The effects of set-up errors on dose distribution in radiotherapy treatment for lung cancer

Background: Our aim was to analyze the effects of set-up errors on dose distribution in radiotherapy treatment for lung cancer by using kilovoltage cone-beam CT (CBCT). Materials and Methods: In this study, we used a Varian IX linear accelerator system perform CBCT scans 30 patients before radiotherapy. Subsequently, image matched with planned CT, left right (LR), top bottom (SI), front back (AP) directions were set incorrectly. And CMS planning system, center plan has been moved actual scan. Finally, bed-moving is simulated. We want explore impact target volume setting error (PTV), total tumor (GTV), radiation normal tissues. Results: The LR, SI AP (-0.20±2.84), (-1.09±5.40), (-2.61±2.08) mm, respectively. 5mm accounted 97.8%, 73% 92.6% three directions. Statistically significant differences found 95%PTV dose, average PTV, 95% GTV without bed-moving, compared original plan. Conclusions: clinical radiotherapy, commonly usually less than 5mm, most which are along direction. that related patient's inherent characteristics can significantly change area.