| acoustic enhancement | A manifestation of increased acoustic signal amplitude returning from regions beyond an object which causes little or no attenuation of the sound beam. Compare: acoustic shadow. (05 Mar 2000) |
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| antibody-dependent enhancement | Enhancement of viral infectivity caused by non-neutralizing antibodies. There are at least two mechanisms known to account for this: mediation by fc receptors (receptors, fc) or by complement receptors (receptors, complement). Either the virus is complexed with antiviral IgG and binds to fc receptors, or virus is coated with antiviral IgM and binds to complement receptors. (12 Dec 1998) |
| radiographic image enhancement | Improvement in the quality of an X-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed. (12 Dec 1998) |
| graft enhancement, immunologic | The induction of prolonged survival and growth of allografts of either tumours or normal tissues which would ordinarily be rejected. It may be induced passively by introducing graft-specific antibodies from previously immunised donors, which bind to the graft's surface antigens, masking them from recognition by T-cells; or actively by prior immunization of the recipient with graft antigens which evoke specific antibodies and form antigen-antibody complexes which bind to the antigen receptor sites of the T-cells and block their cytotoxic activity. (12 Dec 1998) |
| ring enhancement | In computed tomography, when a bright circle appears on an image made after injection of contrast medium, characteristic of localization of the contrast in the wall of an abscess. (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) |
| image enhancement | Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural microscopy, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level. (12 Dec 1998) |
| immunological enhancement | In immunology, the potentiating effect of specific antibody in establishing and in delaying rejection of a tumour allograft; aside from antibody, non-specific substances may also act to enhance immune response. Synonym: immunological enhancement. (05 Mar 2000) |
| edge enhancement | Using analogue or digital image processing to increase the contrast of each interface; equivalent to using a high-pass filter. (05 Mar 2000) |
| enhancement | Altering an object, substance or site for the improvement of a specific value. (09 Oct 1997) |
| enhancement effect | Property of higher plant photosynthesis, discovered by Robert Emerson. The quantum yield of red light (less than 680nm) and far red light (700nm), when shone simultaneously on a plant, is greater than the sum of the yields of the light of the two wavelengths separately. This effect provides evidence for the cooperative interaction of two photosystems in photosynthesis. (18 Nov 1997) |
| paradoxical | Occurring at variance with the normal rule. (18 Nov 1997) |
| paradoxical contraction | A tonic contraction of the anterior tibial muscles when a sudden passive dorsal flexion of the foot is made. (05 Mar 2000) |
| paradoxical diaphragm phenomenon | In pyopneumothorax, hydropneumothorax, and some cases of injury, the diaphragm on the affected side rises during inspiration and falls during expiration. (05 Mar 2000) |
| paradoxical embolism | Passage of a clot (thrombus) from a vein to an artery. When clots in veins break off (embolise) , they travel first to the right side of the heart and, normally, then to the lungs where they lodge. The lungs act as a filter to prevent the clots from entering the arterial circulation. However, when there is a hole in the wall between the two upper chambers of the heart (an atrial septal defect), a clot can cross from the right to the left side of the heart, then pass into the arteries as a paradoxical embolism. Once in the arterial circulation, a clot can travel to the brain, block a vessel there, and cause a stroke (cerebrovascular accident). Because of the risk of stroke from paradoxical embolism, it is usually recommended that even small atrial septal defects be repaired. Also called crossed embolism. (12 Dec 1998) |