A Hybrid Approach for CT-MR Brain Image Denoising Using PSO-Optimised Non-Local Means and Wiener Filtering - Figure 3. Denoised image output of the Brain MR image2 with σ=0.1 (a) Original image (b) Noisy image (c) Median Filter (d) Gaussian Filter (e) Wiener Filter (f) Non-Local Means filter (g) Particle Swarm Optimised Non-Local Means filter (h) Particle Swarm Optimised Non-Local Means Wiener filter