A gamma-ray imaging method for multiple radionuclides and low-activity radioactive sources

Gamma-ray coded-aperture imaging technology has important applications in the fields of nuclear security, isolated source detection, and the decommissioning of nuclear facilities. However, artifacts can reduce the quality of reconstructed images and affect the identification of the intensity and location of radioactive sources. In this paper, a gamma-ray coded-aperture imaging method based on primitive and reversed coded functions (PRCF) was proposed to reduce imaging artifacts. Building on this, the PRCF method was improved by integrating energy spectral information collected by the detector. By selecting energy intervals corresponding to characteristic energies of different radioactive sources for data filtering, the imaging capability of the PRCF method was further enhanced for multiple radioactive sources. Through simulation, the selection range of the correction factor in the PRCF method was determined. Single-source and multi-source imaging experiments were conducted using the self-built coded-aperture imaging system based on a CdZnTe pixel detector, and the selection criteria for the energy interval ranges of different radioactive sources were established. Compared with the conventional maximum likelihood expectation maximization (MLEM) method, the improved PRCF method not only effectively reduced artifacts and enhanced the imaging quality, but also ensured the accuracy of imaging results for multiple radioactive sources. Moreover, through imaging experiments using low-activity ¹³⁷Cs and high-activity ²⁴¹Am and ¹³³Ba, it was demonstrated that the PRCF method can achieve low-count imaging in complex environments, providing a solution for imaging low-activity radioactive sources.