鼻咽癌IMRT中气腔对靶区及OAR剂量影响  

Dosimetric effects of air cavity on target volume and organs at risk during intensity.modulated radiation therapy for nasopharyngeal carcinoma

作　　者：刘志萍[1,2] 田源[1] 王洪智[1] 罗京伟[1] 高黎[1] 徐国镇[1] 

机构地区：[1]国家癌症中心/中国医学科学院肿瘤医院北京协和医学院放疗科,北京100021 [2]哈尔滨医科大学附属第一医院肿瘤科,150001

出　　处：《中华放射肿瘤学杂志》2017年第8期862-866,共5页Chinese Journal of Radiation Oncology

基　　金：北京协和医学院研究生创新基金（2014-1002-3001）

摘　　要：目的明确IMRT中气腔效应对鼻咽癌患者原发肿瘤及OAR受照射剂量影响。方法选择鼻咽癌患者9例，放疗前及放疗第25次分别接受CT定位扫描。在放疗前CT图像上勾画靶区及OAR，制定计划planl。复制planl，将此放疗前cT图像与放疗第25次CT图像融合。在放疗前CT图像上勾画靶区退缩后形成的空腔并将空腔的密度强制设为0，并将放疗前勾画的靶区减去空腔体积形成新靶区，此CT图像命名为CTAir。使用planl计划的设野及计划参数，在CT。上计算剂量分布，形成放疗计划plan2。假设planl和plan2分别被全程使用，配对t检验比较有气腔和无气腔情况下原发肿瘤及OAR受量。结果有气腔情况下肿瘤Dmaan、D95,D90,D10,D5较气腔出现前增加（P=0．000、0．001、0．001、0．001、0．005），剂量增加〈0．5Gy。气腔后方肿瘤区见剂量建成效应，最大剂量在气腔后方1．4cm处，剂量差值为0．36Gy。出现气腔后脑干D2cr及D1cr高于气腔出现之前（P=0．036、0．044）。视交叉、左视神经、右视神经Dmax在出现气腔后较前增高（P=0．438、0．434、0．477），剂量增加〈0．12Gy。结论鼻咽癌IMRT中气腔效应使原发肿瘤及OAR受量增高较小可忽略不计，但要注意放疗前OAR已经接近或超过耐受剂量者。Objective To evaluate the dosimetric effects of air cavity on primary tumor and organs at risk （OARs） during intensity-modulated radiation therapy （IMRT） for nasopharyngeal carcinoma patients. Methods Nine patients with nasopharyngeal carcinoma had CT simulation before treatment and on the 25 fraction of radiotherapy. Radiotherapy planl was first created by delineating the target volumes and OARs on the first CT image, which was then copied and merged with the second CT image. Air cavity that was formed following tumor volume regression was delineated on the first CT image, and the density of air cavity was set to zero. A new gross target volume （GTV） was formed by subtracting the air cavity from the original GTV, and the new CT image was named CTAir. Plan2 was then created by calculating the dose distribution on CTAir using the same portals and parameters as Planl. Assuming that Planl and Plan2 were both used throughout the course of radiotherapy, the dosimetric parameters of nasopharyngeal tumor and OARs in the absence and presence of air cavity were then compared using the paired t-test. Results Dmean , D95, D90, Dl0, and D5 of tumor were significantly higher in plan2 than in planl （P= O. 000, 0. 001, 0. 001, 0. 001, and 0. 005, respectively） , with a〈O. 5 Gy increase in dose. A dose build-up effect was observed within the tumor region posterior to the air cavity, where the highest dose was 1.4 cm posterior to the air cavity, resulting in a dose difference of O. 36 Gy. In addition, D2, and D10, of the brain stem were significantly higher in plan2 than in plan l （P= 0. 036 and 0. 044, respectively）. Dmax of the optical chiasm, left optical nerve, and right optical nerve were also increased in the presence of air cavity （P=0. 438, 0. 434, and 0. 477, respectively）, but the change in dose was〈0. 12 Gy. Conclusions Air cavity induces a small but negligible increase in the tumor and OARs dose in patients with nasopharyngeal carcinoma during IMRT. However, closer monitoring should be cond

关 键 词：鼻咽肿瘤/调强放射疗法 气腔效应 危及器官 

分 类 号：R730.55[医药卫生—肿瘤] R739.63[医药卫生—临床医学]