实际工业CT系统在机械安装时很难满足经典CT图像重建公式所要求的几何对准关系。当不满足该几何对准关系时，利用经典CT重建公式重建的图像将出现几何伪影，从而影响对CT图像的判读。针对扇束CT扫描系统，研究了几何参数误差对一根细丝断层图像的影响，导出了描述细丝断层图像伪影形态的包络线方程，并基于包络线给出了几何伪影的形态分类、演化规律和性质，同时给出了几何参数误差的调整方法。

It is very difficult to modulate a real industrial CT system to satisfy the geometric alignment relations required by the conventional CT image reconstruction formula. A misalignment will result in geometric artifacts in the image reconstructed by the conventional formula, which may cause a misjudgment. In this paper, we study the impact of geometric parameters errors for fan-beam system on the reconstructed images of a thin wire. We derive the envelope function which describes geometric artifact configuration in the image. Based on the envelope function, we give a classification, the evolution regularity and the characteristics of geometric artifacts. Besides, we give a method to adjust the errors of geometric parameters.