Left Ventricular Cavity-to-Myocardial Count Ratio: A New Parameter for Detecting Resting Left Ventricular Dysfunction Directly from Tomographic Thallium Perfusion Scintigraphy

Patients with reduced left ventricular function or aneurysms have cavities that appear dark on SPECT thallium scintigrams. We hypothesized that a quantitative index, which relates thallium activity in the left ventricular cavity to that in the myocardium (C/M ratio), could provide information on left ventricular function. A group of 80 patients who had both exercise SPECT thallium imaging and cardiac catheterization were studied. The C/M ratio was obtained from the shortaxis tomogram on both exercise and rest images. Counts in a 2×2 pixel region of interest in the left ventricular cavity were divided by the number of counts in the «hottest» area of the myocardium