| LF | labile factor; lactoferrin; laryngofissure; Lassa fever; latex fixation; left foot; left forearm; le... |
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| LFD | lactose-free diet; large for date [fetus]; late fetal death; lateral facial dysplasia; least fatal d... |
| LFT | latex fixation test; latex flocculation test; left fronto-transverse [fetal position]; liver functio... |
| LOCM | low molecular contrast medium |
| ELF | elective low forceps; extremely low frequency |
| 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) |
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| 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 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) |
| 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) |
| simultaneous contrast | The enhancement of the visual sensation of white when a white object is viewed adjacent to a black object; the black object also appears blacker as a result of the contiguity of white. Adjacent complementary colours also appear brighter; e.g., green appears a brighter green and red a brighter red if these two colours are viewed side by side. (05 Mar 2000) |