关于体部X刀治疗的QA与QC

体部Ｘ刀适形放射治疗是传统放疗技术的革命性进展。在ＣＴ定位、治疗方案设计、模具制作以及治疗实施均应严格质量保证（ＱＡ）和质量控制（ＱＣ）体系。我们对前期应用体部Ｘ刀治疗５４例患者满一月后随访疗效分析，总有效率达９８．５％，未控率１．８５％，认为，体部Ｘ刀比常规放疗精度高，其ＱＡ与ＱＣ措施是有效保证该治疗方式高有效率的重要内容     

利用模拟机及挡铅托架进行放疗前的治疗模拟

目的：通过对食管癌实例分析,理清放射治疗的全部过程,重点是利用模拟机模拟病人放疗过程,从中探讨模拟机的模拟过程在三维适形放射治疗中的临床应用价值。方法：以10位4野照射的食管癌病人为例,首先进行常规放疗模拟机的质量保证和质量控制（QA／QC）,本文重点介绍等中心精度的检验和光野射野的一致性;然后利用双螺旋CT机、体位固定装置、三维激光定位系统、常规放疗模拟机及挡铅托架对放疗病人进行体模制作、CT定位、制定治疗计划、制作挡铅及进行模拟验证,分别从寻找射野中心、射野验证、计算深度验证、治疗计划各项参数的可行性验证四个方面进行分析。结果：常规放疗模拟机的各项指标达到QA规定的允许限度内。通过治疗计划显示的各种参数（挡块、楔形等）的调整及修饰后,在常规X线模拟机下对照射野位置及计算深度进行验证可发现：全部患者的计算深度符合临床要求;大部分患者的剂量分布符合临床要求,成功率达90％;射野中心偏移误差最大为3．5mm,最小为0．5mm。在整个治疗过程中,两位患者出现了与床相撞的情况。结论：对放疗患者进行放疗前模拟的过程是三维适形放疗的重要环节,用于验证放疗计划的可行性,保证放疗过程安全有效地进行。     

放疗网络与信息系统

目的:探讨目前我国放疗网络与信息系统应用的现状以及发展方向。方法:放疗网络由硬件和软件以及传输协议组成。网络硬件包括服务器、工作站、路由器和交换机、外围网络设备。网络软件包括服务器软件、客户端软件、杀毒软件以及操作系统更新。传输协议包括TCP/IP协议、DICOM协议、HL7协议等。信息系统的构成要素又包括用户,流程,新技术应用,系统管理。结果:目前我国各地医院对于放疗网络和信息系统的应用相比国际水平还有相当的差距。结论:放疗网络与信息系统作为放疗科工作开展的载体,在整个放疗科的诊疗活动中起着非常关键的作用,我国的放疗网络和信息系统的应用将更上一层楼。     

SunCHECK软件在调强放疗计划剂量验证中的应用

目的:探讨SunCHECK软件在调强放疗计划剂量验证中的应用。方法:选取新疆医科大学第一附属医院已执行IMRT计划的40例患者,应用SunCHECK软件,对所接受数据进行单独计算,然后对原始放疗计划和QA计划进行Gamma分析。最后对QA计划与ArcCHECK测量结果进行Gamma通过率比较。结果:在SunCHECK软件单独计算结果中,Monaco计划平均Gamma通过率略高于Eclipse计划。相同计划系统原始计划与QA计划Gamma通过率没有差异。使用SunCHECK软件计算QA计划（包括Monaco计划和Eclipse计划）Gamma通过率略高于ArcCHECK测量结果的Gamma通过率。结论:SunCHECK软件符合IMRT计划剂量验证需要,给放疗质控工作带来了很大的便利性。无论是作为单独放疗计划验算工具,还是以log日志文件反推进行计划验证,都应该把SunCHECK作为质量保证程序的一部分。     

