WorldWideScience

Sample records for convex ultrasound transducer

  1. Calibration of Field II using a Convex Ultrasound Transducer

    DEFF Research Database (Denmark)

    Bæk, David; Jensen, Jørgen Arendt; Willatzen, Morten

    2010-01-01

    Field II is an ultrasound simulation program capable of simulating the pressure scattering from inhomogeneous tissue. The simulations are based on a convolution between spatial impulse responses from the field in front of the transducer and the volt-to-surface acceleration impulse response...... of the transducer. For such simulations to reflect actual measured intensities and pressure levels, the transducer impulse response is to be known. This work presents the results of combining a modified form of a 1D linear transducer model originally suggested by Willatzen with the Field II program to calibrate...... BK-Medical (Herlev, Denmark). As input waveform for the Field model we measured the output voltage of the research amplifier, which peak voltage was limited to 31 V to avoid too high non linear effects. We measured the hydrophone output from three transducer front elements by averaging 40 shoot...

  2. Modeling of ultrasound transducers

    DEFF Research Database (Denmark)

    Bæk, David

    deviation of 5.5 % to 11.0 %. Finite element modeling of piezoceramics in combination with Field II is addressed and reveals the influence of restricting the modeling of transducers to the one-dimensional case. An investigation on modeling capacitive micromachined ultrasonic transducers (CMUT)s with Field......This Ph.D. dissertation addresses ultrasound transducer modeling for medical ultrasound imaging and combines the modeling with the ultrasound simulation program Field II. The project firstly presents two new models for spatial impulse responses (SIR)s to a rectangular elevation focused transducer...... II is addressed. It is shown how a single circular CMUT cell can be well approximated with a simple square transducer encapsulating the cell, and how this influence the modeling of full array elements. An optimal cell discretization with Field II’s mathematical elements is addressed as well...

  3. Ultrasound transducer assembly and method for manufacturing an ultrasound transducer assembly

    NARCIS (Netherlands)

    Dekker, R.; Henneken, V.A.; Louwerse, M.C.; Raganato, M.F.

    2015-01-01

    The present invention relates to an ultrasound transducer assembly (10), in particular for intravascular ultrasound systems. The ultrasound transducer assembly comprises at least one silicon substrate element (30) including an ultrasound transducer element (14) for emitting and receiving ultrasound

  4. Ultrasound transducer assembly and method for manufacturing an ultrasound transducer assembly

    NARCIS (Netherlands)

    Dekker, R.; Henneken, V.A.; Louwerse, M.C.; Raganato, M.F.

    2015-01-01

    The present invention relates to an ultrasound transducer assembly (10), in particular for intravascular ultrasound systems. The ultrasound transducer assembly comprises at least one silicon substrate element (30) including an ultrasound transducer element (14) for emitting and receiving ultrasound

  5. Parameter sensitivity study of a Field II multilayer transducer model on a convex transducer

    DEFF Research Database (Denmark)

    Bæk, David; Jensen, Jørgen Arendt; Willatzen, Morten

    2009-01-01

    .ResultsPredictions using the ZR give a pressure pulse error (PPE) and an intensity error (IE) of 32 % and 23 %, respectively, relative to the measured. Altering the piezoelectric permittivity +12 % from ZR decreases the PPE to 30 % and the IE to 2 % relative to the measured. Changing the stiffness constant of the lens -4......A multilayer transducer model for predicting a transducer impulse response has in earlier works been developed and combined with the Field II software. This development was tested on current, voltage, and intensity measurements on piezoceramics discs (Bæk et al. IUS 2008) and a convex 128 element...... ultrasound imaging transducer (Bæk et al. ICU 2009). The model benefits from its 1D simplicity and hasshown to give an amplitude error around 1.7‐2 dB. However, any prediction of amplitude, phase, and attenuation of pulses relies on the accuracy of manufacturer supplied material characteristics, which may...

  6. Transducer for harmonic intravascular ultrasound imaging

    NARCIS (Netherlands)

    Vos, Hendrik J.; Frijlink, Martijn E.; Droog, E.J.; Goertz, David E.; Blacquiere, Gerrit; Gisolf, Anton; de Jong, N.; van der Steen, Antonius F.W.

    2005-01-01

    A recent study has shown the feasibility of tissue harmonic imaging (THI) using an intravascular ultrasound (IVUS) transducer. This correspondence describes the design, fabrication, and characterization of a THI-optimized piezoelectric transducer with oval aperture of 0.75 mm by 1 mm. The transducer

  7. Micromachined Integrated Transducers for Ultrasound Imaging

    DEFF Research Database (Denmark)

    la Cour, Mette Funding

    The purpose of this project is to develop capacitive micromachined ultrasonic transducers (CMUTs) for medical imaging. Medical ultrasound transducers used today are fabricated using piezoelectric materials and bulk processing. To fabricate transducers capable of delivering a higher imaging...... project and collaboration with a lot of partners to improve medical ultrasound imaging. The focus in this part of the project is to design, fabricate and characterize 1D CMUT arrays. Two versions of 1D transducers are made, one at Stanford University and one at DTU. Electrical and acoustical...... resolution it is however necessary to develop new fabrication methods that allows fabrication of transducer elements with smaller dimensions. By using microfabrication technology it is possible to push the dimensions down and provide higher design flexibility. This project is part of a large ultrasound...

  8. Glass-windowed ultrasound transducers.

    Science.gov (United States)

    Yddal, Tostein; Gilja, Odd Helge; Cochran, Sandy; Postema, Michiel; Kotopoulis, Spiros

    2016-05-01

    In research and industrial processes, it is increasingly common practice to combine multiple measurement modalities. Nevertheless, experimental tools that allow the co-linear combination of optical and ultrasonic transmission have rarely been reported. The aim of this study was to develop and characterise a water-matched ultrasound transducer architecture using standard components, with a central optical window larger than 10 mm in diameter allowing for optical transmission. The window can be used to place illumination or imaging apparatus such as light guides, miniature cameras, or microscope objectives, simplifying experimental setups. Four design variations of a basic architecture were fabricated and characterised with the objective to assess whether the variations influence the acoustic output. The basic architecture consisted of a piezoelectric ring and a glass disc, with an aluminium casing. The designs differed in piezoelectric element dimensions: inner diameter, ID=10 mm, outer diameter, OD=25 mm, thickness, TH=4 mm or ID=20 mm, OD=40 mm, TH=5 mm; glass disc dimensions OD=20-50 mm, TH=2-4 mm; and details of assembly. The transducers' frequency responses were characterised using electrical impedance spectroscopy and pulse-echo measurements, the acoustic propagation pattern using acoustic pressure field scans, the acoustic power output using radiation force balance measurements, and the acoustic pressure using a needle hydrophone. Depending on the design and piezoelectric element dimensions, the resonance frequency was in the range 350-630 kHz, the -6 dB bandwidth was in the range 87-97%, acoustic output power exceeded 1 W, and acoustic pressure exceeded 1 MPa peak-to-peak. 3D stress simulations were performed to predict the isostatic pressure required to induce material failure and 4D acoustic simulations. The pressure simulations indicated that specific design variations could sustain isostatic pressures up to 4.8 MPa.The acoustic simulations were able to

  9. Ultrasound transducer selection in clinical imaging practice.

    Science.gov (United States)

    Szabo, Thomas L; Lewin, Peter A

    2013-04-01

    Many types of medical ultrasound transducers are used in clinical practice. They operate at different center frequencies, have different physical dimensions, footprints, and shapes, and provide different image formats. However, little information is available about which transducers are most appropriate for a given application, and the purpose of this article is to address this deficiency. Specifically, the relationship between the transducer, imaging format, and clinical applications is discussed, and systematic selection criteria that allow matching of transducers to specific clinical needs are presented. These criteria include access to and coverage of the region of interest, maximum scan depth, and coverage of essential diagnostic modes required to optimize a patient's diagnosis. Three comprehensive figures organize and summarize the imaging planes, scanning modes, and types of diagnostic transducers to facilitate their selection in clinical diagnosis.

  10. Design considerations for piezoelectric polymer ultrasound transducers.

    Science.gov (United States)

    Brown, L F

    2000-01-01

    Much work has been published on the design of ultrasound transducers using piezoelectric ceramics, but a great deal of this work does not apply when using the piezoelectric polymers because of their unique electrical and mechanical properties. The purpose of this paper is to review and present new insight into seven important considerations for the design of active piezoelectric polymer ultrasound transducers: piezoelectric polymer materials selection, transducer construction and packaging requirements, materials characterization and modeling, film thickness and active area design, electroding selection, backing material design, and front protection/matching layer design. Besides reviewing these design considerations, this paper also presents new insight into the design of active piezoelectric polymer ultrasonic transducers. The design and fabrication of an immersible ultrasonic transducer, which has no adhesive layer between the active element and backing layer, is included. The transducer features direct deposition of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer onto an insulated aluminum backing substrate. Pulse-echo tests indicated a minimum insertion loss of 37 dB and -6 dB bandwidth of 9.8 to 22 MHz (71%). The use of polymer wear-protection/quarter-wave matching layers is also discussed. Test results on a P(VDF-TrFE) transducer showed that a Mylar/sup TM/ front layer provided a slight increase in pulse-echo amplitude of 15% (or 1.2 dB) and an increase in -6 dB pulse-echo fractional bandwidth from 86 to 95%. Theoretical derivations are reported for optimizing the active area of the piezoelectric polymer element for maximum power transfer at resonance. These derivations are extended to the special case for a low profile (i.e., thin) shielded transducer. A method for modeling the non-linear loading effects of a commercial pulser-receiver is also included.

  11. New piezoelectric transducers for therapeutic ultrasound.

    Science.gov (United States)

    Chapelon, J Y; Cathignol, D; Cain, C; Ebbini, E; Kluiwstra, J U; Sapozhnikov, O A; Fleury, G; Berriet, R; Chupin, L; Guey, J L

    2000-01-01

    Therapeutic ultrasound (US) has been of increasing interest during the past few years. However, the development of this technique depends on the availability of high-performance transducers. These transducers have to be optimised for focusing and steering high-power ultrasonic energy within the target volume. Recently developed high-power 1-3 piezocomposite materials bring to therapeutic US the exceptional electroacoustical properties of piezocomposite technology: these are high efficiency, large bandwidth, predictable beam pattern, more flexibility in terms of shaping and definition of sampling in annular arrays, linear arrays or matrix arrays. The construction and evaluation of several prototypes illustrates the benefit of this new approach that opens the way to further progress in therapeutic US.

  12. Ultrasonic transducer chip assembly, ultrasound probe, ultrasonic imaging system and ultrasound assembly and probe manufacturing methods

    NARCIS (Netherlands)

    Weekamp, J.W.; Henneken, V.A.; Groenland, A.W.; Louwerse, M.C.

    2015-01-01

    Disclosed is an ultrasonic transducer assembly comprising an ultrasonic transducer chip (100) having a main surface comprising a plurality of ultrasound transducer elements (112) and a plurality of first contacts (120) for connecting to said ultrasound transducer elements; a contact chip (400) havin

  13. Micromachined capacitive transducer arrays for intravascular ultrasound

    Science.gov (United States)

    Degertekin, F. Levent; Guldiken, R. Oytun; Karaman, Mustafa

    2005-01-01

    Intravascular ultrasound (IVUS) imaging has become an essential imaging modality for the effective diagnosis and treatment of cardiovascular diseases during the past decade enabled by innovative applications of piezoelectric transducer technology. The limitations in the manufacture and performance of the same piezoelectric transducers have also impeded the improvement of IVUS for emerging clinically important applications such as forward viewing arrays for guiding interventions and high resolution imaging of arterial structure such as vulnerable plaque and fibrous cap, and also implementation of techniques such as harmonic imaging of the tissue and of the contrast agents. Capacitive micromachined ultrasonic transducer (CMUT) technology shows great potential for transforming IVUS not only to satisfy these clinical needs but also to open up possibilities for low-cost imaging devices integrated to therapeutic tools. We have developed manufacturing processes with a maximum process temperature of 250°C to build CMUTs on the same silicon chip with integrated electronics. Using these processes we fabricated CMUT arrays suitable for forward viewing IVUS in the 10-20MHz range. We characterized these array elements in terms of pulse-echo response, radiation pattern measurements and demonstrated its volumetric imaging capabilities on various imaging targets.

  14. Multilayer Array Transducer for Nonlinear Ultrasound Imaging

    Science.gov (United States)

    Owen, Neil R.; Kaczkowski, Peter J.; Li, Tong; Gross, Dan; Postlewait, Steven M.; Curra, Francesco P.

    2011-09-01

    The properties of nonlinear acoustic wave propagation are known to be able to improve the resolution of ultrasound imaging, and could be used to dynamically estimate the physical properties of tissue. However, transducers capable of launching a wave that becomes nonlinear through propagation do not typically have the necessary bandwidth to detect the higher harmonics. Here we present the design and characterization of a novel multilayer transducer for high intensity transmit and broadband receive. The transmit layer was made from a narrow-band, high-power piezoceramic (PZT), with nominal frequency of 2.0 MHz, that was diced into an array of 32 elements. Each element was 0.300 mm wide and 6.3 mm in elevation, and with a pitch of 0.400 mm the overall aperture width was 12.7 mm. A quarter-wave matching layer was attached to the PZT substrate to improve transmit efficiency and bandwidth. The overlaid receive layer was made from polyvinylidene fluoride (PVDF) that had gold metalization on one side. A custom two-sided flex circuit routed electrical connections to the PZT elements and patterned the PVDF elements; the PZT and PVDF elements had identical apertures. A low viscosity and electrically nonconductive epoxy was used for all adhesion layers. Characterization of electrical parameters and acoustic output were performed per standard methods, where transmit and receive events were driven by a software-controlled ultrasound engine. Echo data, collected from ex vivo tissue and digitized at 45 MS/s, exhibited frequency content up to the 4th harmonic of the 2 MHz transmit frequency.

  15. Piezoelectric micromachined ultrasound transducer (PMUT) arrays for integrated sensing, actuation and imaging

    National Research Council Canada - National Science Library

    Qiu, Yongqiang; Gigliotti, James V; Wallace, Margeaux; Griggio, Flavio; Demore, Christine E M; Cochran, Sandy; Trolier-McKinstry, Susan

    2015-01-01

    .... Piezoelectric micromachined ultrasound transducers (PMUTs), diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays...

  16. Ultrasound transducer function: annual testing is not sufficient.

    Science.gov (United States)

    Mårtensson, Mattias; Olsson, Mats; Brodin, Lars-Åke

    2010-10-01

    The objective was to follow-up the study 'High incidence of defective ultrasound transducers in use in routine clinical practice' and evaluate if annual testing is good enough to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level. A total of 299 transducers were tested in 13 clinics at five hospitals in the Stockholm area. Approximately 7000-15,000 ultrasound examinations are carried out at these clinics every year. The transducers tested in the study had been tested and classified as fully operational 1 year before and since then been in normal use in the routine clinical practice. The transducers were tested with the Sonora FirstCall Test System. There were 81 (27.1%) defective transducers found; giving a 95% confidence interval ranging from 22.1 to 32.1%. The most common transducer errors were 'delamination' of the ultrasound lens and 'break in the cable' which together constituted 82.7% of all transducer errors found. The highest error rate was found at the radiological clinics with a mean error rate of 36.0%. There was a significant difference in error rate between two observed ways the clinics handled the transducers. There was no significant difference in the error rates of the transducer brands or the transducers models. Annual testing is not sufficient to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level and it is strongly advisable to create a user routine that minimizes the handling of the transducers.

  17. Integration of Capacitive Micromachined Ultrasound Transducers to Microfluidic Devices

    KAUST Repository

    Viržonis, Darius

    2013-10-22

    The design and manufacturing flexibility of capacitive micromachined ultrasound transducers (CMUT) makes them attractive option for integration with microfluidic devices both for sensing and fluid manipulation. CMUT concept is introduced here by presentin

  18. Focused ultrasound transducer for thermal treatment.

    Science.gov (United States)

    Umemura, Shin-ichiro

    2015-03-01

    Air-backed transducers have been employed for thermal ultrasonic treatment including both ablation and hyperthermia because the power efficiency rather than the bandwidth is a main concern, unlike a typical imaging transducer working in a pulse mode. The characteristic of an air-backed piezoelectric transducer with a matching layer is analysed, and the role and choice of the matching layer is discussed. An element size of a focused array transducer, appropriate for such thermal treatment, is then estimated, and the characteristic of a piezoceramic transducer element of such a size was numerically analysed using a finite element code. The characteristic of a piezocomposite transducer element is also numerically analysed and its suitability to such a therapeutic array transducer is discussed.

  19. Three-Dimensional Synthetic Aperture Focusing Using a Rocking Convex Array Transducer

    DEFF Research Database (Denmark)

    Andresen, Henrik; Nikolov, Svetoslav; Pedersen, Mads Møller;

    2010-01-01

    Volumetric imaging can be performed using 1-D arrays in combination with mechanical motion. Outside the elevation focus of the array, the resolution and contrast quickly degrade compared with the lateral plane, because of the fixed transducer focus. This paper shows the feasibility of using...... synthetic aperture focusing for enhancing the elevation focus for a convex rocking array. The method uses a virtual source (VS) for defocused multi-element transmit, and another VS in the elevation focus point. This allows a direct time-of-flight to be calculated for a given 3-D point. To avoid artifacts...

  20. Focusing of ferroelectret air-coupled ultrasound transducers

    Science.gov (United States)

    Gaal, Mate; Bartusch, Jürgen; Dohse, Elmar; Schadow, Florian; Köppe, Enrico

    2016-02-01

    Air-coupled ultrasound has been applied increasingly as a non-destructive testing method for lightweight construction in recent years. It is particularly appropriate for composite materials being used in automotive and aviation industry. Air-coupled ultrasound transducers mostly consist of piezoelectric materials and matching layers. However, their fabrication is challenging and their signal-to-noise ratio often not sufficient for many testing requirements. To enhance the efficiency, air-coupled ultrasound transducers made of cellular polypropylene have been developed. Because of its small density and sound velocity, this piezoelectric ferroelectret matches the small acoustic impedance of air much better than matching layers applied in conventional transducers. In our contribution, we present two different methods of spherical focusing of ferroelectret transducers for the further enhancement of their performance in NDT applications. Measurements on carbon-fiber-reinforced polymer (CFRP) samples and on metal adhesive joints performed with commercially available focused air-coupled ultrasound transducers are compared to measurements executed with self-developed focused ferroelectret transducers.

  1. Transducers in medical ultrasound: Part Three. Transducer applications in echocardiology.

    Science.gov (United States)

    Lancée, C T; Daigle, R; Sahn, D J; Thijssen, J M

    1985-09-01

    A comparison is made between phased arrays and mechanical sector scanners in transcutaneous echocardiographic applications. Aspects such as contact area, beam control, side lobes, grating lobes and image quality are discussed in the context of transducer frequency. The incorporation of simultaneous acquisition of Doppler velocity information and display of M-mode signals is considered. Transoesophageal and intraoperative scanning systems for cardiology are also compared, in particular linear arrays, phased arrays and mechanical scanners, and their advantages and disadvantages in relation to the above mentioned aspects are discussed. The general conclusion is that electronic sector scanners may have a considerably improved cost/benefit ratio in the near future and thereby will become the leading systems for echocardiography.

  2. Broadband electrical impedance matching for piezoelectric ultrasound transducers.

    Science.gov (United States)

    Huang, Haiying; Paramo, Daniel

    2011-12-01

    This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.

  3. Delimitation of the lung region with distributed ultrasound transducers

    Science.gov (United States)

    Cardona Cárdenas, Diego Armando; Furuie, Sérgio Shiguemi

    2016-04-01

    One technique used to infer and monitor patient's respiratory conditions is the electrical impedance tomography (EIT). This provides images with information about lung function. The EIT image contrast is dependent on the variation of electrical impedance, therefore, this image does not provide anatomical details in border regions of several organs. To contribute to a clinical solution, we propose a new method to delimit regions of interest such as the pulmonary region and to improve the reconstruction quality of the EIT. Using a Matlab Toolbox k-wave, the ultrasound propagation phenomenon in homogeneous medium without patient (Reference) and with thoracic models were simulated, separately via a set of several ultrasound transducers distributed around the chest. After pulse emission by a transducer (TR), all received signals were compared considering the two sets of signals. If the energy relation between parts of the signals does not exceed an empirical threshold (30% in this study), a partial mask is generated between the transmitter and the receptor. This process was repeated until all 128 transducers are considered as TR-emitters. The 128 transducers (150kHz) are uniformly distributed. The evaluation was made by visually comparing the resulting images with the respective simulated object. A simple approach was presented to delimit high contrast organs with ultrasound transducers distributed around the patient. This approach allows other lower contrast objects to become invisible by varying the threshold limit. The investigation, based on numerical simulations of ultrasonic propagation, has shown promising results in the delimitation of the pulmonary region.

  4. Ultrasound transducer positioning aid for fetal heart rate monitoring.

    Science.gov (United States)

    Hamelmann, Paul; Kolen, Alex; Schmitt, Lars; Vullings, Rik; van Assen, Hans; Mischi, Massimo; Demi, Libertario; van Laar, Judith; Bergmans, Jan

    2016-08-01

    Fetal heart rate (fHR) monitoring is usually performed by Doppler ultrasound (US) techniques. For reliable fHR measurements it is required that the fetal heart is located within the US beam. In clinical practice, clinicians palpate the maternal abdomen to identify the fetal presentation and then the US transducer is fixated on the maternal abdomen where the best fHR signal can be obtained. Finding the optimal transducer position is done by listening to the strength of the Doppler audio output and relying on a signal quality indicator of the cardiotocographic (CTG) measurement system. Due to displacement of the US transducer or displacement of the fetal heart out of the US beam, the fHR signal may be lost. Therefore, it is often necessary that the obstetrician repeats the tedious procedure of US transducer positioning to avoid long periods of fHR signal loss. An intuitive US transducer positioning aid would be highly desirable to increase the work flow for the clinical staff. In this paper, the possibility to determine the fetal heart location with respect to the transducer by exploiting the received signal power in the transducer elements is shown. A commercially available US transducer used for fHR monitoring is connected to an US open platform, which allows individual driving of the elements and raw US data acquisition. Based on the power of the received Doppler signals in the transducer elements, the fetal heart location can be estimated. A beating fetal heart setup was designed and realized for validation. The experimental results show the feasibility of estimating the fetal heart location with the proposed method. This can be used to support clinicians in finding the optimal transducer position for fHR monitoring more easily.

  5. Comparison of Vector Velocity Imaging using Directional Beamforming and Transverse Oscillation for a Convex Array Transducer

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2014-01-01

    rig with a stationary, laminar flow, and the volume flow was measured by a MAG 3000 (Danfos, Sønderbog, Denmark) magnetic flow meter for reference. Data were beamformed with an optimized transverse oscillation scheme for the TO VFI, and standard fourth-order estimators were employed for the velocity......Vector velocity imaging can reveal both the magnitude and direction of the blood velocity. Several techniques have been suggested for estimating the velocity, and this paper compares the performance for directional beamforming and transverse oscillation (TO) vector flow imaging (VFI). Data have...... been acquired using the SARUS experimental ultrasound scanner connected to a BK 8820e (BK Medical, Herlev, Denmark) convex array probe with 192 active elements. A duplex sequence with 129 B-mode emissions interleaved with 129 flow emissions has been made. The flow was generated in a recirculating flow...

  6. Dissimilar trend of nonlinearity in ultrasound transducers and systems at resonance and non-resonance frequencies

    DEFF Research Database (Denmark)

    Ghasemi, Negareh; Zare, Firuz; Davari, Pooya

    2017-01-01

    Several factors can affect performance of an ultrasound system such as quality of excitation signal and ultrasound transducer behaviour. Nonlinearity of piezoelectric ultrasound transducers is a key determinant in designing a proper driving power supply. Although, the nonlinearity of piezoelectri...... receiver is a function of a voltage across the resistor in the RLC branches and is related to the resonance frequencies of the ultrasound transducer....

  7. Oblong-Shaped-Focused Transducers for Intravascular Ultrasound Imaging.

    Science.gov (United States)

    Lee, Junsu; Jang, Jihun; Chang, Jin Ho

    2017-03-01

    In intravascular ultrasound (IVUS) imaging, a transducer is inserted into a blood vessel and rotated to obtain image data. For this purpose, the transducer aperture is typically less than 0.5 mm in diameter, which causes natural focusing to occur in the imaging depth ranging from 1 to 5 mm. Due to the small aperture, however, it is not viable to conduct geometric focusing in order to enhance the spatial resolution of IVUS images. Furthermore, this hampers narrowing the slice thickness of a cross-sectional scan plane in the imaging depth, which leads to lowering spatial and contrast resolutions of IVUS images. To solve this problem, we propose an oblong-shaped-focused transducer for IVUS imaging. Unlike the conventional IVUS transducers with either a circular or a square flat aperture, the proposed transducer has an oblong aperture of which long side is positioned along a blood vessel. This unique configuration makes it possible to conduct geometric focusing at a desired depth in the elevation direction. In this study, furthermore, it is demonstrated that a spherically shaped aperture in both lateral and elevation directions also improves lateral resolution, compared to the conventional flat aperture. To ascertain this, the conventional and the proposed IVUS transducers were designed and fabricated to evaluate and to compare their imaging performances through wire phantom and tissue-mimicking phantom experiments. For the proposed 50-MHz IVUS transducer, a PZT piece of 0.5 × 1.0 mm(2) was spherically shaped for elevation focus at 3 mm by using the conventional press-focusing technique whereas the conventional one has a flat aperture of 0.5 × 0.5 mm(2). The experimental results demonstrated that the proposed IVUS transducer is capable of improving spatial and contrast resolutions of IVUS images.

  8. Dual-Frequency Piezoelectric Transducers for Contrast Enhanced Ultrasound Imaging

    Directory of Open Access Journals (Sweden)

    K. Heath Martin

    2014-11-01

    Full Text Available For many years, ultrasound has provided clinicians with an affordable and effective imaging tool for applications ranging from cardiology to obstetrics. Development of microbubble contrast agents over the past several decades has enabled ultrasound to distinguish between blood flow and surrounding tissue. Current clinical practices using microbubble contrast agents rely heavily on user training to evaluate degree of localized perfusion. Advances in separating the signals produced from contrast agents versus surrounding tissue backscatter provide unique opportunities for specialized sensors designed to image microbubbles with higher signal to noise and resolution than previously possible. In this review article, we describe the background principles and recent developments of ultrasound transducer technology for receiving signals produced by contrast agents while rejecting signals arising from soft tissue. This approach relies on transmitting at a low-frequency and receiving microbubble harmonic signals at frequencies many times higher than the transmitted frequency. Design and fabrication of dual-frequency transducers and the extension of recent developments in transducer technology for dual-frequency harmonic imaging are discussed.

  9. High intensity ultrasound transducer used in gene transfection

    Science.gov (United States)

    Morrison, Kyle P.; Keilman, George W.; Noble, Misty L.; Brayman, Andrew A.; Miao, Carol H.

    2012-11-01

    This paper describes a novel therapeutic high intensity non-focused ultrasound (HIU) transducer designed with uniform pressure distribution to aid in accelerated gene transfer in large animal liver tissues in vivo. The underlying HIU transducer was used to initiate homogeneous cavitation throughout the tissue while delivering up to 2.7 MPa at 1.1 MHz across its radiating surface. The HIU transducer was built into a 6 cm diameter x 1.3 cm tall housing ergonomically designed to avoid collateral damage to the surrounding anatomy during dynamic motion. The ultrasound (US) radiation was applied in a 'paintbrush-like' manner to the surface of the liver. The layers and geometry of the transducer were carefully selected to maximize the active diameter (5.74 cm), maximize the electrical to acoustic conversion efficiency (85%) to achieve 2.7 MPa of peak negative pressure, maximize the frequency operating band at the fundamental resonance to within a power transfer delta of 1 dB, and reduce the pressure delta to within 2 dB across the radiating surface. For maximum peak voltage into the transducer, a high performance piezoceramic was chosen and a DC bias circuit was built integral to the system. An apodized two element annular pattern was made from a single piezoceramic element, resulting in significant pressure uniformity enhancement. In addition to using apodization for pressure uniformity, a proprietary multi-layered structure was used to improve efficiency while sustaining an operating band from 900 kHz to 1.3 MHz. The resultant operating band allowed for dithering techniques using frequency modulation. The underlying HIU transducer for use in large animals enhances gene expression up to 6300-fold.

  10. Comparison of vector velocity imaging using directional beamforming and transverse oscillation for a convex array transducer

    Science.gov (United States)

    Jensen, Jørgen Arendt

    2014-03-01

    Vector velocity imaging can reveal both the magnitude and direction of the blood velocity. Several techniques have been suggested for estimating the velocity, and this paper compares the performance for directional beam-forming and transverse oscillation (TO) vector flow imaging (VFI). Data have been acquired using the SARUS experimental ultrasound scanner connected to a BK 8820e (BK Medical, Herlev, Denmark) convex array probe with 192 active elements. A duplex sequence with 129 B-mode emissions interleaved with 129 flow emissions has been made. The flow was generated in a recirculating flow rig with a stationary, laminar flow, and the volume flow was measured by a MAG 3000 (Danfos, Sønderbog, Denmark) magnetic flow meter for reference. Data were beamformed with an optimized transverse oscillation scheme for the TO VFI, and standard fourth-order estimators were employed for the velocity estimation. Directional RF lines were beamformed along the flow direction and cross-correlation employed to estimate the velocity magnitude. The velocities were determined for beam-to-flow angles of 60, 75 and 90 degrees. Using 32 emissions the standard deviation relative to the peak velocity for TO estimation was 7.0% at a beam-to-flow angle of 75° . This was 3.8% for directional beamforming and at 60° it was 2.2%. The general improvement, however, comes at an increase by a factor of roughly 11 in the number of calculations for the directional beamformation compared to the TO method.

  11. Breast ultrasound tomography with two parallel transducer arrays: preliminary clinical results

    Science.gov (United States)

    Huang, Lianjie; Shin, Junseob; Chen, Ting; Lin, Youzuo; Intrator, Miranda; Hanson, Kenneth; Epstein, Katherine; Sandoval, Daniel; Williamson, Michael

    2015-03-01

    Ultrasound tomography has great potential to provide quantitative estimations of physical properties of breast tumors for accurate characterization of breast cancer. We design and manufacture a new synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays. The distance of these two transducer arrays is adjustable for scanning breasts with different sizes. The ultrasound transducer arrays are translated vertically to scan the entire breast slice by slice and acquires ultrasound transmission and reflection data for whole-breast ultrasound imaging and tomographic reconstructions. We use the system to acquire patient data at the University of New Mexico Hospital for clinical studies. We present some preliminary imaging results of in vivo patient ultrasound data. Our preliminary clinical imaging results show promising of our breast ultrasound tomography system with two parallel transducer arrays for breast cancer imaging and characterization.

  12. Development of high frequency annular array ultrasound transducers

    Science.gov (United States)

    Gottlieb, Emanuel John

    The advantage of ultrasonic annular arrays over conventional single element transducers has been in the ability to transmit focus at multiple points throughout the depth of field, as well as receive dynamic focus. Today, annular, linear and multidimensional array imaging systems are not commercially available at frequencies greater than 20 MHz. The fabrication technology used to develop a high frequency (>50 MHz) annular array transducer is presented. A 9 mum P(VDF-TrFE) film was bonded to gold annuli electrodes on the top layer of a two sided polyimide flexible circuit. Each annulus was separated by a 30 mum kerf and had several electroplated micro vias that connected to electrode traces on the bottom side of the polyimide flexible circuit. The array's performance was evaluated by measuring the electrical impedance, pulse echo response and crosstalk measurement for each element in the array. In order to improve device sensitivity each element was electrically matched to an impedance magnitude of 50 O and 0° phase at resonance. The average round trip insertion loss measured for the array and compensated for diffraction effects was -33.5 dB. The measured average center frequency and bandwidth of an element was 55 MHz and 47 respectively. The measured crosstalk between adjacent elements remained below -29 dB at the center frequency in water. A vertical wire phantom was imaged using a single focus transmit beamformer and dynamic focusing receive beamformer. This image showed a significant improvement in lateral resolution over a range of 9 mm after the dynamic focusing receive algorithm was applied. These results correlated well with predictions from a Field II simulation. After beamforming the minimum lateral resolution (-6 dB) was 108 mum at the focus. Preliminary ultrasound B-mode images of the rabbit eye using this transducer were shown in conjunction with a multi-channel digital beamformer. A feasibility study of designing and fabricating tunable copolymer

  13. Novice performance of ultrasound-guided needle advancement: standard 38-mm transducer vs 25-mm hockey stick transducer.

    Science.gov (United States)

    Davies, T; Townsley, P; Jlala, H; Dowling, M; Bedforth, N; Hardman, J G; McCahon, R A

    2012-08-01

    The optimal method to develop expertise in ultrasound-guided regional anaesthesia is unknown. Studies of laryngoscopic expertise in novices demonstrate that the choice of laryngoscope affects performance. In this study, we aimed to compare the effect of two different linear array transducers (38-mm standard vs 25-mm hockey stick) on novice performance of ultrasound-guided needle advancement. Following randomisation, participants watched a video model of expert performance of ultrasound-guided needle advancement. Recruits performed the modelled task on a turkey breast model. The median (IQR [range]) composite error score was statistically significantly larger for participants in the hockey stick transducer group compared with the standard transducer group; 10.0 (7.3-14.3 [2.5-29.0]) vs 7.5 (4.5-10.0 [2.0-28.0]) respectively, (p = 0.01). This study has demonstrated that performance of ultrasound-guided needle advancement by novice operators after simple video instruction is better (as assessed using a composite error score) with a standard 38-mm transducer than with a 25-mm hockey stick transducer. Anaesthesia © 2012 The Association of Anaesthetists of Great Britain and Ireland.

  14. In-vivo Convex Array Vector Flow Imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Brandt, Andreas Hjelm; Nielsen, Michael Bachmann

    2014-01-01

    In-vivo VFI scans obtained from the abdomen of a human volunteer using a convex array transducers and trans- verse oscillation vector flow imaging (VFI) are presented. A 3 MHz BK Medical 8820e (Herlev, Denmark) 192-element convex array probe is used with the SARUS experimental ultrasound scanner....

  15. Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging.

    Science.gov (United States)

    Daoudi, K; van den Berg, P J; Rabot, O; Kohl, A; Tisserand, S; Brands, P; Steenbergen, W

    2014-10-20

    Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expensive systems, which limits their clinical application and makes the combination costly and impracticable. In this work we present and evaluate a compact and ergonomically designed handheld probe, connected to a portable ultrasound system for inexpensive, real-time dual-modality ultrasound/photoacoustic imaging. The probe integrates an ultrasound transducer array and a highly efficient diode stack laser emitting 130 ns pulses at 805 nm wavelength and a pulse energy of 0.56 mJ, with a high pulse repetition frequency of up to 10 kHz. The diodes are driven by a customized laser driver, which can be triggered externally with a high temporal stability necessary to synchronize the ultrasound detection and laser pulsing. The emitted beam is collimated with cylindrical micro-lenses and shaped using a diffractive optical element, delivering a homogenized rectangular light intensity distribution. The system performance was tested in vitro and in vivo by imaging a human finger joint.

  16. Ultrasound transducer modeling--general theory and applications to ultrasound reciprocal systems.

    Science.gov (United States)

    Willatzen, M

    2001-01-01

    A tutorial presentation on the theory of reciprocal ultrasound systems is given, and a complete set of modeling equations for one-dimensional multi-layer ultrasound transducers is derived from first principles. The model includes dielectric losses and mechanical losses in the transducer material layers as well as sound absorption in the transmission medium. First, the so-called constitutive relations of a piezoelectric body are derived based on general thermodynamic considerations, assuming that transducer operation takes place under almost isentropic conditions. Second, full attention is given to transducers oscillating in the thickness mode, discarding all other vibration modes. Dynamic transducer equations are determined using Newton's Second Law, Poisson's equation, and the definition of strain applied to a piezoelectric transducer with one or more non-piezoelectric layers on the front surface (multilayer transducer). Boundary conditions include continuity of normal velocity and stress across material interfaces as well as a subsidiary electrical condition over the piezoceramic electrodes. Sound transmission is assumed to take place in a water bath such that the Rayleigh equation can be used to obtain the incoming pressure at the receiver aperture from the acceleration of the opposing transmitter. This allows, e.g., a detailed treatment of receiver signal variations as the receiver moves from the near-field zone to the far-field zone of the transmitter. In the remaining part of the paper, receiver voltage and current signals are obtained by solving the full set of dynamic equations numerically. Special attention is given to transducers consisting of a) a pure piezoceramic layer only, b) a piezoceramic layer and a quarter-wavelength matching layer of polyphenylensulphide (PPS), c) a piezoceramic layer and a half-wavelength matching layer of stainless steel, and d) a piezoceramic layer and a half-wavelength matching layer of stainless steel tuned to resonance by

  17. Transducer models in the ultrasound simulation program FIELD II and their accuracy

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Bæk, David

    2010-01-01

    The FIELD II simulation program can be used for simulating any kind of linear ultrasound fields. The program is capable of describing multi-element transducers used with any kind of excitation, apodization, and focusing. The program has been widely used in both academia and by commercial ultrasound...... companies for investigation novel transducer geometries and advanced linear imaging schemes. The program models transducer geometries using a division of the transducer elements into either rectangles, triangles, or bounding lines. The precision of the simulation and the simulation time is intimately linked...

  18. Experimental analysis of 1-3 piezocomposites for high-intensity focused ultrasound transducer applications.

    Science.gov (United States)

    Chen, Gin-Shin; Liu, Hsin-Chih; Lin, Yu-Cheng; Lin, Yu-Li

    2013-01-01

    Piezocomposites with 1-3 connectivity have been extensively used in medical imaging transducers and high-intensity focused ultrasound transducers, but most studies of 1-3 piezocomposites address medical imaging applications. The purpose of this study was to completely investigate 1-3 composites specifically for high-power ultrasonic transducer applications via a series of experimental analyses. PZT4-epoxy composite focused transducers with various aspect ratios and volume fractions were constructed in-house for the evaluation of the coupling factor, dielectric loss tangent, quality factor, bandwidth, acoustic impedance, and electroacoustic efficiency. The experimental analyses demonstrated that although the coupling factor of composite transducers was higher than that of the ceramic transducer, the composite transducers had a lower efficiency due to the high dielectric loss and high mechanical energy loss of the composites. In addition, the bandwidth and acoustic impedance of composite transducers were superior to the ceramic transducer. For the composite transducers, the efficiency and acoustic impedance were inversely proportional to the aspect ratio and linearly proportional to the volume fraction. The coupling of inter pillars that are too close to each other could cause a significant decrease in the efficiency of the composite transducer. With an appropriate design in terms of the aspect ratio, volume fraction, and PZT-pillar spacing, a high-efficiency composite high-intensity focused ultrasound transducer can be achieved.

  19. A Flexible Ultrasound Transducer Array with Micro-Machined Bulk PZT

    Directory of Open Access Journals (Sweden)

    Zhe Wang

    2015-01-01

    Full Text Available This paper proposes a novel flexible piezoelectric micro-machined ultrasound transducer, which is based on PZT and a polyimide substrate. The transducer is made on the polyimide substrate and packaged with medical polydimethylsiloxane. Instead of etching the PZT ceramic, this paper proposes a method of putting diced PZT blocks into holes on the polyimide which are pre-etched. The device works in d31 mode and the electromechanical coupling factor is 22.25%. Its flexibility, good conformal contacting with skin surfaces and proper resonant frequency make the device suitable for heart imaging. The flexible packaging ultrasound transducer also has a good waterproof performance after hundreds of ultrasonic electric tests in water. It is a promising ultrasound transducer and will be an effective supplementary ultrasound imaging method in the practical applications.

  20. Resonant gravimetric immunosensing based on capacitive micromachined ultrasound transducers

    KAUST Repository

    Viržonis, Darius

    2014-04-08

    High-frequency (40 MHz) and low-frequency (7 MHz) capacitive micromachined ultrasound transducers (CMUT) were fabricated and tested for use in gravimetric detection of biomolecules. The low-frequency CMUT sensors have a gold-coated surface, while the high-frequency sensors have a silicon nitride surface. Both surfaces were functionalized with bovine leukemia virus antigen gp51 acting as the antigen. On addition of an a specific antibody labeled with horseradish peroxidase (HRP), the antigen/antibody complex is formed on the surface and quantified by HRP-catalyzed oxidation of tetramethylbenzidine. It has been found that a considerably smaller quantity of immuno complex is formed on the high frequency sensor surface. In parallel, the loading of the surface of the CMUT was determined via resonance frequency and electromechanical resistance readings. Following the formation of the immuno complexes, the resonance frequencies of the low-frequency and high-frequency sensors decrease by up to 420 and 440 kHz, respectively. Finite element analysis reveals that the loading of the (gold-coated) low frequency sensors is several times larger than that on high frequency sensors. The formation of the protein film with pronounced elasticity and stress on the gold surface case is discussed. We also discuss the adoption of this method for the detection of DNA using a hybridization assay following polymerase chain reaction.

  1. First measurements on a novel type of optical micro-machined ultrasound transducer (OMUT)

    NARCIS (Netherlands)

    Leinders, S.M.; Dongen, K.W.A. van; Jong, N. de; Verweij, M.D.; Westerveld, W.J.; Urbach, H.P.; Neer, P.L.M.J. van; Pozo Torres, J.M.

    2014-01-01

    Several types of ultrasound sensors have been developed and are used in the field of medical imaging. Conventional transducers are made of piezo-electric material and show good practical performance. However, when the piezo-electric elements need to be small (below 100 μm × 100 μm), these transducer

  2. First measurements on a novel type of optical micro-machined ultrasound transducer (OMUT)

    NARCIS (Netherlands)

    Leinders, S.M.; Dongen, K.W.A. van; Jong, N. de; Verweij, M.D.; Westerveld, W.J.; Urbach, H.P.; Neer, P.L.M.J. van; Pozo Torres, J.M.

    2014-01-01

    Several types of ultrasound sensors have been developed and are used in the field of medical imaging. Conventional transducers are made of piezo-electric material and show good practical performance. However, when the piezo-electric elements need to be small (below 100 μm × 100 μm), these transducer

  3. Acoustical cross-talk in row–column addressed 2-D transducer arrays for ultrasound imaging

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lehrmann; Jensen, Jørgen Arendt; Thomsen, Erik Vilain

    2015-01-01

    The acoustical cross-talk in row–column addressed 2-D transducer arrays for volumetric ultrasound imaging is investigated. Experimental results from a 2.7 MHz, λ/2-pitch capacitive micromachined ultrasonic transducer (CMUT) array with 62 rows and 62 columns are presented and analyzed...

  4. Transducer combination for high-quality ultrasound tomography based on speed of sound imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young Hun; Park, Kwan Kyu [Dept. of Mechanical Engineering, Hanyang University, Seoul (Korea, Republic of)

    2016-02-15

    The type of ultrasound transducer used influences the quality of a reconstructed ultrasound image. This study analyzed the effect of transducer type on ultrasound computed tomography (UCT) image quality. The UCT was modeled in an ultrasound simulator by using a 5 cm anatomy model and a ring-shape 5 MHz 128 transducer array, which considered attenuation, refraction, and reflection. Speed-of-sound images were reconstructed by the Radon transform as the UCT image modality. Acoustic impedance images were also reconstructed by the delayand-sum (DAS) method, which considered the speed of sound information. To determine the optimal combination of transducers in observation, point-source, flat, and focused transducers were tested in combination as trasmitters and receivers; UCT images were constructed from each combination. The combination of point-source/flat transducer as transmitting and receiving devices presented the best reconstructed image quality. In UCT implementation, the combination of a flat transducer for transmitting and a point transducer for receiving permitted acceptable image quality.

  5. Nonlinear Effects in Ultrasound Fields of Diagnostic-type Transducers Used for Kidney Stone Propulsion: Characterization in Water

    Science.gov (United States)

    Karzova, M.; Cunitz, B.; Yuldashev, P.; Andriyakhina, Y.; Kreider, W.; Sapozhnikov, O.; Bailey, M.; Khokhlova, V.

    2016-01-01

    Newer imaging and therapeutic ultrasound technologies require higher in situ pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher transducer output to provide stronger pushing force; however, nonlinear acoustic saturation effect can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match low power pressure beam scans. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging. PMID:27087711

  6. Modeling transducer impulse responses for predicting calibrated pressure pulses with the ultrasound simulation program Field II

    DEFF Research Database (Denmark)

    Bæk, David; Jensen, Jørgen Arendt; Willatzen, Morten

    2010-01-01

    FIELD II is a simulation software capable of predicting the field pressure in front of transducers having any complicated geometry. A calibrated prediction with this program is, however, dependent on an exact voltage-to-surface acceleration impulse response of the transducer. Such impulse response...... is not calculated by FIELD II. This work investigates the usability of combining a one-dimensional multilayer transducer modeling principle with the FIELD II software. Multilayer here refers to a transducer composed of several material layers. Measurements of pressure and current from Pz27 piezoceramic disks...... as well as pressure and intensity measurements in front of a 128 element commercial convex medical transducer are compared to the simulations. Results show that the models can predict the pressure from the piezoceramic disks with a root mean square (rms) error of 11.2% to 36.2% with a 2 dB amplitude...

