目的：比较鼻咽癌放疗中患者解剖结构改变对 IMRT 和 RapidArc 计划剂量影响的大小。方法：选取鼻咽癌患者6例，分别设计 IMRT 和 RapidArc 计划。在疗程的第五周再次行 CT 扫描，在第五周 CT 图像上重新勾画靶区和危及器官。分别将 IMRT 和 RapidArc 计划移植到第五周 CT 图像上，保持所有参数不变，重新计算剂量分布，并与原计划的剂量分布进行比较。结果：两种计划 PGTVnx 和 PTV1的最大剂量、最小剂量、平均剂量、两腮腺的平均剂量的变化量均无明显差异，脑干、脊髓的最大剂量变化量两种计划存在明显差异：第五周 IMRT 计划脑干的最大剂量较原计划增加了（2.98±2.53）Gy，RapidArc 计划只增加了（1.16±1.39） Gy；第五周 IMRT 计划脊髓的最大剂量较原计划增加了（4.72±2.41）Gy，RapidArc 计划只增加了（1.67±1.20）Gy，两者均有统计学差异（P ＜0.05）。结论：放疗过程中患者解剖结构的变化会导致靶区和危及器官剂量分布较原计划产生一定变化，相比 IMRT 计划而言，RapidArc 计划的剂量分布受患者解剖结构变化的影响较小。在鼻咽癌放疗中采用 RapidArc 技术可减少脑干、脊髓随患者解剖结构变化带来的剂量偏差，提高剂量传递的准确性。%Objective:To compare the dose distribution deviation of nasopharyngeal carcinoma(NPC)IMRT and RapidArc due to patient anatomical changes. Methods:Six NPC cases were planned with the same dose prescription and objective constrains by means of IMRT and RapidArc respectively. Repeat CT scan in the fifth week and recontour treatment targets and organs at risk with repeated CT images. Dose distributions were recalculated with repeated CT images and compared to the original plans. Results:There were no significant differences in the deviation of the maxi-mum,minimum,mean dose of PGTVnx and PTV1,the mean dose of parotids between IMRT and RapidArc plan. But the differences in the deviation of the maximum dose of stem,spinal cord were significant(P < 0. 05):Compared to the original plans,the maximum dose of brainstem of IMRT plan increased(2. 98 ± 2. 53)Gy,while RapidArc plan in-creased(1. 16 ± 1. 39)Gy;The maximum dose of spinal cord of IMRT plan increased(4. 72 ± 2. 41)Gy,while Rapi-dArc plan increased(1. 67 ± 1. 20)Gy. Conclusion:The dose distributions of treatment targets and organ at risk would vary comparing with the original plan due to patient anatomical changes during radiation treatment. Compared to IMRT,the patient anatomical changes have less effects to RapidArc. The RapidArc can reduce the dose deviation of brainstem and spinal cord due to patient anatomical changes,improve the accuracy of dose delivery.
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