Quantitative radionuclide angiocardiography: Detection and quantitation of left to right shunts

In 105 patients detection and quantitation of left to right shunts was performed using quantitative radionuclide angiocardiography. The radionuclide angiocardiograms were acquired and analyzed by a gamma camera interfaced to a digital computer system. Pulmonary to systemic flow ($\text{Qp}\text{Qs}$) ratios were calculated by analysis of pulmonary time-activity histograms using a gamma variate model. All patients were studied with cardiac catheterization, left ventricular angiocardiography and radionuclide angiocardiography. The radionuclide method allowed precise detection and quantitation of left to right shunts with a $\text{Qp}\text{Qs}$ ratio of 1.2 to 3.0. There was good agreement between the $\text{Qp}\text{Qs}$ ratio calculated by oximetry at cardiac catheterization and radionuclide angiocardiography (r = 0.94). The information gathered with this nontraumatic method appears sufficiently reliable to be used in the management of patients.