基于UNIX、TCP/IP和Sybase平台的住院病房管理系统的开发

本文说明河北医科大学第二医院新落成的三座主体住院楼内部信息管理网络系统的设计开发和具体实施概况。其中包括网络的物理结构、功能、软件体系和前端开发工具等。     

术中光子立体定向放射治疗的质量保证和质量控制

【摘要】目的:从术中光子立体定向放疗设备物理剂量学方面,总结和分析术中放疗质量保证的内容和方法以及术中放疗实际应用中的注意事项,保证术中放疗物理剂量准确性,旨在建立该系统的日常质量保证程序。方法:利用蔡司公司提供的水箱、剂量仪、电离室等,测量术中立体定向放射外科系统的临床运用数据。监测内容主要包括剂量线性、稳定性、均匀性、射线几何聚焦的位置、绝对剂量标定以及在水模体的衰减等。结果:术中光子立体定向放疗仪产生50 kV低能射线。剂量线性、均匀性良好,短期稳定性也在临床接受的误差范围以内,36 h内剂量误差小于1%。对比24个月的剂量测量值,其误差达到-4.5%。结论:该设备稳定性良好,各检测指标均在临床要求精度范围以内。通过测量了解了卡尔蔡司公司的INTRABEAM术中放射治疗设备临床应用特性,获得了临床使用数据,为临床提供了质量保证方法。     

基于GPU的蒙特卡洛放疗剂量并行计算

目的：蒙特卡洛模拟在放疗剂量计算领域被广泛视为最精确的计算方法,但对于日常的临床应用,其效率仍有较大提升需求和空间。方法：本文会呈现放疗剂量计算领域的最新成果－维持相同的粒子输运原理的同时,使用CUDA语言,利用显卡的GPU（GraphicProcessingUnit）并行处理蒙特卡洛计算中的主要过程,计算光子剂量沉积。这样既可以保证不失去蒙卡模拟的精度．又可以极大地提高运算速度。结果：实践表明在使用NVIDIAGTX4601GDDR5plusINTELi52300的硬件设备,在GPU上并行计算蒙特卡洛放疗剂量沉积时．计算100万个光子剂量沉积时加速因子达到116．6,处理1000万光子入射,加速因子可达127．5。结论：本文中利用显卡GPU运行CUDA语言对放疗剂量计算进行模拟,是一种可以大幅有效提高剂量计算效率方法。     

简化调强技术在脑转移瘤外照射中应用的剂量学研究

目的：通过比较脑转移瘤三维适形放疗（3D-CRT）、调强放疗（IMRT）和简化调强放疗（sIMRT）技术靶区剂量分布均匀性、适形度,危及器官受照体积、剂量,以及实施治疗的机器跳数,对比三者放疗技术的剂量学差异,探讨sIMRT应用于脑转移瘤治疗的可行性。方法：针对10例脑转移瘤患者分别设计3种放疗计划：三维适形放疗、调强放疗和简化调强放疗。保证靶区和危及器官满足临床要求前提下,分别比较3种计划的靶区剂量分布、靶区均匀指数和适形指数、危及器官受照剂量、机器跳数（MU）等,探讨其剂量学差异。结果：3种照射技术均满足临床要求,靶区（PGTV）均匀指数三者没有差异。靶区（PTV）均匀指数sIMRT逊于IMRT,但与3D-CRT无差异。靶区（PGTV、PTV）适形指数sIMRT逊于IMRT而强于3D-CRT。危及器官的保护例如左、右晶体和脑干,sIMRT优于3D-CRT但与IMRT无区别,对左、右视神经和视交叉的保护,IMRT最好,sIMRT和3D-CRT差异不大。机器跳数（MU）以IMRT最多,sIMRT居中,3D-CRT最少,但3D-CRT二程计划增加照射次数,提示实际治疗时间以sIMRT最优。结论：sIMRT可减轻工作人员劳动强度,缩短治疗时间,节省资源,是一种性价比较高的放疗技术,适用于脑转移瘤放疗。     

医院检验设备网络系统DE开发与应用

利用计算机网络技术构建检验设备网络系统，用于解决检验数据实时接收、实时共享、并行处理、在线监控和在线质量控制，实现检验报告的中文化及检验资料存贮、检验计费自动化。本文介绍基于计算机局域网的医院检验设备实时网络系统的设计、特点与功能。     