  7. Optimal experimental design to position transducers in ultrasound breast imaging

    Science.gov (United States)

    Korta Martiartu, Naiara; Boehm, Christian; Vinard, Nicolas; Jovanović Balic, Ivana; Fichtner, Andreas

    2017-03-01

    We present methods to optimize the setup of a 3D ultrasound tomography scanner for breast cancer detection. This approach provides a systematic and quantitative tool to evaluate different designs and to optimize the con- figuration with respect to predefined design parameters. We consider both, time-of-flight inversion using straight rays and time-domain waveform inversion governed by the acoustic wave equation for imaging the sound speed. In order to compare different designs, we measure their quality by extracting properties from the Hessian operator of the time-of-flight or waveform differences defined in the inverse problem, i.e., the second derivatives with respect to the sound speed. Spatial uncertainties and resolution can be related to the eigenvalues of the Hessian, which provide a good indication of the information contained in the data that is acquired with a given design. However, the complete spectrum is often prohibitively expensive to compute, thus suitable approximations have to be developed and analyzed. We use the trace of the Hessian operator as design criterion, which is equivalent to the sum of all eigenvalues and requires less computational effort. In addition, we suggest to take advantage of the spatial symmetry to extrapolate the 3D experimental design from a set of 2D configurations. In order to maximize the quality criterion, we use a genetic algorithm to explore the space of possible design configurations. Numerical results show that the proposed strategies are capable of improving an initial configuration with uniformly distributed transducers, clustering them around regions with poor illumination and improving the ray coverage of the domain of interest.

  8. Design and implementation of capacitive micromachined ultrasonic transducers for high intensity focused ultrasound

    OpenAIRE

    Yamaner, Yalçın Feysel; Yamaner, Yalcin Feysel

    2011-01-01

    High intensity focused ultrasound (HIFU) is a medical procedure for noninvasive treatment of cancers. High intensity focused ultrasound is used to heat and destroy the diseased tissue. Piezoelectricity has been the core mechanism for generation of ultrasound waves in the treatment. Focusing can be done by using spherically curved transducers or using a lens or electronically steering sound waves by using phased arrays. Current research in HIFU technology targets the development of MR-guided m...

  9. Effects of Non-Elevation-Focalized Linear Array Transducer on Ultrasound Plane-Wave Imaging

    Directory of Open Access Journals (Sweden)

    Congzhi Wang

    2016-11-01

    Full Text Available Plane-wave ultrasound imaging (PWUS has become an important method of ultrasound imaging in recent years as its frame rate has exceeded 10,000 frames per second, allowing ultrasound to be used for two-dimensional shear wave detection and functional brain imaging. However, compared to the traditional focusing and scanning method, PWUS images always suffer from a degradation of lateral resolution and contrast. To improve the image quality of PWUS, many different beamforming algorithms have been proposed and verified. Yet the influence of transducer structure is rarely studied. For this paper, the influence of using an acoustic lens for PWUS was evaluated. Two linear array transducers were fabricated. One was not self-focalized in the elevation direction (non-elevation-focalized transducer, NEFT; the other one was a traditional elevation-focalized transducer (EFT. An initial simulation was conducted to show the influence of elevation focusing. Then the images obtained with NEFT on a standard ultrasound imaging phantom were compared with those obtained with EFT. It was demonstrated that, in a relatively deep region, the contrast of an NEFT image is better than that of an EFT image. These results indicate that a more sophisticated design of ultrasound transducer would further improve the image quality of PWUS.

  10. Nonlinear effects in ultrasound fields of diagnostic-type transducers used for kidney stone propulsion: Characterization in water

    Energy Technology Data Exchange (ETDEWEB)

    Karzova, M., E-mail: masha@acs366.phys.msu.ru [Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France); Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Cunitz, B.; Kreider, W.; Bailey, M. [Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40" t" h Street, Seattle, WA 98105 (United States); Yuldashev, P.; Andriyakhina, Y. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Sapozhnikov, O.; Khokhlova, V. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40" t" h Street, Seattle, WA 98105 (United States)

    2015-10-28

    Newer imaging and therapeutic ultrasound technologies require higher in situ pressure levels compared to conventional diagnostic values. One example is the recently developed use of focused ultrasonic radiation force to move kidney stones and residual fragments out of the urinary collecting system. A commercial diagnostic 2.3 MHz C5-2 array probe is used to deliver the acoustic pushing pulses. The probe comprises 128 elements equally spaced at the 55 mm long convex cylindrical surface with 38 mm radius of curvature. The efficacy of the treatment can be increased by using higher intensity at the focus to provide stronger pushing force; however, nonlinear acoustic saturation can be a limiting factor. In this work nonlinear propagation effects were analyzed for the C5-2 transducer using a combined measurement and modeling approach. Simulations were based on the 3D Westervelt equation; the boundary condition was set to match the focal geometry of the beam as measured at a low power output. Focal waveforms simulated for increased output power levels were compared with the fiber-optic hydrophone measurements and were found in good agreement. It was shown that saturation effects do limit the acoustic pressure in the focal region of the transducer. This work has application to standard diagnostic probes and imaging.

  11. Design and fabrication of PIN-PMN-PT single-crystal high-frequency ultrasound transducers.

    Science.gov (United States)

    Sun, Ping; Zhou, Qifa; Zhu, Benpeng; Wu, Dawei; Hu, Changhong; Cannata, Jonathan M; Tian, Jin; Han, Pengdi; Wang, Gaofeng; Shung, K Kirk

    2009-12-01

    High-frequency PIN-PMN-PT single crystal ultrasound transducers at center frequencies of 35 MHz and 60 MHz were successfully fabricated using lead indium niobate-lead magnesium niobate-lead titanate (0.23PIN- 0.5PMN-0.27PT) single crystal. The new PIN-PMN-PT single crystal has higher coercivity (6.0 kV/cm) and higher Curie temperature (160 degrees C) than PMN-PT crystal. Experimental results showed that the PIN-PMN-PT transducers have similar performance but better thermal stability compared with the PMN-PT transducers.

  12. Ultrasound transducer shape has no effect on measurements of lumbar multifidus muscle size.

    Science.gov (United States)

    Worsley, Peter R; Smith, Nicholas; Warner, Martin B; Stokes, Maria

    2012-04-01

    Evidence is currently lacking for guidance on ultrasound transducer configuration (shape) when imaging muscle to measure its size. This study compared measurements made of lumbar multifidus on images obtained using curvilinear and linear transducers. Fifteen asymptomatic males (aged 21-32 years) had their right lumbar multifidus imaged at L3. Two transverse images were taken with two transducers (5 MHz curvilinear and 6 MHz linear), and linear and cross-sectional area (CSA) measurements were made off-line. Reliability of image interpretation was shown using intra-class correlation coefficients (0.78-0.99). Muscle measurements were compared between transducers using Bland and Altman plots and paired t-tests. Relationships between CSA and linear measurements were examined using Pearson's Correlation Coefficients. There were no significant differences (p > 0.05) in the measurements of the two transducers. Thickness and CSA measurements had small differences between transducers, with mean differences of 0.01 cm (SDdiff = 0.21 cm) and 0.03 cm(2) (SDdiff = 0.58 cm(2)) respectively. Width measures had a mean difference of 0.14 cm, with the linear transducer giving larger measures. Significant correlations (p transducers (r = 0.78-0.89). Measurements of multifidus at L3 were not influenced by the configuration of transducers of similar frequency. For the purposes of image interpretation, the curvilinear transducer produced better definition of the lateral muscle border, suggesting it as the preferable transducer for imaging lumbar multifidus. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. DUAL-FOCUS THERAPEUTIC ULTRASOUND TRANSDUCER FOR PRODUCTION OF BROAD TISSUE LESIONS

    Science.gov (United States)

    Jeong, Jong Seob; Cannata, Jonathan M.; Shung, K. Kirk

    2011-01-01

    In noninvasive high-intensity focused ultrasound (HIFU) treatment, formation of a large tissue lesion per sonication is desirable for reducing the overall treatment time. The goal of this study is to show the feasibility of enlarging tissue lesion size with a dual-focus therapeutic ultrasound transducer (DFTUT) by increasing the depth-of-focus (DOF). The proposed transducer consists of a disc- and an annular-type element of different radii of curvatures to produce two focal zones. To increase focal depth and to maintain uniform beamwidth of the elongated DOF, each element transmits ultrasound of a different center frequency: the inner element at a higher frequency for near field focusing and the outer element at a lower frequency for far field focusing. By activating two elements at the same time with a single transmitter capable of generating a dual-frequency mixed signal, the overall DOF of the proposed transducer may be extended considerably. A prototype transducer composed of a 4.1 MHz inner element and a 2.7 MHz outer element was fabricated to obtain preliminary experimental results. The feasibility the proposed technique was demonstrated through sound field, temperature and thermal dose simulations. The performance of the prototype transducer was verified by hydrophone measurements and tissue ablation experiments on a beef liver specimen. When several factors affecting the length and the uniformity of elongated DOF of the DFTUT are optimized, the proposed therapeutic ultrasound transducer design may increase the size of ablated tissues in the axial direction and, thus, decreasing the treatment time for a large volume of malignant tissues especially deep-seated targets. PMID:20870346

  14. The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating

    Science.gov (United States)

    Payne, Allison; Vyas, Urvi; Todd, Nick; Bever, Joshua de; Christensen, Douglas A.; Parker, Dennis L.

    2011-01-01

    Purpose: This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. Methods: The thermal response of a nine-position raster and a 16-mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue-mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite-difference approximation of the Pennes’ bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near-field heating. Results: Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256-element phased array significantly increases the thermal dose deposited in the near-field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near-field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256-randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase-adjusted sample points. Conclusions: Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near-field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near-field tissue temperature will

  15. The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating.

    Science.gov (United States)

    Payne, Allison; Vyas, Urvi; Todd, Nick; de Bever, Joshua; Christensen, Douglas A; Parker, Dennis L

    2011-09-01

    This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. The thermal response of a nine-position raster and a 16-mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue-mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite-difference approximation of the Pennes' bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near-field heating. Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256-element phased array significantly increases the thermal dose deposited in the near-field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near-field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256-randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase-adjusted sample points. Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near-field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near-field tissue temperature will help to ensure patient safety during an MRg

  16. Transducer hygiene: comparison of procedures for decontamination of ultrasound transducers and their use in clinical practice.

    Science.gov (United States)

    Häggström, Mikael; Spira, Jack; Edelstam, Greta

    2015-02-01

    To determine whether current hygiene practices are appropriate during sonographic examinations. Five major hospitals in Sweden were investigated with a survey. At each hospital, the departments corresponding to the main types of sonographic examination were chosen. Personnel who were responsible for or acquainted with the local hygiene procedures completed a standardardized questionnaire. The surveys were completed by 25 departments, where the total number of sonographic examinations was approximately 20,000 per month. For transvaginal and transrectal sonographic examinations, the most common method for decontamination of the transducer was barrier protection during the procedure followed by cleansing with alcohol. Latex was the predominant cover material, but one department used polyethylene gloves, and another department used nitrile gloves. Both of these involved transvaginal ultrasonography. In transcutaneous examinations, all hospitals were using alcohol and paper or cloth for decontamination at a minimum. Transesophageal examinations were carried out without barrier protection, and decontamination was performed with an alkylating substance. The hygiene practices appear to be appropriate at most hospitals, but there is a prevalence of transducer cover materials of unacceptable permeability, as well as use of gloves on transducers despite insufficient evidence of safety. © 2015 Wiley Periodicals, Inc.

  17. Dual-frequency super harmonic imaging piezoelectric transducers for transrectal ultrasound

    Science.gov (United States)

    Kim, Jinwook; Li, Sibo; Kasoji, Sandeep; Dayton, Paul A.; Jiang, Xiaoning

    2015-03-01

    In this paper, a 2/14 MHz dual-frequency single-element transducer and a 2/22 MHz sub-array (16/48-elements linear array) transducer were developed for contrast enhanced super-harmonic ultrasound imaging of prostate cancer with the low frequency ultrasound transducer as a transmitter for contrast agent (microbubble) excitation and the high frequency transducer as a receiver for detection of nonlinear responses from microbubbles. The 1-3 piezoelectric composite was used as active materials of the single-element transducers due to its low acoustic impedance and high coupling factor. A high dielectric constant PZT ceramic was used for the sub-array transducer due to its high dielectric property induced relatively low electrical impedance. The possible resonance modes of the active elements were estimated using finite element analysis (FEA). The pulse-echo response, peak-negative pressure and bubble response were tested, followed by in vitro contrast imaging tests using a graphite-gelatin tissue-mimicking phantom. The single-element dual frequency transducer (8 × 4 × 2 mm3) showed a -6 dB fractional bandwidth of 56.5% for the transmitter, and 41.8% for the receiver. A 2 MHz-transmitter (730 μm pitch and 6.5 mm elevation aperture) and a 22 MHz-receiver (240 μm pitch and 1.5 mm aperture) of the sub-array transducer exhibited -6 dB fractional bandwidth of 51.0% and 40.2%, respectively. The peak negative pressure at the far field was about -1.3 MPa with 200 Vpp, 1-cycle 2 MHz burst, which is high enough to excite microbubbles for nonlinear responses. The 7th harmonic responses from micro bubbles were successfully detected in the phantom imaging test showing a contrast-to-tissue ratio (CTR) of 16 dB.

  18. Development of a thermal test object for the measurement of ultrasound intracavity transducer self-heating.

    Science.gov (United States)

    Killingback, Alban L T; Newey, Valentine R; El-Brawany, Mohamed A; Nassiri, Dariush K

    2008-12-01

    The elevated surface temperature of diagnostic ultrasound transducers imposes an important limitation to their safe use in clinical situations. Moreover, particular care should be taken if transvaginal transducers are to be used during routine scans in the first few weeks of pregnancy as the transducer surface can be very close to embryonic/fetal tissues. Published results have shown that the heating of tissue due to transducer self-heating can equal and often exceed the acoustic heating contribution. In this article, we report the development of a portable self contained thermal test object (TTO) capable of assessing the self-heating of intracavity diagnostic ultrasound transducers. The thermal conductivity and volumetric heat capacity of the tissue mimicking material (TMM) used in the TTO were measured, yielding values of (0.56 +/- 0.01) W m(-1) K(-1) and (3.5 +/- 0.8) MJ m(-3) K(-1). The speed of sound of the TMM was measured as 1540 m s(-1) and the attenuation over a frequency range of 2 to 10 MHz was found to be (0.50 +/- 0.01) dB cm(-1) MHz(-1). These results are in excellent agreement with the International Electrotechnical Commission (IEC 60601-2-37) requirements and the previously published properties of biological soft tissue. The temperature stability and uniformity, and suitability of the TTO for the measurement of transducer self-heating were tested and found to be satisfactory. The TTO reached a stable temperature of 37 degrees C in 3 h and the spatial variation in temperature was less than +/- 0.2 degrees C. Lastly, transducer self-heating measurements from a transvaginal transducer exceeded the IEC temperature limit of 43 degrees C in less than 5 min and the temperature reached after 30 min was 47.3 degrees C.

  19. Simulating arbitrary-geometry ultrasound transducers using triangles

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    1996-01-01

    -echo field. The spatial impulse response has only been determined analytically for a few geometries and using apodization over the transducer surface generally makes it impossible to find the response analytically. A popular approach to find the general field is thus to split the aperture into small...... focused at different zones. The time-integrated spatial impulse response is used in the program to minimize the effect of the sharp edges of the spatial impulse response in a sampled signal. Since the integrated response from a triangular element cannot be analytically evaluated, a simple numerical...

  20. Angled-focused 45 MHz PMN-PT single element transducer for intravascular ultrasound imaging.

    Science.gov (United States)

    Yoon, Sangpil; Williams, Jay; Kang, Bong Jin; Yoon, Changhan; Cabrera-Munoz, Nestor; Jeong, Jong Seob; Lee, Sang Goo; Shung, K Kirk; Kim, Hyung Ham

    2015-06-01

    A transducer with an angled and focused aperture for intravascular ultrasound imaging has been developed. The acoustic stack for the angled-focused transducer was made of PMN-PT single crystal with one matching layer, one protective coating layer, and a highly damped backing layer. It was then press-focused to a desired focal length and inserted into a thin needle housing with an angled tip. A transducer with an angled and unfocused aperture was also made, following the same fabrication procedure, to compare the performance of the two transducers. The focused and unfocused transducers were tested to measure their center frequencies, bandwidths, and spatial resolutions. Lateral resolution of the angled-focused transducer (AFT) improved more than two times compared to that of the angled-unfocused transducer (AUT). A tissue-mimicking phantom in water and a rabbit aorta tissue sample in rabbit blood were scanned using AFT and AUT. Imaging with AFT offered improved contrast, over imaging with AUT, of the tissue-mimicking phantom and the rabbit aorta tissue sample by 23 dB and 8 dB, respectively. The results show that AFT has strong potential to provide morphological and pathological information of coronary arteries with high resolution and high contrast.

  1. TOPICAL REVIEW: Capacitive micromachined ultrasonic transducer arrays for minimally invasive medical ultrasound

    Science.gov (United States)

    Chen, Jingkuang

    2010-02-01

    This paper reviews the minimally invasive capacitive micromachined ultrasonic transducer (CMUT) arrays for medical diagnosis and therapy. While piezoelectric transducers dominate today's medical ultrasound market, the capacitive micromachined ultrasonic transducer has recently emerged as a promising alternative which delivers a comparable device performance to its piezoelectric counterparts, is compatible with front-end circuit integration, allows high-density imager integration and is relative easy in miniaturization. Utilizing MEMS technology, the substrate of CMUT arrays can be micromachined into miniature platforms with various geometrical shapes, which include needles, three-dimensional prisms, as well as other flexible-substrate configurations. These arrays are useful for reaching deep inside the tissue or an organ with a minimally invasive approach. Due to the close proximity of the transducers to the target organ/tissue, a higher resolution/accuracy of diagnostic information can be achieved. In addition to pulse-echo and photoacoustic imaging, high-power CMUT devices capable of delivering ultrasounds with a pressure greater than 1.0 MPa have been monolithically integrated with imager CMUTs for image-guided therapy (IGT). Such miniature devices would facilitate diagnostic and therapy interventions not possible with conventional piezoelectric transducers.

  2. Piezoelectric Micromachined Ultrasound Transducer (PMUT Arrays for Integrated Sensing, Actuation and Imaging

    Directory of Open Access Journals (Sweden)

    Yongqiang Qiu

    2015-04-01

    Full Text Available Many applications of ultrasound for sensing, actuation and imaging require miniaturized and low power transducers and transducer arrays integrated with electronic systems. Piezoelectric micromachined ultrasound transducers (PMUTs, diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays. This paper presents an overview of the current development status of PMUTs and a discussion of their suitability for miniaturized and integrated devices. The thin film piezoelectric materials required to functionalize these devices are discussed, followed by the microfabrication techniques used to create PMUT elements and the constraints the fabrication imposes on device design. Approaches for electrical interconnection and integration with on-chip electronics are discussed. Electrical and acoustic measurements from fabricated PMUT arrays with up to 320 diaphragm elements are presented. The PMUTs are shown to be broadband devices with an operating frequency which is tunable by tailoring the lateral dimensions of the flexural membrane or the thicknesses of the constituent layers. Finally, the outlook for future development of PMUT technology and the potential applications made feasible by integrated PMUT devices are discussed.

  3. Piezoelectric micromachined ultrasound transducer (PMUT) arrays for integrated sensing, actuation and imaging.

    Science.gov (United States)

    Qiu, Yongqiang; Gigliotti, James V; Wallace, Margeaux; Griggio, Flavio; Demore, Christine E M; Cochran, Sandy; Trolier-McKinstry, Susan

    2015-04-03

    Many applications of ultrasound for sensing, actuation and imaging require miniaturized and low power transducers and transducer arrays integrated with electronic systems. Piezoelectric micromachined ultrasound transducers (PMUTs), diaphragm-like thin film flexural transducers typically formed on silicon substrates, are a potential solution for integrated transducer arrays. This paper presents an overview of the current development status of PMUTs and a discussion of their suitability for miniaturized and integrated devices. The thin film piezoelectric materials required to functionalize these devices are discussed, followed by the microfabrication techniques used to create PMUT elements and the constraints the fabrication imposes on device design. Approaches for electrical interconnection and integration with on-chip electronics are discussed. Electrical and acoustic measurements from fabricated PMUT arrays with up to 320 diaphragm elements are presented. The PMUTs are shown to be broadband devices with an operating frequency which is tunable by tailoring the lateral dimensions of the flexural membrane or the thicknesses of the constituent layers. Finally, the outlook for future development of PMUT technology and the potential applications made feasible by integrated PMUT devices are discussed.

  4. Thin catheter bending in the direction perpendicular to ultrasound propagation using two-dimensional array transducer

    Science.gov (United States)

    Suzuki, Toshiya; Mochizuki, Takashi; Ushimizu, Hidetaka; Miyazawa, Shinya; Tsurui, Nobuhiro; Masuda, Kohji

    2017-07-01

    Although we have already experimented on the bending of a thin catheter with acoustic radiation force using a single transducer, it is necessary to develop a method of bending a catheter in an arbitrary direction because the installation position of ultrasound transducers on a body surface is limited for application to various shapes of in vivo blood vessels. Therefore, we examined the bending of a thin catheter in the direction perpendicular to ultrasound propagation using a two-dimensional array transducer (1 MHz), which realizes not only the temporospatial design but also the dynamic variation of acoustic fields. Forming two focal points with opposite phases, where the amplitudes of the two points instantaneously have the positive and negative relationship, we confirmed the bending of a thin catheter in the direction perpendicular to ultrasound propagation. We used a thin catheter (diameter, 200 µm length, 50 mm) to obtain the maximum displacement of 220 µm, where the displacement was proportional to the square of the maximum sound pressure and the duty ratio. From these results, the acoustic energy densities observed in front of and behind the catheter are dominant for the bending of the thin catheter independent of ultrasound propagation. We also found that the distance between two focal points may improve the bending performance without requiring a precise position setting.

  5. Acoustical cross-talk in row–column addressed 2-D transducer arrays for ultrasound imaging

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lehrmann; Jensen, Jørgen Arendt; Thomsen, Erik Vilain

    2015-01-01

    The acoustical cross-talk in row–column addressed 2-D transducer arrays for volumetric ultrasound imaging is investigated. Experimental results from a 2.7 MHz, λ/2-pitch capacitive micromachined ultrasonic transducer (CMUT) array with 62 rows and 62 columns are presented and analyzed...... in the frequency-wavenumber domain. The sources of cross-talk are identified and predicted theoretically. The nearest neighbor cross-talk is 23.9±3.7 dB when the array is used as a 1-D array with the rows functioning as both transmitters and receivers. In the row–column configuration, with the columns transmitting...

  6. Micromachined PIN-PMN-PT Crystal Composite Transducer for High-Frequency Intravascular Ultrasound (IVUS) Imaging

    OpenAIRE

    Li, Xiang; Ma, Teng; Tian, Jian; Han, Pengdi; Zhou, Qifa; Shung, K. Kirk

    2014-01-01

    In this paper, we report the use of micromachined PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–PbTiO3 (PIN-PMN-PT) single crystal 1–3 composite material for intravascular ultrasound (IVUS) imaging application. The effective electromechanical coupling coefficient kt(eff) of the composite was measured to be 0.75 to 0.78. Acoustic impedance was estimated to be 20 MRayl. Based on the composite, needle-type and flexible-type IVUS transducers were fabricated. The composite transducer achieved an 86% bandwidth at ...

  7. Design and Fabrication of PIN-PMN-PT Single-Crystal High-Frequency Ultrasound Transducers

    OpenAIRE

    Sun, Ping; Zhou, Qifa; Zhu, Benpeng; WU, DAWEI; Hu, Changhong; Cannata, Jonathan M.; Tian, Jin; Han, Pengdi; Wang, Gaofeng; Shung, K. Kirk

    2009-01-01

    High-frequency PIN-PMN-PT single crystal ultrasound transducers at center frequencies of 35 MHz and 60 MHz were successfully fabricated using lead indium niobate-lead magnesium niobate-lead titanate (0.23PIN-0.5PMN-0.27PT) single crystal. The new PIN-PMN-PT single crystal has higher coercivity (6.0 kV/cm) and higher Curie temperature (160°C) than PMN-PT crystal. Experimental results showed that the PIN-PMN-PT transducers have similar performance but better thermal stability compared with the ...

  8. Note: Comparative experimental studies on the performance of 2-2 piezocomposite for medical ultrasound transducers

    Science.gov (United States)

    Marinozzi, F.; Bini, F.; Biagioni, A.; Grandoni, A.; Spicci, L.

    2013-09-01

    The paper reports the experimental investigation of the behavior of 2-2 Lead Zirconate Titanate (PZT)-polymer composite transducers array for clinical ultrasound equipments. Several 2-2 plate composites having the same dicing pitch of 0.11 mm and different volume fractions were manufactured and investigated. Measurements were performed through different techniques such as electrical impedance, pulse-echo, and Laser Doppler Vibrometer. With the last one, maps of the surface displacement were presented relative to thickness mode and first lateral mode resonance frequencies. The transducers with volume fractions of the 40% resulted markedly inefficient, whereas the largest bandwidth and best band shape were achieved by the 50%.

  9. Handheld probe integrating laser diode and ultrasound transducer array for ultrasound/photoacoustic dual modality imaging

    NARCIS (Netherlands)

    Daoudi, K.; Berg, van den P.J.; Rabot, O.; Kohl, A.; Tisserand, S.; Brands, P.J.; Steenbergen, W.

    2014-01-01

    Ultrasound and photoacoustics can be utilized as complementary imaging techniques to improve clinical diagnoses. Photoacoustics provides optical contrast and functional information while ultrasound provides structural and anatomical information. As of yet, photoacoustic imaging uses large and expens

  10. Ultrasound backscatter microscope using PZT, fine-grain PZT, and single-crystal perovskite transducers

    Science.gov (United States)

    Olbrish, Kenneth D.; Zipparo, Michael J.; Lopath, Patrick D.; Yu, Clarence; Shrout, Thomas R.; Shung, K. Kirk

    1997-04-01

    Higher frequency ultrasound is rapidly becoming an important tool for dermatologic and ophthalmologic imaging. This brings about a need for improvement in single element transducers operating in the frequency range between 40 MHz and 100 MHz. Several piezoelectric materials may yield improved performance over common lead zirconate titanate (PZT) transducers. This study investigated several different materials incorporated into single element transducers. A static ultrasonic backscatter microscope (UBM) was constructed in the laboratory. This system allowed for a comparative testing of the imaging performance of various transducers. B-mode scans made by individual transducers show differences in image resolution. Clinically, these differences may be important to allow finer detail to be observed in a structure. Not only does this work show differences between transducers constructed from various materials, but it does so in an application-based environment. Previously, only a limited number of materials were used in such a system. This study showed results from several materials that had not been demonstrated before.

  11. Micromachined ultrasound transducers with improved coupling factors from a CMOS compatible process

    Science.gov (United States)

    Eccardt; Niederer

    2000-03-01

    For medical high frequency acoustic imaging purposes the reduction in size of a single transducer element for one-dimensional and even more for two-dimensional arrays is more and more limited by fabrication and cabling technology. In the fields of industrial distance measurement and simple object recognition low cost phased arrays are lacking. Both problems can be solved with micromachined ultrasound transducers (MUTs). A single transducer is made of a large number of microscopic elements. Because of the array structure of these transducers, groups of elements can be built up and used as a phased array. By integrating parts of the sensor electronics on chip, the cabling effort for arrays can be reduced markedly. In contrast to standard ultrasonic technology, which is based on massive thickness resonators, vibrating membranes are the radiating elements of the MUTs. New micromachining technologies have emerged, allowing a highly reproducible fabrication of electrostatically driven membranes with gap heights below 500 nm. A microelectronic BiCMOS process was extended for surface micromechanics (T. Scheiter et al., Proceedings 11th European Conference on Solid-State Transducers, Warsaw, Vol. 3, 1997, pp. 1595-1598). Additional process steps were included for the realization of the membranes which form sealed cavities with the underlying substrate. Membrane and substrate are the opposite electrodes of a capacitive transducer. The transducers can be integrated monolithically on one chip together with the driving, preamplifying and multiplexing circuitry, thus reducing parasitic capacities and noise level significantly. Owing to their low mass the transducers are very well matched to fluid loads, resulting in a very high bandwidth of 50-100% (C. Eccardt et al., Proceedings Ultrasonics Symposium, San Antonio, Vol. 2, 1996, pp. 959-962; P.C. Eccardt et al., Proceedings of the 1997 Ultrasonics Symposium, Toronto, Vol. 2, 1997, pp. 1609-1618). In the following it is shown how

  12. The ultrasound brain helmet: new transducers and volume registration for in vivo simultaneous multi-transducer 3-D transcranial imaging.

    Science.gov (United States)

    Lindsey, Brooks D; Light, Edward D; Nicoletto, Heather A; Bennett, Ellen R; Laskowitz, Daniel T; Smith, Stephen W

    2011-06-01

    Because stroke remains an important and time-sensitive health concern in developed nations, we present a system capable of fusing 3-D transcranial ultrasound volumes acquired from two sides of the head. This system uses custom sparse array transducers built on flexible multilayer circuits that can be positioned for simultaneous imaging through both temporal acoustic windows, allowing for potential registration of multiple real-time 3-D scans of cerebral vasculature. We examine hardware considerations for new matrix arrays-transducer design and interconnects-in this application. Specifically, it is proposed that SNR may be increased by reducing the length of probe cables. This claim is evaluated as part of the presented system through simulation, experimental data, and in vivo imaging. Ultimately, gains in SNR of 7 dB are realized by replacing a standard probe cable with a much shorter flex interconnect; higher gains may be possible using ribbon-based probe cables. In vivo images are presented, showing cerebral arteries with and without the use of microbubble contrast agent; they have been registered and fused using a simple algorithm which maximizes normalized cross-correlation.

  13. An FPGA-based ultrasound imaging system using capacitive micromachined ultrasonic transducers.

    Science.gov (United States)

    Wong, Lawrence L P; Chen, Albert I; Logan, Andrew S; Yeow, John T W

    2012-07-01

    We report the design and experimental results of a field-programmable gate array (FPGA)-based real-time ultrasound imaging system that uses a 16-element phased-array capacitive micromachined ultrasonic transducer fabricated using a fusion bonding process. The imaging system consists of the transducer, discrete analog components situated on a custom-made circuit board, the FPGA, and a monitor. The FPGA program consists of five functional blocks: a main counter, transmit and receive beamformer, receive signal pre-processing, envelope detection, and display. No dedicated digital signal processor or personal computer is required for the imaging system. An experiment is carried out to obtain the sector B-scan of a 4-wire target. The ultrasound imaging system demonstrates the possibility of an integrated system-in-a-package solution.

  14. Quantitative assessment of photoacoustic tomography systems integrating clinical ultrasound transducers using novel tissue-simulating phantoms

    Science.gov (United States)

    Vogt, William C.; Jia, Congxian; Wear, Keith A.; Garra, Brian S.; Pfefer, Joshua

    2015-03-01

    Photoacoustic Tomography (PAT) systems based on commercial ultrasound instruments have the benefit of dualmodality imaging, which increases their appeal from a clinical standpoint. However, factors that influence PAT system performance have not been thoroughly investigated and standardized test methods have not been established for image quality evaluation. To address these issues we have adapted phantom-based approaches from ultrasound imaging standards and implemented them to assess a PAT system developed for vascular imaging. Our system comprises a tunable near-infrared pulsed laser and a commercial ultrasound imaging system, including four interchangeable linear array clinical ultrasound transducers with varying center frequencies, acoustic bandwidths and geometries. Phantoms consisted of a customized polyvinyl chloride (PVC) plastisol gel that simulates both optical and acoustic properties of breast tissue. One phantom incorporates a sub-resolution filament array suitable for bimodal ultrasound-photoacoustic imaging, while another contains an array of hemoglobin-filled cylindrical inclusions at various depths. Key performance characteristics were evaluated, including spatial resolution, signal uniformity, contrast, and penetration depth. These characteristics were evaluated at 750 nm at radiant exposures below ANSI safety limits. Effects of transducer properties on imaging performance were evaluated. Axial and lateral resolution ranged from 0.27-0.83 mm and 0.28-1.8 mm, respectively, and penetration depths from 1.9-4.2 cm were achieved. These results demonstrate variation in PAT system performance based on clinical transducer selection, as well as the utility of realistic phantom-based test methods in performing benchtop evaluations of system performance.

  15. Lead-Free Intravascular Ultrasound Transducer Using BZT-50BCT Ceramics

    Science.gov (United States)

    Yan, Xingwei; Lam, Kwok Ho; Li, Xiang; Chen, Ruimin; Ren, Wei; Ren, Xiaobing; Zhou, Qifa; Shung, K. Kirk

    2013-01-01

    This paper reports the fabrication and evaluation of a high-frequency ultrasonic transducer based on a new lead-free piezoelectric material for intravascular imaging application. Lead-free 0.5Ba(Zr0.2Ti0.8)O3−0.5(Ba0.7Ca0.3)TiO3 (BZT-50BCT) ceramic with a high dielectric constant (~2800) was employed to develop a high-frequency (~30 MHz) needle-type ultrasonic transducer. With superior piezoelectric performance (piezoelectric coefficient d33 ~ 600 pC/N), the lead-free transducer was found to exhibit a −6-dB bandwidth of 53% with an insertion loss of 18.7 dB. In vitro intravascular ultrasound (IVUS) imaging of a human cadaver coronary artery was performed to demonstrate the potential of the lead-free transducer for biomedical imaging applications. This is the first time that a lead-free transducer has been used for IVUS imaging application. The experimental results suggest that the BZT-50BCT ceramic is a promising lead-free piezoelectric material for high-frequency intravascular imaging applications. PMID:25004492

  16. Histotripsy Lesion Formation Using an Ultrasound Imaging Probe Enabled by a Low-Frequency Pump Transducer.

    Science.gov (United States)

    Lin, Kuang-Wei; Hall, Timothy L; Xu, Zhen; Cain, Charles A

    2015-08-01

    advantages: (i) lesion steering can be achieved using the steering of the imaging transducer (implemented with the beamformer of the accompanying programmable ultrasound system), and (ii) treatment can be simultaneously monitored when the imaging transducer is used in conjunction with an ultrasound imaging system. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  17. Single-element focused ultrasound transducer method for harmonic motion imaging.

    Science.gov (United States)

    Maleke, Caroline; Pernot, Mathieu; Konofagou, Elisa E

    2006-07-01

    The harmonic motion imaging (HMI) technique for simultaneous monitoring and generation of ultrasound therapy using two separate focused ultrasound transducer elements was previously demonstrated. In this study, a new HMI technique is described that images tissue displacement induced by a harmonic radiation force using a single focused-ultrasound element. A wave propagation simulation model first indicated that, unlike in the two-beam configuration, the amplitude-modulated beam produced a stable focal zone for the applied harmonic radiation force. The AM beam thus offered the unique advantage of sustaining the application of the spatially-invariant radiation force. Experiments were performed on gelatin phantoms and ex vivo tissues. The radiation force was generated by a 4.68 MHz focused ultrasound (FUS) transducer using a 50 Hz amplitude-modulated wave. A 7.5 MHz pulse-echo transducer was used to acquire rf echoes during the application of the harmonic radiation force. Consecutive rf echoes were acquired with a pulse repetition frequency (PRF) of 6.5 kHz and 1D cross-correlation was performed to estimate the resulting axial tissue displacement. The HMI technique was shown capable of estimating stiffness-dependent displacement amplitudes. Finally, taking advantage of the real-time capability of the HMI technique, temperature-dependent measurements enabled monitoring ofHIFU sonication in ex vivo tissues. The new HMI method may thus enable a highly-localized force and stiffness-dependent measurements as well as real-time and low-cost HIFU monitoring.

  18. Photoacoustic tomography with a high lateral resolution and a large field of view using a rectangular focused ultrasound transducer

    Science.gov (United States)

    Zhang, Shangyu; Cheng, Renxiang; Tao, Chao; Liu, Xiaojun

    2016-04-01

    The enlargement of the field of view (FOV) of a photoacoustic (PA) tomography (PAT) system and the improvement of its lateral resolution are often two conflicting goals. A rectangular focused transducer is proposed to solve this problem. An asymmetric geometry of the transducer results in its asymmetric characteristics of the ultrasound (US) field. Both simulation and experiments confirm that the rectangular focused transducer can improve the FOV and lateral resolution of PAT systems simultaneously. The US transducer proposed in this study has the potential to improve the performance of a PAT system for practical biomedical applications.

  19. Optical micromachined ultrasound transducers (OMUT) - a new approach for high resolution imaging

    Science.gov (United States)

    Tadayon, M. A.; Ashkenazi, S.

    2013-03-01

    Piezoelectric ultrasound (US) transducers are at the heart of almost any ultrasonic medical imaging probe. However, their sensitivity and reliability severely degrade in applications requiring high frequency (>20 MHz) and small element size (construct micron-size air cavities capped by an elastic membrane. The membrane functions as the active ultrasound transmitter and receiver. We will describe the design and testing of prototype OMUT devices which implement a receive-only function. The cavity detector is an optical cavity which its top mirror is deflected under the application of pressure. The intensity of a reflected light beam is highly sensitive to displacement of the top membrane if the optical wavelength is at near-resonance condition. Therefore, US pulses can be detected by recording the reflected light intensity. The sensitivity of the device depends on the mechanical properties of the top membrane and optical characteristics of the optical cavity. The device was fabricated using SU8 as a structural material and gold as a mirror. We have developed a new bonding method to fabricate a sealed, low roughness, high quality optical cavity. The 60μm cavity with the 8.5 μm top membrane is tested in water with 25MHz ultrasound transducer. The NEP of the device for bandwidth of 28MHz was 9.25kPa. The optical cavity has a finesse of around 23.

  20. Analysis of acoustic impedance matching in dual-band ultrasound transducers.

    Science.gov (United States)

    Myhre, Ola Finneng; Johansen, Tonni Franke; Johan Angelsen, Bjørn Atle

    2017-02-01

    Dual-frequency band probes are needed for ultrasound (US) reverberation suppression and are useful for image-guided US therapy. A challenge is to design transducer stacks that achieve high bandwidth and efficiency at both operating frequencies when the frequencies are widely separated with a frequency ratio ∼6:1-20:1. This paper studies the loading and backing conditions of transducers in such stacks. Three stack configurations are presented and analyzed using one-dimensional models. It is shown that a configuration with three layers of material separating the transducers is favorable, as it reduces high frequency ringing by ∼20 dB compared to other designs, and matches the low frequency (LF) transducer to the load at a lower frequency. In some cases, the LF load matching is governed by a simple mass-spring interaction in spite of having a complicated matching structure. The proposed design should yield improved performance of reverberation suppression algorithms. Its suitability for reduction of probe heating, also in single-band probes, should be investigated.

  1. Optimization of acoustic emitted field of transducer array for ultrasound imaging.

    Science.gov (United States)

    He, Zhengyao

    2014-01-01

    A method is proposed to calculate the weight vector of a transducer array for ultrasound imaging to obtain a low-sidelobe transmitting beam pattern based on the near-field response vector. An optimization problem is established, and the second-order cone (SOC) algorithm is used to solve the problem to obtain the weight vector. The optimized acoustic emitted field of the transducer array is then calculated using the Field II program by applying the obtained weight vector to the array. The simulation results with a 64-element 26 MHz linear phased array show that the proposed method can be used to control the sidelobe of the near-field transmitting beam pattern of the transducer array and achieve a low-sidelobe level. The near-field sound pressure distribution of the transducer array using the proposed method focuses much better than that using the standard delay and sum (DAS) beamforming method. The sound energy is more concentrated using the proposed method.

  2. The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.

    Science.gov (United States)

    Mauldin, F William; Owen, Kevin; Tiouririne, Mohamed; Hossack, John A

    2012-06-01

    The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the linear-array geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bone-like) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.

  3. Calculation of pressure fields from arbitrarily shaped, apodized, and excited ultrasound transducers

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Svendsen, Niels Bruun

    1992-01-01

    A method for simulation of pulsed pressure fields from arbitrarily shaped, apodized and excited ultrasound transducers is suggested. It relies on the Tupholme-Stepanishen method for calculating pulsed pressure fields, and can also handle the continuous wave and pulse-echo case. The field...... is calculated by dividing the surface into small rectangles and then Summing their response. A fast calculation is obtained by using the far-field approximation. Examples of the accuracy of the approach and actual calculation times are given...

  4. New technique for fabrication of high frequency piezoelectric Micromachined Ultrasound Transducers

    DEFF Research Database (Denmark)

    Pedersen, T; Thomsen, Erik Vilain; Zawada, T

    2008-01-01

    A novel technique for fabrication of linear arrays of high frequency piezoelectric Micromachined Ultrasound Transducers (pMUT) on silicon substrates is presented. Piezoelectric elements are formed by deposition of PZT ((PbZrxTi1-x)O3) into etched features of the silicon substrate...... such that the depth of these features determine the element thickness and hence the resonance frequency. The process leaves a near planar surface which is ideal for further wafer level processing such as top electrode and interconnect formation. A fabricated single element is characterized by pulse echo response....

  5. A New Method of Designing Electrical Impedance Matching Network for Piezoelectric Ultrasound Transducer

    Directory of Open Access Journals (Sweden)

    Jianfei An

    2014-01-01

    Full Text Available A new method that is based on genetic algorithm (GA is developed to design electrical impedance matching network for broadband piezoelectric ultrasound transducer. The new method can both optimize the topology of the matching network and perform optimization on the components at the same time. Results of classical algorithms are referenced to reduce the number of candidate topologies and greatly simplify the calculation process. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted during optimization to make sure that the algorithm can convergence to global optimal result. Simulation results show that the new method has advantages over designing complex impedance matching network.

  6. Acoustic characterization of multi-element, dual-frequency transducers for high-intensity contact ultrasound therapy

    Science.gov (United States)

    Burtnyk, M.; N'Djin, W. A.; Persaud, L.; Bronskill, M.; Chopra, R.

    2012-10-01

    High-intensity contact ultrasound therapy can generate precise volumes of thermal damage in deep-seated tissue using interstitial or intracavitary devices. Multi-element, dual-frequency transducers offer increased spatial control of the heating pattern by enabling modulation of ultrasound power and frequency along the device. The performance and acoustic coupling between elements of simple, multi-element, dual-frequency transducers was measured. Transducer arrays were fabricated by cutting halfway through a rectangular plate of PZT, creating individual 4 × 5 mm segments with fundamental frequency (4.1 MHz) and third harmonic (13.3 MHz). Coupling between elements was investigated using a scanning laser vibrometer to measure transducer surface displacements at each frequency and different acoustic powers (0, 10, 20 W/cm2). The measured acoustic power was proportional to the input electrical power with no hysteresis and efficiencies >50% at both frequencies. Maximum transducer surface displacements were observed near element centers, reducing to ˜1/3-maximum near edges. The power and frequency of neighboring transducer segments had little impact on an element's output. In the worst case, an element operating at 4.1 MHz and 20 W/cm2 coupled only 1.5 W/cm2 to its immediate neighboring element. Multi-element, dual-frequency transducers were successfully constructed using a simple dicing method. Coupling between elements was minor, therefore the power and frequency of each transducer element could be considered independent.

  7. Improving the thermal dimensional stability of flexible polymer composite backing materials for ultrasound transducers.

    Science.gov (United States)

    State, Mihai; Brands, Peter J; van de Vosse, Frans N

    2010-04-01

    Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast(1265)), a commonly used backing material, was considered reference material and polyurethane composites (PU(2305), PU(2350)) were proposed as better alternatives. When compared to the reference, the PU(2350) filled with a mixture of Al(2)O(3) and tungsten exhibited an approximately 15 times lower glassy transition temperature and a 2.5 time lower longitudinal thermal expansion at 20 degrees C. This ensures that within the entire operational temperature range the backing material is flexible, minimizing the thermal stresses induced onto transducer elements soldered joints and piezoceramic core. For the same material, the attenuation at 5MHz was similar to the reference material while at 7 and 8.5MHz it was 33% and 54% higher respectively. From these analyses it is concluded that the newly developed polyurethane composites outperform the reference backing with respect to the thermal dimensional stability as well as to the damping properties. An integrated rigorous mechano-acoustical approach is being proposed as an appropriate passive material design path. It can be easily extended to any other passive materials used for ultrasound transducer conception.

  8. Numerical simulation of ultrasound thermotherapy of brain with a scanned focus transducer

    Science.gov (United States)

    Behnia, Sohrab; Ghalichi, Farzan; Jafari, Amin; Bonabi, Ashkan

    2005-04-01

    Brain tumors are one of the most difficult ones to treat. The margin between destruction of the tumor and damage to the surrounding tissue is narrow in the brain. Ultrasound could be an effective treatment because of its ability to propagate deep in tissue and induce temperature rise at the focus while leaving the surrounding tissue intact. This study investigates whether using a fix-focus transducer could destroy brain tumor cells, in a cost effective manner which reduces the treatment time significantly. In this work an appropriate fix-focus transducer was designed considering effective parameters and limitations which are dominant in this case. Then a real 2-D brain model was constructed from a MR image. A piece of the skull bone has been removed to allow ultrasound to propagate into the brain. The resultant pressure field and the temperature rise were calculated by Rayleigh integral and bio-heat equation on the model. The obtained results were promising indicating that toxic temperatures could be obtained in short treatment times. This could be of great advantage especially in treating primary brain tumors.

