为去除X射线CT图像中的环形伪影,建立了一种投影数据预处理方法。该方法通过对各角度投影数据逐一进行分段多项式拟合的方式建立异常探元的备选校正因子集合,再根据备选校正因子的概率密度分布确定最可几校正因子。介绍了方法的物理依据、原理及其实现步骤,并分析了其在复杂条件下的适应性。结果表明:该方法对稀疏环形伪影、密集环形伪影以及伴随强噪声污染的CT图像环形伪影均可去除;与中值滤波等方法相比,可以更好地保持图像的空间分辨率。该方法可用于多材质检测对象CT图像的处理。

In this paper, a novel preprocessing technique is proposed for the correction of ring artifact in X-ray CT image. By fitting each projection in sinogram image with piecewise polynomial, a set of candidate correction factors for mis-calibrated detector is created and then the factor with maximum probability occurrence is picked out to rectify the projection data. Principle and procedure of the method is illustrated. Tests under different condition show that, sparse or continuous ring artifact in the CT image can both be well rectified effectively, while spatial resolution of the image preserved. CT images for multi-material object can also be corrected by the method.