title: Multiple sclerosis: magnetization transfer MR imaging of white matter before lesion appearance on T2-weighted images.
abstract: OBJECTIVE
  To determine the evolution of magnetization transfer (MT) in white matter regions before and after plaque development in patients with multiple sclerosis (MS).
  
  
  METHODS
  In a 5-year longitudinal evaluation, 30 patients with MS underwent conventional magnetic resonance (MR) imaging, MT MR imaging, and clinical assessment. Cross-sectional data in 12 healthy subjects were also collected. Semiautomated lesion classification with use of T2-weighted MR images was used to measure the time course of the MT ratio (calculated with MR data acquired without and with MT saturation) in every voxel and to help analyze the relationship with the status of lesions depicted on T2-weighted images.
  
  
  RESULTS
  There was a significant (P <.001) temporal decline in lesion MT ratio after lesion appearance on T2-weighted images. A significant (P <. 001) progressive decline in MT ratio was also present in voxels that later became lesions, prior to initial detection on T2-weighted images. Even 1(1/2) years prior to lesion appearance, the MT ratio (33.3%) in regions destined to become such lesions was significantly (P <.001) lower than that in both white matter in healthy subjects (41.3%) and other normal-appearing white matter in patients with MS (38.1%).
  
  
  CONCLUSIONS
  The MT ratio reveals progressive focal abnormalities in MS that antedate by up to 2 years the appearance of lesions on T2-weighted MR images.
authors.affiliation: McConnell Brain Imaging Center, Montreal Neurological Institute, 3801 University St, Montreal, Québec, Canada. bruce@bic.mni.mcgill.ca
authors.forename: G B
authors.initials: GB
authors.lastname: Pike
authors.forename: N
authors.initials: N
authors.lastname: De Stefano
authors.forename: S
authors.initials: S
authors.lastname: Narayanan
authors.forename: K J
authors.initials: KJ
authors.lastname: Worsley
authors.forename: D
authors.initials: D
authors.lastname: Pelletier
authors.forename: G S
authors.initials: GS
authors.lastname: Francis
authors.forename: J P
authors.initials: JP
authors.lastname: Antel
authors.forename: D L
authors.initials: DL
authors.lastname: Arnold
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis*; D018709:Statistics, Nonparametric; D013997:Time Factors