Multi-Echo SSFP: A Method for Synthetic bSSFP MRI Contrast Without Banding Artifacts at High Field

Balanced steady-state free precession (bSSFP) is an important MRI sequence paradigm with a high signal-to-noise ratio (SNR) and inherent $T_2/T_1$ contrast, but suffers from banding artifacts due to $B_0$ inhomogeneity, especially in high-field MRI. This study introduces a multi-echo SSFP (MESS) sequence that synthesizes tunable bSSFP contrast without banding artifacts.

In bSSFP imaging, the observed signal can be formulated as a superposition of multiple echo orders, where off-resonance phase divergences produce destructive interference, leading to dark bands. In contrast, the MESS sequence acquires these echoes separately. Extended phase graph (EPG) modeling demonstrates that by summing the echo magnitudes, MESS can reconstruct a signal that mirrors bSSFP contrast without banding artifacts. Image contrast can generally be tuned retrospectively by varying the virtual phase-cycle increment $\Delta \varphi$ . Phantom and in vivo experiments on a 5T scanner were performed to validate this approach.

Phantom studies confirmed that MESS reconstructs the bSSFP contrast free of banding artifacts. In vivo scans further demonstrated robust artifact suppression while maintaining bSSFP-like image contrast, and permitted flexible contrast variation by tuning $\Delta \varphi$ .

MESS enables robust generation of banding artifact-free bSSFP contrast in high-field MRI by leveraging echo magnitude and virtual phase-cycling, indicating a strong potential for robust image contrast synthesis.