The authors carried out experimental and clinical studies of left ventricular volume measurement using equilibrium-gated blood pool scan. Using phantoms, we experimentally obtained a regression equation between radioisotope levels and camera counts. From this equation, we deduced a regression equation between camera counts and volumes, which was then used for calculation of left ventricular volumes using count technique. In an experiment using phantom with various volumes, we obtained a favorable result that the average absolute error between the true and measured volumes was as small as 6.8%. In 11 patients, we calculated the left ventricular volume and ejection fraction employing the regression equation and compared the calculated values with the values obtained by cinemascopy. This comparison disclosed an excellent correlation (r = 0.955 for end-diastolic volume, 0.997 for end-systolic volume and 0.853 for ejection fraction). Mean absolute error was 16.2% for end-diastolic volume and 16.0% for end-systolic volume. These results indicate that this technique is clinically applicable.
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