Evaluation of a Computerized Technique for Determination of Cardiac Output and Central Circulation Times Using Gamma Camera and 113mIndium

Abstract

A method for quantitative radiocardiography using a gamma camera, multichannel analyser, computer, and magnetic tape recorder is presented and evaluated. [^113mIn]transferrin (a pure gamma emitter with an energy of 392 KeV, half-life of 99.5 min) has been used as the intravascular tracer. This has some advantages over ¹³¹I-human serum albumin and ⁹⁹Tc-human serum albumin. The cardiac output was determined simultaneously by radiocardiography and an ordinary indicator dilution technique based on continuous sampling of arterial blood. The coefficient of correlation between the results of the two methods was 0.96. The mean pulmonary circulation time could be selectively determined. It was 4.90 sec (S.D. 0.84) in 14 healthy subjects, which represented 75.8 per cent of the interventricular circulation time. The mean pulmonary blood volume in the 14 subjects was 297 ml/m² (S.D. 38) and the mean pulmonary plasma volume 179 ml/m² (S.D. 21), or 11.1 per cent (S.D. 1.7) of the total plasma volume. The presented method is rapidly performed without stress for the patient, can be repeated at frequent intervals, and gives reliable information about cardiac function and pulmonary circulation.