Measurement of Heart Chamber Volumes by Analysis of Dilution Curves Simultaneously Recorded by Scintillation Camera

After a peripheral injection of Technetium-99 m , an Anger scintillation camera placed over the precordium of nine patients without and three patients with hemodynamic abnormalities was used to record in rapid sequence the flow of the injected material through the central circulatory system. After the data were processed as sequential frames of digitized spatial matrices, the position of various chambers or compartments was identified and dilution curves from six sites were obtained, providing a series of input-output relations through the central circulatory system, i.e., superior vena cava, right atrium, right ventricle, lung, left atrium, and left ventricle. These relations were assumed to be cascaded as a series of first order lag systems, with or without time delay, on an analog computer, which allowed estimation of the time constant of the transfer function of each chamber or compartment (volume/flow) by reducing the problem to a consecutive, one-parametric manipulation. Measurement of the flow rate through the series (cardiac output) permitted the volume of each chamber to be estimated. Results correlated well with mean values established by other methods.