 Ordered subset expectation maximization

Ordered Subset Expectation Maximization (OSEM) is an iterative algorithm used in statistical imaging, particularly in the field of positron emission tomography (PET) and single-photon emission computed tomography (SPECT). It is a variation of the Expectation-Maximization (EM) algorithm, which is used for finding maximum likelihood estimates of parameters in probabilistic models, especially those involving latent variables.