AbstractPurposeTo 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 T1ρ mapping at 3T.MethodsAn electrocardiogram‐triggered sequence with dual‐echo Dixon readout was developed, where nine cardiac cycles were repeatedly acquired with inversion recovery and T1ρ preparation pulses for T1 and T1ρ 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 T1ρ quantification. Phantoms and 10 heathy subjects were imaged to validate the proposed technique.ResultsThe proposed technique achieved strong correlation (T1: R2 = 0.99; T1ρ: R2 = 0.98) with the reference measurements in phantoms. 3D cardiac T1 and T1ρ maps with spatial resolution of 2 × 2 × 4 mm were obtained with scan time of 5.4 ± 0.5 min, demonstrating comparable T1 (1236 ± 59 ms) and T1ρ (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.ConclusionThe proposed technique achieved efficient 3D joint myocardial T1 and T1ρ mapping at 3T with respiratory motion correction, spin history B1+ correction and water‐fat separation.