Evaluating the impact of respiratory motion on lung dosimetry using 4D-CT for non-small cell lung cancer / 中华放射医学与防护杂志

ABSTRACT

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.