Acoustic radiation force

The steady (time-averaged) force exerted on tissue by an ultrasound wave as it transfers momentum through absorption and scattering. Because it produces a small mechanical push or displacement of the medium, radiation force is one proposed direct mechanism of ultrasonic neuromodulation — deforming membranes or gating mechanosensitive channels — and it is the physical basis of shear-wave elastography and of the acoustic tweezing and trapping used to position particles or motes.

Radiation force scales with acoustic intensity and tissue absorption and points along the beam, distinguishing it from oscillatory pressure effects and from heating. Whether the micrometre-scale displacements it produces are sufficient to gate neuronal channels at therapeutic intensities is an open, actively debated quantitative question.