Compositional biological mapping with x-rays in the electron microscope

Abstract

New ideas in microprobe analysis over the last decade have refuted the notion that electron probe xray imaging is limited to multispectral data as qualitative maps. Electron microscopy is still the most widely used technique for high resolution imaging of biological materials. The acquisition and processing of digital quantitative elemental images of one to several cells in an electron microscope is now accomplished with advanced, commonly available microcomputers. A system developed in our laboratories uses a graphics-based microcomputer to acquire spectrally filtered xray data that is fitted to standards, to display the data and images on-line and in real time, and to correct the multispectral image with regard to specimen drift. Statistics in the data acquisition is the limiting factor in both the image resolution and the ability to automatically recognize regions which need longer acquisition times.Except in routine clinical or diagnostic situations, specimen preparation requires the tissues or cells to be rapidly frozen in a viable state in order to preserve their inherent elemental and anatomical integrity.