Vulovic M, Rieger B, van Vliet L J, Koster A J, Ravelli R B G
Section Electron Microscopy, Department of Molecular Cell Biology, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands.
Acta Crystallogr D Biol Crystallogr. 2010 Jan;66(Pt 1):97-109. doi: 10.1107/S0907444909031205. Epub 2009 Dec 21.
Charge-coupled devices (CCD) are nowadays commonly utilized in transmission electron microscopy (TEM) for applications in life sciences. Direct access to digitized images has revolutionized the use of electron microscopy, sparking developments such as automated collection of tomographic data, focal series, random conical tilt pairs and ultralarge single-particle data sets. Nevertheless, for ultrahigh-resolution work photographic plates are often still preferred. In the ideal case, the quality of the recorded image of a vitrified biological sample would solely be determined by the counting statistics of the limited electron dose the sample can withstand before beam-induced alterations dominate. Unfortunately, the image is degraded by the non-ideal point-spread function of the detector, as a result of a scintillator coupled by fibre optics to a CCD, and the addition of several inherent noise components. Different detector manufacturers provide different types of figures of merit when advertising the quality of their detector. It is hard for most laboratories to verify whether all of the anticipated specifications are met. In this report, a set of algorithms is presented to characterize on-axis slow-scan large-area CCD-based TEM detectors. These tools have been added to a publicly available image-processing toolbox for MATLAB. Three in-house CCD cameras were carefully characterized, yielding, among others, statistics for hot and bad pixels, the modulation transfer function, the conversion factor, the effective gain and the detective quantum efficiency. These statistics will aid data-collection strategy programs and provide prior information for quantitative imaging. The relative performance of the characterized detectors is discussed and a comparison is made with similar detectors that are used in the field of X-ray crystallography.
电荷耦合器件（CCD）如今常用于生命科学领域的透射电子显微镜（TEM）中。直接获取数字化图像彻底改变了电子显微镜的使用方式，引发了断层扫描数据自动采集、聚焦系列、随机锥形倾斜对以及超大型单颗粒数据集等方面的发展。然而，对于超高分辨率工作，照相底片通常仍然更受青睐。在理想情况下，玻璃化生物样品记录图像的质量仅由样品在电子束诱导变化占主导之前所能承受的有限电子剂量的计数统计决定。不幸的是，由于通过光纤耦合到CCD的闪烁体以及多种固有噪声成分的加入，探测器的非理想点扩散函数会使图像退化。不同的探测器制造商在宣传其探测器质量时提供不同类型的品质因数。大多数实验室很难验证是否满足所有预期规格。在本报告中，提出了一组算法来表征基于轴上慢扫描大面积CCD的TEM探测器。这些工具已被添加到一个公开可用的MATLAB图像处理工具箱中。对三台内部CCD相机进行了仔细表征，除其他外，得出了热点像素和坏点像素的统计数据、调制传递函数、转换因子、有效增益和探测量子效率。这些统计数据将有助于数据采集策略程序，并为定量成像提供先验信息。讨论了所表征探测器的相对性能，并与X射线晶体学领域使用的类似探测器进行了比较。
