Using PINS pulses to investigate Inflow effects in SE-BOLD fMRI at 3T and 7T

Motivation: Most fMRI techniques infer neuronal activity from signal changes created by a complex interplay between hemodynamics and sequence design parameters. Goal(s): Investigate inflow effects in SE-BOLD fMRI signals at different field strengths and resolutions. Approach: We placed PINS pulses to saturate the magnetization in all slice gaps. By turning them on or off, inflow contributions to the SE-BOLD signal were modulated. Both 3- and 1.5-mm data were collected using a visual stimulation paradigm at 3T and 7T. Results: Inflow contributions to SE-BOLD varied by field strength and partial voluming effects. Even at 7T, non-negligible inflow contributions were observed. Impact: Saturating the magnetization in slice-gaps allows investigation of inflow effects in SE-BOLD fMRI. Low-resolution 3T-data revealed differences in onset timing. Comparing low- and high-resolution 7T-data with and without slice-gap saturation, increased resolution retained more activation, suggesting reduced sensitivity to inflow.