The Quantification of Intra-Fractional Tumour Motion Errors in Lung Stereotactic Ablative Radiotherapy Patients

Abstract

This work aims at quantifying intra-fractional motion errors and evaluating the appropriateness of a Planning Target Volume (PTV) margin for Queen Elizabeth (QE) Hospital’s patients. Intra-fractional motion errors were quantified for 29 patients who underwent lung Stereotactic Ablative Radiotherapy (SABR) treatment at the cancer centre of QE Hospital. One hundred thirty post-Cone Beam Computed Tomography (CBCT) scans were collected to calculate these errors. In terms of the adequacy of a PTV margin, the intra-fractional motion errors that were calculated are combined with other geometric errors which were taken from historical audit studies. Then, the combined outcome was compared with the common PTV margin that is delineated by most United Kingdom (UK) oncology centres. The findings of this study showed that the systematic component of intra-fractional motion error is equal to 0.08, 0.08 and 0.08 cm in right/left, superior/anterior and anterior/posterior directions, respectively, While the random component of this error is equal to 0.11, 0.13 and 0.14 cm. In addition to that, a PTV margin of 0.5 cm is the appropriate margin for QE Hospital’s patients and this volume is compatible with the common PTV margin that is delineated by the most UK oncology centres. This work concluded that A PTV margin of 0.5 cm is the suitable volume for lung SABR patients at QE Hospital.