Measurement of left-ventricular volumes using an internal standard.

When performing equilibrium radionuclide angiocardiography with two successive acquisition views, absolute left-ventricular volumes can be calculated using an 'internal standard' generated by a computer in the left-ventricular cavity. The method is based on the computed ratio of maximum to global activity in the 40 degree-left-anterior-oblique view after background correction and on the measured depth of the left ventricle in almost-orthogonal, 30 degree-left-posterior-oblique Fourier first-harmonic images. The method does not require blood sampling or correction for self attenuation. The intra- and interobserver reproducibility is excellent, even in patients with severe impairment of the ventricular-contractility pattern. When compared with a classical method requiring venous-blood counting and an attenuation correction factor, the accuracy of the internal-standard method was fairly good, with a regression coefficient of 0.90.