西门子医用电子直线加速器磁控管更换技术

磁控管在直线加速器中是非常关键的部件，为加速波导提供微波功率，磁控管到达一定使用寿命后应该更换。本文介绍了西门子医用电子直线加速器磁控管更换的一般步骤。     

医用直线加速器磁控管原理及故障鉴别

阐述了医用直线加速器中磁控管的原理、结构及分类，提出了医用直线加速器在磁控管使用到接近或超过保用的高压小时后发生高压或类似故障时的维修及故障的鉴别方法．可提高对直线加速器的认识和排除此类故障的准确率及直线加速器修复率．对临床维修实践有一定的实际意义。     

加速器磁控管使用1200高压小时维护体会

医用电子直线加速器是目前最常用的放射治疗设备。目前国内多数使用的是磁控管微波功率加速器。维护磁控管频率稳定,是实现直线加速器的质量保证重要的措施。     

延长直线加速器磁控管使用寿命的方法

1引言医用直线加速器(Linac)是肿瘤放射治疗的必备设备,磁控管(Mag-netron)是该设备的核心部件。直线加速器的射线输出能谱、稳定性、均匀性、准确性以及直线加速器正常运行的经济成本都与磁控管的工作状态及品质相关。在保证直线加速器正常运行的前提下,设法延长磁控管的工作寿命,对于提高直线加速器的单机成本效益有着至关重要的作用。2磁控管工作原理简介2.1磁控管的构成磁控管在外加磁场和电压作用下产生微波振荡,其结构分为6部分:(1)阴极:脉冲电流可达20～200Amps;(2)阳极:它是一系列谐振腔,又称阳极块;(3)磁铁;(4)波导耦合输出装置;…     

医用直线加速器磁控管伪故障的判断与修复

在医用低能直线加速器中,常采用转电位器R62,使得TP10点电压降到最磁控管作为微波振荡器。我院引进的美低点,大约为3.40V,此时再按照晨检方国VARIAN公司的CL600C/D医用直线法开机出束,开始时剂量率可能会很低,加速器采用英国EEV公司生产的或者较长时间无束流输出,只要磁控管没M     

Elekta BMEI BJ－6B医用直线加速器故障分析三例

本文分析了医用直线加速器楔形故障、手控盒故障、磁控管灯丝电源故障原因。并提出了故障处理方法。     

BJ-6B医用直线加速器磁控管异常打火的应急处理

本文分析了医用直线加速器M5193型磁控管产生异常打火的原因、处理办法及由此引发特殊故障的应急处理。     

直线加速器水冷系统故障处理

医用直线加速器中水冷系统是直线加速器正常工作的重要保障部分，水冷系统的异常将导致直线加速器各系统的故障，甚至会导致直线加速器中一些重要器件的损坏，如磁控管、偏转室、靶窗、聚焦对中线圈等。水冷系统的故障应即时处理，以防止加速器系统的进一步损坏。在我院PHILIPSSL75－14医用直线加速器中，使用了一台循环式水冷机，整个系统由储水箱、水泵、进出水管、制冷压缩机、散热风机及相应的保护控制电路所组成。储水箱中的水由水泵压入直线加速器制冷入水管，流经直线加速器发热系统及相应器件，带走这些部件的热量。温度升高后…     

医用直线电子加速器高压打火的检修

电子加速器就是在真空中用电磁场将带电粒子加速到很高能量的一种装置 ,而电子直线加速器则是用微波电磁场将电子沿直线轨道加速的装置。在用微波电磁场加速电子的电子直线加速器中 ,为了得到高值量的加速电场 ,瞬时微波功率很大。因此 ,微波源都是脉冲工作的 ,高压脉冲调制器是这种微波源的主要组成部分。主要有磁控管或速调管、高压组件、充电组件、脉冲形成网络组件、脉冲变压器等 ,高压脉冲调制器是磁控管的高压脉冲电源 ,其是否正常工作是加速器产生X线、电子线能量高低的关键。北京医疗器械研究所生产的BJ -6B型医用电子直线加速器…     

Varian 600C直线加速器YLD联锁的分析与故障排除

美国Varian 600C直线加速器是一种用于肿瘤放射治疗的低能医用直线加速器，它只能产生单一6MV能量的X射线。600C加速器采用了磁控管作为微波功率源，在设备的控制电路中设计了一个YLD联锁电路，用以检测和调整输出射线能量的稳定性，一旦能量发生变动时，YLD联锁电路动作，使加速器不能用于肿瘤患者的治疗。     

