Originally Posted by Golddinger
Ok. How about an explanation. This thread is investigative, meant to field questions and receive pertinent pointed input. If you know how pressure is involved with ultrasonic waves, and how a piezo, the device used in greeting cards to play holiday chiptunes, is able to make any tissue explode like a stick of dynamite, kindly explain.Are you referring to compression of tissue? My understanding of acoustic waves is that wavelength is modulated by atmospheric pressure, and I can see how this might translate to tissue.
Unless you’ve got some reasoning or argument based on a clearly communicable understanding of the dangers involved, which I’m all ears to hear, I’m not convinced. These machines are not laser guns they’re not dynamite, by all accounts the risk factor is extremely low. They’re creating acoustic vibrations, at a set frequency, rate, and amplitude. That’s it. If you have relevant experience or understanding, tell me what I’m missing.
I’m not an expert in ultrasound. Nor am I a doctor. But I am an engineer with a background in fluid dynamics, mechanics, structures, transducers, etc. I was the guy who threw the curve in the Honors Physics classes at my University. I have a solid understanding of both sound waves and piezoelectric transducers.
When I talked about 100 MPa (Mega Pascal) earlier I was trying to make the point that this is a very high pressure level. It is roughly the same as 14,500 psi (pounds per square inch). Pressure waves at this level can cause permanent tissue damage. Of course it all depends on the details, what is the beam shape, what is the pulse duration, frequency, power density, etc.
From the literature that I have read, most therapeutic ultrasound procedures use low power densities and peak pressures usually range from 0.1 to 0.7 MPa. 100 MPa is, as far as I know, only used for things like blasting kidney stones. And when they do that they use special machines which focus the waves so that the maximum pressure is only applied at the stone, and the rest of the surrounding tissues experience much lower pressures. Even then the surrounding tissues can be severely damaged. Look up “Extracorporeal Shock Wave Lithotripsy” and its side effects.
I could go on; I’m tempted to refute several of your statements, point by point. But I’m done. If you want to know more you’re going to have to get it from someone else. Google is your friend. Try “Health Effects of Exposure to Ultrasound and Infrasound” and “Output Measurements for Medical Ultrasound” for starters.
For the rest of you, please be safe.