# Response of bubbles to diagnotic ultrasound:a unifying theoretical approach

Sascha Hilgenfeldt, Detlef Lohse, M. Zomack

Research output: Contribution to journalArticleAcademicpeer-review

95 Citations (Scopus)
The scattering of ultrasound from bubbles of $\sim 1~\mu$m radius, such as used in contrast enhancers for ultrasound diagnostics, is studied. We show that sound scattering and active'' emission of sound from oscillating bubbles are not contradictory, but are just two different aspects derived from the same physics. Treating the bubble as a nonlinear oscillator, we arrive at general formulas for scattering and absorption cross-sections. We show that several well-known formulas are recovered in the linear limit of this ansatz. In the case of strongly nonlinear oscillations, however, the cross-sections can be larger than those for linear response by several orders of magnitude. The major part of the incident sound energy is then converted into emitted sound, unlike what happens in the linear case, where the absorption cross-sections exceed the scattering cross-sections.