Quantitative flow estimation with transcutaneous Doppler ultrasound

During the last 20 years, Doppler ultrasound has become widely accepted as a means for qualitative or semi-quantitative assessment of blood-flow patterns. Application to transcutaneous quantitation of volume flow (in milliliters/sec), however, has proved difficult. Generally, it has been assumed that the angle between the vessel axis and ultrasound beam must be determined precisely through imaging or triangulation. In addition, because volume flow is a product of velocity and area, the true area of the vessel lumen has been assumed to be essential to volume flow estimation. It has also been considered necessary to measure the velocity profile across the lumen on a point-by-point basis. A new approach to volume-flow measurement is being developed to avoid these problems, wherein flow is measured perpendicular to an arbitrary tomographic plane. The area of the lumen (as projected onto the measurement plane) and the area-average velocity of the fluid per-pendicular to this plane are the only two characteristics relevant to the estimation of volume flow. The product of these two quantities is, by definition, volume flow. As a result, precise measurements of vessel orientation and true diameter and details of the velocity profile are not required.