I'm with Don in that this brings up other opportunities for students to learn:
1) Angle correct or not angle correct, and why?
2) Parallel to vessel wall or to the flow channel, and why?
3) Are velocities in the distal, diving ICA as important as the velocity obtained in the proximal portion where the disease typically occurs? Are students taught the different ways to diagnose stenosis (Bluth, UofW) and that the distal ICA velocities may not be valid when it comes to determining amount of stenosis?
4) Are students evaluating waveform morphology of the ICA? Have seen too many, way too many, carotid reports that say 50-79% ICA stenosis because the velocity is 190 cm/sec, taken from a distal ICA, and the waveform is CLEAN and normal in appearance. Then the pt goes on to CTA and the CT report says "minimal stenosis".
So I'm hoping that students are being taught that there is more information gathered from the duplex, other than a velocity. I agree that 60 degrees is obtainable in almost all, not all, cases and that when you have to adjust your angle due to diving or tortuous vessels, you should use duplex information other than just velocities.
Jeff Stanley BS,RVT
The Surgical Clinic
Nashville, TN
________________________________
From: UVM Flownet on behalf of Don Ridgway
Sent: Mon 1/26/2009 1:21 PM
To: [log in to unmask]
Subject: Re: angles
This is a widespread problem: people not quite trained who have heard that it has to be 60 degrees, which they dutifully dial in regardless of where the flow is actually going. "It says 60 degrees, so it must be okay." What I tell my students is that this is like saying, "I can't be overdrawn-I still have checks in my checkbook."
Fortunately you're in a position to set those students straight. Some labs insist on exactly 60 degrees, some make it a range from 50 to 60 or 45 to 60. "60 degrees or less" is what we used to go by in the old days, before it became clear that angle-correcting wasn't magic, and that different angles could produce different velocity readings for the same actual blood speed.
It seems reasonable to avoid lower angles unless your back is against the wall-just can't maneuver enough to create something in the desired range. When that happens in an obviously normal study, no velocity increases, it seems to me it's nothing to get excited about. It would be more of an issue with stenotic velocities, when you want to be able to compare one study to another. We haven't heard from Jean Primozich or Rob Daigle on this lately....
Don Ridgway
-----Original Message-----
From: UVM Flownet on behalf of Kristy Peeler
Sent: Mon 1/26/2009 7:58 AM
To: [log in to unmask]
Subject: angles
I work in a small city with a new ultrasound program at the university.
There is also a new vascular ultrasound program with students rotating
through my lab. I am finding these students are being taught that the
angle of insonation should be 60 degrees and nothing else no matter how
the vessel is coursing. My students are telling me that he other
surgeons' lab and the general US depts. in the 2 hospitals also
incorporate this same school of thought. For me, it has always been 60
degrees or less. Is this common practice in other communities? I would
appreciate your feedback.
Kristy
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