Ronald A. Roy

University of Oxford | OX · Department of Engineering Science

Noise characterization of cavitation has use in biomedicine, sonochemistry, and waste degradation. Typically, spectral features of the cavitation noise signals obtained through Fourier analysis are specific to the experimental set-up and are analyzed to classify the signals in terms of presumed domains of bubble behaviors. The objective of this res...

No PDF available ABSTRACT The use of high-intensity focused ultrasound (HIFU) to induce irreversible changes in tissue due to heating is well established. We have shown that changes in tissue optical properties (scattering and absorption coefficients) could be used as a proxy to improve sensing and imaging of HIFU lesion formation, as an alternativ...

No PDF available ABSTRACT Sonochemistry involves several steps. First, an acoustic wave must be generated with sufficient energy to nucleate cavitation. This cavitation event must then be energetic enough to produce radicals through the sonolysis of the gas or vapor molecules in the bubble. Finally, these radical species must survive long enough to...

No PDF available ABSTRACT Ultrasound-mediated DNA delivery (UDD) is a technique that utilizes ultrasound to aid the transfer of genetic materials into bacterial cells of interest (either in their planktonic or biofilm modes), resulting in new functionalities being displayed by the target microorganisms in-situ. The physical mechanism of UDD is poor...

No PDF available ABSTRACT When it comes to experimental research on acoustic cavitation, connecting the dots can be challenging. It requires that the researcher possesses good command of the essential facts associated with the medium, the sound field, and the relevant observable phenomena. This maxim is embodied in Robert Apfel's “Three Laws” of ca...

The ability to directly modify native and established biofilms has enormous potential in understanding microbial ecology and application of biofilm in 'real‐world' systems. However, efficient genetic transformation of established biofilms at any scale remains challenging. In this study, we applied an ultrasound‐mediated DNA delivery (UDD) technique...

Acoustic droplet vaporization (ADV) is an important process that enables the theragnostic application of acoustically activated droplets, where the nucleation of inertial cavitation (IC) activity must be precisely controlled. This Letter describes threshold pressure measurements for ADV and acoustic emissions consistent with IC activity of lipid-sh...

High-intensity focused ultrasound (HIFU) is often used to create lesions, or regions of tissue destruction due to heating and cavitation activity, most often in tumors or other diseased tissues. However, the acoustic properties of tissues denatured by heat are not very different from those of untreated tissue, making lesion detection and quantifica...

No PDF available ABSTRACT Heating of tissue by high-intensity focused ultrasound (HIFU) can result in sufficient temperature elevation to cause irreversible changes in the tissue structure. The contiguous volume occupied by these changes, a lesion, and the extent of the tissue changes may be quantified histologically or estimated through techniques...

Detection of inertial and stable cavitation is important for guiding high-intensity focused ultrasound (HIFU). Acoustic transducers can passively detect broadband noise from inertial cavitation and the scattering of HIFU harmonics from stable cavitation bubbles. Conventional approaches to cavitation noise diagnostics typically involve computing the...

As irreplaceable energy sources of minimally invasive treatment, light and sound have, separately, laid solid foundations in their clinic applications. Constrained by the relatively shallow penetration depth of light, photodynamic therapy (PDT) typically involves involves superficial targets such as shallow seated skin conditions, head and neck can...

The optical properties of tissue change during thermal ablation. Multi-modal methods such as acousto-optic (AO) and photo-acoustic (PA) imaging may provide a real-time, direct measure of lesion formation. Baseline changes in optical properties have been previously measured over limited ranges of thermal dose for tissues exposed to a temperature-con...

The safe utilization of controlled cavitation for HIFU therapy and ultrasound assisted drug delivery requires nucleation sites for bubble formation. We consider the potential for nucleating transient vapor cavities using laser-illuminated gold nanoparticles combined with high-intensity focused ultrasound. An transparent polyacrylamide gel phantom w...

The impact of a stainless steel disk-shaped projectile launched by a single-stage light gas gun is used to generate planar shock waves with amplitudes on the order of 10²MPa in a hydrogel target material. These shock waves are characterized using ultra-high-speed imaging as well as a fiber-optic probe hydrophone. Although the hydrogel equation of s...

