中文摘要：

本文根据低剂量CT投影数据的噪声特性,提出了一种基于小波变换的低剂量CT投影数据三维块匹配（BM3D）滤波方法。新方法首先对经过Anscombe变换的低剂量CT投影数据进行小波分解,然后分别对分解后尺度系数和小波系数进行BM3D滤波,接着对滤波后的系数进行逆小波变换和Anscombe逆变换,最后对处理后的投影数据采用经典的滤波反投影（FBP）算法完成图像重建。实验表明,本文方法在噪声抑制和图像细节保持等方面均有上佳表现。

英文摘要：

According to the property of the low-dose CT projection noise,this paper propose a wavelet-transform based low-dose CT projection BM3D Filtering（Block-Matching and 3D filtering）technique.For the proposed method,first,low-dose projection data is decomposed by Haar-wavelet transform after Anscombe transform.And then the efficient BM3D algorithm is performed separately in the scale coefficient and the wavelet coefficients.Next,the filtered coefficients are transformed orderly by inverse Anscombe transform and inverse Haar-wavelet transform.Finally,the reconstruction image is achieved by the classical filtered back projection（FBP）method.Simulated and clinical data experimental results demonstrate that the proposed method can do well in noise suppression and detail preservation of the reconstructed image.