Free-breathing post-contrast three-dimensional T₁ mapping: Volumetric assessment of myocardial T₁ values

Purpose: To develop a three-dimensional (3D) free-breathing myocardial T¹ mapping sequence for assessment of left ventricle diffuse fibrosis after contrast administration.

Methods: In the proposed sequence, multiple 3D inversion recovery images are acquired in an interleaved manner. A mixed prospective/retrospective navigator scheme is used to obtain the 3D Cartesian k-space data with fully sampled center and randomly undersampled outer k-space. The resulting undersampled 3D k-space data are then reconstructed using compressed sensing. Subsequently, T₁ maps are generated by voxel-wise curve fitting of the individual interleaved images. In a phantom study, the accuracy of the 3D sequence was evaluated against two-dimensional (2D) modified Look-Locker inversion recovery (MOLLI) and spin-echo sequences. In vivo T₁ times of the proposed method were compared with 2D multislice MOLLI T₁ mapping. Subsequently, the feasibility of high-resolution 3D T₁ mapping with spatial resolution of 1.7 × 1.7 × 4 mm³ was demonstrated.

Results: The proposed method shows good agreement with 2D MOLLI and the spin-echo reference in phantom. No significant difference was found in the in vivo T₁ times estimated using the proposed sequence and the 2D MOLLI technique (myocardium, 330±66ms versus 319±93 ms; blood pools, 211±68 ms versus 210±98 ms). However, improved homogeneity, as measured using standard deviation of the T₁ signal, was observed in the 3D T₁ maps.

Conclusion: The proposed sequence enables high-resolution 3D T₁ mapping after contrast injection during free-breathing with volumetric left ventricle coverage.