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Baseline changes in optical properties have been previously measured as a function of thermal dose for chicken breast exposed to a temperature-controlled water bath (doi...

Acoustic backscatter from the seasurface is governed by the roughness of the surface and subsurface microbubble distributions. At low frequencies, scattering results primarily from coherent and/or collective scatter from bubbles entrained by the subsurface vorticity or carried to depth by Langmuir circulation and thermal convection. In 1947, Carste...

In biomedical, naval and oceanographic arenas, the acoustic characteristics of bubbly liquids have simultaneously confounded and been exploited by acoustic tools used in the respective fields. The work of Carstensen and Foldy [J. Acoust. Soc. Am. 19, 481-501 (1947)] served as a cornerstone of the post-World War II understanding of this system, but...

Real-time acousto-optic (AO) sensing has been shown to noninvasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. The technique is particularly appropriate for monitoring noncavitating lesions that offer minimal acoustic contrast. A numerical model is presented for an AO-guided HIFU...

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Baseline changes in optical properties have been previously measured as a function of thermal-dose for tissues exposed to a temperature-controlled water bath (doi:10.108...

Detection of inertial and stable cavitation is important for guiding high-intensity focused ultrasound (HIFU). Acoustic transducers can passively detect broadband noise from inertial cavitation and the scattering of HIFU harmonics from stable cavitation bubbles. Conventional approaches to separating these signals typically involve a custom comb-fil...

This study examines the effectiveness of the thermal dose model in accurately predicting thermally induced optical property changes of ex vivo chicken breast between 500–1100 nm. The absorption coefficient, μa, and the reduced scattering coefficient, , of samples are measured as a function of thermal dose over the range 50 °C–70 °C. Additionally, t...

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. The technique is particularly appropriate for monitoring non-cavitating lesions that offer minimal acoustic contrast. This work employs a modeling-based approach to impr...

One of Bill Carey's many scientific interests throughout his career was the acoustics of bubbly liquids. Many underwater acousticians know of Carey's work associated with bubble clouds and more recently, gas-bearing sediments, but Bill got his start with the subject earlier in his career, studying flow in a boiling water reactor while employed at A...

Bob Apfel passed away in 2002 after having taught at Yale University for over thirty years. During his tenure at Yale, Bob graduated 28 Ph.D. students, trained 12 post-doctoral students and influenced countless masters and undergraduate students. Bob devoted considerable time and effort to the Acoustical Society of America (his honors include the G...

The authors describe experimental work examining the collapse of a cavity by a strong shockwave. A millimeter size cavity is cast in Phytagel, which is then impacted by a metallic projectile accelerated by a compressed gas gun, reaching velocities up to 500 m/s. The impact generates a strong shockwave that propagates into the gel at greater than so...

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposures. Although proof-of-concept experiments have been successful, the underlying parameters and mechanisms affecting the AO detectability of HIFU lesion formation are not well...

The laser generation of vapor bubbles around plasmonic nanoparticles can be enhanced through the application of an ultrasound field; a technique referred to as photoacoustic cavitation. The combination of light and ultrasound allows for bubble formation at lower laser fluence and peak negative ultrasound pressure than can be achieved using either m...

Real-time acousto-optic (AO) sensing has been shown to non-invasively detect changes in tissue optical properties, a direct indicator of thermal damage, during high-intensity focused ultrasound (HIFU) therapy. In this work, a comprehensive model is developed to describe the AO sensing of lesion formation during HIFU therapy. The angular spectrum me...

LONG-TERM GOALS One research goal developed from conducted shallow water (SW) acoustic transmission experiments in sandy-silty areas [1] revealed a nonlinear power law frequency-dependent attenuation at lower frequencies (≤ 1 kHz) consistent with results reviewed in [2-4] and the observations by the ONR-HEP program. The Biot Theory [5] predicts tha...

Acousto-optic imaging is a hybrid imaging technique that exploits the interaction between light and sound to image optical contrast at depth in optically turbid media with the high spatial resolution of ultrasound. Quantitative measurement of optical properties using this technique is confounded by multiple parameters that influence the detected ac...

