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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。
X-ray computed tomography (CT) imaging is an important diagnostic and testing tool in modern medicine and industry. The actual radiation source is generally a broad spectrum multi-color ray source. When multi-color rays pass through an object, the low-energy photons are preferentially absorbed due to the photoelectric effect, thereby narrowing the energy spectrum of the ray. This leads to the degradation of CT images and the generation of cup artifacts. This paper systematically analyzes the physical process of CT imaging and proposes a simple and effective beam hardening correction method. This method consists of three steps: firstly, the projection image is suppressed by scattering; secondly, the beam-hardening correction is based on reprojection; finally, the CT image denoising based on wavelet transform is performed. Experiments show the effectiveness of the method.