  Positron Emission Tomography (PET) is a Nuclear Medicine technique that
creates images that allow the study of metabolic activity and organ function
using radiopharmaceuticals. Continuous improvement of scintillation detectors
for radiation in PET as well as improvement in electronic detectors (e.g.,
SiPMs) and signal processing, makes the field of PET a fast and changing
environment. If industry desires to build new systems implementing these
technological improvements, it is of its interest to develop modelling
strategies that can provide information on how to build them, reducing time and
material costs. Bearing this in mind three different PET configurations, were
simulated in Geant4, to determine which one presented the best performance
according to quality parameters such as spatial resolution (SR), coincident
time resolution (CTR) and acceptance value (A). This was done with three
different (in size) pairs of LYSO crystals + SiPM detectors. It was found that
the 2 Modules system presented worst results than the two Ring detector
configurations. Between the Ring configurations the first was marginally better
than the second.
