Sound scattering and localized heat deposition of pulse-driven microbubbles

Hilgenfeldt, Sascha; Lohse, Detlef; Zomack, Michael

doi:10.1121/1.429438

Cited by 83 publications

(75 citation statements)

References 33 publications

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“…Such activity can be exploited to visualize ablation effects (Sanghvi et al 1995;Rabkin et al 2005Rabkin et al , 2006 or to enhance tissue absorption (Melodelima et al 2001;Sokka et al 2003;Umemura et al 2005;Kaneko et al 2005), but can also complicate ultrasound energy deposition and the resulting spatial pattern of tissue coagulation (Watkin et al 1996;Chen et al 2003;Makin et al 2005;. Mechanisms for interactions between cavitation activity and ultrasound-induced heating have been clarified by several detailed numerical modeling studies (Hilgenfeldt et al 2000;Chavrier et al 2000;Yang et al 2004) and phantom experiments (Holt and Roy 2001;Khokhlova et al 2006). Cavitation activity, measured by passive detection of acoustic emissions, has also been found to correlate with cellular-level bioeffects (Edmonds and Ross 1986;Hallow et al 2006) and with ultrasound enhancement of thrombolysis (Datta et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emissions During 3.1 MHz Ultrasound Bulk Ablation In Vitro

Mast

Salgaonkar

Karunakaran

et al. 2008

Ultrasound in Medicine & Biology

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Acoustic emissions associated with cavitation and other bubble activity have previously been observed during ultrasound ablation experiments. Since detectable bubble activity may be related to temperature, tissue state, and sonication characteristics, these acoustic emissions are potentially useful for monitoring and control of ultrasound ablation. To investigate these relationships, ultrasound ablation experiments were performed with simultaneous measurements of acoustic emissions, tissue echogenicity, and tissue temperature, on fresh bovine liver. Ex vivo tissue was exposed to 0.9-3.3 s bursts of unfocused, continuous-wave, 3.10 MHz ultrasound from a miniaturized 32-element array, which performed B-scan imaging with the same piezoelectric elements during brief quiescent periods. Exposures employed pressure amplitudes of 0.8-1.4 MPa for exposure times of 6-20 min, sufficient to achieve significant thermal coagulation in all cases. Acoustic emissions received by a 1 MHz, unfocused passive cavitation detector, beamformed Aline signals acquired by the array, and tissue temperature detected by a needle thermocouple were sampled 0.3-1.1 times per second. Tissue echogenicity was quantified by the backscattered echo energy from a fixed region of interest within the treated zone. Acoustic emission levels were quantified from the spectra of signals measured by the passive cavitation detector, including subharmonic signal components at 1.55 MHz, broadband signal components within the band 0.3-1.1 MHz, and low-frequency components within the band 10-30 kHz. Tissue ablation rates, defined as the thermally ablated volumes per unit time, were assessed by quantitative analysis of digitally imaged, macroscopic tissue sections. Correlation analysis was performed among the averaged and time-dependent acoustic emissions in each band considered, B-mode tissue echogenicity, tissue temperature, and ablation rate. Ablation rate correlated significantly with broadband and low-frequency emissions, but was uncorrelated with subharmonic emissions. Subharmonic emissions were found to depend strongly on temperature in a nonlinear manner, with significant emissions occurring within different temperature ranges for each sonication amplitude. These results suggest potential roles for passive detection of acoustic emissions in guidance and control of bulk ultrasound ablation treatments.

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Section: Introductionmentioning

confidence: 99%

Acoustic Emissions During 3.1 MHz Ultrasound Bulk Ablation In Vitro

Mast

Salgaonkar

Karunakaran

et al. 2008

Ultrasound in Medicine & Biology

View full text Add to dashboard Cite

show abstract

“…Even though this section deals with non-thermal mechanisms, UCAs can have an effect on bulk tissue heating (Hilgenfeldt et al, 1998(Hilgenfeldt et al, ,2000Chavrier and Chapelon, 2000;Holt and Roy, 2001;Sokka et al, 2003;Umemura et al, 2005). Typically, there is at least a 2-4 times enhancement of tissue heating by cavitation, or, if the bioeffect were a lesion, the lesion volume was likewise enhanced.…”

Section: Cavitation With Injected Microbubblesmentioning

confidence: 99%

Ultrasound–biophysics mechanisms

O’Brien

2007

Progress in Biophysics and Molecular Biology

609

416

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Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and nonthermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials. Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns.

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“…The nonlinearity of bubble dynamics and the violent collapses help to increase the bubble response and imprint a distinctive signature onto the emitted sound, making it easier to distinguish bubble echoes from unwanted tissue reflections (de Jong and Hoff, 1993;Hilgenfeldt, Lohse, and Zomack, 1998;Frinking et al, 1999). Yet even here the potential for various kinds of ''cavitation damage'' has to be carefully assessed: mechanical damage to living tissue (Barnett, 1986), thermal hazard from the absorption of high-frequency sound in tissue and blood (Wu, 1998;Hilgenfeldt et al, 2000), or chemical hazard from the sonochemical production of radicals inside the body (Barnett, 1986).…”

Section: Other Applications Of Bubble Dynamics and Cavitationmentioning

confidence: 99%

Single-bubble sonoluminescence

2002

Self Cite

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Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small amounts of trace noble gases or other impurities can dramatically change the amount of light emission, which is also affected by small changes in other operating parameters (mainly forcing pressure, dissolved gas concentration, and liquid temperature). This article reviews experimental and theoretical efforts to understand this phenomenon. The currently available information favors a description of sonoluminescence caused by adiabatic heating of the bubble at collapse, leading to partial ionization of the gas inside the bubble and to thermal emission such as bremsstrahlung. After a brief historical review, the authors survey the major areas of research: Section II describes the classical theory of bubble dynamics, as developed by Rayleigh, Plesset, Prosperetti, and others, while Sec. III describes research on the gas dynamics inside the bubble. Shock waves inside the bubble do not seem to play a prominent role in the process. Section IV discusses the hydrodynamic and chemical stability of the bubble. Stable single-bubble sonoluminescence requires that the bubble be shape stable and diffusively stable, and, together with an energy focusing condition, this fixes the parameter space where light emission occurs. Section V describes experiments and models addressing the origin of the light emission. The final section presents an overview of what is known, and outlines some directions for future research. CONTENTS

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Sound scattering and localized heat deposition of pulse-driven microbubbles

Cited by 83 publications

References 33 publications

Acoustic Emissions During 3.1 MHz Ultrasound Bulk Ablation In Vitro

Acoustic Emissions During 3.1 MHz Ultrasound Bulk Ablation In Vitro

Ultrasound–biophysics mechanisms

Single-bubble sonoluminescence

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