Transmission tomography under Poisson noise using the Anscombe transformation and Wiener filtering of the projections

A minitomograph scanner for soil science was developed by the National Cent er for Research and Development of Agricultural Instrumentation (EMBRAPA/CN PDIA). The purpose of this paper is twofold. First, a statistical character ization of the noise affecting the projection measurements of this scanner is presented. Second, having determined the Poisson nature of this noise, a new method of filtering the projection data prior to the reconstruction is proposed. It is based on transforming the Poisson noise into Gaussian addi tive noise, filtering the projections in blocks through the Wiener filter a nd performing the inverse tranformation. Results with real data indicate th at this method gives superior results, as compared to conventional backproj ection with the ramp filter, by taking into consideration both resolution a nd noise, through a mean square error criterion. (C) 1999 Elsevier Science B.V. All rights reserved.