Varian23EX加速器UDRS连锁故障维修2例

0 引言 瓦里安23EX加速器是产品2300CD的升级版,它添加设计了一些辅助控制功能,加速器的连锁可多达60种左右[1],UDRS连锁比较常见,且起因复杂,在实际维修工作中常常会制造难题,而临床治疗时往往要求快速修复机器故障,提高加速器的开机率,所以有必要分析UDRS连锁的产生机制,从而寻求一种准确快速修复此类故障的维修思路,更好地满足临床治疗需要.     

西门子直线加速器注入电路常见故障的分析与排除探讨

西门子直线加速器在实际应用过程中会遇到一系列故障，这些故障如果得不到有效处理就会影响到实际工作效率。为了保证系统能够正常运行，在实际工作过程中就需要加强对西门子直线加速器注入电路故障的研究。本文将重点分析当前常见故障及采取专业措施来进行排除。     

医用电子直线加速器注入器系统故障定位专家系统模型设计

目的:探讨医用电子直线加速器注入器系统故障定位专家系统模型的实现。方法:医用直线加速器注入器系统故障诊断难度大,不确定性高,故需深入的分析总结基于对医用电子直线加速器注入器系统主要故障类型的故障机理。文章同时剖析了系统故障诊断机制的内容及特点。结果:针对直线加速器注入器故障诊断的特殊性提出了故障逆向推理机制,对推理机制的可行性进行了分析,得出了执行故障逆向推理机制的具体步骤,为系统故障诊断提供了理论依据。结论:利用故障树分析技术对直线加速器注入器故障定位方法切实有效,简单可行。     

医用电子直线加速器驻波加速管系统故障定位与安装调试方法研究

目的：探讨医用电子直线加速器驻波加速管故障定位及安装调试方法的实现,使加速器各项性能指标符合国家标准GBl5213—94《医用电子直线器性能及试验方法》的要求。方法：基于故障树分析法,将驻波加速管常见故障构建故障树,可分为五类：电子枪故障,微波输入窗故障,钛泵外围故障,偏转盒及电子输出窗和加速管真空度联锁（WGVACUUM）故障。经过剖析这五种故障定位方法的机制和特点,结合工作实例,发现一些故障最终需要更换驻波加速管来解决。这就需要提出安装调试驻波加速管的工艺流程。结果：利用这些方法可快速解决医用电子直线加速器驻波加速管的常见电气故障。同时利用安装调试驻波加速管的工艺流程,可快速有效地更换加速管。结论：实践证明利用这些方法维修和安装医用电子直线加速器驻波加速管切实有效,简单可行。     

直线加速器预防性维护保养的内容和方法

本文介绍直线加速器预防性维护保养的内容和方法。实施预防式维修,可减少设备故障、缩短停机时间,有利于实现设备高效益运行。     

临床运行中电子直线加速器的故障原因及干预对策

目的：探讨临床运行中电子直线加速器的故障原因及干预对策。方法：对1台于2020年9月至2021年12月临床运行1年3个月的医用电子直线加速器的故障发生原因与频率调查结果进行回顾性分析,并制定出有效的干预对策。结果：医用电子直线加速器的常见故障原因主要为X射线容积成像影像系统故障,占比为21.82%(12/55),其次为机械运动故障,占比为18.18%(10/55);电路故障的发生频率虽然不高,但因此故障所导致的功能停用与停机时间却相对较长。结论：在医用电子直线加速器临床运行过程中,要减少X射线容积成像影像系统与机械运动故障,降低故障发生频率,应该结合医用电子直线加速器临床运行故障发生原因与频率,制定出定期维护保养等有效的干预对策。     

瓦里安Clinac iX型直线加速器故障维修2例

作为目前国内放射治疗常用机型之一,瓦里安Clinac iX 直线加速器结构复杂,在维修时需要充分掌握其设计和工作原理,以对其故障进行有效分析和针对性排除.本文对瓦里安Clinac iX型直线加速器的2例典型故障进行分析,供同行参考. 1 故障一 故障现象:治疗过程中叶片突然不动,出现MLC联锁.     

加速器6年停机情况的回顾性分析

目的 分析加速器停机原因,总结设备故障规律,为加速器的安全合理使用、设备定期维护和科学管理提供决策依据.方法 有2100C、23EX和600CD3台加速器,其中2100C、23EX为高能加速器,600CD为低能加速器.统计最近6年3台加速器的停机时间和次数,分析设备技术状态指标.结果 2100C、23EX和600CD累...     