  9. Micromachined PIN-PMN-PT crystal composite transducer for high-frequency intravascular ultrasound (IVUS) imaging.

    Science.gov (United States)

    Li, Xiang; Ma, Teng; Tian, Jian; Han, Pengdi; Zhou, Qifa; Shung, K Kirk

    2014-07-01

    In this paper, we report the use of micromachined PbIn1/2Nb1/2O3-PbMg1/3Nb2/3O3-PbTiO 3 (PIN-PMNPT) single crystal 1-3 composite material for intravascular ultrasound (IVUS) imaging application. The effective electromechanical coupling coefficient kt(eff) of the composite was measured to be 0.75 to 0.78. Acoustic impedance was estimated to be 20 MRayl. Based on the composite, needle-type and flexible-type IVUS transducers were fabricated. The composite transducer achieved an 86% bandwidth at the center frequency of 41 MHz, which resulted in a 43 μm axial resolution. Ex vivo IVUS imaging was conducted to demonstrate the improvement of axial resolution. The composite transducer was capable of identifying the three layers of a cadaver coronary artery specimen with high resolution. The PIN-PMN-PT-based composite has superior piezoelectric properties comparable to PMN-PT-based composite and its thermal stability is higher than PMN-PT. PIN-PMN-PT crystal can be an alternative approach for fabricating high-frequency composite, instead of using PMN-PT.

  10. Micromachined PIN-PMN-PT Crystal Composite Transducer for High-Frequency Intravascular Ultrasound (IVUS) Imaging

    Science.gov (United States)

    Li, Xiang; Ma, Teng; Tian, Jian; Han, Pengdi; Zhou, Qifa; Shung, K. Kirk

    2015-01-01

    In this paper, we report the use of micromachined PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–PbTiO3 (PIN-PMN-PT) single crystal 1–3 composite material for intravascular ultrasound (IVUS) imaging application. The effective electromechanical coupling coefficient kt(eff) of the composite was measured to be 0.75 to 0.78. Acoustic impedance was estimated to be 20 MRayl. Based on the composite, needle-type and flexible-type IVUS transducers were fabricated. The composite transducer achieved an 86% bandwidth at the center frequency of 41 MHz, which resulted in a 43 μm axial resolution. Ex vivo IVUS imaging was conducted to demonstrate the improvement of axial resolution. The composite transducer was capable of identifying the three layers of a cadaver coronary artery specimen with high resolution. The PIN-PMN-PT-based composite has superior piezoelectric properties comparable to PMN-PT-based composite and its thermal stability is higher than PMN-PT. PIN-PMN-PT crystal can be an alternative approach for fabricating high-frequency composite, instead of using PMN-PT. PMID:24960706

  11. Design of a bullet beam pattern of a micro ultrasound transducer (Conference Presentation)

    Science.gov (United States)

    Roh, Yongrae; Lee, Seongmin

    2016-04-01

    Ultrasonic imaging transducer is often required to compose a beam pattern of a low sidelobe level and a small beam width over a long focal region to achieve good image resolution. Normal ultrasound transducers have many channels along its azimuth, which allows easy formation of the sound beam into a desired shape. However, micro-array transducers have no control of the beam pattern along their elevation. In this work, a new method is proposed to manipulate the beam pattern by using an acoustic multifocal lens and a shaded electrode on top of the piezoelectric layer. The shading technique split an initial uniform electrode into several segments and combined those segments to compose a desired beam pattern. For a given elevation width and frequency, the optimal pattern of the split electrodes was determined by means of the OptQuest-Nonlinear Program (OQ-NLP) algorithm to achieve the lowest sidelobe level. The requirement to achieve a small beam width with a long focal region was satisfied by employing an acoustic lens of three multiple focuses. Optimal geometry of the multifocal lens such as the radius of curvature and aperture diameter for each focal point was also determined by the OQ-NLP algorithm. For the optimization, a new index was devised to evaluate the on-axis response: focal region ratio = focal region / minimum beam width. The larger was the focal region ratio, the better was the beam pattern. Validity of the design has been verified through fabricating and characterizing an experimental prototype of the transducer.

  12. Highly precise acoustic calibration method of ring-shaped ultrasound transducer array for plane-wave-based ultrasound tomography

    Science.gov (United States)

    Terada, Takahide; Yamanaka, Kazuhiro; Suzuki, Atsuro; Tsubota, Yushi; Wu, Wenjing; Kawabata, Ken-ichi

    2017-07-01

    Ultrasound computed tomography (USCT) is promising for a non-invasive, painless, operator-independent and quantitative system for breast-cancer screening. Assembly error, production tolerance, and aging-degradation variations of the hardwire components, particularly of plane-wave-based USCT systems, may hamper cost effectiveness, precise imaging, and robust operation. The plane wave is transmitted from a ring-shaped transducer array for receiving the signal at a high signal-to-noise-ratio and fast aperture synthesis. There are four signal-delay components: response delays in the transmitters and receivers and propagation delays depending on the positions of the transducer elements and their directivity. We developed a highly precise calibration method for calibrating these delay components and evaluated it with our prototype plane-wave-based USCT system. Our calibration method was found to be effective in reducing delay errors. Gaps and curves were eliminated from the plane wave, and echo images of wires were sharpened in the entire imaging area.

  13. Single-transducer dual-frequency ultrasound generation to enhance acoustic cavitation.

    Science.gov (United States)

    Liu, Hao-Li; Hsieh, Chao-Ming

    2009-03-01

    Dual- or multiple-frequency ultrasound stimulation is capable of effectively enhancing the acoustic cavitation effect over single-frequency ultrasound. Potential application of this sonoreactor design has been widely proposed such as on sonoluminescence, sonochemistry enhancement, and transdermal drug release enhancement. All currently available sonoreactor designs employed multiple piezoelectric transducers for generating single-frequency ultrasonic waves separately and then these waves were mixed and interfered in solutions. The purpose of this research is to propose a novel design of generating dual-frequency ultrasonic waves with single piezoelectric elements, thereby enhancing acoustic cavitation. Macroscopic bubbles were detected optically, and they were quantified at either a single-frequency or for different frequency combinations for determining their efficiency for enhancing acoustic cavitation. Visible bubbles were optically detected and hydrogen peroxide was measured to quantify acoustic cavitation. Test water samples with different gas concentrations and different power levels were used to determine the efficacy of enhancing acoustic cavitation of this design. The spectrum obtained from the backscattered signals was also recorded and examined to confirm the occurrence of stable cavitation. The results confirmed that single-element dual-frequency ultrasound stimulation can enhance acoustic cavitation. Under certain testing conditions, the generation of bubbles can be enhanced up to a level of five times higher than the generation of bubbles in single-frequency stimulation, and can increase the hydrogen peroxide production up to an increase of one fold. This design may serve as a useful alternative for future sonoreactor design owing to its simplicity to produce dual- or multiple-frequency ultrasound.

  14. Implementation of a Rotational Ultrasound Biomicroscopy System Equipped with a High-Frequency Angled Needle Transducer — Ex Vivo Ultrasound Imaging of Porcine Ocular Posterior Tissues

    Directory of Open Access Journals (Sweden)

    Tae-Hoon Bok

    2014-09-01

    Full Text Available The mechanical scanning of a single element transducer has been mostly utilized for high-frequency ultrasound imaging. However, it requires space for the mechanical motion of the transducer. In this paper, a rotational scanning ultrasound biomicroscopy (UBM system equipped with a high-frequency angled needle transducer is designed and implemented in order to minimize the space required. It was applied to ex vivo ultrasound imaging of porcine posterior ocular tissues through a minimal incision hole of 1 mm in diameter. The retina and sclera for the one eye were visualized in the relative rotating angle range of 270° ~ 330° and at a distance range of 6 ~ 7 mm, whereas the tissues of the other eye were observed in relative angle range of 160° ~ 220° and at a distance range of 7.5 ~ 9 mm. The layer between retina and sclera seemed to be bent because the distance between the transducer tip and the layer was varied while the transducer was rotated. Certin features of the rotation system such as the optimal scanning angle, step angle and data length need to be improved for ensure higher accuracy and precision. Moreover, the focal length should be considered for the image quality. This implementation represents the first report of a rotational scanning UBM system.

  15. Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer.

    Science.gov (United States)

    Zemp, Roger J; Song, Liang; Bitton, Rachel; Shung, K Kirk; Wang, Lihong V

    2008-05-26

    We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frames per second. Clearly resolvable images of 6-microm-diameter carbon fibers are experimentally demonstrated at 80 microm separation distances. Realtime imaging performance is demonstrated on phantoms and in vivo with absorbing structures identified to depths of 2.5-3 mm. This work represents the first high-frequency realtime photoacoustic imaging system to our knowledge.

  16. Reliability of Central Adiposity Assessments Using B-Mode Ultrasound: A Comparison of Linear and Curved Array Transducers.

    Science.gov (United States)

    Stoner, Lee; Geoffron, Morgane; Cornwall, Jon; Chinn, Victoria; Gram, Martin; Credeur, Daniel; Fryer, Simon

    2016-12-01

    Recently, it was reported that intra-abdominal thickness (IAT) assessments using ultrasound are most reliable if measured from the linea alba to the anterior vertebral column. These 2 anatomical sites can be simultaneously visualized using a linear array transducer. Linear array transducers have different operational characteristics when compared with conventional curved array transducers and are more reliable for some ultrasound-derived measures such as abdominal subcutaneous fat thickness. However, it is unknown whether linear array transducers facilitate more reliable IAT measurements than curved array transducers. The purpose of the current study was to (1) compare the reliability of linear and curved array transducer assessments of IAT and maximal abdominal ratio (MAR) and (2) use the findings to update central adiposity measurement guidelines. Fifteen healthy adults (mean [SD], 27 [10] years; 60% female) with a range of somatotypes (body mass index: mean [SD], 24 [4]; range, 19-33 kg/m; waist circumference: mean [SD], 75 [11]; range, 61-96 cm) were tested on 3 mornings under standardized conditions. Intra-abdominal thickness was assessed 2 cm above the umbilicus (transverse plane), measuring from linea alba to the anterior vertebral column. Maximal abdominal ratio was defined as the ratio of IAT to abdominal subcutaneous fat thickness. The IAT range was 25 to 87 mm, and the MAR range was 0.15 to 0.77. Between-day intraclass correlation coefficient values for IAT measurements made were comparable (0.96-0.97) for both transducers, as were MAR values (0.95). In conclusion, while both transducers provided equally reliable measurement of IAT, the use of a single linear array transducer simplifies the assessment of central adiposity.

  17. Brachial artery vasomotion and transducer pressure effect on measurements by active contour segmentation on ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Cary, Theodore W.; Sultan, Laith R.; Sehgal, Chandra M., E-mail: sehgalc@uphs.upenn.edu [Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Reamer, Courtney B.; Mohler, Emile R. [Department of Medicine, Division of Cardiovascular Medicine, Section of Vascular Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2014-02-15

    Purpose: To use feed-forward active contours (snakes) to track and measure brachial artery vasomotion on ultrasound images recorded in both transverse and longitudinal views; and to compare the algorithm's performance in each view. Methods: Longitudinal and transverse view ultrasound image sequences of 45 brachial arteries were segmented by feed-forward active contour (FFAC). The segmented regions were used to measure vasomotion artery diameter, cross-sectional area, and distention both as peak-to-peak diameter and as area. ECG waveforms were also simultaneously extracted frame-by-frame by thresholding a running finite-difference image between consecutive images. The arterial and ECG waveforms were compared as they traced each phase of the cardiac cycle. Results: FFAC successfully segmented arteries in longitudinal and transverse views in all 45 cases. The automated analysis took significantly less time than manual tracing, but produced superior, well-behaved arterial waveforms. Automated arterial measurements also had lower interobserver variability as measured by correlation, difference in mean values, and coefficient of variation. Although FFAC successfully segmented both the longitudinal and transverse images, transverse measurements were less variable. The cross-sectional area computed from the longitudinal images was 27% lower than the area measured from transverse images, possibly due to the compression of the artery along the image depth by transducer pressure. Conclusions: FFAC is a robust and sensitive vasomotion segmentation algorithm in both transverse and longitudinal views. Transverse imaging may offer advantages over longitudinal imaging: transverse measurements are more consistent, possibly because the method is less sensitive to variations in transducer pressure during imaging.

  18. Development of a 20-MHz wide-bandwidth PMN-PT single crystal phased-array ultrasound transducer.

    Science.gov (United States)

    Wong, Chi-Man; Chen, Yan; Luo, Haosu; Dai, Jiyan; Lam, Kwok-Ho; Chan, Helen Lai-Wa

    2017-01-01

    In this study, a 20-MHz 64-element phased-array ultrasound transducer with a one-wavelength pitch is developed using a PMN-30%PT single crystal and double-matching layer scheme. High piezoelectric (d33>1000pC/N) and electromechanical coupling (k33>0.8) properties of the single crystal with an optimized fabrication process involving the photolithography technique have been demonstrated to be suitable for wide-bandwidth (⩾70%) and high-sensitivity (insertion loss ⩽30dB) phased-array transducer application. A -6dBbandwidth of 91% and an insertion loss of 29dBfor the 20-MHz 64-element phased-array transducer were achieved. This result shows that the bandwidth is improved comparing with the investigated high-frequency (⩾20MHz) ultrasound transducers using piezoelectric ceramic and single crystal materials. It shows that this phased-array transducer has potential to improve the resolution of biomedical imaging, theoretically. Based on the hypothesis of resolution improvement, this phased-array transducer is capable for small animal (i.e. mouse and zebrafish) studies.

  19. 2D sparse array transducer optimization for 3D ultrasound imaging

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jae Hoon; Park, Kwan Kyu [Dept. of Mechanical Convergence Engineering, Hanyang University, Seoul (Korea, Republic of)

    2016-12-15

    A 3D ultrasound image is desired in many medical examinations. However, the implementation of a 2D array, which is needed for a 3D image, is challenging with respect to fabrication, interconnection and cabling. A 2D sparse array, which needs fewer elements than a dense array, is a realistic way to achieve 3D images. Because the number of ways the elements can be placed in an array is extremely large, a method for optimizing the array configuration is needed. Previous research placed the target point far from the transducer array, making it impossible to optimize the array in the operating range. In our study, we focused on optimizing a 2D sparse array transducer for 3D imaging by using a simulated annealing method. We compared the far-field optimization method with the near-field optimization method by analyzing a point-spread function (PSF). The resolution of the optimized sparse array is comparable to that of the dense array.

  20. Evaluation of a novel therapeutic focused ultrasound transducer based on Fermat’s spiral

    Science.gov (United States)

    Ramaekers, P.; de Greef, M.; Berriet, R.; Moonen, C. T. W.; Ries, M.

    2017-06-01

    The purpose of this study was to evaluate a novel phased array transducer design rule for therapeutic focused ultrasound applications. This design rule uses the discretized Fermat’s spiral to determine the positioning of the transducer elements for a given number of elements and f-number. Using this principle, three variations of Fermat’s spiral were generated, aimed at (1) grating lobe minimization, (2) side lobe minimization, and (3) an optimized element packing efficiency. For each spiral, sparse layouts using identical circular elements and fully populated layouts based on additional Voronoi tessellation were evaluated numerically. Evaluation criteria included the element size distribution, beam steering capabilities, focal plane pressure distribution, prefocal pressure distribution, and practical considerations. Finally, one Voronoi-tessellated design with a focal length and aperture diameter of 16 cm and a natural frequency of 1.3 MHz was evaluated experimentally through hydrophone measurements. The numerical evaluation showed that while sparse arrays possess superior beam steering capabilities for a given number of elements, the focal point quality and prefocal pressure distribution is substantially more favorable when using the Voronoi-tessellated designs. Beam steering was shown to be feasible with the tessellated designs for lateral deflections up to 10 mm and axial deflections up to 20 mm. The experimental evaluation showed that such a transducer is capable of inducing 40.00 MPa rarefactional and 237.50 MPa compressional peak pressure levels at 800 W instantaneous acoustic output power under free-field conditions, making the system potentially relevant for thermal ablation therapy, histotripsy applications, and shockwave-enhanced heating.

  1. Photoacoustic Tomography Imaging of the Adult Zebrafish by Using Unfocused and Focused High-Frequency Ultrasound Transducers

    Directory of Open Access Journals (Sweden)

    Yubin Liu

    2016-11-01

    Full Text Available The zebrafish model provides an essential platform for the study of human diseases or disorders due to the possession of about 87% homologous genes with human. However, it is still very challenging to noninvasively visualize the structure and function of adult zebrafish based on available optical imaging techniques. In this study, photoacoustic tomography (PAT was utilized for high-resolution imaging of adult zebrafish by using focused and unfocused high-frequency (10 MHz ultrasound transducers. We examined and compared the imaging results from the two categories of transducers with in vivo experimental tests, in which we discovered that the unfocused transducer is able to identify the inner organs of adult zebrafish with higher contrast but limited regional resolution, whereas the findings from the focused transducer were with high resolution but limited regional contrast for the recovered inner organs.

  2. Advanced 3-D Ultrasound Imaging: 3-D Synthetic Aperture Imaging using Fully Addressed and Row-Column Addressed 2-D Transducer Arrays

    DEFF Research Database (Denmark)

    Bouzari, Hamed

    with transducer arrays using this addressing scheme, when integrated into probe handles. For that reason, two in-house prototyped 62+62 row-column addressed 2-D array transducer probes were manufactured using capacitive micromachined ultrasonic transducer (CMUT) and piezoelectric transducer (PZT) technology...... in many clinical applications. Real-time 3-D ultrasound imaging is still not as widespread in use in the clinics as 2-D ultrasound imaging. Two limiting factors have traditionally been the low image quality as well as low volume rate achievable with a 2-D transducer array using the conventional 3-D...... and measurements with the ultrasound research scanner SARUS and a 3.8 MHz 1024 element 2-D transducer array. In all investigations, 3-D synthetic aperture imaging achieved a better resolution, lower side-lobes, higher contrast, and better signal to noise ratio than parallel beamforming. This is achieved partly...

  3. A 3D reconstruction algorithm for magneto-acoustic tomography with magnetic induction based on ultrasound transducer characteristics

    Science.gov (United States)

    Ma, Ren; Zhou, Xiaoqing; Zhang, Shunqi; Yin, Tao; Liu, Zhipeng

    2016-12-01

    In this study we present a three-dimensional (3D) reconstruction algorithm for magneto-acoustic tomography with magnetic induction (MAT-MI) based on the characteristics of the ultrasound transducer. The algorithm is investigated to solve the blur problem of the MAT-MI acoustic source image, which is caused by the ultrasound transducer and the scanning geometry. First, we established a transducer model matrix using measured data from the real transducer. With reference to the S-L model used in the computed tomography algorithm, a 3D phantom model of electrical conductivity is set up. Both sphere scanning and cylinder scanning geometries are adopted in the computer simulation. Then, using finite element analysis, the distribution of the eddy current and the acoustic source as well as the acoustic pressure can be obtained with the transducer model matrix. Next, using singular value decomposition, the inverse transducer model matrix together with the reconstruction algorithm are worked out. The acoustic source and the conductivity images are reconstructed using the proposed algorithm. Comparisons between an ideal point transducer and the realistic transducer are made to evaluate the algorithms. Finally, an experiment is performed using a graphite phantom. We found that images of the acoustic source reconstructed using the proposed algorithm are a better match than those using the previous one, the correlation coefficient of sphere scanning geometry is 98.49% and that of cylinder scanning geometry is 94.96%. Comparison between the ideal point transducer and the realistic transducer shows that the correlation coefficients are 90.2% in sphere scanning geometry and 86.35% in cylinder scanning geometry. The reconstruction of the graphite phantom experiment also shows a higher resolution using the proposed algorithm. We conclude that the proposed reconstruction algorithm, which considers the characteristics of the transducer, can obviously improve the resolution of the

  4. Effects of increased compression with an ultrasound transducer on the conspicuity of breast lesions in a phantom

    Science.gov (United States)

    Szczepura, Katy; Faqir, Tahreem; Manning, David

    2017-03-01

    Ultrasound imaging of the breast is highly operator dependent. The amount of pressure applied with the transducer has a direct impact on the lesion visibility in breast ultrasound. The conspicuity index is a quantitative measure of lesion visibility, taking into account more parameters than standard measures that impact on lesion detection. This study assessed the conspicuity of lesions within a breast phantom using increased transducer compression in breast ultrasound. Methods A phantom was constructed of gelatine to represent adipose tissue, steel wool for glandular/blood vessels and silicone spheres to represent lesions, this meant that the lesions were also compressible, but less than the surrounding tissue. The phantom was imaged under increasing transducer compression. The conspicuity index was measured using the Conspicuity Index Software. The distance between the transducer surface and lesion surface was measured as an indication of increased compression. Results When moderate compression (17mm) was applied, the conspicuity index increased resulting in better visualisation of the silicone lesions. However, with increased compression the conspicuity index decreased. New work to be presented The conspicuity index has never been demonstrated in ultrasound imaging before. This is preliminary phantom work to demonstrate the impact of increased transducer compression on quantitative lesion visibility assessment. Conclusion The compression applied should be considered for optimum visualisation, as excessive pressure decreases conspicuity. However, further work needs to be conducted in order to consider other factors, such as density of the breast and lesion location, for a better understanding of the effect of compression on the visualisation of the lesion. A human study is planned.

  5. Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia.

    Science.gov (United States)

    Hyler, Stefan; Pischke, Søren E; Halvorsen, Per Steinar; Espinoza, Andreas; Bergsland, Jacob; Tønnessen, Tor Inge; Fosse, Erik; Skulstad, Helge

    2015-04-01

    Sensitive methods for the early detection of myocardial dysfunction are still needed, as ischemia is a leading cause of decreased ventricular function during and after heart surgery. The aim of this study was to test the hypothesis that low-grade ischemia could be detected quantitatively by a miniaturized epicardial ultrasound transducer (Ø = 3 mm), allowing continuous monitoring. In 10 pigs, transducers were positioned in the left anterior descending and circumflex coronary artery areas. Left ventricular pressure was obtained by a micromanometer. The left internal mammary artery was grafted to the left anterior descending coronary artery, which was occluded proximal to the anastomosis. Left internal mammary artery flow was stepwise reduced by 25%, 50%, and 75% for 18 min each. From the transducers, M-mode traces were obtained, allowing continuous tissue velocity traces and displacement measurements. Regional work was assessed as left ventricular pressure-displacement loop area. Tissue lactate measured from intramyocardial microdialysis was used as reference method to detect ischemia. All steps of coronary flow reduction demonstrated reduced peak systolic velocity (P transducer allowed the precise detection of different levels of coronary flow reduction. The results also showed a quantitative and linear relationship among coronary flow, ischemia, and myocardial function. Thus, the ultrasound transducer has the potential to improve the monitoring of myocardial ischemia and to detect graft failure during and after heart surgery. Copyright © 2015 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

  6. User-guided segmentation of preterm neonate ventricular system from 3-D ultrasound images using convex optimization.

    Science.gov (United States)

    Qiu, Wu; Yuan, Jing; Kishimoto, Jessica; McLeod, Jonathan; Chen, Yimin; de Ribaupierre, Sandrine; Fenster, Aaron

    2015-02-01

    A three-dimensional (3-D) ultrasound (US) system has been developed to monitor the intracranial ventricular system of preterm neonates with intraventricular hemorrhage (IVH) and the resultant dilation of the ventricles (ventriculomegaly). To measure ventricular volume from 3-D US images, a semi-automatic convex optimization-based approach is proposed for segmentation of the cerebral ventricular system in preterm neonates with IVH from 3-D US images. The proposed semi-automatic segmentation method makes use of the convex optimization technique supervised by user-initialized information. Experiments using 58 patient 3-D US images reveal that our proposed approach yielded a mean Dice similarity coefficient of 78.2% compared with the surfaces that were manually contoured, suggesting good agreement between these two segmentations. Additional metrics, the mean absolute distance of 0.65 mm and the maximum absolute distance of 3.2 mm, indicated small distance errors for a voxel spacing of 0.22 × 0.22 × 0.22 mm(3). The Pearson correlation coefficient (r = 0.97, p < 0.001) indicated a significant correlation of algorithm-generated ventricular system volume (VSV) with the manually generated VSV. The calculated minimal detectable difference in ventricular volume change indicated that the proposed segmentation approach with 3-D US images is capable of detecting a VSV difference of 6.5 cm(3) with 95% confidence, suggesting that this approach might be used for monitoring IVH patients' ventricular changes using 3-D US imaging. The mean segmentation times of the graphics processing unit (GPU)- and central processing unit-implemented algorithms were 50 ± 2 and 205 ± 5 s for one 3-D US image, respectively, in addition to 120 ± 10 s for initialization, less than the approximately 35 min required by manual segmentation. In addition, repeatability experiments indicated that the intra-observer variability ranges from 6.5% to 7.5%, and the inter-observer variability is 8.5% in terms

  7. Monitoring of high-intensity focused ultrasound treatment by shear wave elastography induced by two-dimensional-array therapeutic transducer

    Science.gov (United States)

    Iwasaki, Ryosuke; Takagi, Ryo; Nagaoka, Ryo; Jimbo, Hayato; Yoshizawa, Shin; Saijo, Yoshifumi; Umemura, Shin-ichiro

    2016-07-01

    Shear wave elastography (SWE) is expected to be a noninvasive monitoring method of high-intensity focused ultrasound (HIFU) treatment. However, conventional SWE techniques encounter difficulty in inducing shear waves with adequate displacements in deep tissue. To observe tissue coagulation at the HIFU focal depth via SWE, in this study, we propose using a two-dimensional-array therapeutic transducer for not only HIFU exposure but also creating shear sources. The results show that the reconstructed shear wave velocity maps detected the coagulated regions as the area of increased propagation velocity even in deep tissue. This suggests that “HIFU-push” shear elastography is a promising solution for the purpose of coagulation monitoring in deep tissue, because push beams irradiated by the HIFU transducer can naturally reach as deep as the tissue to be coagulated by the same transducer.

  8. Ultrasound (US transducer of higher operating frequency detects photoacoustic (PA signals due to the contrast in elastic property

    Directory of Open Access Journals (Sweden)

    Mayanglambam Suheshkumar Singh

    2016-02-01

    Full Text Available We report our study that shows selection in operating frequency of US-transducer used for boundary detection of PA-signals, which result due to the contrast in elastic property distribution ( E ( r → in sample material other than that of optical absorption coefficient (μa. Studies were carried out, experimentally, in tissue-mimicking Agar phantoms employing acoustic resolution photoacoustic microscopy (AR-PAM system as an imaging unit. In the experiments, various transducers having different operating frequencies, ranging from 1MHz to 50MHz, were employed for studying frequency response of the photoacoustic signals. The study shows that, for detecting photoacoustic signals due to the contrast in elastic property, ultrasound transducer with higher operating frequency (∼50MHz is demanded.

  9. Polyimide-etalon all-optical ultrasound transducer for high frequency applications

    Science.gov (United States)

    Sheaff, Clay; Ashkenazi, Shai

    2014-03-01

    We have enhanced our design for an all-optical high frequency ultrasound transducer consisting of a UV-absorbing polyimide film integrated into an etalon receiver operating in the NIR range. A dielectric stack having high NIR reflectivity and high UV transmittance was chosen as the first mirror for increased sensitivity and the allowance of polyimide as the etalon medium. A 13 ns, 0.7 μJ optical pulse at 355 nm and a continuous-wave NIR laser were focused onto the structure with a spot diameter of 120 and 35 μm, respectively. In receive mode the etalon had a noise-equivalent pressure of 4.1 kPa over a bandwidth of 5 - 50 MHz (0.61 Pa/√Hz ). The device generated a pressure of 270 kPa at a depth of 200 μm, and the -3 dB bandwidth of the emission extended from 27 to 60 MHz. In transmit/receive mode, the pulse-echo had a center frequency of 35 MHz with a -6 dB bandwidth of 49 MHz (140 %). Lastly, wire targets were imaged by scanning the UV spot to create a synthetic aperture of transmitters centered upon a single receiver.

  10. X-ray-induced acoustic computed tomography with an ultrasound transducer ring-array

    Science.gov (United States)

    Tang, S.; Nguyen, D. H.; Zarafshani, A.; Ramseyer, C.; Zheng, B.; Liu, H.; Xiang, L.

    2017-03-01

    The objective of this study is to develop and test a unique X-ray-induced acoustic computed tomography system that combines the advantages of high X-ray imaging contrast and high ultrasonic spatial resolution. The system features a 5 MHz 128-element ultrasound transducer ring-array formed into a full circular aperture. A parallel data receiver, which consists of a dedicated 128-channel preamplifier and a 128-channel data acquisition module, provides full tomographic imaging at a speed of up to 25 frames per second. Details of the system design and calibration are presented, along with the characteristic results of the imaging resolution. The tomographic imaging performance is demonstrated through images of a phantom with a spatial resolution up to 138 μm. The study results indicate that this imaging device and the methodology provide a rapid and high resolution approach for the dynamic imaging of information, and it may have the potential for becoming a promising noninvasive imaging modality to be used in future applications.

  11. Feasibility study for removing calcified material using a planar rectangular ultrasound transducer.

    Science.gov (United States)

    Damianou, Christakis; Couppis, Andreas

    2016-01-01

    The aim of the proposed study was to conduct a feasibility study using a flat rectangular (3 mm × 10 mm) MRI compatible transducer operating at 5.3 MHz for destroying calcified material in an in vitro model. The proposed method can be used in the future for treating atherosclerosis plaques of the coronary, carotid or peripheral arteries. The system was tested initially on calcium rods. Another test was performed in a hydroxyapatite-polylactide model. A parametric study was performed where the mass of calcified material removed was studied as a function of intensity, pulse repetition frequency (PRF), duty factor (DF) and presence of bubbles. The amount of calcified material removed is directly related to the intensity, PRF and DF. It was found that the presence of bubbles accelerates the removal of calcified material. In order to ensure that pure mechanical mode ultrasound was used, the protocols were designed so that the temperature does not exceed 1 °C.

  12. Theory and operation of 2-D array piezoelectric micromachined ultrasound transducers.

    Science.gov (United States)

    Dausch, David E; Castellucci, John B; Chou, Derrick R; von Ramm, Olaf T

    2008-11-01

    Piezoelectric micromachined ultrasound transducers (pMUTs) are a new approach for the construction of 2-D arrays for forward-looking 3-D intravascular (IVUS) and intracardiac (ICE) imaging. Two-dimensional pMUT test arrays containing 25 elements (5 x 5 arrays) were bulk micromachined in silicon substrates. The devices consisted of lead zirconate titanate (PZT) thin film membranes formed by deep reactive ion etching of the silicon substrate. Element widths ranged from 50 to 200 microm with pitch from 100 to 300 mum. Acoustic transmit properties were measured in de-ionized water with a calibrated hydrophone placed at a range of 20 mm. Measured transmit frequencies for the pMUT elements ranged from 4 to 13 MHz, and mode of vibration differed for the various element sizes. Element capacitance varied from 30 to over 400 pF depending on element size and PZT thickness. Smaller element sizes generally produced higher acoustic transmit output as well as higher frequency than larger elements. Thicker PZT layers also produced higher transmit output per unit electric field applied. Due to flexure mode operation above the PZT coercive voltage, transmit output increased nonlinearly with increased drive voltage. The pMUT arrays were attached directly to the Duke University T5 Phased Array Scanner to produce real-time pulse-echo B-mode images with the 2-D pMUT arrays.

  13. Design, simulation and testing of capacitive micromachined ultrasound transducer-based phospholipidic biosensor elements

    Science.gov (United States)

    Sapeliauskas, E.; Vanagas, G.; Barauskas, D.; Mikolajunas, M.; Pakenas, E.; Pelenis, D.; Sergalis, G.; Jukna, T.; Virzonis, D.

    2015-07-01

    In this study we present theoretical proof of the principle of using interdigital capacitive micromachined ultrasound transducers (CMUT IDTs) for the detection of phospholipid membrane elasticity. Proof of principle was needed to find out whether the new type of microelectromechanical sensors of the toxins incorporated with the lipid membranes was feasible. CMUT IDTs for 10 MHz operation in water, with 146 µm spaced double fingers were designed and fabricated using the surface micromachining technique. Fabricated CMUTs were tested for their resonance in air and for Scholte-type wave transmission in deionized water and isopropanol solutions containing 0%, 10% and 20% water. The amplitude and phase velocity of the excited and received Scholte waves were measured in a 200 µm height microchannel, capped with a thick layer of soft polymer, which suppressed the production of non-informative guided waves. It was determined that the average sensitivity of Scholte wave phase velocity within the given range of solution concentrations is 2.9 m s-1 per one percent. Experimental data were also used to verify the adequacy of the finite element model, which was found to be suitable for reliable prediction of the phospholipid membrane elasticity impact on the Scholte wave phase velocity or the resonance frequency in the present IDT structure. It was determined that for the analyzed conditions (the elasticity of simulated phospholipid membrane changed from 1 to 5 GPa) the sensitivity of the measurement channel is expected to be no worse than 2 kHz GPa-1 in terms of the Scholte wave and CMUT IDT resonance frequency. This leads to a positive conclusion on the feasibility of the new sensor type.

  14. Validity and reliability of rectus femoris ultrasound measurements: Comparison of curved-array and linear-array transducers

    Directory of Open Access Journals (Sweden)

    Kendra Hammond, MD

    2014-11-01

    Full Text Available Muscle-mass loss augers increased morbidity and mortality in critically ill patients. Muscle-mass loss can be assessed by wide linear-array ultrasound transducers connected to cumbersome, expensive console units. Whether cheaper, hand-carried units equipped with curved-array transducers can be used as alternatives is unknown. Accordingly, our primary aim was to investigate in 15 nondisabled subjects the validity of measurements of rectus femoris cross-sectional area by using a curved-array transducer against a linear-array transducer—the reference-standard technique. In these subjects, we also determined the reliability of measurements obtained by a novice operator versus measurements obtained by an experienced operator. Lastly, the relationship between quadriceps strength and rectus area recorded by two experienced operators with a curved-array transducer was assessed in 17 patients with chronic obstructive pulmonary disease (COPD. In nondisabled subjects, the rectus cross-sectional area measured with the curved-array transducer by the novice and experienced operators was valid (intraclass correlation coefficient [ICC]: 0.98, typical percentage error [%TE]: 3.7% and reliable (ICC: 0.79, %TE: 9.7%. In the subjects with COPD, both reliability (ICC: 0.99 and repeatability (%TE: 7.6% and 9.8% were high. Rectus area was related to quadriceps strength in COPD for both experienced operators (coefficient of determination: 0.67 and 0.70. In conclusion, measurements of rectus femoris cross-sectional area recorded with a curved-array transducer connected to a hand-carried unit are valid, reliable, and reproducible, leading us to contend that this technique is suitable for cross-sectional and longitudinal studies.

  15. Particle image velocimetry on simulated 3D ultrafast ultrasound from pediatric matrix TEE transducers

    Science.gov (United States)

    Voorneveld, J. D.; Bera, D.; van der Steen, A. F. W.; de Jong, N.; Bosch, J. G.

    2017-03-01

    Ultrafast 3D transesophageal echocardiographic (TEE) imaging, combined with 3D echo particle image velocimetry (ePIV), would be ideal for tracking the complex blood flow patterns in the heart. We are developing a miniature pediatric matrix TEE transducer that employs micro-beamforming (μBF) and allows high framerate in 3D. In this paper, we assess the feasibility of 3D ePIV with a high frame rate, small aperture transducer and the influence of the micro-beamforming technique. We compare the results of 3D ePIV on simulated images using the μBF transducer and an idealized, fully sampled (FS) matrix transducer. For the two transducers, we have simulated high-framerate imaging of an 8.4mm diameter artery having a known 4D velocity field. The simulations were performed in FieldII. 1000 3D volumes, at a rate of 1000 volumes/sec, were created using a single diverging transmission per volume. The error in the 3D velocity estimation was measured by comparing the ePIV results of both transducers to the ground truth. The results on the simulated volumes show that ePIV can estimate the 4D velocity field of the arterial phantom using these small-aperture transducers suitable for pediatric 3D TEE. The μBF transducer (RMSE 44.0%) achieved comparable ePIV accuracy to that of the FS transducer (RMSE 42.6%).

  16. Setting boundary conditions on the Khokhlov-Zabolotskaya equation for modeling ultrasound fields generated by strongly focused transducers

    Science.gov (United States)

    Rosnitskiy, P. B.; Yuldashev, P. V.; Vysokanov, B. A.; Khokhlova, V. A.

    2016-03-01

    An equivalent source model is developed for setting boundary conditions on the parabolic diffraction equation in order to simulate ultrasound fields radiated by strongly focused medical transducers. The equivalent source is defined in a plane; corresponding boundary conditions for pressure amplitude, aperture, and focal distance are chosen so that the axial solution to the parabolic model in the focal region of the beam matches the solution to the full diffraction model (Rayleigh integral) for a spherically curved uniformly vibrating source. It is shown that the proposed approach to transferring the boundary condition from a spherical surface to a plane makes it possible to match the solutions over an interval of several diffraction maxima around the focus even for focused sources with F-numbers less than unity. This method can be used to accurately simulate nonlinear effects in the fields of strongly focused therapeutic transducers using the parabolic Khokhlov-Zabolotskaya equation.

  17. Reflection-mode photoacoustic microscopy using a hollow focused ultrasound transducer for in vivo imaging of blood vessels

    Institute of Scientific and Technical Information of China (English)

    Yuan Yi; Yang Si-Hua

    2012-01-01

    A reflection-mode photoacoustic microscope using a hollow focused ultrasound transducer is developed for highresolution in vivo imaging.A confocal structure of the laser and the ultrasound is used to improve the system resolution.The axial and lateral resolutions of the system are measured to be~32 μm and~58 μm,respectively.Ex vivo and in vivo modes are tested to validate the imaging capability of the photoacoustic microscope.The adjacent vein and artery can be seen clearly from the reconstructed photoacoustic images.The results demonstrate that the reflectionmode photoacoustic microscope can be used for high-resolution imaging of micro-blood vessels,which would be of great benefit for monitoring the neovascularization in tumor angiogenesis.

  18. Optimal design of a piezoelectric transducer for exciting guided wave ultrasound in rails

    Science.gov (United States)

    Ramatlo, Dineo A.; Wilke, Daniel N.; Loveday, Philip W.

    2017-02-01

    An existing Ultrasonic Broken Rail Detection System installed in South Africa on a heavy duty railway line is currently being upgraded to include defect detection and location. To accomplish this, an ultrasonic piezoelectric transducer to strongly excite a guided wave mode with energy concentrated in the web (web mode) of a rail is required. A previous study demonstrated that the recently developed SAFE-3D (Semi-Analytical Finite Element - 3 Dimensional) method can effectively predict the guided waves excited by a resonant piezoelectric transducer. In this study, the SAFE-3D model is used in the design optimization of a rail web transducer. A bound-constrained optimization problem was formulated to maximize the energy transmitted by the transducer in the web mode when driven by a pre-defined excitation signal. Dimensions of the transducer components were selected as the three design variables. A Latin hypercube sampled design of experiments that required a total of 500 SAFE-3D analyses in the design space was employed in a response surface-based optimization approach. The Nelder-Mead optimization algorithm was then used to find an optimal transducer design on the constructed response surface. The radial basis function response surface was first verified by comparing a number of predicted responses against the computed SAFE-3D responses. The performance of the optimal transducer predicted by the optimization algorithm on the response surface was also verified to be sufficiently accurate using SAFE-3D. The computational advantages of SAFE-3D in optimal transducer design are noteworthy as more than 500 analyses were performed. The optimal design was then manufactured and experimental measurements were used to validate the predicted performance. The adopted design method has demonstrated the capability to automate the design of transducers for a particular rail cross-section and frequency range.

  19. Dual-Element Transducer with Phase-Inversion for Wide Depth of Field in High-Frequency Ultrasound Imaging

    Directory of Open Access Journals (Sweden)

    Jong Seob Jeong

    2014-08-01

    Full Text Available In high frequency ultrasound imaging (HFUI, the quality of focusing is deeply related to the length of the depth of field (DOF. In this paper, a phase-inversion technique implemented by a dual-element transducer is proposed to enlarge the DOF. The performance of the proposed method was numerically demonstrated by using the ultrasound simulation program called Field-II. A simulated dual-element transducer was composed of a disc- and an annular-type elements, and its aperture was concavely shaped to have a confocal point at 6 mm. The area of each element was identical in order to provide same intensity at the focal point. The outer diameters of the inner and the outer elements were 2.1 mm and 3 mm, respectively. The center frequency of each element was 40 MHz and the f-number (focal depth/aperture size was two. When two input signals with 0° and 180° phases were applied to inner and outer elements simultaneously, a multi-focal zone was generated in the axial direction. The total −6 dB DOF, i.e., sum of two −6 dB DOFs in the near and far field lobes, was 40% longer than that of the conventional single element transducer. The signal to noise ratio (SNR was increased by about two times, especially in the far field. The point and cyst phantom simulation were conducted and their results were identical to that of the beam pattern simulation. Thus, the proposed scheme may be a potential method to improve the DOF and SNR in HFUI.

  20. Effect of Transducer Orientation on Errors in Ultrasound Image-Based Measurements of Human Medial Gastrocnemius Muscle Fascicle Length and Pennation.

    Science.gov (United States)

    Bolsterlee, Bart; Gandevia, Simon C; Herbert, Robert D

    2016-01-01

    Ultrasound imaging is often used to measure muscle fascicle lengths and pennation angles in human muscles in vivo. Theoretically the most accurate measurements are made when the transducer is oriented so that the image plane aligns with muscle fascicles and, for measurements of pennation, when the image plane also intersects the aponeuroses perpendicularly. However this orientation is difficult to achieve and usually there is some degree of misalignment. Here, we used simulated ultrasound images based on three-dimensional models of the human medial gastrocnemius, derived from magnetic resonance and diffusion tensor images, to describe the relationship between transducer orientation and measurement errors. With the transducer oriented perpendicular to the surface of the leg, the error in measurement of fascicle lengths was about 0.4 mm per degree of misalignment of the ultrasound image with the muscle fascicles. If the transducer is then tipped by 20°, the error increases to 1.1 mm per degree of misalignment. For a given degree of misalignment of muscle fascicles with the image plane, the smallest absolute error in fascicle length measurements occurs when the transducer is held perpendicular to the surface of the leg. Misalignment of the transducer with the fascicles may cause fascicle length measurements to be underestimated or overestimated. Contrary to widely held beliefs, it is shown that pennation angles are always overestimated if the image is not perpendicular to the aponeurosis, even when the image is perfectly aligned with the fascicles. An analytical explanation is provided for this finding.

  1. 80-MHz intravascular ultrasound transducer using PMN-PT free-standing film.

    Science.gov (United States)

    Li, Xiang; Wu, Wei; Chung, Youngsoo; Shih, Wan Y; Shih, Wei-Heng; Zhou, Qifa; Shung, K Kirk

    2011-11-01

    [Pb(Mg(1/3)Nb(2/3))O(3)](0.63)[PbTiO(3)](0.37) (PMN-PT) free-standing film of comparable piezoelectric properties to bulk material with thickness of 30 μm has been fabricated using a modified precursor coating approach. At 1 kHz, the dielectric permittivity and loss were 4364 and 0.033, respectively. The remnant polarization and coercive field were 28 μC/cm(2) and 18.43 kV/cm. The electromechanical coupling coefficient k(t) was measured to be 0.55, which was close to that of bulk PMN-PT single-crystal material. Based on this film, high-frequency (82 MHz) miniature ultrasonic transducers were fabricated with 65% bandwidth and 23 dB insertion loss. Axial and lateral resolutions were determined to be as high as 35 and 176 μm. In vitro intravascular imaging on healthy rabbit aorta was performed using the thin film transducers. In comparison with a 35-MHz IVUS transducer, the 80-MHz transducer showed superior resolution and contrast with satisfactory penetration depth. The imaging results suggest that PMN-PT free-standing thin film technology is a feasible and efficient way to fabricate very-high-frequency ultrasonic transducers.

  2. Convexity Adjustments

    DEFF Research Database (Denmark)

    M. Gaspar, Raquel; Murgoci, Agatha

    2010-01-01

    of particular importance to practitioners: yield convexity adjustments, forward versus futures convexity adjustments, timing and quanto convexity adjustments. We claim that the appropriate way to look into any of these adjustments is as a side effect of a measure change, as proposed by Pelsser (2003...

  3. Undergraduate Convexity

    DEFF Research Database (Denmark)

    Lauritzen, Niels

    -Motzkin elimination, the theory is developed by introducing polyhedra, the double description method and the simplex algorithm, closed convex subsets, convex functions of one and several variables ending with a chapter on convex optimization with the Karush-Kuhn-Tucker conditions, duality and an interior point...

  4. Linear array transducer for high-power airborne ultrasound using flextensional structure

    Science.gov (United States)

    Yamamoto, Jun; Mizuno, Yosuke; Tabaru, Marie; Nakamura, Kentaro

    2015-07-01

    To change the direction of ultrasonic irradiation without moving a transducer, a high-power airborne ultrasonic transducer for a one-dimensional phased array system was designed and tested. A flextensional element transducer with higher-mode bending vibration was fabricated to obtain a high vibration amplitude over a wide aperture, where a phase-compensating stepped structure was employed. The width of the main lobe at half maximum and the sidelobe level were measured to be 14.3 deg and 0.78, respectively. The maximal sound pressure of 132 dB (0 dB re. 0.02 mPa) was obtained under the applied voltage of 4.0 V. The beam steering characteristics of a phased array using eight elements were compared with the simple theory.

  5. Prostate Ultrasound

    Medline Plus

    Full Text Available ... chest. To obtain high-quality images, an ultrasound transducer – a plastic cylinder about the size of a ... or sonography , involves the use of a small transducer (probe) and ultrasound gel placed directly on the ...

  6. Ultrasound pulse-echo measurements on rough surfaces with linear array transducers

    DEFF Research Database (Denmark)

    Sjøj, Sidsel M. N.; Blanco, Esther N.; Wilhjelm, Jens E.

    2012-01-01

    The echo from planar surfaces with rms roughness, Rq, in the range from 0-155 μm was measured with a clinical linear array transducer at different angles of incidence at 6 MHz and 12 MHz. The echo-pulse from the surfaces was isolated with an equal sized window and the power of the echo-pulse was ...

