title: Automatic model-based analysis of skeletal muscle BOLD-MRI in reactive hyperemia.
abstract: OBJECTIVE
  To propose a quantitative model for a reliable and operator independent estimation of parameters describing blood oxygen-level dependent (BOLD) MRI time course in calf muscles during reactive hyperemia.
  
  
  METHODS
  Echo planar imaging-based BOLD-MRI of the human calf were acquired during and after cuff-induced ischemia of the leg. Regions of interest were drawn in soleus, gastrocnemius and tibialis anterior muscles. A gamma-variate plus a sigmoidal function were fitted to the reactive hyperemia time courses and parameters including time to peak (TTP), hyperemic peak value (HPV), peak area, and peak width were calculated. In addition, the TTP and HPV parameters were estimated manually by two operators to validate the reliability of the fitting procedure.
  
  
  RESULTS
  The model function was fitted successfully to all data with a minimum reduced R(2) around 0.9. The in vivo results were in agreement with manually determined values (r ≥ 0.69), although significant inter-operator differences were observed.
  
  
  CONCLUSIONS
  The proposed method allows for rapid, operator independent and robust quantification of muscle BOLD signal during reactive hyperemia. The model worked equally well over a wide range of imaging parameters and data quality. This approach should contribute significantly to the standardization of skeletal muscle BOLD-MRI, an important step toward its clinical application.
authors.affiliation: MR Center of Excellence, Medical University of Vienna, Austria; Department of Clinical Pharmacology, Medical University of Vienna, Austria; Center of Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria.
authors.forename: Kiril
authors.initials: K
authors.lastname: Schewzow
authors.forename: Martin
authors.initials: M
authors.lastname: Andreas
authors.forename: Ewald
authors.initials: E
authors.lastname: Moser
authors.forename: Michael
authors.initials: M
authors.lastname: Wolzt
authors.forename: Albrecht I
authors.initials: AI
authors.lastname: Schmid
mesh_terms: D000328:Adult; D017352:Echo-Planar Imaging; D006801:Humans; D006940:Hyperemia / Q000175:diagnosis / Q000473:pathology*; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000473:pathology*; D007866:Leg / Q000473:pathology; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000473:pathology*; D015203:Reproducibility of Results; D055815:Young Adult