X-射线工业CT射束硬化校正中噪声的抑制

X-射线工业CT中,传统的线性化(ConventionalLinearization,CL)校正法去除射束硬化影响时,会放大投影的噪声,进而降低CT图像的信噪比(SNR)。为克服该点不足,提出了一种改进的线性化(ImprovedLinearization,IL)校正法。该方法基于投影噪声的特点,设计了一种自适应滤波器;利用该滤波器从原始投影数据中提取其噪声,求得由噪声引起的校正误差;根据该误差对校正结果进行修正以抑制投影噪声的放大。通过不同管电压和被检材质,对IL校正法进行了验证。实验结果表明,IL校正法能去除射束硬化的影响,并能有效地抑制校正过程中投影噪声的放大。与CL校正法相比,IL校正的CT图像SNR提高了约6倍。

Noise suppression in beam hardening correction of X-ray industrial CT

In X-ray industrial Computed Tomography (CT), when Conventional Linearization (CL) correction method is used to eliminate beam hardening effect, it enlarges the projection noise and thus the signal-to-noise ratio (SNR) of CT image is reduced. To overcome this shortcoming, an improved linearization (IL) correction method is proposed. Based on the character of projection noise, an adaptive filter is designed to extract the noise from the original projection data, and employs the noise to evaluate the correction errors. According to the errors, the correction results are revised to suppress the projection noise enlargement. IL correction method is examined by different source voltages and tested materials. Experimental results show IL correction method can eliminate beam hardening effect and suppress the projection noise enlargement effectively in correction process. Compared with CL correction method, IL correction improves the SNR of CT image about 6 times.