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Surfactant stabilized microbubbles are widely used clinical contrast agents for ultrasound imaging. In this work, the light propagation through a turbid medium in the presence of microbubbles has been investigated. Through a series of experiments, it has been found that the optical attenuation is increased when the microbubbles in a turbid medium are insonified by ultrasound. Such microbubble enhanced optical attenuation is a function of both applied ultrasound pressure and microbubble concentration. To understand the mechanisms involved, a Monte Carlo (MC) model has been developed. Under ultrasound exposure, the sizes of microbubbles vary in space and time, and their dynamics are modeled by the Rayleigh-Plesset equation. By using Mie theory, the spatially and temporally varying optical scattering and scattering efficiency of microbubbles are determined based on the bubble sizes and internal refractive indices. The MC model is shown to effectively describe a medium with rapidly changing optical scattering, and the results are validated against both computational results using an N-layered diffusion equation model and experimental results using a clinical microbubble contrast agent (SonoVue®).

Original publication

DOI

10.1117/1.jbo.18.1.015002

Type

Journal article

Journal

Journal of biomedical optics

Publication Date

01/2013

Volume

18

Addresses

University College London, Department of Medical Physics & Bioengineering, Malet Place Engineering Building, Gower Street, London, WC1E 6BT, United Kingdom. t.leung@ucl.ac.uk

Keywords

Contrast Media, Surface-Active Agents, Spectroscopy, Near-Infrared, Ultrasonography, Monte Carlo Method, Reproducibility of Results, Microbubbles, Phantoms, Imaging, Diffusion, Photons, Light, Scattering, Radiation, Models, Theoretical, Computer Simulation, Optics and Photonics