New imaging modality: Ultrasound!

[colinbm]

This looks interesting Andy & Dave.
The smallest rotation is 0.1 deg, so that is 3,600 steps to a full rotation.
 

[Andy Perrin]

Update: my rotation stage thingy arrived today! Technically it was "on time" since Ali Express quoted the original date range as "arriving March 3 - 19" when I ordered on February 29th.

 

Now the only problem is that work has gotten extremely busy, so I won't have the time to learn to program it for a while. Always SOMEthing!

[enricosavazzi]

Before some members start experimenting on themselves with industrial ultrasound equipment, it would probably be better to collect some facts about the effects of ultrasound on living tissues. For example, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8954895/ contains some basic information. It seems that high-energy ultrasound, at least, involves some risks. Check also the "Similar articles" link on that page.

 

It is also well known that one should not dip one's fingers into an operating ultrasonic cleaner. One risk is said to be damage to bone marrow, for example. Narrowly focused high-energy sound waves are used, or at least have been experimented with, in the breaking-up of gall and kidney stones. Internal bleeding is one of the possible complications in this case.

 

At the high end of the energy spectrum, it is well known that sound waves produced by underwater explosions can easily kill divers within a much larger radius than in air. During WW2, military divers were recommended to quickly reach the water surface and lay as flat as possible at the surface whenever the enemy started to use depth charges or grenades thrown into the water.

 

I don't know whether there are concerns about frequent exposure to ultrasound, even at levels that are regarded as safe for occasional exposure. Although medical ultrasound equipment is quite safe during occasional hospital visits, things might change for lengthy exposures e.g. of hours, or daily exposure for months on end.

[Andy Perrin]

While that may be true as a general caution, let me be explicit that I am NOT experimenting with industrial ultrasound equipment. Medical ultrasound machines are DESIGNED for safe exposure and there are NO known examples of any patients being harmed by a medical ultrasound machine in any way. (And who on earth, on or off our forums, is going to expose themselves to a medical ultrasound for hours even, much less days?) Ultrasound does not travel far through air, as described in the previous discussion, so unless you are in physical contact with the transducer, just being in the same room with it cannot hurt you because the sound won’t reach you, even if it’s on. Basically it’s probably safer to experiment with medical ultrasound machines than even UV-A, which we know can damage our eyes. 
 

The only thing I noticed that caught my attention as a potential danger in the paper was the possibility of nerve damage to the hands from holding the probe for long periods, but I have no intention of holding the probe at all. I’m setting up a tomography system and the probe will be stationary. 
 

Generally the dangerous ultrasound is at low frequencies (20-100kHz) and high energy levels. Medical ultrasound is at 2-20Mhz and much lower energy levels. In other words, it makes more sense to be scared of a ultrasonic polisher than a medical ultrasound machine.