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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 10 • Date October 2012

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Displaying Results 1 - 25 of 32
  • IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control - cover

    Page(s): c1 - c2
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  • IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society - Administrative Committee

    Page(s): c3
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  • IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society - Elected Administrative Committee

    Page(s): c4
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  • Table of contents

    Page(s): i - iii
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  • Information for contributors with multimedia addition

    Page(s): 2117 - 2120
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  • Electrical properties and impedance spectroscopy of pure and copper-oxide-added potassium sodium niobate ceramics

    Page(s): 2121 - 2128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (924 KB) |  | HTML iconHTML  

    Pure and 1 mol% CuO-added lead-free potassium sodium niobate K0.5Na0.5NbO3 (KNN) ceramics were prepared by the conventional solid-state calcination method. Copper oxide was mainly used as a sintering aid in the KNN structure. Microstructural analyses clearly showed that the CuO formed a secondary phase at the grain boundaries. Impedance spectroscopy was used as a tool to analyze the electrical behavior of KNN ceramics as a function of frequency from 100 Hz to 10 MHz at various temperatures. The impedance studies proved that CuO led to the formation of a secondary grain boundary phase, as well as creation of highly mobile point defects. The relaxation time of copper-added samples was less than that of pure KNN. This shorter time indicated a higher space charge mobility for CuO-added samples. The thermal activation energy for relaxation of charge carriers (Eg) was calculated as 0.73 eV for CuO-added samples. View full abstract»

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  • Power enhancement of piezoelectric transformers by adding heat transfer equipment

    Page(s): 2129 - 2136
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    It is known that piezoelectric transformers have several inherent advantages compared with conventional electromagnetic transformers. However, the maximum power capacity of piezoelectric transformers is not as large as electromagnetic transformers in practice, especially in the case of high output current. The theoretical power density of piezoelectric transformers calculated by stress boundary can reach 330 W/cm3, but no piezoelectric transformer has ever reached such a high power density in practice. The power density of piezoelectric transformers is limited to 33 W/cm3 in practical applications. The underlying reason is that the maximum passing current of the piezoelectric material (mechanical current) is limited by the temperature rise caused by heat generation. To increase this current and the power capacity, we proposed to add a thermal pad to the piezoelectric transformer to dissipate heat. The experimental results showed that the proposed techniques can increase by 3 times the output current of the piezoelectric transformer. A theoretical-phenomenological model which explains the relationship between vibration velocity and generated heat is also established to verify the experimental results. View full abstract»

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  • Active suppression of a beam under a moving mass using a pointwise fiber bragg grating displacement sensing system

    Page(s): 2137 - 2148
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    This paper investigates active vibration control of a beam under a moving mass using a pointwise fiber Bragg grating (FBG) displacement sensing system. Dynamic responses of the proposed FBG displacement sensor are demodulated with an FBG filter and verified with measurement results obtained from a noncontact fiber-optic displacement sensor. System identification of the beam is first performed with a piezoceramic actuator and positive position feedback (PPF) controllers are designed based on the identified results. Then, transient responses of the beam under a moving mass with different moving conditions are measured using the FBG displacement sensor. A high-speed camera is used to detect the speed of the moving mass for further discussions about its influence on the transient response. Finally, active vibration control of the beam under the moving mass is performed and fast Fourier transform (FFT) as well as short-time Fourier transform (STFT) are employed to demonstrate control performances. For the case in which a rolling steel ball is directed from a slide to the beam to generate the moving mass, reductions of the vibration up to 50% and 60% are achieved in the frequency domain for the first and second modes of the beam, respectively. Based on the control experiments on the small-scale beam, results in this work show that the proposed FBG displacement sensing system can be used in research on the moving mass problem. View full abstract»

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  • Optimizing frequency and pulse shape for ultrasound current source density imaging

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    Electric field mapping is commonly used to identify irregular conduction pathways in the heart (e.g., arrhythmia) and brain (e.g., epilepsy). Ultrasound current source density imaging (UCSDI), based on the acoustoelectric (AE) effect, is a promising new technique for mapping electrical current in four dimensions with enhanced resolution. The frequency and pulse shape of the ultrasound beam affect the sensitivity and spatial resolution of UCSDI. In this study, we explore the effects of ultrasound transducer frequency bandwidth and coded excitation pulses for UCSDI and the inherent tradeoff between sensitivity and spatial resolution. We used both simulations and bench-top experiments to image a time-varying electrical dipole in 0.9% NaCl solution. To study the effects of ultrasound bandwidth, we chose two ultrasound transducers with different center frequencies (1.0 and 2.25 MHz). For coded excitation, we measured the AE voltage signal with different chirp excitations. As expected, higher bandwidth correlated with improved spatial resolution at the cost of sensitivity. On the other hand, chirp excitation significantly improved sensitivity (3.5 μV/mA) compared with conventional square pulse excitation (1.6 μV/mA) at 1 MHz. Pulse compression achieved spatial resolution similar to that obtained using square pulse excitation, demonstrating enhanced detection sensitivity without loss of resolution. Optimization of the time duration of the chirp pulse and frequency sweep rate can be further used to improve the quality of UCSDI. View full abstract»

