Zhao Yunsong, Li Mengfei
School of Mathematical Sciences, Capital Normal University, Beijing, China.
Beijing Higher Institution Engineering Research Center of Testing and Imaging, Beijing, China.
PLoS One. 2015 Dec 10;10(12):e0144607. doi: 10.1371/journal.pone.0144607. eCollection 2015.
In this paper, we propose an iterative beam hardening correction method that is applicable for the case with multiple materials. By assuming that the materials composing scanned object are known and that they are distinguishable by their linear attenuation coefficients at some given energy, the beam hardening correction problem is converted into a nonlinear system problem, which is then solved iteratively. The reconstructed image is the distribution of linear attenuation coefficient of the scanned object at a given energy. So there are no beam hardening artifacts in the image theoretically. The proposed iterative scheme combines an accurate polychromatic forward projection with a linearized backprojection. Both forward projection and backprojection have high degree of parallelism, and are suitable for acceleration on parallel systems. Numerical experiments with both simulated data and real data verifies the validity of the proposed method. The beam hardening artifacts are alleviated effectively. In addition, the proposed method has a good tolerance on the error of the estimated x-ray spectrum.
在本文中，我们提出了一种适用于多种材料情况的迭代束硬化校正方法。通过假设构成扫描对象的材料是已知的，并且它们在某些给定能量下可通过其线性衰减系数区分，束硬化校正问题被转化为一个非线性系统问题，然后通过迭代求解。重建图像是扫描对象在给定能量下的线性衰减系数分布。因此，理论上图像中不存在束硬化伪影。所提出的迭代方案将精确的多色前向投影与线性化反投影相结合。前向投影和反投影都具有高度的并行性，适用于在并行系统上进行加速。使用模拟数据和真实数据进行的数值实验验证了所提出方法的有效性。束硬化伪影得到了有效缓解。此外，所提出的方法对估计的X射线光谱误差具有良好的耐受性。
