Measurement of absolute left ventricular volume from gated blood pool studies.

was given by the ratio of the attenuation-corrected end-diastolic count rate from the gated study to the count rate per milliliter from a blood sample. Attenuation correction was made by dividing the end-diastolic count rate by e ud, where u = the linear attenuation coefficient of water and d = the distance from the skin marker to the center of the left ventricle in the anterior view divided by sin 400 to yield the depth of left ventricle in the left anterior oblique view. In the phantom studies, the correlation between radionuclide and true volume was 0.99 (radionuclide = 1.03 true 3 ml); the standard error of the estimate was 8 ml. In the patient studies, the radionuclide end-diastolic volume was used to calibrate the left ventricular time-activity curve, yielding left ventricular volume throughout the cardiac cycle. The correlation between radionuclide and angiographic enddiastolic volume was 0.95 (radionuclide = 0.97 angiographic + 3 ml); the standard error of the estimate was 36 ml. The correlation between radionuclide and angiographic end-systolic volume was 0.95 (radionuclide 1.01 angiographic + I ml); the standard error of the estimate was 33 ml. This method permits direct determination of absolute left ventricular volume without assumptions about the shape of the ventricle or the necessity of using regression equations to convert volume "units" to true volume.