Simulations and measurements of 3-D ultrasonic fields radiated by phased-array transducers using the westervelt equation

Doinikov, Alexander A.; Novell, Anthony; Calmon, Pierre; Bouakaz, Ayache

doi:10.1109/tuffc.2014.3061

Cited by 25 publications

(15 citation statements)

References 33 publications

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“…The acoustic properties of the skull, brain and water are shown in Table 1 , and were applied to simulations of the acoustic field [ 29 ]. A non-linear acoustic model was employed to solve the Westervelt equation [ 30 ] as shown below: where p is the acoustic pressure; c 0 is the speed of sound; ρ 0 is the density; β = 0.1 is the acoustic nonlinearity coefficient; δ is the sound diffusivity. The sound diffusivity δ is obtained through the relationship , where α is the acoustic attenuation coefficient and ω is the angular frequency of ultrasound.…”

Section: Methodsmentioning

confidence: 99%

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain

et al. 2018

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Generating spatially controlled, non-destructive changes in the interstitial spaces of the brain has a host of potential clinical applications, including enhancing the delivery of therapeutics, modulating biological features within the tissue microenvironment, altering fluid and pressure dynamics, and increasing the clearance of toxins, such as plaques found in Alzheimer’s disease. Recently we demonstrated that ultrasound can non-destructively enlarge the interstitial spaces of the brain ex vivo. The goal of the current study was to determine whether these effects could be reproduced in the living brain using non-invasive, transcranial MRI-guided focused ultrasound (MRgFUS). The left striatum of healthy rats was treated using MRgFUS. Computer simulations facilitated treatment planning, and targeting was validated using MRI acoustic radiation force impulse imaging. Following MRgFUS treatments, Evans blue dye or nanoparticle probes were infused to assess changes in the interstitial space. In MRgFUS-treated animals, enhanced dispersion was observed compared to controls for 70 nm (12.8 ± 0.9 mm3 vs. 10.6 ± 1.0 mm3, p = 0.01), 200 nm (10.9 ± 1.4 mm3 vs. 7.4 ± 0.7 mm3, p = 0.01) and 700 nm (7.5 ± 0.4 mm3 vs. 5.4 ± 1.2 mm3, p = 0.02) nanoparticles, indicating enlargement of the interstitial spaces. No evidence of significant histological or electrophysiological injury was identified. These findings suggest that transcranial ultrasound can safely and effectively modulate the brain interstitium and increase the dispersion of large therapeutic entities such as particulate drug carriers or modified viruses. This has the potential to expand the therapeutic uses of MRgFUS.

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Section: Methodsmentioning

confidence: 99%

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain

et al. 2018

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“…In any given physical domain considered, the acoustic pressure distribution has been determined through the solution of the Westervelt equation formulated in 3 D Cartesian space coordinate. The input signal from a focused circular transducer working on a single frequency has been modeled using planar pressure source approximation [28,29]. Pressure produced by the transducer (placed at z ¼ 0) has been calculated using the following expression:…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Numerical analysis of thermal response of tissues subjected to high intensity focused ultrasound

Gupta

Srivastava

2018

International Journal of Hyperthermia

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The present work is concerned with the numerical investigation of the thermal response of tissuemimicking biological phantom(s) subjected to high intensity focused ultrasound (HIFU). Simulations have been performed on the 3-dimensional physical domain for two-layered as well as multi-layered medium consisting of water and liver tissue. Local pressure distribution within the body of the phantom has been calculated by solving the complete full-wave nonlinear form of Westervelt equation. The solution of the pressure wave equation has been coupled with Pennes bioheat transfer equation to determine the full field temperature distribution. Results in the form of pressure fields, temperature distributions and the corresponding thermal dosage in the targeted region of the tissue domain have been presented. Magnitudes of the maximum pressure (and hence the resultant temperature levels) in the focal region as obtained using the nonlinear form of Westervelt equation are found to be significantly higher than that determined based on the linear form of the equation. Compared to water, wherein the acoustic intensity is maximum, the addition of sub-layers of skin, fat, and muscle into water resulted in the reduction of the peak intensity and also shifted the intensity profiles along the direction of propagation of the acoustic waves. However, addition of liver tissue into water led to the shifting of intensity profile in the opposite direction i.e., towards the transducer. The results further reveal that due to the dependence of attenuation coefficient on the source frequency, the temperature at the focal region increases with an increase in the transducer frequency. The work is further extended from single lesion to multiple lesion generation through controlled movement of the transducer and the resultant transient full field temperature distribution has been presented. The concerned observations highlight the need of optimizing the thermal energy for each lesion, the inter spatial distance between different lesions and the delay time so as to ensure minimal thermal damage to the surrounding healthy cells as well as to reduce the total treatment duration.

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“…To model the ultrasound wave propagation in thermoviscous medium incorporating the effects of absorption, diffraction, and nonlinearity, a widely used Westervelt equation was employed, which can be written as follows [23]:…”

Section: Acoustic Model For Ultrasound Wave Propagationmentioning

confidence: 99%

Influence of Blood Vessels on Temperature during High-Intensity Focused Ultrasound Hyperthermia Based on the Thermal Wave Model of Bioheat Transfer

Tan

Zou

et al. 2018

Advances in Condensed Matter Physics

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The coupled effects of blood vessels and thermal relaxation time on temperature and thermal lesion region in biological tissue during high-intensity focused ultrasound (HIFU) hyperthermia are numerically investigated. Considering the non-Fourier behavior of heat conduction in biological tissue, the traditional Pennes bioheat equation was modified to thermal wave model of bioheat transfer (TWMBT). Consequently, a joint physical model, which combines TWMBT for tissue and energy transport equation for blood vessel, is presented to predict the evolution of temperature and the thermal lesion region. In this study, pulsatile blood flow is first introduced into numerical study of HIFU hyperthermia, and thermal relaxation time, ultrasonic focus location, blood vessel radius, and blood flow velocity are all taken into account. The results show that the thermal relaxation time plays a key role in the temperature and the thermal lesion region. Larger thermal relaxation time results in lower temperature and smaller thermal lesion region, which indicates that TWMBT leads to lower temperature and smaller thermal lesion region compared to Pennes bioheat transfer model. In addition, we found that the ultrasonic focus location and blood vessel radius significantly affected the temperature and thermal lesion region, while the heartbeat frequency and amplitude factor of pulsating blood flow as well as the average velocity of blood flow had only a slight effect.

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Simulations and measurements of 3-D ultrasonic fields radiated by phased-array transducers using the westervelt equation

Cited by 25 publications

References 33 publications

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain

Numerical analysis of thermal response of tissues subjected to high intensity focused ultrasound

Influence of Blood Vessels on Temperature during High-Intensity Focused Ultrasound Hyperthermia Based on the Thermal Wave Model of Bioheat Transfer

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