Enhanced 2D Spiral Cine DENSE MRI Using Low-Rank Denoising for Improved Apparent Signal-to-Noise Ratio, Spatial...

To develop a denoising technique for displacement encoding with stimulated echoes (DENSE) MRI that improves spatial resolution, efficiency, and accuracy, and enhances accessibility by implementing DENSE MRI at 0.55 T.

We developed a low-rank denoising technique, which leverages multidimensional spiral cine DENSE MRI data for empirical noise estimation via Monte Carlo simulation combined with automatic noise suppression. Thirty-six subjects (16 healthy, 20 with heart disease) were scanned at 3 T with breath-hold standard-resolution 2D cine DENSE (2.8 × 2.8 mm²) in a short-axis slice of the heart. In 10 healthy subjects, high-resolution DENSE with 1.2 × 1.2 mm² was acquired. Apparent signal-to-noise ratio (SNR), phase SNR, scan efficiency (SNR per heartbeat per unit voxel size), and standard deviation of segmental circumferential myocardial strain (E_cc) were compared with Wilcoxon signed-rank tests (p < 0.05 considered significant). High-resolution and standard-resolution DENSE results were compared using Bland-Altman analysis. Lastly, we scanned seven healthy subjects at 0.55 T and 3 T, and compared E_cc results.

Apparent magnitude SNR, phase SNR and scan efficiency were significantly improved after denoising in both standard-resolution and high-resolution DENSE (all p < 0.01). Bland-Altman analysis showed denoised high-resolution DENSE E_cc had smaller mean differences (non-denoised: 0.028 vs. denoised: 0.009) and narrower limits of agreement (non-denoised: [-0.072, 0.127] vs. denoised: [-0.048, 0.065]), indicating improved accuracy. Strain measurements from denoised DENSE at 0.55 T showed good agreement with those from 3 T, demonstrating feasibility of DENSE MRI at 0.55 T.

Our proposed denoising technique may allow DENSE MRI with improved spatial resolution, efficiency, and accuracy, and enhanced accessibility at 0.55 T.