[摘要] 目的 用胶片（film）测量调强放射治疗（IMRT）多叶光栅叶片到位精确度验证方法研究，为质量核查方法提供数据支持。方法 选择物理师水平较高的6家医院，8台加速器（瓦里安、医科达、西门子）参与验证研究。25 cm×25 cm的放射性免冲洗胶片放在30 cm×30 cm厚的均质固体模体上，厚度2.0 cm的固体模体板覆盖在胶片上面，经CT扫描，影像传给放射治疗计划系统（TPS）制定治疗计划，多叶光栅形成5条栅栏野条状，能量6 MV X射线束，每条栅栏野3 cm×0.6 cm，条状野间隔3 cm，在最大剂量点处，胶片到源距离100 cm，每条栅栏野给出监督剂量250 MU。照射计划传输到加速器上进行照射，照射后的胶片一周内返回国际原子能机构（IAEA）进行分析和计算，并与IAEA给出的限值比较。结果 胶片测量与TPS计划每条多叶光栅栅栏野条状位置偏差±0.5 mm内为合格。7台加速器结果均在±0.5 mm范围内，符合要求。1台加速器结果超出±0.5 mm，不符合要求。胶片测量每对与每条所有多叶光栅叶片位置标准偏差±0.5 mm内为合格。8台加速器胶片测量每对与每条所有多叶光栅叶片位置标准偏差结果均在±0.5 mm内，符合IAEA要求。胶片测量每对与每条所有多叶光栅叶片实际宽度差值±0.75 mm内为合格，7台加速器结果均<±0.75 mm，符合要求，1台加速器结果>±0.75 mm，不符合要求。胶片测量每对与每条所有多叶光栅叶片实际宽度标准偏差0.3 mm内为合格。7台加速器结果 < 0.3 mm，合格，1台加速器结果为0.5 mm，不合格。结论 河南省部分加速器多叶光栅片到位精确度不合格，应定期开展相关的质量保证工作和第三方核查工作，对保证放射治疗剂量的精确实施具有重要意义。

[Abstract] Objective To measure the positioning accuracy of multi-leaf collimators (MLC) leaves by using radiochromic films, with aim to providing data in support of IAEA's methodology validation. Methods The present study focused on 8 accelerators (Varian, Elekta and Siemens machines) at 6 hospitals in Henan province with highly skilled physicists. The 25 cm×25 cm radiochromic films were put on 30 cm×30 cm homogeneous solid phantoms and covered with a 2.0-cm-thick homogeneous solid phantom slabs. The CT-scanned images were transmitted to TPS for plan formulation. With 6 MV X-ray, MLC created 5 strip 3 cm×0.6 cm picket fence field, each with 3.0 cm strip separation. The SSD was 100 cm at the maximum dose point, with a 250 MU to each strip. The irradiated radiochromic films were returned to IAEA for analysis within one week and compared with the values given by IAEA. Results The difference of film-measured and TPS-planned positions of MLC leaves for each strip picket fence should be within ±0.5 mm as required by IAEA. For 7 of 8 accelerators selected, the differences of accurately measured MLC leaf positions were all within ±0.5 mm, which were in line with the IAEA requirements, with only other one being beyond -0.5 mm, not consistent with the IAEA requirements. The differences of film-measured actual widths between each pair and all pairs of leaves were within ±0.75 mm as required by IAEA for 7 accelerators, whereas the other one was outside ±0.75 mm, not consistent with the IAEA requirements. The standard deviation of film-measured actual width of MCL leaf between each pair and all pairs for 7 accelerators were ≤ 0.3 mm as required by IAEA, whereas the other one was 0.5 mm, not consistent with IAEA requirements. Conclusions The MLC positioning accuracy of a few of medical accelerators in Henan is not qualified. It is of great significance to carry out regular quality examination as well as third-party verification to ensure precise delivery of radiotherapy.