In an earlier work by Farny et al. [ARLO 6, 138-143 (2005).] it was demonstrated that the acoustic cavitation threshold in a tissue mimicking gel phantom can be lowered from 4.5 to ∼1 MPa by "seeding" the optically transparent phantom with light absorptive gold nanoparticles and irradiating these absorbers with nanosecond pulses of laser light at i...

Much of the research performed to study SBSL deals with the influence of external parameters (e.g., the host water temperature, the ambient pressure, the type and amount of dissolved gas in the liquid, to name a few) on the bubble dynamics and light emission. In the current paper, work carried out to study the influence of another external paramete...

Light-absorbing nanoparticles can be used to improve the signal-to-noise ratio of the thermoelastic emissions from tissue that are used in photoacoustic tomography (PAT) and microscopy (PAM). Nanoparticles can be functionalized to selectively target cancer cells and destroy them through the formation of vapour bubbles. It has been shown that heatin...

Transcranial ultrasound in combination with intravenously administered ultrasound contrast agents (UCA) in the presence or absence of recombinant tissue plasminogen activator (rt-PA) has been widely evaluated as a new modality for treatment of ischemic stroke. Despite the successful demonstration of accelerated clot lysis there are inherent limitat...

The use of targeted nanoparticles for both imaging and therapeutic applications shows significant promise. Photoacoustic tomography is a non‐invasive imaging technique based on the detection of broad‐band acoustic emissionsgenerated by the absorption of laser light in tissue. The introduction of light‐absorbing gold nanoparticles can improve signal...

The Oak Ridge National Laboratory Spallation Neutron Source (SNS) employs a high?energy proton beam incident on a liquid mercury target to generate short bursts of neutrons. Concomitant with neutron production is the rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitationbubbles. The subsequ...

Light and sound waves propagating through tissue are coupled in useful and interesting ways. When a beam of sound travels through diffuse light, photons passing through the beam are phase modulated at the ultrasound frequency, yielding information on tissue optical and acoustical properties via the acousto?optic (AO) effect. Alternatively, the abso...

Acoustically imaging non?cavitating HIFU lesions is challenging due to the relatively weak contrast between normal and necrosed tissues. However, thermal lesions posses optical scattering and absorptioncharacteristics that can differ significantly from surrounding tissue. Acousto?optic (AO) sensing refers to the detection of phase modulated photons...

High-intensity focused ultrasound (HIFU) is a promising modality that is used to noninvasively ablate soft tissue tumors. Nevertheless, real-time treatment monitoring with diagnostic ultrasound still poses a significant challenge since tissue necrosis, in the absence of cavitation or boiling, provides little acoustic contrast with normal tissue. In...

The effect of time-variant temperature on the dynamics of a single gas bubble in a liquid is investigated. With changes in temperature, several physical parameters controlling bubble behaviour change including surface tension, diffusivity, vapour pressure and gas solubility. A single-bubble model is formulated and a numerical simulation implemented...

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.

Backscatter from the sea surface is governed by the roughness of the surface and subsurface micro bubble distributions. At low frequencies, due to the paucity of large bubbles, scattering results primarily from coherent and∕or collective scatter from bubbles entrained by the subsurface vorticity or carried to depth by the Langmuir circulation and t...

The acoustic monitoring of non-cavitating high-intensity focused ultrasound (HIFU) lesions is challenging due to the relatively weak acoustic contrast between normal and necrosed tissues. Fortunately, thermal lesions posses optical scattering and absorption characteristics that can differ significantly from surrounding tissue. Diffusive optical tec...

A technique to enhance the photoacoustic emissions from laser-heated nanoparticles is presented. Gold nano particle-doped phantoms are subjected to pulsed optical and ultrasound fields, resulting in bubble formation and collapse and producing strong acoustic emissions. The applied ultrasound field allows for cavitation at lower laser fluences than...

The collapse of transient bubble clouds near a solid surface was investigated to test a scheme for mitigation of cavitation-induced damage. The target was a porous ceramic disk through which air could be forced. Transient cavitation bubbles were created using a shock-wave lithotripter focused on the surface of the disk. The dynamics of bubble cloud...

The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent colla...

High‐intensity focused ultrasound (HIFU) is a viable treatment option for small tumors. This study investigates the feasibility of employing a photoacoustic (PA) sensor to monitor the in situ temperature rise during HIFU exposures. The present method also provides means to simultaneously monitor inertial cavitation using the same sensor. Polyacryla...

