Fig. 1. Compton imaging principle. (a) Typical structure of Compton camera; (b) Compton imaging principle diagram (grid in figure is imaging plane, A and B are interaction positions in scattering layer and absorption layer, respectively, θ is Compton scattering angle, and O is one point on reconstructed cone surface)

Fig. 2. Schematic diagram of Compton camera system

Fig. 3. Pictures of GAGG(Ce) crystal, Si-PM, and detector. (a) Before packaging of GAGG(Ce) crystal; (b) after packaging of GAGG(Ce) crystal; (c) Si-PM; (d) three views after detector is packaged

Fig. 4. Row/column readout circuit^[18]

Fig. 5. Compton camera experimental platform

Fig. 6. Flowchart of SOE reconstruction algorithm

Fig. 7. 2D scattering dot plot of detector (bright spots in figure correspond to detector pixels)

Fig. 8. Energy response of scattering layer and fitting curve of all-energy peak-to-energy [energy marked in Figs. 8(a)-(e) is energy corresponding to peak position of all-energy peak of interest). (a) ²⁴¹Am energy spectrum; (b) ¹³³Ba energy spectrum; (c) ¹⁵²Eu energy spectrum; (d) ²²Na energy spectrum; (e) ¹³⁷Cs energy spectrum; (f) full energy peak position-energy fitting curve

Fig. 9. ¹³⁷Cs energy spectrum of single pixel

Fig. 10. Reconstruction result and angular resolution. (a) Imaging result; (b) relative strength change of reconstructed section in Fig. 10(a) (dashed frame corresponds to 0.8I, and I is peak intensity)

Fig. 11. Simulation scenario experimental configuration and experimental result. (a) Experimental scenario setting; (b) simulation scene experimental result