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Mechanisms for permeability enhancement using contrast ultrasound are not fully understood, although the successful use of contrast agents for drug and gene delivery has been demonstrated. Here, we aim to elucidate mechanisms for vascular permeability enhancement by directly observing microbubble contrast agents in a tissue-like gel phantom. The phantom used in these experiments allows us to flow...
Understanding the interaction of acoustically activated microbubbles with small blood vessels is important for designing better imaging schemes, and for targeting and drug delivery applications. To understand the fundamental mechanisms of this interaction, high-speed microscopy was used to observe microbubble dynamics in microvessels of ex vivo rat mesenteries exposed to a single pulse of ultrasound...
In this design, an Ambric's Massively Parallel Processor Array (MPPA), which includes 336 asynchronous processors and communicates through a configurable structure of channels with a 128-bit high speed (100MHz) Input/Output (I/O) port, is used to implement the 64-channel digital beamformer. Besides the beamformer, the system is composed of 256-channel analog front-end pulser/receiver, 64-channel of...
A new method for dynamic elastography of heterogeneous media based on shear wave induction of resonance is proposed. When a confined heterogeneity is excited by a properly selected shear wave at its eigenfrequencies, resonance phenomena appear. The corresponding eigenmodes have the property to be confined into the heterogeneity allowing its discrimination from displacement maps. This phenomenon was...
The field of tissue engineering requires improved methods to monitor tissue growth and function as well as the degradation of biomaterial scaffolds following implantation. Invasive methods of monitoring, such as histology or direct mechanical measurements, are less than ideal. Non-invasive imaging techniques, such as magnetic resonance imaging (MRI), X-ray computed tomography (CT) or conventional...
In this paper, an approach for the extraction of quantitative parameters from multi-directional ultrasound echo signal data for the differentiation and characterization of specular reflections and diffuse backscattering is presented and evaluated. Spatially resolved, tissue-characterizing parametric images are calculated by analyzing the envelope of echo signals from different insonation angles. Frames...
A piezoelectric ultrasonic hydrophone array was fabricated using diaphragm transducer on Si substrates. A two dimensional (2-D) array of 8 times 8 elements with diaphragm transducer has been developed by XeF2 etching from the topside of Si. In this paper, we describe the fabrication process of the diaphragm transducer array. A finite-element analysis (FEA) was calculated to evaluate the resonant frequency...
This paper presents a theoretical analysis of charge effects in silicon nitride membranes in Capacitive Micromachined Ultrasonic Transducers (CMUTs) working at 30 MHz in air. The analysis was motivated by observations of drift in the resonance frequency to the CMUTs during electrical and heterodyne interferometric measurements while keeping the DC voltage level constant over time. After applying a...
A proton-exchanged layer with an elastically soft property can be buried into a substrate by a reverse proton exchange (RPE) process. It is expected that the RPE layer with a property similar to that of bulk LiNbO3 (LN) will prevent the degradation of the coupling factor and that the buried PE layer will reduce the leaky SAW (LSAW) attenuation. In this study, first, a layered structure of air/bulk...
Although a hammer method was used as a shear sound source, the axial resolution (about 0.5 m) was difficult to improve. Therefore, to improve the axial resolution, we newly introduce a shear sound source using super-magnetostriction vibrator and pulse compression method. From the simulation results, when Deltaf (the difference between start and stop frequency) is more than 700 Hz, the axial resolution...
In the present study, Several 4.5 MHz LFE devices with different electrode configurations, including the dual-gap electrode, single-turn Archimedes spiral electrode, two-turn Archimedes spiral electrode and two-turn symmetric spiral electrode, were fabricated and tested. A common LFE device with the single-gap electrode is also fabricated for comparing their performances. A major resonance peak was...
We introduce a systematic design flow consisting of two main stages for ultrasonic signal compression. The first stage of the algorithm is concerned with finding the maximum energy compaction. This is accomplished by finding an optimal subband decomposition tree structure for a particular combination of a wavelet kernel and the experimental input data. The second stage of the algorithm is concerned...
Nanoparticle patterning on a vibrating solid surface according to the vibration modes of the solid is the result of extremely high solid surface acceleration and persistent flow beyond the steady boundary layer. The solid surface acceleration magnitude increased proportionally to the square of vibration angular frequency. The tens-of-megahertz frequency cause the surface acceleration to reach to an...
The optically assisted ultrasonic velocity-change imaging method was applied to obtain the spectroscopic image of nano-particles, which were expected as markers for drug delivery system and photo-thermal therapy, in tissue mimic phantoms. Phantoms including gold nano-rods or semiconductor nano-particles were prepared. The ultrasonic velocity-change images of phantoms were obtained using illumination...
A porous aluminium plate with a regular columnar microstructure exhibits unusual properties when interacting with high frequency acoustic waves. Finite element modeling reproduces this behaviour and a more detailed analysis explains the underlying physics.
Application of ultrasound (US) has been demonstrated as an effective way to realize thrombus dissolution. Cavitation is hypothesized to be an important mechanism of US thrombolysis, but the relationship between quantified cavitation and thrombolysis efficiency has not been studied extensively. The purpose of this work was to study focused US thrombolysis feasibility and the relationship between cavitation...
The 4 GHz bulk acoustic wave (BAW) resonators have been fabricated by thin films of Pb(Zr,Ti)O3 based ternary perovskite compounds. The Pb(Mn1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMnN-PZT) thin films were deposited on (100)MgO substrates by RF magnetron sputtering. The PMnN-PZT thin films showed tetragonal crystal structure and highly (001) orientation. The surface roughness of the thin films was about 2 nm. The...
This paper describes the development of an interdigital bonded (IB) 1-3 composite for use in a 30MHz 256-element geometrically focused ultrasonic array. The composite was manufactured using two IB operations in the elevation direction and one IB operation as well as one additional dicing step in the azimuth direction. The resultant composite elements had 14mum x 19mum wide posts separated by 8mum...
This article concerns the design of a new electrostatic transducer whose backplate consists of a series of drilled pipes. A new one-dimensional model is derived which considers the interaction of the membrane with the air load, the air cavities, and the drilled pipes in the backplate. Dynamic equations for the impedance in each component of the device are calculated analytically and connected using...
Plunging of metal pin or shaft into small hole inducing longitudinal vibration on static plunging force is studied. When inserting pin or shaft using only static force, the material with holes happen to broken by plunging pin by large static force and also the motor shaft plunged into the rotor center has inevitably eccentricity and must to adjust the eccentricity by manual or some machines. Using...
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