Variation of Doppler ultrasound spectral width in the post-stenotic velocity field

The spectral features of post-stenotic velocity fields, recorded in a steady flow model using a 20 MHz pulsed Doppler ultrasonic velocimeter, were analysed and compared to flow patterns revealed by flow visualization. Maximal centrestream spectral width relative to velocity occurred downstream of the stenosis in the region of jet break-up. Proximal to this point, off centre spectral width, in the shear layer between jet and flow recirculation, was greater than centrestream spectral width. The increased velocity gradients in this shear layer would appear to be the source of the immediate increase in spectral width downstream of a stenosis reported for continuous wave velocimeters.