Huang Xinrui, Li Sha, Gao Song
School of basic medical sciences, Peking university, Department of Biophysics, Beijing, 100191, China.
School of foundational education, Peking university, Department of Medical Physics, Beijing, 100191, China.
Sci Rep. 2018 Feb 7;8(1):2582. doi: 10.1038/s41598-018-20945-6.
Cryo-electron tomography (cryo-ET) is one of the most advanced technologies for the in situ visualization of molecular machines by producing three-dimensional (3D) biological structures. However, cryo-ET imaging has two serious disadvantages-low dose and low image contrast-which result in high-resolution information being obscured by noise and image quality being degraded, and this causes errors in biological interpretation. The purpose of this research is to explore an optimal wavelet denoising technique to reduce noise in cryo-ET images. We perform tests using simulation data and design a filter using the optimum selected wavelet parameters (three-level decomposition, level-1 zeroed out, subband-dependent threshold, a soft-thresholding and spline-based discrete dyadic wavelet transform (DDWT)), which we call a modified wavelet shrinkage filter; this filter is suitable for noisy cryo-ET data. When testing using real cryo-ET experiment data, higher quality images and more accurate measures of a biological structure can be obtained with the modified wavelet shrinkage filter processing compared with conventional processing. Because the proposed method provides an inherent advantage when dealing with cryo-ET images, it can therefore extend the current state-of-the-art technology in assisting all aspects of cryo-ET studies: visualization, reconstruction, structural analysis, and interpretation.
冷冻电子断层扫描（cryo-ET）是通过生成三维（3D）生物结构对分子机器进行原位可视化的最先进技术之一。然而，冷冻电子断层扫描成像有两个严重缺点——低剂量和低图像对比度，这导致高分辨率信息被噪声掩盖且图像质量下降，进而在生物学解释中产生误差。本研究的目的是探索一种优化的小波去噪技术，以减少冷冻电子断层扫描图像中的噪声。我们使用模拟数据进行测试，并使用最佳选择的小波参数（三级分解、一级置零、子带相关阈值、软阈值处理以及基于样条的离散二进小波变换（DDWT））设计了一个滤波器，我们将其称为改进的小波收缩滤波器；该滤波器适用于有噪声的冷冻电子断层扫描数据。当使用真实的冷冻电子断层扫描实验数据进行测试时，与传统处理相比，使用改进的小波收缩滤波器处理可以获得更高质量的图像以及对生物结构更准确的测量。由于所提出的方法在处理冷冻电子断层扫描图像时具有内在优势，因此它可以扩展当前的先进技术，辅助冷冻电子断层扫描研究的各个方面：可视化、重建、结构分析和解释。
