Assessment of the distensibility of superficial arteries

Doppler signal processing cannot only be employed to detect the local blood velocity as function of time, but also to assess transcutaneously the displacement of the arterial walls during the cardiac cycle (distension waveform) and, hence, the time-dependent changes in arterial diameter relative to its initial diameter at the start of a cardiac cycle. The distension waveform normalized with respect to the local pulse pressure provides useful information about the local elasticity of the arterial wall. The displacement of the arterial wall can be obtained by processing the RF-signals within a sample volume coinciding with the arterial wall. To evaluate this method a dedicated high-speed memory system has been developed storing the RF-signal, as obtained with a conventional echo-imager in M-mode, over a number of successive sweeps covering a selected depth range. The data are transferred line after line to a personal computer (PC) and processed on the fly, thereby relieving the memory requirements of the PC. It can be concluded that a RF-signal memory in combination with a PC provides a useful tool to extract detailed diameter waveforms from the RF-signals obtained. Although the system does not process the signals in real-time the process can be considered to be on-line since the results become available within one minute after the acquisition of the data is completed.