title: Correlation of diffusion tensor and dynamic perfusion MR imaging metrics in normal-appearing corpus callosum: support for primary hypoperfusion in multiple sclerosis.
abstract: OBJECTIVE
  Hypoperfusion of the normal-appearing white matter in multiple sclerosis (MS) may be related to ischemia or secondary to hypometabolism from wallerian degeneration (WD). This study evaluated whether correlating perfusion and diffusion tensor imaging (DTI) metrics in normal-appearing corpus callosum could provide support for an ischemic mechanism for hypoperfusion.
  
  
  METHODS
  Fourteen patients with relapsing-remitting MS (RRMS) and 17 control subjects underwent perfusion MR imaging and DTI. Absolute measures of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) were calculated. Mean diffusivity (MD) and fractional anisotropy (FA) maps were computed from DTI data. After visual coregistration of perfusion and DTI images, regions of interest were placed in the genu, central body, and splenium of normal-appearing corpus callosum. Pearson product-moment correlation coefficients were calculated using mean DTI and perfusion measures in each region.
  
  
  RESULTS
  In the RRMS group, CBF and CBV were significantly correlated with MD in the splenium (r = 0.83 and r = 0.63, respectively; both P < .001) and in the central body (r = 0.86 and r = 0.65, respectively; both P < .001), but not in the genu (r = 0.23 and 0.25, respectively; both P is nonsignificant). No significant correlations were found between MTT and DTI measures or between FA and any perfusion measure in the RRMS group. No significant correlations between diffusion and perfusion metrics were found in control subjects.
  
  
  CONCLUSIONS
  In the normal-appearing corpus callosum of patients with RRMS, decreasing perfusion is correlated with decreasing MD. These findings are more consistent with what would be expected in primary ischemia than in secondary hypoperfusion from WD.
authors.affiliation: Department of Radiology, New York University Medical Center, New York, NY, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Saindane
authors.forename: M
authors.initials: M
authors.lastname: Law
authors.forename: Y
authors.initials: Y
authors.lastname: Ge
authors.forename: G
authors.initials: G
authors.lastname: Johnson
authors.forename: J S
authors.initials: JS
authors.lastname: Babb
authors.forename: R I
authors.initials: RI
authors.lastname: Grossman
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001810:Blood Volume; D003287:Contrast Media; D003337:Corpus Callosum / Q000098:blood supply*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000503:physiopathology*
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA