Objective To estimate the appropriate margins for the planning target volume( PTV )in non - small cell lung cancer 3DCRT. Methods Eight non - small cell lung cancer patients under - went 3DCRTor IMRT. kV - CBCT scan was acquired on couch before and after radiotherapy. The analysis of these images was performed by automatic and manual regist ration of the kV - CBCT and planning CT images. The patient setup was then corrected by moving the couch accordingly. CBCT online - guided correction data were recorded. Results A total of 160 CBCT sets of 8 non - small cell lung cancer patients were analyzed. If the online image guidance was not corrected,the distance hetween the clinical target volume and the planning target volume was 10.9 mm;lf every online image guided radiotherapy was corrected,the distance between them was 2.2 mm. Conclusion There is some extent of setup error in non - small cell lung cancer 3DCRT or IMRT. The approach based on the CBCT measurements can be used to reduce the impact of setup error obviously and to estimate the required margins for PTV.%目的 探讨非小细胞肺癌三维适形放射治疗临床靶区的外放范围.方法 8例非小细胞肺癌患者均采用三维适形放疗或调强放疗.分次放疗前、后患者在治疗床上进行锥形束CT扫描,并将锥形束CT图像与计划CT图像进行在线配准,根据配准得到的平移矢量调整治疗床的位置,从而修正摆位误差,并分别记录各个方向上平移矢量.结果 8例患者共计160组配准数据.如果放射治疗过程中未进行在线图像引导校正,在实际应用中临床靶区外放10.9mm;如果每次放射治疗均进行在线图像引导校正,在实际应用中临床靶区外放2.2mm.结论 非小细胞肺癌三维适形调强放疗时具有一定的摆位误差.基于锥形束CT图像分析的在线校正方法能减小该摆位误差,并有助于确定合适的临床靶区外放.
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