COMPARISON OF HVEM & IVEM FOR BIOLOGICAL APPLICATIONS

（NIH NCRR/ P41-RR 01219支持）本项目的目标是 确定高压EM相对于 中压EM重建高分辨率 厚生物标本的超微结构。 各种参数 包括，例如，标本类型、标本制备方法和EM 成像条件以及随后的数据呈现（即， 后处理和重建方法）。 两 HVEM和IVEM的可变电压能力 在这个项目中使用。 HVEM的设置使用柯达SO-163 胶片，在我们的其他电子显微镜中使用的标准胶片 设施。 这对于这些测试是必要的，因为图像通常必须 在低剂量下被记录下来，而杜邦的“低剂量”电影，我们已经 用于这一点是不适合光学衍射，其中一个 用于评估图像质量的工具。 对于HVEM和IVEM， SO-163的标准推处理方法被用于 低剂量工作，正常发育进行日常工作。 初步 在1000 kV和1000 kV下成像的相同1 m厚样品的比较研究 HVEM中的400 kV显示出可检测到的，但不显著的差异， 图像质量仅在60（倾斜。 然而，暴露的差异 在1000 kV时，0度和60度之间的电压为3倍， 400千伏。 400 kV下较长的曝光时间使记录无漂移 图像有问题

(Supported by NIH NCRR/ P41-RR 01219) The goal of this project is to determine the advantages of high-voltage EM relative to intermediate-voltage EM for reconstructing the high resolution ultrastructure of thick biological specimens. Various parameters including, e.g., specimen type, specimen preparation method, and EM imaging conditions, as well as subsequent data presentation (i.e., post-processing and reconstruction methods) are being explored. Both the variable-voltage capability of our HVEM, as well as our IVEM are being used in this project. The HVEM was set up to use Kodak SO-163 film, the standard film used in the other electron microscopes in our facility. This is necessary for these tests because images often must be recorded at low dose, and the Dupont "lo-dose" film we had been using for this is not suitable for optical diffraction, one of the tools to be used in assessing image quality. For both HVEM and IVEM, the standard push-processing method for SO-163 is being used for low-dose work, and normal development for routine work. Preliminary comparison studies of the same 1(m thick specimen imaged at 1000kV and 400kV in the HVEM showed detectable, but insignificant, differences in image quality only at 60( tilt. However, the difference in exposure between zero and sixty degrees was 3 times at 1000kV and 25 times at 400kV. The longer exposure time at 400kV made recording drift-free images problematical.