Never heard that. Ultrasound don’t rely on radiation, it’s just sound at different frequency.
It may be expensive and difficult to operate, though. You need not just the machine itself but also some kind of software which can display the images in real-time. Also, you’d have to be able to use the machine, the software and most importantly be able to read and interpret the result, for it to be useful.
Not sure if they are actually restricted items, but I wouldn’t know what to do with one even if they gave me one for free.
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