title: Comparison of muscle BOLD responses to arterial occlusion at 3 and 7 Tesla.
abstract: OBJECTIVE
  The purpose of this study was to determine the feasibility of muscle BOLD (mBOLD) imaging at 7 Tesla (T) by comparing the changes in R2* of muscle at 3 and 7T in response to a brief period of tourniquet-induced ischemia.
  
  
  METHODS
  Eight subjects (three male), aged 29.5 ± 6.1 years (mean ± standard deviation, SD), 167.0 ± 10.6 cm tall with a body mass of 62.0 ± 18.0 kg, participated in the study. Subjects reported to the lab on four separate occasions including a habituation session, two MRI scans, and in a subset of subjects, a session during which changes in blood flow and blood oxygenation were quantified using Doppler ultrasound (U/S) and near-infrared spectroscopy (NIRS) respectively. For statistical comparisons between 3 and 7T, R2* rate constants were calculated as R2* = 1/T2*.
  
  
  RESULTS
  The mean preocclusion R2* value was greater at 7T than at 3T (60.16 ± 2.95 vs. 35.17 ± 0.35 s(-1), respectively, P < 0.001). Also, the mean ΔR2 *END and ΔR2*POST values were greater for 7T than for 3T (-2.36 ± 0.25 vs. -1.24 ± 0.39 s(-1), respectively, Table 1).
  
  
  CONCLUSIONS
  Muscle BOLD contrast at 7T is as much as six-fold greater than at 3T. In addition to providing greater SNR and CNR, 7T mBOLD studies may offer further advantages in the form of greater sensitivity to pathological changes in the muscle microcirculation.
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Physical Medicine and Rehabilitation, Vanderbilt University Medical Center, Nashville, Tennessee, USA.|Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Theodore F
authors.initials: TF
authors.lastname: Towse
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Childs
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Shea A
authors.initials: SA
authors.lastname: Sabin
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Emily C
authors.initials: EC
authors.lastname: Bush
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Elder
authors.affiliation: Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.|Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Damon
mesh_terms: D000328:Adult; D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000503:physiopathology; D010100:Oxygen / Q000097:blood*; D019265:Spectroscopy, Near-Infrared; D018608:Ultrasonography, Doppler; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Doppler ultrasound; NIRS; human; transverse relaxation; ultra-high field MRI