Objectives: To give an overview of some of the methods of measuring volumetric blood flow using Doppler ultrasound.

Abstract: There are many approaches to the measurement of volumetric blood flow using Doppler ultrasound techniques, all of which are, of course, subject to errors to a greater or lesser extent. The best approach in any circumstance, usually the method which introduces the smallest errors, will depend on a variety of factors, and there is certainly no single universally applicable best method. Before attempting to measure flow it is important not only to consider the size, location, and type of flow in a vessel of interest, but also additional important questions such as: Is it really necessary to measure absolute flow? Would mean velocity be equally useful? Would a measure of the relative changes in flow or velocity suffice? It is then a question of matching the measurement approach to the required information, since there is little point in using techniques which are more sophisticated than strictly necessary, if this has the concomitant effect of reducing accuracy.

The purpose of this talk is to survey some of the methods of measuring flow using Doppler ultrasound techniques. Amongst the approaches that will be discussed are the 'standard' duplex method, multigate techniques, the attenuation-compensated method, the assumed velocity profile method, and C-mode techniques. Methods based on the use of contrast agents form a separate class of measurement techniques and will only be discussed in passing.