鼻咽癌处理的调强放疗

本文从物理学的观点介绍鼻咽癌处理中调强放疗临床实践的有关概况。文中对于处理过程中挑战性的问题以及临床处理流程，尤其是保证几何和计量计算的精度问题进行了讨论。对那些用于治疗计划和剂量优化计算的技术和策略、处理计划的评价、剂量验证和病人的移动等问题和处理的质量保证和检测问题一起进行了讨论。对调强放疗虚拟剂量验证的原理和邮电进行了介绍和描述。我们用35个鼻咽癌病人处理的初步结果表明：和常规的放疗技术相比，这里介绍的调强技术能够改进处理时的复杂性。     

A dose verification method using a monitor unit matrix for dynamic IMRT on Varian linear accelerators

Dosimetry verification is an important step during intensity modulated radiotherapy treatment (IMRT). The verification is usually conducted with measurements and independent dose calculations. However, currently available independent dose calculation methods were developed for step-and-shoot beam delivery methods, and their uses for dynamic multi-leaf collimator (MLC) delivery methods are not efficient. In this study, a dose calculation method was developed to perform independent dose verifications for a dynamic MLC-based IMRT technique for Varian linear accelerators. This method extracts the machine delivery parameters from the dynamic MLC (DMLC) files generated by the IMRT treatment planning system. Based on the parameters a monitor unit (MU) matrix was separately calculated as two terms: direct exposure from the open MLC field and leakage contributions, where the leaf-end leakage contribution becomes more important in higher dose gradient regions. The MU matrix was used to compute the primary dose and the scattered dose with a modified Clarkson technique. The doses computed using the method were compared with both measurement and treatment planning for 14 and 25 plans respectively. An average of less than 2% agreement was observed and the standard deviation was about 1.9%.     

Independent monitor unit calculation for intensity modulated radiotherapy using the MIMiC multileaf collimator

A self-consistent monitor unit (MU) and isocenter point-dose calculation method has been developed that provides an independent verification of the MU for intensity modulated radiotherapy (IMRT) using the MIMiC (Nomos Corporation) multileaf collimator. The method takes into account two unique features of IMRT using the MIMiC: namely the gantry-dynamic arc delivery of intensity modulated photon beams and the slice-by-slice dose delivery for large tumor volumes. The method converts the nonuniform beam intensity planned at discrete gantry angles of 5 degrees or 10 degrees into conventional nonmodulated beam intensity apertures of elemental arc segments of 1 degree. This approach more closely simulates the actual gantry-dynamic arc delivery by MIMiC. Because each elemental arc segment is of uniform intensity, the MU calculation for an IMRT arc is made equivalent to a conventional arc with gantry-angle dependent beam apertures. The dose to the isocenter from each 1 degree elemental arc segment is calculated by using the Clarkson scatter summation technique based on measured tissue-maximum-ratio and output factors, independent of the dose calculation model used in the IMRT planning system. For treatments requiring multiple treatment slices, the MU for the arc at each treatment slice takes into account the MU, leakage and scatter doses from other slices. This is achieved by solving a set of coupled linear equations for the MUs of all involved treatment slices. All input dosimetry data for the independent MU/isocenter point-dose calculation are measured directly. Comparison of the MU and isocenter point dose calculated by the independent program to those calculated by the Corvus planning system and to direct measurements has shown good agreement with relative difference less than +/-3%. The program can be used as an independent initial MU verification for IMRT plans using the MIMiC multileaf collimators.     