医用直线加速器的安装验收

目的:探讨医用直线加速器验收的总体要求,提高验收质量和效率。方法:按照国家标准,分析各厂家的验收方法,制定本单位总体验收的程序和措施。结果:ELEKTA SL18、SIEMENS PRIMUS、VARIAN Clinic600C一次性顺利通过卫生行政部门的验收。结论:医用直线加速器验收是机房、设备性能、使用人员资质、物理师水平、管理制度、配套设备、数据资料等方面的全面评估、总体验收,高水平的物理师是高质量、高效率验收的技术保证。     

ELEKTA PRECISE型加速器临床维护情况分析与研究

通过对ELEKTA PRECISE型加速器运行5年中维修保养情况的总结和分析,进一步研究该机型的运行及故障情况规律性,得出如何更好地解决医用电子直线加速器在临床放射治疗中降低停机率的核心问题.     

Effects of collimator backscatter in an Elekta linac by Monte Carlo simulation

The effects of radiation backscattered from the secondary collimators into the monitor chamber in an Elekta linac (producing 6 and 10 MV photon beams) are investigated using BEAMnrc Monte Carlo simulations. The degree and effects of this backscattered radiation are assessed by evaluating the changes to the calculated dose in the monitor chamber, and by determining a correction factor for those changes. Additionally, the fluence and energy characteristics of particles entering the monitor chamber from the downstream direction are evaluated by examining BEAMnrc phase-space data. It is shown that the proportion of particles backscattered into the monitor chamber is small (<0.35 %), for all field sizes studied. However, when the backscatter plate is removed from the model linac, these backscattered particles generate a noticeable increase in dose to the monitor chamber (up to ≈2.4 % for the 6 MV beam and up to 4.4 % for the 10 MV beam). With its backscatter plate in place, the Elekta linac (operating at 6 and 10 MV) is subject to negligible variation of monitor chamber dose with field size. At these energies, output variations in photon beams produced by the clinical Elekta linear accelerator can be attributed to head scatter alone. Corrections for field-size-dependence of monitor chamber dose are not necessary when running Monte Carlo simulations of the Elekta linac operating at 6 and 10 MV.     

加速器工作量与工作效率的评价

目的:探讨1台加速器工作在常规、满负荷和超负荷工作状态时,所能收治的患者数量,从而正确评价加速器的工作效率。方法:对2004—2009年放射治疗科放疗设备的综合使用、不同放疗技术使用、加速器工作负荷界定和实际工作量进行评估,发现加速器最科学的开机时间。结果:放射治疗科近年来始终在满负荷和超负荷工作状态中运行。结论:放射治疗科应引进新设备,以满足不断增长的工作负荷的需要。     

医用加速器TrueBeam剂量输出长期稳定性研究

目的：分析并研究瓦里安公司新型直线加速器TrueBeam型号光子束的长期稳定性。方法：采用Standard Imaging公司的QA BeamChecker Plus采集TrueBeam系统6 MV光子线长期日检数据,并进行系统性分析,评价参数包括中心轴剂量、平坦度及对称性。结果：18个月的日检数据分析结果显示,6 MV的X射线中心轴剂量偏差为（0.0%±0.7%）,仅1次检测结果〉2%;平坦度稳定性好,偏差为（0.1%±0.1%）;轴向对称性偏差和横向对称性偏差测量结果均在±1%以内。结论：TrueBeam医用加速器系统的6 MV光子束具有非常稳定的剂量输出特性。     

医用加速器反光镜的替代及对X线PDD的影响

目的探讨国产玻璃镜片替代进口加速器反光镜后,对射野等中心、对称性、均整性、重合性及MV级X射线百分深度剂量的影响。方法在不同厚度和材质的镜片及机头不同角度条件下,使用胶片法及三维水箱OAR、PDD测量法进行数据采集,分析比较不同镜片的影响情况。结果普通玻璃4mm镜片对射野PDD影响误差最大为6%;经8MVX线720Gy剂量照射后,灯光野出现双影十字线,亮度变暗。石英玻璃1.5mm镜片对射野PDD、OAR、等中心无明显影响,PDD误差<1%。接受同等剂量,灯光野无明显变化。结论普通4mm玻璃镜片不宜作MV级X线医用加速器的反光镜。采用薄型石英玻璃替代进口加速器反光镜较佳,PDD误差小。     

