title: Treatment precision of image-guided liver SBRT using implanted fiducial markers depends on marker-tumour distance.
abstract: The purpose of this study is to assess the accuracy of day-to-day predictions of liver tumour position using implanted gold markers as surrogates and to compare the method with alternative set-up strategies, i.e. no correction, vertebrae and 3D diaphragm-based set-up. Twenty patients undergoing stereotactic body radiation therapy (SBRT) with abdominal compression for primary or metastatic liver cancer were analysed. We determined the day-to-day correlation between gold marker and tumour positions in contrast-enhanced CT scans acquired at treatment preparation and before each treatment session. The influence of marker-tumour distance on the accuracy of prediction was estimated by introducing a method extension of the set-up error paradigm. The distance between gold markers and the centre of the tumour varied between 5 and 96 mm. Marker-guidance was superior to guiding treatment using other surrogates, although both the random and systematic components of the prediction error SD depended on the tumour-marker distance. For a marker-tumour distance of 4 cm, we observed σ = 1.3 mm and Σ = 1.6 mm. The 3D position of the diaphragm dome was the second best predictor. In conclusion, the tumour position can be predicted accurately using implanted markers, but marker-guided set-up accuracy decreases with increasing distance between implanted markers and the tumour.
authors.affiliation: Department of Radiation Oncology, Daniel den Hoed Cancer Center, Erasmus Medical Center, Groene Hilledijk 301, 3075 EA Rotterdam, The Netherlands. y.seppenwoolde@erasmusmc.nl
authors.forename: Y
authors.initials: Y
authors.lastname: Seppenwoolde
authors.forename: W
authors.initials: W
authors.lastname: Wunderink
authors.forename: S R
authors.initials: SR
authors.lastname: Wunderink-van Veen
authors.forename: P
authors.initials: P
authors.lastname: Storchi
authors.forename: A
authors.initials: A
authors.lastname: Méndez Romero
authors.forename: B J M
authors.initials: BJ
authors.lastname: Heijmen
mesh_terms: D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000556:secondary; D003964:Diaphragm / Q000000981:diagnostic imaging; D005260:Female; D057918:Fiducial Markers; D006046:Gold / Q000737:chemistry; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D013131:Spine / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D006046:Gold