A transputer-based physiological signal processing system. Part 2-System testing and investigation of flow through models of very small arterial stenoses

This paper describes the performance testing of a novel transputer-based physiological digital signal processing (DSP) unit and its application in the interpretation of pulsed Doppler ultrasound signals, obtained from models of arterial stenoses. The first test used the DSP unit as a stand-alone spectrum analyser using (1) sinusoidal frequencies (50 Hz to 10 kHz) and (2) filtered white noise (centre frequency 3 kHz, bandwidth 2.5 kHz). For the second test, the DSP unit was attached to a 30-channel multi-gate Doppler ultrasound scanner (transmitting a 4.8 MHz pulse with a repetition frequency of 4.8 kHz) and a vessel tracking unit. The Doppler ultrasound signals obtained from steady flow (100-600 ml/min) in a rigid acrylic tube (internal diameter 6 mm) were then analyzed by the DSP unit and a commercially available system. Lastly, an in vitro investigation into the flow disturbances around very small stenoses (2-25% cross-sectional area reduction), using steady flow (100-600 ml/min), was undertaken. The results indicated that the system was capable of detecting stenoses as small as 5% cross-sectional area reduction.