用主动呼吸控制提高肺癌图像引导放疗精度

Active breath coordinator enhances the precision of image guided radiotherapy for lung cancer

目的增加使用主动呼吸控制(ABC)系统时屏气时间,结合使用图像引导放疗(IG- RT)提高肺癌患者放疗精度。方法对31例肺癌患者行主动呼吸控制系统训练,训练屏气时接入氧,训练5 d,每日训练约30 min。训练时充分发挥患者的主观能动性,让患者熟练掌握屏气技巧,主动配合治疗。采用立体定向体架固定(SBF),用IGRT的SynergyTM系统锥形束CT(CBCT)与ABC系统配合进行治疗。结果31例中训练后最大屏气时间达40 s以上的24例,平均最大屏气时间为65.5 s,较训练前增加33.9 s。使用ABC时横膈在头脚方向运动平均为1.7 mm,而在自由呼吸时为16.0 mm。首次CBCT采集图像与计划图像比较在左右(x)、头脚(y)、前后(z)方向平均误差分别为3.3、4.8、3.1 mm,调整床后分别为1.0、1.2、1.1 mm。结论通过吸入氧气屏气的呼吸训练,能明显延长患者屏气时间。在IGRT中配合使用ABC系统,可使肺部肿瘤放疗精度控制在2 mm,为提高分次剂量和总治疗剂量,减少肺损伤提供可能。

Objective To prolong breath holding time by using active breath coordinator （ABC） and to improve the precision of image guide radiotherapy （IGRT） for lung cancer. Methods Thirty - one patients with lung cancer were trained for breath holding with inhalation of 61% oxygen for approximately 30 minutes every day, at least 5 days totally. Results The maximal breath holding time over 40 seconds was observed in 24 patients （77%） after training. The average maximal breath holding time was 65.5 seconds, which was 33.9 seconds longer than that before training. The average motions of the diaphragm in GT direction using ABC and free breathing were 1.7 mm and 16.0 mm. The average errors in AB,GT and AP directions were 3.3 ram,4.8 mm and 3.1 mm for the first setup. After adjusting the isocenter, the errors were reduced to 1.0 mm, 1.2 mm and 1.1 mm. Conclusions The breath holding time can be markedly extended by breath training and inputting oxygen. When combined with active breath coordinator, the precision of image guide radiotherapy for lung cancer is less than 2 mm, which makes it possible to increase fraction dose and total dose while decrease lung damages.