GATE simulation of the intrinsic radioactivity in LYSO scintillation crystals

Abstract

Many PET scanner detectors use LSO or LYSO as their scintillation crystals. Since natural lutetium contains 2.6% radioactive 176Lu, which decays β− followed by the emission of three gamma rays or internal conversion electrons, its intrinsic radioactivity needs to be considered. This work compares the energy spectrum obtained with Monte Carlo simulations of ionizing radiation transport using the 176Lu ion source defined in GATE v8.1, for different LYSO crystal sizes with experimental and analytical data. In addition, we performed a set of simulations of 88, 202 and 307 keV monoenergetic photons, the gamma rays of the isomeric transitions of the 176Hf excited states, to quantify the Compton scattered photons interacting in or escaping the crystal. Even though the optical transport effects were not simulated, the results show a very good agreement with analytical and experimental data and support the accuracy for modeling the intrinsic radioactivity of LSO/LYSO crystals with GATE.