Development and optimization of a virtual model for the joint calculation of efficiency calibration and trajectory length in TGS emission measurements

摘要: In tomographic gamma scanning (TGS) emission measurements, conventional methods typically compute efficiency calibration and trajectory length separately, which leads to reduced overall computational efficiency.Our analysis reveals a spatial consistency between the efficiency calibration and trajectory length. Building on this physical correlation, this paper proposes a novel joint calculation model, that simultaneously resolves both efficiency calibration and trajectory length. To further improve emission image quality and nuclide activity inversion accuracy, the radiation sources within voxels are treated as uniformly distributed multi-point sources, constructing a joint calculation model under the multi-point source and detector framework. For model verification, three calculation methods under the single-point source emission mode (point-point model, average trajectory model, and the point source mode of this model) and three multi-point source emission modes (uniform 8-point,uniform 64-point, and uniform volume source) were established.The Maximum Likelihood Expectation Maximization algorithm (MLEM) was used to reconstruct images of volume sources at three different locations in seven different waste drums.The results show that this model significantly improves computational efficiency, with multi-point source modes performing better than single-point source modes; in multi-point source modes, the distribution of radiation source points within voxels is not better with more points, with the uniform 64-point mode showing the best comprehensive performance, and demonstrating significant improvements in both emission image quality and nuclide activity accuracy compared to traditional point-to-point and average trajectory models.