  7. Design of a Broadband Electrical Impedance Matching Network for Piezoelectric Ultrasound Transducers Based on a Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Jianfei An

    2014-04-01

    Full Text Available An improved method based on a genetic algorithm (GA is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network and perform optimization on the components. The main idea of this method is to find the optimal matching network in a set of candidate topologies. Some successful experiences of classical algorithms are absorbed to limit the size of the set of candidate topologies and greatly simplify the calculation process. Both binary-coded GA and real-coded GA are used for topology optimization and components optimization, respectively. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted to make sure that the algorithm can converge to the global optimal result. Simulation and experimental results prove that matching networks with better performance might be achieved by this improved method.

  8. Design of a broadband electrical impedance matching network for piezoelectric ultrasound transducers based on a genetic algorithm.

    Science.gov (United States)

    An, Jianfei; Song, Kezhu; Zhang, Shuangxi; Yang, Junfeng; Cao, Ping

    2014-04-16

    An improved method based on a genetic algorithm (GA) is developed to design a broadband electrical impedance matching network for piezoelectric ultrasound transducer. A key feature of the new method is that it can optimize both the topology of the matching network and perform optimization on the components. The main idea of this method is to find the optimal matching network in a set of candidate topologies. Some successful experiences of classical algorithms are absorbed to limit the size of the set of candidate topologies and greatly simplify the calculation process. Both binary-coded GA and real-coded GA are used for topology optimization and components optimization, respectively. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted to make sure that the algorithm can converge to the global optimal result. Simulation and experimental results prove that matching networks with better performance might be achieved by this improved method.

  9. Photoacoustic imaging of early gastric cancer diagnosis based on long focal area ultrasound transducer

    Science.gov (United States)

    Wu, Huaqin; Li, Zuoran; Liu, Lantian; Li, Zhifang; Wu, Shulian; Li, Hui

    2017-06-01

    We illustrated a novel imaging method to diagnose gastric neoplasms via photoacoustic tomography (PAT). Depending on the structural characteristics of gastric cavity, we used column diffusion fiber to irradiate the stomach tissue through the esophagus, and the externally placed telecentric focus ultrasonic transducer detected photoacoustic signals from the gastric tissue. We reconstructed the distribution of light energy deposition of the simulated gastric tumor, and obtained the location and size information of gastric tumor.

  10. Use of nakagami statistics and empirical mode decomposition for ultrasound tissue characterization by a nonfocused transducer.

    Science.gov (United States)

    Tsui, Po-Hsiang; Chang, Chien-Cheng; Ho, Ming-Chih; Lee, Yu-Hsin; Chen, Yung-Sheng; Chang, Chien-Chung; Huang, Norden E; Wu, Zhao-Hua; Chang, King-Jen

    2009-12-01

    The Nakagami parameter associated with the Nakagami distribution estimated from ultrasonic backscattered signals reflects the scatterer concentration in a tissue. A nonfocused transducer does not allow tissue characterization based on the Nakagami parameter. This paper proposes a new method called the noise-assisted Nakagami parameter based on empirical mode decomposition of noisy backscattered echoes to allow quantification of the scatterer concentration based on data obtained using a nonfocused transducer. To explore the practical feasibility of the proposed method, the current study performed experiments on phantoms and measurements on rat livers in vitro with and without fibrosis induction. The results show that using a nonfocused transducer makes it possible to use the noise-assisted Nakagami parameter to classify phantoms with different scatterer concentrations and different stages of liver fibrosis in rats more accurately than when using techniques based on the echo intensity and the conventional Nakagami parameter. However, the conventional Nakagami parameter and the noise-assisted Nakagami parameter have different meanings: the former represents the statistics of signals backscattered from unresolvable scatterers, whereas the latter is associated with stronger resolvable scatterers or local inhomogeneity caused by scatterer aggregation.

  11. Progress in developing a thermal method for measuring the output power of medical ultrasound transducers that exploits the pyroelectric effect.

    Science.gov (United States)

    Zeqiri, Bajram; Zauhar, Gordana; Hodnett, Mark; Barrie, Jill

    2011-05-01

    Progress in developing a new measurement method for ultrasound output power is described. It is a thermal-based technique with the acoustic power generated by a transducer being absorbed within a specially developed polyurethane rubber material, whose high absorption coefficient ensures energy deposition within a few mm of the ultrasonic wave entering the material. The rate of change of temperature at the absorber surface is monitored using the pyroelectric voltage generated from electrodes disposed either side of a 60 mm diameter, 0.061 mm thick membrane of the piezoelectric polymer polyvinylidene fluoride (pvdf) bonded to the absorber. The change in the pyroelectric output voltage generated by the sensor when the transducer is switched ON and OFF is proportional to the delivered ultrasound power. The sensitivity of the device is defined as the magnitude of these switch voltages to a unit input stimulus of power (watt). Three important aspects of the performance of the pyroelectric sensor have been studied. Firstly, measurements have revealed that the temperature dependent sensitivity increases over the range from approximately 20°C to 30°C at a rate of +1.6% °C(-1). Studies point to the key role that the properties of both the absorbing backing layer and pvdf membrane play in controlling the sensor response. Secondly, the high sensitivity of the technique has been demonstrated using an NPL Pulsed Checksource, a 3.5 MHz focused transducer delivering a nominal acoustic power level of 4 mW. Finally, proof-of-concept of a new type of acoustic sensor responding to time-averaged intensity has been demonstrated, through fabrication of an absorber-backed hydrophone of nominal active element diameter 0.4 mm. A preliminary study using such a device to resolve the spatial distribution of acoustic intensity within plane-piston and focused 3.5 MHz acoustic fields has been completed. Derived beam profiles are compared to conventional techniques that depend on deriving

  12. First in vivo use of a capacitive micromachined ultrasound transducer array-based imaging and ablation catheter.

    Science.gov (United States)

    Stephens, Douglas N; Truong, Uyen T; Nikoozadeh, Amin; Oralkan, Omer; Seo, Chi Hyung; Cannata, Jonathan; Dentinger, Aaron; Thomenius, Kai; de la Rama, Alan; Nguyen, Tho; Lin, Feng; Khuri-Yakub, Pierre; Mahajan, Aman; Shivkumar, Kalyanam; O'Donnell, Matt; Sahn, David J

    2012-02-01

    The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML-CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)-derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures. The new 9F forward-looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed. The ML-CMUT ICE catheter provided high-resolution real-time wideband 2-dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24-element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound-compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first-order correlation between TSI and temperature, permitting early development temperature-time relationships at specific myocardial ablation sites. Multifunctional forward-looking ML-CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures.

  13. First In Vivo Use of a Capacitive Micromachined Ultrasound Transducer Array–Based Imaging and Ablation Catheter

    Science.gov (United States)

    Stephens, Douglas N.; Truong, Uyen T.; Nikoozadeh, Amin; Oralkan, Ömer; Seo, Chi Hyung; Cannata, Jonathan; Dentinger, Aaron; Thomenius, Kai; de la Rama, Alan; Nguyen, Tho; Lin, Feng; Khuri-Yakub, Pierre; Mahajan, Aman; Shivkumar, Kalyanam; O’Donnell, Matt; Sahn, David J.

    2012-01-01

    Objectives The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML-CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)-derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures. Methods The new 9F forward-looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed. Results The ML-CMUT ICE catheter provided high-resolution real-time wideband 2-dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24-element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound-compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first-order correlation between TSI and temperature, permitting early development temperature-time relationships at specific myocardial ablation sites. Conclusions Multifunctional forward-looking ML-CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures. PMID:22298868

  14. Heart ablation using a planar rectangular high intensity focused ultrasound transducer and MRI guidance

    Science.gov (United States)

    Couppis, Andreas; Damianou, Christakis; Ioannides, Kleanthis; Mylonas, Nicos; Iosif, Demitris; Kyriakou, Panagiotis; Lafon, Cyril; Chavrier, Francoise; Chapelon, Jean-Yves; Birer, Alain

    2011-09-01

    The aim of this study was to evaluate the performance of a flat rectangular (3×10 mm2) MRI compatible transducer operating at 5 MHz in creating deep lesions in heart at a depth of at least 15 mm. The size of thermal necrosis in heart tissue was estimated as a function of power and time using a simulation model. The system was then tested in freshly excised heart of pig and lamb. In this study we were able to create lesions 15 mm deep with an acoustic power of 6W for an exposure of approximately one minute. The contrast to noise ratio (CNR) between lesion and heart tissue was evaluated using Fast Spin Echo (FSE). With T1W FSE the CNR value was approximately 22. Maximum CNR was achieved with repetition times (TR) between 300 and 800 ms. With T2W FSE the corresponding CNR was approximately 13. The transducer was tested in rabbits in vivo and despite the motion of the heart; it was possible to create thermal lesions.

  15. Prostate Ultrasound

    Medline Plus

    Full Text Available ... are the limitations of Prostate Ultrasound Imaging? What is Ultrasound Imaging of the Prostate? Ultrasound is safe ... transducer into the body. top of page How is the procedure performed? In men, the prostate gland ...

  16. Local piezoelectric behavior in PZT-based thin films for ultrasound transducers

    Science.gov (United States)

    Griggio, Flavio

    Piezoelectric microelectromechanical systems (MEMS) are currently used in inkjet printers and precision resonators; numerous additional applications are being investigated for sensors, low-voltage actuators, and transducers. This work was aimed at improving piezoelectric MEMS by taking two approaches: 1) identifying factors affecting the piezoelectric response of ferroelectric thin films and 2) demonstrating integration of these films into a high frequency array transducer. It was found that there are several key factors influencing the piezoelectric response of thin films for a given material composition. First, large grain size improves the piezoelectric response. This was demonstrated using chemical solution deposited lead nickel niobate -- lead zirconate titanate (0.3)Pb(Ni 0.33Nb0.67)O3 - (0.7)Pb(Zr0.45Ti 0.55O3), (PNN-PZT) ferroelectric thin films. It was shown that this composition allows greater microstructural control than does PZT. Dielectric permittivities ranging from 1350 to 1520 and a transverse piezoelectric coefficient e31,f as high as -- 9.7 C/m 2 were observed for films of about 0.25 mum in thickness. The permittivity and piezoelectric response as well as extrinsic contributions to the dielectric constant increased by 14 and 12 % respectively for samples with grain sizes ranging from 110 to 270 nm. A second factor influencing the piezoelectric response is film composition with respect to the morphotropic phase boundary (MPB). The composition dependence of the dielectric and piezoelectric nonlinearities was characterized in epitaxially grown (0.3)Pb(Ni0.33Nb0.67)O3-(0.7)Pb(Zr xTi1-xO3) thin films deposited on SrTiO 3 to minimize the influence of large-angle grain boundaries. Tetragonal, MPB and rhombohedral films were prepared by changing the Zr/Ti ratio. The largest dielectric and piezoelectric nonlinearities were observed for the rhombohedral sample; this resulted from a higher domain wall mobility due to a smaller ferroelectric distortion and

  17. A laser ultrasound transducer using carbon nanofibers–polydimethylsiloxane composite thin film

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Bao-Yu; Kim, Jinwook; Li, Sibo; Jiang, Xiaoning, E-mail: xjiang5@ncsu.edu [Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Zhu, Jiadeng; Zhang, Xiangwu [Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-01-12

    The photoacoustic effect has been broadly applied to generate high frequency and broadband acoustic waves using lasers. However, the efficient conversion from laser energy to acoustic power is required to generate acoustic waves with high intensity acoustic pressure (>10 MPa). In this study, we demonstrated laser generated high intensity acoustic waves using carbon nanofibers–polydimethylsiloxane (CNFs-PDMS) thin films. The average diameter of the CNFs is 132.7 ± 11.2 nm. The thickness of the CNFs film and the CNFs-PDMS composite film is 24.4 ± 1.43 μm and 57.9 ± 2.80 μm, respectively. The maximum acoustic pressure is 12.15 ± 1.35 MPa using a 4.2 mJ, 532 nm Nd:YAG pulsed laser. The maximum acoustic pressure using the CNFs-PDMS composite was found to be 7.6-fold (17.62 dB) higher than using carbon black PDMS films. Furthermore, the calculated optoacoustic energy conversion efficiency K of the prepared CNFs-PDMS composite thin films is 15.6 × 10{sup −3 }Pa/(W/m{sup 2}), which is significantly higher than carbon black-PDMS thin films and other reported carbon nanomaterials, carbon nanostructures, and metal thin films. The demonstrated laser generated high intensity ultrasound source can be useful in ultrasound imaging and therapy.

  18. Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor.

    Science.gov (United States)

    Zhou, Yufeng

    2015-03-01

    The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

  19. Prostate Ultrasound

    Medline Plus

    Full Text Available ... use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds ...

  20. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds ...

  1. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... or sonography , involves the use of a small transducer (probe) and ultrasound gel placed directly on the ... probe through the gel into the body. The transducer collects the sounds that bounce back and a ...

  2. Design and fabrication of a low-frequency (1-3 MHz) ultrasound transducer for accurate placement of screw implants in the spine

    Science.gov (United States)

    Manbachi, Amir; Lee, Mike; Foster, F. Stuart; Ginsberg, Howard J.; Cobbold, Richard S. C.

    2014-03-01

    In 2012 approximately 800,000 spinal fusion surgeries were performed in the United States, requiring the insertion of screws into the pedicles. Their exact placement is critical and made complex due to limited visibility of the spine, continuous bleeding in the exposed regions, and variability in morphologies. The alarmingly high rate of screw misplacements (up to 20%) reported in the literature is of major concern since such misplacements can place the surrounding vital structures at risk. A potential guidance method for determining the best screw trajectory is by the use of real-time ultrasound imaging similar to that used for intravascular imaging. An endovascular transducer could be inserted into the pedicle to image the anatomy from within and identify bone boundaries. A major challenge of imaging within bone is high signal attenuation. The rapid increase of attenuation with frequency requires much lower frequencies (1-3 MHz) than those used in intravascular imaging. This study describes the custom design and fabrication of 2 MHz ultrasound probes (3.5 mm diameter/ 11 Fr) for pedicle screw guidance. Three transducer designs are explored to provide improved sensitivity and signal to noise ratio, compared to the previously tested transducer within the pedicle. Experimental measurements are compared with the results obtained using various simulation tools. The work reported in this paper represents the first stage in our ultimate goal of developing a 32- element phased array that is capable of generating a radial B-mode image.

  3. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... transducer into the body. Doppler ultrasound, a special application of ultrasound, measures the direction and speed of ... understanding of the possible charges you will incur. Web page review process: This Web page is reviewed ...

  4. Ultrasound -- Pelvis

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    Full Text Available ... 3-D ultrasound or sonohysterography for patients with infertility. In this setting, three-dimensional ultrasound provides information ... the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves ...

  5. Prostate Ultrasound

    Medline Plus

    Full Text Available ... of page What will I experience during and after the procedure? Ultrasound exams in which the transducer ... a regular ultrasound imaging probe on the perineal skin of the patient, between the legs and behind ...

  6. Cubes convexes

    CERN Document Server

    Nedjar, Sebastien; Cicchetti, Rosine; Lakhal, Lotfi; 10.3166/isi.11.6.11-31

    2010-01-01

    In various approaches, data cubes are pre-computed in order to answer efficiently OLAP queries. The notion of data cube has been declined in various ways: iceberg cubes, range cubes or differential cubes. In this paper, we introduce the concept of convex cube which captures all the tuples of a datacube satisfying a constraint combination. It can be represented in a very compact way in order to optimize both computation time and required storage space. The convex cube is not an additional structure appended to the list of cube variants but we propose it as a unifying structure that we use to characterize, in a simple, sound and homogeneous way, the other quoted types of cubes. Finally, we introduce the concept of emerging cube which captures the significant trend inversions. characterizations.

  7. Piezoelectric Composite Micromachined Multifrequency Transducers for High-Resolution, High-Contrast Ultrasound Imaging for Improved Prostate Cancer Assessment

    Science.gov (United States)

    2016-10-01

    MHz) transducer was developed for demonstrating the feasibility of transrectal acoustic angiography. This was the first dual mode 3/15 MHz array... acoustic angiography imaging in intracavity applications. A single element dual-frequency IVUS transducer was developed for concept validation, which...the backside of the transmitter is close to the free boundary, which cannot absorb backward travelling waves, the low acoustic impedance (19.8 MRayl

  8. The Role of Convex Probe Endobronchial Ultrasound Guided Transbronchial Needle Aspiration in the Diagnosis of Malignant Mediastinal and Hilar Lymph Nodes

    Directory of Open Access Journals (Sweden)

    Benan Caglayan

    2012-01-01

    Full Text Available Background: In the diagnosis of malignant lymph nodes (LNs and staging of lung cancer, sampling of mediastinal and hilar LNs is essential. Mediastinoscopy is known as the gold standard. Convex probe (CP endobronchial ultrasound (EBUS-guided transbronchial needle aspiration (TBNA is a noninvasive and highly sensitive diagnostic method in mediastinal and hilar LN sampling.Objectives: Evaluating the role of CP-EBUS-guided TBNA in the diagnosis of mediastinal and hilar LNs suspicious of malignancy.Patients and Methods: One hundred twenty patients with a known lung malignancy or hilar/mediastinal LNs detected by thoracic computed tomography (CT and/or positron emission tomography (PET-CT suspicious for malignancy were included in this prospective study. The procedure was performed by Olympus 7.5 MHz CP endoscope and EU C2000 processor by the oral route under topical anesthesia and conscious sedation. After visualization of LNs, their dimensions were recorded. Aspiration was considered as “insufficient” if there were inadequate lymphocytes on the smears. Diagnosis of “malignancy” on cytologic examination was considered as the “final diagnosis”. If diagnosis was negative for malignancy, more invasive procedures were performed to confirm the diagnosis.Results: Twenty four females and 96 male patients (mean age, 57.8 ± 9.1 were included. A total of 177 LN stations were aspirated in 120 patients. In 82 patients, the diagnosis was malignant by EBUS-guided TBNA and in the remaining 38; the diagnosis was established by further invasive procedures. Of the 38 EBUS-guided TBNA negative patients, 28 were diagnosed as non-malignant and 10 were malignant. The sensitivity, diagnostic accuracy and negative predictive value of CP EBUS-guided TBNA were 89.1%, 91.6% and 73.6%, respectively. No major complications were seen.Conclusion: As an alternative method to mediastinoscopy, EBUS-guided TBNA is a safe and noninvasive procedure with high sensitivity in

  9. Convex polytopes

    CERN Document Server

    Klee, Victor; Ziegler, Günter

    2003-01-01

    "The appearance of Grünbaum's book Convex Polytopes in 1967 was a moment of grace to geometers and combinatorialists. The special spirit of the book is very much alive even in those chapters where the book's immense influence made them quickly obsolete. Some other chapters promise beautiful unexplored land for future research. The appearance of the new edition is going to be another moment of grace. Kaibel, Klee and Ziegler were able to update the convex polytope saga in a clear, accurate, lively, and inspired way." (Gil Kalai, The Hebrew University of Jerusalem) "The original book of Grünbaum has provided the central reference for work in this active area of mathematics for the past 35 years...I first consulted this book as a graduate student in 1967; yet, even today, I am surprised again and again by what I find there. It is an amazingly complete reference for work on this subject up to that time and continues to be a major influence on research to this day." (Louis J. Billera, Cornell University) "The or...

  10. Ultrasound

    Science.gov (United States)

    Ultrasound is a type of imaging. It uses high-frequency sound waves to look at organs and ... liver, and other organs. During pregnancy, doctors use ultrasound to view the fetus. Unlike x-rays, ultrasound ...

  11. Imaging of implant needles for real-time HDR-brachytherapy prostate treatment using biplane ultrasound transducers.

    Science.gov (United States)

    Siebert, Frank-André; Hirt, Markus; Niehoff, Peter; Kovács, György

    2009-08-01

    Ultrasound imaging is becoming increasingly important in prostate brachytherapy. In high-dose-rate (HDR) real-time planning procedures the definition of the implant needles is often performed by transrectal ultrasound. This article describes absolute measurements of the visibility and accuracy of manual detection of implant needle tips and compares measurement results of different biplane ultrasound systems in transversal and longitudinal (i.e., sagittal) ultrasound modes. To obtain a fixed coordinate system and stable conditions the measurements were carried out in a water tank using a dedicated marker system. Needles were manually placed in the phantom until the observer decided by the real-time ultrasound image that the zero position was reached. A comparison of three different ultrasound systems yielded an offset between 0.8 and 3.1 mm for manual detection of the needle tip in ultrasound images by one observer. The direction of the offset was discovered to be in the proximal direction, i.e., the actual needle position was located more distally compared to the ultrasound-based definition. In the second part of the study, the ultrasound anisotropy of trocar implant needles is reported. It was shown that the integrated optical density in a region of interest around the needle tip changes with needle rotation. Three peaks were observed with a phase angle of 120 degrees. Peaks appear not only in transversal but also in longitudinal ultrasound images, with a phase shift of 60 degrees. The third section of this study shows results of observer dependent influences on needle tip detection in sagittal ultrasound images considering needle rotation. These experiments were carried out using the marker system in a water tank. The needle tip was placed exactly at the position z=0 mm. It was found that different users tend to differently interpret the same ultrasound images. The needle tip was manually detected five times in the ultrasound images by three experienced observers

  12. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... of page How is the procedure performed? For most ultrasound exams, you will be positioned lying face- ... Ultrasound examinations are painless and easily tolerated by most patients. Ultrasound exams in which the transducer is ...

  13. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... data into 3-D images. A Doppler ultrasound study may be part of an ultrasound examination. Doppler ... usually stain or discolor clothing. In some ultrasound studies, the transducer is attached to a probe and ...

  14. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... ultrasound. top of page How does the procedure work? Ultrasound imaging is based on the same principles ... not stain or discolor clothing. In some ultrasound studies, the transducer is attached to a probe and ...

  15. 3-D Ultrasound Imaging Performance of a Row-Column Addressed 2-D Array Transducer: A Measurement Study

    DEFF Research Database (Denmark)

    Rasmussen, Morten Fischer; Jensen, Jørgen Arendt

    2013-01-01

    A real-time 3-D ultrasound measurement using only 32 elements and 32 emissions is presented. The imaging quality is compared to a conventionally fully addressed array using 1024 elements and 256 emissions. The main-lobe of the measured line spread function is almost identical, but the side-lobe l...... ultrasound probe made by Vermon S.A....... is 510% larger than when row-column addressing the array. The cyst radius needed to achieve -20 dB intensity in the cyst is 396% larger for the fully addressed array compared to the row-column addressed array. The measurements were made using the experimental ultrasound scanner SARUS and a 32x32 element...

  16. Piezoelectric Composite Micromachined Multifrequency Transducers for High-Resolution, High-Contrast Ultrasound Imaging for Improved Prostate Cancer Assessment

    Science.gov (United States)

    2014-08-01

    Industries Inc., Rochester, NY). The hydrophone was moved laterally and axially and the measured pressure values were processed to obtain the pressure...transmission condition was same as pressure mapping condition (2 MHz, cycles, 300 mVpp, and 55dB gain). The cellulose tube was filled with water, air, and...bubbles & water) Outlet Function generator Power amplifier Computer/LabVIEW Transducer Cellulose tubeWater tank z y x Figure 18. Bubble signal

  17. On Convex Quadratic Approximation

    NARCIS (Netherlands)

    den Hertog, D.; de Klerk, E.; Roos, J.

    2000-01-01

    In this paper we prove the counterintuitive result that the quadratic least squares approximation of a multivariate convex function in a finite set of points is not necessarily convex, even though it is convex for a univariate convex function. This result has many consequences both for the field of

  18. On Convex Quadratic Approximation

    NARCIS (Netherlands)

    den Hertog, D.; de Klerk, E.; Roos, J.

    2000-01-01

    In this paper we prove the counterintuitive result that the quadratic least squares approximation of a multivariate convex function in a finite set of points is not necessarily convex, even though it is convex for a univariate convex function. This result has many consequences both for the field of

  19. Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

    Energy Technology Data Exchange (ETDEWEB)

    Mehrmohammadi, Mohammad; Kinnick, Randall R.; Fatemi, Mostafa, E-mail: fatemi.mostafa@mayo.edu [Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 (United States); Alizad, Azra [Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 and Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905 (United States); Davis, Brian J. [Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905 (United States)

    2014-09-15

    Purpose: Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens. Methods: Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped with a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection. Results: The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%–92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment. Conclusions: Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that

  20. Three-dimensional electrode displacement elastography using the Siemens C7F2 fourSight four-dimensional ultrasound transducer.

    Science.gov (United States)

    Bharat, Shyam; Fisher, Ted G; Varghese, Tomy; Hall, Timothy J; Jiang, Jingfeng; Madsen, Ernest L; Zagzebski, James A; Lee, Fred T

    2008-08-01

    Because ablation therapy alters the elastic modulus of tissues, emerging strain imaging methods may enable clinicians for the first time to have readily available, cost-effective, real-time guidance to identify the location and boundaries of thermal lesions. Electrode displacement elastography is a method of strain imaging tailored specifically to ultrasound-guided electrode-based ablative therapies (e.g., radio-frequency ablation). Here tissue deformation is achieved by applying minute perturbations to the unconstrained end of the treatment electrode, resulting in localized motion around the end of the electrode embedded in tissue. In this article, we present a method for three-dimensional (3D) elastographic reconstruction from volumetric data acquired using the C7F2 fourSight four-dimensional ultrasound transducer, provided by Siemens Medical Solutions USA, Inc. (Issaquah, WA, USA). Lesion reconstruction is demonstrated for a spherical inclusion centered in a tissue-mimicking phantom, which simulates a thermal lesion embedded in a normal tissue background. Elastographic reconstruction is also performed for a thermal lesion created in vitro in canine liver using radio-frequency ablation. Postprocessing is done on the acquired raw radio-frequency data to form surface-rendered 3D elastograms of the inclusion. Elastographic volume estimates of the inclusion compare reasonably well with the actual known inclusion volume, with 3D electrode displacement elastography slightly underestimating the true inclusion volume.

  1. Piezoelectric Composite Micromachined Multifrequency Transducers for High-Resolution, High-Contrast Ultrasound Imaging for Improved Prostate Cancer Assessment

    Science.gov (United States)

    2015-08-01

    Medical Research and Materiel Command Fort Detrick, Maryland 21702-5012 DISTRIBUTION STATEMENT: Approved for Public Release; Distribution Unlimited...SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) U.S. Army Medical Research and Materiel Command Fort Detrick...a Siemens EV- 8C4 transrectal ultrasound probe. In the in-vivo study, molecular imaging and microvascular mapping will both be performed to assess

  2. Systematic evaluation of a secondary method for measuring diagnostic-level medical ultrasound transducer output power based on a large-area pyroelectric sensor

    Science.gov (United States)

    Zeqiri, B.; Žauhar, G.; Rajagopal, S.; Pounder, A.

    2012-06-01

    A systematic study of the application of a novel pyroelectric technique to the measurement of diagnostic-level medical ultrasound output power is described. The method exploits the pyroelectric properties of a 0.028 mm thick membrane of polyvinylidene fluoride (PVDF), backed by an acoustic absorber whose ultrasonic absorption coefficient approaches 1000 dB cm-1 at 3 MHz. When exposed to an ultrasonic field, absorption of ultrasound adjacent to the PVDF-absorber interface results in heating and the generation of a pyroelectric output voltage across gold electrodes deposited on the membrane. For a sensor large enough to intercept the whole of the acoustic beam, the output voltage can be calibrated for the measurement of acoustic output power. A number of key performance properties of the method have been investigated. The technique is very sensitive, with a power to voltage conversion factor of typically 0.23 V W-1. The frequency response of a particular embodiment of the sensor in which acoustic power reflected at the absorber-PVDF interface is subsequently returned to the pyroelectric membrane to be absorbed, has been evaluated over the frequency range 1.5 MHz to 10 MHz. This has shown the frequency response to be flat to within ±4%, above 2.5 MHz. Below this frequency, the sensitivity falls by 20% at 1.5 MHz. Linearity of the technique has been demonstrated to within ±1.6% for applied acoustic power levels from 1 mW up to 120 mW. A number of other studies targeted at assessing the achievable measurement uncertainties are presented. These involve: the effects of soaking, the influence of the angle of incidence of the acoustic beam, measurement repeatability and sensitivity to transducer positioning. Additionally, over the range 20 °C to 30 °C, the rate of change in sensitivity with ambient temperature has been shown to be +0.5% °C-1. Implications of the work for the development of a sensitive, traceable, portable, secondary method of ultrasound output power

  3. Uniformly convex and strictly convex Orlicz spaces

    Science.gov (United States)

    Masta, Al Azhary

    2016-02-01

    In this paper we define the new norm of Orlicz spaces on ℝn through a multiplication operator on an old Orlicz spaces. We obtain some necessary and sufficient conditions that the new norm to be a uniformly convex and strictly convex spaces.

  4. Prostate Ultrasound

    Medline Plus

    Full Text Available ... physician during a routine physical exam or prostate cancer screening exam. an elevated blood test result. difficulty ... vessels or to detect abnormal masses, such as tumors. In an ultrasound examination, a transducer both sends ...

  5. Prostate Ultrasound

    Science.gov (United States)

    ... prostate. help diagnose the cause of a man's infertility. A transrectal ultrasound of the prostate gland is ... the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves ...

  6. Prostate Ultrasound

    Medline Plus

    Full Text Available ... prostate. help diagnose the cause of a man's infertility. A transrectal ultrasound of the prostate gland is ... the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves ...

  7. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... areas of the body while other areas, especially air-filled lungs, are poorly suited for ultrasound. For ... make secure contact with the body and eliminate air pockets between the transducer and the skin that ...

  8. Prostate Ultrasound

    Medline Plus

    Full Text Available ... an ultrasound transducer – a plastic cylinder about the size of a finger – is inserted short distance into ... the object is as well as the object's size, shape and consistency (whether the object is solid ...

  9. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the ... the transducer (the device placed on the patient's skin to send and receive the returning sound waves), ...

  10. Prostate Ultrasound

    Medline Plus

    Full Text Available ... probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the ... the transducer (the device placed on the patient's skin to send and receive the returning sound waves), ...

  11. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... extract a sample of cells from organs for laboratory testing. Doppler ultrasound images can help the physician ... The transducer sends out inaudible, high—frequency sound waves into the body and then listens for the ...

  12. Ultrasound presentation of abdominal non-Hodgkin lymphomas in pediatric patients.

    Science.gov (United States)

    Brodzisz, Agnieszka; Woźniak, Magdalena Maria; Dudkiewicz, Ewa; Grabowski, Dominik; Stefaniak, Jolanta; Wieczorek, Andrzej Paweł; Kowalczyk, Jerzy

    2013-12-01

    Burkitt's lymphoma accounts for approximately 25% of lymphomas diagnosed in children of developmental age. The tumor is localized mainly in the intestine (usually in the ileocecal region), mesenteric lymph nodes and extraperitoneal space. The clinical symptoms are non-specific and include: abdominal pain, vomiting, gastrointestinal bleeding, and acute abdomen suggesting appendicitis or intestinal intussusception. On ultrasound examination, Burkitt's lymphoma may manifest itself in various ways, depending on the origin of the lesion. The aim of this paper was to review the ultrasound manifestation of abdominal Burkitt's lymphoma in children. The analysis included 15 pediatric patients with Burkitt's non-Hodgkin lymphoma in the abdominal cavity. The mean age of the patients was 9.5. Abdominal and gastrointestinal ultrasound examinations were conducted using a Siemens scanner with a convex transducer of 3.5-5 MHz and linear array transducer of L4 - 7.5 MHz. Ultrasound examinations conducted in the group of 15 patients revealed pathological masses localized in the gastric wall in 3 patients (20%), in the ileocecal region in 10 patients (67%) and a disseminated process in 2 patients (13%). In 12 patients with a diagnosed Burkitt's non-Hodgkin lymphoma in an extragastric localization, differences in the morphology of the lesions were observed. The clinical and ultrasound picture of abdominal Burkitt's lymphoma in children is variable. A careful ultrasound assessment of all abdominal organs conducted with the use of convex and linear probes increases the chances of establishing an adequate diagnosis.

  13. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers

    Science.gov (United States)

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-01

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  14. Real-time monitoring of focused ultrasound blood-brain barrier opening via subharmonic acoustic emission detection: implementation of confocal dual-frequency piezoelectric transducers.

    Science.gov (United States)

    Tsai, Chih-Hung; Zhang, Jia-Wei; Liao, Yi-Yi; Liu, Hao-Li

    2016-04-07

    Burst-tone focused ultrasound exposure in the presence of microbubbles has been demonstrated to be effective at inducing temporal and local opening of the blood-brain barrier (BBB), which promises significant clinical potential to deliver therapeutic molecules into the central nervous system (CNS). Traditional contrast-enhanced imaging confirmation after focused ultrasound (FUS) exposure serves as a post-operative indicator of the effectiveness of FUS-BBB opening, however, an indicator that can concurrently report the BBB status and BBB-opening effectiveness is required to provide effective feedback to implement this treatment clinically. In this study, we demonstrate the use of subharmonic acoustic emission detection with implementation on a confocal dual-frequency piezoelectric ceramic structure to perform real-time monitoring of FUS-BBB opening. A confocal dual-frequency (0.55 MHz/1.1 MHz) focused ultrasound transducer was designed. The 1.1 MHz spherically-curved ceramic was employed to deliver FUS exposure to induce BBB-opening, whereas the outer-ring 0.55 MHz ceramic was employed to detect the subharmonic acoustic emissions originating from the target position. In stage-1 experiments, we employed spectral analysis and performed an energy spectrum density (ESD) calculation. An optimized 0.55 MHz ESD level change was shown to effectively discriminate the occurrence of BBB-opening. Wideband acoustic emissions received from 0.55 MHz ceramics were also analyzed to evaluate its correlations with erythrocyte extravasations. In stage-2 real-time monitoring experiments, we applied the predetermined ESD change as a detection threshold in PC-controlled algorithm to predict the FUS exposure intra-operatively. In stage-1 experiment, we showed that subharmonic ESD presents distinguishable dynamics between intact BBB and opened BBB, and therefore a threshold ESD change level (5.5 dB) can be identified for BBB-opening prediction. Using this ESD change threshold detection as a

  15. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds ...

  16. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... or sonography , involves the use of a small transducer (probe) and ultrasound gel placed directly on the ... probe through the gel into the body. The transducer collects the sounds that bounce back and a ...

  17. Micromachined Ultrasonic Transducers for 3-D Imaging

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lehrmann

    such transducer arrays, capacitive micromachined ultrasonic transducer (CMUT) technology is chosen for this project. Properties such as high bandwidth and high design flexibility makes this an attractive transducer technology, which is under continuous development in the research community. A theoretical...... of state-of-the-art 3-D ultrasound systems. The focus is on row-column addressed transducer arrays. This previously sparsely investigated addressing scheme offers a highly reduced number of transducer elements, resulting in reduced transducer manufacturing costs and data processing. To produce......Real-time ultrasound imaging is a widely used technique in medical diagnostics. Recently, ultrasound systems offering real-time imaging in 3-D has emerged. However, the high complexity of the transducer probes and the considerable increase in data to be processed compared to conventional 2-D...

  18. Curved PVDF airborne transducer.

    Science.gov (United States)

    Wang, H; Toda, M

    1999-01-01

    In the application of airborne ultrasonic ranging measurement, a partially cylindrical (curved) PVDF transducer can effectively couple ultrasound into the air and generate strong sound pressure. Because of its geometrical features, the ultrasound beam angles of a curved PVDF transducer can be unsymmetrical (i.e., broad horizontally and narrow vertically). This feature is desired in some applications. In this work, a curved PVDF air transducer is investigated both theoretically and experimentally. Two resonances were observed in this transducer. They are length extensional mode and flexural bending mode. Surface vibration profiles of these two modes were measured by a laser vibrometer. It was found from the experiment that the surface vibration was not uniform along the curvature direction for both vibration modes. Theoretical calculations based on a model developed in this work confirmed the experimental results. Two displacement peaks were found in the piezoelectric active direction of PVDF film for the length extensional mode; three peaks were found for the flexural bending mode. The observed peak positions were in good agreement with the calculation results. Transient surface displacement measurements revealed that vibration peaks were in phase for the length extensional mode and out of phase for the flexural bending mode. Therefore, the length extensional mode can generate a stronger ultrasound wave than the flexural bending mode. The resonance frequencies and vibration amplitudes of the two modes strongly depend on the structure parameters as well as the material properties. For the transducer design, the theoretical model developed in this work can be used to optimize the ultrasound performance.

  19. Current Research Situation of High-intensity Focused Ultrasound Transducer for Oncotherapy%肿瘤治疗用高强度聚焦超声换能器的研究现状

    Institute of Scientific and Technical Information of China (English)

    刘刚; 尹军刚

    2012-01-01

    高强度聚集超声(High-intensity Focused Ultrasound,HIFU)作为一种非侵入性、无毒副作用、具有巨大潜力的肿瘤治疗手段,近年来已经越来越受到国内外学者的广泛关注.高强度聚焦超声换能器是HIFU肿瘤治疗设备的核心部件,直接影响治疗的效果.因此,本文就其发展过程、治疗机制及应用等相关问题做一综述.%As non-invasive technique with non-toxic side effects and great potential, high-intensity focused ultrasound(HIFU) has received widespread attention from scholars both at home and abroad in recent years. Higb- intensity focused ultrasound transducer is the core component of HIFU treatment equipment for oncotherapy, which chould affect the therapeutical result directly. Therefore, this paper summarizes some related issues of high-intensity focused ultrasound transducer, including its development, working principle, applications and so on.

  20. Ultrasound

    Science.gov (United States)

    ... Saunders; 2014:chap 66. Cosgrove DO, Eckersley RJ, Harvey CJ, Lim A. Ultrasound. In: Adam A, Dixon AK, Gillard ... Northside Radiology Associates, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the ...

  1. Ultrasound physics.

    Science.gov (United States)

    Shriki, Jesse

    2014-01-01

    Bedside ultrasound has become an important modality for obtaining critical information in the acute care of patients. It is important to understand the physics of ultrasound in order to perform and interpret images at the bedside. The physics of both continuous wave and pulsed wave sound underlies diagnostic ultrasound. The instrumentation, including transducers and image processing, is important in the acquisition of appropriate sonographic images. Understanding how these concepts interplay with each other enables practitioners to obtain the best possible images.

  2. Bornological Locally Convex Cones

    Directory of Open Access Journals (Sweden)

    Davood Ayaseh

    2014-10-01

    Full Text Available In this paper we define bornological and b-bornological cones and investigate their properties. We give some characterization for these cones. In the special case of locally convex topological vector space both these concepts reduce to the known concept  of bornological spaces. We introduce and investigate the  convex quasiuniform   structures U_{tau}, U_{sigma}(P,P* and \\U_{beta}(P,P* on locally convex cone (P,U.

  3. Tissue Harmonic Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Hemmsen, Martin Christian; Rasmussen, Joachim; Jensen, Jørgen Arendt

    2014-01-01

    , and data were recorded with and without pulse inversion for tissue harmonic imaging. Data were acquired using a Sound Technol- ogy 192 element convex array transducer from both a wire phantom and a tissue mimicking phantom to investigate spatial resolution and pen- etration. In-vivo scans were also......Synthetic aperture sequential beamforming (SASB) and tissue har- monic imaging (THI) are combined to improve the image quality of medical ultrasound imaging. The technique is evaluated in a compar- ative study against dynamic receive focusing (DRF). The objective is to investigate if SASB combined...... with THI improves the image qual- ity compared to DRF-THI. The major benet of SASB is a reduced bandwidth between the probe and processing unit. A BK Medical 2202 Ultraview ultrasound scanner was used to acquire beamformed RF data for oine evaluation. The acquisition was made interleaved between methods...

  4. Uniformly Convex Metric Spaces

    OpenAIRE

    Kell Martin

    2014-01-01

    In this paper the theory of uniformly convex metric spaces is developed. These spaces exhibit a generalized convexity of the metric from a fixed point. Using a (nearly) uniform convexity property a simple proof of reflexivity is presented and a weak topology of such spaces is analyzed. This topology called co-convex topology agrees with the usualy weak topology in Banach spaces. An example of a $CAT(0)$-spaces with weak topology which is not Hausdorff is given. This answers questions raised b...

  5. Theory of convex structures

    CERN Document Server

    van de Vel, MLJ

    1993-01-01

    Presented in this monograph is the current state-of-the-art in the theory of convex structures. The notion of convexity covered here is considerably broader than the classic one; specifically, it is not restricted to the context of vector spaces. Classical concepts of order-convex sets (Birkhoff) and of geodesically convex sets (Menger) are directly inspired by intuition; they go back to the first half of this century. An axiomatic approach started to develop in the early Fifties. The author became attracted to it in the mid-Seventies, resulting in the present volume, in which graphs appear si

  6. On convexity in complex networks

    CERN Document Server

    Marc, Tilen

    2016-01-01

    Metric graph properties lie in the heart of the analysis of complex networks, while in this paper we study their convexity. We analyze the expansion of convex subsets of nodes in empirical networks and also convexity of small subgraphs known as graphlets. We demonstrate that convexity is an inherent property of complex networks not present in a random graph. According to our perception of convexity, a convex network is such in which every connected subset of nodes induces a convex subgraph. Especially convex are technological networks and social collaboration graphs, whereas food webs are the only networks studied that are truly non-convex. Many other networks can be divided into a non-convex core surrounded by a convex periphery. We interpret convexity in terms of redundancy of shortest paths in a network and discuss possible applications.

  7. Design and Test of Capacitive Micromachined Ultrasonic Transducer

    National Research Council Canada - National Science Library

    Hongliang Wang; Xiangjun Wang; Changde He; Chenyang Xue; Jijun Xiong; Wendong Zhang; Jing Miao; Yuping Li

    2014-01-01

      Currently, most capacitive micromachined ultrasound transducers, adopting surface sacrificial technology encounter various problems such as difficult cavity etch, low controllability of membrane thickness etc...

  8. Conformal thermal therapy using planar ultrasound transducers and adaptive closed-loop MR temperature control: demonstration in gel phantoms and ex vivo tissues

    Science.gov (United States)

    Tang, K.; Choy, V.; Chopra, R.; Bronskill, M. J.

    2007-05-01

    MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. Integrating a multi-element planar transducer with active MR temperature feedback can enable three-dimensional conformal thermal therapy of a target region within the prostate gland while sparing surrounding normal tissues. Continuous measurement of the temperature distribution in tissue enables dynamic compensation for unknown changes in blood flow and tissue properties during treatment. The main goal of this study was to evaluate the feasibility of using active temperature feedback on a clinical 1.5 T MR imager for conformal thermal therapy. MR thermometry was performed during heating in both gel phantoms and excised tissue with a transurethral heating applicator, and the rotation rate and power were varied based on the thermal measurements. The capability to produce a region of thermal damage that matched a target boundary was evaluated. The influence of a cooling gradient (to simulate cooling of the rectum or urethra) on the desired pattern of thermal damage was also investigated in gel phantoms. Results showed high correlation between the desired target boundary and the 55 °C isotherm generated during heating with an average distance error of 0.9 mm ± 0.4 mm (n = 6) in turkey breasts, 1.4 mm ± 0.6 mm (n = 4) in gel phantoms without rectal cooling and 1.4 mm ± 0.6 mm (n = 3) in gel phantoms with rectal cooling. The results were obtained using a temporal update rate of 5 s, a spatial resolution of 3 × 3 × 10 mm for the control point, and a temperature uncertainty of approximately 1 °C. The performance of the control algorithm under these conditions was comparable to that of simulations conducted previously by our group. Overall, the feasibility of generating targeted regions of thermal damage with a transurethral heating applicator and active MR temperature feedback has been demonstrated experimentally. This method of treatment

  9. Conformal thermal therapy using planar ultrasound transducers and adaptive closed-loop MR temperature control: demonstration in gel phantoms and ex vivo tissues

    Energy Technology Data Exchange (ETDEWEB)

    Tang, K [Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON M4N 3M5 (Canada); Choy, V [Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON M4N 3M5 (Canada); Chopra, R [Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON M4N 3M5 (Canada); Bronskill, M J [Sunnybrook Health Sciences Centre, 2075 Bayview Ave., Toronto, ON M4N 3M5 (Canada)

    2007-05-21

    MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. Integrating a multi-element planar transducer with active MR temperature feedback can enable three-dimensional conformal thermal therapy of a target region within the prostate gland while sparing surrounding normal tissues. Continuous measurement of the temperature distribution in tissue enables dynamic compensation for unknown changes in blood flow and tissue properties during treatment. The main goal of this study was to evaluate the feasibility of using active temperature feedback on a clinical 1.5 T MR imager for conformal thermal therapy. MR thermometry was performed during heating in both gel phantoms and excised tissue with a transurethral heating applicator, and the rotation rate and power were varied based on the thermal measurements. The capability to produce a region of thermal damage that matched a target boundary was evaluated. The influence of a cooling gradient (to simulate cooling of the rectum or urethra) on the desired pattern of thermal damage was also investigated in gel phantoms. Results showed high correlation between the desired target boundary and the 55 deg. C isotherm generated during heating with an average distance error of 0.9 mm {+-} 0.4 mm (n = 6) in turkey breasts, 1.4 mm {+-} 0.6 mm (n = 4) in gel phantoms without rectal cooling and 1.4 mm {+-} 0.6 mm (n = 3) in gel phantoms with rectal cooling. The results were obtained using a temporal update rate of 5 s, a spatial resolution of 3 x 3 x 10 mm for the control point, and a temperature uncertainty of approximately 1 deg. C. The performance of the control algorithm under these conditions was comparable to that of simulations conducted previously by our group. Overall, the feasibility of generating targeted regions of thermal damage with a transurethral heating applicator and active MR temperature feedback has been demonstrated experimentally. This method of

  10. Microinterferometer transducer

    Science.gov (United States)

    Corey, III, Harry S.

