title: Influence of white matter fiber orientation on R2* revealed by MRI segmentation.
abstract: OBJECTIVE
  To investigate white matter heterogeneity using a multichannel segmentation of a large sample of structural and diffusion magnetic resonance imaging (MRI) data.
  
  
  METHODS
  A sample of 50 subjects was segmented using channels comprising exclusively structural (longitudinal and transverse relaxation times T1 and T2 and transverse relaxation rate R2*) and diffusion-based MRI indices (mean diffusivity and fractional anisotropy). These data were analyzed using a data driven approach in which no prior information was used.
  
  
  RESULTS
  The analysis revealed the splitting of white matter into two subclasses in which the longitudinal fasciculi were distinguished from inferior/superior ones. The distribution of the adopted indices in the obtained clusters showed that R2* was mainly responsible for this splitting.
  
  
  CONCLUSIONS
  This result supports the observation, previously hypothesized in the literature, that R2* is influenced by the fiber orientation.
authors.affiliation: Institute for Advanced Biomedical Technologies, Department of Neuroscience and Imaging, G. D'Annunzio University, Chieti, Italy. f.depasquale@unich.it
authors.forename: Francesco
authors.initials: F
authors.lastname: de Pasquale
authors.forename: Andrea
authors.initials: A
authors.lastname: Cherubini
authors.forename: Patrice
authors.initials: P
authors.lastname: Péran
authors.forename: Carlo
authors.initials: C
authors.lastname: Caltagirone
authors.forename: Umberto
authors.initials: U
authors.lastname: Sabatini
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods*; D016000:Cluster Analysis; D003952:Diagnostic Imaging / Q000379:methods; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D015999:Multivariate Analysis; D009413:Nerve Fibers, Myelinated / Q000473:pathology*