# cardiothoracic ratio

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## ratio

[ra´she-o] (*L.*)

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.

## car·di·o·tho·rac·ic ra·ti·o

the ratio of the horizontal diameter of the heart to the inner diameter of the rib cage at its widest point as determined on a chest roentgenogram.

## cardiothoracic ratio

[-thôras′ik]

the ratio of the diameter of the heart at its widest point to the maximum width of the thoracic cavity, assessed by examining a chest x-ray. The normal ratio is less than 1:2.

## car·di·o·tho·rac·ic ra·ti·o

(kahr'dē-ō-thōr-as'ik rā'shē-ō)The ratio of the horizontal diameter of the heart to the inner diameter of the rib cage at its widest point as determined on a chest roentgenogram.

## ratio

[L.] 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. It differs from a proportion in that the numerator is not included in the denominator. Thus x/(x + y) is a proportion, x:y is a ratio.

**A-G ratio**

albumin-globulin ratio.

**area-incidence ratio**

the number of new cases of a specific disease in a population during a specified time period, divided by the geographic area size in which the observations are made, multiplied by the time elapsed, e.g. cases per hectare per month.

**arm ratio**

a figure expressing the relation of the length of the longer arm of a mitotic chromosome to that of the shorter arm.

**A/S ratio**

the diameter of the ascending aorta divided by the diameter of the aorta at the sinus of Valsalva; less than 1 in a normal dog. In subaortic stenosis it becomes greater than 1.

**cardiothoracic ratio**

the ratio of the transverse diameter of the heart to the internal diameter of the chest at its widest point just anterior to the dome of the diaphragm.

**cross ratio**

see odds ratio.

**fetal death ratio**

the number of fetal deaths divided by the number of live births.

**gain ratio**

individual animal's gain/average gain in group × 100.

**lecithin-sphingomyelin ratio**

the ratio of lecithin to sphingomyelin in amniotic fluid. See also lecithin, sphingomyelin.

**odds ratio**

see odds ratio.

**rates ratio**

the ratio between two rates. See odds ratio and relative risk ratio (below).

**relative risk ratio**

the ratio between the rate (of mortality or some such parameter) in one group of animals and the rate in another group, used as a standard and the comparison expressed as a ratio. See also relative risk.

**sex ratio**

the number of males in a population per number of females, usually stated as the number of males per 100 females.

**S/P ratio**

secondary-to-primary ratio. An indicator of fleece type in sheep, the greater the ratio the finer the fleece. Coarse-wool sheep have ratios of 3:1 to 4:1; merinos have a ratio of 20:1.

**stillbirth ratio**

the ratio of stillbirths to total births in the population.

**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.

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