Acoustic Cavitation Threshold Research Articles

Development of a tomographic cavitation sensor for quality assessment of clinical high intensity focused ultrasound systems.

High‐intensity focused ultrasound (HIFU) fields are known to nucleate and excite inertial and noninertial cavitation in tissue and tissue‐mimicking materials once a threshold negative acoustic pressure is reached. In the context of ablative HIFU treatment, inertial cavitation has been correlated with significantly enhanced rates of heating, while in histotripsy, cavitation is the very mechanism that causes tissue damage. Characterizing the extent of the cavitation region produced by clinical HIFU devices is therefore important to ensure safe, efficient, and effective treatment. A novel, multielement sensor is being developed to enable accurate axial and radial mapping of the cavitation region during HIFU exposure by passive detection and tomographic reconstruction of the broadband emissions arising from bubble collapse. Computational modeling has shown that the application of a cross‐correlation algorithm to simulated received signals has the potential to localise individual sources of emissions with submillimeter accuracy. Initial experimental validation of models has been conducted using a prototype device developed in collaboration with the National Physical Laboratory. Future work will involve the refinement of the sensor design and reconstruction algorithm to improve spatiotemporal resolution, along with the development of a tissue mimicking material which matches the acoustic properties and cavitation threshold of real tissue.

Dynamic adsorption properties of n-alkyl glucopyranosides determine their ability to inhibit cytolysis mediated by acoustic cavitation.

Suspensions of human leukemia (HL-60) cells readily undergo cytolysis when exposed to ultrasound above the acoustic cavitation threshold. However, n-alkyl glucopyranosides (hexyl, heptyl, and octyl) completely inhibit ultrasound-induced (1057 kHz) cytolysis (Sostaric, et al. Free Radical Biol. Med. 2005, 39, 1539-1548). The efficacy of protection from ultrasound-induced cytolysis was determined by the n-alkyl chain length of the glucopyranosides, indicating that protection efficacy depended on adsorption of n-alkyl glucopyranosides to the gas/solution interface of cavitation bubbles and/or the lipid membrane of cells. The current study tests the hypothesis that "sonoprotection" (i.e., protection of cells from ultrasound-induced cytolysis) in vitro depends on the adsorption of glucopyranosides at the gas/solution interface of cavitation bubbles. To test this hypothesis, the effect of ultrasound frequency (from 42 kHz to 1 MHz) on the ability of a homologous series of n-alkyl glucopyranosides to protect cells from ultrasound-induced cytolysis was investigated. It is expected that ultrasound frequency will affect sonoprotection ability since the nature of the cavitation bubble field will change. This will affect the relative importance of the possible mechanisms for ultrasound-induced cytolysis. Additionally, ultrasound frequency will affect the lifetime and rate of change of the surface area of cavitation bubbles, hence the dynamically controlled adsorption of glucopyranosides to their surface. The data support the hypothesis that sonoprotection efficiency depends on the ability of glucopyranosides to adsorb at the gas/solution interface of cavitation bubbles.

Thermodynamic and kinetic considerations of nucleation and stabilization of acoustic cavitation bubbles in water

Qualitative explanation for a homogeneous nucleation of acoustic cavitation bubbles in the incompressible liquid water with simple phenomenological approach has been provided via the concept of the desorbtion of the dissolved gas and the vaporization of local liquid molecules. The liquid medium has been viewed as an ensemble of lattice structures. Validity of the lattice structure approach against the Brownian motion of molecules in the liquid state has been discussed. Criterion based on probability for nucleus formation has been defined for the vaporization of local liquid molecules. Energy need for the enthalpy of vaporization has been considered as an energy criterion for the formation of a vaporous nucleus. Sound energy, thermal energy of the liquid bulk (Joule–Thomson effect) and free energy of activation, which is associated with water molecules in the liquid state (Brownian motion) as per the modified Eyring’s kinetic theory of liquid are considered as possible sources for the enthalpy of vaporization of water molecules forming a single unit lattice. The classical nucleation theory has then been considered for expressing further growth of the vaporous nucleus against the surface energy barrier. Effect of liquid property (temperature), and effect of an acoustic parameter (frequency) on an acoustic cavitation threshold pressure have been discussed. Kinetics of nucleation has been considered.

