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On Thu, 19 Aug 1999 kirvine@sa*.ne* wrote: > Don, how about the bad news: what are the sizes of the bubbles we are > hearing? By the way my boy Smithers here is not half the geek he is > pretending to be, but giving him information like this is tantamount to > feeding the dog at the dinner table. > George, you completely lost me on that one... -Will > Don W. wrote: > > > > Will, > > > > Micron range bubbles would be pretty tough, because the red blood cells are > > 6-8 Microns. Any bubbles smaller than that would be lost in the noise > > generated by the blood cells themselves. (see http://www.wadsworth.org/ > > chemheme/heme/microscope/rbc.htm) As a side note, I've imaged myself in > > the lab many times, and noticed that after several drinks, the blood > > cells tend to clump together and you can actually see the clumps come > > through on the machine. Kind of disconcerting, and convinces you to drink > > lots of water after a party ;-) > > > > The resolution limit for ultrasound depends on the wavelength of the > > ultrasound wave. This is determined by its frequency, and the speed of > > sound propagation in tissue (~1540 m/s for soft tissue). > > > > For example, a 10Mhz probe would transmit a wavelength of 154 microns > > making it difficult to image anything smaller due to diffraction effects. > > (Tells you something about the size of those blood clumps I was seeing > > doesn't it?) You can go to higher frequency probes, but the problem is > > that the attenuation goes up with the frequency, and pretty soon your > > not seeing anything but the air/skin boundary. > > > > The good news is that 154 microns is pretty small. It's ~.006 inches which > > is about the thickness of a piece of paper (well 1.5 pieces of paper). > > > > Anyway, back to your question of how hard it would be to automatically > > capture bubble counts from imaging. I don't know how to do it, but that > > doesn't mean that someone else doesn't. I think you could set up an > > _audio_ counter on a laptop with a sound card pretty easily to keep > > from having to count the bubbles manually. > > > > Later, > > > > Don W. > > > > William M. Smithers wrote: > > > > > > On Tue, 17 Aug 1999, Don W. wrote: > > > > Oh yeah, and I spent ~two years designing ultrasound > > > > machines for > > > > Siemens so I know a little about doppler echocardiography and bubble > > > > studies. > > > > > > Hi, Don! Welcome. Being an EE with various twisted experience myself, > > > I've got a question for you. I've been audio-dopplering myself for a > > > couple of years with a 3Mhz obstetric probe. That's kindof a scary > > > thing, as I've come to realize - virtually *all* of the deco > > > data (research papers) have used the same device, and > > > base their studies on audio bubble-counts. I figure that's probably > > > due to the grad-student agreeable price of an audio unit. > > > > > > How hard would it be to construct a device that *precisely* captures > > > bubble-counts? Hell, I figure if they can get pre-natal visual > > > imaging down, including user software that measures various > > > bone lengths and predicts fetal age, then a system to catch passing > > > aeortic bubble counts couldn't be all that tough. And more importantly, > > > what's the resolution of the technology? I'd really like to detect > > > micron range bubbles. > > > > > > Regards, > > > > > > -Will > > -- > > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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