title: Magnetic susceptibility contrast variations in multiple sclerosis lesions.
abstract: OBJECTIVE
  Recent magnetic resonance imaging (MRI) studies have revealed heterogeneous magnetic susceptibility contrasts in multiple sclerosis (MS) lesions. Due to its sensitivity to disease-related iron and myelin changes, magnetic susceptibility-based measures may better reflect some pathological features of MS lesions. Hence, we sought to characterize MS lesions using combined R2* mapping and quantitative susceptibility mapping (QSM).
  
  
  METHODS
  In all, 306 MS lesions were selected from 24 MS patients who underwent 7T MRI. Maps of R2*, frequency, and quantitative susceptibility were calculated using acquired multiecho gradient echo (GRE) phase data. Lesions were categorized based on their image intensity or their anatomical locations. R2* and susceptibility values were quantified in each lesion based on manually drawn lesion masks and compared between lesion groups showing different contrast patterns. Correlations between R2* and susceptibility were also tested in these lesion groups.
  
  
  RESULTS
  In 38% of selected lesions the frequency map did not show the same contrast pattern as the susceptibility map. While most lesions (93%) showed hypointensity on R2*, the susceptibility contrast in lesions varied, with 40% being isointense and 58% being hyperintense in the lesion core. Significant correlations (r = 0.31, P < 0.001) between R2* and susceptibility were found in susceptibility hyperintense lesions, but not in susceptibility isointense lesions. In addition, a higher proportion (74%) of periventricular lesions was found to be susceptibility hyperintense as compared to subcortical (53%) or juxtacortical (38%) lesions.
  
  
  CONCLUSIONS
  Combining R2* and QSM is useful to characterize heterogeneity in MS lesions.
authors.affiliation: F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Harrison
authors.affiliation: F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.|Department of Radiology, Guangdong Academy of Medical Sciences, Guangdong General Hospital, Guangzhou, China.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Liu
authors.affiliation: F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Craig K
authors.initials: CK
authors.lastname: Jones
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Oh
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Calabresi
authors.affiliation: F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA.|Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Peter C M
authors.initials: PC
authors.lastname: van Zijl
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009103:Multiple Sclerosis / Q000473:pathology*; D012680:Sensitivity and Specificity
keywords: R2*; iron; lesion; multiple sclerosis; myelin; quantitative susceptibility mapping (QSM)