CT成像射束硬化校正方法研究

X射线CT(computed tomography)成像技术是现代医学和工业重要的诊断与检测手段。实际使用的射线源一般为宽能谱多色射线源,当多色射线穿过物体时,低能光子由于光电效应被优先吸收,因此使得射线能谱变窄。这导致CT图像的退化和杯状伪影的产生。本文系统分析了CT成像的物理过程,提出了一种简单有效的射束硬化校正方法。此方法包括三步,首先对投影图像进行散射抑制处理,其次是基于重投影的射束硬化校正,最后是基于小波变换的CT图像降噪处理。实验验证了方法的有效性。

Research on Beam Hardening Correction Method for Computed Tomography Imaging

X-ray CT imaging technology is an important diagnose and testing method for modern medicine and industry. The practical X-ray source is generally polychromatic. As a polychromatic x-ray beam passes through matter, the lower energy photons are preferen- tially absorbed mainly because of photoelectric absorption. So the spectrum becomes narrow. This leads to cupping artifacts in recon- struction image and imaging degradation. A novel beam hardening correction method, which is simple and effective, is presented here based on the systemic analysis to the physics background of X-ray CT imaging. The method includes three steps. The First step is the scatter reduction to the projection image; The Second step is beam hardening correction based on reprojection; The third step is noise depression to the CT image based on wavelet transform. In the end, the feasibility of the methods are validated by the experiment.