Time-frequency distribution inversion of the Radon transform [imagereconstruction]

In using filtered backprojection to compute the inverse Radon transform, the ramp filter amplifies noise. Spatially invariant noise filters reduce resolution. It is desirable to filter noise where projections have no local high-frequency components. Using the short-time Fourier transform, the authors apply a time-frequency mask filter that zeroes out projections where local signal energy is below a threshold. Results show improvement over reconstructions using spatially invariant smoothing filters.