西门子PRIMUS-H型直线加速器故障2例

甘肃省肿瘤医院于1997年购进的西门子PRIMUS—H型直线加速器为高能直线加速器，在运行的这几年中先后更换过速调管、闸流管、射频源等现就治疗中出现的两次故障进行分析。     

医科达Precise直线加速器快速应急处理方法探讨

目的：用处理治疗床手动刹车释放控制和指示电源电路和内循环水温度传感器为实例，探讨Precise直线加速器快速应急处理方法。方法：Precise直线加速器治疗床控制手柄指示灯不亮，手动刹车释放控制失灵，将手动刹车释放控制和指示电源电路7号线搭接在9号线获取26v；向加速器控制系统（LCS）传输内循环水温度信号的传感器工作不正常时，用阻值1kΩ，X-2w型电位器取代内循环水温度传感器。结果：两种应急处理方法分别让机器治疗床正常运动和加速器准确出束治疗。结论：在加速器出现故障时，确认不影响治疗质量和机器安全前提下，可以采取某些应急处理方案，但需要医院工程师熟读图纸和应用技术说明书，在实施应急处理方案前要多和厂家工程师讨论，沟通。在没有把机器恢复到原状时，要密切观察相关参数以确保加速器安全运行。为了提高开机率，医院工程师应多读、多研究相关机型维修文献，熟悉机器元件特性、收集应急备用元件以便出现问题时能有条不紊快速、安全处理。当新元件或电路板到达后．应及时更换，恢复到加速器出厂时的情况。     

Isocentric rotational performance of the Elekta Precise Table studied using a USB-microscope

The isocentric three-dimensional performance of the Elekta Precise Table was investigated. A pointer was attached to the radiation head of the accelerator and positioned at the geometric rotational axis of the head. A USB-microscope was mounted on the treatment tabletop to measure the table position relative to the pointer tip. The table performance was mapped in terms of USB-microscope images of the pointer tip at different table angles and load configurations. The USB-microscope was used as a detector to measure the pointer tip positions with a resolution down to 0.01 mm. A new elastic model of the treatment table was developed. This model describes the performance of the treatment table quite well except from some deviations due to backlash effects. Geometric and elastic features are described through six parameters. These parameters are calculated using the linear least squares fitting technique. A new method to ensure optimal positioning of the table relative to the accelerator is presented. This method cannot eliminate systematic errors completely. To eliminate systematic errors we suggest that geometric and elastic models of the table and accelerator gantry arm are incorporated in the dose planning system.     

基于加速器的锥形束CT系统机械精度的精确测量方法及其实现

目的:设计并实现一种锥形束CT（CBCT）机械精度的检测方法,可对CBCT的机械性能参数进行精确测量和分析（重复性在0.5 mm以内,测量误差在0.5 mm内,耗时数分钟）。方法:系统硬件包括双目红外相机、定位小球、注册笔和水平注册仪。双目红外相机可输出定位小球中心的空间坐标,利用定位小球中心位置坐标可计算出加速器机械等中心坐标,利用CBCT拍出的定位小球图像可计算出CBCT影像中心与加速器机械等中心的偏差,利用注册笔可计算出CBCT平板角度偏差。结果:在某医院加速器配备的CBCT上运用本方法进行3次测试和分析,得到加速器机械等中心坐标、CBCT影像等中心坐标、两等中心距离误差和CBCT平板打开垂直度等数据。结论:本研究提出的检测CBCT机械精度的方法操作过程较简单,结果精准,可重复性高,将复杂的质控过程数字化、自动化和简单化,给CBCT的日常质量检测带来非常大的便利,也为相关技术人员以及医护人员在临床上安全应用CBCT提供指导。 【关键词】锥形束CT;红外双目相机;定位小球;机械等中心;影像等中心     

Modification of Michaëlsson''s method for the measurement of plasma total bilirubin

Michaëlsson''s (1961) method for the measurement of plasma bilirubin concentration was found to be complicated by conjugated bilirubin. Delaying the addition of the accelerator, diphylline, corrected this fault. The method was calibrated using serum or plasma, since reconstituted protein solutions introduced large errors.     

Calculative technique to correct for the change in linear accelerator beam energy at off-axis points

The change in energy of linear accelerator x-ray beams from the central ray to off-axis points causes errors in the dose calculated by conventional techniques for large, irregularly shaped fields. A modification of conventional calculative methods to correct for the change in beam energy is presented. The results of measurements in irregular fields on a Clinac-4 are reported which verify the validity of the calculative method. A discussion of the clinical significance will point out errors of 3% to 4% in conventional dose calculations.     

统计过程控制在医用电子直线加速器机械性能监测中的应用

目的：使用统计过程控制方法分析医用电子直线加速器长期过程表现,监测加速器状态变化趋势,并评估加速器各项指标性能状态。方法：收集2019年6月至2021年4月加速器机器性能检测(MPC)数据。绘制每个机械指标的单值控制图,分析各指标过程特征,并使用过程能力指数C_pk及C_p评估加速器各项机械指标的过程质量。结果：加速器机械精度明显优于当前厂商推荐的规格限值,但控制图监测结果显示各指标均存在一定程度的过程漂移。过程能力分析结果显示所有指标的C_pk及C_p均大于1.33,过程质量优秀。结论：加速器在满足当前MPC规格限的情况下依然可能发生过程失控。统计过程控制方法可及时发现过程中的异常改变,过程能力指数可有效评估过程质量,为质量管理及临床决策提供有效的信息。     

Correlated histogram representation of Monte Carlo derived medical accelerator photon-output phase space.

