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@#<b>Objective</b> To investigate the quality control and protection level of medical electron linear accelerators in Shanghai, China. <b>Methods</b> The startified random sampling method was used to cover tertiary, secondary and ungraded hospitals, and a total of 30 medical electron linear accelerators in 15 hospitals were tested for quality control and protection level according to relevant standards. <b>Results</b> Five medical electron linear accelerators failed the quality control test, with an overall inspection pass rate of 83.3% and a re-inspection pass rate of 100%. The pass rate of flatness of square X-ray irradiation field (5 cm × 5 cm)-(30 cm × 30 cm) was 83.3%, the pass rate of symmetry of square X-ray irradiation field was 96.7%, and other indices were qualified. All medical electron linear accelerator rooms passed the protection test. <b>Conclusion</b> The protection of medical electron linear accelerator rooms in Shanghai meets the requirements of national standards, and some indices do not meet the requirements of national standards in the preliminary inspection. The quality control of medical electron linear accelerators should be further strengthened to ensure the treatment effect of patients.
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@#Multi-leaf collimators are devices to block rays from medical linear accelerators, which directly affect doses to targets and organs at risk by adjusting field shape and dose distribution in radiation therapy. As multi-leaf collimators are diversified in structure, there has been growing research on dosimetric comparison of various multi-leaf collimators. In this paper, we introduced the classifications of multi-leaf collimators according to their basic components, as well as the hardware structure and design features of the products of main accelerator manufacturers, including Varian’s Millennium MLC, HD120 MLC, and Halcyon, Elekta’s MLCi/i2 and Agility, and Accuray’s InCise 2 MLC and TomoTherapy. In terms of clinical application evaluation, focusing on radiotherapy plans for nasopharyngeal carcinoma, we reviewed comparative studies on the dosimetry performance of multi-leaf collimators and the effects of relevant parameters on dose distribution. We hope this review on the design and application evaluation of multi-leaf collimators can provide a reference for more innovative design and accelerator selection and parameter setting in clinical individualized treatment.
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Objective To investigate the awareness of the Radiation Shielding Requirements for Radiotherapy Room–Part 2: Radiotherapy Room of Electron Linear Accelerators (GBZ/T 201.2—2011) among relevant practitioners in medical institutions as well as its implementation and application situation and collect relevant problems and suggestions for an evaluation of the scientificalness, standardization, and timeliness of the standard, and to provide a scientific basis for the further revision and implementation of the standard. Methods An online questionnaire survey was conducted among relevant employees in medical institutions providing medical linear accelerator radiotherapy across 22 provinces of China, which investigated the awareness, training, application, and revision suggestions related to GBZ/T 201.2—2011. The questionnaires were collected and analyzed. Results A total of 340 relevant practitioners filled out the questionnaire. Of the participants, 66.80% were physicists; 79.11% had an awareness of the standard; 56.18% ever participated in the standard-related training; but the survey results showed that the practitioners did not have a good knowledge of the standard’s content, and the training and promotion were not enough; 83.24% thought that the standard had been widely used; 17.60% thought that the standard needed to be revised; 76.76% thought that there was a need to add calculation examples; 88.82% thought that neutron shielding needed to be considered for the 10 MV X-ray accelerator room. Conclusion The standard has been widely known in the field of radiotherapy protection. With the development of radiotherapy technology, the standard should be revised to add calculation examples and consider neutron shielding in the 10 MV X-ray accelerator room. The standard is highly technical and difficult to grasp, so the promotion and implementation goals should be appropriate for different personnel groups, the training for employees at key posts should be strengthened, and the methods recommended in the standard should be uniformly used throughout the country.
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Magnetic resonance-guided radiotherapy (MRgRT) not only offers real time magnetic resonance (MR) imags with high-resolution and good soft tissue contrast to guide the delineation of the target volume during simulation and daily radiotherapy, but also reveals the position and shape changes of the target volumes and organs at risk (OAR) during treatment dynamically, which provides the evidence for the individual-adptive planning revision. Thus, MRgRT has the potential to dramatically impact cancer research and treatment. And this treatment mode is theoretically more suitable for the disease with obvious tissue deformation, such as breast. In this review, application of MR scanner with a linear accelerator (MR-linac) in radiotherapy workflows for breast cancer patients was summarized, and its implications and opportunities on breast cancer irradiation were highlighted.
