Assessment of the arterial distension waveform using Doppler signal processing

To determine the distension waveform of an artery.

Ultrasound signals returned by moving structures were processed by pulsed Doppler in order to detect the displacement of the signals with respect to the transducer as a continuous function of time. The results of two sample volumes combined, one located at the anterior and the other at the posterior wall of an artery, yielded the distension waveform of the artery. The distance between the sample volumes in combination with the distension from diastole to systole provided the local distensibility and compliance coefficients. To prevent any part of the structure under observation from moving outside the sample volume, the position of the sample volume was adjusted according to the displacement detected. A disadvantage with this method is that the phase interference of closely spaced structures, i.e. layers of the arterial wall, and the readjustment of the sample volume position may cause artifacts but these can be effectively suppressed by proper processing.

The phase delay between two distension waveforms assessed simultaneously at a known distance can provide the local pulse wave velocity. Subsequently, the Moens-Korteweg relationship, expressing the relationship between pulse wave velocity and the distensibility coefficient, can be used to estimate the distensibility coefficient without measuring the local pulse pressure. The techniques, however, need further evaluation.