Movement of pulmonary lesion and diaphragm in stereotactic radiotherapy for lung cancers / 中华放射肿瘤学杂志

ABSTRACT

Objective To study the range of movement of pulmonary lesion and diaphragm in stereotactic radiotherapy for lung cancers. Methods We measured the range of movement in 48 lung cancer patients. The movement at different locations of the lung varied. The change in tumor volume from the reconstructed three dimensional (3D) images during respiration as measured by a respiratory simulator was observed. Results The movement was smaller in upper parts of lung in the X and Y directions (0.2?0.06)～(0.20?0.11 )?cm. The movement of the lower field of lung was larger than that of the upper fields (0.31?0.10)～(0.36?0.10)?cm. This is due to the heart and aortic pulsation. However, the movement was the largest in the Z direction (0.9? 0.45 )～(0.93?0.46)?cm. Moreover, if the time of computed tomography (CT) scan for each slice of lung tissue was equal to or longer than the interval of a breathing cycle, the tumor information was not lost. The reconstructed 3D images involved all the movements. The size of reconstructed 3D images changed inversely with the breathing movement. Conclusions The affection of breathing movement in lung cancer is chiefly in the Z direction. If the time of CT scan is equal to or longer than the interval of a breathing cycle, the reconstructed 3D images will encompass all the information of the tumor and its movement, showing the gross tumor volume (GTV) which does not need any safety margin. If the time of CT is shorter than the breathing cycle like the spiral CT, the reconstructed 3D image can not show the range of tumor movement.