Radermacher M
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201.
J Electron Microsc Tech. 1988 Aug;9(4):359-94. doi: 10.1002/jemt.1060090405.
To overcome the radiation damage-induced limitations to the resolution of three-dimensional reconstructions from electron microscopic tilt series, novel reconstruction schemes have been developed that require only a single exposure of the specimen. The tilt series collected with these methods have random projection directions. First, three-dimensional reconstruction techniques are described that are applicable to data obtained from tilt series with regular tilt geometry, followed by the extensions of these techniques to permit analysis of projection series with randomly spaced tilts. The main emphasis is placed on the weighted back-projection methods, which have recently been extended so as to be applicable to random tilt series. Besides a description of the algorithms, the complete procedure for a three-dimensional reconstruction from a single-exposure, random conical tilt series is explained, including the determination of the azimuthal angles, the alignment scheme for conical tilt series, the dependence of the achievable resolution on the number of projections for regular conical and single-axis geometries, and the method to calculate the actual resolution of two-dimensional image averages and of three-dimensional reconstructions using the phase residual and Fourier ring correlation criteria. Examples are given of biological specimens to which these three-dimensional reconstruction methods have been applied.
为了克服辐射损伤对电子显微镜倾斜系列三维重建分辨率造成的限制，已开发出仅需对标本进行单次曝光的新型重建方案。用这些方法收集的倾斜系列具有随机投影方向。首先，描述适用于从具有规则倾斜几何形状的倾斜系列获得的数据的三维重建技术，然后将这些技术扩展以允许分析具有随机间隔倾斜的投影系列。重点主要放在加权反投影方法上，该方法最近已得到扩展，以便适用于随机倾斜系列。除了算法描述外，还解释了从单次曝光、随机锥形倾斜系列进行三维重建的完整过程，包括方位角的确定、锥形倾斜系列的对齐方案、对于规则锥形和单轴几何形状可实现分辨率对投影数量的依赖性，以及使用相位残余和傅里叶环相关标准计算二维图像平均值和三维重建实际分辨率的方法。给出了应用这些三维重建方法的生物标本示例。
