Attenuation correction of equilibrium radionuclide angiography for noninvasive quantitation of cardiac output and ventricular volumes

Abstract Gated equilibrium radionuclide angiography (RNA) provides count information which is proportional to ventricular volumes. In order to convert ventricular count data directly to accurate absolute volumes, we performed attenuation correction on equilibrium radionuclide angiograms by means of a simple geometric method of attenuation distance quantitation. Attenuation distance defined during imaging agreed with similar measurements obtained during fluoroscopy ( r = 0.86). In seven patients, 23 simultaneous cardiac output determinations by Fick and radionuclide imaging techniques showed excellent correlation over a wide range of cardiac outputs ( r = 0.91). Radionuclide angiographic ventricular volumes correlated with contrast angiographic ventricular volumes in 28 patients ( r = 0.80). The weaker correlation found for ventricular volume data may be due to inaccuracies in ventricular volume calculation when single-plane contrast angiography is applied to patients with wall motion abnormalities. We conclude that attenuation-corrected RNA allows direct calculation of cardiac output and ventricular volumes in individual patients without use of regression equations.