Simulation and experimental study of the angle-dependent sensitivity of the thick pinhole used for gamma imaging

The angle-dependent sensitivity of rotationally symmetric thick pinholes used for gamma imaging was investigated using a geometric algorithm and Monte Carlo numerical simulations for the thick pinholes with different structural parameters. The effect of the pinhole diameter, the thickness of the straight-hole portion, and the half conical angle were analyzed. The point source was demonstrated to be a feasible replacement for the homogeneous plane source through theoretical deduction, numerical calculations, and experimental measurements of the angle-dependent sensitivity. A small quasi-point source was established based on a 10K curie level 60Co gamma ray source in the experimental measurement of the angle-dependent sensitivity. The image position remained unchanged and image distortion was avoided by rotating the thick pinhole around the pinhole center. The experimental result was in good agreement with the theoretical calculation, indicating the potential of this measurement method.