Modeling the inertial cavitation threshold for tissue-mimicking gels seeded with laser-irradiated gold nanoparticle nuclei

Previous experiments demonstrated the acoustic cavitation threshold in a tissue-mimicking phantom was lowered from 4.5 to 1 MPa by seeding the optically transparent phantom with light-absorptive gold nanoparticles and irradiating these absorbers with ns-pulsed laser light with radiant exposure less than 10 mJ/cm2. The absorption of laser energy deposits a remarkable amount of heat into the particle and surrounding liquid. Under appropriate acoustic conditions, explosive vaporization occurs and the resultant vapor cavity expands many times its initial size and collapses inertially. A three-stage model is developed to account for prenucleation heating, nucleation and formation of the vapor cavity, and follow-up vapor bubble dynamics. The acoustic pressure and laser-radiant exposure thresholds are determined by examining the radius-time evolution of the cavity. The acoustic threshold decreases when laser exposure increases but the efficiency of light depends on its pulse length and the particle size. A strategy for choosing optimal particles to generate inertial cavitation with acoustic and optic energy inputs is suggested. [Work supported by the Dept. of the Army (Award No. DAMD17-02-2-0014) and the Center for Subsurface Sensing and Imaging Systems (NSF ERC Award No. EEC-9986821).]

Acoustic Cavitation Thresholds of Sea Water in Different Regions of the World Ocean

Results of experimental measurements of acoustic cavitation thresholds are presented for the waters of the Atlantic Ocean, Pacific Ocean, Indian Ocean, Arctic Ocean, and some other parts of the World Ocean, including the Arabian Sea, Baltic Sea, East Siberian Sea, North Sea, Philippine Sea, Black Sea, Sea of Japan, Sea of Okhotsk, and South China Sea. The measurements were carried out by many oceanic expeditions between 1963 and 1987. General laws governing the variations in the cavitation strength of sea water over the World Ocean are revealed.

Detecting large particles in a slurry by measuring acoustic cavitation thresholds

Acoustic microcavitation is used to detect particles in liquids and suspensions. The observation that an acoustic cavitation threshold is characteristic of particle size is exploited to develop a solution for an important problem facing chemical mechanical planarization of silicon wafers. Specifically, it is established via experiments that a sparse presence of large particles in a nanofine slurry can be detected acoustically. Being able to detect such large particles prior to chemical mechanical planarization polishing is expected to save the wafers from being scratched during planarization. The acoustic method is entirely noninvasive.

Acoustic cavitation thresholds and stable oscillations of vapor-gas bubbles

The effect of rectified diffusion on the behavior of gas bubbles and the effect of rectified heat transfer to vapor bubbles are well established. These effects may be equally important for dynamics of vapor-gas bubbles and control the acoustic cavitation thresholds. To describe these effects a model of a spherical vapor-gas bubble is used. This model accounts for heat and mass transfer in the two-component system, including Soret–Dufour effects, kinetics of evaporation, surface tension, liquid viscosity, and compressibility. Equations for acoustic cavitation thresholds and stable bubble oscillations are obtained using asymptotic averaging techniques valid to second order in the amplitude of the acoustic field. Good agreement between the previous results for gas and vapor cavitation thresholds and the present computations is observed in the limiting cases of single-component bubbles. The effects of temperature, kinetics of evaporation, supersaturation, and others on the acoustic cavitation thresholds and stable bubble oscillations are studied and discussed. The existence of stable oscillations and cavitation thresholds of the bubble due to the second resonance of a vapor-gas bubble is predicted. These states occur due to the two-component nature of the bubble and appear at low inert gas concentrations near the liquid boiling point.

Xanthene dyes for reducing acoustic cavitation threshold in aqueous solution

The effect of xanthene dyes on the acoustic cavitation threshold in an aqueous solution was investigated in a progressive wave field. Among fluorescein and its halogenated derivatives, rose bengal (RB), phloxin B (PB), erythrosin B (EB) and tetrachlorofluorescein (TCF) were found to reduce the intensity threshold for inducing cavitation which accompanies subharmonic emission. In phosphate buffer saline, subharmonic emission in the presence of RB or PB was observed at an acoustic intensity more than five times lower than the acoustic intensity in their absence. When iodide ions were also present in the solution, their oxidation proceeded with the subharmonic emission. This indicates that xanthene dyes reduced the threshold for sonochemically active cavitation. The ability of xanthene dyes to reduce the cavitation threshold did not significantly correlate with their surface tension and viscosity, but strongly correlated with their ability to stabilize foams.

