CT模拟机的质量控制方法研究

发布时间：2018-02-20 16:42

本文关键词： 放射治疗 CT模拟定位机质量控制空间分辨率　出处：《清华大学》2012年硕士论文　论文类型：学位论文

【摘要】：CT模拟定位机是放射治疗的辅助设备，用来模拟放射治疗的几何条件来确定照射部位，CT模拟定位机必须是稳定的、安全的和性能可靠的。没有质量控制和质量保证的CT模拟定位机是毫无意义的，因此建立一套完善的质量控制方法和标准具有十分重要的意义。论文将CT模拟定位机的质量控制大体分为三个部分：电离辐射剂量测量、影像质量评价和几何定位精度检测，这三个部分可以同时实施，也可以根据临床需要建立每日、每周或每月的质量保证程序。本研究使用catphan-500型性能模体、诊断水平剂量仪等质控设备。通过大量实验，首先研究了扫描参数对CT模拟定位机性能的影响，确定了日常质量控制中选择的管电压、管电流、层厚、重建算法等扫描条件，然后从质控设备的使用、检测结果的处理等方面详细描述了CT模拟机质量控制的实施过程。一台合格的CT模拟定位机必须满足以下技术指标： 1．电离辐射剂量：头部和腹部模式剂量限值不同，在规定的扫描条件下，其加权CT剂量指数(CTDIW)头部不超过60mGy，腹部不超过35mGy。 2．影像质量：在规定的扫描条件下，对Catphan-500型性能模体进行成像。CT值的均匀性不超过4.0HU；标准常规重建算法条件下，噪声水平应不大于0.35%；对于多排螺旋CT，图像之间不同层面同一中心位置的CT值偏差应不超过6.0HU；CT值线性偏差一般不超过5.0%；扫描层厚偏差不超过1.0mm（薄层扫描不超过标称值的50%）；空间分辨率应大于5.0线对每厘米；低对比度分辨力，应能分辨密度差为1.0%的模体中直径2.0mm的圆孔。 3．几何定位精度：扫描床的各向移动误差应小于1.0mm；激光定位系统各部分的定位误差小于1.0mm；激光定位系统的重复移动最大误差不超过1.0mm。从肿瘤的定位、治疗计划的设计、剂量分布的计算，到计划的模拟、实施，CT模拟定位机的应用贯穿了放射治疗的全过程，它的性能直接关系到放射治疗的质量。论文充分考虑国内不同型号CT模拟定位机的使用现状，对常用质控设备、质控方法、技术指标等内容进行详细的描述。根据制定的各项质量保证程序对CT模拟定位机进行定期的检测，确保该系统在临床应用中的稳定与安全。实验结果表明，，这套方法简单易行，具有一定的推广价值，为相关国家标准的制定提供了理论参考。
[Abstract]:The CT analog locator is an auxiliary device for radiotherapy. It is used to simulate the geometric conditions of radiation therapy to determine that the irradiation site must be stable. The CT analog positioning machine without quality control and quality assurance is meaningless, so it is very important to establish a set of perfect quality control methods and standards. In this paper, the quality control of CT analog positioning machine is divided into three parts: dose measurement of ionizing radiation, image quality evaluation and geometric positioning accuracy measurement. These three parts can be implemented at the same time, and can also be established daily according to clinical needs. Weekly or monthly quality assurance procedures. In this study, catphan-500 performance motifs, diagnostic horizontal dosimeter and other quality control equipment were used. Through a large number of experiments, the effect of scanning parameters on the performance of CT analog positioning machine was studied. The scanning conditions such as tube voltage, tube current, layer thickness, reconstruction algorithm and so on in daily quality control are determined, and then from the use of quality control equipment, The process of quality control of CT simulator is described in detail. A qualified CT simulator must meet the following technical specifications:. 1. Dose of ionizing radiation: the dose limits of the model of head and abdomen are different. Under the prescribed scanning conditions, the weighted CT dose index (CTDIW) does not exceed 60 mGy in the head and 35 mGyin in the abdomen. 2. Image quality: under specified scanning conditions, the uniformity of imaging. Ct value of Catphan-500 performance motif is not more than 4.0 HU. under standard conventional reconstruction algorithm, The noise level should not be greater than 0.35; for multi-row spiral CTs, the deviation of CT value between different layers in the same central position should not exceed 6.0HUU CT value linear deviation should not exceed 5.0mm generally; the thickness deviation of scanning slice should not exceed 1.0mm (thin layer scan is not more than nominal value). The spatial resolution should be greater than 5.0 lines per centimeter; The low contrast resolution should be able to distinguish circular holes with a diameter of 2.0 mm in a mode with a density difference of 1.0%. 3. Geometric positioning accuracy: the moving error of each direction of scanning bed should be less than 1.0 mm; the positioning error of every part of laser positioning system should be less than 1.0 mm; the maximum error of repeated movement of laser positioning system should not exceed 1.0 mm. From the localization of tumor, the design of treatment plan, the calculation of dose distribution, to the simulation of plan, the application of CT simulator runs through the whole process of radiotherapy. Its performance is directly related to the quality of radiotherapy. In order to ensure the stability and safety of the system in clinical application, the experimental results show that this method is simple and feasible. It has certain popularizing value and provides a theoretical reference for the formulation of relevant national standards.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：R318.6

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