title: Blood oxygenation level-dependent (BOLD) MRI of human skeletal muscle at 1.5 and 3 T.
abstract: OBJECTIVE
  To evaluate the dependence of skeletal muscle blood oxygenation level-dependent (BOLD) effect and time course characteristics on magnetic field strength in healthy volunteers using an ischemia/reactive hyperemia paradigm.
  
  
  METHODS
  Two consecutive skeletal muscle BOLD magnetic resonance imaging (MRI) measurements in eight healthy volunteers were performed on 1.5 T and 3.0 T whole-body MRI scanners. For both measurements a fat-saturated multi-shot multiecho gradient-echo EPI sequence was applied. Temporary vascular occlusion was induced by suprasystolic cuff compression of the thigh. T2 time courses were obtained from two different calf muscles and characterized by typical curve parameters. Ischemia- and hyperemia-induced changes in R2 (ΔR2) were calculated for both muscles in each volunteer at the two field strengths.
  
  
  RESULTS
  Skeletal muscle BOLD changes are dependent on magnetic field strength as the ratio ΔR2(3.0 T)/ΔR2(1.5 T) was found to range between 1.6 and 2.2. Regarding time course characteristics, significantly higher relative T2 changes were found in both muscles at 3.0 T.
  
  
  CONCLUSIONS
  The present study shows an approximately linear field strength dependence of ΔR2 in the skeletal muscle in response to ischemia and reactive hyperemia. Using higher magnetic fields is advisable for future BOLD imaging studies of peripheral limb pathologies.
authors.affiliation: Department of Radiology, University Hospital Bruderholz, Basel, Switzerland. sasanp@gmx.de
authors.forename: Sasan
authors.initials: S
authors.lastname: Partovi
authors.forename: Anja-Carina
authors.initials: AC
authors.lastname: Schulte
authors.forename: Bjoern
authors.initials: B
authors.lastname: Jacobi
authors.forename: Markus
authors.initials: M
authors.lastname: Klarhöfer
authors.forename: Alan B
authors.initials: AB
authors.lastname: Lumsden
authors.forename: Matthias
authors.initials: M
authors.lastname: Loebe
authors.forename: Mark G
authors.initials: MG
authors.lastname: Davies
authors.forename: Georg P
authors.initials: GP
authors.lastname: Noon
authors.forename: Christof
authors.initials: C
authors.lastname: Karmonik
authors.forename: Lisa
authors.initials: L
authors.lastname: Zipp
authors.forename: Georg
authors.initials: G
authors.lastname: Bongartz
authors.forename: Deniz
authors.initials: D
authors.lastname: Bilecen
mesh_terms: D000328:Adult; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology*; D007511:Ischemia / Q000503:physiopathology*; D007866:Leg / Q000098:blood supply*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*