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Objective:To improve the quality assurance (QA) skills of radiotherapy personnel and medical students and reduce the radiation risk of training by developing a remote training system for QA of medical electronic linear accelerators.Methods:This training system was built based on radiotherapy technology and quality control contents of medical electronic linear accelerators, and a virtual reality interactive software was developed using extended reality (XR) technology Unity 3D. A remote control module of multi-terminal platform was also developed. A multi-perspective evaluation system was adopted and a questionnaire was designed to analyze the application value of this system.Results:The training system reproduced the live environment and physical objects of medical electronic linear accelerator treatment room. It built a multi-terminal virtual simulation training system with radiotherapy technology as well as QA knowledge system. This system could provide 5G remote control of medical electronic linear accelerator for off-site quality control demonstration and guidance. By March 1, 2022, a total number of 133 people had been trained using this system, 76 valid questionnaires had been taken, of which 90.79% (69/76) of the respondents trusted the experimental results shown by the system and 88.16% (67/76) of the respondents considered the training system necessary.Conclusions:The training effect of this system is widely recognized. It fundamentally reduces the training radiation hazard and provides reference for the reform and progress of QA training mode of medical electronic linear accelerators.
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Radiation absorbed doses to organs outside the radiation therapy treatment beam can be significant and therefore of clinical interest. Two sets of out-of-beam measurements were performed measuring the leak dose and the scattered dose, at 5 points within the accelerator components (accelerator tube and collimator) and at 21 points on the equipment and surroundings based on a positioning scheme. For this purpose, 52 Optically Stimulated Luminescence (OSL) dosimeters were used in a latest generation helical linear accelerator. Of the 200 cGy fired at a cheese-like phantom, 0.332% of the out-of-beam dose contribution was found to come from the leak and 0.784% was transformed into scattering. For these dose values, estimates of the risk of second tumors in long-term survivors indicate a reduced probability of acquiring a second secondary radiation malignancy, based on information from the 1990 BEIR Committee report.
La dosis absorbida de radiación a órganos fuera del haz de tratamiento de radioterapia puede ser significativa y, por lo tanto, de interés clínico. Se realizaron dos sets de mediciones fuera del haz para determinar la dosis de fuga y la dosis dispersa, en 5 puntos dentro de los componentes del acelerador (tubo de aceleración y colimador) y 21 puntos en el equipo y alrededores basado en un esquema de posicionamiento. Para este fin se utilizaron 52 dosímetros de luminiscencia estimulada ópticamente (OSL, Optically Stimulated Luminescence), en un acelerador lineal helicoidal de última generación. De los 200 cGy disparados a un maniquí tipo queso, se encontró que el 0.332% de la contribución de dosis fuera del haz provenía de la fuga y 0.784% se transforma en dispersión. Para estos valores de dosis, las estimaciones del riesgo de segundos tumores en los supervivientes a largo plazo indican una reducida probabilidad de contraer una segunda malignidad por radiación secundaria, según la información del informe del Comité BEIR de 1990.
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Humans , Radiotherapy Planning, Computer-Assisted/methods , Radiotherapy, Intensity-Modulated/methods , Optically Stimulated Luminescence Dosimetry , Radiometry/instrumentation , Thermoluminescent Dosimetry , Calibration , Luminescence , Luminescent MeasurementsABSTRACT
In this article, a case for random signal interference in resolver (or encoder) of carousel on Varian VitalBeam medical linear accelerator was illustrated. This case was considered as a rare failure of the technology platform (including TrueBeam) by Chinese, European and American technical experts in Varian. In this article, the differences of the carousel in the structure and control system between VitalBeam and traditional accelerator were comparatively analyzed to enable the peers to have a deeper understanding of resolver. The logic and methods to solve the fault were summarized, providing reference experience for analyzing the problems related to carousel. It is found that the interlocking system is imperfect, which provides a factual and technological basis for Varian to optimize the system.
