| NR | do not repeat [Lat. non repetatur]; nerve root; neural retina; neutral red; noise reduction; nonreac... |
|---|---|
| S/N | signal/noise [ratio] |
| SNR | selective nerve root [block]; signal-to-noise ratio; substantia nigra zona reticulata; supernumerary... |
| A/G ratio | Albumin/Globulin ratio; 알부민대 글로불린의 비율 |
| S/D ratio | Systolic / Diastolic ratio |
| phase-amplitude contrast | <microscopy> The separation and recombination of direct vs. Diffracted rays in a light microscope adjusted to Kohler illumination. at the lower focal plane of the condenser there is an annular diaphragm with an opaque central stop. Through this diaphragm rays are focused as a hollow cone onto the specimen. In the back focal plane of the objective there is a conjugate annular diaphragm (phase plate). If here the undiffracted rays are retarded (by a transparent film of proper thickness on the annulus of the phase plate), bright contrast results. If, instead, the phase-delay film is on the central spot, dark contrast results. With either a bright or a dark-contrast phase plate, the annulus is usually coated with a partially absorbing (very thin) film of silver (Zernike method) or carbon soot (Wilska method) to reduce the higher amplitude (intensity) of the undiffracted rays. (05 Aug 1998) |
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| phase contrast | <microscopy> An optical method devised by F. Zernike for converting the focused image of a phase object (one with differences in refractive index or optical path but not in absorbance), which ordinarily is not visible in focus, into an image with good contrast. (05 Aug 1998) |
| phase-contrast microscope | <instrument> A specially constructed microscope that has a special condenser and objective containing a phase-shifting ring whereby small differences in index of refraction are made visible as intensity or contrast differences in the image; particularly useful for examining structural details in transparent specimens such as living or unstained cells and tissues. (05 Mar 2000) |
| phase contrast microscopy | <investigation> A simple nonquantitative form of interference micoscopy of great utility in visualising live cells. Small differences in optical path length due to differences in refractive index and thickness of structures are visualised as differences in light intensity. (18 Nov 1997) |
| microscopy, phase-contrast | A form of interference microscopy in which variations of the refracting index in the object are converted into variations of intensity in the image. This is achieved by the action of a phase plate. (12 Dec 1998) |
| colour-contrast microscope | <instrument> A type of microscope in which the condenser stop is of one colour and the annulus is a complement of it so that unstained objects are observed in one colour on a field of the other. (05 Mar 2000) |
| contrast | A dye injected intravenously during X-ray studies, for example CT, to enhance the image of a tumour. In MR studies, the contrast is called gadolinium. The use of contrast may rarely result in some adverse effects: it also increases the cost (but also accuracy in many cases) of the scan. (16 Dec 1997) |
| contrast agent | A substance that is introduced into or around a structure and, because of the difference in absorption of X-rays by the contrast medium and the surrounding tissues, allows radiographic visualisation of the structure. (18 Nov 1997) |
| contrast bath | A bath in which a part is immersed in hot water for a period of a few minutes and then in cold, the hot and cold periods alternated regularly at intervals, usually half-hours; used to increase the blood flow to the part. (05 Mar 2000) |
| contrast echocardiography | The injection of contrast media of high echo reflectants (e.g., bubbles) to outline a chamber or delineate a shunt within the heart. (05 Mar 2000) |
| contrast enema | Enema using barium or another contrast medium. (05 Mar 2000) |
| contrast enhancement | The intravenous administration of water-soluble iodinated contrast material, which increases the CT number of the vascular pool, as well as some lesions (particularly in the brain), due to abnormal leakage into the interstitium; the property of showing increased radiopacity from concentration of contrast medium. (05 Mar 2000) |
| contrast material | A substance that is introduced into or around a structure and, because of the difference in absorption of X-rays by the contrast medium and the surrounding tissues, allows radiographic visualisation of the structure. (18 Nov 1997) |
| contrast media | <radiology> Side-effects from high osmolality / viscosity (fluid shifts from different compartments), vasodilatation, heat, pain, osmotic diuresis, haemodynamic changes, pharmacokinetics, distribute volume into extracellular space, clearance by glomerular filtration and renal excretion, physiologic reaction, increased plasma osmolality causes fluid shift from RBCs and pulmonary tissue leading to increased plasma volume, then osmolar gradient reverses with passage of contrast bolus to pulmonary capillary endothelium leaks protein into pulmonary interstitium leading to increased pulmonary oedema, transient cardiovascular changes (magnitude increased with tonicity of medium), increased PAP, increased CO with decreased peripheral/pulmonary vascular resistance, decreased systemic arterial pressure (variable), may activate gen receptors causing side effects (12 Dec 1998) |
| contrast medium | A substance that is introduced into or around a structure and, because of the difference in absorption of X-rays by the contrast medium and the surrounding tissues, allows radiographic visualisation of the structure. (18 Nov 1997) |