CTVision图像引导系统分析调强放疗过程中鼻咽癌患者腮腺的体积及剂量学变化规律

摘要

目的：应用 CTVision 图像引导系统观察鼻咽癌患者行调强放疗时腮腺体积及剂量学的变化规律。方法选取45例行调强放射治疗的鼻咽癌患者，分别于放疗的第1、2、3、4周末应用CTVision系统行CT图像引导扫描，将CT图像上传至放疗计划系统，勾画腮腺，观察其体积的变化规律；将放疗前治疗规划复制到每个CT图像上，计算腮腺的剂量分布，总结其剂量学变化规律。结果双侧腮腺体积均随放疗进程的延长而缩小（P＜0．05），放疗结束时，左、右侧腮腺体积较放疗前分别缩小35．16％和32．37％；双侧腮腺照射剂量均随放疗过程的延长而增加（P＜0．05），左、右侧腮腺照射剂量较放疗前所设计的照射剂量分别增加7．81％～35．24％、10．26％～46．61％；双侧腮腺所受的剂量增加幅度与腮腺体积缩小幅度呈正相关（P＜0．05）。结论鼻咽癌行调强放疗时，腮腺体积随着放疗进程延长向内侧呈进行性缩小，导致腮腺所受的放疗剂量较原放疗计划剂量明显增加。%Objective To observe the laws of volume and dosimetric variations of parotid gland during intensity-modulated radiation therapy by CTVision image-guided system in patients with nasopharyngeal carcinoma.Methods Forty-five patients with nasopharyngeal carcinoma who planned to undergo intensity-modulated radiation therapy were selected.And image-guided CT scan by CTVision system was conducted in the 1st,2nd, 3rd,4th week of radiotherapy respectively.The CT images were transmitted to therapy planning system,then the parotid gland was sketched and the variation law of volume was observed.The therapy planning before radiotherapy was copied to each CT image ,then the dose distribution of parotid gland was calculated and the variation law of dose was summarized.Results The volumes of bilateral parotid glands diminished with the progress of the radiation(P<0.05).Compared to the volumes before radiotherapy,the volumes of left and right parotid glands decreased by 35.16%and 32.37%respectively.The exposure doses of bilateral parotid glands increased with the progress of the radiation (P<0.05).Compared to the doses planned before radiotherapy,the exposure doses of left and right parotid glands increased by 7.81%-35.24% and 10.26%-46.61% respectively.The increase range of exposure dose positively correlated with the decrease range of volume in bilateral parotid glands (P<0.05).Conclusion The volume of parotid gland diminishes progressively with the progress of the radiation during the intensity-modulated radiation therapy for nasopharyngeal carcinoma,which can lead to the increasing exposure dose of parotid gland compared to the previous radiotherapy plan .