    1979-01-01

    An air-bearing microinterferometer transducer is provided for increased accuracy, range and linearity over conventional displacement transducers. A microinterferometer system is housed within a small compartment of an air-bearing displacement transducer housing. A movable cube corner reflector of the interferometer is mounted to move with the displacement gauging probe of the transducer. The probe is disposed for axial displacement by means of an air-bearing. Light from a single frequency laser is directed into an interferometer system within the transducer housing by means of a self-focusing fiber optic cable to maintain light coherency. Separate fringe patterns are monitored by a pair of fiber optic cables which transmit the patterns to a detecting system. The detecting system includes a bidirectional counter which counts the light pattern fringes according to the direction of movement of the probe during a displacement gauging operation.

  11. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds ...

  12. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... or sonography , involves the use of a small transducer (probe) and ultrasound gel placed directly on the ... probe through the gel into the body. The transducer collects the sounds that bounce back and a ...

  13. Dynamic Planar Convex Hull

    DEFF Research Database (Denmark)

    Jacob, Riko

    We determine the computational complexity of the dynamic convex hull problem in the planar case. We present a data structure that maintains a finite set of n points in the plane under insertion and deletion of points in amortized O(log n) time per operation. The space usage of the data structure...... is O(n). The data structure supports extreme point queries in a given direction, tangent queries through a given point, and queries for the neighboring points on the convex hull in O(log n) time. The extreme point queries can be used to decide whether or not a given line intersects the convex hull......, and the tangent queries to determine whether a given point is inside the convex hull. The space usage of the data structure is O(n). We give a lower bound on the amortized asymptotic time complexity that matches the performance of this data structure....

  14. Dynamic Planar Convex Hull

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølfting; Jacob, Rico

    2002-01-01

    In this paper we determine the computational complexity of the dynamic convex hull problem in the planar case. We present a data structure that maintains a finite set of n points in the plane under insertion and deletion of points in amortized O(log n) time per operation. The space usage...... of the data structure is O(n). The data structure supports extreme point queries in a given direction, tangent queries through a given point, and queries for the neighboring points on the convex hull in O(log n) time. The extreme point queries can be used to decide whether or not a given line intersects...... the convex hull, and the tangent queries to determine whether a given point is inside the convex hull. We give a lower bound on the amortized asymptotic time complexity that matches the performance of this data structure....

  15. Acoustic transducer

    Science.gov (United States)

    Drumheller, Douglas S.

    2000-01-01

    An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

  16. Statistical properties of convex clustering

    OpenAIRE

    Tan, Kean Ming; Witten, Daniela

    2015-01-01

    In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and $k$-means clustering. In addition, we derive the range of the tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimator of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to so...

  17. Transducer Field Imaging Using Acoustography

    Directory of Open Access Journals (Sweden)

    Jaswinder S. Sandhu

    2012-01-01

    Full Text Available A common current practice for transducer field mapping is to scan, point-by-point, a hydrophone element in a 2D raster at various distances from the transducer radiating surface. This approach is tedious, requiring hours of scanning time to generate full cross-sectional and/or axial field distributions. Moreover, the lateral resolution of the field distribution image is dependent on the indexing steps between data points. Acoustography is an imaging process in which an acousto-optical (AO area sensor is employed to record the intensity of an ultrasound wavefield on a two-dimensional plane. This paper reports on the application of acoustography as a simple but practical method for assessing transducer field characteristics. A case study performed on a commercial transducer is reported, where the radiated fields are imaged using acoustography and compared to the corresponding quantities that are predicted numerically.

  18. Notions of convexity

    CERN Document Server

    Hörmander, Lars

    1994-01-01

    The first two chapters of this book are devoted to convexity in the classical sense, for functions of one and several real variables respectively. This gives a background for the study in the following chapters of related notions which occur in the theory of linear partial differential equations and complex analysis such as (pluri-)subharmonic functions, pseudoconvex sets, and sets which are convex for supports or singular supports with respect to a differential operator. In addition, the convexity conditions which are relevant for local or global existence of holomorphic differential equations are discussed, leading up to Trépreau’s theorem on sufficiency of condition (capital Greek letter Psi) for microlocal solvability in the analytic category. At the beginning of the book, no prerequisites are assumed beyond calculus and linear algebra. Later on, basic facts from distribution theory and functional analysis are needed. In a few places, a more extensive background in differential geometry or pseudodiffer...

  19. Ultrasonic transducer

    Science.gov (United States)

    Taylor, Steven C.; Kraft, Nancy C.

    2007-03-13

    An ultrasonic transducer having an effective center frequency of about 42 MHz; a bandwidth of greater than 85% at 6 dB; a spherical focus of at least 0.5 inches in water; an F4 lens; a resolution sufficient to be able to detect and separate a 0.005 inch flat-bottomed hole at 0.005 inches below surface; and a beam size of approximately 0.006–0.008 inches measured off a 11/2 mm ball in water at the transducer's focal point.

  20. Language of Transducer Manipulation: Codifying Terms for Effective Teaching.

    Science.gov (United States)

    Bahner, David P; Blickendorf, J Matthew; Bockbrader, Marcia; Adkins, Eric; Vira, Amar; Boulger, Creagh; Panchal, Ashish R

    2016-01-01

    There is a need for consistent, repetitive, and reliable terminology to describe the basic manipulations of the ultrasound transducer. Previously, 5 basic transducer motions have been defined and used in education. However, even with this effort, there is still a lack of consistency and clarity in describing transducer manipulation and motion. In this technical innovation, we describe an expanded definition of transducer motions, which include movements to change the transducer's angle of insonation to the target as well as the location on the body to optimize the ultrasound image. This new terminology may allow for consistent teaching and improved communication in the process of image acquisition.

  1. Convex Geometry and Stoichiometry

    CERN Document Server

    Jer-Chin,

    2011-01-01

    We demonstrate the benefits of a convex geometric perspective for questions on chemical stoichiometry. We show that the balancing of chemical equations, the use of "mixtures" to explain multiple stoichiometry, and the half-reaction for balancing redox actions all yield nice convex geometric interpretations. We also relate some natural questions on reaction mechanisms with the enumeration of lattice points in polytopes. Lastly, it is known that a given reaction mechanism imposes linear constraints on observed stoichiometries. We consider the inverse question of deducing reaction mechanism consistent with a given set of linear stoichiometric restrictions.

  2. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

    OpenAIRE

    Zhou, Qifa; Lau, Sienting; WU, DAWEI; Shung, K. Kirk

    2011-01-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the curr...

  3. Prostate Ultrasound

    Medline Plus

    Full Text Available ... and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through ... during a single exam. The transducer sends out high-frequency sound waves (that the human ear cannot hear) ...

  4. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through ... during a single exam. The transducer sends out high-frequency sound waves (that the human ear cannot hear) ...

  5. SMOOTHING BY CONVEX QUADRATIC PROGRAMMING

    Institute of Scientific and Technical Information of China (English)

    Bing-sheng He; Yu-mei Wang

    2005-01-01

    In this paper, we study the relaxed smoothing problems with general closed convex constraints. It is pointed out that such problems can be converted to a convex quadratic minimization problem for which there are good programs in software libraries.

  6. Global approximation of convex functions

    CERN Document Server

    Azagra, D

    2011-01-01

    We show that for every (not necessarily bounded) open convex subset $U$ of $\\R^n$, every (not necessarily Lipschitz or strongly) convex function $f:U\\to\\R$ can be approximated by real analytic convex functions, uniformly on all of $U$. In doing so we provide a technique which transfers results on uniform approximation on bounded sets to results on uniform approximation on unbounded sets, in such a way that not only convexity and $C^k$ smoothness, but also local Lipschitz constants, minimizers, order, and strict or strong convexity, are preserved. This transfer method is quite general and it can also be used to obtain new results on approximation of convex functions defined on Riemannian manifolds or Banach spaces. We also provide a characterization of the class of convex functions which can be uniformly approximated on $\\R^n$ by strongly convex functions.

  7. Ultrasound presentation of abdominal non-Hodgkin lymphomas in pediatric patients

    Directory of Open Access Journals (Sweden)

    Agnieszka Brodzisz

    2013-12-01

    Full Text Available Introduction: Burkitt’s lymphoma accounts for approximately 25% of lymphomas diagnosed in children of developmental age. The tumor is localized mainly in the intestine (usually in the ileocecal region, mesenteric lymph nodes and extraperitoneal space. The clinical symptoms are non-specific and include: abdominal pain, vomiting, gastrointestinal bleeding, and acute abdomen suggesting appendicitis or intestinal intussusception. On ultrasound examination, Burkitt’s lymphoma may manifest itself in various ways, depending on the origin of the lesion. Aim: The aim of this paper was to review the ultrasound manifestation of abdominal Burkitt’s lymphoma in children. Material and methods: The analysis included 15 pediatric patients with Burkitt’s non-Hodgkin lymphoma in the abdominal cavity. The mean age of the patients was 9.5. Abdominal and gastrointestinal ultrasound examinations were conducted using a Siemens scanner with a convex transducer of 3.5–5 MHz and linear array transducer of L4 – 7.5 MHz. Results: Ultrasound examinations conducted in the group of 15 patients revealed pathological masses localized in the gastric wall in 3 patients (20%, in the ileocecal region in 10 patients (67% and a disseminated process in 2 patients (13%. In 12 patients with a diagnosed Burkitt’s non-Hodgkin lymphoma in an extragastric localization, differences in the morphology of the lesions were observed. Conclusions: The clinical and ultrasound picture of abdominal Burkitt’s lymphoma in children is variable. A careful ultrasound assessment of all abdominal organs conducted with the use of convex and linear probes increases the chances of establishing an adequate diagnosis.

  8. Egalitarianism in Convex Fuzzy Games

    NARCIS (Netherlands)

    Brânzei, R.; Dimitrov, D.A.; Tijs, S.H.

    2002-01-01

    In this paper the egalitarian solution for convex cooperative fuzzy games is introduced.The classical Dutta-Ray algorithm for finding the constrained egalitarian solution for convex crisp games is adjusted to provide the egalitarian solution of a convex fuzzy game.This adjusted algorithm is also a f

  9. Average Convexity in Communication Situations

    NARCIS (Netherlands)

    Slikker, M.

    1998-01-01

    In this paper we study inheritance properties of average convexity in communication situations. We show that the underlying graph ensures that the graphrestricted game originating from an average convex game is average convex if and only if every subgraph associated with a component of the underlyin

  10. Pressure transducer

    Science.gov (United States)

    Anderson, Thomas T.; Roop, Conard J.; Schmidt, Kenneth J.; Gunchin, Elmer R.

    1989-01-01

    A pressure transducer suitable for use in high temperature environments includes two pairs of induction coils, each pair being bifilarly wound together, and each pair of coils connected as opposite arms of a four arm circuit; an electrically conductive target moveably positioned between the coil pairs and connected to a diaphragm such that deflection of the diaphragm causes axial movement of the target and an unbalance in the bridge output.

  11. Efficient Approximation of Convex Recolorings

    OpenAIRE

    Moran, Shlomo; Snir, Sagi

    2005-01-01

    A coloring of a tree is convex if the vertices that pertain to any color induce a connected subtree; a partial coloring (which assigns colors to some of the vertices) is convex if it can be completed to a convex (total) coloring. Convex coloring of trees arise in areas such as phylogenetics, linguistics, etc. eg, a perfect phylogenetic tree is one in which the states of each character induce a convex coloring of the tree. Research on perfect phylogeny is usually focused on finding a tree so t...

  12. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... areas of the body while other areas, especially air-filled lungs, are poorly suited for ultrasound. top ... make secure contact with the body and eliminate air pockets between the transducer and the skin that ...

  13. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the ... the transducer (the device placed on the patient's skin to send and receive the returning sound waves), ...

  14. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... organs and to examine a baby in pregnant women and the brain and hips in infants. It’s ... Transvaginal ultrasound. The transducer is inserted into a woman's vagina to view the uterus and ovaries. top ...

  15. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... whether the object is solid or filled with fluid). In medicine, ultrasound is used to detect changes ... As the sound waves bounce off internal organs, fluids and tissues, the sensitive receiver in the transducer ...

  16. Convex Graph Invariants

    Science.gov (United States)

    2010-12-02

    evaluating the function ΘP (A) for any fixed A,P is equivalent to solving the so-called Quadratic Assignment Problem ( QAP ), and thus we can employ various...tractable linear programming, spectral, and SDP relaxations of QAP [40, 11, 33]. In particular we discuss recent work [14] on exploiting group...symmetry in SDP relaxations of QAP , which is useful for approximately computing elementary convex graph invariants in many interesting cases. Finally in

  17. Spatial impulse response of a rectangular double curved transducer

    DEFF Research Database (Denmark)

    Bæk, David; Jensen, Jørgen Arendt; Willatzen, Morten

    2012-01-01

    Calculation of the pressure field from transducers having both a convex and a concave surface geometry is a complicated assignment that often is accomplished by subdividing the transducer surface into smaller flat elements of which the spatial impulse response is known. This method is often seen...... applied to curved transducers because an analytical solution is un-known. In this work a semi-analytical algorithm for the exact solution to a first order in diffraction effect of the spatial impulse response of rectangular shaped double curved transducers is presented. The algorithm and an approximation...... approximations ranging from 0.03 % to 0.8 % relative to a numerical solution for the spatial impulse response. It is shown that the presented algorithm gives consistent results with Field II for a linear flat, a linear focused, and a convex non-focused element. Best solution was found to be 0.01 % with a three...

  18. Ultrasound pregnancy

    Science.gov (United States)

    Pregnancy sonogram; Obstetric ultrasonography; Obstetric sonogram; Ultrasound - pregnancy; IUGR - ultrasound; Intrauterine growth - ultrasound; Polyhydramnios - ultrasound; Oligohydramnios - ultrasound; ...

  19. Introducing the Adaptive Convex Enveloping

    CERN Document Server

    Yu, Sheng

    2011-01-01

    Convexity, though extremely important in mathematical programming, has not drawn enough attention in the field of dynamic programming. This paper gives conditions for verifying convexity of the cost-to-go functions, and introduces an accurate, fast and reliable algorithm for solving convex dynamic programs with multivariate continuous states and actions, called Adaptive Convex Enveloping. This is a short introduction of the core technique created and used in my dissertation, so it is less formal, and misses some parts, such as literature review and reference, compared to a full journal paper.

  20. Convex polytopes and quantum states

    Energy Technology Data Exchange (ETDEWEB)

    Wilmott, Colin; Kampermann, Hermann; Bruss, Dagmar [Institut fuer Theoretische Physik III, Heinrich-Heine-Universitaet Duesseldorf (Germany)

    2010-07-01

    A convex polytope is defined as the convex hull of a finite non-empty set of vectors. We present a theorem of Rado (1952) which characterizes the convex hull of the collection of all permutations of a given real d-tuple in terms of the Hardy-Littlewood-Polya spectral order relation prec. We give a necessary and sufficient condition to construct a d-dimensional convex polytope which utilizes Rado's original (d-1)-dimensional characterization, and we describe how the resulting polytope may be placed in a quantum mechanical framework.

  1. Cryogenic Clamp-on Ultrasonic Flowmeters using Single Crystal Piezoelectric Transducers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Clamp-on ultrasound cryogenic flowmeters using single crystal piezoelectric transducers are proposed to enable reliable, accurate cryogenic instrumentation needs in...

  2. Exploiting Ultrasound Harmonics

    NARCIS (Netherlands)

    G.M. Matte (Guillaume)

    2010-01-01

    textabstractUltrasound imaging is an inexpensive method which provides an accurate diagnosis tool. This thesis provides elements to characterise the acoustic pressure generated by ultrasound transducers as well as signal processing method that could improve modern echography. The first measurement

  3. Exploiting Ultrasound Harmonics

    NARCIS (Netherlands)

    G.M. Matte (Guillaume)

    2010-01-01

    textabstractUltrasound imaging is an inexpensive method which provides an accurate diagnosis tool. This thesis provides elements to characterise the acoustic pressure generated by ultrasound transducers as well as signal processing method that could improve modern echography. The first measurement

  4. Convex Games versus Clan Games

    NARCIS (Netherlands)

    Brânzei, R.; Dimitrov, D.A.; Tijs, S.H.

    2006-01-01

    In this paper we provide characterizations of convex games and total clan games by using properties of their corresponding marginal games.We show that a "dualize and restrict" procedure transforms total clan games with zero worth for the clan into monotonic convex games.Furthermore, each monotonic

  5. Wideband Single Crystal Transducer for Bone Characterization Project

    Data.gov (United States)

    National Aeronautics and Space Administration — TRS proposes to develop a simple-to-use, launch capable, ultrasound transducer that is capable of producing the necessary bandwidth to accurately determine in vivo...

  6. Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation.

    Science.gov (United States)

    Kwiecinski, Wojciech; Bessière, Francis; Colas, Elodie Constanciel; N'Djin, W Apoutou; Tanter, Mickaël; Lafon, Cyril; Pernot, Mathieu

    2015-10-21

    Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion's extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions. First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle (n = 11) and mapped (n = 7). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n  =  3), then atrial (left, n = 2) and ventricular (left n = 1, right n = 1) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE. During the cardiac cycle stiffness varied from 0.5   ±   0.1 kPa to 6.0   ±   0.3 kPa in the atrium and from 1.3   ±   0.3 kPa to 13.5   ±   9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3   ±   5.5 kPa (versus 4.4   ±   1.6 kPa before ablation) in the chicken breast, to 30.3   ±   10.3 kPa (versus 12.2   ±   4.3 kPa) in the atria and to 73.8

  7. Convex Optimization without Projection Steps

    CERN Document Server

    Jaggi, Martin

    2011-01-01

    We study the general problem of minimizing a convex function over a compact convex domain. We will investigate a simple iterative approximation algorithm that does not need projection steps in order to stay inside the optimization domain. Instead of a projection step, the linearized problem defined by a current subgradient is solved, which gives a step direction that will naturally stay in the domain. The approach generalizes the sparse greedy algorithm of Clarkson (and the low-rank SDP solver by Hazan) to arbitrary convex domains, and to using subgradients for the case of non-differentiable convex functions. Analogously, we give a convergence proof guaranteeing {\\epsilon}-small duality gap after O(1/{\\epsilon}) iterations. The framework allows us understand the sparsity of approximate solutions for any l1-regularized convex optimization problem, expressed as a function of the approximation quality. We obtain matching upper and lower bounds of {\\Theta}(1/{\\epsilon}) for the sparsity for l1-problems. The same ...

  8. Focused ultrasound in ophthalmology

    Directory of Open Access Journals (Sweden)

    Silverman RH

    2016-09-01

    Full Text Available Ronald H Silverman1,2 1Department of Ophthalmology, Columbia University Medical Center, 2F.L. Lizzi Center for Biomedical Engineering, Riverside Research, New York, NY, USA Abstract: The use of focused ultrasound to obtain diagnostically significant information about the eye goes back to the 1950s. This review describes the historical and technological development of ophthalmic ultrasound and its clinical application and impact. Ultrasound, like light, can be focused, which is crucial for formation of high-resolution, diagnostically useful images. Focused, single-element, mechanically scanned transducers are most common in ophthalmology. Specially designed transducers have been used to generate focused, high-intensity ultrasound that through thermal effects has been used to treat glaucoma (via cilio-destruction, tumors, and other pathologies. Linear and annular transducer arrays offer synthetic focusing in which precise timing of the excitation of independently addressable array elements allows formation of a converging wavefront to create a focus at one or more programmable depths. Most recently, linear array-based plane-wave ultrasound, in which the array emits an unfocused wavefront and focusing is performed solely on received data, has been demonstrated for imaging ocular anatomy and blood flow. While the history of ophthalmic ultrasound extends back over half-a-century, new and powerful technologic advances continue to be made, offering the prospect of novel diagnostic capabilities. Keywords: ophthalmic ultrasound, ultrasound biomicroscopy (UBM, high-intensity focused ultrasound (HIFU, ultrafast imaging, Doppler imaging 

  9. Adaptive Thermal Therapy using Planar Ultrasound Transducers with Real-time MR Temperature Feedback: Demonstration in Gel Phantoms and Ex-vivo Tissues

    Science.gov (United States)

    Tang, Kee; Choy, Vanessa; Chopra, Rajiv; Bronskill, Michael

    2007-05-01

    MRI-guided transurethral ultrasound therapy offers a minimally invasive approach for the treatment of localized prostate cancer. The main goal of this study was to evaluate active temperature feedback on a clinical 1.5T MR imager to control conformal thermal therapy. MR thermometry was performed during heating in both thermal gel phantoms and ex-vivo tissue with a single-element transurethral heating applicator. The applicator rotation rate and power were controlled based on MRI-temperature measurements. The influence of a cooling gradient (to simulate cooling of the rectum or urethra) was also investigated in gel phantoms. The 55°C isotherm generated during heating closely matched the targeted prostate shape, with an average distance error of 0.9 mm ± 0.4 mm in turkey breasts, 1.3 mm ± 0.5 mm in gel phantoms without rectal cooling and 1.4 mm ± 0.6 mm in gel phantoms with rectal cooling. Accurate, MRI-guided, active feedback has been successfully demonstrated experimentally and has the capability to adjust for unpredictable and varying tissue properties during the treatment.

  10. Transverse Oscillation Vector Velocity Estimation using a Phased Array Transducer

    DEFF Research Database (Denmark)

    Marcher, Jønne; Pihl, Michael Johannes; Seerup, Gert

    2012-01-01

    The Transverse Oscillation method has shown its commercial feasibility, providing the user with 2D velocity information. Todays implementation on commercial ultrasound platforms only support linear array transducers and are limited in depth. Extending the implementation to a phased array transducer...

  11. Tissue harmonic synthetic aperture ultrasound imaging.

    Science.gov (United States)

    Hemmsen, Martin Christian; Rasmussen, Joachim Hee; Jensen, Jørgen Arendt

    2014-10-01

    Synthetic aperture sequential beamforming (SASB) and tissue harmonic imaging (THI) are combined to improve the image quality of medical ultrasound imaging. The technique is evaluated in a comparative study against dynamic receive focusing (DRF). The objective is to investigate if SASB combined with THI improves the image quality compared to DRF-THI. The major benefit of SASB is a reduced bandwidth between the probe and processing unit. A BK Medical 2202 Ultraview ultrasound scanner was used to acquire beamformed RF data for offline evaluation. The acquisition was made interleaved between methods, and data were recorded with and without pulse inversion for tissue harmonic imaging. Data were acquired using a Sound Technology 192 element convex array transducer from both a wire phantom and a tissue mimicking phantom to investigate spatial resolution and penetration. In vivo scans were also performed for a visual comparison. The spatial resolution for SASB-THI is on average 19% better than DRI-THI, and the investigation of penetration showed equally good signal-to-noise ratio. In vivo B-mode scans were made and compared. The comparison showed that SASB-THI reduces the artifact and noise interference and improves image contrast and spatial resolution.

  12. Decision Problems For Convex Languages

    CERN Document Server

    Brzozowski, Janusz; Xu, Zhi

    2008-01-01

    In this paper we examine decision problems associated with various classes of convex languages, studied by Ang and Brzozowski (under the name "continuous languages''). We show that we can decide whether a given language L is prefix-, suffix-, factor-, or subword-convex in polynomial time if L is represented by a DFA, but that the problem is PSPACE-hard if L is represented by an NFA. In the case that a regular language is not convex, we prove tight upper bounds on the length of the shortest words demonstrating this fact, in terms of the number of states of an accepting DFA. Similar results are proved for some subclasses of convex languages: the prefix-, suffix-, factor-, and subword-closed languages, and the prefix-, suffix-, factor-, and subword-free languages.

  13. Covering Numbers for Convex Functions

    CERN Document Server

    Guntuboyina, Adityanand

    2012-01-01

    In this paper we study the covering numbers of the space of convex and uniformly bounded functions in multi-dimension. We find optimal upper and lower bounds for the $\\epsilon$-covering number of $\\C([a, b]^d, B)$, in the $L_p$-metric, $1 \\le p 0$, and $\\C([a,b]^d, B)$ denotes the set of all convex functions on $[a, b]^d$ that are uniformly bounded by $B$. We summarize previously known results on covering numbers for convex functions and also provide alternate proofs of some known results. Our results have direct implications in the study of rates of convergence of empirical minimization procedures as well as optimal convergence rates in the numerous convexity constrained function estimation problems.

  14. Model of a Piezoelectric Transducer

    Science.gov (United States)

    Goodenow, Debra

    2004-01-01

    It's difficult to control liquid and gas in propellant tanks in zero gravity. A possible a design would utilize acoustic liquid manipulation (ALM) technology which uses ultrasonic beams conducted through a liquid and solid media, to push gas bubbles in the liquid to desirable locations. We can propel and control the bubble with acoustic radiation pressure by aiming the acoustic waves on the bubble s surface. This allows us to design a so called smart tank in which the ALM devices transfer the gas to the outer wall of the tank and isolating the liquid in the center. Because the heat transfer rate of a gas is lower of that of the liquid it would substantially decrease boil off and provide of for a longer storage life. The ALM beam is composed of little wavelets which are individual waves that constructively interfere with each other to produce a single, combined acoustic wave front. This is accomplished by using a set of synchronized ultrasound transducers arranged in an array. A slight phase offset of these elements allows us to focus and steer the beam. The device that we are using to produce the acoustic beam is called the piezoelectric transducer. This device converts electrical energy to mechanical energy, which appears in the form of acoustic energy. Therefore the behavior of the device is dependent on both the mechanical characteristics, such as its density, cross-sectional area, and its electrical characteristics, such as, electric flux permittivity and coupling factor. These devices can also be set up in a number of modes which are determined by the way the piezoelectric device is arranged, and the shape of the transducer. For this application we are using the longitudinal or thickness mode for our operation. The transducer also vibrates in the lateral mode, and one of the goals of my project is to decrease the amount of energy lost to the lateral mode. To model the behavior of the transducers I will be using Pspice, electric circuit modeling tool, to

  15. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... blood flow (such as clots) narrowing of vessels tumors and congenital vascular malformations reduced or absent blood ... vessels or to detect abnormal masses, such as tumors. In an ultrasound examination, a transducer both sends ...

  16. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... areas of the body while other areas, especially air-filled lungs, are poorly suited for ultrasound. top ... make secure contact with the body and eliminate air pockets between the transducer and the skin that ...

  17. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the ... the transducer (the device placed on the patient's skin to send and receive the returning sound waves), ...

  18. Complex Convexity of Orlicz Modular Sequence Spaces

    Directory of Open Access Journals (Sweden)

    Lili Chen

    2016-01-01

    Full Text Available The concepts of complex extreme points, complex strongly extreme points, complex strict convexity, and complex midpoint locally uniform convexity in general modular spaces are introduced. Then we prove that, for any Orlicz modular sequence space lΦ,ρ, lΦ,ρ is complex midpoint locally uniformly convex. As a corollary, lΦ,ρ is also complex strictly convex.

  19. Uniformly convex-transitive function spaces

    OpenAIRE

    Rambla-Barreno, Fernando; Talponen, Jarno

    2009-01-01

    We introduce a property of Banach spaces called uniform convex-transitivity, which falls between almost transitivity and convex-transitivity. We will provide examples of uniformly convex-transitive spaces. This property behaves nicely in connection with some Banach-valued function spaces. As a consequence, we obtain new examples of convex-transitive Banach spaces.

  20. On Fuzzy Simplex and Fuzzy Convex Hull

    Institute of Scientific and Technical Information of China (English)

    Dong QIU; Wei Quan ZHANG

    2011-01-01

    In this paper,we discuss fuzzy simplex and fuzzy convex hull,and give several representation theorems for fuzzy simplex and fuzzy convex hull.In addition,by giving a new characterization theorem of fuzzy convex hull,we improve some known results about fuzzy convex hull.

  1. The Convex Coordinates of the Symmedian Point

    Science.gov (United States)

    Boyd, J. N.; Raychowdhury, P. N.

    2006-01-01

    In this note, we recall the convex (or barycentric) coordinates of the points of a closed triangular region. We relate the convex and trilinear coordinates of the interior points of the triangular region. We use the relationship between convex and trilinear coordinates to calculate the convex coordinates of the symmedian point of the triangular…

  2. Convexity Adjustments for ATS Models

    DEFF Research Database (Denmark)

    Murgoci, Agatha; Gaspar, Raquel M.

    Practitioners are used to value a broad class of exotic interest rate derivatives simply by preforming for what is known as convexity adjustments (or convexity corrections). We start by exploiting the relations between various interest rate models and their connections to measure changes. As a re......Practitioners are used to value a broad class of exotic interest rate derivatives simply by preforming for what is known as convexity adjustments (or convexity corrections). We start by exploiting the relations between various interest rate models and their connections to measure changes....... As a result we classify convexity adjustments into forward adjustments and swaps adjustments. We, then, focus on affine term structure (ATS) models and, in this context, conjecture convexity adjustments should be related of affine functionals. In the case of forward adjustments, we show how to obtain exact...... formulas. Concretely for LIBOR in arrears (LIA) contracts, we derive the system of Riccatti ODE-s one needs to compute to obtain the exact adjustment. Based upon the ideas of Schrager and Pelsser (2006) we are also able to derive general swap adjustments useful, in particular, when dealing with constant...

  3. Compactly convex sets in linear topological spaces

    CERN Document Server

    Banakh, T; Ravsky, O

    2012-01-01

    A convex subset X of a linear topological space is called compactly convex if there is a continuous compact-valued map $\\Phi:X\\to exp(X)$ such that $[x,y]\\subset\\Phi(x)\\cup \\Phi(y)$ for all $x,y\\in X$. We prove that each convex subset of the plane is compactly convex. On the other hand, the space $R^3$ contains a convex set that is not compactly convex. Each compactly convex subset $X$ of a linear topological space $L$ has locally compact closure $\\bar X$ which is metrizable if and only if each compact subset of $X$ is metrizable.

  4. Powers of Convex-Cyclic Operators

    Directory of Open Access Journals (Sweden)

    Fernando León-Saavedra

    2014-01-01

    Full Text Available A bounded operator T on a Banach space X is convex cyclic if there exists a vector x such that the convex hull generated by the orbit Tnxn≥0 is dense in X. In this note we study some questions concerned with convex-cyclic operators. We provide an example of a convex-cyclic operator T such that the power Tn fails to be convex cyclic. Using this result we solve three questions posed by Rezaei (2013.

  5. A class of free locally convex spaces

    Science.gov (United States)

    Sipacheva, O. V.

    2003-04-01

    Stratifiable spaces are a natural generalization of metrizable spaces for which Dugundji's theorem holds. It is proved that the free locally convex space of a stratifiable space is stratifiable. This means, in particular, that the space of finitely supported probability measures on a stratifiable space is a retract of a locally convex space, and that each stratifiable convex subset of a locally convex space is a retract of a locally convex space.

  6. An IVUS Transducer for Microbubble Therapies

    Science.gov (United States)

    Kilroy, Joseph P.; Patil, Abhay V.; Rychak, Joshua J.; Hossack, John A.

    2014-01-01

    There is interest in examining the potential of modified intravascular ultrasound (IVUS) catheters to facilitate dual diagnostic and therapeutic roles using ultrasound plus microbubbles for localized drug delivery to the vessel wall. The goal of this study was to design, prototype, and validate an IVUS transducer for microbubble-based drug delivery. A 1-D acoustic radiation force model and finite element analysis guided the design of a 1.5-MHz IVUS transducer. Using the IVUS transducer, biotinylated microbubbles were displaced in water and bovine whole blood to the streptavidin-coated wall of a flow phantom by a 1.5-MHz center frequency, peak negative pressure = 70 kPa pulse with varying pulse repetition frequency (PRF) while monitoring microbubble adhesion with ultrasound. A fit was applied to the RF data to extract a time constant (τ). As PRF was increased in water, the time constant decreased (τ = 32.6 s, 1 kHz vs. τ = 8.2 s, 6 kHz), whereas in bovine whole blood an adhesion–no adhesion transition was found for PRFs ≥ 8 kHz. Finally, a fluorophore was delivered to an ex vivo swine artery using microbubbles and the IVUS transducer, resulting in a 6.6-fold increase in fluorescence. These results indicate the importance of PRF (or duty factor) for IVUS acoustic radiation force microbubble displacement and the potential for IVUS and microbubbles to provide localized drug delivery. PMID:24569249

  7. High temperature, high power piezoelectric composite transducers.

    Science.gov (United States)

    Lee, Hyeong Jae; Zhang, Shujun; Bar-Cohen, Yoseph; Sherrit, Stewart

    2014-08-08

    Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

  8. High Temperature, High Power Piezoelectric Composite Transducers

    Directory of Open Access Journals (Sweden)

    Hyeong Jae Lee

    2014-08-01

    Full Text Available Piezoelectric composites are a class of functional materials consisting of piezoelectric active materials and non-piezoelectric passive polymers, mechanically attached together to form different connectivities. These composites have several advantages compared to conventional piezoelectric ceramics and polymers, including improved electromechanical properties, mechanical flexibility and the ability to tailor properties by using several different connectivity patterns. These advantages have led to the improvement of overall transducer performance, such as transducer sensitivity and bandwidth, resulting in rapid implementation of piezoelectric composites in medical imaging ultrasounds and other acoustic transducers. Recently, new piezoelectric composite transducers have been developed with optimized composite components that have improved thermal stability and mechanical quality factors, making them promising candidates for high temperature, high power transducer applications, such as therapeutic ultrasound, high power ultrasonic wirebonding, high temperature non-destructive testing, and downhole energy harvesting. This paper will present recent developments of piezoelectric composite technology for high temperature and high power applications. The concerns and limitations of using piezoelectric composites will also be discussed, and the expected future research directions will be outlined.

  9. Duplex ultrasound

    Science.gov (United States)

    Vascular ultrasound; Peripheral vascular ultrasound ... A duplex ultrasound combines: Traditional ultrasound: This uses sound waves that bounce off blood vessels to create pictures. Doppler ultrasound: This ...

  10. The genealogy of convex solids

    CERN Document Server

    Domokos, Gabor; Szabó, Timea

    2012-01-01

    The shape of homogeneous, smooth convex bodies as described by the Euclidean distance from the center of gravity represents a rather restricted class M_C of Morse-Smale functions on S^2. Here we show that even M_C exhibits the complexity known for general Morse-Smale functions on S^2 by exhausting all combinatorial possibilities: every 2-colored quadrangulation of the sphere is isomorphic to a suitably represented Morse-Smale complex associated with a function in M_C (and vice versa). We prove our claim by an inductive algorithm, starting from the path graph P_2 and generating convex bodies corresponding to quadrangulations with increasing number of vertices by performing each combinatorially possible vertex splitting by a convexity- preserving local manipulation of the surface. Since convex bodies carrying Morse-Smale complexes isomorphic to P_2 exist, this algorithm not only proves our claim but also defines a hierarchical order among convex solids and general- izes the known classification scheme in [35], ...

  11. NP-completeness of weakly convex and convex dominating set decision problems

    Directory of Open Access Journals (Sweden)

    Joanna Raczek

    2004-01-01

    Full Text Available The convex domination number and the weakly convex domination number are new domination parameters. In this paper we show that the decision problems of convex and weakly convex dominating sets are \\(NP\\-complete for bipartite and split graphs. Using a modified version of Warshall algorithm we can verify in polynomial time whether a given subset of vertices of a graph is convex or weakly convex.

  12. Macro tree transducers

    NARCIS (Netherlands)

    Engelfriet, Joost; Vogler, Heiko

    1985-01-01

    Macro tree transducers are a combination of top-down tree transducers and macro grammars. They serve as a model for syntax-directed semantics in which context information can be handled. In this paper the formal model of macro tree transducers is studied by investigating typical automata theoretical

  13. Megahertz tonpilz transducer

    Science.gov (United States)

    Van Tol, Dave; Hughes, W. Jack

    1999-06-01

    The tonpilz configuration is applied to a transducer operating in the megahertz frequency range. The KLM model is used to design the transducer using readily available components. The construction techniques used are the same as those applied to standard high frequency transducers. Modeled and measured pulse-echo results display a high level of agreement, but impedance and sensitivity comparisons are less promising.

  14. Macro tree transducers

    NARCIS (Netherlands)

    Engelfriet, Joost; Vogler, Heiko

    1985-01-01

    Macro tree transducers are a combination of top-down tree transducers and macro grammars. They serve as a model for syntax-directed semantics in which context information can be handled. In this paper the formal model of macro tree transducers is studied by investigating typical automata theoretical

  15. Local Routing in Convex Subdivisions

    DEFF Research Database (Denmark)

    Bose, Prosenjit; Durocher, Stephane; Mondal, Debajyoti;

    2015-01-01

    In various wireless networking settings, node locations determine a network’s topology, allowing the network to be modelled by a geometric graph drawn in the plane. Without any additional information, local geometric routing algorithms can guarantee delivery to the target node only in restricted...... classes of geometric graphs, such as triangulations. In order to guarantee delivery on more general classes of geometric graphs (e.g., convex subdivisions or planar subdivisions), previous local geometric routing algorithms required Θ(logn) state bits to be stored and passed with the message. We present...... the first local geometric routing algorithm using only one state bit to guarantee delivery on convex subdivisions and the first local geometric memoryless routing algorithm that guarantees delivery on edge-augmented monotone subdivisions (including all convex subdivisions) when the algorithm has knowledge...

  16. Microelectronics mounted on a piezoelectric transducer: method, simulations, and measurements.

    Science.gov (United States)

    Johansson, Jonny; Delsing, Jerker

    2006-01-01

    This paper describes the design of a highly integrated ultrasound sensor where the piezoelectric ceramic transducer is used as the carrier for the driver electronics. Intended as one part in a complete portable, battery operated ultrasound sensor system, focus has been to achieve small size and low power consumption. An optimized ASIC driver stage is mounted directly on the piezoelectric transducer and connected using wire bond technology. The absence of wiring between driver and transducer provides excellent pulse control possibilities and eliminates the need for broad band matching networks. Estimates of the sensor power consumption are made based on the capacitive behavior of the piezoelectric transducer. System behavior and power consumption are simulated using SPICE models of the ultrasound transducer together with transistor level modelling of the driver stage. Measurements and simulations are presented of system power consumption and echo energy in a pulse echo setup. It is shown that the power consumption varies with the excitation pulse width, which also affects the received ultrasound energy in a pulse echo setup. The measured power consumption for a 16 mm diameter 4.4 MHz piezoelectric transducer varies between 95 microW and 130 microW at a repetition frequency of 1 kHz. As a lower repetition frequency gives a linearly lower power consumption, very long battery operating times can be achieved. The measured results come very close to simulations as well as estimated ideal minimum power consumption.

  17. Quality assurance in diagnostic ultrasound

    Energy Technology Data Exchange (ETDEWEB)

    Sipilae, Outi, E-mail: outi.sipila@hus.fi [HUS Helsinki Medical Imaging Center, Helsinki University Central Hospital, P.O. Box 340, 00029 HUS (Finland); Mannila, Vilma, E-mail: vilma.mannila@hus.fi [HUS Helsinki Medical Imaging Center, Helsinki University Central Hospital, P.O. Box 340, 00029 HUS (Finland); Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki University (Finland); Vartiainen, Eija, E-mail: eija.vartiainen@hus.fi [HUS Helsinki Medical Imaging Center, Helsinki University Central Hospital, P.O. Box 750, 00029 HUS (Finland)

    2011-11-15

    Objective: To setup a practical ultrasound quality assurance protocol in a large radiological center, results from transducer tests, phantom measurements and visual checks for physical faults were compared. Materials and methods: Altogether 151 transducers from 54 ultrasound scanners, from seven different manufacturers, were tested with a Sonora FirstCall aPerio{sup TM} system (Sonora Medical Systems, Inc., Longmont, CO, USA) to detect non-functional elements. Phantom measurements using a CIRS General Purpose Phantom Model 040 (CIRS Tissue Simulation and Phantom Technology, VA, USA) were available for 135 transducers. The transducers and scanners were also checked visually for physical faults. The percentages of defective findings in these tests were computed. Results: Defective results in the FirstCall tests were found in 17% of the 151 transducers, and in 16% of the 135 transducers. Defective image quality resulted with 15% of the transducers, and 25% of the transducers had a physical flaw. In 16% of the scanners, a physical fault elsewhere than in the transducer was found. Seven percent of the transducers had a concurrent defective result both in the FirstCall test and in the phantom measurements, 8% in the FirstCall test and in the visual check, 4% in the phantom measurements and in the visual check, and 2% in all three tests. Conclusion: The tested methods produced partly complementary results and seemed all to be necessary. Thus a quality assurance protocol is forced to be rather labored, and therefore the benefits and costs must be closely followed.

  18. Iterative reconstruction of the transducer surface velocity.

    Science.gov (United States)

    Alles, Erwin; van Dongen, Koen

    2013-05-01

    Ultrasound arrays used for medical imaging consist of many elements placed closely together. Ideally, each element vibrates independently. However, because of mechanical coupling, crosstalk between neighboring elements may occur. To quantify the amount of crosstalk, the transducer velocity distribution should be measured. In this work, a method is presented to reconstruct the velocity distribution from far-field pressure field measurements acquired over an arbitrary surface. The distribution is retrieved from the measurements by solving an integral equation, derived from the Rayleigh integral of the first kind, using a conjugate gradient inversion scheme. This approach has the advantages that it allows for arbitrary transducer and pressure field measurement geometries, as well as the application of regularization techniques. Numerical experiments show that measuring the pressure field along a hemisphere enclosing the transducer yields significantly more accurate reconstructions than measuring along a parallel plane. In addition, it is shown that an increase in accuracy is achieved when the assumption is made that all points on the transducer surface vibrate in phase. Finally, the method has been tested on an actual transducer with an active element of 700 × 200 μm which operates at a center frequency of 12.2 MHz. For this transducer, the velocity distribution has been reconstructed accurately to within 50 μm precision from pressure measurements at a distance of 1.98 mm (=16λ0) using a 200-μm-diameter needle hydrophone.

  19. Quantum information and convex optimization

    Energy Technology Data Exchange (ETDEWEB)

    Reimpell, Michael

    2008-07-01

    This thesis is concerned with convex optimization problems in quantum information theory. It features an iterative algorithm for optimal quantum error correcting codes, a postprocessing method for incomplete tomography data, a method to estimate the amount of entanglement in witness experiments, and it gives necessary and sufficient criteria for the existence of retrodiction strategies for a generalized mean king problem. (orig.)

  20. Comparison of conventional and PureWave Crystal transducer in obstetric sonography.

    Science.gov (United States)

    Yu, Yi Min; Chen, Min; Xiong, Yi; Chau, Macy Mo Ching; Li, Rosita Siu Hung; Lau, Tze Kin

    2009-07-01

    To compare the quality of ultrasound images acquired by the new PureWave Crystal transducer with those acquired by a conventional transducer in 'difficult' obstetric subjects. A predefined list of ultrasound images were obtained from 35 'difficult' obstetric patients using both conventional and new PureWave Crystal transducers by a sonographer. All images were rated using a three-point scale by an independent assessor. Both the sonographer and assessor were experienced in obstetric ultrasound and blinded to the type of transducers being used. A higher score represented better image quality. The scores of each pair of images obtained by the two different ultrasound transducers were compared. The scores for images obtained by the PureWave Crystal transducer were significant higher than those by a conventional transducer, among all 10 structures examined. The new transducer was rated to enable higher diagnostic confidence (82.9%), and produced better image quality for the near field image (94.3%), the far field image (88.6%) and overall (94.3%). Ultrasound transducer incorporating the PureWave Crystal technology produces significantly better image quality for diagnostic purpose in difficult obstetric patients.

  1. Basics of biomedical ultrasound for engineers

    CERN Document Server

    Azhari, Haim

    2010-01-01

    "Basics of Biomedical Ultrasound for Engineers is a structured textbook for university engineering courses in biomedical ultrasound and for researchers in the field. This book offers a tool for building a solid understanding of biomedical ultrasound, and leads the novice through the field in a step-by-step manner. The book begins with the most basic definitions of waves, proceeds to ultrasounds in fluids, and then delves into solid ultrasounds, the most complicated kind of ultrasound. It encompasses a wide range of topics within biomedical ultrasound, from conceptual definitions of waves to the intricacies of focusing devices, transducers, and acoustic fields"--Provided by publisher.

  2. A Microscopic Convexity Principle for Spacetime Convex Solutions of Fully Nonlinear Parabolic Equations

    Institute of Scientific and Technical Information of China (English)

    Chuan Qiang CHEN; Bo Wen HU

    2013-01-01

    We study microscopic spacetime convexity properties of fully nonlinear parabolic partial differential equations.Under certain general structure condition,we establish a constant rank theorem for the spacetime convex solutions of fully nonlinear parabolic equations.At last,we consider the parabolic convexity of solutions to parabolic equations and the convexity of the spacetime second fundamental form of geometric flows.

  3. Revisiting separation properties of convex fuzzy sets

    Science.gov (United States)

    Separation of convex sets by hyperplanes has been extensively studied on crisp sets. In a seminal paper separability and convexity are investigated, however there is a flaw on the definition of degree of separation. We revisited separation on convex fuzzy sets that have level-wise (crisp) disjointne...

  4. A Note on Permutationally Convex Games

    NARCIS (Netherlands)

    van Velzen, S.; Hamers, H.J.M.; Norde, H.W.

