边界体素处理方式对层析γ扫描技术的透射重建质量的影响

用层析γ扫描技术(TGS)对废物桶进行透射重建时,通常将桶边界处的不规则体素近似为规则的立方体体素。为探究边界体素处理方式对透射重建质量的影响,采用代数重建算法(ART)和极大似然期望最大化算法(MLEM),用MCNP程序分别模拟计算将边界体素分别视为不规则体素和规则体素的两种处理方式对透射重建质量的影响。计算结果表明:将不规则的桶边界体素近似为规则的立方体体素会使透射重建所得线性衰减系数出现较大误差,应采用实际的不规则桶边界体素方式进行透射重建,且相对于ART算法,MLEM算法更适合作为TGS技术的透射重建算法。

Influence of Waste Drum Edge Voxels Treatment Mode on Quality of Transmission Reconstruction in Tomographic Gamma Scanning

The irregular voxels of waste drum at the periphery are regarded as regular voxels in tomographic gamma scanning.In order to explore the influence of treatment modes of voxels at the periphery of waste drum on the quality of transmission reconstruction,MCNP code was used to compare the irregular voxels mode and regular voxels mode,with algebraic reconstruction technique (ART) and maximum likelihood expectation maximization (MLEM) respectively.The results show that irregular voxels treatment mode of waste drum at the periphery is preferable,for the reason that by regular voxels treatment mode,there will be a relatively big discrepancy between reconstructed linear attenuation coefficients (LACs) and the real ones,which may cause failure in accurately reconstructing activity in upcoming emission reconstruction stage,and that compared with ART algorithm,MLEM algorithm is a better choice to the transmission reconstruction algorithm.