投影数据恢复导引的非局部平均低剂量CT优质重建

摘要

针对低剂量CT成像质量退化问题,将CT投影数据恢复与图像数据恢复巧妙地融合,提出一种投影数据恢复导引的非局部平均(NL-means)低剂量CT重建方法.首先通过非线性Anscombe变换将满足Poisson分布的投影数据转化为Gaussian分布,以便于投影数据噪声的滤除;然后对滤波后的投影数据执行Anscombe逆变换和滤波反投影(FBP)CT图像重建;最后将投影数据滤波后的FBP图像作为先验构建非局部权值矩阵,并将该权值矩阵用于低剂量CT图像的非局部平均成像.仿真和临床实验结果表明.该方法在噪声消除和伪影抑制两方面均有上佳表现.%To improve the quality of low-dose computed tomography (CT) image, a novel projection data recovery induced non-local means for low-dose CT reconstruction is proposed. The presented method can take the advantages of data recovery methods in two domains (projection domain and image domain). Specially, the projection data is first transformed from Poisson distribution to Gaussian distribution using the nonlinear Anscombe transform in order to easily filter the noise of projection data. Second, after Anscombe transformed data is filtered, Anscombe inverse transform is performed, and the reconstructed image is achieved using the classical filtered back projection (FBP) method from filtered projection data. Last, non-local means (NL-means) weights of FBP image are computed from the restored projection data to induce the NL-means filtering of directly reconstructed FBP image from the un-restored projection data. Simulated and clinical experimental results demonstrate that the proposed method performs very well in lowering the noise and preserving the image edge.