Comment by infinet
12 hours ago
There was a startup in Shanghai in the early 2000. Their device used multiple transducers. The probe was at least 40 cm in diameter. They did trials on uterine fibroids, among other diseases. One of the difficulties was while it looks good in theory, but the path ultrasound travels in the body is more complicated than, say x-ray or gamma ray. They expected a fine focal zone, but sometimes the focal zone was much larger than expected. This new wave of ultrasound equipment may have discovered better ways to control the sound beam.
it seems like the intesection point can be smaller than a grain of rice, and moved at 0.1mm three dimensionally [0]
[0] https://youtu.be/3Bwq2YxD9eU
This is amazing! That HIFU 20 years ago used phase array to steer beam. Don't know the size of transducer. One of the tests I heard of was on a pig leg. The damage was bigger than expected, could be in the range of few centimeters, probably due to the leg has skin, subcutaneous fat, muscle and bone. All have different sound characteristic.