The FDA's upper limit for diagnostic ultrasound is Isppa = 190 W/cm^2, not 190 W/cm^3. That is for the pulse average, and it measures intensity of a cross section of the beam which is why it is /cm^2 rather than /cm^3. The actual energy deposited in tissue per cm^3 for a beam conforming to the FDA limit would be much lower than 190 W/cm^3.
That's also only the intensity of a brief pulse. If that power were sustained, 100 W/cm^3 for any significant amount of time would definitely cook the brain; a microwave oven has lower power per unit volume than that. It would raise the temperature of the targeted area by 24 C per second.
For the long-term temporal average (Ispta) the FDA's upper limit is 3 orders of magnitude lower: 94 mW/cm^2.
Wouldn't Tolerance also be a potential problem? Let's say, for instance, that you use neuromodulation to treat depression, but it only works in the short term and in the long term it causes the problems to get worse.
The FDA's upper limit for diagnostic ultrasound is Isppa = 190 W/cm^2, not 190 W/cm^3. That is for the pulse average, and it measures intensity of a cross section of the beam which is why it is /cm^2 rather than /cm^3. The actual energy deposited in tissue per cm^3 for a beam conforming to the FDA limit would be much lower than 190 W/cm^3.
That's also only the intensity of a brief pulse. If that power were sustained, 100 W/cm^3 for any significant amount of time would definitely cook the brain; a microwave oven has lower power per unit volume than that. It would raise the temperature of the targeted area by 24 C per second.
For the long-term temporal average (Ispta) the FDA's upper limit is 3 orders of magnitude lower: 94 mW/cm^2.
thanks, that's very good to know!
Wouldn't Tolerance also be a potential problem? Let's say, for instance, that you use neuromodulation to treat depression, but it only works in the short term and in the long term it causes the problems to get worse.