Figure 5.

Flowchart of the multiscale denoising process, starting from the noisy sinogram Z and resulting in the estimate of the streak-free sinogram, both of size . First, Z is vertically rescaled into a sinogram Z ₀ of size , , through the binning operator . Then, by repeated horizontal binning , Z ₀ is progressively downscaled into a series of sinograms , , each of size . The coarsest scale noisy input is denoised with BM3D to produce . Then, recursively for , the noisy input is denoised by BM3D to produce ; this definition of means that the coarse-scale horizontal components of Z _k are replaced by . The PSD for each scale is estimated as described in Section 3.3.2. The resulting estimate of the horizontal debinning (size ) similarly replaces the coarse-scale vertical components of Z to obtain the full-size estimate .