title: On the relation between the ISRA and the EM algorithm for positron emission tomography.
abstract: The image space reconstruction algorithm (ISRA) was proposed as a modification of the expectation maximization (EM) algorithm based on physical considerations for application in volume emission computered tomography. As a consequence of this modification, ISRA searches for least squares solutions instead of maximizing Poisson likelihoods as the EM algorithm. It is shown that both algorithms may be obtained from a common mathematical framework. This fact is used to extend ISRA for penalized likelihood estimates.
authors.affiliation: Inst. de Matematica Estatistica, e Ciencia da Computacao, Univ. Estadual de Campinas, Sao Paulo.
authors.forename: A R
authors.initials: AR
authors.lastname: De Pierro