Acoustic cavitation thresholds in NaCl-water solutions

L'emission acoustique de subharmonique 1/2 et de lumiere dans les solutions aqueuses de NaCl a ete etudiee par la technique de la cavitation ultrasonique a impulsions en fonction de la concentration. Les resultats experimentaux concernant les seuils du bruit et de lumiere sont analyses pour expliquer l'influence de la concentration du sel.

Theoretical estimation of the cavitation threshold for very short pulses of ultrasound

Theoretical predictions of the dependence of the ultrasonic cavitation threshold on acoustic frequency, pulse length and liquid shear viscosity are presented. The calculations are based on numerical modelling of oscillations of an isolated gas-filled bubble in a liquid. The polytropic approximation is used. No restraints are imposed on the bubble size distribution. The results presented are considered to indicate the lowest limit of acoustic cavitation threshold for sonoluminescence and related phenomena.

The past, present, and future of acoustic cavitation nucleation

Those familiar with the field do not need to be reminded that acoustic cavitation is the cornerstone of sonoluminescence and sonochemistry. However, an equally important and often overlooked statement is that nucleation is the cornerstone of acoustic cavitation. So critical is the nature of the nucleus to the cavitation process that the acoustic cavitation threshold in water can be varied from a few atmospheres to a few hundred atmospheres just by altering the distribution and properties of the nuclei. (The acoustic cavitation threshold is the maximum acoustic pressure amplitude to which a liquid can be exposed before cavitation inception.) The fundamentals of acoustic cavitation nucleation will be presented in this paper, which is intended to be tutorial in nature. Topics include homogeneous and heterogeneous nucleation, stabilization mechanisms, models of heterogeneous cavitation nuclei, and the dependence of the cavitation threshold on the properties of the nucleus. [Work supported by ONR and the NPS Res. Program]

Cavitation threshold measurements for microsecond length pulses of ultrasound.

The acoustic cavitation threshold of an aqueous solution has been measured at megahertz frequencies as a function of pulse width and pulse repetition frequency for various combinations of these quantities. The fluid tested was a 0.1M KOH-H3BO3 buffer solution with pH 10.9, which contained luminol, was saturated with argon, and filtered to 25 mu. The presence of cavitation was detected by a photomultiplier tube that required the emission of visible light that was both larger in magnitude and longer in duration than a preset criterion. It was observed that the cavitation threshold of water under pulse conditions decreases both when the pulse width is fixed and the pulse repetition frequency is increased, and when the pulse repetition frequency is fixed and the pulse width is increased. Acoustic cavitation thresholds measured in aqueous solutions are significantly less than those acoustic pressures associated with instruments that are currently in widespread use in medicine.

A precise technique for the measurement of acoustic cavitation thresholds and some preliminary results.

A description is given of a precise technique for measuring the threshold for acoustic cavitation inception. The system, which is automated so as to remove operator involvement, utilizes a slow ramping of the acoustic pressure amplitude until cavitation occurs. The detection criterion is the generation of a sufficiently intense sonoluminescent signal. Measurements made in filtered water show a well-defined, reproducible, and stable cavitation threshold. Measurements of the dependence of the threshold on filter size, on time, and on the concentration of dissolved ions for various salts are also presented. Many of these results appear anomalous.

The influence of the dissolved ion concentration on the acoustic cavitation threshold of water

The variation in the transient acoustic cavitation threshold of water was measured as a function of the dissolved ion concentration of various salts. The measurements were made with a resonant sphere system in which solid particle size, water temperature, and dissolved gas content could be controlled within a closed circulating system. The normal criterion used for a cavitation event was the detection, by a photomultiplier tube, of sonoluminescence produced by a collapsing cavity. Water with a specific conductance of about 1 μS cm−1 was assigned zero concentration for the first data point. Measurements were then made at successively higher concentrations, up to 10 mmoles 1−1. The salts were chosen to check and extend the measurements of a previous researcher [V. A. Akulichev, Sov. Phys. Acoust. 12, 144–149 (1966)], who first detected a dependence of the cavitation threshold on dissolved ion concentration. The results of our measurements show that the threshold increases with ion concentration, reaching saturation at concentrations of 2 mmoles 1−1 or less. This dependence is in the opposite direction to that observed by Akulichev. Our results will be analyzed with regard to the standard models of cavitation nucleation. [Work supported in part by the Office of Naval Research and the National Science Foundation.]