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Objective To analyze the room layout and shielding of three types of self-shielded accelerators, and to provide a basis for optimizing the shielding design of rooms for self-shielded accelerators. Methods We compared the radiation shielding levels (transmitted radiation dose rate outside the primary barrier and scattered radiation dose rate outside the secondary barrier) of three self-shielded accelerator rooms by Monte Carlo simulation and empirical formula calculation. Results According to Monte Carlo simulation and empirical formula calculation, for the Unity MR Linac accelerator, the scatter radiation dose rate outside the secondary barrier was significantly higher (up to five times) than the transmitted primary radiation dose rate outside the primary barrier. The scatter radiation dose rate of the cross section was significantly higher than that of the sagittal section for both Unity MR Linac and TOMO accelerators. Conclusion The differences in the shape, material, and thickness of self-shielding structures complicate the shielding calculation and design for accelerator rooms. The shielding calculation method should be improved to optimize the radiation shielding of novel accelerator rooms.
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@#<b>Objective</b> To investigate the current situation of quality control in medical linear accelerators in Hebei Province, China. <b>Methods</b> The main performance indices of some medical linear accelerators in Hebei Province, 2019—2021 were tested according to the current relevant effective standards GB 15213—2016 <i>Medical Electron Accelerators-Functional Performance Characteristics and Test Methods</i> and WS 674—2020 <i>Specification for Testing of Quality Control in Medical Linear Accelerator</i>. <b>Results</b> A total of 175 medical linear accelerators were tested from 2019 to 2021, and the annual pass rates were 72.4% in 2019, 75.9% in 2020, and 79.4% in 2021. The overall pass rate of initial inspection was 76.0%, and the pass rate of reinspection was 100.0%. The index with the lowest pass rate in the initial inspection was square X radiation field uniformity, followed by dose deviation and square X radiation field symmetry. <b>Conclusion</b> Medical institutions should strengthen quality control management, conduct regular testing of medical linear accelerators, and timely correct dose deviation, so as to ensure the treatment effect of patients.
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@#Abstract: Objective To evaluate the key quality control and protective performance test of Halcyon medical linear accelerator. Methods WS 674-2020Specification for Testing of Quality Control in Medical Linear Accelerator（ According to the hereinafter WS 674-2020） ， referred to and the manufacturer´s manual the performance of the first Halcyon medical linear accelerator in Results ， ， Hunan Province was tested. The results showed that all ten indicators of the accelerator including dose deviation ， ， （ ， ， ， - repeatability linearity daily stability and symmetry the results were 0.10% 0.03% 0.04% 0.50% and 100.50% 100.80% ）， - - respectively met the requirements of WS 674 2020. The results of manufacturer quality control indicators such as dose rate ， ， stability in beam gantry rotation isocenter and mechanical position accuracy megavolt image parameters and cone beam computer tomography image parameters met the requirements of the manufacturer´s regulations. Due to the special structure and ， - ： function of the accelerator it is difficult to detect the parameter required by WS 674 2020 as below the radiation leakage - ， ， ， ， outside the M zone the uniformity the indicators related to the light field the offset of the radiation beam axis the zero scale Conclusion - position of the rotating motion scale and others. It is difficult to carry out complete testing according to WS 6742020 for Halcyon medical linear accelerator and it is urgent for the state to issue relevant testing standards to standardize and strengthen the quality control testing of various accelerators.
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Objective:To build an evaluation index system for linac stability and establish a scientific, systematic and objective evaluation standard for the stability of linac equipment.Methods:Based on the Delphi and AHP methods, a three-level index system for the stability of linac equipment was established, and the correlation coefficients and weights were calculated using Microsoft Excel 2007 and SPSS 16.0.Results:The enthusiasm of experts in two rounds was 85%(17/20) and 92%(23/25), the authority coefficients were 0.79 and 0.87, and the expert Kendall coordination coefficients were 0.957(first-level index, P<0.05), 0.637(second-level index, P<0.05) and 0.527(third-level index, P<0.05), respectively. Finally, a three-level index system covering 2 first-level indicators of mechanical treatment system and accessory system, 9 second-level indicators and 32 third-level indicators was established. The CVs of all levels of indicators were less than 0.25 and passed the consistency test. Conclusion:The evaluation index system for linac equipment stability has good scientificity, operability and versatility, which can provide theoretical and quantitative reference for linac stability evaluation and equipment purchase.
