目的：比较分析肝癌旋转容积调强放疗（ VMAT）计划与固定野调强放疗（ IMRT）计划靶区及其周围危机器官的剂量学差异。方法选择36例肝癌患者的CT图像数据，分别设计VMAT计划、IMRT计划，比较两者的靶区剂量分布、危及器官受量、正常组织受量、机器跳数及治疗时间等。结果 VMAT计划的靶区剂量最大值比IMRT计划低（ Z=2.090，P<0.05）；VMAT计划的90%的处方剂量的适形指数比IMRT计划小（Z=2.809，P<0.05）；VMAT计划的正常肝组织的V30低于IMRT计划（Z=2.395，P<0.05）；VMAT计划的正常肾脏组织的V20低于 IMRT计划（Z=2.201，P<0.05）；VMAT计划机器跳数是 IMRT计划的<40%，治疗时间低于IMRT计划的50%。结论2种治疗计划在剂量学上均能满足临床要求，并且剂量分布基本一致，VMAT计划的适形指数比IMRT好，危及器官剂量比IMRT计划略有降低，正常组织的低剂量区VMAT计划与IMRT相比有先高后低的趋势，并且机器跳数少，治疗时间短，更值得临床推广应用。%Objective To compare the dosimetric differences of the target volume and the surrounding organ at risk between volumetric modulated arc radiotherapy( VMAT)and fixed field intensity-modulated radiation therapy ( IMRT)plans for liver cancer. Methods The CT image data of 36 patients with liver cancer were observed,the VMAT plan and the IMRT plan were designed,the target dose distribution of the two plans,organs at risk affected by quantity ,normal tissue by volume ,the number of machine unit and treatment time of the two plans were compared .Results The maximum value in the target region of the VMAT plan was lower than that of the IMRT plan( Z=2. 090,P<0. 05);the conformal index of 90% of prescription dose in the VMAT plan was smaller than that in the IMRT plan(Z=2. 809,P<0. 05);the V30 of liver in the VMAT plan was lower than that in the IMRT plan(Z=2. 395,P<0. 05);the V20 of kidney in the VMAT plan was lower than that in the IMRT plan( Z=2. 201,P<0. 05);the machine unit in the VMAT plan was 40% of that in the IMRT plan,the treatment time in the VMAT plan was lower than 50% in the IMRT plan. Conclusion Two kinds of treatment plan can satisfy the clinical re-quirements on dosimetry and dose distribution;conformal index of the VMAT plan is better than IMRT plan;dose of organs at risk in the VMAT plan is lower than that in the IMRT plan;compared with the IMRT plan,low dose area of normal tissues in the VMAT plan has the tendency of high after the first low,and the less machine units,the short treatment time.
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