    2005-01-01

    In this paper we generalise marginal vectors and permutational convexity.We show that if a game is generalised permutationally convex, then the corresponding generalised marginal vector is a core element.Furthermore we refine the concept of permutational convexity and show that this refinement yield

  5. On Uniform Convexity of Banach Spaces

    Institute of Scientific and Technical Information of China (English)

    Qing Jin CHENG; Bo WANG; Cui Ling WANG

    2011-01-01

    This paper gives some relations and properties of several kinds of generalized convexity in Banach spaces. As a result, it proves that every kind of uniform convexity implies the Banach-Sakes property, and several notions of uniform convexity in literature are actually equivalent.

  6. Computing farthest neighbors on a convex polytope

    NARCIS (Netherlands)

    Cheong, O.; Shin, C.S.; Vigneron, A.

    2002-01-01

    Let N be a set of n points in convex position in R3. The farthest-point Voronoi diagram of N partitions R³ into n convex cells. We consider the intersection G(N) of the diagram with the boundary of the convex hull of N. We give an algorithm that computes an implicit representation of G(N) in expecte

  7. Computing farthest neighbors on a convex polytope

    NARCIS (Netherlands)

    Cheong, O.; Shin, C.S.; Vigneron, A.

    2002-01-01

    Let N be a set of n points in convex position in R3. The farthest-point Voronoi diagram of N partitions R³ into n convex cells. We consider the intersection G(N) of the diagram with the boundary of the convex hull of N. We give an algorithm that computes an implicit representation of G(N) in

  8. Generalized geometrically convex functions and inequalities.

    Science.gov (United States)

    Noor, Muhammad Aslam; Noor, Khalida Inayat; Safdar, Farhat

    2017-01-01

    In this paper, we introduce and study a new class of generalized functions, called generalized geometrically convex functions. We establish several basic inequalities related to generalized geometrically convex functions. We also derive several new inequalities of the Hermite-Hadamard type for generalized geometrically convex functions. Several special cases are discussed, which can be deduced from our main results.

  9. Firey linear combinations of convex bodies

    Institute of Scientific and Technical Information of China (English)

    XIONG Ge; XIAO Qi-ming; CHEUNG Wing-Sum

    2009-01-01

    For convex bodies, the Firey linear combinations were introduced and studied in several papers. In this paper the mean width of the Firey linear combinations of convex bodies is studied, and the lower bound of the mean width of the Firey linear combinations of convex body and its polar body is given.

  10. General Ultrasound Imaging

    Medline Plus

    Full Text Available ... and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through ... during a single exam. The transducer sends out high-frequency sound waves (that the human ear cannot hear) ...

  11. Safety Issues for HIFU Transducer Design

    Science.gov (United States)

    Fleury, Gérard; Berriet, Rémi; Chapelon, Jean Yves; ter Haar, Gail; Lafon, Cyril; Le Baron, Olivier; Chupin, Laurent; Pichonnat, Fabrice; Lenormand, Jérôme

    2005-03-01

    In contrast with most ultrasound modalities for medical applications, (especially ultrasound imaging), High Intensity Focused Ultrasound (HIFU) involves technologies and procedures which may present risk to the patient. These risks, resulting from the high power levels required for effective therapy, should be taken into account at the earliest stages in the design of a system dedicated to HIFU treatment. An understanding of these risks must thus be shared amongst the many players in the field of therapy using high power ultrasound. Moreover, since the number of applications of HIFU has increased appreciably over recent years and the technology is ready to move from the research to the industrial level, it is worth now considering solutions that should be put in place to guarantee the safety of the patient during HIFU treatment. This paper reports thoughts on this, identifies some risks to the patient that must be taken into consideration in the design of HIFU transducers, and proposes some solutions that could prevent the deleterious consequences of transducer misuse or failure. For the main risks identified, such as exceeding the desired acoustic power or poor control of tissue targeting, a description of transducer performance that could potentially result in problems is systematically sought. This allows proposals for precautions to be taken during operation to be made. Parameters which should be monitored to ensure safe use are also suggested. This type of approach, which should be undertaken for the different components of a therapeutic system, highlights the challenges that must be faced in the immediate future for the development and safe exploitation of HIFU systems. The necessity for standard definitions of the parameters to be checked or monitored during HIFU treatments is crucial in this approach, as is the availability of reliable dedicated measurement devices. Co-ordinated action on these topics in the HIFU community would contribute to the

  12. Handbook of force transducers

    CERN Document Server

    Stefanescu, Dan Mihai

    2011-01-01

    Part I introduces the basic ""Principles and Methods of Force Measurement"" acording to a classification into a dozen of force transducers types: resistive, inductive, capacitive, piezoelectric, electromagnetic, electrodynamic, magnetoelastic, galvanomagnetic (Hall-effect), vibrating wires, (micro)resonators, acoustic and gyroscopic. Two special chapters refer to force balance techniques and to combined methods in force measurement. Part II discusses the ""(Strain Gauge) Force Transducers Components"", evolving from the classical force transducer to the digital / intelligent one, with the inco

  13. Gas speed flow transducer

    Directory of Open Access Journals (Sweden)

    Godovaniouk V. N.

    2011-08-01

    Full Text Available The design of a gas speed flow transducer using the coupling of gas speed and heat streams within the transducer itself is proposed. To maintain the heat balance between two thermoresistors under gas stream at different temperatures, it provides energy consumption monitoring. The detailed combined planar technology for the transducer production is presented. The worked-out measurement procedure allows to make measurements in the temperature range. Information enough to organize production of cheap, reliable and precise gas speed flow transducers is given.

  14. Driving electrostatic transducers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    Electrostatic transducers represent a very interesting alternative to the traditional inefficient electrodynamic transducers. In order to establish the full potential of these transducers, power amplifiers which fulfill the strict requirements imposed by such loads (high impedance, frequency...... depended, nonlinear and high bias voltage for linearization) must be developed. This paper analyzes power stages and bias configurations suitable for driving an electrostatic transducer. Measurement results of a 300 V prototype amplifier are shown. Measuring THD across a high impedance source is discussed......, and a high voltage attenuation interface for an audio analyzer is presented. THD below 0:1% is reported....

  15. A noncommutative convexity in C*-bimodules

    Directory of Open Access Journals (Sweden)

    Mohsen Kian

    2017-02-01

    Full Text Available Let A and B be C*-algebras. We consider a noncommutative convexity in Hilbert A-B-bimodules, called A-B-convexity, as a generalization of C*-convexity in C*-algebras. We show that if X is a Hilbert A-B-bimodule, then Mn(X is a Hilbert Mn(A-Mn(B-bimodule and apply it to show that the closed unit ball of every Hilbert A-B-bimodule is A-B-convex. Some properties of this kind of convexity and various examples have been given.

  16. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... specific content. Related Articles and Media Sonohysterography Ultrasound - Abdomen Children's (Pediatric) Ultrasound - Abdomen Obstetric Ultrasound Ultrasound - Prostate Kidney and ...

  17. Detailed EFSUM recommendations on the scope of ultrasound assessment in patients with portal hypertension considering the diagnostic reference level

    Directory of Open Access Journals (Sweden)

    Andrzej Smereczyński

    2017-06-01

    Full Text Available An important paper describing the Standards of the Polish Ultrasound Society regarding the assessment of portal and hepatic vasculature was published in the Journal of Ultrasonography. Due to the multiplicity of morphological and hemodynamic data required, the time needed to obtain these data and the legal responsibility of doctors for the results, there seems to be a need to determine a clear range of the assessed parameters depending on the reference level of a given healthcare facility. Therefore, the aim of the paper was to present the EFSUMB recommendations on the range of the evaluated ultrasonographic parameters in portal hypertension depending on the reference level. European healthcare institutions are characterized by a clear three-level reference network. Due to the lack of a similar division in Poland, we propose our own classification of the competence of medical entities. The first reference level: ultrasound assessments in a primary health care setting (performed by GPs, emergency physicians, non-specialist private practice physicians, non-specialist practice physicians; at least one mid-class ultrasound scanner with pulsed and color Doppler options, equipped with convex 3–5 MHz and linear 7–12 MHz transducers should be available at physician’s disposal. The second reference level: ultrasound assessments in the hospital setting and specialist outpatient clinics, performed by specialist private practice physicians, radiologists, gastroenterologists and hepatologists; top class (premium digital ultrasound scanner should be available at physician’s disposal. Third reference level: ultrasound assessments performed in gastroenterology, hepatology and liver surgery departments as well as their specialist outpatient clinics; physicians should use top class digital ultrasound equipment. At every reference level, physicians performing abdominal ultrasound should have the appropriate certification to perform such an assessment or

  18. Evaluating convex roof entanglement measures.

    Science.gov (United States)

    Tóth, Géza; Moroder, Tobias; Gühne, Otfried

    2015-04-24

    We show a powerful method to compute entanglement measures based on convex roof constructions. In particular, our method is applicable to measures that, for pure states, can be written as low order polynomials of operator expectation values. We show how to compute the linear entropy of entanglement, the linear entanglement of assistance, and a bound on the dimension of the entanglement for bipartite systems. We discuss how to obtain the convex roof of the three-tangle for three-qubit states. We also show how to calculate the linear entropy of entanglement and the quantum Fisher information based on partial information or device independent information. We demonstrate the usefulness of our method by concrete examples.

  19. Ultrasound cleaning of microfilters

    DEFF Research Database (Denmark)

    Hald, Jens; Bjørnø, Irina; Jensen, Leif Bjørnø

    1999-01-01

    The aim of the present work is to develop, design, and manufacture a high-power ultrasound transducer module to be used for preventing the blocking of plastic-based microfilters by organic materials, and possibly to prolong the lifetime of the filters in industry using the cavitation on the surface...... suitable for cleaning of microfilters without damaging the filter structure. The filter surface was studied using an optical microscope before and after the experiment. When high-power ultrasound (max. 75 W/cm2) was applied to the surface of some microfilters, no visible damage was found, while others...... filters were damaged. The results of the laboratory experiments formed background for the final design of an ultrasound transducer module for use by foodstuff filtration plants. [This work was financed by the EU Project WAMBIO PL96-3257 (FAIR Programme).]...

  20. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.

    Science.gov (United States)

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K Kirk

    2011-02-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  1. Convex Hulls of Algebraic Sets

    CERN Document Server

    Gouveia, João

    2010-01-01

    This article describes a method to compute successive convex approximations of the convex hull of a set of points in R^n that are the solutions to a system of polynomial equations over the reals. The method relies on sums of squares of polynomials and the dual theory of moment matrices. The main feature of the technique is that all computations are done modulo the ideal generated by the polynomials defining the set to the convexified. This work was motivated by questions raised by Lov\\'asz concerning extensions of the theta body of a graph to arbitrary real algebraic varieties, and hence the relaxations described here are called theta bodies. The convexification process can be seen as an incarnation of Lasserre's hierarchy of convex relaxations of a semialgebraic set in R^n. When the defining ideal is real radical the results become especially nice. We provide several examples of the method and discuss convergence issues. Finite convergence, especially after the first step of the method, can be described expl...

  2. An Inexpensive Position Transducer.

    Science.gov (United States)

    Fox, J.; And Others

    1989-01-01

    Described is a position transducer used to convert the position of an object into a voltage read by a computer with use of an interface board. The arrangement of the apparatus, electronic circuit, and typical graph displays are presented. Discussed is the instructional use of the transducer. (YP)

  3. ROLE OF ULTRASOUND IN EVALUATION OF RETROPERITONEAL LESIONS

    Directory of Open Access Journals (Sweden)

    Harshita Pant

    2016-07-01

    Full Text Available BACKGROUND The retroperitoneum contains the adrenals, kidneys and ureters, the duodenal loop, pancreas, great vessels with their branches and associated lymph node chains, ascending and descending portions of the colon including the caecum, the retroperitoneal sonographic images are frequently degraded by bowel gas, thick muscles, fat, ribs, the lower lungs. AIMS AND OBJECTIVES To study the various features of retroperitoneal lesions by ultrasonography and assess its role. MATERIALS AND METHODS Fifty patients presenting with signs and symptoms suggestive of retroperitoneal pathology were evaluated over a period of 12 months using machine Siemens Sonoline Omnia/Siemens Sonoline G50 with 3.5 MHz convex and 5-10 MHz multifrequency linear transducer. OBSERVATIONS The maximum numbers of cases–17 (34% were of renal origin. This was followed by pancreatic lesion - 14 cases (28%, USG correctly detected 46 out of 50 cases thus having an accuracy of 92% for the detection and evaluation of retroperitoneal lesions. CONCLUSIONS Ultrasound provides a safe, quick, reliable, non-invasive and cost effective tool for screening for retroperitoneum. We recommend ultrasound as the primary diagnostic tool for various retroperitoneal lesions.

  4. Triple-resonant transducers.

    Science.gov (United States)

    Butler, Stephen C

    2012-06-01

    A detailed analysis is presented of two novel multiple-resonant transducers which produce a wider transmit response than that of a conventional Tonpilz-type transducer. These multi-resonant transducers are Tonpilz-type longitudinal vibrators that produce three coupled resonances and are referred to as triple-resonant transducers (TRTs). One of these designs is a mechanical series arrangement of a tail mass, piezoelectric ceramic stack, central mass, compliant spring, second central mass, second compliant spring, and a piston-radiating head mass. The other TRT design is a mechanical series arrangement of a tail mass, piezoelectric ceramic stack, central mass, compliant spring, and head mass with a quarter-wave matching layer of poly(methyl methacrylate) on the head mass. Several prototype transducer element designs were fabricated that demonstrated proof-of-concept.

  5. Programming macro tree transducers

    DEFF Research Database (Denmark)

    Bahr, Patrick; Day, Laurence E.

    2013-01-01

    A tree transducer is a set of mutually recursive functions transforming an input tree into an output tree. Macro tree transducers extend this recursion scheme by allowing each function to be defined in terms of an arbitrary number of accumulation parameters. In this paper, we show how macro tree...... transducers can be concisely represented in Haskell, and demonstrate the benefits of utilising such an approach with a number of examples. In particular, tree transducers afford a modular programming style as they can be easily composed and manipulated. Our Haskell representation generalises the original...... definition of (macro) tree transducers, abolishing a restriction on finite state spaces. However, as we demonstrate, this generalisation does not affect compositionality....

  6. Programming macro tree transducers

    DEFF Research Database (Denmark)

    Bahr, Patrick; Day, Laurence E.

    2013-01-01

    A tree transducer is a set of mutually recursive functions transforming an input tree into an output tree. Macro tree transducers extend this recursion scheme by allowing each function to be defined in terms of an arbitrary number of accumulation parameters. In this paper, we show how macro tree...... transducers can be concisely represented in Haskell, and demonstrate the benefits of utilising such an approach with a number of examples. In particular, tree transducers afford a modular programming style as they can be easily composed and manipulated. Our Haskell representation generalises the original...... definition of (macro) tree transducers, abolishing a restriction on finite state spaces. However, as we demonstrate, this generalisation does not affect compositionality....

  7. Acoustic window planning for ultrasound acquisition.

    Science.gov (United States)

    Göbl, Rüdiger; Virga, Salvatore; Rackerseder, Julia; Frisch, Benjamin; Navab, Nassir; Hennersperger, Christoph

    2017-03-11

    Autonomous robotic ultrasound has recently gained considerable interest, especially for collaborative applications. Existing methods for acquisition trajectory planning are solely based on geometrical considerations, such as the pose of the transducer with respect to the patient surface.

  8. Combined photoacoustic and ultrasound biomicroscopy.

    Science.gov (United States)

    Harrison, Tyler; Ranasinghesagara, Janaka C; Lu, Huihong; Mathewson, Kory; Walsh, Andrew; Zemp, Roger J

    2009-11-23

    We report on the development of an imaging system capable of combined ultrasound and photoacoustic imaging based on a fast-scanning single-element 25-MHz ultrasound transducer and a unique light-delivery system. The system is capable of 20 ultrasound frames per second and slower photoacoustic frame rates limited by laser pulse-repetition rates. Laser and ultrasound pulses are interlaced for co-registration of photoacoustic and ultrasound images. In vivo imaging of a human finger permits ultrasonic visualization of vessel structures and speckle changes indicative of blood flow, while overlaid photoacoustic images highlight some small vessels that are not clear from the ultrasound scan. Photoacoustic images provide optical absorption contrast co-registered in the structural and blood-flow context of ultrasound with high-spatial resolution and may prove important for clinical diagnostics and basic science of the microvasculature.

  9. Tunable-angle wedge transducer for improved acoustophoretic control in a microfluidic chip

    DEFF Research Database (Denmark)

    Iranmanesh, I.; Barnkob, Rune; Bruus, Henrik;

    2013-01-01

    coupling angle, and transducer actuation method (single-frequency actuation or frequency-modulation actuation). The energy-density analysis is based on measuring the transmitted light intensity through a microfluidic channel filled with a suspension of 5 µm diameter beads and the results with the tunable...... uniform particle patterns with average acoustic energy densities comparable to those obtained using single-frequency actuation.......We present a tunable-angle wedge ultrasound transducer for improved control of microparticle acoustophoresis in a microfluidic chip. The transducer is investigated by analyzing the pattern of aligned particles and induced acoustic energy density while varying the transducer geometry, transducer...

  10. Obstetrical Ultrasound

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Obstetric Ultrasound Obstetric ultrasound uses sound waves to produce pictures ... limitations of Obstetrical Ultrasound Imaging? What is Obstetrical Ultrasound Imaging? Ultrasound is safe and painless, and produces ...

  11. Prostate Ultrasound

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Ultrasound - Prostate Ultrasound of the prostate uses sound waves ... the limitations of Prostate Ultrasound Imaging? What is Ultrasound Imaging of the Prostate? Ultrasound is safe and ...

  12. Musculoskeletal Ultrasound

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Ultrasound - Musculoskeletal Ultrasound imaging uses sound waves to produce ... Ultrasound Imaging of the Musculoskeletal System? What is Ultrasound Imaging of the Musculoskeletal System? Ultrasound is safe ...

  13. Ultrasound - Scrotum

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Ultrasound - Scrotum Ultrasound imaging of the scrotum uses sound ... of Ultrasound Imaging of the Scrotum? What is Ultrasound Imaging of the Scrotum? Ultrasound imaging of the ...

  14. Ultrasound -- Vascular

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Ultrasound - Vascular Vascular ultrasound uses sound waves to evaluate ... the limitations of Vascular Ultrasound? What is Vascular Ultrasound? Ultrasound is safe and painless, and produces pictures ...

  15. Hip Ultrasound

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Hip Ultrasound Hip ultrasound uses sound waves to produce pictures ... of Ultrasound Imaging of the Hip? What is Ultrasound Imaging of the Hip? Ultrasound images of the ...

  16. Ultrasound -- Vascular

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Ultrasound - Vascular Vascular ultrasound uses sound waves to evaluate the ... are the limitations of Vascular Ultrasound? What is Vascular Ultrasound? Ultrasound is safe and painless, and produces ...

  17. PMN-PT single crystal focusing transducer fabricated using a mechanical dimpling technique.

    Science.gov (United States)

    Lam, K H; Chen, Y; Cheung, K F; Dai, J Y

    2012-01-01

    A ∼5MHz focusing PMN-PT single crystal ultrasound transducer has been fabricated utilizing a mechanical dimpling technique, where the dimpled crystal wafer was used as an active element of the focusing transducer. For the dimpled focusing transducer, the effective electromechanical coupling coefficient was enhanced significantly from 0.42 to 0.56. The dimpled transducer also yields a -6dB bandwidth of 63.5% which is almost double the bandwidth of the plane transducer. An insertion loss of the dimpled transducer (-18.1dB) is much lower than that of the plane transducer. Finite element simulation also reveals specific focused beam from concave crystal surface. These promising results show that the dimpling technique can be used to develop high-resolution focusing single crystal transducers.

  18. Use of Convexity in Ostomy Care

    Science.gov (United States)

    Salvadalena, Ginger; Pridham, Sue; Droste, Werner; McNichol, Laurie; Gray, Mikel

    2017-01-01

    Ostomy skin barriers that incorporate a convexity feature have been available in the marketplace for decades, but limited resources are available to guide clinicians in selection and use of convex products. Given the widespread use of convexity, and the need to provide practical guidelines for appropriate use of pouching systems with convex features, an international consensus panel was convened to provide consensus-based guidance for this aspect of ostomy practice. Panelists were provided with a summary of relevant literature in advance of the meeting; these articles were used to generate and reach consensus on 26 statements during a 1-day meeting. Consensus was achieved when 80% of panelists agreed on a statement using an anonymous electronic response system. The 26 statements provide guidance for convex product characteristics, patient assessment, convexity use, and outcomes. PMID:28002174

  19. CONVEX CLASS OF STARLIKE FUNCTIONS

    OpenAIRE

    Gupta, V. P.

    1984-01-01

    Let $S$ denote the class of functions of the form $f(z)=z-¥sum_{n=2}^{¥infty}|a_{n}|z^{n}$ that are analytic and univalent in the unit disk $U$. Let $S(¥alpha, ¥beta)$ and $K(¥alpha, ¥beta)$ denote the subclasses of $S$ consisting respectively, of starlike and close-to-convex functions of order $¥alpha(0¥leqq¥alpha

  20. Finite dimensional convexity and optimization

    CERN Document Server

    Florenzano, Monique

    2001-01-01

    The primary aim of this book is to present notions of convex analysis which constitute the basic underlying structure of argumentation in economic theory and which are common to optimization problems encountered in many applications. The intended readers are graduate students, and specialists of mathematical programming whose research fields are applied mathematics and economics. The text consists of a systematic development in eight chapters, with guided exercises containing sometimes significant and useful additional results. The book is appropriate as a class text, or for self-study.

  1. Compact Transducers and Arrays

    Science.gov (United States)

    2005-05-01

    Soc. Am., 104, pp.64-71 44 25.Decarpigny, J.N., J.C. Debus, B. Tocquet & D. Boucher. 1985. "In-Air Analysis Of Piezoelectric Tonpilz Transducers In A... Transducers and Arrays Final Report May 2005 Contacts: Dr. Robert E. Newnham The Pennsylvania State University, 251 MRL, University Park, PA 16802 phone...814) 865-1612 fax: (814) 865-2326 email: ....c xx.....i.i.....ht.. .u a.p.u..c.e.du. Dr. Richard J. Meyer, Jr. Systems Engineering ( Transducers ), ARL

  2. Design and development of a multi-hole broadband-based ultrasonic transducer.

    Science.gov (United States)

    Dong, Hui-juan; Wu, Jian; Zhang, He; Zhang, Guang-yu

    2011-03-01

    In order to improve the efficiency of ultrasonic energy transformed from electricity for an ultrasonic transducer array, a novel 1/2 wavelength multi-hole broadband-based transducer was designed, developed and evaluated. The low equivalent mass of the transducer is realized in this work through drilling holes on the output end of the horn. In comparison with a traditional transducer, the developed transducer has demonstrated a lower mechanical quality coefficient and a wider broadband. As a result, an ultrasound treatment system for crude oil has been developed based on the new transducer design. Furthermore, we have demonstrated the effectiveness of the ultrasound treatment system on viscosity reduction of crude oil and paraffin.

  3. Uniformly convex subsets of the Hilbert space with modulus of convexity of the second order

    OpenAIRE

    Balashov, Maxim V.; Repovš, Dušan,

    2011-01-01

    We prove that in the Hilbert space every uniformly convex set with modulus of convexity of the second order at zero is an intersection of closed balls of fixed radius. We also obtain an estimate of this radius.

  4. Various Expressions for Modulus of Random Convexity

    Institute of Scientific and Technical Information of China (English)

    Xiao Lin ZENG

    2013-01-01

    We first prove various kinds of expressions for modulus of random convexity by using an Lo(F,R)-valued function's intermediate value theorem and the well known Hahn-Banach theorem for almost surely bounded random linear functionals,then establish some basic properties including continuity for modulus of random convexity.In particular,we express the modulus of random convexity of a special random normed module Lo(F,X) derived from a normed space X by the classical modulus of convexity of X.

  5. Pressure Transducer Locations

    Data.gov (United States)

    National Aeronautics and Space Administration — Files are located here, defining the locations of the pressure transducers on the HIRENASD model. These locations also correspond to the locations that analysts...

  6. Ultrasound transmission attenuation tomography using energy-scaled amplitude ratios

    Science.gov (United States)

    Chen, Ting; Shin, Junseob; Huang, Lianjie

    2016-04-01

    Ultrasound attenuation of breast tumors is related to their types and pathological states, and can be used to detect and characterize breast cancer. Particularly, ultrasound scattering attenuation can infer the margin properties of breast tumors. Ultrasound attenuation tomography quantitatively reconstructs the attenuation properties of the breast. Our synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays records both ultrasound reflection and transmission signals. We develop an ultrasound attenuation tomography method using ultrasound energy-scaled amplitude decays of ultrasound transmission signals and conduct ultrasound attenuation tomography using a known sound-speed model. We apply our ultrasound transmission attenuation tomography method to a breast phantom dataset, and compare the ultrasound attenuation tomography results with conventional beamforming ultrasound images obtained using reflection signals. We show that ultrasound transmission attenuation tomography complements beamforming images in identifying breast lesions.

  7. A transesophageal phased array transducer for ultrasonic imaging of the heart

    NARCIS (Netherlands)

    C.T. Lancée (Charles)

    1987-01-01

    textabstractIn this thesis the development of a miniaturized phased array ultrasound transducer is described. The application of this transducer in the field of echocardiology is devoted to transesophageal cross-sectional scanning of the heart and its great vessels. The enormous increase in diagnost

  8. A transesophageal phased array transducer for ultrasonic imaging of the heart

    NARCIS (Netherlands)

    C.T. Lancée (Charles)

    1987-01-01

    textabstractIn this thesis the development of a miniaturized phased array ultrasound transducer is described. The application of this transducer in the field of echocardiology is devoted to transesophageal cross-sectional scanning of the heart and its great vessels. The enormous increase in

  9. Synthetic Aperture Focusing for a Single Element Transducer undergoing Helix Motion

    DEFF Research Database (Denmark)

    Andresen, Henrik; Nikolov, Svetoslav Ivanov; Jensen, Jørgen Arendt

    2011-01-01

    This paper describes the application of 3D synthetic aperture focusing (SAF) to a single element trans-rectal ultrasound transducer. The transducer samples a 3D volume by simultaneous rotation and translation giving a helix motion. Two different 3D SAF methods are investigated, a direct and a two...

  10. DIFFERENTIABILITY OF CONVEX FUNCTIONS ON SUBLINEAR TOPOLOGICAL SPACES AND VARIATIONAL PRINCIPLES IN LOCALLY CONVEX SPACES

    Institute of Scientific and Technical Information of China (English)

    CHENG LIXIN; TENG YANMEI

    2005-01-01

    This paper presents a type of variational principles for real valued w* lower semicon tinuous functions on certain subsets in duals of locally convex spaces, and resolve a problem concerning differentiability of convex functions on general Banach spaces. They are done through discussing differentiability of convex functions on nonlinear topological spaces and convexification of nonconvex functions on topological linear spaces.

  11. A simple view on convex analysis and its applications

    NARCIS (Netherlands)

    J. Brinkhuis (Jan); V. Tikhomirov

    2005-01-01

    textabstractOur aim is to give a simple view on the basics and applications of convex analysis. The essential feature of this account is the systematic use of the possibility to associate to each convex object---such as a convex set, a convex function or a convex extremal problem--- a cone, without

  12. Entropy coherent and entropy convex measures of risk

    NARCIS (Netherlands)

    Laeven, R.J.A.; Stadje, M.

    2013-01-01

    We introduce two subclasses of convex measures of risk, referred to as entropy coherent and entropy convex measures of risk. Entropy coherent and entropy convex measures of risk are special cases of φ-coherent and φ-convex measures of risk. Contrary to the classical use of coherent and convex measur

  13. Studies of the source complex behaviour and of the ultrasound radiation of contact flexible multi-element transducers; Etudes du comportement complexe de source et du rayonnement ultrasonore des traducteurs multi-elements flexibles au contact

    Energy Technology Data Exchange (ETDEWEB)

    Amory, V

    2007-12-15

    This work deals with the ultrasonic nondestructive testing of parts with complex geometries using soft multi-element sensors. The different types of contact control configurations are presented first. Then, the difficulties encountered with conventional contact transducers are explained and the multi-element piezoelectric transducers technology, developed to meet these difficulties, is presented. The second chapter presents the results of finite-element calculations showing the complexity of a transducer in a condition of testing utilization. In a same configuration, the radiated far field calculated by finite-elements is compared to the measurement in order to validate the way the source behaviour is calculated. However, despite the efficiency of the finite-elements simulation, this tool is numerically too costly and cannot be used to optimize a full multi-element transducer. Therefore, a realistic source model is built and implemented in a radiation code based on high-frequency asymptotic approximations where only L and T volume waves are calculated. The incapacity of this model to reproduce the behaviour of T waves in some directions of propagation has led to give a particular attention to the fore-waves, neglected in the radiation calculation. Chapter 3 treats of the building of an exact radiation model taking into consideration the fore-waves contribution emitted by a contact transducer exerting a random space-time distribution constraint at the surface of the considered medium. A radiation model, based on the calculation of exact Green functions of the Lamb problem is proposed. The exact model is particularly interesting in the case of sensor geometries with a long length with respect to other dimensions (2D case). Field calculation results are shown for an element of the matrix network (3D case) and for a linear element (2D case). A study of different existing approached models is carried out as well. The last chapter presents some results of the field

  14. Rocking convex array used for 3D synthetic aperture focusing

    DEFF Research Database (Denmark)

    Andresen, Henrik; Nikolov, Svetoslav; Pedersen, M M

    2008-01-01

    Volumetric imaging can be performed using 1D arrays in combination with mechanical motion. Outside the elevation focus of the array, the resolution and contrast quickly degrade compared to the azimuth plane, because of the fixed transducer focus. The purpose of this paper is to use synthetic...... aperture focusing (SAF) for enhancing the elevation focusing for a convex rocking array, to obtain a more isotropic point spread function. This paper presents further development of the SAF method, which can be used with curved array combined with a rocking motion. The method uses a virtual source (VS...... Kretztechnik, Zipf, Austria). The array has an elevation focus at 60 mm of depth, and the angular rocking velocity is up to 140deg/s. The scan sequence uses an fprf of 4500 - 7000 Hz allowing up to 15 cm of penetration. The full width at half max (FWHM) and main-lobe to side-lobe ratio (MLSL) is used...

  15. In-vivo evaluation of convex array synthetic aperture imaging

    DEFF Research Database (Denmark)

    Pedersen, Morten Høgholm; Gammelmark, Kim Løkke; Jensen, Jørgen Arendt

    2007-01-01

    This paper presents an in-vivo study of synthetic transmit aperture (STA) imaging in comparison to conventional imaging, evaluating whether STA imaging is feasible in-vivo, and whether the image quality obtained is comparable to traditional scanned imaging in terms of penetration depth, spatial...... resolution, contrast resolution, and artifacts. Acquisition was performed using our research scanner RASMUS and a 5.5 MHz convex array transducer. STA imaging was acquired using circular wave emulation by 33-element subapertures and a 20 us linear FM signal as excitation pulse. For conventional imaging a 64...... element aperture was used in transmit and receive with a 1.5 cycle sinusoid excitation pulse. Conventional and STA images were acquired interleaved ensuring that the exact same anatomical location was scanned. Image sequences were recorded in real-time and processed off-line. Seven male volunteers were...

  16. Thyroid and parathyroid ultrasound.

    Science.gov (United States)

    Ghervan, Cristina

    2011-03-01

    Thyroid ultrasound is easy to perform due to the superficial location of the thyroid gland, but appropriate equipment is mandatory with a linear high frequency transducer (7.5 - 12) MHz. Some pathological aspects of the thyroid gland are easily diagnosed by ultrasound, like the enlargement of the thyroid volume (goiter) or the presence of nodules and cysts; while other aspects are more difficult and need more experience (diffuse changes in the structure, echogenicity and vascularization of the parenchyma, differential diagnosis of malignant nodules). Ultrasound has become the diagnostic procedure of choice in guidelines for the management of thyroid nodules; most structural abnormalities of the thyroid need evaluation and monitoring but not intervention. A good knowledge of the normal appearance of the thyroid gland is compulsory for an accurate ultrasound diagnosis.

  17. Thermal dispersion method for an ultrasonic phased-array transducer

    Science.gov (United States)

    Choi, Euna; Lee, Wonseok; Roh, Yongrae

    2016-07-01

    When the driving voltage of an ultrasonic transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer, which can burn the patient’s skin and degrade transducer performance. In this study, the method to disperse the heat inside an ultrasonic phased-array transducer has been examined. The mechanism of temperature rise due to heat generation inside the transducer was investigated by numerical analysis and the effects of the thermal properties of the components of the transducer such as specific heat and thermal conductivity on the temperature rise were analyzed. On the basis of the results, a heat-dispersive structure was devised to reduce the temperature at the surface of the acoustic lens of the transducer. Prototype transducers were fabricated to check the efficacy of the heat-dispersive structure. By experiments, we have confirmed that the new heat-dispersive structure can reduce the internal temperature by as much as 50% in comparison with the conventional structure, which confirms the validity of the thermal dispersion mechanism developed in this work.

  18. Metal cap flexural transducers for air-coupled ultrasonics

    Science.gov (United States)

    Eriksson, T. J. R.; Dixon, S.; Ramadas, S. N.

    2015-03-01

    Ultrasonic generation and detection in fluids is inefficient due to the large difference in acoustic impedance between the piezoelectric element and the propagation medium, leading to large internal reflections and energy loss. One way of addressing the problem is to use a flexural transducer, which uses the bending modes in a thin plate or membrane. As the plate bends, it displaces the medium in front of it, hence producing sound waves. A piezoelectric flexural transducer can generate large amplitude displacements in fluid media for relatively low excitation voltages. Commercially available flexural transducers for air applications operate at 40 kHz, but there exists ultrasound applications that require significantly higher frequencies, e.g. flow measurements. Relatively little work has been done to date to understand the underlying physics of the flexural transducer, and hence how to design it to have specific properties suitable for particular applications. This paper investigates the potential of the flexural transducer and its operating principles. Two types of actuation methods are considerd: piezoelectric and electrodynamic. The piezoelectrically actuated transducer is more energy efficient and intrinsically safe, but the electrodynamic transducer has the advantage of being less sensitive to high temperature environments. The theory of vibrating plates is used to predict transducer frequency in addition to front face amplitude, which shows good correlation with experimental results.

  19. Efficient Line Searching for Convex Functions

    NARCIS (Netherlands)

    den Boef, E.; den Hertog, D.

    2004-01-01

    In this paper we propose two new line search methods for convex functions. These new methods exploit the convexity property of the function, contrary to existing methods.The worst method is an improved version of the golden section method.For the second method it is proven that after two evaluations

  20. Introduction to Convex and Quasiconvex Analysis

    NARCIS (Netherlands)

    J.B.G. Frenk (Hans); G. Kassay

    2004-01-01

    textabstractIn the first chapter of this book the basic results within convex and quasiconvex analysis are presented. In Section 2 we consider in detail the algebraic and topological properties of convex sets within Rn together with their primal and dual representations. In Section 3 we apply the re

  1. Stochastic Dominance: Convexity and Some Efficiency Tests

    NARCIS (Netherlands)

    A.M. Lizyayev (Andrey)

    2009-01-01

    textabstractThis paper points out the importance of Stochastic Dominance (SD) efficient sets being convex. We review classic convexity and efficient set characterization results on SD efficiency of a given portfolio relative to a diversified set of assets and generalize them in the following

  2. Convex trace functions of several variables

    DEFF Research Database (Denmark)

    Hansen, Frank

    2002-01-01

    We prove that the function (x1,...,xk)¿Tr(f(x1,...,xk)), defined on k-tuples of symmetric matrices of order (n1,...,nk) in the domain of f, is convex for any convex function f of k variables. The matrix f(x1,...,xk) is defined by the functional calculus for functions of several variables, and it ...

  3. Polar DuaLs of Convex Bodies

    Science.gov (United States)

    1990-01-01

    to Convex Bodies, Geometriae Dedicata 2" (1973) 225-248. 10. H. Guggenheimer, "The Analytic Geometry of the Unsymmetric Minkowski Plane," Lecture...Mathematics, Vol. 58, No. 2, 1975. 19. E. Lutwak, "On Cross-Sectional Measures of Polar Reciprocal Convex Bodies," Geometriae Dedicata 5, (1976) 79-80

  4. Differential analysis of matrix convex functions II

    DEFF Research Database (Denmark)

    Hansen, Frank; Tomiyama, Jun

    2009-01-01

    We continue the analysis in [F. Hansen, and J. Tomiyama, Differential analysis of matrix convex functions. Linear Algebra Appl., 420:102--116, 2007] of matrix convex functions of a fixed order defined in a real interval by differential methods as opposed to the characterization in terms of divide...

  5. The Band around a Convex Body

    Science.gov (United States)

    Swanson, David

    2011-01-01

    We give elementary proofs of formulas for the area and perimeter of a planar convex body surrounded by a band of uniform thickness. The primary tool is a integral formula for the perimeter of a convex body which describes the perimeter in terms of the projections of the body onto lines in the plane.

  6. Strictly convex functions on complete Finsler manifolds

    Indian Academy of Sciences (India)

    YOE ITOKAWA; KATSUHIRO SHIOHAMA; BANKTESHWAR TIWARI

    2016-10-01

    The purpose of the present paper is to investigate the influence of strictly convex functions on the metric structures of complete Finsler manifolds. More precisely we discuss the properties of the group of isometries and the exponential maps on a complete Finsler manifold admitting strictly convex functions.

  7. Harmonic ultrasound imaging using synthetic aperture sequential beamforming

    DEFF Research Database (Denmark)

    2012-01-01

    A method includes generating an ultrasound image based on the harmonic components in the received echoes using multi-stage beam forming and data generated therefrom. An ultrasound imaging system (100, 200) includes a transducer array (108) including a plurality of transducer elements configured...... to emit ultrasound signals and receive echoes generated in response to the emitted ultrasound signals. The ultrasound imaging system further includes transmit circuitry (1 10) that generates a set of pulses that actuate a set of the plurality of transducer elements to emit ultrasound signals....... The ultrasound imaging system further includes receive circuitry (1 12), including a first beam former (122) configured to process the second harmonic signal components extracted from the received echo signals, generating intermediate scan lines. Memory (126) stores the generated intermediate scan lines...

  8. Method and system to synchronize acoustic therapy with ultrasound imaging

    Science.gov (United States)

    Owen, Neil (Inventor); Bailey, Michael R. (Inventor); Hossack, James (Inventor)

    2009-01-01

    Interference in ultrasound imaging when used in connection with high intensity focused ultrasound (HIFU) is avoided by employing a synchronization signal to control the HIFU signal. Unless the timing of the HIFU transducer is controlled, its output will substantially overwhelm the signal produced by ultrasound imaging system and obscure the image it produces. The synchronization signal employed to control the HIFU transducer is obtained without requiring modification of the ultrasound imaging system. Signals corresponding to scattered ultrasound imaging waves are collected using either the HIFU transducer or a dedicated receiver. A synchronization processor manipulates the scattered ultrasound imaging signals to achieve the synchronization signal, which is then used to control the HIFU bursts so as to substantially reduce or eliminate HIFU interference in the ultrasound image. The synchronization processor can alternatively be implemented using a computing device or an application-specific circuit.

  9. Thermal safety of vibro-acoustography using a confocal transducer.

    Science.gov (United States)

    Chen, Shigao; Aquino, Wilkins; Alizad, Azra; Urban, Matthew W; Kinnick, Randall; Greenleaf, James F; Fatemi, Mostafa

    2010-02-01

    Vibro-acoustography (VA) is an imaging method that forms a two-dimensional (2-D) image by moving two cofocused ultrasound beams with slightly different frequencies over the object in a C-scan format and recording acoustic emission from the focal region at the difference frequency. This article studies tissue heating due to a VA scan using a concentric confocal transducer. The three-dimensional (3-D) ultrasound intensity field calculated by Field II is used with the bio-heat equation to estimate tissue heating due to ultrasound absorption. Results calculated with thermal conduction and with blood perfusion, with conduction and without perfusion and without conduction and without perfusion are compared. Maximum heating due to ultrasound absorption occurs in the transducer's near-field and maximum temperature rise in soft tissue during a single VA scan is below 0.05 degrees C for all three attenuation coefficients evaluated: 0.3, 0.5 and 0.7 dB/cm/MHz. Transducer self-heating during a single VA scan measured by a thermocouple is less than 0.27 degrees C. 2010 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  10. Prostate Ultrasound

    Medline Plus

    Full Text Available ... through blood vessels. Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions. Prostate ultrasound, also called transrectal ultrasound, provides ...

  11. Toric geometry of convex quadrilaterals

    CERN Document Server

    Legendre, Eveline

    2009-01-01

    We provide an explicit resolution of the Abreu equation on convex labeled quadrilaterals. This confirms a conjecture of Donaldson in this particular case and implies a complete classification of the explicit toric K\\"ahler-Einstein and toric Sasaki-Einstein metrics constructed in [6,23,14]. As a byproduct, we obtain a wealth of extremal toric (complex) orbi-surfaces, including K\\"ahler-Einstein ones, and show that for a toric orbi-surface with 4 fixed points of the torus action, the vanishing of the Futaki invariant is a necessary and sufficient condition for the existence of K\\"ahler metric with constant scalar curvature. Our results also provide explicit examples of relative K-unstable toric orbi-surfaces that do not admit extremal metrics.

  12. Convex analysis and global optimization

    CERN Document Server

    Tuy, Hoang

    2016-01-01

    This book presents state-of-the-art results and methodologies in modern global optimization, and has been a staple reference for researchers, engineers, advanced students (also in applied mathematics), and practitioners in various fields of engineering. The second edition has been brought up to date and continues to develop a coherent and rigorous theory of deterministic global optimization, highlighting the essential role of convex analysis. The text has been revised and expanded to meet the needs of research, education, and applications for many years to come. Updates for this new edition include: · Discussion of modern approaches to minimax, fixed point, and equilibrium theorems, and to nonconvex optimization; · Increased focus on dealing more efficiently with ill-posed problems of global optimization, particularly those with hard constraints;

  13. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    The set of all surface tensors of a convex body K (Minkowski tensors derived from the surface area measure of K) determine K up to translation, and hereby, the surface tensors of K contain all information on the shape of K. Here, shape means the equivalence class of all convex bodies...... that are translates of each other. An algorithm for reconstructing an unknown convex body in R 2 from its surface tensors up to a certain rank is presented. Using the reconstruction algorithm, the shape of an unknown convex body can be approximated when only a finite number s of surface tensors are available....... The output of the reconstruction algorithm is a polytope P, where the surface tensors of P and K are identical up to rank s. We establish a stability result based on a generalization of Wirtinger’s inequality that shows that for large s, two convex bodies are close in shape when they have identical surface...

  14. Convex functions, monotone operators and differentiability

    CERN Document Server

    Phelps, Robert R

    1993-01-01

    The improved and expanded second edition contains expositions of some major results which have been obtained in the years since the 1st edition. Theaffirmative answer by Preiss of the decades old question of whether a Banachspace with an equivalent Gateaux differentiable norm is a weak Asplund space. The startlingly simple proof by Simons of Rockafellar's fundamental maximal monotonicity theorem for subdifferentials of convex functions. The exciting new version of the useful Borwein-Preiss smooth variational principle due to Godefroy, Deville and Zizler. The material is accessible to students who have had a course in Functional Analysis; indeed, the first edition has been used in numerous graduate seminars. Starting with convex functions on the line, it leads to interconnected topics in convexity, differentiability and subdifferentiability of convex functions in Banach spaces, generic continuity of monotone operators, geometry of Banach spaces and the Radon-Nikodym property, convex analysis, variational princ...

  15. A Note on Upper Convex Density

    Institute of Scientific and Technical Information of China (English)

    YIN JIAN-DONG; ZHOU ZUO-LING

    2010-01-01

    For a self-similar set E satisfying the open set condition,upper convex density is an important concept for the computation of its Hausdorff measure,and it is well known that the set of relative interior points with upper convex density 1has a full Hausdorff measure.But whether the upper convex densities of E at all the relative interior points are equal to 1? In other words,whether there exists a relative interior point of E such that the upper convex density of E at this point is less than 1?In this paper,the authors construct a self-similar set satisfying the open set condition,which has a relative interior point with upper convex density less than 1.Thereby,the above problem is sufficiently answered.

  16. Generalized convexity, generalized monotonicity recent results

    CERN Document Server

    Martinez-Legaz, Juan-Enrique; Volle, Michel

    1998-01-01

    A function is convex if its epigraph is convex. This geometrical structure has very strong implications in terms of continuity and differentiability. Separation theorems lead to optimality conditions and duality for convex problems. A function is quasiconvex if its lower level sets are convex. Here again, the geo­ metrical structure of the level sets implies some continuity and differentiability properties for quasiconvex functions. Optimality conditions and duality can be derived for optimization problems involving such functions as well. Over a period of about fifty years, quasiconvex and other generalized convex functions have been considered in a variety of fields including economies, man­ agement science, engineering, probability and applied sciences in accordance with the need of particular applications. During the last twenty-five years, an increase of research activities in this field has been witnessed. More recently generalized monotonicity of maps has been studied. It relates to generalized conve...

  17. A plasticity principle of convex quadrilaterals on a complete convex surface of bounded specific curvature

    CERN Document Server

    Zachos, Anastasios

    2010-01-01

    We obtain the plasticity equations for convex quadrilaterals on a complete convex surface with bounded specific curvature and derive a plasticity principle which states that: Given four shortest arcs which meet at the weighted Fermat-Torricelli point P_F and their endpoints form a convex quadrilateral, an increase of the weight that corresponds to a shortest arc causes a decrease to the two weights that correspond to the two neighboring shortest arcs and an increase to the weight that corresponds to the opposite shortest arc. We show a connection between the plasticity of convex quadrilaterals on a complete convex surface with bounded specific curvature with the plasticity of generalized convex quadrilaterals on a manifold which is composed by triangles located on a complete convex surface of bounded specific curvature and triangles located on a two dimensional sphere whose constant Gaussian curvature equals to the infimum or supremum of the specific curvature. Furthermore, we give some cases of geometrizatio...