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Objective:To compare dose distributions of hypofractionated radiotherapy for pancreatic cancer between IMPT and VMAT.Methods:Ten pancreatic cancer cases were included in this retrospective study. Photon (Edge) and proton (Proteus?PLUS) plans were designed by Eclipse and RayStation TPS, respectively. All plans were transferred to MIM system for extraction of parameters, which included Dmin, Dmean and Dmax of PTV, conformity index (CI), new conformity index (nCI), homogeneity index (HI), gradient index (GI), coverage, Dmax and dose-volume of the organs at risk (OARs). Results:There was no significant difference in CI between the two groups. The higher PTV Dmin, Dmean, Dmax, D98%, D2%, HI, coverage and the better GI, D2 cmwere found in VMAT ( t/ Z=-4.63-5.32, P<0.05). The lower 10%_PD was found in IMPT ( t=-7.47, P<0.05). Regarding the OARs, Dmax of the intestine, stomach, and duodenum and Dmean of the left kidney were similar between two groups without significant difference ( P>0.05). The D5 cm 3 of the intestine, D10 cm 3 of the stomach, D5 cm 3 and D10 cm 3 of the duodenum, D2/3 of the left kidney, Dmean and D2/3 of the right kidney were lower in IMPT than those in VMAT ( t/ Z=-8.12--2.60, P<0.05). However, the Dmax and D0.35 cm 3 of the spinal cord were higher in IMPT than those in VMAT ( t=7.30, 6.77, P<0.05). Conclusions:Both of hypofractionated radiotherapy plans of pancreatic cancer designed by VMAT and IMPT could meet clinical needs. No significant difference was found in Dmax of the adjacent gastrointestinal tracts between the two groups. While IMPT had the advantage over VMAT in the case of lower dose-volumes of the gastrointestinal tracts. Nevertheless, less protections of the OARs in front of the tumor volume could be provided by IMPT compared with VMAT.
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Objective:To explore the setup errors of vacuum pad combined with breast bracket in linear accelerator intensity-modulated radiotherapy for breast cancer.Methods:The clinical data of 72 patients who received linear accelerator intensity-modulated radiotherapy after breast conserving surgery in Hai'an Hospital of Traditional Chinese Medicine from July 2017 to March 2022 were retrospectively analyzed. According to the radiotherapy fixation schemes, they were divided into vacuum pad group (24 patients), breast bracket group (27 patients) and vacuum pad combined with breast bracket group (21 patients). Cone-beam CT was used to analyze the setup errors of the fixation, and the mean value of the overall errors and the standard deviation of the system errors were calculated. The relative factors affecting the fixed setup errors were analyzed.Results:There were statistical differences among vacuum pad group, breast bracket group and vacuum pad combined with breast bracket group in the level of forward and backward (Z) direction translation error (2.11±0.41, 2.67±0.26 and 1.79±0.21) and Z direction rotation error (1.14±0.24, 1.05±0.21 and 0.91±0.22) ( F values were 45.86 and 6.21, both P < 0.05). The level of Z direction translation error in vacuum pad group was higher than that in vacuum pad combined with breast bracket group, and the difference was statistically significant ( t = 12.37, P = 0.001). The level of Z direction rotation error in breast bracket group was higher than that in vacuum pad combined with breast bracket group, and the difference was statistically significant ( t = 3.41, P = 0.001). In the breast bracket group, the planning target volume (PTV) extension boundary values in the left and right (X), up and down (Y), and Z directions were 2.02, 2.09 and 1.97; the PTV release boundary values in X, Y and Z directions of the vacuum pad group were 1.81, 2.07 and 2.25; the external boundary values of PTV in X, Y and Z directions of the vacuum pad combined with breast bracket group were 1.13, 1.51 and 1.49. The result of multifactor analysis showed that body mass index (BMI) ( OR = 4.208, 95% CI 1.438-12.312) and breast volume ( OR = 4.023, 95% CI 1.375-11.769) were the independent influencing factors of fixed setup errors (both P < 0.05). Conclusions:The application of vacuum pad combined with breast bracket in the fixed setup of linear accelerator intensity-modulated radiotherapy of breast cancer is helpful to reduce the fixed setup errors, but at the same time, the fixed setup errors is affected by the patient's BMI, breast volume and other factors.
