Background: Monte Carlo methods are extensively used in
Nuclear Medicine to do a variety of problems that are difficult
to study by an experimental or analytical approach, so researchers
use the Monte Carlo simulation in designing the scanners or
evaluating their performance and optimizing the functional
parameters before commercialization. In this study, one of the
three PET/CT imaging systems currently running in all over the
world, was simulated using Monte Carlo simulation.
Methods: The PET scanner of the Siemens Biograph6 PET/CT
system was simulated using MCNPX simulation Monte Carlo
code. This PET ring -83 cm in diameter- consists of 48 block
detector in transaxial direction. Each block is made of 13.13 LSO
crystals. whole scanner consists of 24,336 crystals arranged in 3
detection rings in axial direction. The surface area and the
thickness of the individual crystals are 4.4mm2 and 20mm.
.As shown in fig.1.a and b, in this simulation, there is mird
phantom inside this PET ring. A spherical 511 keV gamma source
with 2cm radius is positioned the center of liver to model a tumor
in that place.