Dual-excitation flip-angle simultaneous cine and T1 mapping using spiral acquisition with respiratory and cardiac self-gating

Abstract

Purpose: To develop a free-breathing cardiac self-gated technique that provides cine images and $B_1^{+}$ slice profile-corrected T₁ maps from a single acquisition.

Methods: Without breath-holding or electrocardiogram gating, data were acquired continuously on a 3T scanner using a golden-angle gradient-echo spiral pulse sequence, with an inversion RF pulse applied every 4 seconds. Flip angles of 3° and 15° were used for readouts after the first four and second four inversions. Self-gating cardiac triggers were extracted from heart image navigators, and respiratory motion was corrected by rigid registration on each heartbeat. Cine images were reconstructed from the steady-state portion of 15° readouts using a low-rank plus sparse reconstruction. The T₁ maps were fit using a projection onto convex sets approach from images reconstructed using slice profile-corrected dictionary learning. This strategy was evaluated in a phantom and 14 human subjects.

Results: The self-gated signal demonstrated close agreement with the acquired electrocardiogram signal. The image quality for the proposed cine images and standard clinical balanced SSFP images were 4.31 (±0.50) and 4.65 (±0.30), respectively. The slice profile-corrected T₁ values were similar to those of the inversion-recovery spin-echo technique in phantom, and had a higher global T₁ value than that of MOLLI in human subjects.

Conclusions: Cine and T₁ mapping using spiral acquisition with respiratory and cardiac self-gating successfully acquired T₁ maps and cine images in a single acquisition without the need for electrocardiogram gating or breath-holding. This dual-excitation flip-angle approach provides a novel approach for measuring T₁ while accounting for $B_1^{+}$ and slice profile effect on the apparent $T_1^{\ast }$ .

Keywords: T1 mapping; cardiac MRI; cine; dictionary learning; self-gating; spiral trajectory.