Helical tomotherapy for non-small cell lung cancer: A dosimetric study

Objective To investigate the dosimetric characteristics of helical tomotherapy（HT） for non-small-cell lung cancer（NSCLC）. Methods CT images,tumor target area and normal organs were selected respectively from 5 patients with central NSCLC and 5 patients with ambient NSCLC to design the HT and IMRT treatment plans.The prescription dose was 70Gy/33F and 60Gy/33F for CTV and CTVnd,respectively.The dose limit was ＜45Gy for spinal cord,＜30% for V20 of the total lung,and ＜50% for V50 of the heart and V55 of the esophagus.Differences in the two plans were compared. Results The dose homogeneities were better in HT plan for ambient NSCLC group.The dose limit was over 60% and close to 60% for V5 of lung in ambient NSCLC group and central NSCLC group,respectively.The dose limit was considerably lower for V20-V30 of the ambient NSCLC group and for V25 of the central NSCLC group after HT.The maximum doses for spinal cord,heart,esophagus and trachea were lower in HT plan than in IMRT plan with no significant difference between the two plans. Conclusion HT plan can give better dose uniformity,dose gradient and healthy tissue savage than IMRT plan.HT plan can reduce the irradiated volume with medium-high doses in patients with NSCLC.However,the increased irradiated volume with low dose needs further investigation.