title: Impact of 4D image quality on the accuracy of target definition.
abstract: Delineation accuracy of target shape and position depends on the image quality. This study investigates whether the image quality on standard 4D systems has an influence comparable to the overall delineation uncertainty. A moving lung target was imaged using a dynamic thorax phantom on three different 4D computed tomography (CT) systems and a 4D cone beam CT (CBCT) system using pre-defined clinical scanning protocols. Peak-to-peak motion and target volume were registered using rigid registration and automatic delineation, respectively. A spatial distribution of the imaging uncertainty was calculated as the distance deviation between the imaged target and the true target shape. The measured motions were smaller than actual motions. There were volume differences of the imaged target between respiration phases. Imaging uncertainties of >0.4 cm were measured in the motion direction which showed that there was a large distortion of the imaged target shape. Imaging uncertainties of standard 4D systems are of similar size as typical GTV-CTV expansions (0.5-1 cm) and contribute considerably to the target definition uncertainty. Optimising and validating 4D systems is recommended in order to obtain the most optimal imaged target shape.
authors.affiliation: Laboratory of Radiation Physics, Odense University Hospital, 5000, Odense, Denmark. tine.bjoern.nielsen@rsyd.dk.
authors.forename: Tine Bjørn
authors.initials: TB
authors.lastname: Nielsen
authors.affiliation: Laboratory of Radiation Physics, Odense University Hospital, 5000, Odense, Denmark.
authors.forename: Christian Rønn
authors.initials: CR
authors.lastname: Hansen
authors.affiliation: Laboratory of Radiation Physics, Odense University Hospital, 5000, Odense, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Westberg
authors.affiliation: Department of Oncology, Odense University Hospital, Odense, Denmark.|Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Olfred
authors.initials: O
authors.lastname: Hansen
authors.affiliation: Laboratory of Radiation Physics, Odense University Hospital, 5000, Odense, Denmark.|Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Brink
mesh_terms: D054893:Cone-Beam Computed Tomography; D016001:Confidence Intervals; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D007089:Image Enhancement; D008175:Lung Neoplasms / Q000000981:diagnostic imaging; D019047:Phantoms, Imaging
keywords: 4D-CBCT; 4D-CT; Image artefact; Motion management; NSCLC; Target motion