The application of quantitative digital subtraction angiography (DSA) to the assessment of ventricular function in humans, particularly during exercise, has been limited by cardiac and respiratory motion. The purpose of this research plan is to develop and apply in patients a motion immune dual-energy digital subtraction technique which will provide for the quantitative assessment of both global and regional left ventricular function during rest and exercise. More specifically, the aims are: First to optimize the dual-energy imaging mode, which as already been developed in the canine model, for use in human cardiac imaging. Exploiting the motion immunity of this technique, it is then proposed to develop a digital subtraction dual-energy ventriculographic exercise stress test using a central venous injection of contrast. This exercise test will be utilized to assess the functional significance of coronary stenoses at the time of cardiac catheterization. Secondly, a single plane videodensitometric analysis of dual-energy subtraction images will be investigated to test the hypothesis that absolute global left ventricular volumes can be accurately measured independent of geometric assumptions. This will be done using a direct measure of blood iodine concentration. Thirdly, it will be determined whether accurate videodensitometric volume measurements can be made using a calculated concentration of iodine in the aorta, as compared with the direct measurement. Thus videodensitometric volume determinations may be possible using only a central venous injection of contrast. Fourthly, a phase-matched rest/exercise wall motion display will be developed to quantitate regional myocardial function independent of cardiac coordinate systems. The sensitivity of this technique in assessing regional ischemia will be assessed in a dog model using ultrasonic crystals. Finally, the functional significance of coronary stenoses in patients will be determined by the dual- energy rest/exercise stress test and will be compared to the physiologic significance of the same stenoses as defined by coronary blood flow reserve measurements obtained using DSA based parametric imaging. The results of this research will provide improved methods of quantitating global and regional left ventricular function using dual-energy digital subtraction angiography in patients. Furthermore, these techniques have the potential to be utilized as an outpatient screening test for significant coronary artery disease and for the serial assessment of rest and exercise ventricular function.
