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>  I
>still think frequency is more accurate than velocity (another can of worms!).
>
>I'm interested in what other Flownetters use for their criteria.
>
>JP Hughes, RVT, RCVT
>Easton Hospital
>Easton, PA
whoa, can't let this one past! arguments from the u of washington group
notwithstanding, *all* of the difficulty in trying to determine the true
Doppler angle and, therefore, the inaccuracy of estimating velocity apply
equally to the use of frequency shift as a standard- i.e., if your angle is
not 60, your frequency shift may under- or overestimate stenosis to the
same degree as does estimated velocity-
once again (with feeling) measuring freqency shift is a piece of cake, but
knowing the Doppler angle, and therefore, legitimate comparison to a
frequency shift standard is not
furthermore, i read studies from 3 different types of machines (atl UM9,
acuson128, and hp), each with at least 2 different probes with different
Doppler carrier frequencies- remember u of wash criteria assume 5MHz
Doppler, do you convert the frequency criteria when you Doppler carrier
frequency is different?
i contend that any inaccuracy in velocity estimation is simply the
perpetuation of inaccurate Doppler angle/freqncy shift measurement
joe


Joseph R Schneider, MD, PhD
Associate Professor, Vascular Surgery, Northwestern Univ Med Schl
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