Free-Running Three-Dimensional Cardiac Extracellular Volume Mapping in a Single Scan With Mid-Scan Contrast Injection

To develop a new method for free-running three-dimensional (3D) extracellular volume mapping of the heart in a single scan with mid-scan contrast injection.

3D cardiac MR imaging was performed with a single scan that acquired k-space data continuously using an inversion recovery (IR) sequence with a spoiled gradient-echo readout. Contrast agent was injected in the middle of the scan. Dynamic images were reconstructed utilizing a linear tangent space alignment (LTSA) model. The pre- and postcontrast T₁* was estimated by finding the best fit between the measured signal and the MR signal model, which assumes a linearly time-varying R₁* that accounts for T₁* changes after the contrast agent injection. Cardiac cine images were synthesized by fitting with the signal model. The 3D ECV mapping was performed using the 3D pre- and postcontrast T₁* maps and the measured hematocrit level from blood sampling.

The feasibility of the proposed method was demonstrated through in vivo studies conducted on three healthy subjects using a 3T MR scanner. The ECV maps from the proposed method showed good agreement with those from the MOLLI method. The estimated average myocardial ECV from the proposed and MOLLI methods was 29.82% ± 2.45% and 29.28% ± 2.15%, respectively. The cine images from the proposed method successfully captured the heart's motion. The estimated ejection fraction was 63.3% ± 8%, which was in good agreement with literature values.

We developed a novel approach that allows 3D cardiac ECV mapping in a single, free-running, continuous 15-min scan with mid-scan contrast injection.