基于投影的CT图像金属伪影非线性权重校正

Projection-based metal artifacts reduction in CT images via nonlinear weights

为抑制计算机层析造影(CT)系统重建图像中出现的金属伪影,提高图像的质量,采用一种基于金属投影非线性权重衰减的方法进行校正。对原始的投影直接重建,在得到的图像中利用阈值分离出金属区域,并重新对该金属区域进行投影,便得到原始的投影中金属投影的区间。只对该金属投影进行合适的非线性衰减。再用传统的滤波反投影方法重建图像。数值模拟表明,该方法不但能基本消除由射线硬化和射线剧烈衰减而引起的金属伪影,而且能保留金属信息,同时能增强金属区域不同部分之间的对比度,使得重建图像的质量得到很大的提高。该算法计算复杂度较小,实现简单,具有较高的实用价值。

A metal artifacts reduction method using nonlinear weights was developed to suppress metal artifacts in X-ray CT （computerized tomography） images to improve the image quality. The metal projection regions were identified by re-projecting the metal regions extracted from an initial reconstruction without modification. The metal projections were non-linearly attenuated to a suitable level without changing the projection in the nonmetal regions. The image was reconstructed by a filtered back projection algorithm using the modified projection. Numerical simulations show that the method not only effectively suppresses metal artifacts derived from beam hardening and high attenuation, but also preserves the metal information, and enhances the contrast of complicated structures in the metal region. The method is very practical because of its simplicity, effectiveness, and ease of implementation.