title: Magnetic resonance angiography signal intensity as a marker of hemodynamic impairment in intracranial arterial stenosis.
abstract: BACKGROUND
  Intracranial arterial stenosis (ICAS) is the predominant cause of ischemic stroke and transient ischemic attack in Asia. Change of signal intensities (SI) across an ICAS on magnetic resonance angiography (MRA) may reflect its hemodynamic severity.
  
  
  METHODS
  In-patients with a symptomatic single ICAS detected on 3D time-of-flight MRA were recruited from 2 hospitals. Baseline and 1-year follow-up data were collected. Signal intensity ratio (SIR) [ =  (mean post-stenotic SI -mean background SI)/(mean pre-stenotic SI - mean background SI)] was evaluated on baseline MRA to represent change of SIs across an ICAS. Acute infarct volume was measured on baseline diffusion-weighted images (DWI). Relationships between SIR and baseline characteristics as well as 1y outcomes were evaluated.
  
  
  RESULTS
  Thirty-six subjects (86.1% males, mean age 55.0) were recruited. Overall, mean SIR was 0.84±0.23. Mean SIRs were not significantly different between the 23 (63.9%) anatomically severe stenoses and the 13 (36.1%) anatomically moderate stenoses (0.80±0.23 versus 0.92±0.21, p = 0.126). SIR was significantly, linearly and negatively correlated to acute infarct volume on DWI (Spearman correlation coefficient -0.471, p = 0.011). Two patients (5.6%) had recurrent ischemic strokes at 1y, not related to SIR values.
  
  
  CONCLUSIONS
  Change of signal intensities across an ICAS on MRA may reflect its hemodynamic and functional severity. Future studies are warranted to further verify the relationships between this index and prognosis of patients with symptomatic ICAS.
authors.affiliation: Department of Medicine and Therapeutics, the Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong Special Administrative Region, China.
authors.forename: Xinyi
authors.initials: X
authors.lastname: Leng
authors.forename: Ka Sing
authors.initials: KS
authors.lastname: Wong
authors.forename: Yannie
authors.initials: Y
authors.lastname: Soo
authors.forename: Thomas
authors.initials: T
authors.lastname: Leung
authors.forename: Xinying
authors.initials: X
authors.lastname: Zou
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Wang
authors.forename: Edward
authors.initials: E
authors.lastname: Feldmann
authors.forename: Liping
authors.initials: L
authors.lastname: Liu
authors.forename: David S
authors.initials: DS
authors.lastname: Liebeskind
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology; D003251:Constriction, Pathologic; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D020765:Intracranial Arterial Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis / Q000209:etiology