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目的:比较旋转调强(intensity-modulated arc radiotherapy,IMAT)与固定野动态调强(dynamic intensitymodulated radiation therapy,dIMRT)在T2期鼻咽癌放射治疗计划中的剂量学差异。方法:随机选取10例已经接受固定野动态调强放射治疗的T2期鼻咽癌病例,将这10例放疗计划改为旋转调强方式,重新进行计划优化,比较两种计划的等剂量分布、靶区和危机器官的剂量参数、机器跳数以及治疗时间等。结果:两种计划的靶区剂量分布D98、D95以及D2等参数均无统计学差异(P>0.05),IMAT计划的脑干Dmax和D1cc、脊髓Dmax、右腮腺Dmean、右颞颌关节Dmax以及左中耳Dmean和Dmax均明显小于dIMRT计划的受量(P<0.05);同时IMAT计划的左右晶体Dmax、左右视神经Dmax和视交叉Dmax均明显大于dIMRT计划的受量(P<0.05)。IMAT计划正常组织受照剂量为5Gy的总体积明显大于dIMRT计划(P<0.05),而受照剂量在20Gy和30Gy的总体积明显小于dIMRT计划(P<0.05)。IMAT比dIMRT计划的单次照射总机器跳数平均减少了47.0%,单次照射时间平均减少48.2%。结论:对于T2期鼻咽癌,两种计划的剂量分布均满足临床要求,在靶区剂量分布没有统计学差异的情况下,IMAT技术能显著降低机器跳数,大大缩短治疗时间。
OBJECTIVE: To compare the dosimetry differences of intensity-modulated arc radiotherapy (IMAT) and dynamic intensity modulated radiation therapy (dIMRT) in radiotherapy of T2-stage nasopharyngeal carcinoma. Methods: Totally 10 cases of stage T2 nasopharyngeal carcinoma who had undergone dynamic field intensity modulated radiation therapy were randomly selected. The 10 cases of radiotherapy were changed to rotating intensity modulation mode, and then the plan was optimized again. The isodose distribution of the two plans was compared, Target and critical organ dose parameters, machine hops and treatment time. Results: There was no significant difference in dose distribution D98, D95 and D2 between the two plans (P> 0.05), Dmax and D1cc in brainstem, Dmax in spinal cord, Dmean in parotid gland, Dmax in right temporomandibular joint, Dmean and Dmax in the left middle ear were significantly lower than those in the dIMRT plan (P <0.05). Meanwhile, the left and right optic nerve Dmax, left and right optic nerve Dmax, and optic chiasm Dmax in IMAT were significantly greater than those in dIMRT (P <0.05). The total volume of IMAT normal tissue irradiated dose 5Gy was significantly larger than that of dIMRT (P <0.05), while the total dose of 20 Gy and 30Gy dose was significantly less than that of dIMRT (P <0.05). IMAT reduced the number of hops by 47.0% on average for a single shot of the dIMRT program and reduced the average duration of single shots by 48.2%. CONCLUSIONS: For T2 stage nasopharyngeal carcinoma, both planned dose distributions meet clinical requirements. IMAT technique significantly reduces the number of machine hops and shortens the duration of treatment when the target dose distribution is not statistically different.