Re: Doppler Jargon
From: Logamuthu Krishnan (logamuthu@gmail.com)
Thu Jun 29 05:34:42 2006
Zillion Thanks for a very lucid review.
I am sure many other readers will thank you too.
To pick your brain a bit more -
I have come across some vendor-brochures claiming their product to be
"Directionality-separated" "Multidirectional" etc., What do you make out of
this claim of being "Directionality-separated" for what looks like a very
low level vascular Doppler - too ancient to be a Power Doppler - probably
just CW! (Vendor name omitted to avoid flaming!). And... What
is "Multidirectional" as opposed to the mere 2-way "Bi-directional" we know
of?
Maybe the thread is worth continuing - to throw more *light* on this issue -
*not heat*, of course!
You must also have heard of Inverse Doppler Effect and Pseudo-Doppler!! More
will follow! if co-readers chime in!
Prof.K.Loga muthu krishnan.
On 6/29/06, Terry DuBose <terrydubose@sbcglobal.net> wrote:
>
> This web site may help.
>
> http://www.centrus.com.br/DiplomaFMF/SeriesFMF/doppler/capitulos-html/chapter_01.htm
>
> also this page, scroll down to Doppler:
> http://en.wikipedia.org/wiki/Doppler_ultrasound#Doppler_sonography
>
> However, let me see if I can answer briefly. With true Doppler effect,
> the direction of the moving object (blood is a scatter/reflector in the case
> of ultrasound) is in relationship to the transducer. The color displayed
> will be dependent on whether the blood flow is toward the transducer or
> away. With spectral Doppler analysis the same principle applies except flow
> away from the transducer will be below the base line, or above if flow is
> toward the transducer, and displayed as a spectral wave form..
>
> Non-directional "Doppler" is probably not true Doppler (it may be done in
> different ways). It may be called "power Doppler", "amplitude Doppler", or
> something else depending upon the manufacturer. The advantage is it is
> much more sensitive to very slow flow that may not be detected with
> directional Doppler. Another advantage is it will not "alias", which is a
> type of false reading (not really false, but that is the easiest way to
> explain it). The disadvantage is that it does not tell if flow is toward
> the transducer or away.
>
> Range-gating is a software control that allows the machine to look at
> Doppler shift information (spectral only) at a specific point along a
> vector. In this way a specific vessel can be interrogated for flow
> direction and velocity (amount of Doppler frequency shift). Range-gating
> only takes place with pulse-Doppler machines. Continuous Wave (CW) Doppler
> reads all frequency shifts all along the vector, even if it passes through
> two or more vessels.
>
> I hope this helps... it is a very basic explanation. If you ask more
> specific questions, I will try to respond, and am sure others will also.
>
> Terry J DuBose, M.S., RDMS,
> UAMS Little Rock, Arkansas
>
> --------------------------------
>
> --------------------------------
>
> --------------------------------
> *"Prof.K.Loga muthu krishnan" <logamuthu@gmail.com>* wrote:
>
> I am getting confused with Doppler jargon in recent times - especially
> by brochures from vendors - I need some clarification of two areas -
> 1. Directionality in Doppler - where does it reside? Is it probe-based
> or console-circuitry-based? What is the advantage of a Non-Directional
> Doppler over a Directional Doppler?
> 2.Range-Gating - where does the responsible hardware / software reside -
> in the transducer or in the console?
> I need some physics-based enlightenment. Thanks!
>
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