Design and performance evaluation of a 4[formula omitted]-view gamma camera with mosaic-patterned 3D position-sensitive scintillators

Abstract

Gamma hotspots imaging is of dramatic demand in nuclear-related industrial and homeland security activities such as nuclear facilities monitoring, nuclear emergency response and border inspection. Gamma cameras with mechanical collimation (i.e., coded-aperture) have reduced sensitivity, limited FOV and are typically heavy-weighted. Compton cameras with electrical collimation can achieve higher sensitivity as well as being capable of performing portable 4π-view imaging. However, imageable isotopes of Compton cameras are limited to middle- or high-energy ones. We have previously proposed the concept to image gamma hotspots with a 3-D position-sensitive scintillation detector. This approach achieves high sensitivity, 4π-view FOV and is effective in a wide energy range. In this work, we present a novel gamma camera design aiming for high-resolution gamma imaging. The proposed detector consists of interspaced GAGG(Ce) scintillators that form a mosaic pattern, which is coupled to SiPM arrays on both ends. 3-D photon interaction position information is measured with a dual-end-readout technique. The measured interaction positions for detected photon events are rebinned into the projection data, and the gamma image is reconstructed using a maximum likelihood expectation maximization (MLEM) algorithm. We perform Monte Carlo simulations and experiments to evaluate the performance of the proposed gamma camera design for imaging 99mTc and 137Cs sources. Results show that the proposed gamma camera achieves a positioning accuracy of less than 1° for a 99mTc source and 3° for a 137Cs source. It can clearly resolve two 99mTc sources with 10° separation and two 137Cs point sources with 23° separation, as well as a 2 × 6 99mTc point-source-array with 20° separation clearly. We conclude that the proposed gamma camera design is profitable in portability, FOV, sensitivity, image resolution and energy range. It has promising application potential in fast and accurate radiation monitoring tasks in nuclear security applications.