| X-ray diffraction | <investigation> Basis of powerful technique for determining the three dimensional structure of molecules, including complex biological macromolecules such as proteins and nucleic acids, that form crystals or regular fibres. Low angle X-ray diffraction is also used to investigate higher levels of ordered structure, as found in muscle fibres. (18 Nov 1997) |
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| X-ray dosimetry | Measurement of an administered therapeutic or diagnostic dose and the penetrating power of X-rays. Synonym: X-ray dosimetry. (05 Mar 2000) |
| X-ray film | A film base coated with an emulsion designed for use with X-rays. (12 Dec 1998) |
| X-ray generator | The electronic device that controls production of X-rays in radiography; a key function is rectification of line voltage to produce a smooth direct current voltage to the X-ray tube. (05 Mar 2000) |
| X-ray intensifying screens | Screens which absorb the energy in the X-ray beam that has penetrated the patient and convert this energy into a light pattern which has as nearly as possible the same information as the original x-ray beam. The more light a screen produces for a given input of x-radiation, the less X-ray exposure and thus shorter exposure time are needed to expose the film. In most film-screen systems, the film is sandwiched between two screens in a cassette so that the emulsion on each side is exposed to the light from its contiguous screen. (12 Dec 1998) |
| X-ray, lateral | An X-ray picture taken from the side. (12 Dec 1998) |
| X-ray microanalysis | A technique of elemental analysis in the electron microscope based on spectral analysis of the scattered X-ray emission from the specimen induced by the electron beam. Using this technique it is possible to obtain quantitative data on, for example: the calcium concentration in different parts of a cell, but it is necessary to use ultra thin frozen sections. (18 Nov 1997) |
| X-ray microscope | <instrument> A microscope in which images are obtained by using X-rays as an energy source that are recorded on a very fine-grained film, or the image is enlarged by projection; if film is used, it may be examined with the light microscope at fairly high magnifications. (05 Mar 2000) |
| X-ray, pa | An X-ray picture in which the beams pass from back-to-front (posteroanterior). By contrast an ap (anteroposterior) film is one in which the rays pass through the body from front-to-back. (12 Dec 1998) |
| X-ray therapy | Radiation therapy using X-rays; sometimes used ironically to refer to excessive use of diagnostic radiation. (05 Mar 2000) |
| slow ray | <microscopy> The slower of the two rays created by a crystal or fibre and the one that travels the path of higher refractive index. (05 Aug 1998) |
| spectrometry, X-ray emission | Identification and measurement of concentration of elements based on the fact that X-rays emitted by an excited element have a wavelength characteristic of that element and an intensity related to its concentration. It includes fluorescence, or secondary-emission, X-ray spectrometry, in which the specimen is irradiated by X-rays. Primary-emission x-ray spectrometry, in which the specimen is bombarded by electrons, is a specific type of X-ray emission spectrometry known as electron probe microanalysis. (12 Dec 1998) |
| densitometry, X-ray | Measurement of the degree of darkening of X-ray film by means of a photocell which measures light transmission through the film. (12 Dec 1998) |
| incident ray | The ray that strikes the surface before reflection. (05 Mar 2000) |
| infrared ray | See: infrared. (05 Mar 2000) |