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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...
Contrast of echographic images has been highly improved by the injection of ultrasound contrast agents that consist of gaz microbubbles. The improvement is due to the nonlinearity of microbubbles, i.e. when excited with a frequency f0, they can generate harmonics at (2f0, 3f0, …). However, the contrast improvement is limited by the nonlinear ultrasound propagation in tissue. To overcome this drawback,...
The modeling of acoustic streaming problems is usually treated by using simulation schemes based on perturbation theory to reduce the computational effort, where a quiescent fluid is assumed in the unperturbed state. However, when considering situations and applications where a steady background flow is present, this zero-order field would directly influence the first- and second-order velocity fields...
The point spread function (PSF), namely the response of a system to a point source, is a measure of the quality of an ultrasound imager system. It highly depends on the image reconstruction algorithm, and it is usually either crudely estimated by assuming spatial-invariance, or evaluated via simulation, as proposed by Field II, coupled with reconstruction algorithms, such as delay-and-sum (DAS). The...
Ultrafast vector flow imaging can provide detailed measurements of 2D/3D blood velocity patterns, but suffers from an increased variance due to reduced SNR and inherent estimator properties. Further, clutter filtering causes measurement dropouts during parts of the cardiac cycle and imposes an angle-dependent measurement accuracy. This work aims to demonstrate how simulation of the incompressible...
A two-dimensional (2D) computational model of acoustic impedance (Z) constructed from histological tissue images, termed 2D Z map (2DZM), was recently proposed to obtain quantitative information about tissue scattering (Luchies & Oelze 2016). However, this 2DZM approach was limited to isotropic and sparse media. The present study investigates the 2D structure factor model (SFM) in 2DZM approaches...
In IUS 2016, we proposed a capacitive micromachined ultrasonic transducer embedded a field effect transistor (CMUT-FET) for 20 MHz operation. As a result, the possibility of high sensitivity in a high-frequency range was verified via a combination of two simulation tools, a 3-D finite element analysis (FEA) for the CMUT part and a technology computer aided design for the FET part. Since the results...
Ultrasound Computer Tomography (USCT) is used to map local wave propagation parameters, such as speed of sound, as potential imaging biomarkers. A reflector-based reconstruction algorithm using a conventional transducer was proposed in [1], yielding satisfactory reconstructions thanks to dynamic-programing based reflector delineation and angular-weighted totalvariation regularization. In this work,...
To implement super-resolution imaging of microvessels in clinical practice, the trade-off between the concentration of microbubbles (MB) appropriate to detect single MB and reasonable short measurement times has to be resolved. Therefore, we estimated the measurement times necessary to adequately reconstruct the microvessel trees in 3 different tumor models.
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...
Ultrasound medical diagnostics is a real-time modality based on a doctor's interpretation of images. So far, automated Computer-Aided Diagnostic tools were not widely applied to ultrasound imaging. The emerging methods in Artificial Intelligence, namely deep-learning, gave rise to new applications in medical imaging modalities. The work's objective was to show the feasibility of implementing deep-learning...
Pre-fatigue damage can have drastic effects on the elastic nonlinearity of solid materials, offering the possibility of extracting spatially resolved information on the pre-fatigue state from nonlinear effects on guided waves, like harmonic generation [1]. Of particular interest are surface and wedge acoustic waves. They are sensitive to surfaces and edges and are non-dispersive in homogeneous media,...
Intrauterine growth retardation (IUGR), and preeclampsia (PE) are major public health challenges. In these situations, significant changes in the villous tree structure probably affect placental elasticity, and their detection could improve diagnostic accuracy and prognosis assessment. To date, no clinical device provides information about placental elasticity or architecture.
Recent studies suggest that the analysis of the intracardiac blood flow dynamics via vector imaging can provide relevant evaluation of cardiac dysfunction. In particular, the clinical importance of intraventricular vortex formation has been underlined. Cardiac magnetic resonance and contrast-enhanced ultrasound are commonly used. These approaches, however, cannot be integrated into routine clinical...
The Keller-Miksis equation (KME) is commonly used for numerical studies of inertial and stable-inertial cavitation. However, experimental validation of KME under clinically relevant exposure settings is scarce, particularly in terms of the acoustic emission signal generated by the cavitation. Validation of KME for strongly driven bubbles could significantly aid the design of arrays for passive acoustic...
An accurate nonlinear lumped equivalent circuit model is used for modeling of capacitive micromachined Ultrasonic Transducers (CMUTs). Finite element analysis (FEA) is a powerful tool for the analysis of CMUT arrays with a few number of cells while with the equivalent circuit model, the entire behavior of a large-scale arbitrary CMUT array can be modelled in a very short time. Recently, an accurate...
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...
Contrast of echographic images has been highly improved by the injection of microbubbles, due to their nonlinear behavior. However, this contrast enhancement is limited by the nonlinear acoustic propagation in tissue. To overcome this drawback, sub and ultra-harmonic contrast imaging can be used, since only microbubbles can generate these components. Nonlinear modeling is a primordial step in the...
Ultrafast ultrasound (US) imaging uses unfocused waves to insonify the whole medium of interest at once, allowing pulse-echo US imaging to achieve very high frame rates, at the cost of a lower image quality. In this paper, we present USSR, an UltraSound Sparse Regularization framework which permits high-quality imaging at fast rates and with a very low memory footprint. The framework, based on highly...
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