自由与主动呼吸控制状态下乳腺癌调强放疗位移EPID误差比较

目的:应用电子射野影像系统测量自由呼吸状态(FB)和主动呼吸控制状态(ABC)下的相对位移,并对比其差别。方法:选择29例接受保留乳房术后调强放疗的乳腺癌患者,16例在FB下13例在ABC下接受放疗。患者在每次放疗前拍电子射野影像片(EPI),ABC的8例在每次放疗前拍2次。依据胸壁和乳腺表面轮廓将EPI和数字重建图像(DRR)进行配准,计算出每次配准时垂直和水平方向的差异。结果:FB组水平和垂直方向的平均位移分别为1.93和0.99mm,ABC组分别为1.97和1.14mm。位移>5mm的<4%。ABC组之间在水平和垂直方向的位移差异无统计学意义,P值分别为0.778和0.142。其中8例每次放疗前拍2次EPI的ABC患者,在水平和垂直方向差异无统计学意义,P值分别为0.220和0.862。结论:尽管从理论上ABC可减少呼吸运动,但在减少由摆位误差和呼吸运动造成的混合位移方面并无优势。乳腺癌放疗时从临床靶区到计划靶区外放5mm的边界是合理的。

Comparison of displacement between FB and ABC condition measured by electronic portal imaging device in breast radiotherapy

OBJECTIVE:To measure the displacement respectively in condition of free breath(FB) and active breathing control(ABC) using electronic portal imaging device(EPID),and compare the difference of the displacement between FB and ABC.METHODS: Twenty nine breast cancer patients receiving IMRT after breast-conserving surgery were enrolled in the study.Electronic portal imaging(EPI) was performed for all patients in FB group(n=16) and ABC group(n=13) before each irradiation at the position of the two main tangential...