  18. Photoacoustic tomography of monkey brain using virtual point ultrasonic transducers.

    Science.gov (United States)

    Nie, Liming; Guo, Zijian; Wang, Lihong V

    2011-07-01

    A photoacoustic tomography system (PAT) using virtual point ultrasonic transducers was developed and applied to image a monkey brain. The custom-built transducers provide a 10-fold greater field-of-view (FOV) than finite-aperture unfocused transducers as well as an improved signal-to-noise ratio (SNR) and reduced artifacts rather than negative-lens transducers. Their tangential resolution, radial resolution, and (SNR) improvements were quantified using tissue phantoms. Our PAT system can achieve high uniformity in both resolution (8) within a large FOV of 6 cm in diameter, even when the imaging objects are enclosed by a monkey skull. The cerebral cortex of a monkey brain was accurately mapped transcranially, through a skull ranging from 2 to 4 mm in thickness. This study demonstrates that PAT can overcome the optical and ultrasound attenuation of a relatively thick skull and can potentially be applied to human neonatal brain imaging.

  19. Prostate Ultrasound

    Medline Plus

    Full Text Available ... Prostate Ultrasound Imaging? What is Ultrasound Imaging of the Prostate? Ultrasound is safe and painless, and produces ... of page What are some common uses of the procedure? A transrectal ultrasound of the prostate gland ...

  20. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... are the limitations of Pelvic Ultrasound Imaging? What is Pelvic Ultrasound Imaging? Ultrasound is safe and painless, ... through the blood vessels. top of page How is the procedure performed? Transabdominal: For most ultrasound exams, ...

  1. Prostate Ultrasound

    Medline Plus

    Full Text Available ... Ultrasound - Prostate Ultrasound of the prostate uses sound waves to produce pictures of a man’s prostate gland ... of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or sonography , ...

  2. Ultrasound - Breast

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Ultrasound - Breast Ultrasound imaging of the breast uses sound waves ... the Breast? What is Ultrasound Imaging of the Breast? Ultrasound is safe and painless, and produces pictures ...

  3. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... Ultrasound - Pelvis Ultrasound imaging of the pelvis uses sound waves to produce pictures of the structures and ... pictures of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or ...

  4. Prostate Ultrasound

    Medline Plus

    Full Text Available ... Z Ultrasound - Prostate Ultrasound of the prostate uses sound waves to produce pictures of a man’s prostate ... pictures of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or ...

  5. Prostate Ultrasound

    Medline Plus

    Full Text Available ... Prostate Ultrasound Imaging? What is Ultrasound Imaging of the Prostate? Ultrasound is safe and painless, and produces ... of page What are some common uses of the procedure? A transrectal ultrasound of the prostate gland ...

  6. Konstruktion af transducer

    DEFF Research Database (Denmark)

    Henriksen, Lars; Nielsen, Martin Pram

    Formålet med dette midtvejsprojekt er at udarbejde en transducer til måling af pressers stivhed. Dette er gjort på baggrund af en gennemgang af både presse- og stativ-typer samtidig med at udbøjningssituationen beskrives. Der introduceres en ide, der udgør grundkonceptet for opmålingsproceduren o...... færdige transducer – Load cellen. Strain gauge sørger for dataopsamlingen fra load cellen. Disse kalibreres således at transduceren er klar til de videre målinger der ligger i forlængelse af dette projekt....

  7. MRI-compatible ultrasound heating system with ring-shaped phased arrays for breast tumor thermal therapy.

    Science.gov (United States)

    Chen, Hung-Nien; Chen, Guan-Ming; Lin, Bo-Sian; Lien, Pi-Hsien; Chen, Yung-Yaw; Chen, Gin-Shin; Lin, Win-Li

    2013-01-01

    Therapeutic ultrasound transducers can carry out precise and efficient power deposition for tumor thermal therapy under the guidance of magnetic resonance imaging. For a better heating, organ-specific ultrasound transducers with precision location control system should be developed for tumors located at various organs. It is feasible to perform a better heating for breast tumor thermal therapy with a ring-shaped ultrasound phased-array transducer. In this study, we developed ring-shaped phased-array ultrasound transducers with 1.0 and 2.5 MHz and a precision location control system to drive the transducers to the desired location to sonicate the designated region. Both thermo-sensitive hydrogel phantom and ex vivo fresh pork were used to evaluate the heating performance of the transducers. The results showed that the ring-shaped phased array ultrasound transducers were very promising for breast tumor heating with the variation of heating patterns and without overheating the ribs.

  8. Design of advanced ultrasonic transducers for welding devices.

    Science.gov (United States)

    Parrini, L

    2001-11-01

    A new high frequency ultrasonic transducer has been conceived, designed, prototyped, and tested. In the design phase, an advanced approach was used and established. The method is based on an initial design estimate obtained with finite element method (FEM) simulations. The simulated ultrasonic transducers and resonators are then built and characterized experimentally through laser interferometry and electrical resonance spectra. The comparison of simulation results with experimental data allows the parameters of FEM models to be adjusted and optimized. The achieved FEM simulations exhibit a remarkably high predictive potential and allow full control of the vibration behavior of the transducer. The new transducer is mounted on a wire bonder with a flange whose special geometry was calculated by means of FEM simulations. This flange allows the transducer to be attached on the wire bonder, not only in longitudinal nodes, but also in radial nodes of the ultrasonic field excited in the horn. This leads to a total decoupling of the transducer to the wire bonder, which has not been achieved so far. The new approach to mount ultrasonic transducers on a welding device is of major importance, not only for wire bonding, but also for all high power ultrasound applications and has been patented.

  9. Quasi-convex Functions in Carnot Groups

    Institute of Scientific and Technical Information of China (English)

    Mingbao SUN; Xiaoping YANG

    2007-01-01

    In this paper, the authors introduce the concept of h-quasiconvex functions on Carnot groups G. It is shown that the notions of h-quasiconvex functions and h-convex sets are equivalent and the L∞ estimates of first derivatives of h-quasiconvex functions are given. For a Carnot group G of step two, it is proved that h-quasiconvex functions are locally bounded from above. Furthermore, the authors obtain that h-convex functions are locally Lipschitz continuous and that an h-convex function is twice differentiable almost everywhere.

  10. On the vertex index of convex bodies

    CERN Document Server

    Bezdek, Karoly

    2011-01-01

    We introduce the vertex index, vein(K), of a given centrally symmetric convex body K, which, in a sense, measures how well K can be inscribed into a convex polytope with small number of vertices. This index is closely connected to the illumination parameter of a body, introduced earlier by the first named author, and, thus, related to the famous conjecture in Convex Geometry about covering of a d-dimensional body by 2^d smaller positively homothetic copies. We provide asymptotically sharp estimates (up to a logarithmic term) of this index in the general case. Also, we provide sharp estimates in dimensions 2 and 3.

  11. Children's (Pediatric) Abdominal Ultrasound Imaging

    Medline Plus

    Full Text Available ... and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through ... during a single exam. The transducer sends out high-frequency sound waves (that the human ear cannot hear) ...

  12. Ultrasound Harmonic Classification of Microemboli

    NARCIS (Netherlands)

    P.C. Palanchon

    2004-01-01

    textabstractThe ultrasound community has experienced dramatic technical advances over the last decades, such as blood °ow measurements with elabo rate Doppler techniques or real time three-dimensional imaging with 2-D phased array transducers. This was partly ascribed to the advantages of ultraso

  13. Nonlinear intravascular ultrasound contrast imaging

    NARCIS (Netherlands)

    Goertz, David E.; Frijlink, Martijn E.; de Jong, N.; van der Steen, Antonius F.W.

    2006-01-01

    Nonlinear contrast agent imaging with intravascular ultrasound (IVUS) is investigated using a prototype IVUS system and an experimental small bubble contrast agent. The IVUS system employed a mechanically scanned single element transducer and was operated at a 20 MHz transmit frequency (F20) for

  14. Tunable-angle wedge transducer for improved acoustophoretic control in a microfluidic chip

    DEFF Research Database (Denmark)

    Iranmanesh, I.; Barnkob, Rune; Bruus, Henrik;

    2012-01-01

    coupling angle, and transducer actuation method (single-frequency actuation or frequency-modulation actuation). The energy-density analysis is based on measuring the transmitted light intensity through a microfluidic channel filled with a suspension of 5-μm-diameter beads and the results with the tunable...... particle patterns with average acoustic energy densities comparable to those obtained using single-frequency actuation.......We present a tunable-angle wedge ultrasound transducer for improved control of microparticle acoustophoresis in a microfluidic chip. The transducer is investigated by analyzing the pattern of aligned particles and induced acoustic energy density while varying the system geometry, transducer...

  15. Modeling of phased array transducers.

    Science.gov (United States)

    Ahmad, Rais; Kundu, Tribikram; Placko, Dominique

    2005-04-01

    Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.

  16. Noah, Joseph and Convex Hulls

    Science.gov (United States)

    Watkins, N. W.; Chau, Y.; Chapman, S. C.

    2010-12-01

    The idea of describing animal movement by mathematical models based on diffusion and Brownian motion has a long heritage. It has thus been natural to account for those aspects of motion that depart from the Brownian by the use of models incorporating long memory & subdiffusion (“the Joseph effect”) and/or heavy tails & superdiffusion (“the Noah effect”). My own interest in this problem was originally from a geoscience perspective, and was triggered by the need to model time series in space physics where both effects coincide. Subsequently I have been involved in animal foraging studies [e.g. Edwards et al, Nature, 2007]. I will describe some recent work [Watkins et al, PRE, 2009] which studies how fixed-timestep and variable-timestep formulations of anomalous diffusion are related in the presence of heavy tails and long range memory (stable processes versus the CTRW). Quantities for which different scaling relations are predicted between the two approaches are of particular interest, to aid testability. I will also present some of work in progress on the convex hull of anomalously diffusing walkers, inspired by its possible relevance to the idea of home range in biology, and by Randon-Furling et al’s recent analytical results in the Brownian case [PRL, 2009].

  17. Design and fabrication of liner-arroy ultrasonic transducer using KLM and FEM simulation for non-destructive testing

    Energy Technology Data Exchange (ETDEWEB)

    Park, Chan Yuk; Sung, Jin Ho; Jeong, Jong Seob [Dept. of Medical Biotechnology, Dongguk University Biomedi Campus, Goyang (Korea, Republic of)

    2015-04-15

    In this paper, a linear-array transducer capable of overcoming the faults of a single element and phased array transducers with convex shape for non-destructive ultrasonic testing was designed and fabricated. A 5.5 MHz linear-array transducer was designed using the PiezoCAD program based on the KLM analysis and the PZFlex program based on the FEM analysis. A 2-2 composite structure was employed to achieve broad-band characteristics. A 128 element linear-array transducer was fabricated and its performance was compared with the simulation results. The center frequency of the fabricated transducer was 5.5 Mhzand the -6 dB frequency bandwidth was 70 %. Thus, we expect that the designed transducer can provide an effective inner image of the test material during non-destructive ultrasonic testing.

  18. A hybrid transducer to magnetically and ultrasonically evaluate magnetic fluids.

    Science.gov (United States)

    Bruno, Alexandre Colello; Pavan, Théo Z; Baffa, Oswaldo; Carneiro, Antonio Adilton Oliveira

    2013-09-01

    Ultrasound, magnetic fields, and optical techniques have been explored for clinical diagnosis and therapy. However, these techniques have limitations. In this study, we constructed and characterized a transducer to magnetically and ultrasonically investigate samples labeled with magnetic particles. The transducer is a hybrid system consisting of an ac biosusceptometer (ACB) and an ultrasonic transducer. The basic operation principle consisted of measuring the magnetization and microvibrations of ferromagnetic particles (37 and 70 μm) mixed in yogurt and excited by an external alternating magnetic field generated by the ACB's excitation coils. The vibration of the ferromagnetic particles was measured in phantoms using a Doppler ultrasonic transducer; we verified the sensitivity to detecting the vibrations at low concentrations of ferromagnetic material (~1%). The responses of the susceptometer and Doppler ultrasound linearly depended on the voltage level applied to the magnetizing coils at low ferromagnetic particle concentrations (⩽ 5%). We also conducted a repeatability test on the prototype, which indicated a deviation of 0.94% and 0.25% in the Doppler and susceptometric measurements, respectively. We can conclude that the hybrid transducer technique has potential clinical applications.

  19. Technical quality assessment of breast ultrasound according to American College of Radiology (ACR) Standards

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Kyung Hee; Kim, Eun Kyung; Kim, Young Ah; Son, Eun Ju; Oh, Ki Keun [Yonsei University College of Medicine, Seoul (Korea, Republic of); Chung, Sun Yang [Pochon CHA University, Pochon (Korea, Republic of)

    2003-06-15

    To evaluate the technical quality of breast ultrasound based on American College of Radiology(ACR) standards. Between March 2002 and July 2002, ninety three breast sonograms obtained from 73 institutions were evaluated based on ACR standards for the hardware, technical settings, labeling of the images and identification. Of 93 breast sonograms, a satisfactory compliance with all ACR standards in the performance of breast US examinations was documented in 31% while the remaining 69% did not fully meet all ACR standards. 4.3% of breast US examinations were performed with a convex transducers, and the focal zone was inappropriately positioned in 14.2%. Gray-scale gain was subjectively characterized as inappropriate in 26.9%, and the size of lesion was not measured in 7.5%. Anatomic location of lesions was inappropriately described in 9.3%. The orientation of an US transducer was not properly labeled on any images in 33.3%. Inadequate recording of patient's information was noted in 43.3%. 50% of sonograms at University medical centers and larger general hospitals fully met all ACR standards while 36.8% at radiologic clinics and 12.1% at other private clinics met all ACR standards. Overall, 69% of breast sonograms failed to meet the quality criteria of the ACR standards. Therefore, it is essential to educate the basic technical details in performing breast US for the quality control.

  20. Revising incompletely specified convex probabilistic belief bases

    CSIR Research Space (South Africa)

    Rens, G

    2016-04-01

    Full Text Available International Workshop on Non-Monotonic Reasoning (NMR), 22-24 April 2016, Cape Town, South Africa Revising Incompletely Specified Convex Probabilistic Belief Bases Gavin Rens CAIR_, University of KwaZulu-Natal, School of Mathematics, Statistics...

  1. Relations between Lipschitz functions and convex functions

    Institute of Scientific and Technical Information of China (English)

    RUAN Yingbin

    2005-01-01

    We discuss the relationship between Lipschitz functions and convex functions.By these relations, we give a sufficient condition for the set of points where Lipschitz functions on a Hilbert space is Frechet differentiable to be residual.

  2. Some integral inequalities for logarithmically convex functions

    Directory of Open Access Journals (Sweden)

    Mevlüt Tunç

    2014-07-01

    Full Text Available The main aim of the present note is to establish new Hadamard like integral inequalities involving log-convex function. We also prove some Hadamard-type inequalities, and applications to the special means are given.

  3. Convex analysis and optimization in Hadamard spaces

    CERN Document Server

    Bacak, Miroslav

    2014-01-01

    This book gives a first systematic account on the subject of convex analysis and optimization in Hadamard spaces. It is primarily aimed at both graduate students and researchers in analysis and optimization.

  4. Teaching a sonographically guided invasive procedure to first-year medical students using a novel finger transducer.

    Science.gov (United States)

    Benninger, Brion; Corbett, Rebecca; Delamarter, Taylor

    2013-04-01

    The exposure to ultrasound technology in medicine is increasing at multiple training levels. Ultrasound transducers have evolved to provide higher-resolution imaging for more accurate structural identification, with few improvements in ease of use. This study investigated a novel finger ultrasound transducer used by first-year medical students conducting structural identification and practicing an invasive procedure. A literature search was conducted on texts, specialty journals, and websites regarding the anatomy of internal jugular and subclavian vein central line placement with sonographic guidance and the use of a finger transducer. First-year medical students performed timed sonographically guided cannulation on the internal jugular and subclavian veins on a phantom torso and identified the internal jugular and subclavian veins on a healthy volunteer using the finger transducer and a conventional transducer. After exposure to both transducers, a survey was taken regarding transducer preference. The literature search revealed no studies comparing finger and classic transducers or sonographically guided central line techniques being conducted by first-year medical students. The students identified and cannulated the internal jugular and subclavian veins using both transducers. Survey results revealed that 70% of the students preferred the finger transducer. This study showed that first-year medical students could interpret sonographic anatomy while conducting a clinical procedure. The finger transducer proved successful in structure identification and was preferred to the classic transducer because of its combined tactile presence. This pilot study of a novel finger transducer showed the benefits of combining palpatory skills with ultrasound technology in teaching first-year medical students to perform invasive procedures.

  5. Linearization functors on real convex sets

    OpenAIRE

    Velasco, Mauricio

    2012-01-01

    We prove that linearizing certain families of polynomial optimization problems leads to new functorial operations in real convex sets. We show that under some conditions these operations can be computed or approximated in ways amenable to efficient computation. These operations are convex analogues of Hom functors, tensor products, symmetric powers, exterior powers and general Schur functors on vector spaces and lead to novel constructions even for polyhedra.

  6. Deformation in locally convex topological linear spaces

    Institute of Scientific and Technical Information of China (English)

    DING; Yanheng

    2004-01-01

    We are concerned with a deformation theory in locally convex topological linear spaces. A special "nice" partition of unity is given. This enables us to construct certain vector fields which are locally Lipschitz continuous with respect to the locally convex topology. The existence, uniqueness and continuous dependence of flows associated to the vector fields are established. Deformations related to strongly indefinite functionals are then obtained. Finally, as applications, we prove some abstract critical point theorems.

  7. The convexity radius of a Riemannian manifold

    OpenAIRE

    Dibble, James

    2014-01-01

    The ratio of convexity radius over injectivity radius may be made arbitrarily small within the class of compact Riemannian manifolds of any fixed dimension at least two. This is proved using Gulliver's method of constructing manifolds with focal points but no conjugate points. The approach is suggested by a characterization of the convexity radius that resembles a classical result of Klingenberg about the injectivity radius.

  8. Future needs for biomedical transducers

    Science.gov (United States)

    Wooten, F. T.

    1971-01-01

    In summary there are three major classes of transducer improvements required: improvements in existing transducers, needs for unexploited physical science phenomena in transducer design, and needs for unutilized physiological phenomena in transducer design. During the next decade, increasing emphasis will be placed on noninvasive measurement in all of these areas. Patient safety, patient comfort, and the need for efficient utilization of the time of both patient and physician requires that noninvasive methods of monitoring be developed.

  9. [Ultrasound findings in rhabdomyolysis].

    Science.gov (United States)

    Carrillo-Esper, Raúl; Galván-Talamantes, Yazmin; Meza-Ayala, Cynthia Margarita; Cruz-Santana, Julio Alberto; Bonilla-Reséndiz, Luis Ignacio

    Rhabdomyolysis is defined as skeletal muscle necrosis. Ultrasound assessment has recently become a useful tool for the diagnosis and monitoring of muscle diseases, including rhabdomyolysis. A case is presented on the ultrasound findings in a patient with rhabdomyolysis. To highlight the importance of ultrasound as an essential part in the diagnosis in rhabdomyolysis, to describe the ultrasound findings, and review the literature. A 30 year-old with post-traumatic rhabdomyolysis of both thighs. Ultrasound was performed using a Philips Sparq model with a high-frequency linear transducer (5-10MHz), in low-dimensional scanning mode (2D), in longitudinal and transverse sections at the level of both thighs. The images obtained showed disorganisation of the orientation of the muscle fibres, ground glass image, thickening of the muscular fascia, and the presence of anechoic areas. Ultrasound is a useful tool in the evaluation of rhabdomyolysis. Copyright © 2015 Academia Mexicana de Cirugía A.C. Publicado por Masson Doyma México S.A. All rights reserved.

  10. Convexity conditions and normal structure of Banach spaces

    Science.gov (United States)

    Saejung, Satit

    2008-08-01

    We prove that F-convexity, the property dual to P-convexity of Kottman, implies uniform normal structure. Moreover, in the presence of the WORTH property, normal structure follows from a weaker convexity condition than F-convexity. The latter result improves the known fact that every uniformly nonsquare space with the WORTH property has normal structure.

  11. Entropy Coherent and Entropy Convex Measures of Risk

    NARCIS (Netherlands)

    Laeven, R.J.A.; Stadje, M.A.

    2011-01-01

    We introduce two subclasses of convex measures of risk, referred to as entropy coherent and entropy convex measures of risk. We prove that convex, entropy convex and entropy coherent measures of risk emerge as certainty equivalents under variational, homothetic and multiple priors preferences, respe

  12. A further characteristic of abstract convexity structures on topological spaces

    Science.gov (United States)

    Xiang, Shu-Wen; Xia, Shunyou

    2007-11-01

    In this paper, we give a characteristic of abstract convexity structures on topological spaces with selection property. We show that if a convexity structure defined on a topological space has the weak selection property then satisfies H0-condition. Moreover, in a compact convex subset of a topological space with convexity structure, the weak selection property implies the fixed point property.

  13. Exact and Approximate Sizes of Convex Datacubes

    Science.gov (United States)

    Nedjar, Sébastien

    In various approaches, data cubes are pre-computed in order to efficiently answer Olap queries. The notion of data cube has been explored in various ways: iceberg cubes, range cubes, differential cubes or emerging cubes. Previously, we have introduced the concept of convex cube which generalizes all the quoted variants of cubes. More precisely, the convex cube captures all the tuples satisfying a monotone and/or antimonotone constraint combination. This paper is dedicated to a study of the convex cube size. Actually, knowing the size of such a cube even before computing it has various advantages. First of all, free space can be saved for its storage and the data warehouse administration can be improved. However the main interest of this size knowledge is to choose at best the constraints to apply in order to get a workable result. For an aided calibrating of constraints, we propose a sound characterization, based on inclusion-exclusion principle, of the exact size of convex cube as long as an upper bound which can be very quickly yielded. Moreover we adapt the nearly optimal algorithm HyperLogLog in order to provide a very good approximation of the exact size of convex cubes. Our analytical results are confirmed by experiments: the approximated size of convex cubes is really close to their exact size and can be computed quasi immediately.

  14. Non-linear Ultrasound Imaging

    DEFF Research Database (Denmark)

    Du, Yigang

    without iteration steps. The ASA is implemented in combination with Field II and extended to simulate the pulsed ultrasound fields. The simulated results from a linear array transducer are made by the ASA based on Field II, and by a released non-linear simulation program- Abersim, respectively....... The calculation speed of the ASA is increased approximately by a factor of 140. For the second harmonic point spread function the error of the full width is 1.5% at -6 dB and 6.4% at -12 dB compared to Abersim. To further investigate the linear and non-linear ultrasound fields, hydrophone measurements.......3% relative to the measurement from a 1 inch diameter transducer. A preliminary study for harmonic imaging using synthetic aperture sequential beamforming (SASB) has been demonstrated. A wire phantom underwater measurement is made by an experimental synthetic aperture real-time ultrasound scanner (SARUS...

  15. Three dimensional transducer

    Science.gov (United States)

    Warren, Oden Lee; Asif, Syed Amanulla Syed; Oh, Yunje; Feng, Yuxin; Cyrankowski, Edward; Major, Ryan

    2014-09-30

    A testing instrument for mechanical testing at nano or micron scale includes a transducer body, and a coupling shaft coupled with a probe tip. A transducer body houses a capacitor. The capacitor includes first and second counter electrodes and a center electrode assembly interposed therebetween. The center electrode assembly is movable with the coupling shaft relative to the first and second counter electrodes, for instance in one or more of dimensions including laterally and normally. The center electrode assembly includes a center plate coupled with the coupling shaft and one or more springs extending from the center plate. Upper and lower plates are coupled with the center plate and cover the center plate and the one or more springs. A shaft support assembly includes one or more support elements coupled along the coupling shaft. The shaft support assembly provides lateral support to the coupling shaft.

  16. Nano-optomechanical transducer

    Science.gov (United States)

    Rakich, Peter T; El-Kady, Ihab F; Olsson, Roy H; Su, Mehmet Fatih; Reinke, Charles; Camacho, Ryan; Wang, Zheng; Davids, Paul

    2013-12-03

    A nano-optomechanical transducer provides ultrabroadband coherent optomechanical transduction based on Mach-wave emission that uses enhanced photon-phonon coupling efficiencies by low impedance effective phononic medium, both electrostriction and radiation pressure to boost and tailor optomechanical forces, and highly dispersive electromagnetic modes that amplify both electrostriction and radiation pressure. The optomechanical transducer provides a large operating bandwidth and high efficiency while simultaneously having a small size and minimal power consumption, enabling a host of transformative phonon and signal processing capabilities. These capabilities include optomechanical transduction via pulsed phonon emission and up-conversion, broadband stimulated phonon emission and amplification, picosecond pulsed phonon lasers, broadband phononic modulators, and ultrahigh bandwidth true time delay and signal processing technologies.

  17. Three dimensional transducer

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Oden Lee; Asif, Syed Amanulla Syed; Oh, Yunje; Feng, Yuxin; Cyrankowski, Edward; Major, Ryan

    2014-09-30

    A testing instrument for mechanical testing at nano or micron scale includes a transducer body, and a coupling shaft coupled with a probe tip. A transducer body houses a capacitor. The capacitor includes first and second counter electrodes and a center electrode assembly interposed therebetween. The center electrode assembly is movable with the coupling shaft relative to the first and second counter electrodes, for instance in one or more of dimensions including laterally and normally. The center electrode assembly includes a center plate coupled with the coupling shaft and one or more springs extending from the center plate. Upper and lower plates are coupled with the center plate and cover the center plate and the one or more springs. A shaft support assembly includes one or more support elements coupled along the coupling shaft. The shaft support assembly provides lateral support to the coupling shaft.

  18. Numerical transducer modelling

    DEFF Research Database (Denmark)

    Cutanda, Vicente

    1999-01-01

    Numerical modelling is of importance for the design, improvement and study of acoustic transducers such as microphones and accelerometers. Techniques like the boundary element method and the finite element method are the most common supplement to the traditional empirical and analytical approaches...... errors and instabilities in the computations of numerical solutions. An investigation to deal with this narrow-gap problem has been carried out....

  19. Stress wave focusing transducers

    Energy Technology Data Exchange (ETDEWEB)

    Visuri, S.R., LLNL

    1998-05-15

    Conversion of laser radiation to mechanical energy is the fundamental process behind many medical laser procedures, particularly those involving tissue destruction and removal. Stress waves can be generated with laser radiation in several ways: creation of a plasma and subsequent launch of a shock wave, thermoelastic expansion of the target tissue, vapor bubble collapse, and ablation recoil. Thermoelastic generation of stress waves generally requires short laser pulse durations and high energy density. Thermoelastic stress waves can be formed when the laser pulse duration is shorter than the acoustic transit time of the material: {tau}{sub c} = d/c{sub s} where d = absorption depth or spot diameter, whichever is smaller, and c{sub s} = sound speed in the material. The stress wave due to thermoelastic expansion travels at the sound speed (approximately 1500 m/s in tissue) and leaves the site of irradiation well before subsequent thermal events can be initiated. These stress waves, often evolving into shock waves, can be used to disrupt tissue. Shock waves are used in ophthalmology to perform intraocular microsurgery and photodisruptive procedures as well as in lithotripsy to fragment stones. We have explored a variety of transducers that can efficiently convert optical to mechanical energy. One such class of transducers allows a shock wave to be focused within a material such that the stress magnitude can be greatly increased compared to conventional geometries. Some transducer tips could be made to operate regardless of the absorption properties of the ambient media. The size and nature of the devices enable easy delivery, potentially minimally-invasive procedures, and precise tissue- targeting while limiting thermal loading. The transducer tips may have applications in lithotripsy, ophthalmology, drug delivery, and cardiology.

  20. Frequency steerable acoustic transducers

    Science.gov (United States)

    Senesi, Matteo

    Structural health monitoring (SHM) is an active research area devoted to the assessment of the structural integrity of critical components of aerospace, civil and mechanical systems. Guided wave methods have been proposed for SHM of plate-like structures using permanently attached piezoelectric transducers, which generate and sense waves to evaluate the presence of damage. Effective interrogation of structural health is often facilitated by sensors and actuators with the ability to perform electronic, i.e. phased array, scanning. The objective of this research is to design an innovative directional piezoelectric transducer to be employed for the localization of broadband acoustic events, or for the generation of Lamb waves for active interrogation of structural health. The proposed Frequency Steerable Acoustic Transducers (FSATs) are characterized by a spatial arrangement of active material which leads to directional characteristics varying with frequency. Thus FSATs can be employed both for directional sensing and generation of guided waves without relying on phasing and control of a large number of channels. The analytical expression of the shape of the FSATs is obtained through a theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. The FSAT configurations analyzed in this work are a quadrilateral array and a geometry which corresponds to a spiral in the wavenumber domain. The quadrilateral array is experimentally validated, confirming the concept of frequency-dependent directionality. Its limited directivity is improved by the Wavenumber Spiral FSAT (WS-FSAT), which, instead, is characterized by a continuous frequency dependent directionality. Preliminary validations of the WS-FSAT, using a laser doppler vibrometer, are followed by the implementation of the WS-FSAT as a properly shaped piezo transducer. The prototype is first used for localization of acoustic broadband sources. Signal processing

  1. Fluid force transducer

    Science.gov (United States)

    Jendrzejczyk, Joseph A.

    1982-01-01

    An electrical fluid force transducer for measuring the magnitude and direction of fluid forces caused by lateral fluid flow, includes a movable sleeve which is deflectable in response to the movement of fluid, and a rod fixed to the sleeve to translate forces applied to the sleeve to strain gauges attached to the rod, the strain gauges being connected in a bridge circuit arrangement enabling generation of a signal output indicative of the magnitude and direction of the force applied to the sleeve.

  2. Polymer film composite transducer

    Science.gov (United States)

    Owen, Thomas E.

    2005-09-20

    A composite piezoelectric transducer, whose piezoeletric element is a "ribbon wound" film of piezolectric material. As the film is excited, it expands and contracts, which results in expansion and contraction of the diameter of the entire ribbon winding. This is accompanied by expansion and contraction of the thickness of the ribbon winding, such that the sound radiating plate may be placed on the side of the winding.

  3. NONINVASIVE MEASUREMENT OF LOCAL THERMAL DIFFUSIVITY USING BACKSCATTERED ULTRASOUND AND FOCUSED ULTRASOUND HEATING

    OpenAIRE

    2008-01-01

    Previously, noninvasive methods of estimating local tissue thermal and acoustic properties using backscattered ultrasound have been proposed in the literature. In this article, a noninvasive method of estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data and applying novel signal processing techniques is developed. A high intensity focused ultrasound (HIFU) transducer operating at subablative intensities is employed to create...

  4. Steerable Doppler transducer probes

    Energy Technology Data Exchange (ETDEWEB)

    Fidel, H.F.; Greenwood, D.L.

    1986-07-22

    An ultrasonic diagnostic probe is described which is capable of performing ultrasonic imaging and Doppler measurement consisting of: a hollow case having an acoustic window which passes ultrasonic energy and including chamber means for containing fluid located within the hollow case and adjacent to a portion of the acoustic window; imaging transducer means, located in the hollow case and outside the fluid chamber means, and oriented to direct ultrasonic energy through the acoustic window toward an area which is to be imaged; Doppler transducer means, located in the hollow case within the fluid chamber means, and movably oriented to direct Doppler signals through the acoustic window toward the imaged area; means located within the fluid chamber means and externally controlled for controllably moving the Doppler transducer means to select one of a plurality of axes in the imaged area along which the Doppler signals are to be directed; and means, located external to the fluid chamber means and responsive to the means for moving, for providing an indication signal for identifying the selected axis.

  5. High frequency PMN-PT single crystal focusing transducer fabricated by a mechanical dimpling technique.

    Science.gov (United States)

    Chen, Y; Lam, K H; Zhou, D; Cheng, W F; Dai, J Y; Luo, H S; Chan, H L W

    2013-02-01

    High frequency (∼30MHz and ∼80MHz) focusing ultrasound transducers were fabricated using a PMN-0.28PT single crystal by a mechanical dimpling technique. The dimpled single crystal was used as an active element for the focusing transducer. Compared with a plane transducer, the focusing transducer fabricated with a dimpled active element exhibits much broader bandwidth and higher sensitivity. Besides, a high quality image can be obtained by the 30MHz focusing transducer, in which the -6dB axial and lateral resolution is 27μm and 139μm, respectively. These results prove that the dimpling technique is capable to fabricate the high frequency focusing transducers with excellent performance for imaging applications.

  6. Experimental Evaluation of Three Designs of Electrodynamic Flexural Transducers

    Science.gov (United States)

    Eriksson, Tobias J. R.; Laws, Michael; Kang, Lei; Fan, Yichao; Ramadas, Sivaram N.; Dixon, Steve

    2016-01-01

    Three designs for electrodynamic flexural transducers (EDFT) for air-coupled ultrasonics are presented and compared. An all-metal housing was used for robustness, which makes the designs more suitable for industrial applications. The housing is designed such that there is a thin metal plate at the front, with a fundamental flexural vibration mode at ∼50 kHz. By using a flexural resonance mode, good coupling to the load medium was achieved without the use of matching layers. The front radiating plate is actuated electrodynamically by a spiral coil inside the transducer, which produces an induced magnetic field when an AC current is applied to it. The transducers operate without the use of piezoelectric materials, which can simplify manufacturing and prolong the lifetime of the transducers, as well as open up possibilities for high-temperature applications. The results show that different designs perform best for the generation and reception of ultrasound. All three designs produced large acoustic pressure outputs, with a recorded sound pressure level (SPL) above 120 dB at a 40 cm distance from the highest output transducer. The sensitivity of the transducers was low, however, with single shot signal-to-noise ratio (SNR)≃15 dB in transmit–receive mode, with transmitter and receiver 40 cm apart. PMID:27571075

  7. Subharmonic Contrast Intravascular Ultrasound for Vasa Vasorum Imaging

    NARCIS (Netherlands)

    Goertz, David E.; Frijlink, Martijn E.; Tempel, Dennie; Bhagwandas, Vijay; Gisolf, Andries; Krams, Robert; Jong, de Nico; Steen, van der Antonius F.W.

    2007-01-01

    The feasibility of subharmonic contrast intravascular ultrasound (IVUS) imaging was investigated using a prototype nonlinear IVUS system and the commercial contrast agent Definity™. The system employed a mechanically scanned commercial catheter with a custom transducer element fabricated to have sen

  8. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... Pelvis Ultrasound imaging of the pelvis uses sound waves to produce pictures of the structures and organs ... of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or sonography , ...

  9. Prostate Ultrasound

    Medline Plus

    Full Text Available ... gel. top of page How does the procedure work? Ultrasound imaging is based on the same principles ... to-use and less expensive than other imaging methods. Ultrasound imaging uses no ionizing radiation. Ultrasound scanning ...

  10. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... a pelvic ultrasound examination. Doppler ultrasound , also called color Doppler ultrasonography, is a special ultrasound technique that ... and processes the sounds and creates graphs or color pictures that represent the flow of blood through ...

  11. Intravascular ultrasound

    Science.gov (United States)

    IVUS; Ultrasound - coronary artery; Endovascular ultrasound; Intravascular echocardiography ... A tiny ultrasound wand is attached to the top of a thin tube. This tube is called a catheter. The catheter ...

  12. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... three types of pelvic ultrasound: abdominal, vaginal (for women), and rectal (for men). These exams are frequently ... pelvic ultrasound: abdominal ( transabdominal ) vaginal ( transvaginal / endovaginal ) for women rectal ( transrectal ) for men A Doppler ultrasound exam ...

  13. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... ultrasound images are captured in real-time, they can show the structure and movement of the body's ... Obstetrical Ultrasound page for more information . Ultrasound examinations can help diagnose symptoms experienced by women such as: ...

  14. Transducers for ultrasonic limb plethysmography

    Science.gov (United States)

    Nickell, W. T.; Wu, V. C.; Bhagat, P. K.

    1983-01-01

    The design, construction, and performance characteristics of ultasonic transducers suitable for limb plethysmography are presented. Both 3-mm-diameter flat-plate and 12-mm-diameter hemispheric ceramic transducers operating at 2 MHz were fitted in 1-mm thick epoxy-resin lens/acoustic-coupling structures and mounted in exercie-EKG electrode housings for placement on the calf using adhesive collars. The effects of transducer directional characteristics on performance under off-axis rotation and the electrical impedances of the transducers were measured: The flat transducer was found to be sensitive to rotation and have an impedance of 800 ohms; the hemispheric transducer, to be unaffected by rotation and have an impedance of 80 ohms. The use of hemispheric transducers as both transmitter and receiver, or of a flat transducer as transmitter and a hemispheric transducer as receiver, was found to produce adequate dimensional measurements, with minimum care in transducer placement, in short-term physiological experiments and long-term (up to 7-day) attachment tests.

  15. The Use of Phononic Crystals to Design Piezoelectric Power Transducers

    Directory of Open Access Journals (Sweden)

    Silvia Ronda

    2017-03-01

    Full Text Available It was recently proposed that the lateral resonances around the working resonance band of ultrasonic piezoelectric sandwich transducers can be stopped by a periodic array of circular holes drilled along the main propagation direction (a phononic crystal. In this work, the performance of different transducer designs made with this procedure is tested using laser vibrometry, electric impedance tests and finite element models (FEM. It is shown that in terms of mechanical vibration amplitude and acoustic efficiency, the best design for physiotherapy applications is when both, the piezoceramic and an aluminum capsule are phononic structures. The procedure described here can be applied to the design of power ultrasonic devices, physiotherapy transducers and other external medical power ultrasound applications where piston-like vibration in a narrow band is required.

  16. Wideband Single-Crystal Transducer for Bone Characterization

    Science.gov (United States)

    Liang, Yu; Snook, Kevin

    2012-01-01

    The microgravity conditions of space travel result in unique physiological demands on the human body. In particular, the absence of the continual mechanical stresses on the skeletal system that are present on Earth cause the bones to decalcify. Trabecular structure decreases in thickness and increases in spacing, resulting in decreased bone strength and increased risk of injury. Thus, monitoring bone health is a high priority for long-term space travel. A single probe covering all frequency bands of interest would be ideal for such measurements, and this would also minimize storage space and eliminate the complexity of integrating multiple probes. This invention is an ultrasound transducer for the structural characterization of bone. Such characterization measures features of reflected and transmitted ultrasound signals, and correlates these signals with bone structure metrics such as bone mineral density, trabecular spacing, and thickness, etc. The techniques used to determine these various metrics require measurements over a broad range of ultrasound frequencies, and therefore, complete characterization requires the use of several narrowband transducers. This is a single transducer capable of making these measurements in all the required frequency bands. The device achieves this capability through a unique combination of a broadband piezoelectric material; a design incorporating multiple resonator sizes with distinct, overlapping frequency spectra; and a micromachining process for producing the multiple-resonator pattern with common electrode surfaces between the resonators. This device consists of a pattern of resonator bars with common electrodes that is wrapped around a central mandrel such that the radiating faces of the resonators are coplanar and can be simultaneously applied to the sample to be measured. The device operates as both a source and receiver of acoustic energy. It is operated by connection to an electronic system capable of both providing an

  17. Analog gradient beamformer for a wireless ultrasound scanner

    Science.gov (United States)

    Di Ianni, Tommaso; Hemmsen, Martin Christian; Bagge, Jan; Jensen, Henrik; Vardi, Nitsan; Jensen, Jørgen Arendt

    2016-04-01

    This paper presents a novel beamformer architecture for a low-cost receiver front-end, and investigates if the image quality can be maintained. The system is oriented to the development of a hand-held wireless ultrasound probe based on Synthetic Aperture Sequential Beamforming, and has the advantage of effectively reducing circuit complexity and power dissipation. The array of transducers is divided into sub-apertures, in which the signals from the single channels are aligned through a network of cascaded gradient delays, and summed in the analog domain before A/D conversion. The delay values are quantized to simplify the shifting unit, and a single A/D converter is needed for each sub-aperture yielding a compact, low-power architecture that can be integrated in a single chip. A simulation study was performed using a 3:75MHz convex array, and the point spread function (PSF) for different configurations was evaluated in terms of lateral full-width-at-half-maximum (FWHM) and -20 dB cystic resolution (CR). Several setups were simulated varying the sub-aperture size N and the quantization step, and design constraints were obtained comparing the PSF to that of an ideal non-quantized system. The PSF is shown for N = 32 with a quantization step of 12 ns. For this configuration, the FWHM is degraded by 0.25% and the CR is 8.70% lower compared to the ideal situation. The results demonstrate that the gradient beamformer provides an adequate image quality, and open the way to a fully-integrated chip for a compact, low-cost, wireless ultrasound probe.

  18. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... through blood vessels. Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions. There are three types of pelvic ultrasound: ...

  19. Piezoelectric transducer array microspeaker

    KAUST Repository

    Carreno, Armando Arpys Arevalo

    2016-12-19

    In this paper we present the fabrication and characterization of a piezoelectric micro-speaker. The speaker is an array of micro-machined piezoelectric membranes, fabricated on silicon wafer using advanced micro-machining techniques. Each array contains 2n piezoelectric transducer membranes, where “n” is the bit number. Every element of the array has a circular shape structure. The membrane is made out four layers: 300nm of platinum for the bottom electrode, 250nm or lead zirconate titanate (PZT), a top electrode of 300nm and a structural layer of 50

  20. Numerical transducer modelling

    DEFF Research Database (Denmark)

    Cutanda, Vicente

    1999-01-01

    Numerical modelling is of importance for the design, improvement and study of acoustic transducers such as microphones and accelerometers. Techniques like the boundary element method and the finite element method are the most common supplement to the traditional empirical and analytical approaches....... However, there are several difficulties to be addressed that are derived from the size, internal structure and precision requirements that are characteristic of these devices. One of them, the presence of very close surfaces (e.g. the microphone diaphragm and back-electrode), leads to machine precision...

  1. Wellbore pressure transducer

    Science.gov (United States)

    Shuck, Lowell Z.

    1979-01-01

    Subterranean earth formations containing energy values are subjected to hydraulic fracturing procedures to enhance the recovery of the energy values. These fractures are induced in the earth formation by pumping liquid into the wellbore penetrating the earth formation until the pressure of the liquid is sufficient to fracture the earth formation adjacent to the wellbore. The present invention is directed to a transducer which is positionable within the wellbore to generate a signal indicative of the fracture initiation useful for providing a timing signal to equipment for seismic mapping of the fracture as it occurs and for providing a measurement of the pressure at which the fracture is initiated.

  2. RADIO-ACTIVE TRANSDUCER

    Science.gov (United States)

    Wanetick, S.

    1962-03-01

    ABS>ure the change in velocity of a moving object. The transducer includes a radioactive source having a collimated beam of radioactive particles, a shield which can block the passage of the radioactive beam, and a scintillation detector to measure the number of radioactive particles in the beam which are not blocked by the shield. The shield is operatively placed across the radioactive beam so that any motion normal to the beam will cause the shield to move in the opposite direction thereby allowing more radioactive particles to reach the detector. The number of particles detected indicates the acceleration. (AEC)

  3. Medical ultrasound systems.

    Science.gov (United States)

    Powers, Jeff; Kremkau, Frederick

    2011-08-06

    Medical ultrasound imaging has advanced dramatically since its introduction only a few decades ago. This paper provides a short historical background, and then briefly describes many of the system features and concepts required in a modern commercial ultrasound system. The topics addressed include array beam formation, steering and focusing; array and matrix transducers; echo image formation; tissue harmonic imaging; speckle reduction through frequency and spatial compounding, and image processing; tissue aberration; Doppler flow detection; and system architectures. It then describes some of the more practical aspects of ultrasound system design necessary to be taken into account for today's marketplace. It finally discusses the recent explosion of portable and handheld devices and their potential to expand the clinical footprint of ultrasound into regions of the world where medical care is practically non-existent. Throughout the article reference is made to ways in which ultrasound imaging has benefited from advances in the commercial electronics industry. It is meant to be an overview of the field as an introduction to other more detailed papers in this special issue.

  4. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... are captured. There is usually no discomfort from pressure as the transducer is pressed against the area ... over an area of tenderness, you may feel pressure or minor pain from the transducer. Once the ...

  5. Optimal convex shapes for concave functionals

    CERN Document Server

    Bucur, Dorin; Lamboley, Jimmy

    2011-01-01

    Motivated by a long-standing conjecture of Polya and Szeg\\"o about the Newtonian capacity of convex bodies, we discuss the role of concavity inequalities in shape optimization, and we provide several counterexamples to the Blaschke-concavity of variational functionals, including capacity. We then introduce a new algebraic structure on convex bodies, which allows to obtain global concavity and indecomposability results, and we discuss their application to isoperimetriclike inequalities. As a byproduct of this approach we also obtain a quantitative version of the Kneser-S\\"uss inequality. Finally, for a large class of functionals involving Dirichlet energies and the surface measure, we perform a local analysis of strictly convex portions of the boundary via second order shape derivatives. This allows in particular to exclude the presence of smooth regions with positive Gauss curvature in an optimal shape for Polya-Szeg\\"o problem.

