title: A population-specific symmetric phase model to automatically analyze susceptibility-weighted imaging (SWI) phase shifts and phase symmetry in the human brain.
abstract: OBJECTIVE
  To create a population-specific symmetric phase model and to evaluate the susceptibility-weighted imaging (SWI) phase in terms of phase shift using different segmentation methods (manual and automatic) and phase shift symmetry, which is expected as a marker for lateralized Parkinson's disease (PD) symptoms.
  
  
  METHODS
  SWI and T(1)-weighted data from 25 PD patients and five healthy controls were acquired on a 3T MRI system. A population-specific, symmetric phase model was developed. Regions of interest (ROIs) were defined manually on the phase model, manually on each individual data set, and automatically using model-based segmentation (MBS). Manually- and MBS-defined ROIs were compared using kappa values, and left-right phase symmetry was evaluated using correlation analysis.
  
  
  RESULTS
  Independent of the analysis method, a phase increase from the anterior to the posterior putamen, and the average phase value relationship substantia nigra > globus pallidus > red nucleus was found. Phase symmetry analysis shows a difference between lateralized and symmetric PD.
  
  
  CONCLUSIONS
  The symmetric phase model helps to analyze phase data with similar accuracy, but a greatly reduced tracing effort compared to individual tracing and also allows evaluating left-right phase symmetries.
authors.affiliation: Department of Radiology, Medical University of Vienna, Vienna, Austria.
authors.forename: Günther
authors.initials: G
authors.lastname: Grabner
authors.forename: Dietrich
authors.initials: D
authors.lastname: Haubenberger
authors.forename: Jakob
authors.initials: J
authors.lastname: Rath
authors.forename: Roland
authors.initials: R
authors.lastname: Beisteiner
authors.forename: Eduard
authors.initials: E
authors.lastname: Auff
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.forename: Markus
authors.initials: M
authors.lastname: Barth
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D010300:Parkinson Disease / Q000175:diagnosis*; D011699:Putamen / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity