3D B1+corrected simultaneous myocardial T1 and T1ρ mapping with subject-specific respiratory motion correction and water-fat separation

Purpose: To develop a 3D free-breathing cardiac multi-parametric mapping framework that is robust to confounders of respiratory motion, fat, and B1+ inhomogeneities and validate it for joint myocardial T1 and T1 rho mapping at 3T. Methods: An electrocardiogram-triggered sequence with dual-echo Dixon readout was developed, where nine cardiac cycles were repeatedly acquired with inversion recovery and T1 rho preparation pulses for T1 and T1 rho sensitization. A subject-specific respiratory motion model relating the 1D diaphragmatic navigator to the respiration-induced 3D translational motion of the heart was constructed followed by respiratory motion binning and intra-bin 3D translational and inter-bin non-rigid motion correction. Spin history B1+ inhomogeneities were corrected with optimized dual flip angle strategy. After water-fat separation, the water images were matched to the simulated dictionary for T1 and T1 rho quantification. Phantoms and 10 heathy subjects were imaged to validate the proposed technique. Results: The proposed technique achieved strong correlation (T1: R-2=0.99; T1 rho: R-2=0.98) with the reference measurements in phantoms. 3D cardiac T1 and T1 rho maps with spatial resolution of 2x2x4 mm were obtained with scan time of 5.4 +/- 0.5 min, demonstrating comparable T1 (1236 +/- 59 ms) and T1 rho (50.2 +/- 2.4 ms) measurements to 2D separate breath-hold mapping techniques. The estimated B1+ maps showed spatial variations across the left ventricle with the septal and inferior regions being 10%-25% lower than the anterior and septal regions. Conclusion: The proposed technique achieved efficient 3D joint myocardial T1 and T1 rho mapping at 3T with respiratory motion correction, spin history B1+ correction and water-fat separation.