A new contrast-to-noise ratio for image quality characterization of a coded-aperture γ camera

Highlights: • A new characterization method for image quality derived from present methods is proposed for a coded-aperture gamma camera. • The new method was evaluated by MATLAB calculation, Geant4 simulation, and experiment with a custom-made gamma camera. • The performances of the two present characterization methods and the new method were compared and analyzed. • The new evaluation method is more reliable and more practical than the two present methods. The gamma-ray imaging technique was developed and is widely used in several nuclear engineering fields. Specifically, compared with the traditional point-by-point radiation detector, the coded-aperture gamma camera has advantages of a wide field of view, high angular resolution, and high efficiency. Several methods for characterizing image quality, including the figure of merit (FOM) method and the contrast-to-noise ratio (CNR) method, were assessed and developed. These methods have their respective drawbacks depending on the circumstances. The FOM lacks reliability in exhibiting the impact of background noise fluctuation on the purity of a real image. The CNR characterizes image quality with inconsistent sensitivity while the source moves along the X and Y directions. Therefore, a new CNR method was proposed to achieve better performance and greater consistency in real imaging. With our coded-aperture imaging system developed in the laboratory, we performed simulations within the MATLAB and Geant4 platforms and real imaging experiments to analyze and compare images and the results of these three characterization methods. The results show that the new CNR method is reliable and practical in regard to real imaging performance.