Dynamics and Limitations of Blood/Muscle Interface Detection Using Doppler Power Returns

A new method that relies on backscattered Doppler power from red cells to locate and track blood/muscle interfaces is described. It allows current pulsed Doppler flowmeter systems to yield continuous information on internal vessel diameter and to evenly distribute range gates within the lumen. A smal signal model is fommulated that describes this feedback approach and indicates the relationships between system parameters (filter characteristics, gain settings, sampling rate, etc.) and tracking dynamics. Large signal nonlinear effects, problems of initial lock-in, potential loss of lock, and sources of tracking error are then outlined to provide a thorough description of this novel technique.