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Objective To understand the level of quality control in medical linear accelerator in Guangxi, and to provide technical support for the health administrative department to make related standards. Methods To select medical linear accelerators in Guangxi by random sampling method. Results A total of 118 accelerators were checked in 2017—2019, the initial inspection pass rates of medical linear accelerators were 56.8% and re-inspect pass rate were 96.6%. Conclusion The quality control level of the radiology institutions needs to be improved. The health administrative department should strengthen routine management，it is necessary to implement quality control in medical linear accelerator.
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OBJECTIVE: To explore the radiation shielding problem of Halcyon linear accelerator room. METHODS: According to the dose estimation method recommended by GBZ/T 201.2—2011 Radiation Shielding Requirements for Radiotherapy room--Part 2: Radiotherapy Room of Electron Linear Accelerators(hereinafter referred to as GBZ/T 201.2—2011) and NCRP report No.151 Structural Shielding Design and Evaluation for Megavoltage X-and Gamma-Ray Radiotherapy Facilities the required shielding thickness of 6.0 MeV Halcyon linear machine room is evaluated and compared with the existing machine room. After the equipment was put into use, we measured and verified the dose equivalent rate around each point. RESULTS: ⅰ) The transmittance of the main beam passing through the self-shielding system was 0.06%. The theoretical shielding thickness of the main beam path sites A, C and L of the accelerator(two main shielding walls and room top sites respectively) was 136.00, 130.00 and 136.00 cm, which was lower than the required shielding thickness of the main shielding area specified in GBZ/T 201.2—2011 for 6.0 MeV accelerator. ⅱ) Compared with the existing equipment rooms in the hospital, except that the thickness of the top secondary shield(80.00 cm) and the thickness of the west section of the outer wall of the labyrinth(100.00 cm) are smaller, the rest meets the shielding requirements. ⅲ) After the transformation of the computer room and the installation of Halcyon linear accelerator, the surrounding dose equivalent rate was lower than the control level required by GBZ/T 201.2—2011. CONCLUSION: The self-shielding design of Halcyon linear accelerator can effectively protect 6.0 MeV rays used for treatment, reduce the shielding thickness required for the main shielding area, reduce the shielding construction cost of the equipment room and increase the usable area of the equipment room.
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OBJECTIVES@#To compare the effects of different irradiators on the establishment of osteoradionecrosis of jaw model (ORNJ) to explore an ideal modeling method.@*METHODS@#A total of 33 adult SD rats were included and randomly divided into three groups according to the radiation equipment, namely, the blank control (CN, 3 rats), group A (linear accelerator irradiation, 15 rats), and group B (small-animal irradiator irradiation, 15 rats). Groups A and B were irradiated with daily fractions of 7, 8, and 9 Gy for 5 days and further divided into three subgroups as follows: group A@*RESULTS@#At 3 weeks after dental extractions, complete gingival healing was found in the regions of dental extractions in groups A@*CONCLUSIONS@#Small-animal irradiator irradiation is an ideal device for establishing ORNJ model.