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  • Intravascular ultrasound catheter to enhance microbubble-based drug delivery via acoustic radiation force

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    Previous research has demonstrated that acoustic radiation force enhances intravascular microbubble adhesion to blood vessels in the presence of flow for molecular-targeted ultrasound imaging and drug delivery. A prototype acoustic radiation force intravascular ultrasound (ARFIVUS) catheter was designed and fabricated to displace a microbubble contrast agent in flow representative of conditions encountered in the human carotid artery. The prototype ARFIVUS transducer was designed to match the resonance frequency of 1.4- to 2.6-μm-diameter microbubbles modeled by an experimentally verified 1-D microbubble acoustic radiation force translation model. The transducer element was an elongated Navy Type I (hard) lead zirconate titanate (PZT) ceramic designed to operate at 3 MHz. Fabricated devices operated with center frequencies of 3.3 and 3.6 MHz with -6-dB fractional bandwidths of 55% and 50%, respectively. Microbubble translation velocities as high as 0.86 m/s were measured using a high-speed streak camera when insonating with the ARFIVUS transducer. Finally, the prototype was used to displace microbubbles in a flow phantom while imaging with a commercial 45-MHz imaging IVUS transducer. A sustained increase of 31 dB in average video intensity was measured following insonation with the ARFIVUS, indicating microbubble accumulation resulting from the application of acoustic radiation force. View full abstract»

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  • Real-time 1-D/2-D transient elastography on a standard ultrasound scanner using mechanically induced vibration

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    Transient elastography has been well established in the literature as a means of assessing the elasticity of soft tissue. In this technique, tissue elasticity is estimated from the study of the propagation of the transient shear waves induced by an external or internal source of vibration. Previous studies have focused mainly on custom single-element transducers and ultrafast scanners which are not available in a typical clinical setup. In this work, we report the design and implementation of a transient elastography system on a standard ultrasound scanner that enables quantitative assessment of tissue elasticity in real-time. Two new custom imaging modes are introduced that enable the system to image the axial component of the transient shear wave, in response to an externally induced vibration, in both 1-D and 2-D. Elasticity reconstruction algorithms that estimate the tissue elasticity from these transient waves are also presented. Simulation results are provided to show the advantages and limitations of the proposed system. The performance of the system is also validated experimentally using a commercial elasticity phantom. View full abstract»

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  • Applying Thomson's multitaper approach to reduce speckle in medical ultrasound imaging

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1714 KB) |  | HTML iconHTML  

    To reduce the variance of speckle in coherent imaging systems, one must average images with different speckle realizations. Traditionally, these images have been formed by observing the target region from slightly different angles (spatial compounding) or by varying the involved temporal frequencies (frequency compounding). In this paper, we investigate a third option based on Thomson's multitaper approach to power spectrum estimation. The tapers are applied spatially, as array weights. Our investigations, based on both recorded ultrasound data and simulations, verify that the multitaper approach can be used for speckle reduction at a rate comparable to that of the more traditional method of spatial compounding. Because of the spectral concentration of the tapers, an added benefit is reduced side lobe levels, which can result in steeper edges and better definition of cyst-like structures. View full abstract»

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  • Ultrasound time-reversal MUSIC imaging with diffraction and attenuation compensation

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    Time-reversal imaging with multiple signal classification (TR-MUSIC) is an algorithm for imaging point-like scatterers embedded in a homogeneous and non-attenuative medium. We generalize this algorithm to account for the attenuation in the medium and the diffraction effects caused by the finite size of the transducer elements. The generalized algorithm yields higher-resolution images than those obtained with the original TR-MUSIC algorithm. We evaluate the axial and lateral resolutions of the images obtained with the generalized algorithm when noise corrupts the recorded signals and show that the axial resolution is degraded more than the lateral resolution. The TR-MUSIC algorithm is valid only when the number of point-like targets in the imaging plane is fewer than the number of transducer elements used to interrogate the medium. We remedy this shortcoming by dividing the imaging plane into subregions and applying the TR-MUSIC algorithm to the windowed backscattered signals corresponding to each subregion. The images of all subregions are then combined to form the total image. Imaging results of numerical and phantom data show that when the number of scatterers within each subregion is much smaller than the number of transducer elements, the windowing method yields super-resolution images with accurate scatterer localization. We use computer simulations and tissue-mimicking phantom data acquired with a real-time synthetic-aperture ultrasound system to illustrate the algorithms presented in the paper. View full abstract»

