Author: Molokotima Kekana, Dennis S. Mackin, Stephen W. Peterson, Jerimy C. Polf 👨🔬
Affiliation: Department of Physics, University of Cape Town, M3D, Inc, The University of Texas MD Anderson Cancer Center, Houston 🌍
Purpose: To study the imaging characteristics of a prototype prompt gamma (PG) imaging system consisting of multiple rotating Compton cameras (CC).
Methods: The prototype CC imaging system is composed of three orthogonally positioned H3D M400 detectors placed 8 cm from the isocenter along the x, y and z axes with each detector containing four 20x20x10 mm Cadmium Zinc Telluride (CZT) crystals arranged in a 2 x 2 grid. This system was used to image a single Co-60 source while the detectors were used either together or individually. To mimic a rotating detection system, the source was placed on a platform that rotated in the XY plane. The collected Compton scatter data was first translated into the rotating coordinate frame and then reconstructed using either the back projection (BP) or MLEM reconstruction algorithm. The resulting images were used to study the ability to accurately locate the source position and to determine the spatial resolution of the static vs rotating CC setup.
Results: For the static CC system, each of the three detectors were evaluated individually, in pairs, then all three combined. There was a clear improvement in the reconstructed images using both techniques, with resolution dropping from 40.55 mm to 33.16 mm for BP, and from 10.29 mm to 5.65 mm for MLEM, when going from one to three orthogonal detectors. Position accuracy improved from 2.61 mm to 0.87 mm (BP) and from 8.19 mm to 0.87 mm (MLEM).
For the rotating CC system, there was not a noticeable difference in accuracy when comparing one or two detectors, until the detector placed along the z-axis was included, resulting in improvements in both accuracy and resolution.
Conclusion: This work has demonstrated that a rotating three axis orthogonal Compton camera configuration can improve 3D imaging over static single or double detector system.