The absorption of laser light in tissue can be enhanced through the use of gold nanoparticles. This enhancement can improve the signal-to-noise ratio of the thermoelastic emissions used for photoacoustic tomography (PAT) and photoacoustic microscopy (PAM). The ability to functionalize nanoparticles allows them to be used for the selective targeting...

Tissue heating by high-intensity focused ultrasound (HIFU) is a promising modality for minimally invasive therapy. However, real-time treatment monitoring still poses significant challenges, particularly at the lower exposure levels where stable cavitation andor boiling does not result. Bubble--free HIFU lesions offer little acoustic contrast; howe...

It has been established that while the inherent presence of bubbles increases heat generation due to scattering and absorption, inertial cavitation is responsible for elevated heating during high-intensity focused ultrasound (HIFU) application. The contribution of bubble-induced heating can be an important factor to consider, as it can be several t...

Photoacoustic tomography is a non-invasive imaging technique based on the detection of broadband acoustic emissions generated by the absorption of light in tissue. This technique utilises the high contrast of optical imaging with high resolution from ultrasound imaging. However, the ability to detect these emissions above the noise level ultimately...

High intensity focused ultrasound (HIFU) is a powerful noninvasive tool for targeted tissue ablation. Monitoring of the treatment process and efficacy in real time, however, remains challenging. The tissue necrosis during the HIFU exposure leads to changes in optical absorption and scattering coefficients. In this paper, we explore the use of acous...

The presence of noise and coherent returns from clutter often confounds efforts to acoustically detect and identify target objects buried in inhomogeneous media. Using iterative time reversal with a single channel transducer, returns from resonant targets are enhanced, yielding convergence to a narrowband waveform characteristic of the dominant mod...

Local hyperthermia is widely studied as a treatment option for small tumors. This study investigates the feasibility of exploiting the photoacoustic (PA) effect to monitor the in situ temperature rise during high-intensity focused ultrasound (HIFU) exposures for therapeutic hyperthermia. Polyacrylamide phantoms with a cylindrical inclusion (3 × 20...

Photoacoustictomography is a non‐invasive imaging technique based on broadband acoustic emissions from light absorption in tissue. Light‐absorbing goldnanoparticles can be introduced and targeted to specific cell populations, thereby promoting both contrast and the ability to delineate tissue types. For sufficiently high laser fluence, a transient...

Acousto‐opticimaging is a dual‐wave modality that combines ultrasound with diffuse light to achieve deep‐tissue imaging of optical contrast with the spatial resolution of ultrasound. While substantial progress has been made in recent years in detecting and imaging optical inhomogeneities in highly scattering media based on the acousto‐optic respons...

Tissue ablation by high?intensity focused ultrasound (HIFU) leads to changes in the optical absorption and scattering of the tissue. Here acousto?optic (AO) sensing was used to detect HIFU induced changes in the optical contrast of chicken breast. The tissue was insonified by 1?MHz HIFU and illuminated by infrared light. The diffuse light that exit...

An electromagnetic acoustic source (EMAS) consists of a flat electrical coil, a thin insulating membrane, and a metal plate. The EMAS is excited by discharging a capacitor through the coil, and the resulting eddycurrents produce a repulsive force on the metal plate launching acoustic waves. Here an EMAS was used to excite acoustic waves in a cylind...

An acousto-optic imaging technique suitable for the local and quantitative determination of subsurface optical properties in turbid media is presented. Acousto-optic signals elicited by ultrasound pulses at two different peak pressures in turbid media are detected by using photorefractive-crystal-based interferometry. The ratio of the measured sign...

Scaled laboratory experiments are conducted to assess the efficacy of iterative, single-channel time reversal for enhancement of monostatic returns from resonant spheres in the free field and buried in a sediment phantom. Experiments are performed in a water tank using a broad-band piston transducer operating between 0.4 and 1.5 MHz and calibrated...

Central to a spallation neutron source (SNS) is a vessel of liquid mercury. During SNS operation acoustic pulses, with pressures in excess of 10 MPa, are generated in the mercury likely resulting in cavitation, which may erode the walls. We developed an electromagnetic shock wave source to generate similar pressures and cavitation. An electromagnet...

