title: Enhancement of temporal resolution and BOLD sensitivity in real-time fMRI using multi-slab echo-volumar imaging.
abstract: In this study, a new approach to high-speed fMRI using multi-slab echo-volumar imaging (EVI) is developed that minimizes geometrical image distortion and spatial blurring, and enables nonaliased sampling of physiological signal fluctuation to increase BOLD sensitivity compared to conventional echo-planar imaging (EPI). Real-time fMRI using whole brain 4-slab EVI with 286 ms temporal resolution (4mm isotropic voxel size) and partial brain 2-slab EVI with 136 ms temporal resolution (4×4×6 mm(3) voxel size) was performed on a clinical 3 Tesla MRI scanner equipped with 12-channel head coil. Four-slab EVI of visual and motor tasks significantly increased mean (visual: 96%, motor: 66%) and maximum t-score (visual: 263%, motor: 124%) and mean (visual: 59%, motor: 131%) and maximum (visual: 29%, motor: 67%) BOLD signal amplitude compared with EPI. Time domain moving average filtering (2s width) to suppress physiological noise from cardiac and respiratory fluctuations further improved mean (visual: 196%, motor: 140%) and maximum (visual: 384%, motor: 200%) t-scores and increased extents of activation (visual: 73%, motor: 70%) compared to EPI. Similar sensitivity enhancement, which is attributed to high sampling rate at only moderately reduced temporal signal-to-noise ratio (mean: -52%) and longer sampling of the BOLD effect in the echo-time domain compared to EPI, was measured in auditory cortex. Two-slab EVI further improved temporal resolution for measuring task-related activation and enabled mapping of five major resting state networks (RSNs) in individual subjects in 5 min scans. The bilateral sensorimotor, the default mode and the occipital RSNs were detectable in time frames as short as 75 s. In conclusion, the high sampling rate of real-time multi-slab EVI significantly improves sensitivity for studying the temporal dynamics of hemodynamic responses and for characterizing functional networks at high field strength in short measurement times.
authors.affiliation: Department of Neurology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA. sposse@unm.edu
authors.forename: Stefan
authors.initials: S
authors.lastname: Posse
authors.forename: Elena
authors.initials: E
authors.lastname: Ackley
authors.forename: Radu
authors.initials: R
authors.lastname: Mutihac
authors.forename: Jochen
authors.initials: J
authors.lastname: Rick
authors.forename: Matthew
authors.initials: M
authors.lastname: Shane
authors.forename: Cristina
authors.initials: C
authors.lastname: Murray-Krezan
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
authors.forename: Oliver
authors.initials: O
authors.lastname: Speck
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000502:physiology; D001921:Brain / Q000033:anatomy & histology*; D001931:Brain Mapping; D003627:Data Interpretation, Statistical; D017352:Echo-Planar Imaging / Q000379:methods*; D006321:Heart / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D017397:Prefrontal Cortex / Q000033:anatomy & histology / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D059629:Signal-To-Noise Ratio; D012984:Software; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology; D014796:Visual Perception / Q000502:physiology
chemical_list: D010100:Oxygen