中文摘要：

针对多金属伪影的校正问题,本文通过仿真实验分析了多金属伪影的成因,并提出了一种基于投影校正的多金属伪影校正方法.该方法首先直接从投影域分割出金属区域,然后建立对金属区域投影值的校正模型,最后通过调整模型参数达到校正目的.模型以重建图像的灰度熵为目标函数,采用单纯形法迭代求解使熵最小时的校正参数.仿真和实际数据的实验结果表明,本文算法对多金属伪影的校正起到了良好的效果,且校正后的图像质量优于插值校正法.

英文摘要：

High-attenuation objects like metals will result in metal artifacts in computed tomography images. Compared with single metallic object, artifacts due to multiple and large-scaled metallic objects is more complicated in representation and have much worse efiects on reconstructed image. State-of-the-art metal artifacts reduction for multiple metal objects based on interpolation method cannot solve the beam hardening inside the metals, and can easily make mistakes in segmentation and interpolation. Aiming at reduction of multiple metallic objects, this paper simulates the production of the artifacts and proposes a metal artifacts reduction method based on projections correction. In this method, metal regions are firstly segmented directly from projection domain, and then a correction model is established for projections in metal regions. Finally, correction is made by adjusting parameters of the model. The optimal solution of the parameters is achieved by NM-simplex method that makes the gray entropy of the reconstructed image minimum. The simulation results and obtained data show that the present method significantly improves metal artifact due to multiple metallic objects and provides a better image quality than that obtained using interpolation.