Doppler Ultrasound Explanation?

[carbon]

Hi to all,

I've tried my best to google my way to an article that explains how bubble formation in the bloodstream is detected by doppler ultrasound. Can anyone explain the details of this technique and/or can point me to an appropriate document?

I have a good understanding a doppler and pulsed doppler methods from my radar experience. I would like to know how they target the bloodstream for the ultrasound measurement, and if they use something simple like simple frequency binning to detect energy from a significant doppler shift (indicating a bubble?).

As always, jokes and jests are welcome along with serious responses.

Regards,
Carbon

 

[Mako Mark]

I am not sure what creates the detectable shift, but I do know that it is detected passing through the heart valve.

 

[Dr Deco]

Hello carbon:

The shift in the ultrasound frequency results from the moving target, a bubble in this case. No particular frequency is targeted. It is entirely depended on the velocity of the bubbles.

The bubbles arise in the circulatory system from supersaturated tissues in all the body. These are mostly muscle and fat tissue. Regrettable, these tissues are not really responsible for decompression sickness of the joint pain variety. This is why Doppler ultrasound bubble detectors are not good monitoring systems for “the bends.”

Joint pain DCS probably comes from free gas growing in tendon and ligament tissue and distorting pain nerves located there. (This is unproven, though.)What is really needed is a method for determining which bubbles emanate from muscle tissue and which one come from tendons and ligaments. It would be nice if muscle bubbles were red and ligament ones were blue (or round and square) so that they could be distinguished one from the other. Unfortunately, that is not the case.

Dr Deco :doctor:

 

[miketsp]

As Dr Deco stated - by itself the doppler detection is not much use:

From:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2932833&dopt=Abstract

Doppler bubble detection and decompression sickness: a prospective clinical trial.

Bayne CG, Hunt WS, Johanson DC, Flynn ET, Weathersby PK.

Decompression sickness in human beings exposed to high ambient pressure is thought to follow from gas bubble formation and growth in the body during return to low pressure. Detection of Doppler-shifted ultrasonic reflections in major blood vessels has been promoted as a noninvasive and sensitive indicator of the imminence of decompression sickness. We have conducted a double-blind, prospective clinical trial of Doppler ultrasonic bubble detection in simulated diving using 83 men, of whom 8 were stricken and treated for the clinical disease. Diagnosis based only on the Doppler signals had no correlation with clinical diagnosis. Bubble scores were only slightly higher in the stricken group. The Doppler technique does not appear to be of diagnostic value in the absence of other clinical information.

Publication Types:
Clinical Trial
Controlled Clinical Trial

PMID: 2932833 [PubMed - indexed for MEDLINE]

 

[carbon]

Hi,

Thanks for the bubble information. Do you know how the bubbles are observed in a clinical setting? Do you "see" bubbles on a imaging device? Is the doppler shift represented in a graph of some kind?

I get this mental picture of a tiny motorcycle cop hiding behind a bend in a blood vessel with his ultrasound gun....

Thanks,
Carbon

 

[miketsp]

As far as I have read the two frequency resonance technique gains over doppler.
There are quite a lot of pages on the Internet about this and there are some commercial bubble detectors working on this principle.

Example see
http://www.nsbri.org/Research/Projects/viewsummary.epl?pid=98

 

[carbon]

Thanks Mikestp,

I hadn't thought about using resonance to size the bubbles. That's a very interesting article.

Carbon

P.S. You have a great signature line. I laugh every time I see it.

 

[Dr Deco]

Hello readers:

Doppler Bubble Detection

The Doppler system uses head phones to listen to the blood flow. It sounds as though you were placing a microphone over the blood vessel but it is actually the ultrasound transducers. The flow sound is actually the Doppler-shifted ultrasound. It is shifted such that it is in the audible range. When gas bubbles are present, you hear what sounds like little “clicks” or “pops.” These “bubble sounds” are not as clear as one might hope for in the circulation near the heart, and thus bubble detection is partly an art.

Doppler systems have the advantage that they are very robust and free of motion artifacts, and yield and unequivocal signal [usually].

Resonance Systems

One of these has recently been constructed under contract to NASA and is being evaluated. It is referenced in the posting above. The problem with these systems is that they are not robust or free of motion artifacts and the signals returned are not unequivocally from gas bubbles. These are not trivial problems.

Dr Deco :doctor:

 

[Diver0001]

Hello readers:

Doppler Bubble Detection

The Doppler system uses head phones to listen to the blood flow. It sounds as though you were placing a microphone over the blood vessel but it is actually the ultrasound transducers. The flow sound is actually the Doppler-shifted ultrasound. It is shifted such that it is in the audible range. When gas bubbles are present, you hear what sounds like little “clicks” or “pops.” These “bubble sounds” are not as clear as one might hope for in the circulation near the heart, and thus bubble detection is partly an art.

Doppler systems have the advantage that they are very robust and free of motion artifacts, and yield and unequivocal signal [usually].

Resonance Systems

One of these has recently been constructed under contract to NASA and is being evaluated. It is referenced in the posting above. The problem with these systems is that they are not robust or free of motion artifacts and the signals returned are not unequivocally from gas bubbles. These are not trivial problems.

Dr Deco :doctor:

You mean it sounds like a gieger-counter....?

R..