Impact of denoising on precision and accuracy of saturation-recovery-based myocardial T 1 mapping.

Purpose: To evaluate the impact of a novel postprocessing denoising technique on accuracy and precision in myocardial T ₁ mapping.
Materials and Methods: This study introduces a fast and robust denoising method developed for magnetic resonance T ₁ mapping. The technique imposes edge-preserving regularity and exploits the co-occurence of spatial gradients in the acquired T ₁ -weighted images. The proposed approach was assessed in simulations, ex vivo data and in vivo imaging on a cohort of 16 healthy volunteers (12 males, average age 39 ± 8 years, 62 ± 9 bpm) both in pre- and postcontrast injection. The method was evaluated in myocardial T ₁ mapping at 3T with a saturation-recovery technique that is accurate but sensitive to noise. ROIs in the myocardium and left-ventricle blood pool were analyzed by an experienced reader. Mean T ₁ values and standard deviation were extracted and compared in all studies.
Results: Simulations on synthetic phantom showed signal-to-noise ratio and sharpness improvement with the proposed method in comparison with conventional denoising. In vivo results demonstrated that our method preserves accuracy, as no difference in mean T ₁ values was observed in the myocardium (precontrast: 1433/1426 msec, 95%CI: [-40.7, 55.9], p = 0.75, postcontrast: 766/759 msec, 95%CI: [-60.7, 77.2], p = 0.8). Meanwhile, precision was improved with standard deviations of T ₁ values being significantly decreased (precontrast: 223/151 msec, 95%CI: [27.3, 116.5], p = 0.003, postcontrast: 176/135 msec, 95%CI: [5.5, 77.1], p = 0.03).
Conclusion: The proposed denoising method preserves accuracy and improves precision in myocardial T ₁ mapping, with the potential to offer better map visualization and analysis.
Level of Evidence: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1377-1388.
(© 2017 International Society for Magnetic Resonance in Medicine.)