Performance comparisons with R = 8.7, 8.6, and 9.9 uniform undersampling, respectively for these three datasets. For the representative slices from each dataset, the magnitude and difference images of a representative region are shown, along with PSNR, for (a) GRAPPA, (b) GRAPPA with multichannel adaptive local Wiener-filter-based denoising, (c) L1 SPIR-iT, and (d) DESIGN denoising. The PSNR-optimal choices of λ are shown for both L1 SPIR-iT and DESIGN. Note that L1 SPIR-iT is limited here by uniform undersampling.