旋转摆位误差对调强放疗剂量准确性的影响

Impact of rotational set-up error in dose veracity of intensity-modulated radiotherapy

目的:分析旋转摆位误差对调强放疗剂量准确性的影响。方法:随机选取10例鼻咽癌患者的适形调强放疗(intensity-modulated radiation therapy,IMRT)计划,以患者放疗计划做模板计划(template plan,TP),然后分别旋转治疗床角度为±0.5、±1、±1.5、±2、±2.5、±3、±3.5、±5°形成不同的模拟计划(simulate plan,SP),利用Omni Pro-IMRT软件对SP与TP进行比较,观察不同旋转角度在3%/3 mm标准下对gamma值的影响。结果:在旋转误差≤1.5°时,gamma值之间无统计学意义(P>0.05);旋转角度≥2°时,gamma值之间有统计学意义(P<0.05)。沿相反方向旋转相同角度后,gamma值之间无统计学意义(P>0.05)。结论:旋转摆位误差对靶区剂量准确性的影响与靶区长度有关;旋转误差的校正阈值为1.5°可能更为合理。

Objective To analyze the effect of the rotational set-up error in dose veracity of intensity-modulated radiotherapy. Methods Totally 10 IMRT treatment plans of nasopharyngeal carcinoma patients were selected for the study. The template plans （TP） were designed with the treatment plans. Then the couch was rotated at ±0.5, ±1, ±1.5, ±2, ±2.5, ±3, ±3.5 and ±5° to create the simulate plans （SP）. OmniPro-IMRT was used to compare the influences of gamma indexes with different rotate angles between SP vs TP. Then the gamma values were analyzed to evaluate these influences. Results The gamma values of different rotational set-up errors in 3%/3 mm were as follows： when the rotation set-up error was not more than 1.5°, there had no significant differences （P〉0.05）, while had significant differences when the rotation set-up error was not less than 2° （P〈0.05）. The gamma values with the same rotate degree at the opposite directions had no significant difference （P〉0.05）. Conclusion The influence of the rotational position error on the accuracy of the target dose is related to the target length. Rotation set-up error correction threshold of 1.5° may be reasonable.