You are correct Joshua. But.... all the other imaging modalities also obtain
2D data - they simply construct 3D as do we. US has typically significantly
higher resolution than does angiography, CTA, or MRA. Additionally, those
modalities have limitations on the # of slices the use to create the image
while we have virtually infinite #'s of slices as we scan through the area
of interest. While our instrument generated 3D reconstruction is marginal at
best (at this point in time), our mental 3D reconstruction is superb. As
Bill Johnson notes, the key is physiology which creates a synergy with the
imaging. We would NEVER call a stenosis based on velocity alone. But I do
strongly agree with you, standardization and especially consistency is
obtaining the data is critical. 

If you search back in the Flownet archives from about a year ago or so, you
will find a post by Dr. Kirk Beach regarding reproducibility. To summarize
his post (and correct me if I am wrong Dr Beach)  

Comparing a series of 20 Doppler vs Angiography publications, angiography
and Doppler velocity had the following disagreement rate: 
Systolic Velocity 32%
Diastolic velocity 33%
ICA/CCA ratio 33% in native arteries.  
For stented arteries, disagreement was 20%, 30% and 30%.  

Comparative repeat ultrasound measurements disagreement :
7% on systolic velocity 
11% on ICA/CCA ratio

In summary - 
Ultrasound  -  7% disagreement using PSV
Angiography - 24% disagreement between readers 

The take home, US is significantly more reproducible than is angiography.


William B Schroedter, BS, RVT, RPhS, FSVU
Technical Director, Quality Vascular Imaging, Inc
4120 Woodmere Park Blvd
Suite 8B
Venice, Florida  34293
(941) 408-8855 office
[log in to unmask] 

-----Original Message-----
From: UVM Flownet [mailto:[log in to unmask]] On Behalf Of Joshua Waks
Sent: Thursday, October 18, 2012 1:02 PM
To: [log in to unmask]
Subject: Re: CCA criteria

High quality duplex scanning is exceedingly important; however, there's too
many variables and controversy.  Intra-observer variability will always
create a difference, but if you're looking at a stenosis of >70%, where do
you align the sample volume to?  Vessel wall or flow jet?  If it's aligned
to the flow jet, the transducer being at a slightly different approach, the
tech will view a slightly different jet, and get a different velocity,
because we're viewing a 3- dimensional object in 2 dimensions.  GREATER
I know this, and I just graduated from my Vascular Tech program!

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