A method for the calculation of areas under indicator-dilution curves.

Abstract

One hundred indi-cator-dilution curves were recorded in 9 dogs with a linear densitometer (Waters XC250A) after injecting 1-3 ml of indocyanine green (1.25 mg/l) in the right atrium or pulmonary artery and sampling from the descending aorta. A curve-area formula, utilizing 3 time intervals and 2 concentration values, was derived by fitting the indicator-dilution curves with 3 parabolas and an exponential. The areas under the total curve and under the segments preceding and following the onset of exponential decay were calculated separately and found to agree closely with similar areas determined by 1) planimetry, 2) summing at 1-sec intervals, and 3) semilogarithmic replotting. The mean difference between total curve areas determined by the area formula and by a combination of methods 2 and 3 was 0.02 cm2 (0.01%) standard deviation (SD) of differences 0.65 cm2 (1.4%). Application of the area formula offers a considerable saving in time with no demonstrable decrease in accuracy in comparison with current technics for assessing areas under indicator-dilution curves.