Oscillations of polymeric microbubbles: Effect of the encapsulating shell

Hoff, Lars; Sontum, Per Christian; Hovem, Jens M.

doi:10.1121/1.428557

Cited by 389 publications

(413 citation statements)

References 25 publications

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“…At the level of basic physics research, efforts are concentrated in determining through experimentation and mathematical modeling the scattering properties and the bubble dynamics of the different kinds of UCAs, which differ for properties such as encapsulating shell, gas, and size distribution (de Jong and Hoff 1993;Guan and Matula 2004;Lo et al 2006;Marsh et al 1999;May et al 2002). A number of models have been proposed to describe the bubble dynamics in the presence of a shell, which are a modification of the free bubble equation, such as the Rayleigh-Plesset equation or the Gilmore equations, to include the shell properties Chatterjee and Sasaki 2003;Church 1995;Hoff et al 2000;Khismatullin and Nadim 2002).…”

Section: Introductionmentioning

confidence: 99%

Cavitation Threshold of Microbubbles in Gel Tunnels by Focused Ultrasound

Sassaroli

Hynynen

2007

Ultrasound in Medicine & Biology

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The investigation of inertial cavitation in micro-tunnels has significant implications for the development of therapeutic applications of ultrasound such as ultrasound-mediated drug and gene delivery. The threshold for inertial cavitation was investigated using a passive cavitation detector with a center frequency of 1 MHz. Micro-tunnels of various diameters (90 to 800 μm) embedded in gel were fabricated and injected with a solution of Optison™ contrast agent of concentrations 1.2% and 0.2% diluted in water. An ultrasound pulse of duration 500 ms and center frequency 1.736 MHz was used to insonate the microbubbles. The acoustic pressure was increased at one second intervals until broadband noise emission was detected. The pressure threshold at which broadband noise emission was observed was found to be dependent on the diameter of the micro-tunnels, with an average increase of 1.2 to 1.5 between the smallest and the largest tunnels, depending on the microbubble concentration. The evaluation of inertial cavitation in gel tunnels rather than tubes provides a novel opportunity to investigate microbubble collapse in a situation that simulates in vivo blood vessels better than tubes with solid walls do.

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Section: Introductionmentioning

confidence: 99%

Cavitation Threshold of Microbubbles in Gel Tunnels by Focused Ultrasound

Sassaroli

Hynynen

2007

Ultrasound in Medicine & Biology

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“…[10][11][12] High-speed micrography has been used to study microbubble radial oscillation, 13 translation, 14 and fragmentation. 15 In these studies, a microbubble is assumed to remain spherical and in an infinite medium.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric oscillation of adherent targeted ultrasound contrast agents

Zhao¹,

Ferrara²,

Dayton³

2005

Appl. Phys. Lett.

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With a lipid shell containing biotin, micron-sized bubbles bound to avidin on a porous and flexible cellulose boundary were insonified by ultrasound. The oscillation of these targeted microbubbles was observed by high-speed photography and compared to the oscillation of free-floating microbubbles. Adherent microbubbles were observed to oscillate asymmetrically in the plane normal to the boundary, and nearly symmetrically in the plane parallel to the boundary, with a significantly smaller maximum expansion in each dimension for bound than free bubbles. With sufficient transmitted pressure, a jet was produced traveling toward the boundary.There is a great interest in developing molecularly targeted ultrasound contrast agents due to the potential medical applications. [1][2][3][4] The agents are gas bubbles with a diameter on the order of a few microns and a shell of albumin, lipid, or polymer. After intravenous injection, peptides or antibodies attached to the shells link the agents to a receptor on endothelial cells. Because of their high echogencity, these targeted agents can be detected by an ultrasound system with high sensitivity, and therefore can provide important information such as the spatial distribution and extent of tumor angiogenesis, 5,6 inflammatory response, 7,8 or thrombus. 9 Current contrast imaging schemes are not yet optimized for imaging these targeted agents because the microbubbles retained in tissue are limited in number, 5,9 and the signal from adherent microbubbles can be masked by the signal from freely circulating microbubbles. Strategies for imaging these agents currently require waiting for clearance of free-floating microbubbles or employing image averaging and subtraction techniques. Neither of these techniques is optimal since they require either a time delay, or multiple frames, which impede real-time imaging. Hence, there is a need for the development of a new selective and sensitive method for detecting adherent microbubbles, which will depend on our understanding of the acoustic behavior of a targeted microbubble after it binds to a targeting site.Mathematical simulations have been developed for modeling microbubble radial oscillation with different assumptions and simplifications. [10][11][12] High-speed micrography has been used to study microbubble radial oscillation, 13 translation, 14 and fragmentation. 15 In these studies, a microbubble is assumed to remain spherical and in an infinite medium. Asymmetrical oscillation of a cavitation bubble and formation of a jet have been studied both theoretically and experimentally by a number of research groups, [16][17][18] although previous experimental studies have involved unencapsulated bubbles of a diameter larger than micron-sized contrast agents, and have not used ultrasound as an excitation source. The behavior of a targeted microbubble after it binds to a vessel wall and is insonified by an ultrasound pulse has not been reported previously. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptIn...

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“…The commercially available contrast agents Sonovue R (Bracco), Definity (Lan- theus Medical Imaging) and Sonazoid (GE) consist of a monolayer of phospholipids with a thickness of a few nanometers. Various models account for a coating by assuming a viscoelastic thin shell, see for example [34], [35] and more recently [36]. The Rayleigh-Plesset type models account for the shell by an elastic term P elas and a viscous term P vis .…”

Section: Coated Bubblesmentioning

confidence: 99%

Ultrasound contrast agents : dynamics of coated bubbles

Overvelde¹

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Oscillations of polymeric microbubbles: Effect of the encapsulating shell

Cited by 389 publications

References 25 publications

Cavitation Threshold of Microbubbles in Gel Tunnels by Focused Ultrasound

Cavitation Threshold of Microbubbles in Gel Tunnels by Focused Ultrasound

Asymmetric oscillation of adherent targeted ultrasound contrast agents

Ultrasound contrast agents : dynamics of coated bubbles

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