Compensation of missing wedge effects with sequential statistical reconstruction in electron tomography.
Compensation of missing wedge effects with sequential statistical reconstruction in electron tomography.
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DOI：
10.1371/journal.pone.0108978
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Ruotsalainen U
中科院分区：
文献类型：
--
作者：
Paavolainen L;Acar E;Tuna U;Peltonen S;Moriya T;Soonsawad P;Marjomäki V;Cheng RH;Ruotsalainen U
生物样品的电子断层扫描（ET）被用来详细研究整个细胞和亚细胞复合物的组织和结构。然而，在电子显微镜下，生物样品不能在全倾斜角度范围内获得投影。由于这些信息的缺失，ET图像重建可以被认为是一个不适定问题。这将导致伪影，即重建图像中三维（3D）分辨率的损失。本研究的目的是通过统计重建方法实现各向同性分辨率，序列最大后检期望最大化（sMAP-EM），不使用关于标本的先验形态学知识。缺失的楔形效应对sMAP-EM用合成细胞幻象检查，以评估噪声的影响。一个多泡体的实验数据集用一些金粒子进行了评估。提出了一种基于椭球拟合的方法，实现了自动、客观、可靠的定量测量伸长和对比。该方法对随机分布在整个体积各个部分的含金粒子的子体积进行统计评估，从而给出了体积重建的鲁棒性信息。定量结果还与广泛使用的加权反投影和同时迭代重建技术方法进行了比较。结果表明，所提出的sMAP-EM方法显著抑制了缺失信息产生各向同性分辨率的影响。此外，该方法提高了对比度，增强了进一步自动化和半自动分析的适用性。与传统方法相比，sMAP-EM在ET重建方面的这些改进使亚细胞结构分析具有更高的三维分辨率和对比度。
Electron tomography (ET) of biological samples is used to study the organization and the structure of the whole cell and subcellular complexes in great detail. However, projections cannot be acquired over full tilt angle range with biological samples in electron microscopy. ET image reconstruction can be considered an ill-posed problem because of this missing information. This results in artifacts, seen as the loss of three-dimensional (3D) resolution in the reconstructed images. The goal of this study was to achieve isotropic resolution with a statistical reconstruction method, sequential maximum a posteriori expectation maximization (sMAP-EM), using no prior morphological knowledge about the specimen. The missing wedge effects on sMAP-EM were examined with a synthetic cell phantom to assess the effects of noise. An experimental dataset of a multivesicular body was evaluated with a number of gold particles. An ellipsoid fitting based method was developed to realize the quantitative measures elongation and contrast in an automated, objective, and reliable way. The method statistically evaluates the sub-volumes containing gold particles randomly located in various parts of the whole volume, thus giving information about the robustness of the volume reconstruction. The quantitative results were also compared with reconstructions made with widely-used weighted backprojection and simultaneous iterative reconstruction technique methods. The results showed that the proposed sMAP-EM method significantly suppresses the effects of the missing information producing isotropic resolution. Furthermore, this method improves the contrast ratio, enhancing the applicability of further automatic and semi-automatic analysis. These improvements in ET reconstruction by sMAP-EM enable analysis of subcellular structures with higher three-dimensional resolution and contrast than conventional methods.
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