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Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
The primary aim of this work was to develop and study the potential of Capacitive Micro-machined Ultrasound Transducers (CMUTs) for dual-mode ultrasound therapy and imaging. This was investigated in the context of Ultrasound-guided High Intensity Focused Ultrasound (USgHIFU) designed for endocavitary HIFU tissue ablation of the prostate gland. The hypothesis is that this CMUT design could offer potential...
Histotripsy with ultrasound is an emerging noninvasive therapeutic modality that uses cavitation to precisely destroy diseased soft tissue. Accurate simulations of histotripsy are needed for treatment planning and device design. These simulations are performed in the time-domain, span hundreds of wavelengths, and must handle strong shocks and discontinuities between materials, such as the brain and...
While tissue-mimicking phantoms have been useful in the validation of ultrasonic equipment and image processing techniques, they are often restricted to simple vascular geometries due to limitations in fabrication techniques. To address this need, a novel technique has been employed to fabricate 3D-printed photo-curable poly(ethylene glycol) (PEG) hydrogel constructs containing complex, small-scale...
One of the major cause for the attenuation of ultrasonic waves in polycrystalline materials is the random scattering at the grain boundaries — grain boundary scattering (GBS) —, whereby the acoustic mismatch is the result of the random orientation of the mechanical properties of the single crystals within the individual grains. Various analytical models, such as the unified theory, have been developed...
The k-Wave MATLAB toolbox is widely used to conduct medical ultrasound simulations. These require accurate models of acoustic sources. In k-Wave, a k-space pseudospectral time domain model of acoustic propagation, sources are introduced by adding acoustic pressure at points on a uniform, orthogonal grid. For curved sources two issues arise: First, points on the source's surface do not necessarily...
Blood-brain and blood-tumor barriers (BBB and BTB) constitute a major obstacle to the transport of therapeutics in brain tumors. While several studies have demonstrated the potential of focused ultrasound (FUS) to disrupt transiently the BBB/BTB and improve drug delivery, there is a lack of fundamental understanding of the impact of this method on the pharmacokinetics of anticancer agents in the brain...
Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), efficiency enhancement has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. Researchers reported theoretically and experimentally that the enhanced effect is due to the enhancement of inertial cavitation. One key experimental observation...
Contrast enhanced ultrasound (CEUS) has shown great promise in quantifying myocardial perfusion and ventricular flow. More recently high frame-rate contrast enhanced echocardiography (HFR CE), based on pulse inversion (PI) and diverging waves, has shown to significantly improve the image contrast over standard CEUS [M. Toulemonde, IUS 2016]. Both contrast pulse sequences and spatial compounding involve...
Low intensity Focused Ultrasound (FUS) combined with microbubbles open locally and not invasively the Blood-Brain Barrier (BBB) allowing passage of nanoparticles into the brain [Hynynen et al. 2001]. However, since the quantity of particles that can be delivered with this technique depends on tissue properties, on particle properties as well as on acoustic parameters, so far a model fully predicting...
The attenuation of ultrasound in soft tissue follows a frequency-dependent power law. As an alternative to the time-fractional partial differential equations that describe power law attenuation and dispersion, Treeby and Cox derived a space-fractional model that accounts for both power law attenuation and dispersion. The Treeby-Cox space-fractional wave equation is convenient for simulations with...
The normal way to simulate SAW resonators is to use a phenomenological model like coupling of modes or P matrix. Numerical methods can also be used but are very costly in computing resources. Models based on combination of finite elements and boundary elements models are a possible approach but are mostly limited two dimensional models. Also, they are less versatile than models using only finite elements...
The investigation of multiphase non-Newtonian flows is of big interest, e.g. for the optimization of the flow field in secondary hydraulic zinc-air batteries (ZAB). These batteries are operated by pumping an opaque suspension of zinc particles and an aqueous potassium hydroxide solution with a binder through an electrochemical cell. Flow investigation is done by means of computational fluid dynamics...
Optimization of ultrasound applications in medical diagnostics as well as in non-destructive testing demands accuracy in prediction of ultrasound propagation. Several attempts were used and few different simulation methods were proposed as a publicly available software toolboxes. Although the Field II, k-Wave, Creanuis belong to most popular ones, we propose new toolbox for the simulation of acoustic...
A new toolbox for the simulation of acoustic wave fields is described. The toolbox, USim, is designed to make an acoustic modeling of ultrasound propagation in tissues reliable and fast. The forward simulations of the wave field are based on the Born-Neumann single scattering approximation of the solution of Sturm-Liouville equation. The toolbox allows simulating the ultrasound wave propagation in...
The k-Wave MATLAB toolbox is widely used to conduct medical ultrasound simulations. It uses a Fourier collocation method to numerically solve the governing model equations, and introduces sources by adding acoustic pressure at points on an orthogonal grid. This approach introduces two errors when sources don't exactly align with the grid. These are phase errors arising from shifting source points...
Driven by the need for high data-rates and improved cell coverage, mobile phone filters are required to process increasingly high RF power levels. The simultaneous demand for smaller filter footprints makes designing a filter for high-power performance a challenge. We report a method for simulating the self-heating effects of high input powers on a surface acoustic wave (SAW) filter. We also report...
Understanding of the propagation of ultrasound through a bubbly medium is a challenging task because of the nonlinear dynamics of the bubbles and their effect on the attenuation and sound speed of the medium. The majority of the studies on this subject apply linear models, which will generate inaccurate results, especially at higher-pressure excitations. These studies have also ignored the effect...
Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency...
Grain-boundary scattering of acoustic waves in polycrystalline materials is studied with analytical and numerical methods in the presented paper. In particular, the attenuation of Surface Acoustic Waves (SAWs) propagating through a polycrys-talline microstructure is investigated. A three dimensional timedomain finite-element method (FEM) is utilized for the numerical simulation, whereby the granular...
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