| simon nitinol ivc filter | <radiology> Introduced 1990; Nitinol Medical Technologies, Woburn, MA. BARD, thermal memory alloy:titanium and nickel;, straightened form at cool temperatures (4-10C), reforms into predetermined filter shape at body temperatures efficacy, recurrent PE: 0 - 4.8%, IVC thrombosis: 7 - 11% (by clinical symptoms), access site thrombosis: 2 - 10% advantages, narrow introducer sheath (9 Fr), largest choice of access: brachial or left CFV approach without difficulty, only mild MRI artifacts disadvantages, IVC thrombosis: symptomatic occlusion rates higher than reported wtih Greenfield or bird's nest filters, caval penetration: 1 - 33%, caudal drop: exact filter location difficult to predict (12 Dec 1998) |
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| spatial filter | <radiobiology> Device consisting of a lens pair and a pinhole aperture stop. Intensity fluctuations over the spatial extent of a laser beam are removed by passing the focused beam through the aperture stop. The pinhole must be placed in a vacuum to prevent air breakdown by the focused beam. These filters are used to counter the effects caused by self-focusing. (09 Oct 1997) |
| neutral-density filter | <equipment> A light-absorbing filter whose absorption spectrum is moderately flat. Depending on the type, the absorption curve is flat primarily in the visible spectral range, or may extend to varying degrees beyond the visible range. For video microscopy, this is an important point since the absorbance may or may not extend into the near-infrared region where the sensitivity of many video image pickup devices is very high. (05 Aug 1998) |
| nitinol filter | A vena cava filter made with a metal that springs into shape when warmed to body heat by the blood after catheter insertion. (05 Mar 2000) |
| Nucleopore filter | Filter of defined pore size made by etching a polycarbonate filter that has been bombarded by neutrons, the extent of etching determining the pore size. Very thin, with neat circular holes going right through the membrane, not a complex meshwork like micropore filters. (18 Nov 1997) |
| DNA filter assay | <molecular biology> A lab technique used to identify the complementary base sequences of DNA. It involves immobilising the DNA on a filter and putting it in a solution that contains radioactively-labelled probe DNA or RNA molecules. (09 Oct 1997) |
| inferior vena cava filter | <radiology> Indications: contraindication to anticoagulation, failure of anticoagulation, complication of anticoagulation: haemorrhage or thrombocytopenia, large free-floating IVC/iliac vein thrombus expanded indications: cor pulmonale and DVT/PE, patients with high risk of complications to anticoagulation, metastatic disease, syncope in elderly, prophylactic placement in high-risk trauma patients, spinal cord injury, severe head injury, complex pelvic fractures, multiple long bone fractures, prophylactic placement before hip/knee replacement in patients with prior DVT prophylactic filters remain controversial see also: types of IVC filters (12 Dec 1998) |
| titanium greenfield ivc filter | <radiology> Advantages: low profile: 14.3 Fr introducer sheath, percutaneous placement, lack of ferromagnetic properties, low recurrent PE rate (3-5%), low IVC thrombosis rate (1-9%), successful placement (97%) disadvantages: maximum caval diameter = 28mm, tilting/leg assymetry, difficult placement from left femoral approach see also: indications (12 Dec 1998) |
| filter | 1. A porous substance through which a liquid or gas is passed in order to separate it from contained particulate matter or impurities. Synonym: filtrum. 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 and less desirable energy 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 image data for the purpose of enhancing image quality, usually by suppression of high spatial frequency noise. Origin: Mediev. L. Filtro, pp. -atus, to strain through felt, fr. Filtrum, felt (05 Mar 2000) |
| filter fabric | A fabric used to collect sediment from water flowing through a creek or through a gully. (09 Oct 1997) |
| filter sterilisation | A lab technique to sterilise a solution by passing it through a filter fine enough to catch bacteria-sized microorganisms. (09 Oct 1997) |
| low-pass filter | A device or material with the opposite effect from a high-pass filter; most tissues act as low-pass filters of ultrasound signals. (05 Mar 2000) |