| static tremor | Tremor present when the limbs or trunk are kept in certain positions and when they are moved actively, usually due to near-synchronous rhythmic bursts in opposing muscle groups. Synonym: static tremor. (05 Mar 2000) |
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| calorimetry, differential scanning | Differential thermal analysis in which the sample compartment of the apparatus is a differential calorimeter, allowing an exact measure of the heat of transition independent of the specific heat, thermal conductivity, and other variables of the sample. (12 Dec 1998) |
| magnetic resonance scanning | A special imaging technique used to image internal stuctures of the body, particularly the soft tissues. An MRI image is often superior to a normal X-ray image. It uses the influence of a large magnet to polarize hydrogen atoms in the tissues and then monitors the summation of the spinning energies within living cells. Images are very clear and are particularly good for soft tissue, brain and spinal cord, joints and abdomen. These scans may be used for detecting some cancers or for following their progress. Acronym: MRI (11 Nov 1997) |
| ventilation perfusion scanning | <investigation, radiology> A nuclear medicine test that involves the inhalation of a radioactive gas and the injection of a radioactive compound into the bloodstream. A special camera measures the radioactive compound and generates a image of the lungs. Comparisons are made between the images generated. Pulmonary embolism can be diagnosed using this procedure. (12 Jan 1998) |
| vq scanning | A nuclear medicine test that involves the inhalation of a radioactive gas and the injection of a radioactive compound into the bloodstream. A special camera measures the radioactive compound and generates a image of the lungs. Comparisons are made between the images generated. Pulmonary embolism can be diagnosed using this procedure. (27 Sep 1997) |
| microscopy, electron, scanning | Microscopy in which the object is examined directly by an electron beam scanning the specimen point-by-point, giving the surface image a three-dimensional quality. (12 Dec 1998) |
| microscopy, electron, scanning transmission | A type of electron microscopy which scans with an extremely narrow beam that is transmitted through the sample. The detection apparatus produces an image whose brightness depends on the atomic number of the sample. It should not be confused with microscopy, electron scanning nor with microscopy, electron, transmission (see microscopy, electron). (12 Dec 1998) |
| microscopy, scanning tunneling | Electron microscopy in which a very sharp conducting needle is swept just a few angstroms above the surface of a sample. The tiny tunneling current that flows between the sample and the needle tip is measured and from this are produced three-dimensional topographs, with a lateral resolution often as good as 1-2 angstroms and a vertical resolution of less than 1 angstrom. Due to their composition, biological samples are usually coated with a conductive layer, e.g., by depositing a thin metal or carbon film on top of the sample, to enhance their conductivity. (12 Dec 1998) |
| 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) |