1987/09/01 by Donald L. Snyder, Michael I. Miller, Lewis J. Thomas +1 · 2 citations
Medicine · Engineering · #Medical Imaging Techniques and Applications #Advanced X-ray and CT Imaging #Advanced MRI Techniques and Applications
paper · doi:10.1109/tmi.1987.4307831
openalex publication_date 1987/09/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/27
Images produced in emission tomography with the expectation-maximization algorithm have been observed to become more noisy and to have large distortions near edges as iterations proceed and the images converge towards the maximum-likelihood estimate. It is our conclusion that these artifacts are fundamental to reconstructions based on maximum-likelihood estimation as it has been applied usually; they are not due to the use of the expectation-maximization algorithm, which is but one numerical approach for finding the maximum-likelihood estimate. In this paper, we develop a mathematical approach for suppressing both the noise and edge artifacts by modifying the maximum-likelihood approach to include constraints which the estimate must satisfy.