(snip) > 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 e-mail: [log in to unmask] voice 708-570-2565 fax: 708-570-2899 *****note: area code changes from 708 to 847 on January 20, 1996***** Northwestern- a world class university, not just a football power