X-Ray Contact Imaging: the Technique

Abstract

Until recently, instruments used to image small biological objects directly have involved the use of light microscopy or electron microscopy. Presently, the use of x-rays has emerged as another probe to investigate details in biological specimens. X-rays can be used either by using an x-ray “lens”, which will be discussed by others at this symposium or by a direct contact “print” of the object on a special emulsion. This latter method is what will be discussed in this paper.The object to be ‘photographed’ is prepared on a substrate and then placed in contact with a resist such as poly- methyl-methacrylate (PMMA). This polymer has the property that when it is exposed to x-rays and then placed in a solution of methyl isobutyl ketone (MIBK) it will 'develop’ depending on the number of x-ray photons absorbed in the PMMA. This three dimensional relief structure is actually a photon density map of the specimen.