[L. filtrum, felt (for straining)]
1. To pass a liquid through any porous substance that prevents particles larger than a certain size from passing through.
2. A device for filtering liquids, light rays, or radiations.
SEE: absorption; SEE: osmosis
3. Material, such as aluminum or molybdenum, inserted between the radiation source and the patient to absorb low-level radiation that would increase the dose.
SEE: Berkefeld filter
In radiography, a filter that shields less dense areas to produce a more nearly uniform radiographic image.
ABBR: HEPA filter An air filter capable of removing 99.7% of particles greater than 0.3 μm in diameter.
A filter that permits passage of only infrared waves of a certain wavelength.
A filter that removes high-frequency waves from a sample, allowing only those below a specified frequency to pass.
A filter made from biologically inert cellulose esters, polyethylene, or other porous materials.
Trademark name of a filter usually composed of cellulose acetate with controlled pore size that separates particles above specific sizes from the solutions that flow through.
A device that passes only a portion of the visible light spectrum. Absorption filters absorb the unwanted wavelengths. Interference filters employ the wave effects of constructive and destructive superposition to pass or inhibit appropriate wavelengths.
An unglazed porcelain filter capable of retaining bacteria and some viruses. Either pressure or suction is required to force or draw the liquid through the filter.
A filter placed in a blood vessel to prevent emboli from passing that point. It has been used in the vena cava to prevent emboli reaching the lungs via the chambers of the right heart and pulmonary arteries.
Complications of filter use include perforation of the vein, migration of the filter, or fragmentation and embolization of its parts.
A wire apparatus inserted through a catheter into the inferior vena cava to prevent pulmonary emboli.
A filter used in radiography and radiation therapy to vary the intensity of the x-ray beam. This compensates for differences in the thicknesses of the parts being exposed to radiation.
An ultraviolet light source used to diagnose some fungal and bacterial skin diseases.
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