Rapid free-breathing myocardial T1 mapping with free-running interleaved multi-slice acquisition and respiratory motion correction using self-navigated auto calibration.

Purpose: To develop a rapid 2D free-running myocardial $T_1$ mapping technique that is robust to through-plane respiratory motion.

Methods: A free-running golden angle radial sequence consisting of $T_1$ encoding and self-navigated auto motion calibration (SNAC) was developed. The $T_1$ encoding adopted inversion recovery (IR) prepared interleaved multi-slice acquisition with optimized inter-slice gap to ensure a uniform excitation of the middle slice regardless of through-plane respiratory motion. The flip angles were alternated between the odd and even IR readouts to correct flip-angle errors. SNAC was designed to calibrate the through-plane motion with the respiratory self-navigation signal extracted from the free-running sequence, and integrate the multi-slice data into a through-plane motion-corrected 2D slice for $T_1$ mapping reconstruction. Numerical simulations were performed to optimize the key sequence parameters, followed by phantom and in-vivo imaging to validate the accuracy and repeatability.

Results: Numerical simulations yielded the dual flip angles minimizing $T_1$ estimation errors and the adjacent slice offset achieving uniformity in the superimposed slice profile. Phantom experiments demonstrated a strong correlation between the proposed and reference method, and no dependence of the free-running $T_1$ estimation on heart rates. Adding through-plane respiratory motion correction significantly improved the in-vivo $T_1$ mapping sharpness and visual quality. Validated against the conventional breath-hold mapping technique, the motion corrected free-running method achieved comparable $T_1$ mapping quality and repeatability.

Conclusion: Respiratory motion is effectively suppressed in the proposed 2D free-running method, which achieves superior $T_1$ mapping with acceptable repeatability in a short scan time of 46 s.