ABC对肺肿瘤运动和放疗靶区及肺受照射剂量的影响

Study on Effects of Tumor Movements,Target and Irradiation Dose of Lung by Using Active Breathing Control System

目的探讨肺癌3DCRT中应用主动呼吸控制(ABC)技术对肿瘤运动、靶体积变化和肺受照射剂量的影响。方法选择NSCLC患者9例,在模拟定位机下分别测量FB和DIBH-ABC时,肿瘤在左右(X)、前后(Y)和头脚(Z)方向的运动范围,分别在2种呼吸状态下进行3DCRT定位CT扫描,采集图像输入TPS系统,勾画2种状态下肿瘤的GTV、CTV和PTV靶体积和两肺总体积。分别以相同处方剂量、达到最优适形指数(conformal index,CI)为标准,设计3DCRT计划,再以肺V20≤25%、脊髓Dmax≤45Gy为限制条件,进行GTV剂量递增。结果9例患者,在FB状态下X、Y、Z方向上肿瘤的移动度分别为(2.22±0.95)mm、(2.78±1.48)mm、(6.44±4.75)mm;而在DIBH-ABC状态下未观察到肿瘤可测量的移动度。ABC状态下较FB状态下两肺总体积有明显增加,分别为(5980.2±1018.34)cm3和(4338.62±826.27)cm3(P<0.05),PTV体积明显缩小,分别为(252.89±222.75)cm3和(277.52±224.17)cm3(P<0.05),而GTV和CTV无明显变化。GTV处方剂量为60Gy时,肺V20、V30、Dmean在DIBH-ABC状态下均明显低于FB状态,P<0.05。当以肺V20≤25%及脊髓Dmax≤45Gy为限制条件,进行GTV剂量递增,GTV剂量可以增加至100Gy以上的,在DIBH-ABC状态时,9例中有8例;在FB状态下,仅有7例。心脏V45、食管V50在2种呼吸状态下均无显著差异。结论应用深吸气屏气及主动呼吸控制技术,可有效地降低肿瘤随呼吸的移动度,明显缩小PTV体积,并使全肺总体积增加,从而使肺受照射V20、V30、Dmean明显降低。

Objective To explore the impact on lung tumor movement, target volume changes and irradiation dose of lung after the application of ABC system to Precise Radiotherapy for Lung Cancer. Methods Nine patients of NSCLC were enrolled. Respectively measure the tumor＇s range of motion in directions of left-right （X） ,superior-inferior （Y） and cranial-caudal （Z） with the simulated positioning machine when in the situations of FB and DIBH-ABC. CT scans were performed under both the respiration conditions,which transmitting to TPS system, sketch out tumor＇ s target volume of GTV, CTV and PTV and the total volume of the two lungs in both conditions. Take the same prescription dose and optimal CI for the standard scheme conduct 3DCRT scheme. Then conduct dose escalation to GTV when Lung V20 ≤25% ,spinal cord Dmax ≤45 Gy for the restrictions. Results The mean ranges in X, Y and Z directions were （ 2.22 ± 0.95 ）mm, （ 2.78 ±1.48 ） mm, （6.44 ±4.75 ） mm when breathing freely. However,in the condition of DIBH-ABC, tumor movement can＇ t be observed. In the condition of DIBH-ABC, there is a marked increase in the total bilateral lung volume than that in the condition of FB,respectively （5980.2 ±1018.34） cm^3 , （4338.62 ±826.27 ） cm^3 （ P 〈 0. 05 ） , and the PTV volume significantly reduced, respectively （ 252.89 ±222.75 ） cm^3 , （277.52 ±224.17 ）cm^3（ P 〈 0.05 ） , while there was no significant change in GTV and CTV. In granting GTV 60 Gy, take optimal CI as the standard,lung V20 ,V30, Dmean in the condition of ABC was significantly lower than that in the condition of FB, P 〈 0.05. When the lung V20 ≤25% and spinal cord Dmax ≤ 45 Gy,conduct GTV dose increments. In the DIBH-ABC condition,it is 8 of the 9 cases that GTV dose could be increased to more than 100 Gy. In the FB condition,it is 7. For heart V45 and esophagus V50,there was no significant difference in both respiratory conditions. Conclusion Application of the deep inspiration breathhold and active breathing control techniques, effectively reduced the degree of tumor movement resulting from respiration, had significantly narrowed the PTV volume, and increased the total volume of the whole lungs so that irradiation of V20, V30, Dmean on the lungs is significantly reduced.