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

This work aims at quantifying intra-fractional motion errors and evaluatingthe appropriateness of a Planning Target Volume (PTV) margin for QueenElizabeth (QE) Hospital’s patients. Intra-fractional motion errors werequantified for 29 patients who underwent lung Stereotactic AblativeRadiotherapy (SABR) treatment at the cancer centre of QE Hospital. One hundredthirty post-Cone Beam Computed Tomography (CBCT) scans were collected tocalculate these errors. In terms of the adequacy of a PTV margin, theintra-fractional motion errors that were calculated are combined with othergeometric errors which were taken from historical audit studies. Then, thecombined outcome was compared with the common PTV margin that is delineated bymost United Kingdom (UK) oncology centres. The findings of this study showedthat the systematic component of intra-fractional motion error is equal to0.08, 0.08 and 0.08 cm in right/left, superior/anterior and anterior/posteriordirections, respectively, While the random component of this error is equal to0.11, 0.13 and 0.14 cm. In addition to that, a PTV margin of 0.5 cm is theappropriate margin for QE Hospital’s patients and this volume is compatiblewith 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 lungSABR patients at QE Hospital.