The only reason that percent diameter reduction is considered important in
the evaluation of carotid artery disease is that Antonio Egas Moniz
(1875-1955)
http://www.uic.edu/depts/mcne/founders/page0064.html
developed cerebral angiography and in 1937 wrote a paper associating
carotid stenosis with appoplexy (stroke).
Moniz won the Nobel Prize in medicine, but not for angiography.  He won
the prize for advocating frontal lobotomy
http://www.pbs.org/wgbh/aso/databank/entries/dh35lo.html
The method (carotid angiography, not frontal lobotomy) was further
promoted by C. Miller Fisher and has become the "Gold Standard"
http://johns.largnet.uwo.ca/shine/cmhf/xfisher.htm

Logic and evidence suggests that it is HIGH VELOCITY that causes the
forces that lead to plaque disruption, emboli and stroke, not narrowness.
The European trials and the North American Trials have used different
methods to establish the denomonator for the %diameter reduction, as you
have.  The differences are argued, but hard to see.

 So my advice is to stop following the method of Moniz.  Stop worrying
aboiut percent diameter reduction, and "Go with the Doppler Velocity"

Kirk

On Fri, 3 Sep 1999, Carles Nicolau Molina wrote:

>         Hello Flownetters,
>
> I would like to request some advice on the evaluation of carotid stenosis.
> In our Hospital we measure stenosis by ultrasound comparing the diameter of the lumen with the diameter of the vessel at the point of maximum stenosis (real stenosis), but correlation  with the results of arteriography is sometimes poor because they compare the diameter of the lumen with the distal diameter of the carotid.
> Do you think that we must do the same by ultrasound?
>
> Carlos Nicolau
>