Monte Carlo Simulation for Distance and Absorbed Dose Calculations in a PET-CT Facility by Using MCNP-X

Modern PET/CT clinics consist of a scanner room housing the double gantry PET/CT unit and a control area. These areas should be considered as a parts of facility that must be protected. The scanner room, quiet rooms, and frequently the hot lab require structural shielding to protect staff and personnel in surrounding areas. The 511 keV photons from the PET positron emitting isotopes are the source term for the quiet rooms and the hot lab, while both the 511 keV photons and the multi-energetic spectrum of x-rays from the CT unit must be considered for the scanner room. In this study, we have developed a 3D (three dimensional) model of PET-CT scanner room by using MCNP-X (version 2.4.0) Monte Carlo code. We considered the distance factor in PET-CT facility for the amount of exposure radiation dose received by staff. In terms of exposed radiation dose of staff, we obtained the well agreement on distance factor calculations by using Monte Carlo method. We achieved a good agreement between MCNP-X results and clinical experimental results.