title: B1-sensitivity analysis of quantitative magnetization transfer imaging.
abstract: OBJECTIVE
  To evaluate the sensitivity of quantitative magnetization transfer (qMT) fitted parameters to B1inaccuracies, focusing on the difference between two categories of T1mapping techniques: B1-independent and B1-dependent.
  
  
  METHODS
  The B1-sensitivity of qMT was investigated and compared using two T1measurement methods: inversion recovery (IR) (B1-independent) and variable flip angle (VFA), B1-dependent). The study was separated into four stages: 1) numerical simulations, 2) sensitivity analysis of the Z-spectra, 3) healthy subjects at 3T, and 4) comparison using three different B1imaging techniques.
  
  
  RESULTS
  For typical B1variations in the brain at 3T (±30%), the simulations resulted in errors of the pool-size ratio (F) ranging from -3% to 7% for VFA, and -40% to > 100% for IR, agreeing with the Z-spectra sensitivity analysis. In healthy subjects, pooled whole-brain Pearson correlation coefficients for F (comparing measured double angle and nominal flip angle B1maps) were ρ = 0.97/0.81 for VFA/IR.
  
  
  CONCLUSIONS
  This work describes the B1-sensitivity characteristics of qMT, demonstrating that it varies substantially on the B1-dependency of the T1mapping method. Particularly, the pool-size ratio is more robust against B1inaccuracies if VFA T1mapping is used, so much so that B1mapping could be omitted without substantially biasing F. Magn Reson Med 79:276-285, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Boudreau
authors.affiliation: Département du Génie Biomédical, École Polytechnique de Montreal, Montreal, Quebec, Canada.|Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: Nikola
authors.initials: N
authors.lastname: Stikov
authors.affiliation: McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.|Hotchkiss Brain Institute and Department of Radiology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: G Bruce
authors.initials: GB
authors.lastname: Pike
mesh_terms: D000054:Acceleration; D000328:Adult; D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D002138:Calibration; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008297:Male; D008872:Microwaves; D008953:Models, Anatomic; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011846:Radio Waves; D015203:Reproducibility of Results
keywords: B1 mapping; T1 mapping; quantitative magnetization transfer; sensitivity analysis