应用4D-CT对非小细胞肺癌由呼吸运动所致肺受量变化的研究

Evaluating the impact of respiratory motion on lung dosimetry using 4D-CT for non-small cell lung cancer

目的 使用4D-CT评估在肺癌的放射治疗中呼吸运动对肺受量的影响.方法 选取本院10例非小细胞肺癌患者.在治疗前行4D-CT扫描定位,每例患者均获取10个呼吸时相的CT图像序列,在最大密度投影（MIP）图像中勾画靶区,在平均密度投影（AIP）图像中制定计划,然后将计划移植到其他时相图像中计算肺受量,评估肺和体内的绝对剂量体积.结果 肺平均剂量受到呼吸运动的影响很大,不同肿瘤位置时其影响差异较大,当肿瘤位于肺内部时,平均剂量与肺体积变化趋势相同,幅度2.18％显著小于肺体积的变化4.49％（t=4.189,P＜0.05）,当肿瘤位于肺边缘时,肺平均剂量与肺体积变化趋势相反,变化幅度3.76％,小于肺体积的变化4.49％（仁25.007,P＜0.05）.呼吸运动对体内V5、V10和V20影响很小,体内剂量变化幅度相应为0.47％、0.28％、0.17％,均小于肺体积的变化4.49％（t=11.371、11.188、11.377,P＜0.05）.肺体积量V5、V10和V20与肺体积变化趋势相同,幅度分别为2.39％、1.91％、1.80％,均小于肺体积的变化4.49％（t=2.279、2.298、2.485,P＜0.05）.结论 肺的平均剂量随呼吸运动变化明显,在制定计划时要更加谨慎评估肺受量.

Objective To evaluate the impact of respiratory motion on lung dosimetry using 4D-CT during lung cancer radiotherapy.Methods Ten cases were randomly selected from non-small cell lung cancer （NSCLC） patients treated in our department.The 4D-CT machine was adopted for simulation before treatment and 10 respiratory phases were obtained for each patient.Target volumes were delineated on the maximum intensity projection （MIP） images,and plans were generated on average intensity projection （ALP） images.Plans were transferred to CT images of each respiratory phase,and we calculated the dosage on lungs and subsequently evaluated the volume dosage to lungs and the entire body.Results The mean dosage to lungs are greatly affected by the respiratory phase.This difference also depended on tumor location.When it was inside the lung,the average dosage shows the same trend as the respiratory motion,with the change rate of 2.18%,which was less than the change of lung volume 4.49% （t =4.189,P 〈 0.05）.When the tumor was located nearby the lung,the mean dosage showed the opposite trend with respiratory motion,with the change rate of 3.76%,which was also less than the change of lung volume 4.49% （t =25.007,P 〈 0.05）.The effect of respiratory motion on V5,V10,V20 of body was small,and the magnitude of change for whole body dosages were 0.47%,0.28%,0.17% respectively,which was smaller than the change of lung volume 4.49% （t =11.371,11.188,11.377,P 〈 0.05）.Volume dose of lung V5,V10,V20 and lung volume change trends were the same,and the magnitude of change for lung volume dosages were 2.39%,1.91%,1.80% respectively,and were smaller than the change of lung volume 4.49% （t =2.279,2.298,2.485,P 〈 0.05）.Conclusions The mean dosage to lungs shows a great difference between different respiratory phases.More attention should be paid when evaluating the lung volume during treatment planning.