The Oak Ridge National Laboratory spallation neutron source (SNS) employs a high-energy proton beam incident on a liquid mercury target to generate short bursts of neutrons. Concomitant with neutron production is the rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subseq...

Real-time imaging of the heating of tissue and lesion formation is a major barrier to the clinical application of HIFU. Tissue necrosis results in a change in the optical properties of the tissue. We have employed the acousto-optical (A-O) interaction to image HIFU lesions formed in excised chicken breast. The tissue was illuminated with infrared l...

Acousto-optic imaging (AOI) is a dual-wave modality that combines ultrasound with diffuse light to achieve deep-tissue imaging of optical properties with the spatial resolution of ultrasound. Progress has been made in the detection of optically absorbing inhomogeneities in recent years, yet it remains a challenge for AOI to detect targets possessin...

High intensity focused ultrasound (HIFU) is a non‐invasive technique for treating soft tissue tumors. A feasibility study for using the photoacoustic (PA) effect to monitor in‐situtemperature changes during HIFU exposures is presented. A PA wave is generated from the thermoelastic expansion of a light‐absorbing medium with its amplitude related to...

The onset and presence of inertial cavitation and near-boiling temperatures in high-intensity focused ultrasound (HIFU) therapy have been identified as important indicators of energy deposition for therapy guidance. Passive cavitation detection is commonly used to detect bubble emissions, where a fixed-focus single-element acoustic transducer is ty...

The speed of sound in a bubbly liquid is strongly dependent upon the volume fraction of the gas phase, the bubble size distribution, and the frequency of the acoustic excitation. At sufficiently low frequencies, the speed of sound depends primarily on the gas volume fraction. This effect can be audibly demonstrated using a one-dimensional acoustic...

No PDF available ABSTRACT An acoustic resonator for measuring free‐gas void fraction of a helium‐mercury mixture is investigated. We employ a vertical, stainless steel cylindrical waveguide with a 5.08‐cm i.d., a 1.27‐cm wall thickness, a 40‐cm length, and pressure‐release boundary conditions at both ends. A bubble injection flow loop produces 2‐ph...

Inertial cavitation is known to play a key role in thermal HIFU therapy, both from the point of view of treatment safety and delivery, and as a potential tool for treatment monitoring. However, bubble behaviour in rapidly changing temperature fields remains poorly understood. Using a theoretical model, we have previously shown that, for a given ini...

The collapse of transient bubble clouds near a boundary was investigated. Transient cavitation bubbles were created using a shock-wave lithotripter. A porous ceramic disk (flow-pressure 7.5psi) was placed at the lithotripter focus. Air was forced through the disk to alter the boundary condition at the ceramic disk's proximal face. Gas pressure belo...

Due to the dynamic nature of the shallow water environment, targets are often buried beneath the seafloor, hindering their detection and identification by acoustic methods. Using iterative time reversal with a single channel transducer [Waters et al., J. Acoust. Soc. Am. 122, 3023 (2007)], the monostatic return from a buried resonant target is enha...

Iterative time reversal techniques developed at smaller scales, [Waters et al., J. Acoust. Soc. Am. 122, 3023 (2007)], are applied to the detection of a 15 cm diameter stainless steel shell buried in sandy sediment at the acoustic test pond at the Naval Surface Warfare Center - Panama City Division. A mid-frequency, directional projector is located...

The backscattering spectrum of thin spherical shells show resonance peaks due to several different physical processes including high frequency Lamb wave excitation and low frequency modal ringing [Kaduchak et al., J. Acoust. Soc. Am. 97, 2699-2708 (1995)]. These different processes can be isolated in both time and frequency by using simulated itera...

The R. Bruce Lindsay Award (formerly the Biennial Award) is presented in the Spring to a member of the Society who is under 35 years of age on 1 January of the year of the Award and who, during a period of two or more years immediately preceding the award, has been active in the affairs of the Society and has contributed substantially, through publ...

Relative measures of the energy radiated as broadband noise emissions by inertially cavitating bubbles, such as the mean square voltage received using a passive cavitation detector (PCD), have been recently shown to be directly relatable to cavitation-mediated bioeffects. Even though numerous techniques exist to detect inertial cavitation qualitati...

