Inverted BOLD signal changes in the transient phase of passband balanced SSFP

Motivation: Efficient, distortion-free, and selective to microvessels: these attributes make bSSFP an attractive candidate for fMRI. 2D multi-slice scans in the transient state are increasingly employed as an alternative to 3D steady-state imaging to improve localization. Goal(s): To evaluate the BOLD sensitivity of bSSFP during the transient phase as compared to the steady state. Approach: bSSFP acquisitions in transient and steady state are utilized for task-based fMRI. Monte Carlo simulations and in vitro microsphere experiments are conducted to verify the in vivo results. Results: An inversion of the BOLD contrast with a trend towards negative BOLD in the early transient phase can be observed. Impact: The bSSFP BOLD contrast undergoes an inversion during the transient phase. Consequently, the BOLD response appears suppressed in transient-state imaging with a tendency to become negative, which has important implications when designing 2D multi-slice fMRI experiments with high temporal resolution.