医用电子直线加速器照射野的日常质量保证

目的通过分析照射野特性相关参数的日检数据的变化趋势．探讨医用电子直线加速器照射野的日常质量保证方法的可行性和必要性。方法每天放射治疗前．用二维电离室矩阵Daily QA3测量加速器照射野特性相关参数与预设标定值的偏差．辅以IBA公司的剂量仪DOSl进行绝对剂量验证和用慢感光胶片进行光野一致性的二次验证．并对以上各项日常检测数据（2009年11月28日-2011年4月8日）进行回顾性分析。结果X线和电子线输出剂量均随着时间的增加逐渐增大．光野一致性、射野平坦度及对称性基本保持不变。结论一年多的实践表明．本文论述的照射野日常质量保证方法是有效和可行的．它在保证每日放疗精确执行的同时,也为加速器的长期校准提供了依据。     

A study of Winston–Lutz test on two different electronic portal imaging devices and with low energy imaging

Stereotactic radiosurgery requires sub-millimetre accuracy in patient positioning and target localization. Therefore, verification of the linear accelerator (linac) isocentre and the laser alignment to the isocentre is performed in some clinics prior to the treatment using the Winston–Lutz (W–L) test with films and more recently with images obtained using the electronic portal imaging devices (EPID). The W–L test is performed by acquiring EPID images of a radio-opaque ball of 6 mm diameter (the W–L phantom) placed at the isocentre of the linac at various gantry and table angles, with a predefined small square or circular radiation beam. In this study, the W–L test was performed on two linacs having EPIDs of different size and resolution, viz, a TrueBeam? linac with aS1000 EPID of size 40 × 30 cm² with 1024 × 768 pixel resolution and an EDGE? linac having an EPID of size 43 × 43 cm² with pixel resolution of 1280 × 1280. In order to determine the displacement of the radio-opaque ball centre from the radiation beam centre of the W–L test, an in-house MATLAB? image processing code was developed using morphological operations. The displacement in radiation beam centre at each gantry and couch position was obtained by determining the distance between the radiation field centre and the radio-opaque ball centre for every image. Since the MATLAB code was based on image processing that was dependent on the image contrast and resolution, the W–L test was also compared for images obtained with different beam energies. The W–L tests were performed for 6 and 8 MV beams on the TrueBeam? linac and for 2.5 and 6 MV beams on the EDGE? linac with a higher resolution EPID. It was observed that the images obtained with the EPID of higher resolution resulted in same accuracy in the determination of the displacement between the centres of the radio-opaque ball and the radiation beam, and significant difference was not observed with images acquired with different energies. It is concluded that the software based on morphological operations provided an accurate estimation of the displacement of the ball centre from the radiation beam center.     

直线加速器XVI质量控制方法的研究

目的：研究直线加速器x线容积影像（xvi）质量控制方法。方法：通过Barracuda多功能X射线分析仪检NX射线的千伏、毫安、剂量等参数，利用CTP503体模测图像低对比度、图像垂直距离、图像空间分辨率、图像均匀性及图像矢状位的几何精度等参数。结果：通过分析4年的X射线参数和各个图像参数的检测数据，针对所发现的问题及时进行维修或校准机器，保障机器各个参数的检测合格率为100％。结论：通过定期对直线加速器质量控制可以确保XVI满足临床的要求，引导直线加速器精确用于临床放疗。     

A method for patient set-up guidance in radiotherapy using augmented reality

A system for patient set-up in external beam radiotherapy was developed using Augmented Reality (AR). Live images of the linac treatment couch and patient were obtained with video cameras and displayed on a nearby monitor. A 3D model of the patient’s external contour was obtained from planning CT data, and AR tracking software was used to superimpose the model onto the video images in the correct position for treatment. Throughout set-up and treatment, the user can view the monitor and visually confirm that the patient is positioned correctly. To ensure that the virtual contour was displayed in the correct position, a process was devised to register the coordinates of the linac with the camera images. A cube with AR tracking markers attached to its faces was constructed for alignment with the isocentre using room lasers or conebeam CT. The performance of the system was investigated in a clinical environment by using it to position an anthropomorphic phantom without the aid of additional set-up methods. The positioning errors were determined by means of CBCT and image registration. The translational set-up errors were found to be less than 2.4 mm and the rotational errors less than 0.3°. This proof-of-principle study has demonstrated the feasibility of using AR for patient position and pose guidance.