基于四维CT的呼吸门控技术分析呼吸运动对肺部肿瘤的影响

目的：探讨应用呼吸门控技术行三维放疗的肺部肿瘤患者受呼吸影响后靶区几何中心在三维方向上的矢量变化。方法采用放疗专用Phlipis 16排大孔径 CT定位机对48例需行胸部放疗、已行真空气垫体位固定的肺癌患者行辅以瓦里安实时位置管理系统的4D-CT模拟定位扫描，将每个呼吸周期的 CT图像平均分为10个呼吸时相。每个时相勾画靶区，融合10个时相的CT图像，测定靶区中心点在三维方向上的最大运动矢量并进行分析。结果（1）在平静呼吸状态下，肺的呼吸动度在 X轴方向（左右）、Y轴方向（前后）、Z轴方向（头脚）分别为1．97、2．33、8．41 mm；方向精度分别为1．31、1．50、1．92 mm；平均误差分别为（1．00＆#177;1．28）mm、（1．19＆#177;1．49）mm、（1．67＆#177;1．89）mm ，三维方向的呼吸动度差异有统计学意义（χ2＝6．773，P ＝0．034）。（2）病灶位于左、右肺的呼吸动度在 X轴方向（左右）、Y轴方向（前后）、Z轴方向（头脚）分别为1．96和1．99 mm （t ＝0．79，P ＝0．94），2．49和2．18 mm （t＝0．72，P ＝0．48），8．49和8．18 mm （t＝1．21，P ＝0．23）；三维方向的呼吸动度差异无统计学意义。结论呼吸门控技术可以定量测定肺部肿瘤受呼吸运动影响在三维方向的移动范围。

Influence of respiratory motion based on 4 dimensional-CT for lung cancer

Objective To analyze the three-dimensional vector changes of gross target volume（GTV）geo-metrical center of lung cancer patients receiving conformal radiotherapy （3-DCRT）using respiratory mo-tion,to determine the range,guide GTV＆#39;s drawing and improve the radiotherapy precision.Methods 48 cases who need chest radiotherapy,have already been fixed,received the scan by Phlipis 1 6 rows big bore CT simulation machine assisted by 4 dimensional-CT simulation scan,divide the CT image of each respira-tory period into 10 respiratory time phases.Draw GTV of each time phase,registrate the 10-time-phase CT images,measure and analyze the maxium three-dimensional motion vector changes of the GTV center. Results In the calm respiratory suitation,the lung respiratory motion is 1.97 mm,2.33 mm and 8.41 mm in the X,Y,Z direction respectively,while the direction precision is 1.31 mm,1.50 mm and 1.92 mm re-spectively,there are statistical differences （χ2=6.773,P=0.034）.The lung respiratory motion in left and right lung is 1.96 mm,1.99 mm （t=0.79,P =0.94）,2.49 mm,2.18 mm（t=0.72,P=0.48）,8.49 mm, 8.18 mm （t=1.21,P=0.23）in the X,Y,Z direction respectively,there are no statistical differences.Con-clusion It is possible to test lung cancer′s three-dimensional vector changes by using during respiratory motion.The definition of internal target volume margin for lung.