Non-electrocardiogram-gated, free-breathing, off-resonance reduced, high-resolution, whole-heart myocardial T₂* mapping at 3 T within 5 min

Purpose: Widely used conventional 2D T-2* approaches that are based on breath-held, electrocardiogram (ECG)-gated, multi-gradient-echo sequences are prone to motion artifacts in the presence of incomplete breath holding or arrhythmias, which is common in cardiac patients. To address these limitations, a 3D, non-ECG-gated, free-breathing T-2* technique that enables rapid whole-heart coverage was developed and validated.Methods: A continuous random Gaussian 3D k-space sampling was implemented using a low-rank tensor framework for motion-resolved 3D T-2* imaging. This approach was tested in healthy human volunteers and in swine before and after intravenous administration of ferumoxytol.Results: Spatial-resolution matched T-2* images were acquired with 2-3-fold reduction in scan time using the proposed T-2* mapping approach relative to conventional T-2* mapping. Compared with the conventional approach, T-2* images acquired with the proposed method demonstrated reduced off-resonance and flow artifacts, leading to higher image quality and lower coefficient of variation in T-2*-weighted images of the myocardium of swine and humans. Mean myocardial T-2* values determined using the proposed and conventional approaches were highly correlated and showed minimal bias.Conclusion: The proposed non-ECG-gated, free-breathing, 3D T-2* imaging approach can be performed within 5 min or less. It can overcome critical image artifacts from undesirable cardiac and respiratory motion and bulk off-resonance shifts at the heart-lung interface. The proposed approach is expected to facilitate faster and improved cardiac T-2* mapping in those with limited breath-holding capacity or arrhythmias.