| Harris and Ray test | A test for vitamin C in the urine; a microtitration test of the urine against a known amount of 0.05% aqueous solution of the dye 2,6-dichloroindophenol in 10% acetic acid (usually 0.05 ml of dye is used, roughly equivalent to 0.025 mg of ascorbic acid). Synonym: Harris test. (05 Mar 2000) |
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| X-ray | <investigation> A type of irradiation used for imaging purposes that uses energy beams of very short wavelengths (0.1 to 1000 angstroms) that can penetrate most substances except heavy metals. This is the commonest form of imaging technique used in clinical practice everywhere in the world with the image captured on photographic film. An AP film is when the beams pass from front-to-back (anteroposterior) and is used for mobile film, particularly on the ward or in casualty. This is the oposite to a PA film (posteroanterior) in which the rays pass through the body from back-to-front. Most films taken in the main radiology department are PA. (20 Jun 2000) |
| X-ray computed tomography | <radiology> Tomography using X-ray transmission and a computer to reconstruct the image. See: computed tomography. (20 Jun 2000) |
| X-ray crystallography | <investigation> A technique of determining the three-dimensional structure of a molecule by analysing the X-ray diffraction patterns of crystals made up of the molecule in question. (06 May 1997) |
| 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) |
| 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) |