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Pronunciation: fil'ter


  1. A porous substance through which a liquid or gas is passed to separate it from contained particulate matter or impurities to sterilize.
  2. To use or to subject to the action of a filter.
  3. In diagnostic or therapeutic radiology, a plate made of one or more metals such as aluminum and copper that, placed in the x- or gamma ray beam, permits passage of a greater proportion of higher-energy radiation and attenuation of lower-energy and less desirable radiation, raising the average energy or hardening the beam.
  4. A device used in spectrophotometric analysis to isolate a segment of the spectrum.
  5. A mathematical algorithm applied to imaging data for the purpose of enhancing image quality, usually by suppression or enhancement of high spatial frequencies.
  6. A passive electronic circuit or device that selectively permits the passage of certain electrical signals.
  7. A device placed in the inferior vena cava to prevent pulmonary embolism from low extremity clot. There are many variants.

Synonym(s): filtrum

[Mediev. L. filtro, pp. -atus, to strain through felt, fr. filtrum, felt]

Further information

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.