I have multi-shell HARDI data from b = 1000 to 10,000 s/mm^2 with 64 directions per b-value shell. Along with the b0 images (n = 11), there are roughly 750 total volumes. This doesn’t happen consistently but sometimes if I use a kernel size such as 11x11x11 or 9x9x9, I get noise maps with voxel patches of zero noise. If I drop down to say 7x7x7, the issue is resolved. I wonder though, since the kernel size should be larger than the number of total volumes being denoised, if using a smaller kernel will not denoise the data optimally.
Is this a known issue with datasets that are large such as this one?