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.

伽马射线成像技术已经开发出来，并广泛应用于几个核工程领域。特别地，与传统的逐点辐射探测器相比，编码孔径伽马相机具有视野宽，角分辨率高和效率高的优点。评估和开发了几种表征图像质量的方法，包括品质因数（FOM）方法和对比噪声比（CNR）方法。这些方法根据情况具有各自的缺点。FOM在展现背景噪声波动对真实图像纯度的影响方面缺乏可靠性。当源沿X和Y方向移动时，CNR会以不一致的灵敏度来表征图像质量。因此，提出了一种新的CNR方法，以在实际成像中实现更好的性能和更大的一致性。借助我们在实验室开发的编码孔径成像系统，我们在MATLAB和Geant4平台内进行了仿真，并在实际成像实验中进行了分析和比较，并比较了这三种表征方法的结果。结果表明，新的CNR方法在实际成像性能方面是可靠和实用的。