Modeling of ultrasound contrast agents

Abstract

Ultrasound contrast agents differ from free-gas bubbles such that a polymer, lipid, or fluid shell encapsulates them. Many modeling efforts have focused on the role of the shell on the overall dynamics. Early efforts used semiempirical approaches to incorporate the shell into a generalized Rayleigh–Plesset equation. Church [J. Acoust. Soc. Am. 97(3) (1995)] developed a more rigorous approach modeling the albumin shell of Albunex as a linear elastic material. This work has provided the foundation for many subsequent theoretical and experimental efforts. Ye [J. Acoust. Soc. Am. 100(3) (1996)] examined modal scattering solutions for an Albunex agent. Recent efforts to design a high-frequency contrast agent based on dipole scattering are discussed [Allen, Kruse, and Ferrara, IEEE-Trans. Ultrason. Ferroelectr. Freq. Control, in press]. The modeling of different types of shell materials remains an outstanding issue. The potential role of both viscous and viscoelastic shell materials is outlined. Furthermore, the limitations of linear elastic and viscoelastic material models are highlighted. The modeling of possible interaction effects among groups of contrast agents has received less attention. Also, outstanding issues exist with respect to a rigorous mathematical modeling of contrast agent destruction, drug delivery schemes, and potential bioeffects.