title: Serial magnetization transfer imaging to characterize the early evolution of new MS lesions.
abstract: OBJECTIVE
  To explore the temporal relation of demyelination and blood-brain barrier breakdown during new lesion formation.
  
  
  BACKGROUND
  Conventional MRI appears sensitive for detecting changes due to MS, but may be limited by poor pathologic specificity. By indirectly assessing protons bound to rigid macromolecules, magnetization transfer (MT) imaging may provide information relating to tissue structure and, by inference, myelin integrity.
  
  
  METHODS
  Gadolinium contrast-enhanced MRI and MT imaging were performed at weekly intervals for 3 months in three patients with MS. For each enhancing lesion, the largest corresponding area of proton density hyperintensity seen during the study was outlined and magnetization transfer ratio (MTR) calculated at each time point from coregistered calculated MTR images. Lesions greater than 20 mm2, not affected by partial volume effects, and first enhancing after the baseline study were analyzed. Two-dimensional registration software allowed accurate evaluation of MTR in regions both before and after the initial appearance of MS lesions.
  
  
  RESULTS
  Mean lesion MTR decreased significantly during the first week of enhancement (29.6 percent units [pu] immediately pre-enhancement versus 28.2 pu at first documented stage of enhancement). No significant MTR reduction was noted before this.
  
  
  CONCLUSIONS
  The lack of observable change in MTR before the first detectable gadolinium enhancement within MS lesions suggests that blood-brain barrier disruption is closely related to, but not preceded by, demyelination.
authors.affiliation: NMR Research Unit, Institute of Neurology, London, UK.
authors.forename: N C
authors.initials: NC
authors.lastname: Silver
authors.forename: M
authors.initials: M
authors.lastname: Lai
authors.forename: M R
authors.initials: MR
authors.lastname: Symms
authors.forename: G J
authors.initials: GJ
authors.lastname: Barker
authors.forename: W I
authors.initials: WI
authors.lastname: McDonald
authors.forename: D H
authors.initials: DH
authors.lastname: Miller
mesh_terms: D000328:Adult; D001812:Blood-Brain Barrier; D005260:Female; D005682:Gadolinium; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009103:Multiple Sclerosis / Q000175:diagnosis*; D009186:Myelin Sheath / Q000473:pathology*
chemical_list: D005682:Gadolinium