Fig. 1. Flow chart of physical detection process simulation of coded aperture γ imaging system

Fig. 2. Pattern of the coded mask: MURA(45×45)

Fig. 3. Illustration of the geometry setup of the imaging system

Fig. 4. Two-dimensional model of photon counting estimation for detection

Fig. 5. Reconstructed images of a point source at different distances and different FOV angles: the 1^st, 2^nd, 3^rd, 4^th, 5^th and 6^th columns are positions at (-29.64°, 23.65°), (0°, 23.65°), (0°, 0°), (28.66°, 0°), (29.64°, 0°) and (-14.87°, -14.87°); the 1^st, 2^nd and 3^rd rows are the distance between the radiation source and the detector of 10 m, 15 m and 18 m, respectively

Fig. 6. Reconstruction images of 1.11×10⁶ Bq ¹³⁷Cs at distance of 4 m from detector with different FOV angles: the 1^st, 2^nd, 3^rd, 4^th and 5^th columns are positions at (-29.64°, 23.65°), (0°, 23.65°), (0°, 0°), (28.66°, 0°) and (-14.87°, -14.87°), respectively

Fig. 7. (a) Reconstructed image of 3.7×10⁷ Bq ¹³⁷Cs point source at distance of 10 m from detector with FOV angle (0°, 0°), Gaussian fitting of normalized data points of pixel intensity distribution along the X direction (b) and the Y direction (c) of a single point source

Fig. 8. Reconstructed images of two 3.7×10⁷ Bq ¹³⁷Cs sources at the distance of 10 m from detector with acquisition time of 1 s