An Evaluation of the Use of Sieves for Producing Estimates. Of Radioactivity Distributions with the EM Algorithm for PET

Reconstructions of spatial-distributions of radioactivity produced using maximum-likelihood estimation in positron-emission tomography exhibit noise-like artifacts in the form of sharp peaks and valleys located randomly throughout the image field. These become increasingly apparent with each stage of iteration when the expectation-maximization algorithm is used to produce the maximum-likelihood estimate numerically. In this paper, we present a preliminary evaluation of the use of Grenander´s method of sieves to reduce these undesirable artifacts.