Fig. 2.

Parameter analysis of central nervous system studies: instantaneous peak pressure (p) against driving frequency (f). The studies are split into human, large animal, small animal and in vitro work. Any studies that conduct histologic analysis and report no damage are filled in blue, and those that report damage are filled in red. Lines of constant mechanical index (MI) and fp², a measure of acoustic radiation force (ARF), are also displayed. (a) Full parameter space (log scale). (b) Subset of parameters applicable to transcranial human delivery (linear scale, p < 1.2 MPa, f < 1.2 MHz). ARF = acoustic radiation force; f = driving frequency; fp² = measure of acoustic radiation forces; MI = constant mechanical index; p = instantaneous peak pressure.