CT模拟软件的质量保证

Quality Assurance for CT-simulation Software

目的:CT-SIM模拟软件作为几何模拟的重要工具,其精确度和完整性应是目前三维立体放射治疗中首要考虑的问题之一。本文旨在研究和探讨CT模拟软件的质量保证和质量控制(quality assurance and quality control,QA&QC)的检测方法。材料与方法:利用飞利浦BrillianceTMCT模拟机对QUASARTM模体和QUASAR多叶准直器束流几何模体分别实施扫描,通过在ACQSim工作站软件中来实现以下几项质控检测:(1)等中心计算和空间/几何精度检测;(2)图像重建精度测试;(3)DRR几何精确度的评估;(4)射野几何学和MLC精度的测量。结果:(1)用QUASAR模体检测模拟软件等中心计算及空间/几何计算精度,偏差均小于1mm。(2)所测量的模体插件体积与标称值相比较:大正方体为1.24%,小正方体为1.76%,楔形空腔体积为2.1%,大球体相差-0.44%,中球体为0.56%,小球体为13.68%。(3)在DRR图像中测量出最里面的丙烯酸材料的矩形面积为0.9cm×1.9cm,中间空气腔矩形面积为10cm×9.9cm,外面丙烯酸材料的矩形面积为14.7cm×14.8cm。(4)照射野的MLC与模体的几何精度误差基本保持在±1mm精度。结论:CT模拟软件的QA在CT模拟定位系统质量保证中应占有十分重要地位,其直接影响到放疗定位的精确度和治疗的准确性。

Objective： With the CT-simulation software being an important tool for the geometry simulation, its accuracy and integrity should be firstly considered. The purpose of this study is to provide a series of methods about quality assurance and quality control for CT-simulation software. Material and Methods： The QUASAR and QUASAR^TM MLC Beam Geometry phantom were scanned independently by using Philips Brilliance^TM CT simulator. In the ACQSim workstation, there were the following measurements to be done. （1）The isocenter calculation and the spatial/geometry accuracy tests. （2）The accuracy tests for the image reconstruction. （3）Evaluation of the digitally reconstructed radiographs（DRRs）. （4） Evaluation of the accuracy of beam and MLC. Results： （1）To evaluate the isocenter calculation and the spatial/geometry accuracy using QUASAR phantom, make sure that the tolerance limits were within ±1mm. （2）The comparison with the measured and nominal values showed that, the error was 1.24% for the big cube. And the errors for the small cube were 1.76%, 2.1% for the wedge cavity, - 0.44% for the big sphere, 0.56% for the middle sphere and 13.68% for the small sphere. （3） The measured values of the inner acrylic rectangle, the air square and the outer acrylic square were 0.9 cm ×1.9 cm, 10cm×9.9cm, and 14.7cm×14.8 cm respectively. （4）The errors between the field sizes and the phantom geometry were kept within ±1 mm. Conclusions： Quality assurance of CT-Simulation software plays an extremely important part in the CT-Simulation system. And its results would directly influence the accuracy of patient setup and the precision of radiation treatment.