title: On-the-fly motion-compensated cone-beam CT using an a priori motion model.
abstract: Respiratory motion causes artifacts in slow-rotating cone-beam (CB) computed tomography (CT) images acquired for example for image guidance of radiotherapy. Respiration-correlated CBCT has been proposed to correct for the respiratory motion, but the use of a subset of the CB projections to reconstruct each frame of the 4D CBCT image limits their quality, thus requiring a longer acquisition time. Another solution is motion-compensated CBCT which consists of reconstructing a single 3D CBCT image at a reference position from all the CB projections by using an estimate of the respiratory motion in the reconstruction algorithm. In this paper, we propose a method for motion-compensated CBCT which allows to reconstruct the image on-the-fly, i.e. concurrent with acquisition. Before the CB acquisition, a model of the patient motion over the respiratory cycle is estimated from the planning 4D CT. The respiratory motion is then computed on-the-fly from this model using a respiratory signal extracted from the CB projections and incorporated into the motion-compensated CBCT reconstruction algorithm. The proposed method is evaluated on 26 CBCT scans of 3 patients acquired with two protocols used for static and respiration-correlated CBCT respectively. Our results show that this method provides CBCT images within a few seconds after the end of the acquisition where most of the motion artifacts have been removed.
authors.affiliation: The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Department of Radiation Oncology, The Netherlands. j.sonke@nki.nl
authors.forename: Simon
authors.initials: S
authors.lastname: Rit
authors.forename: Jochem
authors.initials: J
authors.lastname: Wolthaus
authors.forename: Marcel
authors.initials: M
authors.lastname: van Herk
authors.forename: Jan-Jakob
authors.initials: JJ
authors.lastname: Sonke
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D003199:Computer Systems; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging*; D008954:Models, Biological; D009038:Motion; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D013382:Subtraction Technique