UCLA

Purpose

Widely used conventional 2D T₂ * 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 T₂ * 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 T₂ * imaging. This approach was tested in healthy human volunteers and in swine before and after intravenous administration of ferumoxytol.

Results

Spatial-resolution matched T₂ * images were acquired with 2-3-fold reduction in scan time using the proposed T₂ * mapping approach relative to conventional T₂ * mapping. Compared with the conventional approach, T₂ * images acquired with the proposed method demonstrated reduced off-resonance and flow artifacts, leading to higher image quality and lower coefficient of variation in T₂ *-weighted images of the myocardium of swine and humans. Mean myocardial T₂ * values determined using the proposed and conventional approaches were highly correlated and showed minimal bias.

Conclusion

The proposed non-ECG-gated, free-breathing, 3D T₂ * 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 T₂ * mapping in those with limited breath-holding capacity or arrhythmias.