中文摘要：

目的 探讨适度深吸气呼吸控制（mDIBH）与自由呼吸（FB）两种状态下千伏（KV）X线平片测得术腔中选定银夹位移的差异及其两种呼吸状态下临床靶体积（CTV）外扩到计划靶体积（PTV）边界的差异.方法 比较mDIBH和FB状态下,同一选定银夹不同方向上位移的差异,不同选定银夹在同一方向上位移的差异,左右、头脚、前后各方向上CTV→PTVSb扩边界的差异性.结果 FB状态下,左右、头脚、前后方向最上层银夹与最下层银夹的位移不同[9.7mm与10.6mm（Z=-2.12,P=0.037）、7.3 mm与8.3mm（Z=-2.31,P=0.041）、15.5 mm与16.1 mm（Z=-2.32,P=0.041）],而最近胸壁层银夹与最外侧银夹位移相似[8.6 mm与10.6mm（Z=-0.27,P=0.754）、8.4 mm与8.3 mm（Z=-0.24,P=0.814）、15.7mm与16.5mm（Z=-0.26,P=0.856）];mDIBH状态下,每个银夹不同方向位移不同[5.0 mm与7.8 nun（Z=-2.31,P=0.036）、5.0 mm与9.3 mill（Z=-2.21,P=0.021）、7.8 nun与9.3 mm（Z=-2.11,P=0.041）].FB状态下,不同银夹在左右方向上的位移相似[10.6 mm与10.6 mm（Z=-0.24,P=0.815）],在头脚、前后方向上的位移不同[7.3 mill与8.4 mm（Z=-2.45,P=0.021）、15.5 mm与16.5 mm（Z=-2.41,P=0.043）];mDIBH状态下,不同银夹在左右方向上的位移不同[4.4mm与5.4 mm（Z=-2.31,P=0.031）],而在头脚、前后方向上的位移相似[8.6 mm与8.6 nlnl（Z=-0.21,P=0.815）、10.5 mm与10.8 mm（Z=-0.27,P=0.754）].FB与mDIBH状态间各银夹CTV→PTV外扩边界差异在左右、前后方向均不同[9.7 mm与5.0 mm（Z=-2.34,P=0.029）、15.5 mm与9.3 mm（Z=-2.31,P=0.021）],而在头脚方向上则相似[7.3 mm与7.8 mm（Z=-0.29,P=0.770）].结论 部分乳腺外照射的CTV→PTV靶区边界外扩应依据呼吸状态、边界位置及边界方向区别对待.

英文摘要：

Objective To compare the displacements of the clips in the cavity measured with orthogonal kilovoltage （KV） X-ray plain film in conditions of moderate deep inspiration breathing hold （mDIBH） and free breath （FB）, and compare the margins from clinical target volume （CTV） to planning target volume （PTV） based on the displacements. Methods Before radiotherapy, 2 and 5 sets of orthogonal KV plain film were respectively collected in mDIBH and FB group, then the automatic registration of the reconstructed KV plain film and DRR derived from the planning CT images was finished. In conditions of mDIBH and FB, the displacements of the selected clip at the same location in the different directions and of the different selected clips in the same direction were compared. The margins in three dimensional directions were calculated and compared in conditions of mDIBH and FB . Results In FB group, the difference of displacement in left-right （LR）, cranial-caudal （CC） and anterior-posterior （AP） directions were statistically significant between the clips at the cranial and caudal border of the cavity （9.7 mm and 10. 6 mm （Z = -2. 12,P =0. 037） ,7. 3 mm and 8. 3 mm （Z = -2. 31 ,P =0. 041 ） ,15.5 mm and 16. 1 mm （Z = -2. 32 ,P = 0. 041 ） ）, but not statistically significant for the clips at the bottom and lateral border of the cavity （8.6 mm 与 10. 6 mm（ Z = - 0. 27, P = 0. 754）, 8.4 mm and 8.3 mm（ Z = - 0. 24, P =0. 814）, 15.7 mm and 16. 5 mm （ Z = - 0. 26, P = 0. 856） ）. The corresponding differences in the different directions were statistically significant （ 5.0 mm and 7. 8 mm （ Z = - 2. 31, P = 0. 036 ）, 5.0 mm and 9.3 mm（Z= -2.21,P=0.021）,7.8mmand9.3mm（Z= -2.11,P=0.041））. InFBgroup, the differences of the displacements of the four selected clips were statistically significant in CC and AP directions （7.3 mm and 8.4 mm （Z= -2.45,P=0.021）, 15.5 mm and 16.5 mm （Z= -2.41,P= 0. 043） ）, but not in LF direction （ 10. 6 mm and 10. 6 mm （Z