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  • An open system for intravascular ultrasound imaging

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (779 KB) |  | HTML iconHTML  

    Visualization of the blood vessels can provide valuable morphological information for diagnosis and therapy strategies for cardiovascular disease. Intravascular ultrasound (IVUS) is able to delineate internal structures of vessel wall with fine spatial resolution. However, the developed IVUS is insufficient to identify the fibrous cap thickness and tissue composition of atherosclerotic lesions. Novel imaging strategies have been proposed, such as increasing the center frequency of ultrasound or using a modulated excitation technique to improve the accuracy of diagnosis. Dual-mode tomography combining IVUS with optical tomography has also been developed to determine tissue morphology and characteristics. The implementation of these new imaging methods requires an open system that allows users to customize the system for various studies. This paper presents the development of an IVUS system that has open structures to support various imaging strategies. The system design is based on electronic components and printed circuit board, and provides reconfigurable hardware implementation, programmable image processing algorithms, flexible imaging control, and raw RF data acquisition. In addition, the proposed IVUS system utilized a miniaturized ultrasound transducer constructed using PMNPT single crystal for better piezoelectric constant and electromechanical coupling coefficient than traditional lead zirconate titanate (PZT) ceramics. Testing results showed that the IVUS system could offer a minimum detectable signal of 25 μV, allowing a 51 dB dynamic range at 47 dB gain, with a frequency range from 20 to 80 MHz. Finally, phantom imaging, in vitro IVUS vessel imaging, and multimodality imaging with photoacoustics were conducted to demonstrate the performance of the open system. View full abstract»

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  • Aberration compensation of an ultrasound imaging instrument with a reduced number of channels

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    Focusing and imaging qualities of an ultrasound imaging system that uses aberration correction were experimentally investigated as functions of the number of parallel channels. Front-end electronics that consolidate signals from multiple physical elements can be used to lower hardware and computational costs by reducing the number of parallel channels. However, the signals from sparse arrays of synthetic elements yield poorer aberration estimates. In this study, aberration estimates derived from synthetic arrays of varying element sizes are evaluated by comparing compensated receive focuses, compensated transmit focuses, and compensated b-scan images of a point target and a cyst phantom. An array of 80 × 80 physical elements with a pitch of 0.6 × 0.6 mm was used for all of the experiments and the aberration was produced by a phantom selected to mimic propagation through abdominal wall. The results show that aberration correction derived from synthetic arrays with pitches that have a diagonal length smaller than 70% of the correlation length of the aberration yield focuses and images of approximately the same quality. This connection between correlation length of the aberration and synthetic element size provides a guideline for determining the number of parallel channels that are required when designing imaging systems that employ aberration correction. View full abstract»

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  • Scale transform signal processing for optimal ultrasonic temperature compensation

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    In structural health monitoring, temperature compensation is an important step to reduce systemic errors and avoid false-positive results. Several methods have been developed to accomplish temperature compensation in guided wave systems, but these techniques are often limited in computational speed. In this paper, we present a new methodology for optimal, stretch-based temperature compensation that operates on signals in the stretch factor and scale-transform domains. Using these tools, we demonstrate three algorithms for temperature compensation that show improved computational speed relative to other optimal methods. We test the performance of these algorithms using experimental guided wave data. View full abstract»

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  • Narrowband ultrasonic detection with high range resolution: separating echoes via compressed sensing and singular value decomposition

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    It is well known that broader bandwidth leads to higher range resolution, but in ultrasonic flaw detection, the bandwidth is often limited. That is, the upper frequency of the transmitted signal is bounded by the attenuation of highfrequency ultrasound, especially when the penetration depth is large. In this case, only the band-limited signals are suitable for far-field detection. Fortunately, theoretical analysis in this paper shows that narrowband detection has greater potential for obtaining high range resolution compared with broadband detection. However, it is difficult to fully utilize this potential because of the severe overlap of narrowband echoes. As a result, we propose a novel approach for separating highly overlapping narrowband echoes in this paper to improve the resolution of range imaging. In our approach, in addition to a formulation following the emerging theory of sparse representation and compressed sensing, singular value decomposition is also employed to capture the main features of the signals, making this approach robust to moderate signal distortions. Numerous simulations and experiments on real data show that the proposed approach is able to fully utilize the potential of narrowband detection and outperforms other competitive methods in terms of stability and accuracy. View full abstract»

