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Recently we demonstrated non-contact excitation of broadband mechanical waves in soft media for transient elastography. Using US from an air-coupled transducer focused on an air/medium interface, this method (called “acoustic micro-tapping”, or AμT) provides sufficient radiation force to launch a transient displacement. Combined with ultrafast phase sensitive OCT, AμT-OCT can track propagating mechanical...
Echocardiography is the most used modality for the evaluation of cardiac function. To obtain a time-resolved volumetric quantification of cardiac motion, ultrafast 3-D imaging is required. Ultrafast ultrasound imaging with diverging waves has demonstrated its potential for clinical 2-D echocardiography. It has been shown that MoCo (motion compensation) strategies based on a triangle transmit arrangement...
Capacitive micro-machined ultrasonic transducers (CMUTs) offer several advantages over conventional piezoelectric transducers in terms of acoustic performance and circuit integration capability. In this study, we focus on the potential of CMUTs for the high receiving sensitivity which is strongly required for photoacoustic imaging applications. We propose an advanced CMUT cell design with an ultra-narrow...
Because conventional geophysical measurements cannot directly measure the microstructure or pore fluids of rocks, new measurement approaches are needed as well as one that can select regions of interest. The aim of this study is to utilize the nonlinear interaction of two co-propagating longitudinal waves to characterize induced viscoelastic changes occurring in the rock microstructure. Our experimental...
Coupling between surface acoustic waves (SAW) and arrays of mechanical resonators has appeared early in SAW history as a potential means to slow down wave propagation through mass-loading, in particular by creating corrugations on the substrate surface. This concept has been revisited over the past few years in the context of locally-resonant phononic crystals where pillars deposited on a homogeneous...
Noninvasive electrical brain imaging in humans often suffers from poor spatial resolution due to the uncertain spread of electric fields through the head. To overcome this limitation, we propose 4D transcranial acoustoelectric brain imaging (tABI) for mapping current densities at a spatial resolution confined to the ultrasound (US) focus. Acoustoelectric (AE) imaging exploits an interaction between...
Ultrasonic standing waves (USWs) particle sorting has shown great potential to develop diverse applications in biotechnology and medical research due to its ability to offer non-contact, label-free particle manipulation. Currently, most reported on-chip acoustic particle sorters rely on high Q-value materials and elaborate geometry designs, which make these devices not easy to build and unsuited for...
As the medical ultrasound signals are not stationary, the radiation pattern of the corresponding input data does not have a specific shape. Thus, their reconstruction using adaptive beamformer (BF) become indispensable in order to improve the quality of the image. Generalized Side Lobe Canceller (GSC) is a robust realization against clutter and interference, resulting from an elegant representation...
Carotid plaque vulnerability is difficult to characterize from B-mode ultrasound imaging alone. However, elastographic characterization of plaque mechanical properties may aid in the assessment of vulnerability. As an initial step to understand the complex wave propagation that can occur in plaques, we have developed simulation models that incorporate different shear moduli (μ) of the arterial wall,...
Multiple research groups have recently innovated image recovery methods for fast pulse-echo ultrasound imaging (UI) that combine inverse scattering techniques with compressed sensing (CS). These methods alleviate the inherent tradeoff between the image quality and the image acquisition rate. The choice of the incident sound field is a crucial degree of freedom to implement the specific requirements...
Medical imaging through a targeting agent promises to improve the specificity and sensitivity of cancer detection. Nanoparticles (NPs) may provide advantages for targeted photoacoustic (PA) imaging due to their unique physical and optical properties. In our previous study, we developed a phase-change contrast agent made from a biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA) and loaded...
To elicit bio-effects, ultrasound (US) stimulated microbubbles (MBs) must be in proximity to their target and this is not always the case (e.g. sonothrombolysis). Radiation forces can direct MBs to clots and our previous work suggested clot degradation patterns (Fig A) could be influenced by ‘transport pulses’. However, this is a complex process involving a population of MBs, with size-dependent radiation...
Point shear wave elastography (pSWE) provides noninvasive measures of mechanical stiffness of biological tissue. Over the past decade, research has demonstrated that pSWE is effective at diagnosing a multitude of pathologies such as liver fibrosis and cancer. Life science researchers stand to benefit tremendously from access to pSWE but a number of challenges have limited its use in small animals...
Cardiovascular diseases are the leading cause of death globally. Such diseases may affect the left ventricular function, which in turn is closely related to the left ventricular stiffness. Estimation of cardiac deformation can give information on the myocardial stiffness, and may therefore be important in assessment of cardiovascular diseases. A 3D motion estimation scheme is necessary to measure...
High-frequency ultrasound (>20 MHz) imaging has gained widespread attention due to its high spatial resolution being useful for basic cardiovascular and cancer research involving small animals. The sampling rate of the analog-to-digital converter in a high-frequency ultrasound system usually needs to be higher than 120-MHz to satisfy the Nyquist requirement. However, the sampling rate is typically...
Keloids are benign dermal disease that are characterized by the collagen deposition and growth beyond the boundaries of the original wound position. Many studies on keloids have showed that the density of blood vessel within keloids is higher than normal skin, which is a determinant of the physiological conditions of the tissue and also important for understanding the pathogenesis and radiotherapy...
Microembolization during PCI for acute myocardial infarction can cause microvascular obstruction (MVO). MVO severely limits the success of reperfusion therapies and is linked to worse prognosis, including death. A recent clinical trial showed that adjunct short pulse MB+US therapy prior to and following PCI in first STEMI patients, improved angiographic recanalization prior to PCI and ejection fraction...
Our earlier work on support vector machines (SVM) and ultrasonic flaw detection algorithms demonstrated i) highly accurate classifier performance and ii) the feasibility of the algorithm for real-time implementation on low-cost embedded systems with graphical processing units (GPU) and CUDA library (a parallel computing platform and programming model) support. This works extends the implementation...
Traumatic spinal cord injury (tSCI) often leads to debilitating neurological disabilities that in addition to the loss of sensory and motor capabilities, also includes other issues with the bladder, heart and respiration. Overall, tSCI results in a drastic decrease in the quality of life. Traumatic spinal cord injury causes an almost complete loss of blood flow at the site of injury (primary injury)...
Suppression of the SH-SAW response is mandatory to design TC SAW devices on θ degree rotated Y-cut LiNbO3. However, it is not easy because K2 for SH SAW changes rapidly with θ, and its optimal value in terms of the SH-SAW suppression is dependent on electrode and SiO2 thicknesses. The authors found that the optimal θ always locates close to θ where difference in velocities of two SAWs is minimum....
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