title: Steady-state functional MRI using spoiled small-tip fast recovery imaging.
abstract: OBJECTIVE
  To determine whether a recently proposed steady-state magnetic resonance imaging (MRI) sequence, "small-tip fast recovery" (STFR), can be used for functional brain imaging. Compared to existing functional MRI (fMRI) based on T2*-contrast and long echo time, STFR has the potential for high-resolution imaging with reduced B0 artifacts such as geometric distortions, blurring, or local signal dropout.
  
  
  METHODS
  We used Monte Carlo Bloch simulations to calculate the voxel-averaged steady-state signal during rest and activation, for blood oxygen level dependent (BOLD) and STFR. STFR relies on a tailored "tip-up" radiofrequency pulse to align the spins with the longitudinal axis after each data readout segment, and here we performed proof-of-concept in vivo STFR fMRI experiments using a tip-up pulse tailored to a two-dimensional region-of-interest in motor cortex. Experiments were performed on multiple subjects to test reliability of the functional activation maps.
  
  
  RESULTS
  Bloch simulations predict a detectable functional signal that depends mainly on intravoxel dephasing, and only weakly on spin diffusion. STFR produces similar activation maps and signal change as BOLD in finger-tapping experiments, and shows reliability comparable to BOLD.
  
  
  CONCLUSIONS
  STFR can produce functional contrast (even with short TE), and is a potential alternative to long-TE ( T2*) fMRI. The functional contrast arises primarily from the interaction between T2*-like dephasing and the tailored tip-up pulse, and not from spin diffusion.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Sun
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fessler
authors.forename: Douglas C
authors.initials: DC
authors.lastname: Noll
authors.forename: Jon-Fredrik
authors.initials: JF
authors.lastname: Nielsen
mesh_terms: D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: blood oxygen level dependent; functional magnetic resonance imaging; passband balanced steady-state free precession; passband steady-state free precession; small-tip fast recovery