| myocardial infarct imaging | <radiology> Tc-99m pyrophosphate (PYP) 20 mCi, peak abnormality 2-3 days, often falsely negative before 2 days, abnormal for 7-10 days, mechanism: calcium influx into ischemic cells, PYP incorporated into crystalline structure, analogous to hydroxyapatite see: nuclear cardiology (12 Dec 1998) |
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| haemorrhagic infarct | An infarct red in colour from infiltration of blood from collateral vessels into the necrotic area. Synonym: haemorrhagic gangrene, red infarct. (05 Mar 2000) |
| scanning | The act of imaging by traversing with an active or passive sensing device, often identified by the technology or device employed. (05 Mar 2000) |
| scanning electron microscope | <instrument> An electron microscope in which the image is formed by a beam synchronised with an electron probe scanning the object. The intensity of the image forming beam is proportional to the scattering or secondary emission of the specimen where the probe strikes it (05 Aug 1998) |
| scanning electron microscopy | <procedure> Technique of electron microscopy in which the specimen is coated with heavy metal and then scanned by an electron beam. The image is built up on a monitor screen (in the same way as the raster builds a conventional television image). The resolution is not so great as with transmission electron microscopy, but preparation is easier (often by fixation followed by critical point drying), the depth of focus is relatively enormous, the surface of a specimen can be seen (though not the interior unless the specimen is cracked open) and the image is aesthetically pleasing. (18 Nov 1997) |
| scanning equalization radiography | An electronically enhanced method of radiography in which a small X-ray beam is scanned over the patient while its attenuation is measured, providing feedback to modulate beam intensity in order to equalise average X-ray film exposure. (05 Mar 2000) |
| Scanning Probe Microscopy | <technique> Initially called Atomic Force Microscopy, this technique is now more typically termed Scanning Force Microscopy or Scanning Probe Microscopy. This instrument is essentially an extremely high resolution profilometre. A sharp tip, typically fabricated from silicon nitride, is scanned across the surface of a sample at a constant force by three piezoelectric ceramics. The piezoelectric ceramics are computer controlled via a feedback loop which monitors the position of the tip by means of an optical lever. (A laser is focused on the top of the tip support and the beam reflected into a position sensitive detector). The changes in height of the tip are used to form an image as the tip is scanned across the sample. Acronym: SPM (26 Mar 1998) |
| scanning speech | Measured or metered, often slow speech. (05 Mar 2000) |
| scanning transmission electron microscopy | <procedure> Method of electron microscopy in which image formation depends upon analysis of the pattern of energies of electrons that pass through the specimen. Has comparable resolving power to conventional transmission EM. (18 Nov 1997) |
| scanning tunnelling microscopy | <procedure> A form of ultra high resolution microscopy of a surface in which a very small current is passed through a surface and is detected by a microprobe of atomic dimnensions at its tip that scans the surface by use of a piezodrive. In the simplest form the current transferred to the probe is recorded as an indication of the contours of molecules on the surface above the local plane. In more complex forms feedback is used to hold the probe at a constant difference and the signal in the feedback loop indicates the contours of the molecule. Capable of resolving single atoms and known to work for nonconducting molecules as well as conducting ones. (18 Nov 1997) |
| septic infarct | An area of necrosis resulting from vascular obstruction due to emboli comprised of clumps of bacteria or infected material. (05 Mar 2000) |
| dementia, multi-infarct | Organic mental disorder caused by repetitive multiple cerebral infarcts which act cumulatively to produce dementia. Vascular disease is always presumed to be present. (12 Dec 1998) |
| infarct | An area of tissue death due to a local lack of oxygen. (12 Dec 1998) |
| thrombotic infarct | An infarct caused by a thrombus. (05 Mar 2000) |
| embolic infarct | An infarct caused by an embolus. (05 Mar 2000) |