3D joint T1/T1 ρ/T2 mapping and water-fat imaging for contrast-agent free myocardial tissue characterization at 1.5T.

Abstract

Purpose: To develop a novel, free-breathing, 3D joint $T_1$ / $T_{1\rho }$ / $T_2$ mapping sequence with Dixon encoding to provide co-registered 3D $T_1$ , $T_{1\rho }$ , and $T_2$ maps and water-fat volumes with isotropic spatial resolution in a single $\approx 7$ min scan for comprehensive contrast-agent-free myocardial tissue characterization and simultaneous evaluation of the whole-heart anatomy.

Methods: An interleaving sequence over 5 heartbeats is proposed to provide $T_1$ , $T_{1\rho }$ , and $T_2$ encoding, with 3D data acquired with Dixon gradient-echo readout and 2D image navigators to enable $100\%$ respiratory scan efficiency. Images were reconstructed with a non-rigid motion-corrected, low-rank patch-based reconstruction, and maps were generated through dictionary matching. The proposed sequence was compared against conventional 2D techniques in phantoms, 10 healthy subjects, and 1 patient.

Results: The proposed 3D $T_1$ , $T_{1\rho }$ , and $T_2$ measurements showed excellent correlation with 2D reference measurements in phantoms. For healthy subjects, the mapping values of septal myocardial tissue were $T_1=1060\pm 48\text{ms}$ , $T_{1\rho }=48.1\pm 3.9\text{ms}$ , and $T_2=44.2\pm 3.2\text{ms}$ for the proposed sequence, against $T_1=959\pm 15\text{ms}$ , $T_{1\rho }=56.4\pm 1.9\text{ms}$ , and $T_2=47.3\pm 1.5\text{ms}$ for 2D MOLLI, 2D $T_{1\rho }$ -prep bSSFP and 2D $T_2$ -prep bSSFP, respectively. Promising results were obtained when comparing the proposed mapping to 2D references in 1 patient with active myocarditis.

Conclusion: The proposed approach enables simultaneous 3D whole-heart joint $T_1$ / $T_{1\rho }$ / $T_2$ mapping and water/fat imaging in $\approx$ 7 min scan time, demonstrating good agreement with conventional mapping techniques in phantoms and healthy subjects and promising results in 1 patient with suspected cardiovascular disease.