Investigating the reproducibility of motion for lung tumours treated with stereotactic body radiotherapy

Abstract

Purpose: Breathing induced target motion may influence the accuracy of radiotherapy treatment - especially for stereotactic body radiotherapy. The work will focus on reproducibility of tumour motion which was acquired before and during radiation therapy. Methods: Two imaging techniques were used to determined tumour motion of 27 target volumes of 24 patients via 4D computer tomography (4DCT) and portal image system (EPID). EPID movies were analyzed by means of motion amplitude. Motion amplitude was calculated by the difference of tumour position in maximum inspiration and maximum expiration. Results: The evaluation of the EPID movies showed that 48 % and 22 % of investigated target volumes were moving more than 5 mm and 10 mm, respectively. A strong correlation was seen between motion determined in 4DCT and EPID movies (CC 0.87). Conclusion: Tumour motion acquired in 4DCT and portal image movies showed good correlation. For some target volumes large deviations of motion amplitudes were observed. © 2009 Springer-Verlag.