Abstract: Imaging with gamma-rays is a field with important applications in fields like
astrophysics, homeland security or nuclear medicine. In this seminar, the basic theory
behind emission tomography is reviewed, with particular focus on the iterative imaging
methods and, specifically, the popular Maximum Likelihood Expectation Maximization (MLEM)
algorithm. Compton cameras and PET imaging systems are taken as a reference to illustrate
the concepts presented, and the modification of the MLEM algorithm to obtain
four-dimensional images (spatial+spectral) is discussed.