主动呼吸控制系统在非小细胞肺癌精确放疗中的应用

Application of Active Breathing Control System to Precise Radiotherapy for Non-small Cell Lung Cancer

背景与目的:呼吸运动是影响非小细胞肺癌放射剂量提升的重要因素。本研究观察使用主动呼吸控制(activebreathingcontrol,ABC)系统对非小细胞肺癌原发肿瘤运动的影响,研究其在精确放疗中减少放射性肺损伤方面作用。方法:选择ⅢA～Ⅳ期周围型肺鳞癌或腺癌患者7例,使用ABC系统控制呼吸进行三维适形放疗定位及治疗,在患者吸气量达到平静呼吸最大吸气量的80%时强制屏气,分别计算分次放疗时、分次放疗间的肿瘤运动范围,保持相同体位患者平静呼吸,重复扫描计算出平静呼吸时的肿瘤运动范围。制定适形放疗计划,比较两种状态下内边界、V20、Dmean、大体靶区(grosstargetvolumol,GTV)的体积及双侧肺的体积(totalvolume,TV)的不同,用t检验进行统计学分析。结果:7例患者在主动呼吸控制时分次放疗时左右方向(X)、前后方向(Y)和头脚方向(Z)的运动幅度分别为(0.79±0.45)mm、(0.98±0.52)mm、(0.50±0.75)mm,分次放疗间的三维方向的运动幅度分别为(0.91±0.69)mm、(1.02±0.77)mm、(0.74±1.0)mm,平静呼吸(freebreathing,FB)时的三维运动幅度分别为(1.09±0.61)mm、(1.71±0.82)mm、(2.73±1.08)mm。分别制定ABC和FB状态下的放疗计划,其DVH显示V20分别为(10.0±3.7)%、(17.0±6.5)%(P=0.015),Dmean分别为(539±247)cGy、(844±390)cGy(P=0.012),GTV的体积分别为(26.1±22.0)cm3、(30.0±23.9)cm3(P=0.02),双肺的总体积分别为(3522.8±1020.0)cm3、(3240.7±876.7)cm3(P=0.045)。结论:使用ABC系统控制呼吸,可有效缩小肿瘤运动幅度和内边界,缩小周围型肺癌周围正常组织的受照体积;使用吸气期屏气进行定位和放射治疗,可增加全肺体积,从而降低受照射肺组织的密度,减少放射性肺损伤的发生率。

BACKGROUND ＆ OBJECTIVE： Breathing is one major factor which affects the dose used in the treatment of non-small cell lung cancer （NSCLC）. This study was to observe the influence of active breathing control （ABC） system on the motion of primary tumor of non-small cell lung cancer and investigate the effect of ABC on the reduction of radioactive damage of lungs during precise radiotherapy. METHODS： Seven patients with stage Ⅲ A and IV peripheral lung cancer, whose pathology were either squamous cell carcinoma or adenocarcinoma, were enrolled. The patients receiving threedimensional conformal radiotherapy controlled by ABC system held their breath when their inspiratory volume reached 80% of the maximum. The moving ranges of tumor in intra- and inter-fractions during radiotherapy were calculated respectively. The tumor moving ranges of patients who accepted repeated CT scans when breathing freely in the same position were calculated. Internal margin, V2, Dmean, volume of G＇IV and total volume of bilateral lung were calculated by treatment planning system and compared by t-test. RESULTS： The mean ranges in left-right （X）, superior-inferior （Y） and cranial-caudal （Z）directions were （0.79 ±0.45）mm, （0.98±0.52） mm, （0.50＋0.75）mm in intra-fractional radiotherapy and （0.91 ＋0.69）mm, （1.02±0.77）mm, （0.74±1.0）mm in inter-fractional radiotherapy respectively when patients used ABC system; while the ranges were （1.09±0.61）mm, （1.71±0.82）mm, （2.73±1.08）mm respectively when patients breathed freely. V20 were （10.0±3.7）% and （17.0±6.5）% （P=0.015）; Dmeen were （539±247） cGy and （844±390） cGy （P=0.012）; the volumes of GTV were （26.1±22） cm^3 and （30.0±23.9）cm^3 （P=0.02）, and total bilateral lung volume were （3522.8±1020）cm^3 and （3240.7±876.7）cm^3 （P=0.045） respectively under ABC and free breathing condition. CONCLUSIONS： The tumor moving ranges and internal margins are reduced by holding the patients＇ breath by ABC system, which reduces the volume of normal tissues around peripheral lung tumor during radiotherapy. In addition, total lung volumes are enlarged when patients holding their breath while inhaling, which can reduce the density of iradiated lungs, and thus the incidence of radioactive lung damage is decreased accordingly.