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Quantitative Approaches to Color Doppler Flow Mapping of Intracardiac Blood Flow: A Review of In Vitro Methods

The development of color Doppler flow mapping in the early 1980s represented a significant enhancement of the conventional cardiovascular Doppler instrumentation that had been used successfully for over a decade. Immediately, speculative hypotheses and proposals were made for quantifying blood flow within the heart. Could the area of a regurgitant jet imaged in real time be correlated quantitatively with the severity of leakage? Could the diameter of a stenotic jet at its origin be used to assess the remaining area available for outflow from the obstructed valve? Today, these questions and many others remain unanswered. The lack of readily available quantitative information from color Doppler flow mapping can be attributed to the fact that the spatial characteristics of a color flow image are dependent on many factors. Physiological factors such as cardiac output, heart rate, driving pressure, chamber compliance, kinetic energy, and technical or instrumentation factors such as gain, pulse repetition frequency, carrier frequency, frame rate, depth, angle of incidence (both due to transducer position and scanning line angle to flow direction), and wall filter settings all combine to produce the final image of blood flow that we observe on the screen. In order to address some of these questions, we have designed a flow phantom as shown in Figure 1. It consists of a chamber for creating well-defined jet flows and a uniformly tapering