title: The role of edema and demyelination in chronic T1 black holes: a quantitative magnetization transfer study.
abstract: OBJECTIVE
  To use quantitative magnetization transfer imaging (qMTI) in an investigation of T1-weighted hypointensity observed in clinical magnetic resonance imaging (MRI) scans of multiple sclerosis (MS) patients, which has previously been proposed as a more specific indicator of tissue damage than the more commonly detected T2 hyperintensity.
  
  
  METHODS
  A cross-sectional study of 10 MS patients was performed using qMTI. A total of 60 MTI measurements were collected in each patient at a resolution of 2 x 2 x 7 mm, over a range of saturation pulses. The observed T1 and T2 were also measured. qMT model parameters were estimated using a voxel-by-voxel fit.
  
  
  RESULTS
  A total of 65 T2-hyperintense lesions were identified; 53 were also T1 hypointense. In these black holes, the qMTI-derived semisolid pool fraction F correlated negatively with T(1,obs) (r2 = 0.76; P < 0.0001). The water pool absolute size (PDf) showed a weaker correlation with T(1,obs) (positive, r2 = 0.53; P < 0.0001). The magnetization transfer ratio (MTR) showed a similarly strong correlation with F and a weaker correlation with PDf (r2 = 0.18; P < 0.04).
  
  
  CONCLUSIONS
  T1 increases in chronic black holes strongly correlated with the decline in semisolid pool size, and somewhat less to the confounding effect of edema. MTR was less sensitive than T(1,obs) to liquid pool changes associated with edema.
authors.affiliation: McConnell Brain Imaging Centre, Montréal Neurological Institute, McGill University, Montréal, H3A 2B4 Québec, Canada. ives@bic.mni.mcgill.ca
authors.forename: Ives
authors.initials: I
authors.lastname: Levesque
authors.forename: John G
authors.initials: JG
authors.lastname: Sled
authors.forename: Sridar
authors.initials: S
authors.lastname: Narayanan
authors.forename: A Carlos
authors.initials: AC
authors.lastname: Santos
authors.forename: Steven D
authors.initials: SD
authors.lastname: Brass
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Francis
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Arnold
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
mesh_terms: D000328:Adult; D001834:Body Water; D001921:Brain / Q000473:pathology; D001929:Brain Edema / Q000473:pathology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003711:Demyelinating Diseases / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000473:pathology*; D020528:Multiple Sclerosis, Chronic Progressive / Q000473:pathology; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000473:pathology; D009186:Myelin Sheath / Q000473:pathology; D013997:Time Factors