We present a method for condensing the photon energy and angular distributions obtained from Monte Carlo simulations of medical accelerators. This method represents the output as a series of correlated histograms and as such is well-suited for inclusion as the photon-source package for Monte Carlo codes used to determine the dose distributions in photon teletherapy. The method accounts for the isocenter-plane variations of the photon energy spectral distributions with increasing distance from the beam central axis for radiation produced in the bremsstrahlung target as well as for radiation scattered by the various treatment machine components within the accelerator head. Comparison of the isocenter energy fluence computed by this algorithm with that of the underlying full-physics Monte Carlo photon phase space indicates that energy fluence errors are less than 1% of the maximum energy fluence for a range of open-field sizes. Comparison of jaw-edge penumbrae shows that the angular distributions of the photons are accurately reproduced. The Monte Carlo sampling efficiency (the fraction of generated photons which clear the collimator jaws) of the algorithm is approximately 83% for an open 10x10 field, rising to approximately 96% for an open 40x40 field. Data file sizes for a typical medical accelerator, at a given energy, are approximately 150 kB, compared to the 1 GB size of the underlying full-physics phase space file.     

肿瘤快速旋转调强放疗摆位误差的测量与分析

目的:采用直线加速器机载的千伏级锥形束CT扫描技术对不同部位肿瘤患者的摆位误差进行探讨。方法:应用瓦里安RapidArc直线加速器治疗肿瘤患者180例,其中头颈部患者53例,胸部患者58例,盆腔患者69例。所有患者在首次放疗前行KV-CBCT扫描,以后每周扫描1次。将CBCT扫描图像和计划CT图像及其靶中心匹配,分析靶中心在x、y、z方向上的误差值及其误差分布情况,探讨我科CTV–PTV外放边界大小。结果:系统误差(均数)±随机误差(标准差)在平移误差Lateral左右(x)方向、Vertical背腹(y)方向、Longitudinal头脚(z)方向分别为头颈部x(0.55±0.79)mm,y(0.81±1.00)mm,z(1.21±1.12)mm;胸部x(1.13±1.26)mm,y(1.03±1.09)mm,z(2.12±2.15)mm;盆腔x(0.94±1.16)mm,y(0.87±1.08)mm,z(2.02±1.78)mm;绕y轴方向旋转(Rtn)误差分别为头颈部(0.39±0.48)°,胸部(0.47±0.54)°,盆腔(0.44±0.51)°。结论:CBCT可以减少分次治疗间的摆位误差,保证放疗摆位精度。     

放疗智能检测仪在直线加速器质量保证和质量控制中的应用

目的：比较用放疗智能检测仪与常规方法检测同一台直线加速器而得到的机械参数和几何参数的差异值．分析两种方法的准确性。希望放疗智能检测仪能够代替常规检测手段来检测直线加速器，保证直线加速器的机械精度和几何精度符合《医用电子加速器验收试验和周期检验规程》（GB／T19046-2003）（以下简称《规程》）。方法：利用一台我院新启用的医科达（synergy）电子直线加速器作为实验平台，根据不同的光学检测原理，使用放疗智能检测仪匹配的检测方法和《规程》规范的检测方法分别对这台直线加速器的机架、光野、多页准直器、治疗床以及激光灯等的相关技术参数进行测量．并将得到的相同类别的不同参数作比较。结果：通过比较检测得到所有项目的机械参数和几何参数，发现两种测量方法所得结果相近，并且两种方法所得结果的差值都在理论值的±l％以内，而且检测仪检测方法所得到的结果精度更高。结论：基于这个结果，发现放疗智能检测仪能够代替常规的测量手段，检测直线加速器乃至放疗科其他定位设备（如X线模拟定位机），做好直线加速器以及其他定位设备的质量保证和质量控制工作，并且能够做到精度更高，时间更省!     

On the accuracy and effectiveness of dose reconstruction for tomotherapy

Dose reconstruction is a process that re-creates the treatment-time dose deposited in a patient provided there is knowledge of the delivered energy fluence and the patient's anatomy at the time of treatment. A method for reconstructing dose is presented. The process starts with delivery verification, in which the incident energy fluence from a treatment is computed using the exit detector signal and a transfer matrix to convert the detector signal to energy fluence. With the verified energy fluence and a CT image of the patient in the treatment position, the treatment-time dose distribution is computed using any model-based algorithm such as convolution/superposition or Monte Carlo. The accuracy of dose reconstruction and the ability of the process to reveal delivery errors are presented. Regarding accuracy, a reconstructed dose distribution was compared with a measured film distribution for a simulated breast treatment carried out on a thorax phantom. It was found that the reconstructed dose distribution agreed well with the dose distribution measured using film: the majority of the voxels were within the low and high dose-gradient tolerances of 3% and 3 mm respectively. Concerning delivery errors, it was found that errors associated with the accelerator, the multileaf collimator and patient positioning might be detected in the verified energy fluence and are readily apparent in the reconstructed dose. For the cases in which errors appear in the reconstructed dose, the possibility for adaptive radiotherapy is discussed.