中文摘要：

目的千伏特平片引导测定自主呼吸控制（ABC）辅助适度深吸气呼吸控制（mDIBH）状态下术腔中银夹位移以探讨保乳术后ABC辅助三维适形部分乳腺外照射（EB—PBI）临床靶区（CTV）外扩到计划靶区（PTV）的边界。方法ABC辅助行CT模拟定位扫描，获取mDIBH状态CT图像，分别勾画和标记术腔中4个选定银夹及所有银夹构成的术腔作为肉眼靶区（GTV）。每次治疗前获取ABC辅助mDIBH状态下2次正交平片，每次获取平片先与计划数字重建影像片进行自动匹配，在此基础上进行手动匹配，获得选定银夹在左右（LAT）、上下（LNG）、前后（VRT）各个方向位移数据，并依数据计算各个选定银夹在LAT、LNG、VRT各个方向上由CTV外扩到PTV所需边界大小。结果最上层银夹LAT、LNG、VRT三个方向由CTV到PTV的外扩边界分别为5．00、7．78、9．30mm，最近胸壁层银夹为4．40、6．43、6．73mm，最外侧银夹为5．04、8．63、10．54mm，最下层银夹为5．40、8．59、10．81mm。结论术腔中银夹可清晰显示在干伏特平片上，ABC辅助mDIBH状态下平片与计划数字重建影像片自动加手动配准可准确显示银夹的位移，为EB—PBI的PTV边界确定提供了依据。

英文摘要：

Objective To measure the displacement of the silver clips guided by kV-plain film at state of moderate deep inspiration hold（mDIBH） assisted by active breathing control （ABC） and to explore the margin of clinical target volume（CTV） to planning target volume（PTV） for breast cancer patients treated with three-dimensional eonformal external-beam partial breast irradiation （EB-PBI） assisted by ABC. Methods The patients undertook CT simulation assisted by ABC to get the CT images on the respiratory condition of mDIBH. Four selected silver clips in breast cavity were delineated and the cavity based on all of the clips were delineated as gross tumor volume （GTV）. Before each irradiation, two orthogonal kV-plain films were taken for the patients in the respiratory condition of mDIBH assisted by ABC device. 2D-2D auto- matic registration was performed based on pixel between the kV-plain films and the digital reconstructed radiographs（DRR）. Then manual registration was undertook to get the shifts of the four clips separately at LAT, LNG, and VRT directions. Based on the shift data, the margins of CTV to PTV at LAT, LNG and VRT direc- tions were calculated. Results The margins from CTV to PTV were 5.00 mm ,7.78 mm and 9.30 mm at LAT, LNG and VRT directions based on the clip at cephal border of the cavity. The corresponding margins were 4.40 mm,6.43 mm and 6.73 mm based on the clip at bottom of the cavity;5.04 mm,8.63 mm and 10.54 mm based on the clip at lateral border of the cavity;5.40 mm,8.59 mm and 10.81 mm based on the clip at pedal border of the cavity. Conclusions The silver clips in breast cavity can be clearly showed on the kV-plain film. The displacement of the clips can be exactly measured by registration of kV-plain film and planning DRR in condition of mDIBH assisted by ABC. The margins from CTV to PTV for EB-PBI can be calculated based on the displacement of the clips.