Acoustic Radiation Force On A Sphere In Tissue

A theory is presented for the acoustic radiation force on a sphere embedded in a soft elastic medium that possesses a shear modulus several orders of magnitude smaller than its bulk modulus. Scattering of both compressional and shear waves is taken into account. There is no restriction on the size of the sphere or, apart from symmetry about an axis passing through the center of the sphere, the form of the incident compressional wave. If the medium is a liquid and the sphere is small in comparison with a wavelength the result reduces to the classical theory developed by Gor'kov [1] and others. The effect of shear elasticity on the radiation force is discussed in the context of parameters relevant to a gas bubble in tissue.