Bubble translation and deformation induced by ultrasound radiation force

Measurement of small‐bubble dynamics has been proposed for the remote evaluation of tissue elasticity [Erpelding et al., Proc. IEEE Ultrasonics Symp., 554–557, 2003]. For example, a microbubble can be produced within the cornea during femtosecond laser surgery and its response to a pulsed ultrasonic radiation force can be measured. The bubble’s translation, deformation, and oscillation can be directly related to the mechanical properties of surrounding tissue information that is required for optimization of the surgical procedure. In the work reported here, a model was developed to predict the translation and deformation of an initially spherical bubble in a soft viscoelastic medium as induced by radiation pressure. The extent of bubble translation and deformation is dictated by the elastic stress and viscous forces that oppose the radiation pressure. Numerical simulations predict static, periodic, and transient translation of the bubble in response to continuous, periodic, and pulsed waveforms, respectively. The model also predicts the deformation of the bubble. The results indicate increased deformations with increased bubble translations. Overall, the model can be used to determine the local shear modulus and viscosity of the medium based on measurements of gas‐bubble displacement. [Work supported by ARL:UT IR&D.]