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Cardiac function has traditionally been studied using pressure-volume (PV) loop analysis. PV loops can be used to derive functional indices such as end-systolic pressure volume relationship (ESPVR)—a measure of myocardial contractility, end-diastolic pressure volume relationship (EDPVR) — a measure of myocardial compliance and relaxation time constant (τ) — a measure of left ventricular relaxation...
Elastic properties of the ocular tissues are significantly affected by intraocular pressure (IOP) in the eye. For example, the speed of the elastic wave in the cornea dramatically increases with IOP. In our previous studies using ultrasound shear wave imaging we demonstrated that, for the lens, the increase in IOP does not result significant changes in the wave velocity. Compared with ultrasound imaging,...
Shear wave elastography is useful for quantitatively evaluating tissue elasticity by measuring the speed of a shear wave induced within the body by acoustic radiation force. We proposed a pushing-and-tracking sequence, coded push-pulse excitation to increase the signal-to-noise ratio (SNR) of the observed shear wave propagation without increasing measurement time and push-pulse amplitude1). In this...
High-intensity focused ultrasound (HIFU) have been an attractive research topic for some time now. HIFU studies have started with single-element transducers, but using arrays provide the opportunity to scan the focal point electronically. Modular and scalable driving systems that can adapt to custom-made transducer elements to drive these arrays are needed and at the present time there are few such...
The control of acoustic fields in 3-D is vital in many areas of physical acoustics. Recently, a new approach for the generation of complex diffraction limited acoustic fields in 3-D was introduced. This works by calculating a phase hologram designed to generate a desired acoustic field. The output of a simple planar transducer is then mapped onto this phase distribution using a 3-D printed kinoform...
We present a fully-populated 2D-phased array, capable of emitting directed air-coupled ultrasound at 40 kHz without any grating lobes. In comparison to our previous work [Konetzke et al, IUS 2015], in which we describe a 1D-phased array, we use 3D printing techniques to realize a wave guide structure that fulfills the half-wavelength criteria of 4.3 mm. The key idea is to use the wave-guide structure...
Accurate measurement of acoustic dispersion has important applications in theoretical acoustics, ultrasound tissue characterization, ultrasound measurement systems, etc. Usually, the parameter of interest associated to dispersion is the variation in the propagation velocity as a function of the frequency or the temperature. Nevertheless, this work is focused on the study of the variation in the propagation...
Forward-looking intravascular ultrasound (FL-IVUS) transducers are needed to image complex lesions in the coronary arteries, such as chronic total occlusions (CTOs). To achieve 2D and 3D FL-IVUS imaging, transducer arrays can be integrated at the tip of the catheter. However, connecting the elements is challenging due to the limited space available. In this work, we present a FL-IVUS matrix transducer...
Oil has been used in many fields, such as transportation systems and machine tools. Performances of those depend on oil quality. However, quality is normally checked by visual inspection. Therefore, it is required to develop a sensor for monitoring oil quality to measure online and real time. A shear horizontal surface acoustic wave (SH-SAW) sensor can detect liquid properties. In this paper, particles...
Subharmonic aided pressure estimation (SHAPE) is based on the inverse relationship between the subharmonic amplitude of contrast microbubbles and the ambient pressure. A noninvasive ultrasound based pressure estimation procedure would be a major development in the diagnosis of portal hypertension and less invasive than the current hepatic venous pressure gradient (HVPG) measurement. The hypothesis...
In previous work, the advantage of using super-harmonic contrast imaging to visualize the microvasculature in tumors and organs has been demonstrated [1]. This was performed using dual frequency (DF) probes consisting of a high frequency single element transducer from a motorized probe concentric with a low frequency ring [2]. However, mechanically scanned systems have limitations, including single...
Non-alcoholic fatty liver disease (NAFLD) is a major health concern due to the increasing obesity epidemic and it has the risk to progress to liver fibrosis, cirrhosis and hepatocellular carcinoma. It is important to assess the severity of hepatic fibrosis for the risk-stratified management of patients with NAFLD. Ultrasound elastography is a new technique for evaluation of liver fibrosis and it has...
Ferroelectric polymers like polyvinylidenefluoride (PVDF) and its copolymer with trifluoroethylene [P(VDF-TrFE)] are widely used in sensor and transducer applications. Good acoustic match to many materials (e.g. water, polymers, and human tissue) and high chemical stability make these materials suitable for ultrasonic applications, especially in the high frequency end (20 MHz-1 GHz). The current work...
Sonothrombolysis with microbubbles (STL) is being explored as a promising therapeutic alternative in ischemic stroke. The objective of this study is to better understand the impact of STL +/-rt-PA on the acoustic properties of blood clot in vitro.
The flawless operation of a power transformer is essential to a functioning “smart” grid. Measurement of the dielectric breakdown voltage (BDV) of insulating oil in real-time and online, is the most crucial and desired feature to manage the high-energy power network. Established good laboratory practices have shown that the BDV is mainly dependent on two major factors: absolute moisture (Wc) and total...
Shear wave elasticity imaging (SWEI) measures mechanical properties of tissues and has been used to characterize tissue stiffness, but SWEI is limited by low displacement SNR in stiff media such as skin. A method for repeatable measurement of skin elasticity is critical for longitudinal monitoring of sclerotic diseases such as morphea. Constructive Shearwave Interference (CSI) overcomes the SNR limitations...
Since the beginning of using piezoelectric single crystals for highly-precise microacoustic components rigorous knowledge of material constant (MC) sets was an indispensable requirement for mastering the subject. The sets have to be both accurate and complete. Accuracy is important for acceptable agreement between device simulation and experimental reality, completeness preferentially plays a role...
Piezoelectric transducers have been employed in trapping particles and molecules in microfluidic platform. Here we studied the acoustic streaming effect of multiple Lamb wave resonators (LWRs) in liquid. A novel device consisting of 4 LWRs was designed and fabricated. The experiment result demonstrated that the LWR array can efficiently drive multiple cylindrical vortices in liquid and trapped the...
Multi-element ultrasound arrays are increasingly used in clinical practice for both imaging and therapy. In therapy, they allow electronic steering, aberration correction, and focusing. To avoid grating lobes, an important requirement for such an array is the absence of periodicity in the arrangement of the elements. A convenient solution is the arrangement of the elements along spirals. The objective...
In ultrasound 3-D imaging an N×N element 2-D array can be operated utilizing only 2N connections, when row-column addressing is used. One issue with the row-column-addressed (RCA) arrays is that the imaging can only be performed within a rectilinear region in front of the array. This study proposes and evaluates the possibility of curvilinear 3-D imaging with RCA arrays, using a double-curved diverging...
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