Characterizations of the mathematical models of Ultrasound Contrast Agents: a review

Abstract

The typical contrast agents of ultrasound imaging composed of microbubbles of smaller than 7 µm in diameter this microbubbles consist of gas coated with a protein, lipid or polymer layer it is acting as very powerful scatterers.There are several models describe the dynamic behavior of these microbubbles under ultrasound filed, the Lord Rayleigh’s model is the oldest one and the basis for all other models, this model was modified by plesset by added the driving sound field, resulting in an equation called Rayleigh-Plesset equation which describes bubble oscillating due to the driving sound field in an inviscid and incompressible fluid of constant density, RP model is a second order nonlinear ODE, The RP equation may be modified by Noltingk, Neppiras and Poritsky Whose added the effects of the surrounding field , this led to an equation called the RPNNP equation which is considered the the first step to construct a shelled bubble model. Later researchs Take into account the liquid compressibility effect on the bubble dynamics, the major developments occurred in this area by Keller and Miksis. The microbubbles which used in such contrast agents are normally stabilized by a thin shell ,the stiffness and viscosity of this thin shell add a another foctors to the acoustical behavior of the bubble, several models exist for the encapsulating shell, the common models of encapsulated bubble are Hoff model and Marmottant Model, these models are an extension of the RP equation. Understanding the behavior of the microbubbles under ultrasound filed gives us a good tool to predict it’s dynamic motion, which help in designing a new and good contrast agent. In this article we review the linear and non-linear behavior of the microbubbles and its mathematical models