title: Revised motion estimation algorithm for PROPELLER MRI.
abstract: OBJECTIVE
  To introduce a new algorithm for estimating data shifts (used for both rotation and translation estimates) for motion-corrected PROPELLER MRI. The method estimates shifts for all blades jointly, emphasizing blade-pair correlations that are both strong and more robust to noise.
  
  
  METHODS
  The heads of three volunteers were scanned using a PROPELLER acquisition while they exhibited various amounts of motion. All data were reconstructed twice, using motion estimates from the original and new algorithm. Two radiologists independently and blindly compared 216 image pairs from these scans, ranking the left image as substantially better or worse than, slightly better or worse than, or equivalent to the right image.
  
  
  RESULTS
  In the aggregate of 432 scores, the new method was judged substantially better than the old method 11 times, and was never judged substantially worse.
  
  
  CONCLUSIONS
  The new algorithm compared favorably with the old in its ability to estimate bulk motion in a limited study of volunteer motion. A larger study of patients is planned for future work.
authors.affiliation: Barrow Neurological Institute, Phoenix, Arizona, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Pipe
authors.forename: Wende N
authors.initials: WN
authors.lastname: Gibbs
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li
authors.forename: John P
authors.initials: JP
authors.lastname: Karis
authors.forename: Michael
authors.initials: M
authors.lastname: Schar
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Zwart
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: MRI; PROPELLER; motion