Browsing by Author "Censor, Yair"

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String-averaging expectation-maximization for maximum likelihood estimation in emission tomography
(2014-05-01)
Helou, Elias Salomao
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Censor, Yair
;
Chen, Tai-Been
;
Chern, I-Liang
;
De Pierro, Alvaro Rodolfo
We study the maximum likelihood model in emission tomography and propose a new family of algorithms for its solution, called string-averaging expectation maximization (SAEM). In the string-averaging algorithmic regime, the index set of all underlying equations is split into subsets, called \'strings\', and the algorithm separately proceeds along each string, possibly in parallel. Then, the end-points of all strings are averaged to form the next iterate. SAEM algorithms with several strings present better practical merits than the classical row-action maximum-likelihood algorithm. We present numerical experiments showing the effectiveness of the algorithmic scheme, using data of image reconstruction problems. Performance is evaluated from the computational cost and reconstruction quality viewpoints. A complete convergence theory is also provided.