REPAIRit: Improving Myocardial Nulling and Ghosting Artifacts of 3D Navigator-Gated Late Gadolinium Enhancement Imaging During Arrhythmia

Background: Cardiac 3D navigator-gated late gadolinium enhancement (LGE) imaging is important for assessment of left atrial fibrosis, but the image quality is often degraded due to arrhythmia.

Purpose: To investigate a novel 3D LGE sequence with improved myocardial nulling and reduced ghosting artifacts during arrhythmia.

Study type: Prospective.

Population: Arrhythmia patients (n = 14).

Sequence: The proposed technique, REPAIRit (Regrowth Equalization Pulse for Arrhythmias in Inversion Recovery with automatic inversion time calculation), inserts a saturation pulse with a dynamic flip angle into the 3D LGE sequence to minimize arrhythmia-induced signal fluctuations. Using ShMOLLI (shortened modified Look-Locker imaging) to estimate myocardial T₁ , REPAIRit automatically calculates the optimal inversion time (TI) based on Bloch equations.

Assessment: REPAIRit LGE and the standard LGE were compared with simulations, phantom imaging, and patient studies. Patient images were assessed quantitatively, based on ghost-to-noise ratio (GNR), blood signal-to-noise ratio (SNRb), myocardial signal-to-noise ratio (SNRm), and blood-to-myocardium contrast-to-noise ratio (CNR), and qualitatively on a 4-point scale. Patients were subgrouped based on the presence of arrhythmia to assess the image quality difference.

Statistical tests: The two LGE sequences were compared by Student's t-test and Wilcoxon signed-rank test. The two patient-subgroups were compared using Welch's t-test and Wilcoxon rank-sum test.

Results: In 14 analyzed patients, REPAIRit LGE significantly lowered GNR (1.25 ± 0.41 vs. 1.42 ± 0.42, P = 0.04), reduced SNRm (1.90 ± 0.60 vs. 3.16 ± 1.66, P = 0.01), improved ghosting artifact scores (2.5 ± 0.6 vs. 2.2 ± 0.9, P = 0.03), myocardial nulling scores (2.7 ± 0.5 vs. 2.3 ± 0.7, P = 0.02), and atrial quality scores (2.8 ± 0.3 vs. 2.4 ± 0.8, P = 0.03) compared with the standard LGE. Comparing patients with arrhythmia (n = 6) to those without (n = 8) during the scan, the former had lower left ventricular (LV) myocardial T₁ s (430 ± 26 msec vs. 469 ± 39 msec, P = 0.06) but similar blood T₁ s (318 ± 55 msec vs. 316 ± 27 msec, P = 0.96), and significantly lower blood SNR (5.2 ± 1.8 vs. 9.2 ± 3.0, P = 0.01) and significantly worse image quality (P = 0.01 for REPAIRit and P = 0.03 for standard).

Data conclusion: REPAIRit improves myocardial nulling and reduces ghosting artifacts of 3D LGE under arrhythmia.

Level of evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:688-699.