Effect of Dilute Polymer Additives on the Acoustic Cavitation Threshold of Water

Measurements are presented of the variation of the acoustic cavitation threshold of water with concentration of the polymer additives polyethylene oxide and guar gum. It was found that small amounts of these additives could significantly increase the cavitation threshold. A theoretical model, based upon nucleation of a gas bubble from a Harvey-type crevice in a mote or solid particle, is developed that gives good agreement with the measurements. The applicability of this approach to an explanation of cavitation index reduction in flow-generated or confined jet cavitation, when polymer additives are introduced, is discussed.

Acoustic Cavitation Studies

Abstract : The primary thrust of this study was toward a more complete understanding of general aspects of acoustic cavitation. The effect of long- chain polymer additives on the cavitation threshold was investigated to determine if they reduced the acoustic cavitation threshold in a similar manner to the observed reduction in the cavitation index in hydrodynamic cavitation. Measurements were made of the acoustic cavitation threshold as a function of polymer concentration for additives such as guar gum and polyethelene oxide. The measurements were also made as a function of dissolved gas concentration, surface tension and viscosity. It was determined that there was a significant increase in the acoustic cavitation threshold for increased concentrations of the polymer additives (measurable effects could be obtained for concentrations as low as a few parts per million). One would normally expect that an additive that reduces surface tension to decrease the pressure required to cause a cavity to grow and thus these additives, at first thought, should reduce the threshold. However, even in the hydrodynamic case, the threshold was increased. In both of the hydrodynamic cases considered, the explanation for the increased threshold was given 'in terms of changed fluid dynamics rather than changed physical properties of the fluid.

The effect of polymer additives on cavitation inception in water

Measurements are presented of the variation of the acoustic cavitation threshold of water with concentration of the polymer additives polyethylene oxide and guar gum. It was found that small amounts of these additives could significantly increase the cavitation threshold. A theoretical model, based upon nucleation of a gas bubble from a Harvey‐type crevice in a mote or solid particle, is developed that gives good agreement with the measurements. The applicability of this approach to an explanation of cavitation index reduction in flow‐generated or confined jet cavitation, when polymer additives are introduced, is discussed. [Work supported in part by the ONR and the NSF.]

Acoustic cavitation thresholds and cyclic processes

There is currently renewed interest in cavitation thresholds in connection with industrial and medical applications of ultrasound. This paper is a review of the theory relating to thresholds. In particular, it shows how these thresholds can be located using simple approximate formulae. The paper also examines a number of interesting cyclic processes that take place around the thresholds. The paper is an expanded form of recent seminars.

Tensile strength of water

THE measured tensile strength of water has long been known to be significantly less than theoretical predictions and the reduced strength is normally attributed to the presence of solid impurities that serve as nucleation sites for rupture of the liquid1. A favourite method of measuring tensile strength is through the dynamic stressing of a liquid by an acoustic field. At sufficiently large values of the peak negative acoustic-pressure amplitude the liquid ruptures and forms a rapidly growing vapour cavity that collapses violently during the positive portion of the cycle. This cavity collapse is normally violent enough to be observed easily with the unaided eye or ear. Such an event is termed the acoustic cavitation threshold and is a measure of the tensile strength of a liquid. Although some successes have been obtained in achieving measured values of the tensile strength comparable to theoretical predictions for extremely small samples2 or after extensive filtration3, I know of no current theory for the prediction of values of the dynamic tensile strength for ordinary distilled water. Using a modified version of a recent theory by Apfel4, an equation is presented here that correctly predicts the variation of the acoustic cavitation threshold of water with surface tension, dissolved gas content and temperature.

Investigation of acoustic cavitation thresholds by observation of the first subharmonic

The onset of acoustic cavitation has been studied using the first peak of subharmonic generation as an indicator of cavitation onset in the liquid. The findings are discussed in terms of the most satisfactory explanation of this subharmonic generation. The results of altering certain parameters of the liquid such as surface tension, viscosity, gas content and nucleation on subharmonic peak formation are given and commented on.