Effect of CZT System Characteristics on Compton Scatter Event Recovery

Abstract

Improving 511 keV photon detection sensitivity is a common goal for positron emission tomography (PET) system designers. One attractive approach to increase sensitivity is recovering events that are normally rejected. The kinematics of Compton scattering can be used to recover the line of response through direction difference angle (DDA). The uncertainty of DDA is determined by the energy and spatial resolution of a system. In this paper, we evaluated the performance of small animal cadmium zinc telluride-based PET systems with energy resolution of 1%, 4%, and 6% and different spatial resolution based on prior work for guiding new design efforts. Designs with energy resolution limited by counting statistics and by electronic noise were considered. The influence of modifying the conventional energy window and uncertainty of DDA was investigated. For a system with 4% energy resolution and limited by electronic noise, the figure of merit of noise equivalent count increases by 65% as the lower energy bound increases from 471 to 493 keV. If the system-wide energy resolution becomes worse than 4% of the full width half maximum at 511 keV, going to a pixel size finer than 1 mm has very limited effect in reducing total angular uncertainty. For a system with 1% energy resolution, as the spatial resolution improves from 1 mm to 0.5 mm, the contrast-to-noise ratio increases by 9%.

Quantum Entanglement Filtering: A PET Feasibility Study in Imaging Dual-Positron and Prompt Gamma Emission via Monte Carlo Simulation

“…This design can achieve an x-y gamma interaction resolution of 1×2.5 mm via charge sharing information and sub-millimeter z-resolution with the use of cathode-to-anode ratio [46]. With this system design, we have shown accurate Compton scatter event recovery with an average polar angular resolution of 0.67 o for 1×1×1 mm interaction resolution and 2.65 o for 1×3×1 mm interaction resolution [47], [48]. We have implemented this work in simulation due to the need for accurate positioning.…”

Design Study of a Dedicated Head and Neck Cancer PET System

“…However, in the LYSO system, the poor energy resolution dominated the recovery error, so changing crystal size did not make an obvious influence. Details can be found in our previous study [57].…”

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