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Mitigating Impacts of Tissue-Heterogeneity and Noise Bias on MP-PCA Denoising for High-Quality Diffusion MRI
Cornelius Eichner1, Michael Paquette1, Angela D Friederici1, and Alfred Anwander1
1Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
Informed MP-PCA significantly improves the denoising-performance on advanced dMRI data with high resolutions and strong diffusion-weighting. Specifically, iMP-PCA reduces global noise levels while retaining local tissue-related signal differences. 
Figure 3: A The iMP-PCA kernel is defined by similarity of voxels within a larger region (dotted blue). Best matching voxels are selected for denoising. Every voxel potentially has its own kernel shape, depending on the underlying tissue. B The voxel-wise intra-kernel standard variation (SD) shows tissue-preserving characteristics of iMP-PCA. Informed adaptive kernels result in separation of tissue types in cortex and specific white matter tracts (see enlargements).
Figure 4: A iMP-PCA denoising with real-valued dMRI data is superior with improved signal-attenuation and reduced noise B Left: iMP-PCA denoising retains tissue-related, large signal-variations in highly anisotropic white matter regions - however, it reduces noise in less anisotropic regions, such as in gray matter for all b-shells (ratio). Right: Real-valued dMRI denoising impact becomes evident at b=2000 with a stronger noise attenuation in central grey matter regions (ratio).