Nonlinear Dynamics Of Lipid-shelled Ultrasound
Microbubble Contrast Agents
Author(s)
A. A. Doinikov & P. A. Dayton
Abstract
Encapsulated gas microbubbles, known as contrast agents, are widely used in
ultrasound medical applications. The present study is devoted to modelling of the
spatio-temporal dynamics of lipid-shelled contrast agents. A theoretical model is
proposed that describes the radial and translational motion of a lipid-shelled
microbubble in an ultrasound field. The model approximates the behaviour of the
lipid shell by the linear 3-constant Oldroyd constitutive equation, incorporates
the translational motion of the bubble, and accounts for acoustic radiation losses
due to the compressibility of the surrounding liquid. The values of the shell
parameters appearing in the model are evaluated by fitting simulated radius-time
curves to experimental ones. The results are then used for the simulation of the
translational motion of contrast agent bubbles of various radii and the evaluation
of the relationship between equilibrium radii of lipid-shelled agents and their
resonance frequencies in the regime of nonlinear oscillation.
Keywords: contrast agents, encapsulated bubbles, lipid shell, ultrasound, radial
oscillation, translational motion, resonance frequencies.
1 Introduction
Ultrasound contrast agents are micron-sized encapsulated gas bubbles which are
produced by pharmaceutical companies for medical ultrasound applications [1].
They are normally injected into the bloodstream of the patient in order to
increase blood-tissue contrast during an ultrasonic examination and thereby to
improve the quality of ultrasonic images. Contrast agents are also used in
targeted imaging and ultrasound-assisted localized drug delivery [2, 3]. Targeted
agents are taken up by specific tissues or adhere to specific sites in the body.
Keywords
contrast agents, encapsulated bubbles, lipid shell, ultrasound, radial
oscillation, translational motion, resonance frequencies.
Related Book
Other papers in this volume
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