Dependence of Doppler line-flow spectrum on range and beam-to-flow angles: an experimental approach

A theorem introduced by V.L. Newhouse and J. Reid (see Ultrasonics Sym. Proc., vol.3, pp.1533-1536, 1990) predicts that the Doppler spectrum bandwidth originated by a line flow crossing a whole sound field depends only on the flow-to-beam axis angle and is independent of the location of the scatterers. Experimental tests of this theorem, using a thread phantom operated at beam-to-flow angles ranging from 60° to 90° and over a wide series of ranges, are presented. The tests were made with a pulsed Doppler system specially designed to perform optimal real time spectral analysis of data obtained in this application. The prototype system and the experimental procedure adopted for demonstrating in vitro the invariance of the Doppler spectrum are discussed