低剂量CT投影图像噪声分析及去噪算法研究

Noise analysis and noise reduction for low-dose CT sinogram

提高低剂量CT图像的信噪比(SNR)是使低剂量CT获得有效临床应用的关键。本文对低剂量CT投影数据噪声研究发现,在投影图像的某些区域中可能会存在一些孤立的噪声点,滤除这些孤立点后的投影数据近似服从非平稳高斯噪声分布。由此,提出一种低剂量CT图像降噪算法,包括"孤立点"检测与滤波(IDE),基于最大后验概率(MAP)的高斯噪声滤波及FBP重建过程。计算机仿真以及真实数据实验表明,本文提出的去噪算法获得的重建CT图像,SNR及视觉效果均有明显的提高。

The improvement of the SNR of the low-dose CT image is a crucial issue for the low-dose CT application.As studied before,the noise in the calibrated and log-transformed projection data of low-mA（or low-dose） CT protocol follows approximately a non-stationary Gaussian distribution.In this study,we further demonstrate that some isolated noise points would not satisfy the above observation.Hence,we propose a noise reduction scheme for low-dose CT sinograms,which includes isolated datum detection and removal,MAP estimation and FBP reconstruction.The effectiveness of the proposed method is validated by both computer simulations and experimental studies.