QUANTITATIVE TECHNIQUES IN ARTERIAL DOPPLER ULTRASOUND

A brief review is given of quantitative Doppler ultrasound techniques applied to arteries. Doppler ultrasound procedures can be split into waveform analysis, volume flow measurement and, recently, colour flow imaging. The pulsatility of the Doppler waveform has been used to assess distal vascular resistance. In the obstetric field the increase in pulsatility seen in the umbilical artery waveform when there is placental disease is a good predictor of fetal compromise. Considerable effort has been undertaken over the past 20 years in the assessment of carotid artery stenosis using Doppler. Both the peak systolic velocity in the internal carotid and spectral broadening have been related to the degree of stenosis. More complex waveform analysis methods such as principal component analysis have been used, however these have not passed into clinical practice. Measurement of volume flow in arteries using a duplex system is attractive, but in practice there may be large errors and this technique is not routinely performed. Recently cardiac output has been measured by a Doppler device using the attenuation-compensation principle. This promising technique is currently under assessment. Colour flow Doppler raises new prospects for quantitation in Doppler. At present the colour flow Doppler image is assessed by eye. Quantitative techniques in colour flow are likely to be introduced as experience with these systems grows.