鼻咽癌调强放疗中解剖位置变化对剂量分布的影响

Influence of anatomical changes on dose distribution in inasopharyngeal carcinoma with intensity-modulated radiation therapy

目的 研究鼻咽癌（NPC）患者调强放疗中解剖结构改变及对剂量分布的影响。方法 选取2015年1-8月江西省赣州市肿瘤医院收治的15例NPC患者,放疗第16、21次后重复CT扫描,计算临床靶体积（GTVnx、GTVnd、CTV1、CTV2）和危及器官体积,及剂量分布变化。结果 与初始CT相比,放疗16与21次后GTVnx的体积平均分别缩小20.7%和33.9%（P〈0.05）,GTVnd平均缩小31.0%和45.5%（P〈0.05）,CTV1平均缩小3.5%和6.8%（P〈0.05）,CTV2平均缩小6.2%和9.2%（P〈0.05）;左腮腺体积缩小22.2%和33.9%（P〈0.05）,右腮腺体积缩小23.5%和34.5%（P〈0.05）,脑干体积、脊髓体积无明显变化。与初始计划比,放疗16和21次后GTVnx的D95分别平均增加了-1.7%、-0.6%;GTVnd的D95分别增加了1.9%、-1.2%;左腮腺Dmean分别增加了2.9、5.0 Gy,右腮腺的Dmean分别增加了3.0、4.6 Gy;脑干的Dmax分别增加了0.1、0.3 Gy,脊髓的Dmax分别增加0.3、1.4 Gy。结论 NPC患者在调强放疗过程中靶区和腮腺的体积均随治疗剂量增加而显著缩小,除了腮腺的剂量显著增加外,靶区GTVnx、GTVnd剂量分布差异无统计学意义,脑干和脊髓的最大剂量无显著升高。

Objective To research the anatomy changes during intensity-modulated radiation therapy （IMRT） of patients with nasopharyngeal carcinoma （NPC） and its effect on the dose distribution.Methods Fifteen patients with NPC treated in tumor hospital of Ganzhou city in Jiangxi province from January to August 2015,at the 16^th and 21^th radiotherapy CT scanning were scaned by the same conditions as the initial CT simulation and at the same time CT and CT of the initial registration were repeated.Clinical target volume（GTVnx,GTVnd,CTV1,CTV2） and volume of the endanger organs,change of dose distribution were calculated.Results Compared with the initial CT,Volume of GTVnx were reduced 20.7% and 33.9% at 16^th and 21^th after IMRT （P〈0.05）,GTVnd were reduced 31.0% and 45.5%（P〈0.05）,CTV1 were reduced 3.5% and 6.8% （P〈0.05）,CTV2 were reduced 6.2% and 9.2% （P〈0.05）;Volume of the left parotid glands were reduced 22.2% and 33.9% （P〈0.05）,volume of right parotid gland were reduced 23.5% and 34.5%（P〈0.05）.Volume of brain stem and spinal cord was no obvious changes.Compared with the initial plan,at 16^th and 21^th after IMRT,D95 of GTVnx was increased -1.7% and -0.6%,D95 of GTVnd was increased 1.9% and-l.2%;Dmean of left parotid gland was increased 2.9,5.0 Gy,Dmean of right parotid gland was increased 3.0,4.6 Gy,brain stem was increased 0.1,0.3 Gy on Dmax,spinal cord increased 0.3,1.4 Gy on Dmax.Conclusion The volume of target and parotid gland during IMRT in NPC are significantly reduce with the increase of treatment dose,except dose of parotid gland increasing significantly,dose distribution of target GTVnx,GTVnd have not much difference,the maximum dose of brain stem and spinal cord slightly increases.