I agree with your important, if somewhat obvious, points. I would say,
however that the 50 vs 60 degree difference is significant.  Remember, the
mathematical corrections are not perfect and above 60 degrees are deemed
inaccurate.  Still the velocities are slightly exaggerated in a ballooning
fashion the further get from 0 degrees.
Again using 60 degrees probably contributes to the doppler overcalling
phenomenon.
T Cunningham, RVT, RDCS
----- Original Message -----
From: Bill Schroedter <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, September 07, 1999 5:07 PM
Subject: Re: Carotid stenosis.


>      Just had to jump in here. Clearly, the point was made that you need
>      to use spectral analysis as the primary classification tool. To
>      whatever school of thought you subscribe, it is imperative that you
>      VERIFY your results, not blindly follow someone else's. Meticulous
>      attention and CONSISTENCY is the more important than 50 vs 60
>      degrees. I measure the residual lumen routinely but use it
>      primarily to confirm the spectral data category. If there is
>      disagreement, we call it an image/Doppler mismatch, then one needs
>      to look a little more closely, take a few more images, ask why?
>      Understand the original velocity data identified stenosis in the
>      bulb, hence all the recent "new" criteria for grading the important
>      cutoffs. I also believe it is inherently wrong to lessen our
>      accuracy or at least our description of what is there (ie: call a
>      50% lesion in the bulb normal because the residual lumen is reduced
>      to that of the distal ICA?) in order to correlate with an imperfect
>      gold standard that will be gone in a few years anyway. Mostly, I
>      agree with Kirk's reply. If you could look at the raw data of the
>      duplex results in the NASCET trials, throw out residual lumen
>      measurements and/or categories and look solely at velocities, I
>      believe you would find an obvious break between symptomatic and
>      asymptomatic individuals. Go with the flow! (Sorry I couldn't
>      resist!)
>
>      Bill Schroedter
>      Venice,FL.
>
>
> ______________________________ Reply Separator
_________________________________
> Subject: Carotid stenosis.
> Author:  UVM Flownet <[log in to unmask]> at Internet
> Date:    9/3/99 11:16 PM
>
>
>         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 ste
> nosis), but correlation  with the results of arteriography is sometimes
poor bec
> ause they compare the diameter of the lumen with the distal diameter of
the caro
> tid.
> Do you think that we must do the same by ultrasound?
>
> Carlos Nicolau
>