclusions A longitudinal analysis of a cloud-based Machine Log system yielded operational insights into the utilization, performance, and technical reliability of the linacs in use at our institution. Several trends in linac sub-system reliability were identified and could be attributed to either age, design, clinical use, or operational demands. The results of this analysis will be used as a basis for designing linac quality assurance schedules that reflect actual linac usage and observed sub-system reliability. Such a practice may contribute to a clinic workflow subject to fewer disruptions from linac faults, ultimately improving efficiency and patient safety.