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  • A polyimide-etalon thin film structure for all-optical high-frequency ultrasound transduction

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (614 KB) |  | HTML iconHTML  

    In this work, we have designed, fabricated, and tested an all-optical ultrasound transducer by integrating a photoabsorptive polyimide thin film into a Fabry-Pérot (etalon) high-frequency receiver. A 5-ns UV pulse was used for thermoelastic ultrasound generation in the polyimide film, and the transmission had a maximum amplitude of 4.3 MPa centered at 27 MHz with a fractional bandwidth of 107%. The device attained a noise-equivalent pressure of 1.3 Pa/ Hz in receive-only mode. When used in pulse-echo mode, the -6-dB upper cutoff frequency of the transmit/receive response reached 47 MHz. Basic imaging capabilities were also investigated by scanning the near-infrared probe beam across the device to create a 2 × 2 mm synthetic aperture. The imaging of targets placed at depths of 1.8 and 5.2 mm yielded estimates of 71 and 145 μm, respectively, for the lateral resolution and 35 and 38 μm, respectively, for the axial resolution. Finally, a design concept for a forward-viewing intravascular imager is presented that entails the coupling of light to a rotating, linear array of optical fibers on top of which are deposited polyimide- etalon transducers. Such a design would allow for a flexible and compact high-resolution imager well-suited for intravascular applications, such as guidance of treatment in the case of chronic total occlusion. View full abstract»

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  • Acoustically coupled thickness-mode AIN-on-Si band-pass filters-part I: principle and devices

    Page(s): 2262 - 2269
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    In this, the first of two papers, we present the working principle and the implementation of laterally acoustically coupled thickness-mode thin-film piezoelectric-on-substrate (TPoS) filters. This type of filter offers low insertion loss and small bandwidth in a broad frequency range- from a few hundred megahertz up to a few gigahertz-and occupy a small chip area. In this paper, we discuss several design concerns, including the choice of materials for TPoS filters. We demonstrate a design for an air-suspended AlN-on-Si filter, which offers a low insertion loss of 2.4 dB at 2.877 GHz. The bandwidth of this filter is 12 MHz with a return loss of better than 30 dB. In Part II of this paper, we present a comprehensive analysis of the effect of physical layout parameters on the frequency response of TPoS filters. View full abstract»

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  • Acoustically coupled thickness-mode AIN-on-Si band-pass filters-Part II: simulation and analysis

    Page(s): 2270 - 2277
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    In this, the second of two papers, we present numerical simulations and comprehensive analysis of acoustically coupled thickness-mode AlN-on-Si filters. We simulate the scattering parameters of such acoustically coupled filters using commercially available finite element analysis software and compare the simulation results with a set of measurements. The simulations are in good agreement with the measurements, allowing the optimization of filter characteristics. We analyze the filter response under varying geometric parameters and demonstrate that variations in the top electrode geometry allow the design of low-loss filters (insertion loss <;5 dB) with percentage bandwidth up to about 1% and ripple less than 1 dB. View full abstract»

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  • The fifth-order overtone vibrations of quartz crystal plates with corrected higher-order mindlin plate equations

    Page(s): 2278 - 2291
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    Higher-order overtone resonators have been widely used in various electronic products for their higher vibration frequencies, which are in the much-needed frequency range beyond the reach of the fundamental mode. However, the existing designs of higher-order overtone resonators and further improvement for meeting more precise requirements are largely based on empirical approaches. As an analytical effort, we have derived the corrected fifth-order Mindlin plate equations with the consideration of electric potential and overtone displacements. The elimination and truncation of the infinite two-dimensional equations has been done to ensure the exact cut-off frequencies of the fundamental, the third-order overtone, and fifth-order overtone thickness-shear modes in comparison with the three-dimensional equations. The frequency spectra are plotted in the vicinity of overtone thickness-shear modes for analysis of couplings and interactions with spurious modes, and the optimal design of quartz crystal blanks for overtone vibrations has been suggested. The equations, solutions, and method will be important in design of the higher-order overtone thickness-shear vibration resonators. View full abstract»

