William T Clarke1 and Mark Chiew1
1Wellcome Centre for Integrative Neuroimaging, NDCN, University of Oxford, Oxford, United Kingdom
1Wellcome Centre for Integrative Neuroimaging, NDCN, University of Oxford, Oxford, United Kingdom
Despite visually denoising MRS data it is not clear whether low rank denoising decreases uncertainty in metabolite concentrations. We use simulation and in vivo reproducibility to show that denoising is beneficial, but much less than is apparent.
Figure 1. Denoising of a single identical Lorentzian peak with independent noise. The black line shows the noiseless signal, the red line shows a single voxel’s data after denoising (no denoising applied in “Noisy”, all spectra mean shown in “Avg”). The Shaded grey region shows ± two standard deviations of all 128 spectra. All denoising approaches show high apparent noise level reduction, but LP denoising does not show a reduction in peak amplitude variance.
Figure 5. Voxel-wise maps of mean metabolite concentration (left, red/yellow) and standard deviation of metabolite concentration (blue) across the ten repeated acquisitions for each denoising case. Data is shown for three metabolites and is overlaid on a T1w structural image. Colour scales are fixed for each metabolite.
