title: Vascular space occupancy (VASO) cerebral blood volume-weighted MRI identifies hemodynamic impairment in patients with carotid artery disease.
abstract: OBJECTIVE
  To assess the role of vascular space occupancy (VASO) magnetic resonance imaging (MRI), a noninvasive cerebral blood volume (CBV)-weighted technique, for evaluating CBV reactivity in patients with internal carotid artery (ICA) stenosis.
  
  
  METHODS
  VASO reactivity, defined as a signal change in response to hypercapnic stimulus (4-second exhale, 14-second breath-hold), was measured in the left and right ICA flow territories in patients (n=10) with varying degrees of unilateral and bilateral ICA stenosis and in healthy volunteers (n=10).
  
  
  RESULTS
  Percent VASO reactivity was more negative (P<0.01) bilaterally in patients (ipsilateral: -3.6+/-1.5%; contralateral: -3.4+/-1.2%) compared with age-matched controls (left: -1.9+/-0.6%; right: -1.9+/-0.8%). Owing to the nature of the VASO contrast mechanism, this more negative VASO reactivity was attributed to autoregulatory CBV effects in patients. A postbreath-hold overshoot, which was absent in healthy volunteers, was observed unilaterally in a subset of patients.
  
  
  CONCLUSIONS
  More negative VASO reactivity was observed in patients with ICA stenosis and may be a marker of autoregulatory effects. Furthermore, the postbreath-hold overshoot observed in patients is consistent with compensatory microvascular vasoconstriction and may be a marker of hemodynamic impairment. Based on the results of this feasibility study, VASO should be useful for identifying CBV adjustments in patients with steno-occlusive disease of the ICA.
authors.affiliation: Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Manus J
authors.initials: MJ
authors.lastname: Donahue
authors.forename: Peter Jan
authors.initials: PJ
authors.lastname: van Laar
authors.forename: Peter C M
authors.initials: PC
authors.lastname: van Zijl
authors.forename: Robert D
authors.initials: RD
authors.lastname: Stevens
authors.forename: Jeroen
authors.initials: J
authors.lastname: Hendrikse
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001810:Blood Volume; D001921:Brain / Q000098:blood supply*; D002340:Carotid Artery Diseases / Q000175:diagnosis / Q000503:physiopathology*; D002560:Cerebrovascular Circulation; D005240:Feasibility Studies; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged