title: "Compression-only" behavior: a second-order nonlinear response of ultrasound contrast agent microbubbles.
abstract: Oscillating phospholipid-coated ultrasound contrast agent microbubbles display a so-called "compression-only" behavior, where it is observed that the bubbles compress efficiently while their expansion is suppressed. Here, a theoretical understanding of the source of this nonlinear behavior is provided through a weakly nonlinear analysis of the shell buckling model proposed by Marmottant et al. [J. Acoust. Soc. Am. 118, 3499-3505 (2005)]. It is shown that the radial dynamics of the bubble can be considered as a superposition of a linear response at the fundamental driving frequency and a second-order nonlinear low-frequency response that describes the negative offset of the mean bubble radius. The analytical solution deduced from the weakly nonlinear analysis shows that the compression-only behavior results from a rapid change of the shell elasticity with bubble radius. In addition, the radial dynamics of single phospholipid-coated microbubbles was recorded as a function of both the amplitude and the frequency of the driving pressure pulse. The comparison between the experimental data and the theory shows that the magnitude of compression-only behavior is mainly determined by the initial phospholipids concentration on the bubble surface, which slightly varies from bubble to bubble.
authors.affiliation: Physics of Fluids Group, MIRA Institute of Biomedical Engineering and Technical Medicine, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Sijl
authors.forename: Marlies
authors.initials: M
authors.lastname: Overvelde
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dollet
authors.forename: Valeria
authors.initials: V
authors.lastname: Garbin
authors.forename: Nico
authors.initials: N
authors.lastname: de Jong
authors.forename: Detlef
authors.initials: D
authors.lastname: Lohse
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis
mesh_terms: D000162:Acoustics; D019245:Compressive Strength; D004548:Elasticity; D006801:Humans; D045423:Microbubbles; D008954:Models, Biological; D017711:Nonlinear Dynamics; D010743:Phospholipids / Q000737:chemistry; D013500:Surface Tension; D014463:Ultrasonography / Q000379:methods*
chemical_list: D010743:Phospholipids