A new geometric procedure for in vivo pulsed Doppler evaluation of velocity distribution inside the diametrical section of large arteries in humans.

A new geometric procedure determination of velocity profiles inside large human arteries, such as the brachial and femoral, has been developed. The procedure requires the use of two crystal element Doppler probes and a highly precise micromanipulator with three degrees of freedom. Precise positioning is needed to obtain the required high degree of parallelism between the vessel axis and the plane containing the two crystal elements. Once the appropriate degree of parallelism is achieved, a controlled translation of the probe, perpendicular to the ultrasonic beam plane, allows velocity waveforms to be recorded at sequential radial positions across the measured artery. Velocity profiles obtained with this geometric procedure depended on the type of artery investigated. The profiles measured with the geometric procedure were more symmetrical than those found using the electronic range-gated time system of reception. While the geometric and electronic methods were almost identical in determining the diameter values of the three arteries measured, the geometric procedure enabled greater accuracy for detailed analysis of velocity profiles in the peripheral large arteries in humans. Although the present methodology is not applicable in clinical practice due to prolonged data acquisition time (approximately 45 s) it is expected that future equipment improvements will reduce this time significantly.