[bearsnowstorm]

I also wonder how much it might heat up the brain? And whether that would be a problem for sustained use? (In practice this heating effect is occasionally limiting for some other forms of ultrasound (e.g. TEE) requiring you to take a break or reduce the power.)

[mountainriver]

This is pretty well studied now. There are safe ranges and durations, but yeah ultrasound at high frequencies is used for brain surgery today so it’s a delicate tool. It’s also lacking large scale human studies currently.