Should we be concerned that ultrasound is capable of effecting changes in the brain? Ultrasound is one of those "safe" medical operations that you don't think too much about because it's not chemical, radioactive, or built out of superconductors.
For example, 3D fetal ultrasounds bombard a baby but they are really only done out of pure vanity for parents. They don't tell doctor's anything they don't already know from the boring standard ultrasound.
The long-term effects of tissue heating and cavitation are not known. Therefore, ultrasound scans should be done only when there is a medical need, based on a prescription, and performed by appropriately-trained operators.
In the article I didn't see what type of ultrasound they are using. I don't know a great deal about ultrasound, but I do know that there is a difference between diagnostic (imaging) and therapeutic ultrasound systems. It's likely they were using a therapeutic system for this test.
I was having chronic muscle spasms in my right shoulder blade area, and the physical therapist used therapeutic ultrasound on me. It melted the spasms like butter. Several months of terrible pain gone in an instant. I was never so tempted to steal a machine in my life.
Ultrasound is not without risk. The general advice is to follow the ALARA principle (as low exposure as reasonably achievable). In the early 90's the FDA under pressure from manufacturers approved a 7-fold increase in the power output of ultrasound. Part of that approval was that ultrasound machines show feedback to technicians on estimated amount of tissue heating. That's one of the main concerns. E.g., in a fetus, heating tissue above 4 degrees or so causes damage and that level of heating is possible, especially around areas of bone.
From the paper - they don't use ultrasound itself to generate the effect, they use ultrasound to activate injected 'micro-bubbles' in the brain which disrupt the blood-brain barrier.
For example, 3D fetal ultrasounds bombard a baby but they are really only done out of pure vanity for parents. They don't tell doctor's anything they don't already know from the boring standard ultrasound.