Although it is logical to make the Doppler cursor parallel to the flow
stream,, that is not possible.
Streaks which appear on color Doppler images or on color power
angiography are NOT parallel to the flow stream. Color Doppler images are
subject to the Doppler equation just like other Doppler. Therefore a high
velocity stream line nearly perpendicular to the ultrasound beam patterns
forming the color Doppler image will produce a color indicating a low
Doppler shift, which is interpreted as low velocity. In contrast, a lower
velocity streamline that is nearly parallel to the ultraosund beam
patterns forming the color Doppler images will produce a color indicating
a high Doppler shift which would be interpreted as a high velocity. Thus,
on color Doppler images, "bright" colors DON'T indicate high velocity,
only a high velocity COMPONENT in the direction of the ultrasound beam
patterns.

Please don't believe me. I'm likely to lead you astray.

Anything less than 60 degrees IS NOT FINE.

Please don't believe me, I'm as likely to lead you astray as all of the
other people who write.

Do the test yourself.

Align the Doppler cursor "parallel to the [stresm] (I expect that Janson
means a color streak)". Take the Doppler spectral waveform at an angle of
70 degrees, then take it again at an angle of 60 degrees then take it
again at an angle of 50 degrees then take it again at an angle of 40
degrees.

NOW
Align the Doppler cursor 'arallel to the "vessel walls" on the B-mode
image. Take the Doppler spectral waveform at an angle of 70 degrees and
60 degrees and 50 degrees and 40 degrees.

Compare the results of the 8 measurements. Do this in a case with a
significant stenosis.

PLEASE REPORT YOUR FINDINGS HERE.

Here is what has happened every time that we did it.
I've never seen the test coparing the streak alignment vs the axis (vessel
wall) alignment. I expect that this will depend the relative angle of the
streak and whether the Doppler line is directed cephalad or caudad.

When we've aligned the cursor with the axis, the measurements
progressively increase from 40 to 70 degrees.

v40 < v50 < v60 < v70.

We explain this with comments about helical flow (which is normal except
in the distal poriton of a long straight artery such as the superficial
femoral) and converging flow (on the way into a stenosis).

Kirk


On Mon, 27 Mar 2006, JASON ROBERTS wrote:

> Definitely parallel to the the stream. 60 degrees is nice because all
> protocols are set to that, but anything less is fine. When you go above 60
> degrees the velocity will be falsely elevated. so a 0-49% at 80 degrees may
> be 69-79% false. This may lead to a surgeon look at the tech sheet then the
> MRA with malcontent toward his tech. Any published material will tell you go
> or less, 0 degrees being the optimal. Just remember the doppler shift
> corrects for anything greater than 0 degrees and no shift at 90 degrees. So
> in turn nothing greater than 60 degrees is acceptable in any lab any where
> and if someone says dont worry then I dont want my tech work done there.
>
> Jason
>
>
>> From: Dawn Stirrat <[log in to unmask]>
>> Reply-To: UVM Flownet <[log in to unmask]>
>> To: [log in to unmask]
>> Subject: HELP
>> Date: Sun, 26 Mar 2006 20:41:28 -0500
>>
>> Hi all resident gurus.
>> I need a favor, rather a question answered for me. When doing your
>> doppler recordings, is the sample volume to be placed in the center of the
>> stream, parallel to the vessel wall at 60 degrees or is it center of the
>> flow jet (highest velocity recorded) parallel to the flow channel
>> regardless of the angle? I know what I was taught and it seems there are
>> varying opinions out there. We are running about 2-2 in my lab right now.
>> My textbooks are all from the late 90's but i need to be able to bring back
>> all information to the doctor in question, so if you could also provide
>> references it would be much appreciated.
>>
>> TIA,
>> Dawn
>>
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