Use of digitized functional angiography to evaluate arterial blood flow

Digital angiography (DA), being a computer-based imaging system, allows for manipulation of the image data. One potential use derived from data manipulation is the production of functional images or images that reflect a physiologic parameter in addition to anatomic information. A discussion is presented of the background work employed to derive blood flow measurements using DA images, including the theoretical and practical limitations of the methodology. While absolute blood flow is hard to determine by any noninvasive and many invasive methods, flow velocity and relative blood flow in large vessels is obtainable with small volumes of intraarterial contrast injection using the basic principles of indicator dilution techniques and evaluation of the time versus density relationships of contrast bolus. An appraisal of the functional imaging method is provided, including its drawbacks and the potential areas of application.