锥形束CT的常规检测方法和质量保证

目的探讨图像引导放疗中锥形束CT的常规检测方法和质量保证(QA)。方法从加速器中锥形束CT的相关项目验收程序入手,对锥形束CT系统进行日检、周检、月检,完成锥形束CT的系统安全、机械精度、图像质量等项目的质量保证。结果锥形束CT的系统安全性能正常,机械精度和图像质量的误差均在允许范围。锥形束CT的等中心与加速器机架等中心的误差为0.3 mm,SAD检测结果为85.2 cm,均在允许的误差范围内。锥形束CT在OBI模式下2D图像的低对比度分辨率和空间分辨率均合格,CBCT模式下CT图像空间分辨率在Ful-Fan和Half-Fan扫描模式下分别为7 lp/cm和6 lp/cm,低对比度分辨率合格,HU值的线性和一致性均合格,几何失真度小于1 mm,CT图像质量检查均为正常。结论锥形束CT的常规检测和质量保证可确保锥形束CT系统安全、精确。

Routine Measurement Method and Quality Assurance Procedure on Cone-Beam Computed Tomography

Objective To discuss a conventional measurement method and quality assurance （QA） for cone-beam computed tomography （CBCT） in image guided radiotherapy （IGRT）. Methods From the related acceptance procedures of cone-beam CT, daily, weekly, monthly measurements were performed to complete quality assurance program of system security, mechanical precision and image quality for cone-beam CT system. Results Operational safety performance, mechanical precision and image quality of cone-beam CT system were within the allowable range. The average measurement error ofisocenter accuracy for cone-beam system was 0.3 mm, the result of SAD measurement was 85.2 cm, which were within the permissible tolerance range. The 2D image quality tests were normal. The CT image low contrast visibility and HU was normal, the spatial resolution was not less than 7 lp/cm （Ful-Fan）, 6 lp/cm （Half-Fan） respectively, and the geometric distorton was less than 1 mm. The image quality test was normal. Conclusions The conventional measurement and quality assurance of cone-beam CT will ensure safe and accurate cone-beam CT system.