title: An iterative projection-based motion estimation and compensation scheme for head x-ray CT.
abstract: OBJECTIVE
  Although current computed tomography (CT) systems can scan the head in a very short time, patient motion sometimes still induces artifacts. If motion occurs, one has to repeat the scan; to avoid motion, sedation or anesthesia is sometimes applied.
  
  
  METHODS
  The authors propose a method to iteratively estimate and compensate this motion during the reconstruction. In every iteration, the rigid motion was estimated view-by-view and then used to update the system matrix. A multiresolution scheme was used to speed up the convergence of this joint estimation of the image and the motion of the subject. A final iterative reconstruction was performed with the last motion estimate.
  
  
  RESULTS
  The method was evaluated on simulations, patient scans, and a phantom study. The quality of the reconstructed images was improved substantially after the compensation. In simulation and phantom studies, root-mean-square error was reduced and mean structural similarity was increased. In the patient studies, most of the motion blurring in the reconstructed images disappeared after the compensation.
  
  
  CONCLUSIONS
  The proposed method effectively eliminated motion-induced artifacts in head CT scans. Since only measured raw data are needed for the motion estimation and compensation, the proposed method can be applied retrospectively to clinical helical CT scans affected by motion.
authors: Department of Imaging and Pathology, KU Leuven-University of Leuven, Nuclear Medicine and Molecular Imaging, Medical Imaging Research Center (MIRC), Leuven B-3000, Belgium.
authors: Tao
authors: T
authors: Sun
authors: Faculty of Health Sciences, University of Sydney, NSW 2006, Australia.
authors: Jung-Ha
authors: JH
authors: Kim
authors: Faculty of Health Sciences, University of Sydney, NSW 2006, Australia and Department of Medical Physics, Westmead Hospital, Westmead, NSW 2145, Australia.
authors: Roger
authors: R
authors: Fulton
authors: Department of Imaging and Pathology, KU Leuven-University of Leuven, Nuclear Medicine and Molecular Imaging, Medical Imaging Research Center (MIRC), Leuven B-3000, Belgium.
authors: Johan
authors: J
authors: Nuyts
mesh_terms: D016477:Artifacts; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D009068:Movement; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed