Double photon coincidence crosstalk reduction method for multi-nuclide Compton imaging

Abstract

Compton imaging based on Compton scattering kinematics has the potential to visualize multi-nuclides by discriminating the total energy of Compton scattering and photoelectric absorption events. This feature enables us to perform multi-tracer imaging that reflects different functional information in nuclear medicine, resulting in a definitive diagnosis and being useful for biological and medical research. One of the challenges with multi-nuclide imaging is the crosstalk artifacts caused by scattered photons of higher energy gamma-rays. In this study, we investigated the potential benefits of the double photon coincidence detection as a drastic crosstalk reduction method. Coincidence detection of successive gamma-rays can differentiate nuclides and reduce the background caused by other nuclides' gamma-rays because some nuclides emit two or more gamma-rays in rapid succession. In this study, we focused on the coincidence detection of a Compton event and a photoelectric absorption event, and we showed simultaneous double photon emitter imaging of 111In and 177Lu with a ring-type Compton imaging system. The artifacts caused by other nuclides' gamma-rays were reduced by extracting Compton events coincident with photoelectric absorption events. The coincidence Compton images demonstrated a signal-to-background ratio improvement of 1.1–1.7 times over the one of no-coincidence Compton images, despite a drop in intrinsic detection efficiency of the order of 10-2. This strategy of directly reducing crosstalk will be useful in other combinations imaging such as of 111In (or 177Lu) and a positron emission tomography nuclide.