Simulation and Detector Measurements of a Small Animal PET System for Simultaneous Multi-Tracer Imaging

Positron emission tomography (PET) is a method of measuring quantitative uptake of positron emitting tracers in vivo. Due to scanner limitations, it is not possible to measure more than one tracer’s biodistribution at a time using PET. However, many diseases would benefit from information provided by multiple tracers. We present Monte Carlo simulations of a small animal imaging system under development for imaging pure positron and positron + prompt gamma emitting radionuclides simultaneously in a new paradigm for simultaneously imaging multiple PET tracers in one scan. A detector submodule has been tested with $1.5 \times 1.5 \times 20 \mathrm{~mm}^{3}$ LYSO crystals to have an uncalibrated energy resolution of 9.8% +/- 0.9% and 9.0% +/- 2.0% at 511 keV and 1275 keV respectively. Simulation studies were conducted with positron + prompt gamma emitters ${ }^{44} \mathrm{Sc}$ and ${ }^{124} \mathrm{I}$ yielding a peak sensitivity of 7.3% and 2.2% for the 2-photon coincidences and 4.1% and 0.7% for the 3-photon coincidences with those two isotopes, respectively.