Free-breathing 3D cardiac extracellular volume (ECV) mapping using a linear tangent space alignment (LTSA) model

Abstract

Purpose: To develop a new method for free-breathing 3D extracellular volume (ECV) mapping of the whole heart at 3 T.

Methods: A free-breathing 3D cardiac ECV mapping method was developed at 3 T. T₁ mapping was performed before and after contrast agent injection using a free-breathing electrocardiogram-gated inversion recovery sequence with spoiled gradient echo readout. A linear tangent space alignment model-based method was used to reconstruct high-frame-rate dynamic images from (k,t)-space data sparsely sampled along a random stack-of-stars trajectory. Joint T₁ and transmit B₁ estimation were performed voxel-by-voxel for pre- and post-contrast T₁ mapping. To account for the time-varying T₁ after contrast agent injection, a linearly time-varying T₁ model was introduced for post-contrast T₁ mapping. ECV maps were generated by aligning pre- and post-contrast T₁ maps through affine transformation.

Results: The feasibility of the proposed method was demonstrated using in vivo studies with six healthy volunteers at 3 T. We obtained 3D ECV maps at a spatial resolution of 1.9 × 1.9 × 4.5 mm³ and a FOV of 308 × 308 × 144 mm³, with a scan time of 10.1 ± 1.4 and 10.6 ± 1.6 min before and after contrast agent injection, respectively. The ECV maps and the pre- and post-contrast T₁ maps obtained by the proposed method were in good agreement with the 2D MOLLI method both qualitatively and quantitatively.

Conclusion: The proposed method allows for free-breathing 3D ECV mapping of the whole heart within a practically feasible imaging time. The estimated ECV values from the proposed method were comparable to those from the existing method.

Keywords: cardiac T1 mapping; cardiac extracellular volume (ECV) mapping; linear tangent space alignment (LTSA); manifold learning.