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an expression of the quantity of one substance or entity in relation to that of another; the relationship between two quantities expressed as the quotient of one divided by the other.
A/D ratio adult versus developmental toxicity ratio; the ratio between the toxic effects of a substance on adults (humans or animals, especially pregnant females) and such effects on developing embryos or fetuses.
A-G ratio (albumin-globulin ratio) the ratio of albumin to globulin in blood serum, plasma, cerebrospinal fluid, or urine.
arm ratio a figure expressing the relation of the length of the longer arm of a mitotic chromosome to that of the shorter arm.
benefit-risk ratio a determination of the potential of a research study for positive effects on patients compared to the risks of doing harm.
cardiothoracic ratio on a chest radiograph, the ratio of the transverse diameter of the heart to the internal diameter of the chest at its widest point just above the dome of the diaphragm.
grid ratio a ratio comparing the height of lead lines in an x-ray grid to the distance between the lead strips.
inspiratory-expiratory ratio the ratio of the inspiratory time to the expiratory time during the breathing cycle. Normally, expiratory time will be longer than inspiratory time; if the inspiratory time is longer than the expiratory time, gas trapping may result.
lecithin/sphingomyelin ratio see lecithin-sphingomyelin ratio.
risk ratio relative risk.
sex ratio the proportion of one sex to the other; by tradition the number of males in a population to the number of females, usually stated as the number of males per 100 females.
signal-to-noise ratio the ratio between the amplitude of a signal being measured and that of the noise.
urea excretion ratio the ratio of the amount of urea in the urine excreted in one hour to the amount in 100 ml of blood. The normal ratio is 50.
zeta sedimentation ratio (ZSR) a measurement comparable to the erythrocyte sedimentation rate, except that it is unaffected by anemia. The packed-cell volume (zetacrit) of a blood specimens is calculated by centrifuging the specimen in a Zetafuge, a specially designed instrument that produces controlled cycles of compaction and dispersion and allows rouleaux to form and sediment rapidly. The zetacrit divided into the true hematocrit gives the zeta sedimentation ratio.
signal-to-noise ratio (SNR)
the number used to describe the relative contributions to a detected signal of the true signal and random superimposed signals or "noise."
signal-to-noise ratioAn MRI term for the ratio between the amplitude of the received signal and background noise, which may obscure that signal. SNR, and by extension, image quality, can be improved by increasing the number of excitations, field of view, slice thickness, etc., while factoring the electrical properties of the patient being studied and type of receiving coil used.
signal-to-noise ratioMRI The ratio obtained from the relative contributions of detected true signal to that of random superimposed signals–'noise'. See Magnetic resonance imaging.
the ratio of a specific response, e.g. counts per minutes (cpm) from a radiolabeled substance, to the background cpm; the latter is substracted from the former to give the value of the specific response.