title: Correction of head movement on PET studies: comparison of methods.
abstract: Head movement presents a continuing problem in PET studies. Head restraint minimizes movement but is unreliable, resulting in the need to develop alternative strategies. These include frame-by-frame (FBF) realignment or use of motion tracking (MT) during the scan to realign PET acquisition data. Here we present a comparative analysis of these 2 methods of motion correction.
  
  
  METHODS
  Eight volunteers were examined at rest using (11)C-raclopride PET with the radioligand administered as a bolus followed by constant infusion to achieve steady state. Binding potential (BP) was estimated using the ratio method during 2 periods of the scan at steady state. Head movement was compensated by using coregistration between frames (FBF) and 3 methods using MT measurements of head position acquired with a commercially available optical tracking system.
  
  
  RESULTS
  All methods of realignment improved test-retest reliability and noise characteristics of the raw data, with important consequences for the power to detect small changes in radiotracer binding, and the potential to reduce false-positive and false-negative results. MT methods were superior to FBF realignment using coregistration on some indices.
  
  
  CONCLUSIONS
  Such methods have considerable potential to improve the reliability of PET data with important implications for the numbers of volunteers required to test hypotheses.
authors.affiliation: CSC-MRC Cyclotron Unit, Imperial College, Hammersmith Hospital, London, UK. andrew.montgomery@imperial.ac.uk
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Montgomery
authors.forename: Kris
authors.initials: K
authors.lastname: Thielemans
authors.forename: Mitul A
authors.initials: MA
authors.lastname: Mehta
authors.forename: Federico
authors.initials: F
authors.lastname: Turkheimer
authors.forename: Sanida
authors.initials: S
authors.lastname: Mustafovic
authors.forename: Paul M
authors.initials: PM
authors.lastname: Grasby
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000000981:diagnostic imaging*; D019416:Head Movements; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity