Quantitative radionuclide angiocardiography using gold-195m

A limitation of first-pass radionuclide angiocardiography is the limited repeatability because of the relatively long half-life of technetium-99m (Tc-99m). The feasibility, reproducibility and validity of multiple sequential quantitative first-pass studies were assessed in humans using the short-lived isotope gold-195m (Au-195m) (half-life of 30.6 seconds, 262 keV), which can be directly obtained from a generator made of its parent isotope, mercury-195m (half-life of 41.6 hours). Thirty-three subjects (13 normal volunteers and 20 cardiac patients) were studied using a large-field gamma camera equipped with a medium-energy collimator. After Au-195m intravenous injections, repeat first-pass studies were performed in the left anterior oblique projection. A left anterior oblique study was then obtained after i.v. injection of Tc-99m. Left ventricular ejection fraction calculations were performed separately by 2 observers. Reproducibility of Au-195m first-pass studies was excellent. The correlation coefficients for left ventricular ejection fraction from the first and the second Au-195m injections were 0.93 and 0.98 for observers 1 and 2, respectively. The correlation coefficients between Au-195m and Tc-99m first-pass studies were 0.95 and 0.98, respectively.