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

Abstract

PurposeWidely 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.MethodsA 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.ResultsSpatial‐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.ConclusionThe 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.