Dynamic Studies of Central Circulation Using Radionuclides

With the development of the scintillation camera, it is now possible to record sequential radionuclide images from the precordium after injection of a high specific activity bolus of a radioactive intravascular indicator. From these images, the passage of the bolus can be visualized as it transits each of the cardiac chambers, the great vessels, and the lungs revealing both anatomic and functional characteristics of these elements of the central circulation. This qualitative technique can be used to diagnose a large number of congenital and acquired diseases of the heart and great vessels in a manner similar to contrast angiography. When a small computer is interfaced to a scintillation camera, time-activity curves can readily be generated from subregions of interest within the field of view of the detector. Quantitative analysis of these curves gives important and clinically useful functional information relative to the heart and circulation including cardiac output, stroke volume, left ventricular ejection fraction, left ventricular end-diastolic volume, and pulmonary blood volume. In addition, the size of intracardiac shunts can be quantified and certain wall-motion abnormalities can be detected and evaluated.