title: Combined magnitude and phase-based segmentation of the cerebral cortex in 7T MR images of the elderly.
abstract: OBJECTIVE
  To propose a new method that integrates both magnitude and phase information obtained from magnetic resonance (MR) T*(2) -weighted scans for cerebral cortex segmentation of the elderly.
  
  
  METHODS
  This method makes use of K-means clustering on magnitude and phase images to compute an initial segmentation, which is further refined by means of transformation with reconstruction criteria. The method was evaluated against the manual segmentation of 7T in vivo MR data of 20 elderly subjects (age = 67.7 ± 10.9). The added value of combining magnitude and phase was also evaluated by comparing the performance of the proposed method with the results obtained when limiting the available data to either magnitude or phase.
  
  
  RESULTS
  The proposed method shows good overlap agreement, as quantified by the Dice Index (0.79 ± 0.04), limited bias (average relative volume difference = 2.94%), and reasonable volumetric correlation (R = 0.555, p = 0.011). Using the combined magnitude and phase information significantly improves the segmentation accuracy compared with using either magnitude or phase.
  
  
  CONCLUSIONS
  This study suggests that the proposed method is an accurate and robust approach for cerebral cortex segmentation in datasets presenting low gray/white matter contrast.
authors.affiliation: Division of Image Processing, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Nhat Trung
authors.initials: NT
authors.lastname: Doan
authors.forename: Sanneke
authors.initials: S
authors.lastname: van Rooden
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Versluis
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Webb
authors.forename: Jeroen
authors.initials: J
authors.lastname: van der Grond
authors.forename: Mark A
authors.initials: MA
authors.lastname: van Buchem
authors.forename: Johan H C
authors.initials: JH
authors.lastname: Reiber
authors.forename: Julien
authors.initials: J
authors.lastname: Milles
mesh_terms: D000368:Aged; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology*; D002540:Cerebral Cortex / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity