HP Labs Technical Reports

Angle - Insensitive Flow Measurement Using Doppler Bandwidth

Yeung, King-Wah W.

HPL-97-46

Keyword(s):flow; Doppler; bandwidth; angle; insensitive

Abstract: The ability to measure the velocity of blood flow independent of the orientation of the blood vessel could aid in evaluation of many disease processes, such as coronary lesions. Conventional ultrasonic Doppler techniques require knowledge of the beam-to-flow angle, and the Doppler effect vanishes when this angle is 90 degrees. By employing a spherically symmetrical range cell and the Doppler bandwidth instead of the Doppler shift, flow measurement of ideal uniform flow that has a blunt velocity profile can be made without knowledge of the orientation of the vessel, even when the angle of orientation is around 90 degrees. But when the technique is applied to a real flow that has a parabolic velocity profile, the Doppler bandwidth decreases as the beam-to-flow angle increases. Nevertheless, the technique can still be considered for larger blood vessels when the flow velocity in a much smaller range cell is approximately uniform, especially when the velocity profile and the range of beam-to-flow angle can also be estimated. The experimental techniques and results for flow measurements of both the ideal uniform flow and the real flow are presented in this paper.

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