Implementation of a quality assurance program for computerized treatment planning systems

In the present investigation, the necessary tests for implementing a quality assurance program for a commercial treatment planning system (TPS), recently installed at Sao Paulo University School of Medicine Clinicas Hospital-Brazil, was established and performed in accordance with the new IAEA publication TRS 430, and with AAPM Task Group 53. The tests recommended by those documents are classified mainly into acceptance, commissioning (dosimetric and nondosimetric), periodic quality assurance, and patient specific quality assurance tests. The recommendations of both IAEA and AAPM documents are being implemented at the hospital for photon beams produced by two linear accelerators. A Farmer ionization chamber was used in a 30 x 30 x 30 cm3 phantom with a dose rate of 320 monitor unit (MU)/min and 50 MU in the case of the dosimetric tests. The acceptance tests verified hardware, network systems integration, data transfer, and software parameters. The results obtained are in good agreement with the specifications of the manufacturer. For the commissioning dosimetric tests, the absolute dose was measured for simple geometries, such as square and rectangular fields, up to more complex geometries such as off-axis hard wedges and for behavior in the build up region. Results were analysed by the use of confidence limit as proposed by Venselaar et al. [Radio Ther. Oncol. 60, 191-201 (2001)]. Criteria of acceptability had been applied also for the comparison between the values of MU calculated manually and MU generated by TPS. The results of the dosimetric tests show that work can be reduced by choosing to perform only those that are more crucial, such as oblique incidence, shaped fields, hard wedges, and buildup region behavior. Staff experience with the implementation of the quality assurance program for a commercial TPS is extremely useful as part of a training program.     

Q-Pro: a quality control management system for medical equipment

Q-Pro is an application for quality control (QC) and inspection of medical equipment. The system has been designed on the basis of a broad requirements analysis, contributed by clinical engineers from several European countries and with a focus on current and forthcoming regulatory requirements concerning the quality control and risk management for medical equipment. Q-Pro comprises a generalized application, providing the necessary flexibility to accommodate the different degrees of difficulty and specialization in creating or customizing QC protocols, carrying out inspections and managing collected data. The system incorporates a tool library for QC protocol design, widely used multimedia as well as a local database for protocol and inventory data archiving. The paper presents a detailed account of the system context of use, design and functionality.     

Q-Pro: a quality control management system for medical equipment

Q-Pro is an application for quality control (QC) and inspection of medical equipment. The system has been designed on the basis of a broad requirements analysis, contributed by clinical engineers from several European countries and with a focus on current and forthcoming regulatory requirements concerning the quality control and risk management for medical equipment. Q-Pro comprises a generalized application, providing the necessary flexibility to accommodate the different degrees of difficulty and specialization in creating or customizing QC protocols, carrying out inspections and managing collected data. The system incorporates a tool library for QC protocol design, widely used multimedia as well as a local database for protocol and inventory data archiving. The paper presents a detailed account of the system context of use, design and functionality.     

Megavoltage CT on a tomotherapy system.

A megavoltage computed tomography (MVCT) system was developed on the University of Wisconsin tomotherapy benchtop. This system can operate either axially or helically, and collect transmission data without any bounds on delivered dose. Scan times as low as 12 s per slice are possible, and scans were run with linac output rates of 100 MU min(-1), although the system can be tuned to deliver arbitrarily low dose rates. Images were reconstructed with clinically reasonable doses ranging from 8 to 12 cGy. These images delineate contrasts below 2% and resolutions of 3.0 mm. Thus, the MVCT image quality of this system should be sufficient for verifying the patient's position and anatomy prior to radiotherapy. Additionally, synthetic data were used to test the potential for improved MVCT contrast using maximum-likelihood (ML) reconstruction. Specifically, the maximum-likelihood expectation-maximization (ML-EM) algorithm and a transmission ML algorithm were compared with filtered backprojection (FBP). It was found that for expected clinical MVCT doses enough imaging photons are used such that little benefit is conferred by the improved noise model of ML algorithms. For significantly lower doses, some quantitative improvement is achieved through ML reconstruction. Nonetheless, the image quality at those lower doses is not satisfactory for radiotherapy verification.     

