Abstract: In order to improve the quality of low-dose CT image，a novel approach is proposed based on low-dose CT projection restoration.In this paper，first，projection data is transformed to a Gaussian distribution from a Poisson distribution using nonlinear Anscombe transform.Then，the transformed data is filtered by an efficient BM3D algorithm.Last，the reconstruction result is achieved by inverse Anscombe transform and Filtered Back Projection（FBP） method.Because the variance of the Gaussian noise is known，the proposed scheme can be implemented without any manual parameters.Simulated and clinical low-dose CT data experiment results demonstrate that a high quality CT image can be reconstructed with effectively suppressed noise and streak artifacts.

Key words: low-dose CT, Anscombe transform, projection restoration, Block-Matching and 3D（BM3D） filtering

摘要： 针对低剂量CT图像质量退化问题，提出了一种基于投影域数据恢复的低剂量CT优质重建方法。新方法首先通过非线性Anscombe变换将满足Poisson分布的投影域数据转化Gaussian型分布，然后利用针对Anscombe变换的Gaussian型数据进行自适应Block-Matching and 3D filtering（BM3D）滤波，最后通过对Anscombe逆变换数据执行传统的滤波反投影（Filtered Back Projection，FBP）CT重建。由于Anscombe变换数据的方差已知，且所用BM3D滤波无需人工设置滤波参数，使得方法可实现自适应低剂量CT图像重建。仿真和临床低剂量CT数据的实验表明，方法具有良好的重建鲁棒性，其重建图像的噪声和伪影可同时得到有效抑制。

关键词: 低剂量CT, Anscombe变换, 投影域数据恢复, 基于块匹配的混合（BM3D）滤波