ACOUSTIC MODELING OF SHELL-ENCAPSULATED GAS-BUBBLES

Existing theoretical models do not adequately describe the scatter and attenuation properties of the ultrasound contrast agents Quantison(TM ) and Myomap(TM). An adapted version of the Rayleigh-Plesset equation, in which the shell is described by a viscoelastic solid, is proposed and validated for these agents and Albunex(R), The acoustic transmissi on and scattering are measured in the frequency band from 1-10 MHz, Th e measured transmission is used to estimate two parameters, the effect ive bulk modulus, K-eff, describing the elasticity, and the friction p arameter, S-F, describing the viscosity of the shell. For the scatteri ng, the difference between measurements and calculations is < 3 dB, Fo r Quantison(TM), the effective bulk modulus is independent of the bubb le diameter. For Albunex(R), it increases for decreasing bubble diamet er. The nonlinear response of Quantison(TM) is minimal for acoustic pr essures up to 200 kPa, For acoustic pressures above 200 kPa, the measu red scattering abruptly increases. This increase reaches a level of 20 dB for an acoustic pressure of 1.8 MPa, This response cannot be predi cted by the theoretical model developed in this article. (C) 1998 Worl d Federation for Ultrasound in Medicine & Biology.