基于原始投影正弦图的X-CT硬化校正

Harden correction based on original projection sinogram for X-CT

在X射线层析成像(X-CT,X-ray Computed Tomography)技术中,X射线束能谱的多色性将导致层析重建图像出现杯状或条状等射束硬化伪迹,降低成像质量.在分析射束硬化现象具有的3个物理属性基础上,提出了一种对原始多色投影正弦图进行操作的硬化校正方法,并从数学上证明了其校正原理.针对该方法带来的噪声放大问题,研究了一种基于高、低频信息分类处理的噪声抑制方法.计算机仿真和2种典型试件的实际CT扫描数据的硬化校正结果表明了该方法的有效性.与传统基于多项式拟合技术的校正法相比,该方法不需要事先进行建模扫描和计算,校正程序简单、实时,校正结果具有更高信噪比,且不受扫描条件限制.

The polychromatic spectrum leads to cup or streak beam hardening artifacts and reduces the image quality in X-CT （X-ray computed tomography）. A correction method for beam hardening, involving simple operations of the original polychromatic projection sinogram, was presented based on the analysis of three physics properties implied by beam hardening. Its correction principle was deduced mathematically. A noise reduction method was proposed to suppress the noise enlarged by the harden correction by processing the high-frequency and the low-frequency components in the projection sinogram respectively. The validity of this method was proved by correction results from computer simulations and CT scan experiments of two typical objects. A prior CT scan and complex operations, which were need for the conventional beam hardening correction method with the polynomial fit technique to create the correction models, were not necessary for this correction method. So it is much simpler and quicker, with better signal-noise-ratio, and not affected by scan conditions.