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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,...
Electromagnetic [1] and acoustic [2] metamaterials that exhibit linear dispersion at a nonzero frequency and a wave vector (k) of zero, leading to a conical dispersion surface or so-called Dirac cone dispersion, have been demonstrated recently. These materials display unusual behavior associated with the occurrence of a finite group velocity at k = 0, leading to a wave which propagates with a uniform...
It is widely accepted that cell membrane rupture induced by bubbles oscillating beside the cells is a maj or mechanism of sonoporation; however, elucidation of bubble dynamics by high-speed observation is still important because the behavior is highly dependent on their surrounding conditions. In this study, a new observation chamber was developed. The observation chamber allows observation of bubble-cell...
Histotripsy is considered a non-invasive therapeutic modality capable of mechanically fractionating tissue using cavitation bubbles induced by high intensity focused ultrasound pulses. Histotripsy-induced cavitation region over relatively large focal volume is effective in treating sizable lesion, while compromising its treatment precision. We demonstrate high-precision cavitation treatment using...
We have developed a new, fast and simple 3D imaging approach referred to as Simultaneous Azimuth and Fresnel Elevation (SAFE) compounding. The principle behind this technique is to perform conventional plane wave compounding with the bottom set of electrodes, while implementing a reconfigurable Fresnel elevation lens with the top electrodes. While a Fresnel lens would usually result in unacceptable...
Nematic liquid crystal is widely used in optical devices such as liquid crystal displays. The optical characteristics of liquid crystal devices (ex, birefringence) can be controlled by applying an electric field because the liquid crystal molecules have electric dipoles. Although indium tin oxide (ITO) is generally employed as the transparent electrode material, ITO needs the rare metal indium and...
Catheter-delivered ultrasound has been widely utilized for intravascular therapies such as thrombolysis, drug delivery, and plaque removal. High amplitude pressure is required for cavitation induced-microstreaming, which is considered main factor for therapeutic efficiency. Precise spatiotemporal control of insonation is important to relieve concerns on ultrasound-induced damaging of surrounding healthy...
3D Ultrasound systems present several technical challenges, particularly the large number of elements in a 2D array, high electrical impedance, and image acquisition time. Crossed electrode arrays address some of these issues, especially the huge reduction in number of elements. However, creating a two-way focused 3D image in real-time is difficult with these arrays because azimuth and elevation dimensions...
In this work, we present experimental results on subwavelength focusing of an ultrasound beam by a polymer ball-shaped lens (Rexolite) immersed in water at room temperature. The superfocusing phenomenon occurs in the shadow region of the ball lens in the nearfield. The ball lens with radius 12.2 mm yields a focused beam with a 14.4 dB-intensity gain, a subwavelength focal spot with the full width...
In this paper, we report the development of optical fiber laser-generated-focused-ultrasound (LGFU) transducers for intravascular therapies. By combining advantages of fiber optics and photoacoustics, high frequency (>10 MHz), high pressure (> 10 MPa), short pulse (<10 ns) shock waves can be generated from a small aperture (<1 mm in diameter), which is immune to electromagnetic noise....
Surface acoustic wave (SAW) devices are widely used as acoustic-electronic components today. The lithium niobate was often used as the substrate of SAW devices for its higher electromechanical coupling coefficient. In some applications like RFID tags and sensors, SAW devices have a long delay line and the energy loss of diffraction is considerable. Phononic crystals (PnC) have properties of band gaps...
Acoustic lenses, concentrating the acoustic energy into a specific area, have attracted interest due to their broad applications in various domains, such as biomedical imaging, nondestructive testing, etc. For waterborne sound, conventional silicone materials are fabricated with concave shape for focusing wave. However, it is not flexible to design a concave lens than a flat lens to manipulate acoustic...
We numerically report a high efficient acoustic lens using a flat artificial composite plate in water, which is designed using silicone films deposited on PMMA plate engraved with the annular grooves. The focusing effect is due to the phase of the plate changing with the height of PMMA variation, while the total height of the plate is held constant. As both PMMA and silicone are low impedance mismatch...
The pathological or physiological changes of the crystalline lens directly affect the eye accommodation and transmittance, and then increase the risk of the presbyopia and cataract for people in middle and old age groups. There is no universally accepted quantitative method to measure the lens' mechanical properties in vivo so far. This study aims to investigate the possibility of assessing the age-related...
The availability of better air-coupled transducers have made possible many different applications. In particular, air-coupled ultrasound is a good solution for the inspection/study of flat/plate materials than can not be wetted by working in through transmission, but experience some problems with curved surfaces. Another successful application is for the generation/reception of Lamb waves using the...
The pathological or physiological changes of the crystalline lens directly affect the eye accommodation and transmittance, and then increase the risk of the presbyopia and cataract for people in middle and old age groups. This risk has a remarkable rise with age, seriously influencing the living quality of the elderly, and also posing a huge burden on public health. There is no universally accepted...
A double-curved diverging lens over a flat row-column-addressed (RCA) 2-D array can extend its inherent rectilinear 3-D imaging field-of-view (FOV) to a curvilinear volume region, which is necessary for applications such as abdominal and cardiac imaging. A concave lens with radius of 12.7 mm was manufactured using RTV664 silicone. The diverging properties of the lens were evaluated based on measurements...
In this work, we present the development of a low-cost, 10 mm diameter histotripsy transducer with co-registered imaging using a 45 MHZ, 64-element phased array. The construction of 10 mm diameter transducer consisting of a 45% volume fraction composite, aluminum lens, and quarter-wavelength parylene matching layer is outlined. Steady-state peak-to-peak pressure ranges from 3.0 to 10.6 MPa as drive...
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...
In this paper, we report the development of miniaturized forward-looking transducers for microbubble-mediated intravascular ultrasound-enhanced thrombolysis (UET). UET has shown its efficacy for thrombo-occlusive disease by enhancing penetration of thrombolytic drugs into clots, reducing the required dose. In this study, we adopted a previously-developed forward-looking, stacked type transducer for...
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