title: Functional MRI in human subjects with gradient-echo and spin-echo EPI at 9.4 T.
abstract: OBJECTIVE
  The increased signal-to-noise ratio and blood oxygen level dependent signal at ultra-high field can only help to boost the resolution in functional MRI studies if the spatial specificity of the activation signal is improved. At a field strength of 9.4 T, both gradient-echo and spin-echo based echo-planar imaging were implemented and applied to investigate the specificity of human functional MRI. A finger tapping paradigm was used to acquire functional MRI data with scan parameters similar to standard neuroscientific applications.
  
  
  METHODS
  Spatial resolution, echo, and readout times were varied to determine their influence on the distribution of the blood oxygen level dependent signal. High-resolution co-localized images were used to classify the signal according to its origin in veins or tissue.
  
  
  RESULTS
  High-quality activation maps were obtained with both sequences. Signal contributions from tissue were found to be smaller or slightly larger than from veins. Gradient-echo echo-planar imaging yielded lower ratios of micro-/macro-vascular signals of around 0.6 than spin-echo based functional MRI, where this ratio varied between 0.75 and 1.02, with higher values for larger echo and shorter readout time.
  
  
  CONCLUSIONS
  This study demonstrates the feasibility of human functional MRI at 9.4 T with high spatial specificity. Although venous contributions could not be entirely suppressed, venous effects in spin-echo echo-planar imaging are significantly reduced compared with gradient-echo echo-planar imaging.
authors: Max Planck Institute for Biological Cybernetics, High Field Magnetic Resonance Center, Tübingen, Germany; Graduate School of Neural and Behavioural Sciences, International Max Planck Research School, Universität Tübingen, Tübingen, Germany.
authors: Juliane
authors: J
authors: Budde
authors: G
authors: G
authors: Shajan
authors: Maxim
authors: M
authors: Zaitsev
authors: Klaus
authors: K
authors: Scheffler
authors: Rolf
authors: R
authors: Pohmann
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D064847:Multimodal Imaging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013113:Spin Labels
chemical_list: D013113:Spin Labels
keywords: BOLD; GRE-EPI; SE-EPI; human imaging; tissue; ultra-high field; veins