Unraveling bSSFP Phase: High Quality Field and Bias Mapping

Motivation: MRI signal phase is crucial for various advanced MRI techniques, yet extracting needed phase components can be challenging. Goal(s): To develop a comprehensive B0 field mapping procedure that includes full FOV, high quality characterization of RF receive-channel-specific bias using the bSSFP elliptical signal model for improved quantitative phase-sensitive MRI reconstructions. Approach: Utilizing bSSFP geometry, the off-resonance phase accumulation at different stages of the sequence were calculated and leveraged to create refined B0 field and RF receive-channel-specific bias maps. Results: Phantom data confirmed that the derived B0 field and RF receive-channel-specific bias maps are accurate with high SNR and full FOV coverage. Impact: The proposed method leverages bSSFP's SNR efficiency to generate B0 and RF receive-channel bias maps with high-SNR, smooth variation, and full FOV coverage. This enables advanced phase-sensitive reconstructions and correction of phase-related system errors without requiring additional scans.