| 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) |
| contrast sensitivity | The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease. (12 Dec 1998) |
| contrast stain | <technique> A dye used to colour one portion of a tissue or cell which remained unaffected when the other part was stained by a dye of different colour. Synonym: differential stain. (05 Mar 2000) |
| contrast transfer function | <microscopy> A mathematical function that expresses the ability of an optical or electronic device to transfer signals faithfully as a function of the spatial or temporal frequency of the signal. The modulation transfer function is the ratio of percentage modulation of a sinusoidal signal leaving to that entering the device over the range of frequencies of interest. The modulation transfer function is usually presented as a graph of modulation transfer function versus log (frequency). For a square wave signal, the function is known as the CTF. Acronym: MTF (26 Mar 1998) |
| contrastimulant | 1. Annulling the effect of a stimulant. 2. An agent whose action opposes that of a stimulant. (05 Mar 2000) |
| contrasuppressor cells | A subpopulation of T-cells, distinct from T helper cells, which inhibit T suppressor cell function. (05 Mar 2000) |
| contrecoup | Denoting the manner of a contrafissura, as in the skull, at a point opposite that at which the blow was received. See: contrecoup injury of brain. Origin: Fr. Counter-blow (05 Mar 2000) |
| contrecoup injury of brain | An injury occurring beneath the skull opposite to the area of impact. (05 Mar 2000) |
| contrectation | 1. Sexual foreplay prior to coition. 2. The impulse to caress or embrace one of the opposite sex. Origin: L. Con-trecto, pp. -trectatus, to handle (05 Mar 2000) |
| control | In research, control subjects or control procedures permit comparison with experimental results. The first controlled clinical research was probably done in 1875 by the British naval surgeon James Lind who, on board the HMS Salisbury, gave sailors with scurvy either oranges or lemons or cider or vinegar or nutmeg (or another treatment) and after just six days discovered that the citrus-consuming sailors had recovered from scury, until then the scourge of extended sea voyages, while the sailors who had been given the other treatments remained uncured. (12 Dec 1998) |
| control animal | In research, an animal submitted to the same conditions as the others used for the experiment, but with the crucial factor (such as the injection of antitoxin, the administration of a drug, etc.) omitted. See: control, control experiment. (05 Mar 2000) |