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  • Modeling the measurement of ultrasonic beams transmitted through a penetrable acoustic cone

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    The interaction of ultrasonic beams with conical scatterers is governed by a combination of diffraction effects occurring at the aperture of the acoustic source/receiver and refraction through the cone. Accordingly, the outcome of a transmission experiment is dependent upon the many physical parameters characterizing the transducers and the cone. We develop a simplified model which describes the deflection caused by refraction through the cone using ray theory, then uses Huygens' summation to calculate the transducer response from this deflection. The model's accuracy is verified by comparison to simulated data. The model shows that transmission occurs in two different regimes, depending on the parameters of the particular problem. In the first regime, the cone alters the spatial phase distribution of the incident field along the receiver's aperture, whereas its amplitude remains almost unchanged. Because the receiver integrates the field over the aperture, the phasing affects the measurements via constructive and destructive interference. In the second regime, the phase alteration is accompanied by large amplitude variations around an average value that is significantly smaller than the amplitude observed in the first regime. The approximation will aid the design of ultrasound tomography arrays, such as those being developed for breast cancer detection. View full abstract»

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  • Bragg waveguide ultrasound detectors

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    Polymer Bragg grating waveguides (BGWs) are demonstrated as ultrasound detectors. The device is fabricated by a direct electron beam lithography technique using an epoxy-based photoresist as the core material, with grating features fabricated on the side walls of the rib waveguide. The main motivation for this design is the linear geometry of the device, which can be used in a linear array, facilitating high-frequency ultrasound imaging. The fabricated BGW device has a cross-sectional area of 1.5 × 1.5 μm and the grating length is 500 μm. The optical resonance spectrum is measured and compared with a theoretical model. The BGW device is experimentally demonstrated for the detection of ultrasound waves emitted by a 25-MHz transducer. Detection sensitivity depends on optimal grating design for a steep resonance. The extension of a single-element BGW device to a linear array using optical wavelength division multiplexing is presented. The results demonstrate the potential use of BGW devices in highly compact array of optoacoustic detectors for high-sensitivity ultrasound detection and photoacoustic imaging. View full abstract»

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  • Crosstalk reduction for high-frequency linear-array ultrasound transducers using 1-3 piezocomposites with pseudo-random pillars

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    The goal of this research was to develop a novel diced 1-3 piezocomposite geometry to reduce pulse-echo ring down and acoustic crosstalk between high-frequency ultrasonic array elements. Two PZT-5H-based 1-3 composites (10 and 15 MHz) of different pillar geometries [square (SQ), 45° triangle (TR), and pseudo-random (PR)] were fabricated and then made into single-element ultrasound transducers. The measured pulse-echo waveforms and their envelopes indicate that the PR composites had the shortest -20-dB pulse length and highest sensitivity among the composites evaluated. Using these composites, 15-MHz array subapertures with a 0.95λ pitch were fabricated to assess the acoustic crosstalk between array elements. The combined electrical and acoustical crosstalk between the nearest array elements of the PR array subapertures (-31.8 dB at 15 MHz) was 6.5 and 2.2 dB lower than those of the SQ and the TR array subapertures, respectively. These results demonstrate that the 1-3 piezocomposite with the pseudo-random pillars may be a better choice for fabricating enhanced high-frequency linear-array ultrasound transducers; especially when mechanical dicing is used. View full abstract»

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  • Thin-film sparse boundary array design for passive acoustic mapping during ultrasound therapy

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    A new 2-D hydrophone array for ultrasound therapy monitoring is presented, along with a novel algorithm for passive acoustic mapping using a sparse weighted aperture. The array is constructed using existing polyvinylidene fluoride (PVDF) ultrasound sensor technology, and is utilized for its broadband characteristics and its high receive sensitivity. For most 2-D arrays, high-resolution imagery is desired, which requires a large aperture at the cost of a large number of elements. The proposed array's geometry is sparse, with elements only on the boundary of the rectangular aperture. The missing information from the interior is filled in using linear imaging techniques. After receiving acoustic emissions during ultrasound therapy, this algorithm applies an apodization to the sparse aperture to limit side lobes and then reconstructs acoustic activity with high spatiotemporal resolution. Experiments show verification of the theoretical point spread function, and cavitation maps in agar phantoms correspond closely to predicted areas, showing the validity of the array and methodology. View full abstract»

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Aims & Scope

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control focuses on the theory, design, and application on generation, transmission, and detection of bulk and surface mechanical waves.

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Editor-in-Chief
Steven Freear
s.freear@leeds.ac.uk