A technique for detecting buried resonant targets is described in which enhanced signal-to-noise ratio and convergence to a narrowband signal is achieved using the iterative time reversal of backscattered echo returns. [Waters et al., J. Acoust. Soc. Am. 122, 3023 (2007).] The center frequency of the converged-upon signal is typically a resonance f...

The low-frequency sound speed in a fluid-like kaolinite sediment containing air bubbles was measured using an acoustic resonator technique and found to be 114 ms with negligible dispersion between 100 and 400 Hz. The sediment's void fraction and bubble size distribution was determined from volumetric images obtained from x-ray computed tomography s...

Biomedical acoustics is rapidly evolving from a diagnostic modality into a therapeutic tool, and acoustic cavitation is often the common denominator in a wide range of new therapeutic applications. High-intensity focused ultrasound (HIFU) waves generated outside the body can be used to deposit heat deep within the body. Through a quantitative analy...

The presence of noise and clutter makes identification of targets buried beneath the seafloor a challenging problem. Iterative time reversal using a single‐channel transducer is shown to enhance the signal‐to‐noise ratio of backscattered echo returns from a buried resonant target. Each iteration consists of: (1) Insonifying the target with a broadb...

The collapse of transient bubbles in the vicinity of a boundary was investigated. Transient bubbles were created using a focused laser, and a shock‐wave lithotripter. Two boundary types were investigated, rigid and smooth, and rigid and porous. The porous boundary was either gas‐saturated, or actively bubbling. Acoustic emissions from the collapsin...

The effects of resonant bubbles on the measurement of void fraction in a cylindrical waveguide are examined. Air bubbles are introduced into a steel cylindrical waveguide containing a Xanthan gum gel. The frequency response of the system is obtained. Sound speeds are inferred by assuming a linear dependence of axial mode number on mode frequency, a...

The role of both inertial and stable cavitation was investigated during in vitro ultrasound-accelerated fibrinolysis by recombinant tissue plasminogen activator (rt-PA) in the presence and absence of Optison™. A unique treatment configuration applied ultrasound, rt-PA and Optison™ to the interior of a plasma clot. Lysis efficacy was measured as clo...

Acoustic cavitation has been shown to play a key role in a wide array of novel therapeutic ultrasound applications. This paper presents a brief discussion of the physics of thermally relevant acoustic cavitation in the context of high-intensity focussed ultrasound (HIFU). Models for how different types of cavitation activity can serve to accelerate...

A laboratory experiment was conducted to measure the speed of sound in an artificial water-saturated granular sediment composed of cleaned and sorted medium-grained sand and degassed distilled water. The experiment was conducted within a range of frequencies where dispersion is predicted by a number of existing models. Between 2 and 4 kHz, the soun...

One of the difficulties encountered in verifying sound propagation models for gas bearing sediments is determining the overall void fraction (VF) and the bubble size distribution (BSD), both of which greatly effect the acoustic behavior. Traditional time-of-flight sound speed measurements are hindered at low frequencies because of the large sample...

Acousto-optic (AO) imaging is a new dual-wave modality that combines ultrasound with diffuse light to achieve deep-tissue imaging of optical properties with the spatial resolution of ultrasound. In this technique, the sample is simultaneously insonified by an ultrasound beam and illuminated with a laser source. The ultrasound modulates the optical...

It has been established that inertial cavitation is responsible for elevated heating during high‐intensity focused ultrasound (HIFU) application for certain intensity regimes. The contribution of bubble‐induced heating can be an important factor to consider, as it can be several times that expected from absorption of the primary ultrasound energy....

The onset and presence of inertial cavitation in high‐intensity focused ultrasound (HIFU) therapy has been identified as an important indicator of energy deposition for therapy planning. A common technique for detecting inertial cavitation is passive cavitation detection, where broadband noise emissions indicative of inertially driven bubbles colla...

The identification and classification of mines resting on and buried beneath the sea floor is an important and challenging problem. Previous numerical results indicate that iterative time reversal using a single‐element transducer increases the signal‐to‐noise ratio of the backscattered return while simultaneously converging to a narrow‐band signal...