1. A sheet of any substance used to shield an object from any influence, such as heat, light, x-rays, etc. 2. A sheet upon which an image is projected. 3. Formerly, to make a fluoroscopic examination. 4. In psychoanalysis, concealment, as one image or memory concealing another. SEE ALSO: s. memory. 5. To examine, evaluate; to process a group to select or separate certain individuals from it. 6. A thin layer of crystals that converts x-rays to light photons to expose film; used in a cassette to produce radiographic images on film. [Fr. écran]
- Bjerrum s. SYN: tangent s..
- s.-film contact the closeness and uniformity with which the x-ray film in a cassette lies against the s. (6). Image resolution is dependent on this property.
- fluorescent s. a s. coated with fluorescent crystals such as the calcium tungstate used in the fluoroscope.
- intensifying s. a s. (6) used in radiography.
- multiple marker s. use of two or more markers in the maternal serum to determine the relative risk of an abnormal fetus. SEE ALSO: triple s..
- rare-earth s. an intensifying s. (6) made of a rare-earth oxide phosphor, more efficient than calcium tungstate, especially at the higher kilovoltages used in modern radiography.
- tangent s. a flat, usually black surface used to measure the central 30 degrees of the field of vision. SYN: Bjerrum s..
- triple s. test of maternal serum α-fetoprotein, chorionic gonadotropin, and unconjugated estrogen for indications of increased risk of fetal abnormality, especially trisomy 21.
- vestibular s. a s. made of acrylic resin that covers the labial or buccal surfaces of one or both dental arches; used to treat oral habits and to stimulate tooth movement by using perioral muscle force.
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screen 'skrēn vt to test or examine for the presence of something (as a disease) <\screen patients for prostate cancer> <a test to \screen donor blood for HIV and hepatitis C (Penni Crabtree)>
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(skrēn) 1. a structure resembling a curtain or partition, used as a protection or shield, e.g., against excessive radiation exposure; see also shield. 2. a large flat surface upon which light rays are projected. 3. protective (def. 2). 4. to examine by fluoroscopy (Great Britain). 5. to separate well individuals in a population from those who have an undiagnosed disease, defect, or other pathologic condition or who are at high risk, by means of tests, examinations, or other procedures. See also screening.Medical dictionary. 2011.