Analysis of quality control data of eight modern radiotherapy linear accelerators: the short- and long-term behaviours of the outputs and the reproducibility of quality control measurements

Quality control (QC) data of radiotherapy linear accelerators, collected by Helsinki University Central Hospital between the years 2000 and 2004, were analysed. The goal was to provide information for the evaluation and elaboration of QC of accelerator outputs and to propose a method for QC data analysis. Short- and long-term drifts in outputs were quantified by fitting empirical mathematical models to the QC measurements. Normally, long-term drifts were well (< or =1%) modelled by either a straight line or a single-exponential function. A drift of 2% occurred in 18 +/- 12 months. The shortest drift times of only 2-3 months were observed for some new accelerators just after the commissioning but they stabilized during the first 2-3 years. The short-term reproducibility and the long-term stability of local constancy checks, carried out with a sealed plane parallel ion chamber, were also estimated by fitting empirical models to the QC measurements. The reproducibility was 0.2-0.5% depending on the positioning practice of a device. Long-term instabilities of about 0.3%/month were observed for some checking devices. The reproducibility of local absorbed dose measurements was estimated to be about 0.5%. The proposed empirical model fitting of QC data facilitates the recognition of erroneous QC measurements and abnormal output behaviour, caused by malfunctions, offering a tool to improve dose control.     

MRS quality assessment in a multicentre study on MRS-based classification of brain tumours

This paper reports on quality assessment of MRS in the European Union-funded multicentre project INTERPRET (International Network for Pattern Recognition of Tumours Using Magnetic Resonance; http://azizu.uab.es/INTERPRET), which has developed brain tumour classification software using in vivo proton MR spectra. The quality assessment consisted of both MR system quality assurance (SQA) and quality control (QC) of spectral data acquired from patients and healthy volunteers. The system performance of the MR spectrometers at all participating centres was checked bimonthly by a short measurement protocol using a specially designed INTERPRET phantom. In addition, a more extended SQA protocol was performed yearly and after each hardware or software upgrade. To compare the system performance for in vivo measurements, each centre acquired MR spectra from the brain of five healthy volunteers. All MR systems fulfilled generally accepted minimal system performance for brain MRS during the entire data acquisition period. The QC procedure of the MR spectra in the database comprised automatic determination of the signal-to-noise ratio (SNR) in a water-suppressed spectrum and of the line width of the water resonance (water band width, WBW) in the corresponding non-suppressed spectrum. Values of SNR > 10 and WBW < 8 Hz at 1.5 T were determined empirically as conservative threshold levels required for spectra to be of acceptable quality. These thresholds only hold for SNR and WBW values using the definitions and data processing described in this article. A final QC check consisted of visual inspection of each clinically validated water-suppressed metabolite spectrum by two, or, in the case of disagreement, three, experienced MR spectroscopists, to detect artefacts such as large baseline distortions, exceptionally broadened metabolite peaks, insufficient removal of the water line, large phase errors, and signals originating from outside the voxel. In the end, 10% of 889 spectra with completed spectroscopic judgement were discarded.     

Implementation and verification of virtual wedge in a three-dimensional radiotherapy planning system

Virtual Wedge (VW) is a Siemens treatment modality which generates wedge-shaped dose distributions by moving a collimator jaw from closed to open at a constant speed while varying the dose rate in every 2 mm jaw position. In this work, the implementation and verification of VW in a radiotherapy treatment planning (RTP) system is presented. The VW implementation models the dose delivered by VW using the Siemens monitor units (MU) analytic formalism which determines the number of MU required to generate a wedge-fluence profile at points across the VW beam. For any set of treatment parameters, the VW algorithm generates an "intensity map" that is used to model the modification of fluence emanating from the collimator. The intensity map is calculated as the ratio of MU delivered on an axis point, divided by the monitor units delivered on the central-axis MU(0). The dose calculation is then performed using either the Clarkson or Convolution/ Superposition algorithms. The VW implementation also models the operational constraints for the delivery of VW due to dose rate and jaw speed limits. Dose verifications with measured profiles were performed using both the Clarkson and Convolution/Superposition algorithms for three photon beams; Siemens Primus 6 and 23 MV, and Mevatron MD 15 MV. Agreement within 2% or 2 mm was found between calculated and measured doses, over a large set of test cases, for 15, 30, 45, and 60 degree symmetric and asymmetric VW fields, using the manufacturer's supplied mu and c values for each beam.