Coronary arteriography is the standard method for determination of coronary anatomy and assessment of atherosclerosis. However, there are definite limitations to the use of visual estimation to assess the severity of coronary artery disease and luminal stenosis. These limitations include the large intraobserver and interobserver variability that result from subjective visual grading of coronary stenotic lesions. This is especially true in the case of an intermediate coronary lesion (30%-70% diameter stenosis), where coronary arteriography is very limited in distinguishing ischemia-producing intermediate coronary lesions from non- ischemia-producing ones. Furthermore, pathologic findings have shown a lack of correlation between the severity of coronary stenosis as estimated from coronary arteriogram and the actual severity of stenotic lesions measured in postmortem hearts. Because of the major limitations of standard coronary arteriography, a method for functional measure of stenosis severity such as measurement of fractional flow reserve obtainable during cardiac catheterization is desirable. The fractional flow reserve measurement would provide valuable functional information in addition to the anatomical data obtained during routine coronary arteriography. The purpose of this research plan is to develop a technique for quantification of fractional flow reserve by combining the first pass distribution algorithm with regional lumen volume measurement technique and its implementation in the cardiac catheterization laboratory. More specifically, the aims are: (1) Investigation of the hypothesis that the sum of arterial lumen volume can be used to predict the maximum hyperemic blood flow into the coronary artery tree. (2) Investigation of the hypothesis that fractional flow reserve can be measured using the sum of lumen volume and measured blood flow from angiographic images. (3) Implementation of the fractional flow reserve measurement technique in the cardiac catheterization laboratory for human studies. The results of this research will provide improved physiological methods of quantitating coronary artery stenosis severity in patients. This quantification technique could be used to measure fractional flow reserve in patients undergoing standard coronary arteriography. PUBLIC HEALTH RELEVANCE. Angiography is the standard method for determination of coronary anatomy and assessment of atherosclerosis. However, there are definite limitations to the use of visual estimation to assess the severity of coronary artery disease and luminal stenosis. These limitations include the large observer variability that result from subjective visual grading of coronary stenotic lesions. This is especially true in the case of an intermediate coronary lesion (30%-70% diameter stenosis), where angiography is very limited in distinguishing whether a coronary lesions is the cause of chest pain. Because of the major limitations of standard coronary arteriography, a method for functional measure of stenosis severity such as measurement of fractional flow reserve obtainable during cardiac catheterization is desirable. The fractional flow reserve measurement would provide valuable functional information in addition to the anatomical data obtained during routine coronary arteriography. The purpose of this research plan is to develop a technique for quantification of fractional flow reserve by combining the regional blood flow and lumen volume measurement technique and its implementation in the cardiac catheterization laboratory. The results of this research will provide improved physiological methods for quantification of coronary artery stenosis severity in patients. This quantification technique could be used to measure fractional flow reserve in patients undergoing standard coronary arteriography.