High resolution microscopic imaging with X-rays: technology and application to the biological sciences

Abstract

Ever since the invention of the visible light microscope, there has been a quest for ever sharper views of microscopic biological structure. Even before the advent of electron microscopy, it was recognized that the short wavelengths of x-rays could in principle allow high resolution imaging. But only in the last decade or so have technological advances made the original promise of biological x-ray microscopy realizable. These advances include the development of sources, optics, and detectors for the low energy x-rays ({open_quotes}soft{close_quotes} x-rays) best suited for imaging cellular structure. Modern x-ray microscopy (XM) is a versatile tool that offers several modes of operation and a variety of contrast mechanisms. Some of these may be viewed simply as high resolution extensions of existing visible light methods, while others are unique to x-rays, allowing new views of biological samples. XM fills a special niche between visible light microscopy (VLM) and electron microscopy (EM): it combines resolution beyond VLM, currently 30 to 50 nm, with penetration depth much greater than EM, up to several micrometers of water and organic material. Thus it can be used to image whole cells in an aqueous environment, in a near native state, potentially even living. In addition, itmore » is capable of quantitative, element specific mapping with high sensitivity.« less