UC Santa Cruz

Utilizing prompt gamma emissions in radionuclides has potential to enable newopportunities in Positron Emission Tomography (PET). The Compton scattering and imaging of the prompt gamma-ray provide extra information that aid in correcting for positron range error and as a consequence, enable an improved system sensitivity and image quality. In addition, by coincidence windowing the 511 keV positron annihilation photons and the prompt-gamma, it is possible to differentiate between multiple PET tracers since in many nuclides, prompt gammas are emitted with energy unique to the nuclide and are emitted almost simultaneously at the time of decay before positron annihilation can occur. In this study, we explore this concept through a simulation study. In order to demonstrate the feasibility of imaging prompt-gamma emitting radionuclides combined with PET, we implement a Maximum-Likelihood Expectation Maximization (MLEM) image reconstruction algorithm for Compton Camera (CC) imaging on an existing dual-panel Cadmium Zinc Telluride (CZT) PET system simulated by a Monte Carlo based simulation toolkit GEANT4 Application for Tomographic Emission (GATE). The CZT detector is a good candidate for a hybrid imaging modality because of its large cross-section for Compton scattering at high energy, its good energy resolution (> 5 % full width half maximum at 511 keV), and a wide dynamic range to measure energy from 100 keV to 1.2 MeV.