| ray grass | <botany> A perennial European grass (Lolium perenne). Synonym: rye grass, and red darnel. See Darnel, and Grass. Italian ray, or rye, grass. See Darnel, and Grass. Origin: Etymol. Of ray is uncertain. Source: Websters Dictionary (01 Mar 1998) |
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| ray, light | <microscopy> The term applied to the lines perpendicular to the wavefronts of waves of light to indicate their direction of travel in an isotropic medium. Note the wave normal and the ray do not coincide in isotropic media. (05 Aug 1998) |
| ray therapeutics | An obsolete term for radiotherapy. (05 Mar 2000) |
| mass chest X-ray | X-ray screening of large groups of persons for diseases of the lung and heart by means of radiography of the chest. (12 Dec 1998) |
| reflected ray | A ray of light or other form of radiant energy which is thrown back from a nonpermeable or nonabsorbing surface; the ray which strikes the surface before reflection is the incident ray. (05 Mar 2000) |
| reflection X-ray microscopy | <technique> A method of producing enlarged images by means of X rays. In this method the radiation is totally reflected at glancing incidence from polished concave mirrors or from the curved surfaces of single crystals by Bragg reflection. The problem of aberration corrections still limits the resolution obtainable. (05 Aug 1998) |
| cathode ray | <physics> Electrons emitted from the surface of a cathode in a vacuum tube. (16 Mar 1998) |
| cathode ray tube | An evacuated tube containing a beam of electrons which can be deflected to various parts of a fluorescent screen; used in the cathode ray oscilloscope. (05 Mar 2000) |
| pa X-ray | An X-ray picture in which the beams pass from back-to-front (posteroanterior). As opposed to an ap (anteroposterior) film in which the rays pass through the body from front-to-back. (12 Dec 1998) |
| medullary ray | The centre of the renal lobule, which has the shape of a small, steep pyramid, consisting of straight tubular parts; these may be either ascending or descending limbs of the nephronic loop or collecting tubules. Synonym: pars radiata lobuli corticalis renis, Ferrein's pyramid, processus ferreini. (05 Mar 2000) |
| characteristic X-ray | <microscopy> An X-ray having a unique energy that is emitted by an atom in the sample during its de-energization after ionization of one of its electrons by an incident electron. (05 Aug 1998) |
| chemical ray | A light ray toward and beyond the violet end of the spectrum that acts upon a photographic plate and produces other chemical effects. Synonym: chemical ray. (05 Mar 2000) |
| chest X-ray | Commonly used to detect abnormalities in the lungs, but can also detect abnormalities in the heart, aorta, and the bones of the thoracic area. Metallic objects, such as jewelry are removed from the chest and neck areas for a chest X-ray to avoid interference with x-ray penetration and improve accuracy of the interpretation. (12 Dec 1998) |
| grenz ray | Very soft X-ray's, closely allied to the ultraviolet ray's in their wavelength (i.e., long) and in their biologic action upon tissues; they are produced by a specially built vacuum tube with a hot cathode operating from a transformer delivering not more than 8 kw. Origin: Ger. Grenze, borderline, boundary (05 Mar 2000) |
| roentgen 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) |