title: Air pressure-induced susceptibility changes in vascular reactivity studies using BOLD MRI.
abstract: OBJECTIVE
  To investigate whether compressed air during air-cuff inflation in vascular reactivity studies could induce aberrant blood oxygenation level-dependent (BOLD) signal change.
  
  
  METHODS
  Magnetic resonance imaging (MRI) experiments were performed on a whole-body 3 T scanner. The pattern of T2* signal change measured from a phantom simulating the lower limb was assessed while a thigh cuff was inflated and deflated. MR spectroscopy was performed on a head phantom wrapped using a hand-cuff to determine the relationship between water peak linewidth and applied cuff pressure. Calf muscles from 14 normal subjects were examined to identify aberrant T2* signal changes in the occluded and nonoccluded legs.
  
  
  RESULTS
  A sudden T2* signal drop was observed in the phantom on initiation of cuff inflation with subsequent signal change being dependent on cuff pressure. Water peak linewidth increased linearly with cuff pressure (r(2) = 0.94). Aberrant T2* signal changes were observed in both the occluded and nonoccluded legs.
  
  
  CONCLUSIONS
  Compressed air due to cuff inflation directly affects local magnetic field susceptibility. The T2* sequence is sensitive to local field disturbances induced by an inflated cuff. Muscle BOLD results are affected by high-pressure air, with a sudden drop in T2* signal being a characteristic feature of this induced effect.
authors.affiliation: Department of Imaging and Interventional Radiology, Faculty of Medicine, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong SAR, China.
authors.forename: David K W
authors.initials: DK
authors.lastname: Yeung
authors.forename: James F
authors.initials: JF
authors.lastname: Griffith
authors.forename: Alvin F W
authors.initials: AF
authors.lastname: Li
authors.forename: Heather T
authors.initials: HT
authors.lastname: Ma
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
mesh_terms: D000328:Adult; D000399:Air Pressure; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000473:pathology*; D007511:Ischemia / Q000473:pathology; D007866:Leg / Q000098:blood supply; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D010100:Oxygen / Q000737:chemistry; D019047:Phantoms, Imaging; D013696:Temperature
chemical_list: D010100:Oxygen