IGRT系统的质量保证和质量控制

目的：结合我院开展IGRT技术以来所做的质量保证和质量控制工作所积累的经验，分析和探讨IGRT系统的主要质控检测项目和实现方法，以保证系统安全、有效、稳定的进行。方法：检测图像系统的低对比度分辨力、空间分辨率、密度均匀性和几何失真度，测试系统的图像匹配精度，校准六自由度治疗床系统（Hexa PODTM evo System）的等中心。结果：能分辨的图像低密度差异值小于2％，空间分辨率不小于71p／cm，表征图像密度均一性的像素值差异小于2％，表征图像几何失真度的几何精度在X、Y、Z方向均小于1．04mm，XVI系统随机架运动时，旋转中心由于重力作用引起的位置变化范围在X、Y方向上小于1．04mm，KV级系统中心和MV级系统中心的位置差异在X、Y、Z方向上小于0．5mm。六自由度治疗床相对于等中心的偏差在0．2mm、0．2。以内。结论：相应的质控项目和方法保证了我院IGRT系统得以安全、稳定的运行，也有助于减小病人治疗过程中由于系统误差而引起的摆位误差。

Quality assurance and quality control of IGRT system

Objective： With the accumulated experience from the quality assuranceand quality control work that our institute has done since the beginning of IGRT technology, the major quality control and monitoring programs and realization methods in IGRT system are analyzed and discussed, to ensure the safe, efficient and stable operation. Methods： The image low contrast visibility, spatial resolution, uniformity and the geometry accuracy of the imaging system were detected, the registration accuracy of the system was tested, the isocenter of the six-degree couch was calibrated. Results： The image low contrast visibility was below 2%, the spatial resolution was no less than 71p/ cm, the deviation of the pixel value which indicates the image uniformity was below 2%, the geometry accuracy which represents the degree of image distortion was below 1.04mm in X, Y, Z directions, respectively. When the XVI system rotates with the gantry, the deviation of rotation isocenter due to gravity was below 4pixel; the deviation between the KV system and MV system was below 0.5mm in X, Y, Z directions, respectively. The deviation between the six-degree couch and the isocenter was within 0.2mm, 0.2°. Conclusion： The corresponding quality control programs and methods could ensure the operational safety and stability, and helped to minimizing the setup errors during the patients＇ radiotherapy.