title: MRI-based motion correction of thoracic PET: initial comparison of acquisition protocols and correction strategies suitable for simultaneous PET/MRI systems.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) acquired on equipment capable of simultaneous MRI and positron emission tomography (PET) could potentially provide the gold standard method for motion correction of PET. To assess the latter, in this study we compared fast 2D and 3D MRI of the torso and used deformation parameters from real MRI data to correct simulated PET data for respiratory motion.
  
  
  METHODS
  PET sinogram data were simulated using SimSET from a 4D pseudo-PET image series created by segmenting MR images acquired over a respiratory cycle. Motion-corrected PET images were produced using post-reconstruction registration (PRR) and motion-compensated image reconstruction (MCIR).
  
  
  RESULTS
  MRI-based motion correction improved PET image quality at the lung-liver and lung-spleen boundaries and in the heart but little improvement was obtained where MRI contrast was low. The root mean square error in SUV units per voxel compared to a motion-free image was reduced from 0.0271 (no motion correction) to 0.0264 (PRR) and 0.0250 (MCIR).
  
  
  CONCLUSIONS
  Motion correction using MRI can improve thoracic PET images but there are limitations due to the quality of fast MRI.
authors.affiliation: Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Dikaios
authors.forename: David
authors.initials: D
authors.lastname: Izquierdo-Garcia
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Graves
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Mani
authors.forename: Zahi A
authors.initials: ZA
authors.lastname: Fayad
authors.forename: Tim D
authors.initials: TD
authors.lastname: Fryer
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D009038:Motion; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D012119:Respiration; D013909:Thorax / Q000473:pathology*; D013997:Time Factors; D051598:Whole Body Imaging / Q000379:methods