工业CT重建图像中边缘梯度效应引起的高频伪影

High-frequency artifacts in industrial CT reconstruction images due to the exponential edge-gradient effect

为研究伪影对大型工件内部密度锐变区域高对比度微小缺陷检测的影响,从一个简单的轴对称断层模型出发,计算了边缘梯度效应引起的通过物体内部不同材料交界面处的射束的投影偏差。并研究采样相位的影响,探讨了由此偏差引起的重建图像中的高频伪影的表现形式。计算结果表明,高频伪影具有相当的强度,且具有与缺陷相似的表现形式,从而影响工业CT的检测能力。结合点扩散过程,高频伪影强度的计算为评估工业CT边缘处的缺陷检测能力提供了理论依据。

This paper analyzes the influence of high-frequency artifacts on the detection of high-contrast micro defects in regions of sharp density transitions inside large workpieces in industrial CT systems. The analysis uses a simple axisymmetric model to theoretically calculate the projection error due to the exponential edge-gradient effect near the boundaries of two different materials. The analysis is used to investigate the resulting high-frequency artifacts in the reconstructed images. The results show that the high-frequency artifacts are similar to micro defects in the form, which will reduce the detection ability of the CT systems. The results provide theoretic framework for the assessment of detection ability at the edges in industrial CT systems based on knowledge of the point spread.