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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...
Quantum Spin Hall Effects(QSHE) underpins most of the design in topological insulators. The intrinsic spin-0 of the phononics, yet, continue to be the main barrier in designing acoustic topological insulators. Previous research proposed a solution using external fields such as clockwise and counter-clockwise circulating fluids to create artificial acoustic spin-1/2 states. Most recently, several papers...
In cortical bone, osteoporosis impacts both pore size and porosity. A theoretical model predicting ultrasonic parameters based on cortical micro-architectural parameters remains to be developed, and the independent effect of pore size and porosity on ultrasonic parameters remains unclear. Here, we propose a model predicting the attenuation, phase velocity and scattering mean free path (SMFP) in cortical...
Design of side edges is one of the most important tasks for realization of high performance RF SAW/BAW devices. For the purpose, the authors proposed an FEM based technique where the specified mode is injected to the border under concern through a damping mechanism, and scattering coefficients are estimated from calculated BAW field [1]. Even though this technique is effective, its setup is too complicated...
Imaging using the total focusing method (TFM) is a popular tool in nondestructive evaluation and it becomes a standard. From full matrix capture, this method consists in focusing at each point of a defined reconstruction zone. It is generally more efficient than conventional phased array focusing that can focus at only a few points. Despite the good quality of TFM images, TFM suffers from a lack of...
Power Doppler (PD) is the preferred technique for accessing weakly scattering blood cells with low-velocity flow. However, strong clutter decreases sensitivity of the blood signals, which degrades micro-vasculature imaging. Eigen-based filtering methods have been developed to separate the independent scattering sources using both spatial and slow-time statistics of echo data. We recently found that...
Recently, ultrasound imaging of muscle contractions has been used by several research groups to infer volitional motor intent of the user, and has shown promise as a novel muscle computer interface. Learning spatiotemporal features from ultrasound image sequences is challenging because of deformations introduced by probe repositioning. The image features are sensitive to probe placement and even small...
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...
In order to achieve better performance of bulk and surface acoustic wave resonators operating at several GHz, it is crucial to dispose of advanced techniques and methods to provide information about the elastic constants of the constituent layered materials and to image the spatial profile of the acoustic field, both inside and outside the resonator.
To understand physiologic state in diseased liver e.g. non-alcoholic steatohepatitis, this study aims to analyze the acoustic impedance (Z) of hepatic cells using a scanning acoustic microscopy (SAM). Ultrasound scattering sources in cells, however, cause the multi-reflection and prevent from analyzing the precious value of Z although it provides the useful information of structure in cells (M. N...
Linear reconstruction techniques based on the Born approximation are known to be unable to reconstruct speed of sound quantitatively. Recently, it was shown that non-linear reconstructions based on the Kaczmarz method can overcome this limitation (Hesse, Salehi, and Schmitz 2013). However, a fundamental problem towards its practical application is the convergence. As described by Natterer (Natterer...
The resolution of ultrasound images is limited by the bandwidth of the imaging system and the features of the propagating medium. Using certain assumptions, image restoration can recover out-of-bandwidth data and improve resolution. Several resolution improvement methods have been reported in the literature. Due to the lack of ground truth, their evaluation remains an open issue. Indeed, to evaluate...
Nondestructive evaluation of material microstructure has become increasingly relevant with the surge of advanced manufacturing methods. Because factors such as grain size and shape dictate material properties, accurate characterization of these features is crucial when implementing novel production methods. Previous ultrasonic approaches to measure grain size in complex media have been hindered by...
The range spatial resolution in ultrasound imaging is an important index determining the image quality and basically determined by the frequency band width of the ultrasonic transducer. In the present study, a new element-domain signal processing technique based on the maximum likelihood method was developed for improvement of the range spatial resolution in ultrasonic imaging.
In the past, members of our group developed a model based beamforming method called aperture domain model image reconstruction (ADMIRE). They tuned ADMIRE to improve ultrasound image quality by suppressing sources of image degradation such as off-axis scattering, reverberation, and phase aberration. In addition, the development of ADMIRE demonstrated that beamforming could be posed as a regularized...
Traditional B-Scan images show the envelope of received echoes as a grey scale image. The echoes are produced from specular reflections and scattering sites where changes in acoustic impedance occur (Cobbold, Foundations of Biomedical Ultrasound, Oxford Press, 2007). A long-standing area of interest concerns the frequency dependence of scatterers within different tissues, organs, and the blood.
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...
Resistance spot welding is one of the most widely used joining methods for sheet metals. As more advanced sheet metals are developed and used, new welding parameters need to be developed and optimized to meet a required weld strength. During this process, numerous test coupons are typically generated and examined destructively to analyze the size and microstructure character of the weld nuggets. Weld...
There are significant differences in microvasculature density, tortuosity, and anisotropy of cancerous and benign tissue, which makes non-invasive methods to quantify these microvascular architectural properties highly relevant for applications like monitoring the response to anti-angiogenic treatments. We present a method to quantify these properties using ultrasound multiple scattering from contrast...
The lung parenchyma is a highly complex and diffusive medium for which ultrasound (US) techniques have remained qualitative. US quantitative characterization of the lung has remained elusive due to the presence of air-filled alveoli which is responsible for Multiple Scattering (MS). There is a need from pulmonologists for a method which would enable them to stage and monitor pulmonary edema and fibrosis...
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