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Animals , Rats , Mandible , Molar , Osteoradionecrosis/etiology , Rats, Sprague-Dawley , X-Ray MicrotomographyABSTRACT
The transportation of electron is inseparable from vacuum environment. The maintenance of the vacuum system of Elekta linear accelerator depends on two sputtering ionic pumps at the gun end and the target end. The traveling wave acceleration were used in Elekta linear accelerators. And the design of the electron gun filament is detachable. Because of these two reasons, the vacuum stability is relatively weak. Only two vacuum values are used to reflect the operation state of the whole vacuum system, which causes a few failures but will not trigger a the machine interlock. Considering the complexity of whole vacuum system, the problem of vacuum caused by the failure of various components in vacuum system is analyzed in this paper. It is hoped that some useful repairing experience and suggestions for the maintenance engineers of linear accelerator to solve the vacuum fault and rebuild the vacuum can be provided quickly.
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Electrons , Particle Accelerators , Radiotherapy Dosage , VacuumABSTRACT
Objective To analyze the quality control data of linear accelerator detected by Daily QA3 and to evaluate this quality control process using statistical process control.Methods After the calibrations of the accelerator and Daily QA3,Daily QA3 device was used to perform daily quality control by technicians and physicists and 100 groups and 30 groups of daily quality control data were collected.After the accelerator and Daily QA3 were re-calibrated,Daily QA3 device was utilized to perform daily quality control by technicians and 100 groups of the daily quality control data were repeatedly collected.The variations of normalized signal-to-noise ratio of quality control data collected after two calibrations were analyzed.The first 30 groups of daily quality control data measured by technicians and physicists were adopted to calculate the I-MR control chartsand compare the location of CL and the range of UCL and LCL.The process capability indices were calculated for three different quality control processes bytechnicians and physicists,respectively.Results For twice calibrations,normalized signal-to-noise ratio of quality control data significantly changed before 6 weeks,became stable between 6 and 8 weeks,and the changes became smaller after 8 weeks.For dose output measured by physicists,the rang of UCL and LCL was more narrow.In terms of flatness and symmetry,the location of CL was closer to zero.Regarding dose output and flatness,the process capability indices of three different quality control process were all satisfied ≥ 1,whereas unsatisfied for transverse symmetry.Conclusions The first 30-40 data points should be adopted to delineate I-MR control chart of the linear accelerator in daily quality control process.The quality control process should be completed by a fixed and small group of personnel and an optimal tolerance level should be customized.
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Aim: The purpose of this study is to measure radiation leakage of Siemens Primus Plus and Siemens Artiste linear accelerators in electron mode and to compare the leakage level with that recommended by the International Electrotechnical Commission (IEC) standard. Materials and Methods: In this assessment, Siemens Primus Plus linear accelerator with 10 cm × 10 cm, 15 cm × 15 cm, and 25 cm × 25 cm applicators was used. The radiation leakage in lateral and vertical directions was measured for Siemens Primus Plus and Siemens Artiste linear accelerators. Results: Data derived from radiation leakage measurement for Siemens Primus Plus and Siemens Artiste linear accelerators in lateral direction from the field edge and in vertical direction from the applicator were reported. The radiation leakage data were then compared with the IEC standard to evaluate in-air field leakage. Conclusion: Comparing the radiation leakage level from fields with the IEC standard for two applicators, the maximum that was occurred for 12 MeV electron beam and applicator size of 10 cm × 10 cm in Siemens Artiste linear accelerator was 2.3%, which is less than the IEC's recommended limit of 10%. It is concluded that the leakage amount is much less than the specified limit and that both of the linear accelerators have high level of safety. Considering the measurement stage, it also needs to be noted that the beam angle affected the radiation leakage level from field edge, and in 25° angle, it is higher than in 0° angle. Comparing radiation leakage from the right side of the field for the two linear accelerators, the amount of leakage for Siemens Primus Plus linear accelerator is more than Siemens Artiste linear accelerator
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Through the analysis of 3 maintenance of Bmag interlocking fault of Varian Clinac Ⅸ Linear Accelerator,it is found that the full wave rectifier diode breakdown in the bend magnet power supply,the improper setting of the bend magnet interlock,and the failure of the modulator CB3 air switch can cause the bmag interlocking.Through the replacement of accessories,adjustment parameters,etc.,so that the fault is resolved.