  6. On the convexity of Relativistic Ideal Magnetohydrodynamics

    CERN Document Server

    Ibáñez, José-María; Aloy, Miguel-Ángel; Martí, José-María; Miralles, Juan-Antonio

    2015-01-01

    We analyze the influence of the magnetic field in the convexity properties of the relativistic magnetohydrodynamics system of equations. To this purpose we use the approach of Lax, based on the analysis of the linearly degenerate/genuinely non-linear nature of the characteristic fields. Degenerate and non-degenerate states are discussed separately and the non-relativistic, unmagnetized limits are properly recovered. The characteristic fields corresponding to the material and Alfv\\'en waves are linearly degenerate and, then, not affected by the convexity issue. The analysis of the characteristic fields associated with the magnetosonic waves reveals, however, a dependence of the convexity condition on the magnetic field. The result is expressed in the form of a generalized fundamental derivative written as the sum of two terms. The first one is the generalized fundamental derivative in the case of purely hydrodynamical (relativistic) flow. The second one contains the effects of the magnetic field. The analysis ...

  7. A generalization of the convex Kakeya problem

    KAUST Repository

    Ahn, Heekap

    2012-01-01

    We consider the following geometric alignment problem: Given a set of line segments in the plane, find a convex region of smallest area that contains a translate of each input segment. This can be seen as a generalization of Kakeya\\'s problem of finding a convex region of smallest area such that a needle can be turned through 360 degrees within this region. Our main result is an optimal Θ(n log n)-time algorithm for our geometric alignment problem, when the input is a set of n line segments. We also show that, if the goal is to minimize the perimeter of the region instead of its area, then the optimum placement is when the midpoints of the segments coincide. Finally, we show that for any compact convex figure G, the smallest enclosing disk of G is a smallest-perimeter region containing a translate of any rotated copy of G. © 2012 Springer-Verlag Berlin Heidelberg.

  8. Cost Allocation and Convex Data Envelopment

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Tind, Jørgen

    This paper considers allocation rules. First, we demonstrate that costs allocated by the Aumann-Shapley and the Friedman-Moulin cost allocation rules are easy to determine in practice using convex envelopment of registered cost data and parametric programming. Second, from the linear programming...... such as Data Envelopment Analysis (DEA). The convexity constraint of the BCC model introduces a non-zero slack in the objective function of the multiplier problem and we show that the cost allocation rules discussed in this paper can be used as candidates to allocate this slack value on to the input (or output...... problems involved it becomes clear that the allocation rules, technically speaking, allocate the non-zero value of the dual variable for a convexity constraint on to the output vector. Hence, the allocation rules can also be used to allocate inefficiencies in non-parametric efficiency measurement models...

  9. Non-convex multi-objective optimization

    CERN Document Server

    Pardalos, Panos M; Žilinskas, Julius

    2017-01-01

    Recent results on non-convex multi-objective optimization problems and methods are presented in this book, with particular attention to expensive black-box objective functions. Multi-objective optimization methods facilitate designers, engineers, and researchers to make decisions on appropriate trade-offs between various conflicting goals. A variety of deterministic and stochastic multi-objective optimization methods are developed in this book. Beginning with basic concepts and a review of non-convex single-objective optimization problems; this book moves on to cover multi-objective branch and bound algorithms, worst-case optimal algorithms (for Lipschitz functions and bi-objective problems), statistical models based algorithms, and probabilistic branch and bound approach. Detailed descriptions of new algorithms for non-convex multi-objective optimization, their theoretical substantiation, and examples for practical applications to the cell formation problem in manufacturing engineering, the process design in...

  10. Nonlinear Dynamic Modeling of Langevin-Type Piezoelectric Transducers

    Directory of Open Access Journals (Sweden)

    Nicolás Peréz Alvarez

    2015-11-01

    Full Text Available Langevin transducers are employed in several applications, such as power ultrasound systems, naval hydrophones, and high-displacement actuators. Nonlinear effects can influence their performance, especially at high vibration amplitude levels. These nonlinear effects produce variations in the resonant frequency, harmonics of the excitation frequency, in addition to loss of symmetry in the frequency response and “frequency domain hysteresis”. In this context, this paper presents a simplified nonlinear dynamic model of power ultrasound transducers requiring only two parameters for simulating the most relevant nonlinear effects. One parameter reproduces the changes in the resonance frequency and the other introduces the dependence of the frequency response on the history of the system. The piezoelectric constitutive equations are extended by a linear dependence of the elastic constant on the mechanical displacement amplitude. For introducing the frequency hysteresis, the elastic constant is computed by combining the current value of the mechanical amplitude with the previous state amplitude. The model developed in this work is applied for predicting the dynamic responses of a 26 kHz ultrasonic transducer. The comparison of theoretical and experimental responses, obtained at several input voltages around the tuned frequency, shows a good agreement, indicating that the model can accurately describe the transducer nonlinear behavior.

  11. Three dimensional (3d) transverse oscillation vector velocity ultrasound imaging

    DEFF Research Database (Denmark)

    2013-01-01

    An ultrasound imaging system (300) includes a transducer array (302) with a two- dimensional array of transducer elements configured to transmit an ultrasound signal and receive echoes, transmit circuitry (304) configured to control the transducer array to transmit the ultrasound signal so...... as to traverse a field of view, and receive circuitry (306) configured to receive a two dimensional set of echoes produced in response to the ultrasound signal traversing structure in the field of view, wherein the structure includes flowing structures such as flowing blood cells, organ cells etc. A beamformer...... (312) configured to beamform the echoes, and a velocity processor (314) configured to separately determine a depth velocity component, a transverse velocity component and an elevation velocity component, wherein the velocity components are determined based on the same transmitted ultrasound signal...

  12. Non-convex onion peeling using a shape hull algorithm

    OpenAIRE

    Fadili, Jalal M.; Melkemi, Mahmoud; Elmoataz, Abderrahim

    2004-01-01

    International audience; The convex onion-peeling of a set of points is the organization of these points into a sequence of interpolating convex polygons. This method is adequate to detect the shape of the “center” of a set of points when this shape is convex. However it reveals inadequate to detect non-convex shapes. Alternatively, we propose an extension of the convex onion-peeling method. It consists in representing a set of points with a sequence of non-convex polylines which are computed ...

  13. Uniform convexity and the splitting problem for selections

    CERN Document Server

    Balashov, Maxim V; 10.1016/j.jmaa.2009.06.045

    2009-01-01

    We continue to investigate cases when the Repov\\v{s}-Semenov splitting problem for selections has an affirmative solution for continuous set-valued mappings. We consider the situation in infinite-dimensional uniformly convex Banach spaces. We use the notion of Polyak of uniform convexity and modulus of uniform convexity for arbitrary convex sets (not necessary balls). We study general geometric properties of uniformly convex sets. We also obtain an affirmative solution of the splitting problem for selections of certain set-valued mappings with uniformly convex images.

  14. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    2016-01-01

    We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. When only measurements subject to noise...... of surface tensors are available for reconstruction, we recommend to use certain values of the surface tensors, namely harmonic intrinsic volumes instead of the surface tensors evaluated at the standard basis. The second algorithm we present is based on harmonic intrinsic volumes and allows for noisy...

  15. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. The second algorithm uses harmonic intrinsic...... volumes which are certain values of the surface tensors and allows for noisy measurements. From a generalized version of Wirtinger's inequality, we derive stability results that are utilized to ensure consistency of both reconstruction procedures. Consistency of the reconstruction procedure based...

  16. Cost Allocation and Convex Data Envelopment

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Tind, Jørgen

    problems involved it becomes clear that the allocation rules, technically speaking, allocate the non-zero value of the dual variable for a convexity constraint on to the output vector. Hence, the allocation rules can also be used to allocate inefficiencies in non-parametric efficiency measurement models...... such as Data Envelopment Analysis (DEA). The convexity constraint of the BCC model introduces a non-zero slack in the objective function of the multiplier problem and we show that the cost allocation rules discussed in this paper can be used as candidates to allocate this slack value on to the input (or output...

  17. Convex functions and the rolling circle criterion

    OpenAIRE

    1995-01-01

    Given 0≤R1≤R2≤∞, CVG(R1,R2) denotes the class of normalized convex functions f in the unit disc U, for which ∂f(U) satisfies a Blaschke Rolling Circles Criterion with radii R1 and R2. Necessary and sufficient conditions for R1=R2, growth and distortion theorems for CVG(R1,R2) and rotation theorem for the class of convex functions of bounded type, are found.

  18. A Complete Characterization of the Gap between Convexity and SOS-Convexity

    CERN Document Server

    Ahmadi, Amir Ali

    2011-01-01

    Our first contribution in this paper is to prove that three natural sum of squares (sos) based sufficient conditions for convexity of polynomials via the definition of convexity, its first order characterization, and its second order characterization are equivalent. These three equivalent algebraic conditions, henceforth referred to as sos-convexity, can be checked by semidefinite programming whereas deciding convexity is NP-hard. If we denote the set of convex and sos-convex polynomials in $n$ variables of degree $d$ with $\\tilde{C}_{n,d}$ and $\\tilde{\\Sigma C}_{n,d}$ respectively, then our main contribution is to prove that $\\tilde{C}_{n,d}=\\tilde{\\Sigma C}_{n,d}$ if and only if $n=1$ or $d=2$ or $(n,d)=(2,4)$. We also present a complete characterization for forms (homogeneous polynomials) except for the case $(n,d)=(3,4)$ which is joint work with G. Blekherman and is to be published elsewhere. Our result states that the set $C_{n,d}$ of convex forms in $n$ variables of degree $d$ equals the set $\\Sigma C_{...

  19. Transducer of linear displacements

    Science.gov (United States)

    Malamed, Y. R.

    1984-02-01

    The basic PLP transducer is designed for a UIM-29 microscope and a 2-coordinate measuring instrument with electronic digital readout. Its optical system consists of an AL-107B light-emitting diode as light source, two condenser lenses, a special wedge carrying two pairs of joined receiver lenses, a prism-mirror, a photoreceiver, a wedge-shape transparent replica of a twin diffraction grating which prevents light reflected by the air-glass interface from focusing on the receiver photodiodes, and a reflective replica of a diffraction grating on a movable carriage. The already available three models of this transducer are PLP1-0.2, PLP1-0.5, and PLP1-1.0 with respectively 625, 250, 125 lines/mm on the transparent replica and respectively 312.5, 125, 62.5 lines/mm on the reflective replica. The scale of moire-interference fringes characterizing the shift between both diffraction gratings per grating period (9.16 mm in each model) is respectively 0.8, 2.0, 4.0 microns and the angle between the two arrays of grating lines on the transparent replica is respectively 36 + or - 4 deg, 90 + or - 10 deg, 190 + or - 20 deg.

  20. Superconducting Qubit Optical Transducer (SQOT)

    Science.gov (United States)

    2015-08-05

    SECURITY CLASSIFICATION OF: The SQOT (Superconducting Qubit Optical Transducer ) project proposes to build a novel electro-optic system which can...Apr-2015 Approved for Public Release; Distribution Unlimited Final Report: "Superconducting Qubit Optical Transducer " (SQOT) The views, opinions and...journals: Number of Papers published in non peer-reviewed journals: Final Report: "Superconducting Qubit Optical Transducer " (SQOT) Report Title The

  1. Miniature multimode monolithic flextensional transducers.

    Science.gov (United States)

    Hladky-Hennion, Anne-Christine; Uzgur, A Erman; Markley, Douglas C; Safari, Ahmad; Cochran, Joe K; Newnham, Robert E

    2007-10-01

    Traditional flextensional transducers classified in seven groups based on their designs have been used extensively in 1-100 kHz range for mine hunting, fish finding, oil explorations, and biomedical applications. In this study, a new family of small, low cost underwater, and biomedical transducers has been developed. After the fabrication of transducers, finite-elements analysis (FEA) was used extensively in order to optimize these miniature versions of high-power, low-frequency flextensional transducer designs to achieve broad bandwidth for both transmitting and receiving, engineered vibration modes, and optimized acoustic directivity patterns. Transducer topologies with various shapes, cross sections, and symmetries can be fabricated through high-volume, low-cost ceramic and metal extrusion processes. Miniaturized transducers posses resonance frequencies in the range of above 1 MHz to below 10 kHz. Symmetry and design of the transducer, polling patterns, driving and receiving electrode geometries, and driving conditions have a strong effect on the vibration modes, resonance frequencies, and radiation patterns. This paper is devoted to small, multimode flextensional transducers with active shells, which combine the advantages of small size and low-cost manufacturing with control of the shape of the acoustic radiation/receive pattern. The performance of the transducers is emphasized.

  2. Foundations of complex analysis in non locally convex spaces function theory without convexity condition

    CERN Document Server

    Bayoumi, A

    2003-01-01

    All the existing books in Infinite Dimensional Complex Analysis focus on the problems of locally convex spaces. However, the theory without convexity condition is covered for the first time in this book. This shows that we are really working with a new, important and interesting field. Theory of functions and nonlinear analysis problems are widespread in the mathematical modeling of real world systems in a very broad range of applications. During the past three decades many new results from the author have helped to solve multiextreme problems arising from important situations, non-convex and

  3. Advanced 3-D Ultrasound Imaging

    DEFF Research Database (Denmark)

    Rasmussen, Morten Fischer

    to produce high quality 3-D images. Because of the large matrix transducers with integrated custom electronics, these systems are extremely expensive. The relatively low price of ultrasound scanners is one of the factors for the widespread use of ultrasound imaging. The high price tag on the high quality 3-D......The main purpose of the PhD project was to develop methods that increase the 3-D ultrasound imaging quality available for the medical personnel in the clinic. Acquiring a 3-D volume gives the medical doctor the freedom to investigate the measured anatomy in any slice desirable after the scan has...... been completed. This allows for precise measurements of organs dimensions and makes the scan more operator independent. Real-time 3-D ultrasound imaging is still not as widespread in use in the clinics as 2-D imaging. A limiting factor has traditionally been the low image quality achievable using...

  4. Tropicalized Lambda Lengths, Measured Laminations and Convexity

    DEFF Research Database (Denmark)

    C. Penner, R.

    cell decomposition of a surface is discovered in the limit. Finally, the tropical analogue of the convex hull construction in Minkowski space is formulated as an explicit algorithm that serially simplifies a triangulation with respect to a fixed lamination and has its own independent applications....

  5. Some Characterizations of Convex Interval Games

    NARCIS (Netherlands)

    Brânzei, R.; Tijs, S.H.; Alparslan-Gok, S.Z.

    2008-01-01

    This paper focuses on new characterizations of convex interval games using the notions of exactness and superadditivity. We also relate big boss interval games with concave interval games and obtain characterizations of big boss interval games in terms of exactness and subadditivity.

  6. A generalization of the convex Kakeya problem

    KAUST Repository

    Ahn, Heekap

    2013-09-19

    Given a set of line segments in the plane, not necessarily finite, what is a convex region of smallest area that contains a translate of each input segment? This question can be seen as a generalization of Kakeya\\'s problem of finding a convex region of smallest area such that a needle can be rotated through 360 degrees within this region. We show that there is always an optimal region that is a triangle, and we give an optimal Θ(nlogn)-time algorithm to compute such a triangle for a given set of n segments. We also show that, if the goal is to minimize the perimeter of the region instead of its area, then placing the segments with their midpoint at the origin and taking their convex hull results in an optimal solution. Finally, we show that for any compact convex figure G, the smallest enclosing disk of G is a smallest-perimeter region containing a translate of every rotated copy of G. © 2013 Springer Science+Business Media New York.

  7. Robust Utility Maximization Under Convex Portfolio Constraints

    Energy Technology Data Exchange (ETDEWEB)

    Matoussi, Anis, E-mail: anis.matoussi@univ-lemans.fr [Université du Maine, Risk and Insurance institut of Le Mans Laboratoire Manceau de Mathématiques (France); Mezghani, Hanen, E-mail: hanen.mezghani@lamsin.rnu.tn; Mnif, Mohamed, E-mail: mohamed.mnif@enit.rnu.tn [University of Tunis El Manar, Laboratoire de Modélisation Mathématique et Numérique dans les Sciences de l’Ingénieur, ENIT (Tunisia)

    2015-04-15

    We study a robust maximization problem from terminal wealth and consumption under a convex constraints on the portfolio. We state the existence and the uniqueness of the consumption–investment strategy by studying the associated quadratic backward stochastic differential equation. We characterize the optimal control by using the duality method and deriving a dynamic maximum principle.

  8. Tropicalized Lambda Lengths, Measured Laminations and Convexity

    DEFF Research Database (Denmark)

    C. Penner, R.

    This work uncovers the tropical analogue for measured laminations of the convex hull construction of decorated Teichmueller theory, namely, it is a study in coordinates of geometric degeneration to a point of Thurston's boundary for Teichmueller space. This may offer a paradigm for the extension...

  9. On fixed points and uniformly convex spaces

    OpenAIRE

    Gelander, Tsachik

    2008-01-01

    The purpose of this note is to present two elementary, but useful, facts concerning actions on uniformly convex spaces. We demonstrate how each of them can be used in an alternative proof of the triviality of the first $L_p$-cohomology of higher rank simple Lie groups, proved in [BFGM].

  10. Dynamic Matchings in Convex Bipartite Graphs

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Georgiadis, Loukas; Hansen, Kristoffer Arnsfelt

    2007-01-01

    We consider the problem of maintaining a maximum matching in a convex bipartite graph G = (V,E) under a set of update operations which includes insertions and deletions of vertices and edges. It is not hard to show that it is impossible to maintain an explicit representation of a maximum matching...

  11. Minimizing convex functions by continuous descent methods

    Directory of Open Access Journals (Sweden)

    Sergiu Aizicovici

    2010-01-01

    Full Text Available We study continuous descent methods for minimizing convex functions, defined on general Banach spaces, which are associated with an appropriate complete metric space of vector fields. We show that there exists an everywhere dense open set in this space of vector fields such that each of its elements generates strongly convergent trajectories.

  12. Differential analysis of matrix convex functions

    DEFF Research Database (Denmark)

    Hansen, Frank; Tomiyama, Jun

    2007-01-01

    We analyze matrix convex functions of a fixed order defined in a real interval by differential methods as opposed to the characterization in terms of divided differences given by Kraus [F. Kraus, Über konvekse Matrixfunktionen, Math. Z. 41 (1936) 18-42]. We obtain for each order conditions for ma...

  13. Estimates for oscillatory integrals with convex phase

    Energy Technology Data Exchange (ETDEWEB)

    Chakhkiev, M A [Moscow State Social University, Moscow (Russian Federation)

    2006-02-28

    We consider methods for estimating one-dimensional oscillatory integrals with convex phase and amplitudes of bounded variation or Lipschitz class amplitudes. In particular, we improve the estimate for the Piercey integral with near-caustic parameter values, and also consider estimation methods for n-dimensional oscillatory integrals.

  14. Some Characterizations of Convex Interval Games

    NARCIS (Netherlands)

    Brânzei, R.; Tijs, S.H.; Alparslan-Gok, S.Z.

    2008-01-01

    This paper focuses on new characterizations of convex interval games using the notions of exactness and superadditivity. We also relate big boss interval games with concave interval games and obtain characterizations of big boss interval games in terms of exactness and subadditivity.

  15. Directional Convexity and Finite Optimality Conditions.

    Science.gov (United States)

    1984-03-01

    system, Necessary Conditions for optimality. Work Unit Number 5 (Optimization and Large Scale Systems) *Istituto di Matematica Applicata, Universita...that R(T) is convex would then imply x(u,T) e int R(T). Cletituto di Matematica Applicata, Universita di Padova, 35100 ITALY. Sponsored by the United

  16. Convex bodies of states and maps

    Science.gov (United States)

    Grabowski, Janusz; Ibort, Alberto; Kuś, Marek; Marmo, Giuseppe

    2013-10-01

    We give a general solution to the question of when the convex hulls of orbits of quantum states on a finite-dimensional Hilbert space under unitary actions of a compact group have a non-empty interior in the surrounding space of all density operators. The same approach can be applied to study convex combinations of quantum channels. The importance of both problems stems from the fact that, usually, only sets with non-vanishing volumes in the embedding spaces of all states or channels are of practical importance. For the group of local transformations on a bipartite system we characterize maximally entangled states by the properties of a convex hull of orbits through them. We also compare two partial characteristics of convex bodies in terms of the largest balls and maximum volume ellipsoids contained in them and show that, in general, they do not coincide. Separable states, mixed-unitary channels and k-entangled states are also considered as examples of our techniques.

  17. Convexity properties of Hamiltonian group actions

    CERN Document Server

    Guillemin, Victor

    2005-01-01

    This is a monograph on convexity properties of moment mappings in symplectic geometry. The fundamental result in this subject is the Kirwan convexity theorem, which describes the image of a moment map in terms of linear inequalities. This theorem bears a close relationship to perplexing old puzzles from linear algebra, such as the Horn problem on sums of Hermitian matrices, on which considerable progress has been made in recent years following a breakthrough by Klyachko. The book presents a simple local model for the moment polytope, valid in the "generic&rdquo case, and an elementary Morse-theoretic argument deriving the Klyachko inequalities and some of their generalizations. It reviews various infinite-dimensional manifestations of moment convexity, such as the Kostant type theorems for orbits of a loop group (due to Atiyah and Pressley) or a symplectomorphism group (due to Bloch, Flaschka and Ratiu). Finally, it gives an account of a new convexity theorem for moment map images of orbits of a Borel sub...

  18. Subset Selection by Local Convex Approximation

    DEFF Research Database (Denmark)

    Øjelund, Henrik; Sadegh, Payman; Madsen, Henrik

    1999-01-01

    least squares criterion. We propose an optimization technique for the posed probelm based on a modified version of the Newton-Raphson iterations, combined with a backward elimination type algorithm. THe Newton-Raphson modification concerns iterative approximations to the non-convex cost function...

  19. Conference on Convex Analysis and Global Optimization

    CERN Document Server

    Pardalos, Panos

    2001-01-01

    There has been much recent progress in global optimization algo­ rithms for nonconvex continuous and discrete problems from both a theoretical and a practical perspective. Convex analysis plays a fun­ damental role in the analysis and development of global optimization algorithms. This is due essentially to the fact that virtually all noncon­ vex optimization problems can be described using differences of convex functions and differences of convex sets. A conference on Convex Analysis and Global Optimization was held during June 5 -9, 2000 at Pythagorion, Samos, Greece. The conference was honoring the memory of C. Caratheodory (1873-1950) and was en­ dorsed by the Mathematical Programming Society (MPS) and by the Society for Industrial and Applied Mathematics (SIAM) Activity Group in Optimization. The conference was sponsored by the European Union (through the EPEAEK program), the Department of Mathematics of the Aegean University and the Center for Applied Optimization of the University of Florida, by th...

  20. A model for the propagation and scattering of ultrasound in tissue

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    1991-01-01

    of the field from typical transducers used in clinical ultrasound to yield a model for the received pulse-echo pressure field. Analytic expressions are found in the literature for a number of transducers, and any transducer excitation can be incorporated into the model. An example is given for a concave......, nonapodized transducer in which the predicted pressure field is compared to a measured field....

  1. Numerical Transducer Modeling

    DEFF Research Database (Denmark)

    Henriquez, Vicente Cutanda

    This thesis describes the development of a numerical model of the propagation of sound waves in fluids with viscous and thermal losses, with application to the simulation of acoustic transducers, in particular condenser microphones for measurement. The theoretical basis is presented, numerical...... tools and implementation techniques are described and performance tests are carried out. The equations that govern the motion of fluids with losses and the corresponding boundary conditions are reduced to a form that is tractable for the Boundary Element Method (BEM) by adopting some hypotheses...... that are allowable in this case: linear variations, absence of flow, harmonic time variation, thermodynamical equilibrium and physical dimensions much larger than the molecular mean free path. A formulation of the BEM is also developed with an improvement designed to cope with the numerical difficulty associated...

  2. Optically transduced MEMS magnetometer

    Science.gov (United States)

    Nielson, Gregory N; Langlois, Eric

    2014-03-18

    MEMS magnetometers with optically transduced resonator displacement are described herein. Improved sensitivity, crosstalk reduction, and extended dynamic range may be achieved with devices including a deflectable resonator suspended from the support, a first grating extending from the support and disposed over the resonator, a pair of drive electrodes to drive an alternating current through the resonator, and a second grating in the resonator overlapping the first grating to form a multi-layer grating having apertures that vary dimensionally in response to deflection occurring as the resonator mechanically resonates in a plane parallel to the first grating in the presence of a magnetic field as a function of the Lorentz force resulting from the alternating current. A plurality of such multi-layer gratings may be disposed across a length of the resonator to provide greater dynamic range and/or accommodate fabrication tolerances.

  3. Electromagnetic acoustic transducer

    Science.gov (United States)

    Alers, George A.; Burns, Jr., Leigh R.; MacLauchlan, Daniel T.

    1988-01-01

    A noncontact ultrasonic transducer for studying the acoustic properties of a metal workpiece includes a generally planar magnetizing coil positioned above the surface of the workpiece, and a generally planar eddy current coil between the magnetizing coil and the workpiece. When a large current is passed through the magnetizing coil, a large magnetic field is applied to the near-surface regions of the workpiece. The eddy current coil can then be operated as a transmitter by passing an alternating current therethrough to excite ultrasonic waves in the surface of the workpiece, or operated as a passive receiver to sense ultrasonic waves in the surface by measuring the output signal. The geometries of the two coils can be varied widely to be effective for different types of ultrasonic waves. The coils are preferably packaged in a housing which does not interfere with their operation, but protects them from a variety of adverse environmental conditions.

  4. Relations between Lipschitz functions and convex functions

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    [1]Zajicek, J., On the differentation of convex functions in finite and infinite dimensional spaces, Czech J. Math.,1979, 29: 340-348.[2]Hu, T. C., Klee, V. L., Larman, D. G., Optimization of globally convex functions, SIAM J. Control Optim., 1989,27: 1026-1047.[3]Cepedello Boiso, M., Approximation of Lipschitz functions by △-convex functions in Banach spaces, Israel J.Math., 1998, 106: 269-284.[4]Asplund, E., Frechet differentiability of convex functions, Acta Math., 1968, 121: 31-47.[5]Johnson, J. A., Lipschitz spaces, Pacific J. Math, 1974, 51: 177-186.[6]Stromberg, T., The operation of infimal convolution, Dissert. Math., (Rozprawy Mat.), 1996, 325: 58.[7]Kadison, R. V., Ringrose, J. R., Fundamentals of the theory of operator algebras, volume Ⅰ: Elementary Theory,Graduate Studies in Math., vol. 15, Amer. Math. Soc., 1997.[8]Phelps, R. R., Convex functions,monotone operators and differentiability, Lect. Notes in Math., vol. 1364,Springer-Verlag, 1977.[9]Lindenstrauss, J., On operators which attain their norm, Israel J. Math., 1963, 1: 139-148.[10]Press, D., Gateaux differentiable functions are somewhere Frechet differentiable, Rend. Circ. Mat. Palermo,1984, 33: 122-133.[11]Press, D., Differentiability of Lipschitz functions on Banach spaces, J. Funct. Anal., 1990, 91:312-345.[12]Lindenstrauss, J., Press, D., On Frechet differentiability of Lipschitz maps between Banach spaces, Annals of Math., 2003, 157: 257-288.[13]Press, D., Gateaux differentiable Lipschitz functions need not be Frechet differentiable on a residual set, Supplemento Rend. Circ. Mat. Palermo, Serie Ⅱ, 1982, 2: 217-222.

  5. Fast approximate convex decomposition using relative concavity

    KAUST Repository

    Ghosh, Mukulika

    2013-02-01

    Approximate convex decomposition (ACD) is a technique that partitions an input object into approximately convex components. Decomposition into approximately convex pieces is both more efficient to compute than exact convex decomposition and can also generate a more manageable number of components. It can be used as a basis of divide-and-conquer algorithms for applications such as collision detection, skeleton extraction and mesh generation. In this paper, we propose a new method called Fast Approximate Convex Decomposition (FACD) that improves the quality of the decomposition and reduces the cost of computing it for both 2D and 3D models. In particular, we propose a new strategy for evaluating potential cuts that aims to reduce the relative concavity, rather than absolute concavity. As shown in our results, this leads to more natural and smaller decompositions that include components for small but important features such as toes or fingers while not decomposing larger components, such as the torso, that may have concavities due to surface texture. Second, instead of decomposing a component into two pieces at each step, as in the original ACD, we propose a new strategy that uses a dynamic programming approach to select a set of n c non-crossing (independent) cuts that can be simultaneously applied to decompose the component into n c+1 components. This reduces the depth of recursion and, together with a more efficient method for computing the concavity measure, leads to significant gains in efficiency. We provide comparative results for 2D and 3D models illustrating the improvements obtained by FACD over ACD and we compare with the segmentation methods in the Princeton Shape Benchmark by Chen et al. (2009) [31]. © 2012 Elsevier Ltd. All rights reserved.

  6. On the convexity of N-Chebyshev sets

    Science.gov (United States)

    Borodin, Petr A.

    2011-10-01

    We define N-Chebyshev sets in a Banach space X for every positive integer N (when N=1, these are ordinary Chebyshev sets) and study conditions that guarantee their convexity. In particular, we prove that all N-Chebyshev sets are convex when N is even and X is uniformly convex or N\\ge 3 is odd and X is smooth uniformly convex.

  7. The Identification of Convex Function on Riemannian Manifold

    Directory of Open Access Journals (Sweden)

    Li Zou

    2014-01-01

    Full Text Available The necessary and sufficient condition of convex function is significant in nonlinear convex programming. This paper presents the identification of convex function on Riemannian manifold by use of Penot generalized directional derivative and the Clarke generalized gradient. This paper also presents a method for judging whether a point is the global minimum point in the inequality constraints. Our objective here is to extend the content and proof the necessary and sufficient condition of convex function to Riemannian manifolds.

  8. ON THE PRODUCT OF GATEAUX DIFFERENTIABILITY LOCALLY CONVEX SPACES

    Institute of Scientific and Technical Information of China (English)

    Shen Xisheng; Cheng Lixin

    2005-01-01

    A locally convex space is said to be a Gateaux differentiability space (GDS)provided every continuous convex function defined on a nonempty convex open subset D of the space is densely Gateaux differentiable in D.This paper shows that the product of a GDS and a family of separable Frechet spaces is a GDS,and that the product of a GDS and an arbitrary locally convex space endowed with the weak topology is a GDS.

  9. Calibration of Underwater Sound Transducers

    Directory of Open Access Journals (Sweden)

    H.R.S. Sastry

    1983-07-01

    Full Text Available The techniques of calibration of underwater sound transducers for farfield, near-field and closed environment conditions are reviewed in this paper .The design of acoustic calibration tank is mentioned. The facilities available at Naval Physical & Oceanographic Laboratory, Cochin for calibration of transducers are also listed.

  10. On a New Optical Transducer

    Directory of Open Access Journals (Sweden)

    Cornel Bit

    2015-07-01

    Full Text Available This paper presents a new type of mechano – optical force transducer which to be used in different mechanical experimental investigations. This transducer has been integrated within a mechanical modulus, providing a useful tool for this kind of measurements. The use of optical methods for the elastic contact measurements has several important advantages.

  11. Bubble sorting in pinched microchannels for ultrasound contrast agent enrichment

    NARCIS (Netherlands)

    Kok, M.P.; Segers, T.J.; Versluis, M.

    2015-01-01

    Ultrasound contrast agent (UCA) suspensions contain encapsulated microbubbles with a wide size distribution, with radii between 1 and 10 μm. Medical transducers generally operate at a narrow frequency bandwidth, severely limiting the fraction of bubbles that resonates to the driving ultrasound. Thus

  12. In Vivo Real Time Volumetric Synthetic Aperture Ultrasound Imaging

    DEFF Research Database (Denmark)

    Bouzari, Hamed; Rasmussen, Morten Fischer; Brandt, Andreas Hjelm;

    2015-01-01

    Synthetic aperture (SA) imaging can be used to achieve real-time volumetric ultrasound imaging using 2-D array transducers. The sensitivity of SA imaging is improved by maximizing the acoustic output, but one must consider the limitations of an ultrasound system, both technical and biological...

  13. An Enhanced Fuselage Ultrasound Inspection Approach for ISHM Purposes

    Science.gov (United States)

    2012-03-01

    ultrasound (see Figure 12). Figure 12: Omni-directional Piezoelectric Transducer Piezoelectricity is an electric polarization effect due to mechanical...Fatigue Management Program bdd [SysML Block Definition] Design Model [Design Model] Specific Program for Each Fleet Ultrasound on- board

  14. Allometric relationships between traveltime channel networks, convex hulls, and convexity measures

    Science.gov (United States)

    Tay, Lea Tien; Sagar, B. S. Daya; Chuah, Hean Teik

    2006-06-01

    The channel network (S) is a nonconvex set, while its basin [C(S)] is convex. We remove open-end points of the channel connectivity network iteratively to generate a traveltime sequence of networks (Sn). The convex hulls of these traveltime networks provide an interesting topological quantity, which has not been noted thus far. We compute lengths of shrinking traveltime networks L(Sn) and areas of corresponding convex hulls C(Sn), the ratios of which provide convexity measures CM(Sn) of traveltime networks. A statistically significant scaling relationship is found for a model network in the form L(Sn) ˜ A[C(Sn)]0.57. From the plots of the lengths of these traveltime networks and the areas of their corresponding convex hulls as functions of convexity measures, new power law relations are derived. Such relations for a model network are CM(Sn) ˜ ? and CM(Sn) ˜ ?. In addition to the model study, these relations for networks derived from seven subbasins of Cameron Highlands region of Peninsular Malaysia are provided. Further studies are needed on a large number of channel networks of distinct sizes and topologies to understand the relationships of these new exponents with other scaling exponents that define the scaling structure of river networks.

  15. Reverse convex problems: an approach based on optimality conditions

    Directory of Open Access Journals (Sweden)

    Ider Tseveendorj

    2006-01-01

    Full Text Available We present some results concerning reverse convex problems. Global optimality conditions for the problems with a nonsmooth reverse convex constraint are established and convergence of an algorithm in the case of linear program with an additional quadratic reverse convex constraint is studied.

  16. On Quasi E-Convex Bilevel Programming Problem

    Directory of Open Access Journals (Sweden)

    E. A. Youness

    2005-01-01

    Full Text Available Bilevel programming problems involve two optimization problems where the data of the first one is implicity determined by the solution of the second. This study introduces the notions of E-convexity and quasi E-convexity in bilevel programming problems to generalize quasi convex bilevel programming problems.

  17. Reverse convex problems: an approach based on optimality conditions

    OpenAIRE

    Ider Tseveendorj

    2006-01-01

    We present some results concerning reverse convex problems. Global optimality conditions for the problems with a nonsmooth reverse convex constraint are established and convergence of an algorithm in the case of linear program with an additional quadratic reverse convex constraint is studied.

  18. Finite element analysis of hysteresis effects in piezoelectric transducers

    Science.gov (United States)

    Simkovics, Reinhard; Landes, Hermann; Kaltenbacher, Manfred; Hoffelner, Johann; Lerch, Reinhard

    2000-06-01

    The design of ultrasonic transducers for high power applications, e.g. in medical therapy or production engineering, asks for effective computer aided design tools to analyze the occurring nonlinear effects. In this paper the finite-element-boundary-element package CAPA is presented that allows to model different types of electromechanical sensors and actuators. These transducers are based on various physical coupling effects, such as piezoelectricity or magneto- mechanical interactions. Their computer modeling requires the numerical solution of a multifield problem, such as coupled electric-mechanical fields or magnetic-mechanical fields as well as coupled mechanical-acoustic fields. With the reported software environment we are able to compute the dynamic behavior of electromechanical sensors and actuators by taking into account geometric nonlinearities, nonlinear wave propagation and ferroelectric as well as magnetic material nonlinearities. After a short introduction to the basic theory of the numerical calculation schemes, two practical examples will demonstrate the applicability of the numerical simulation tool. As a first example an ultrasonic thickness mode transducer consisting of a piezoceramic material used for high power ultrasound production is examined. Due to ferroelectric hysteresis, higher order harmonics can be detected in the actuators input current. Also in case of electrical and mechanical prestressing a resonance frequency shift occurs, caused by ferroelectric hysteresis and nonlinear dependencies of the material coefficients on electric field and mechanical stresses. As a second example, a power ultrasound transducer used in HIFU-therapy (high intensity focused ultrasound) is presented. Due to the compressibility and losses in the propagating fluid a nonlinear shock wave generation can be observed. For both examples a good agreement between numerical simulation and experimental data has been achieved.

  19. Study on Enhancement Effect of Cavitation Caused by HIFU Piezoelectricity Transducer

    Institute of Scientific and Technical Information of China (English)

    Xinnan Fan; Changping Zhu; Shichuan He; Minglei Shan; Jiacai Chen

    2006-01-01

    An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper. Effect of cavitation was detected by pH-value measurement and conductance measurement. The result shows that the effect of cavitation caused by ultrasound with frequency at 28 kHz is greatly enhanced by HIFU piezoelectricity transducer with frequency at 1.05 MHz.

  20. Circuit for Driving Piezoelectric Transducers

    Science.gov (United States)

    Randall, David P.; Chapsky, Jacob

    2009-01-01

    The figure schematically depicts an oscillator circuit for driving a piezoelectric transducer to excite vibrations in a mechanical structure. The circuit was designed and built to satisfy application-specific requirements to drive a selected one of 16 such transducers at a regulated amplitude and frequency chosen to optimize the amount of work performed by the transducer and to compensate for both (1) temporal variations of the resonance frequency and damping time of each transducer and (2) initially unknown differences among the resonance frequencies and damping times of different transducers. In other words, the circuit is designed to adjust itself to optimize the performance of whichever transducer is selected at any given time. The basic design concept may be adaptable to other applications that involve the use of piezoelectric transducers in ultrasonic cleaners and other apparatuses in which high-frequency mechanical drives are utilized. This circuit includes three resistor-capacitor networks that, together with the selected piezoelectric transducer, constitute a band-pass filter having a peak response at a frequency of about 2 kHz, which is approximately the resonance frequency of the piezoelectric transducers. Gain for generating oscillations is provided by a power hybrid operational amplifier (U1). A junction field-effect transistor (Q1) in combination with a resistor (R4) is used as a voltage-variable resistor to control the magnitude of the oscillation. The voltage-variable resistor is part of a feedback control loop: Part of the output of the oscillator is rectified and filtered for use as a slow negative feedback to the gate of Q1 to keep the output amplitude constant. The response of this control loop is much slower than 2 kHz and, therefore, does not introduce significant distortion of the oscillator output, which is a fairly clean sine wave. The positive AC feedback needed to sustain oscillations is derived from sampling the current through the

  1. Design parameter investigation of industrial size ultrasound textile treatment bath.

    Science.gov (United States)

    Perincek, Seher; Uzgur, A Erman; Duran, Kerim; Dogan, Aydin; Korlu, Aysegul E; Bahtiyari, Ibrahim M

    2009-01-01

    Design requirements for industrial size ultrasound bath for textile treatments have been determined. For this purpose, effects of sound pressure level, bath temperature, bath volume, textile material type and hydrophility degree of fabric were examined extensively. Finite element analysis (FEA) was used to investigate spacing and alignment of the ultrasound source transducers to reach effective and homogenous acoustic pressure distribution in the bath. It was found that textile material type, bath temperature and volume led to significant changes at sound pressure level. These parameters should be taken into consideration in designing of industrial size ultrasound bath for textile treatments. Besides, wettability of textiles is highly dependent to the distance from the transducers.

  2. Measurement of a PAGAT gel dosimeter by ultrasound computed tomography

    Science.gov (United States)

    Khoei, S.; Trapp, J. V.; Langton, C. M.

    2013-06-01

    In this work we used a 3D quantitative CT ultrasound imaging system to characterise polymer gel dosimeters. The system comprised of two identical 5 MHz 128 element phased-array ultrasound transducers co-axially aligned and submerged in water as a coupling agent. Rotational and translational movement of the gel dosimeter sample between the transducers were performed using a robotic arm. Ultrasound signals were generated and received using an Olympus Omniscan unit. Dose sensitivity of attenuation and time of flight ultrasonic parameters were assessed using this system.

  3. A Generalization of Uniformly Extremely Convex Banach Spaces

    OpenAIRE

    Suyalatu Wulede; Wurichaihu Bai; Wurina Bao

    2016-01-01

    We discuss a new class of Banach spaces which are the generalization of uniformly extremely convex spaces introduced by Wulede and Ha. We prove that the new class of Banach spaces lies strictly between either the classes of k-uniformly rotund spaces and k-strongly convex spaces or classes of fully k-convex spaces and k-strongly convex spaces and has no inclusive relation with the class of locally k-uniformly convex spaces. We obtain in addition some characterizations and properties of this ne...

  4. The heart of a convex body

    CERN Document Server

    Brasco, Lorenzo

    2012-01-01

    We investigate some basic properties of the {\\it heart} $\\heartsuit(\\mathcal{K})$ of a convex set $\\mathcal{K}.$ It is a subset of $\\mathcal{K},$ whose definition is based on mirror reflections of euclidean space, and is a non-local object. The main motivation of our interest for $\\heartsuit(\\mathcal{K})$ is that this gives an estimate of the location of the hot spot in a convex heat conductor with boundary temperature grounded at zero. Here, we investigate on the relation between $\\heartsuit(\\mathcal{K})$ and the mirror symmetries of $\\mathcal{K};$ we show that $\\heartsuit(\\mathcal{K})$ contains many (geometrically and phisically) relevant points of $\\mathcal{K};$ we prove a simple geometrical lower estimate for the diameter of $\\heartsuit(\\mathcal{K});$ we also prove an upper estimate for the area of $\\heartsuit(\\mathcal{K}),$ when $\\mathcal{K}$ is a triangle.

  5. Coalescence between two convex liquid surfaces

    Science.gov (United States)

    Yang, Fan; Jian, Zhen; Li, Erqiang; Thoroddsen, S. T.

    2015-11-01

    We study the coalescence of two convex surfaces of the same liquid. One of the convex free surfaces is formed at a circular opening of a closed tank by imposing a negative pressure difference. The other surface is a droplet of larger curvature, which is pendant from a concentric nozzle. The coalescence starts from near-zero velocity, so the configuration can be characterized by two dimensionless numbers: the Ohnesorge number Oh = μ /√{ ργL } and the radius ratio between the two surfaces α =rd /rs . We use high-speed video, PIV and numerical simulations, using the Gerris program, to study the dynamics of the coalescence. Our focus is on the interface shapes, the growth-rate of the neck connecting the two surfaces and the formation of a vortex ring. The growth-rate is compared to earlier models for the coalescence of drops or bubbles.

  6. Convex Modeling of Interactions with Strong Heredity

    Science.gov (United States)

    Haris, Asad; Witten, Daniela; Simon, Noah

    2015-01-01

    We consider the task of fitting a regression model involving interactions among a potentially large set of covariates, in which we wish to enforce strong heredity. We propose FAMILY, a very general framework for this task. Our proposal is a generalization of several existing methods, such as VANISH [Radchenko and James, 2010], hierNet [Bien et al., 2013], the all-pairs lasso, and the lasso using only main effects. It can be formulated as the solution to a convex optimization problem, which we solve using an efficient alternating directions method of multipliers (ADMM) algorithm. This algorithm has guaranteed convergence to the global optimum, can be easily specialized to any convex penalty function of interest, and allows for a straightforward extension to the setting of generalized linear models. We derive an unbiased estimator of the degrees of freedom of FAMILY, and explore its performance in a simulation study and on an HIV sequence data set. PMID:28316461

  7. Convex Arrhenius plots and their interpretation

    Science.gov (United States)

    Truhlar, Donald G.; Kohen, Amnon

    2001-01-01

    This paper draws attention to selected experiments on enzyme-catalyzed reactions that show convex Arrhenius plots, which are very rare, and points out that Tolman's interpretation of the activation energy places a fundamental model-independent constraint on any detailed explanation of these reactions. The analysis presented here shows that in such systems, the rate coefficient as a function of energy is not just increasing more slowly than expected, it is actually decreasing. This interpretation of the data provides a constraint on proposed microscopic models, i.e., it requires that any successful model of a reaction with a convex Arrhenius plot should be consistent with the microcanonical rate coefficient being a decreasing function of energy. The implications and limitations of this analysis to interpreting enzyme mechanisms are discussed. This model-independent conclusion has broad applicability to all fields of kinetics, and we also draw attention to an analogy with diffusion in metastable fluids and glasses. PMID:11158559

  8. Passive wireless ultrasonic transducer systems

    Science.gov (United States)

    Zhong, C. H.; Croxford, A. J.; Wilcox, P. D.

    2014-02-01

    Inductive coupling and capacitive coupling both offer simple solutions to wirelessly probe ultrasonic transducers. This paper investigates the theory and feasibility of such system in the context of non-destructive evaluation (NDE) applications. Firstly, the physical principles and construction of an inductively coupled transducer system (ICTS) and a capacitively coupled transducer system (CCTS) are introduced. Then the development of a transmission line model with the measured impedance of a bonded piezoelectric ceramic disc representing a sensor attached to an arbitrary solid substrate for both systems is described. The models are validated experimentally. Several applications of CCTS are presented, such CCTS for the underwater and through-composite testing.

  9. On the convexity of Relativistic Hydrodynamics

    CERN Document Server

    Ibáñez, José María; Martí, José María; Miralles, Juan Antonio; 10.1088/0264-9381/30/5/057002

    2013-01-01

    The relativistic hydrodynamic system of equations for a perfect fluid obeying a causal equation of state is hyperbolic (Anile 1989 {\\it Relativistic Fluids and Magneto-Fluids} (Cambridge: Cambridge University Press)). In this report, we derive the conditions for this system to be convex in terms of the fundamental derivative of the equation of state (Menikoff and Plohr 1989 {\\it Rev. Mod. Phys.} {\\bf 61} 75). The classical limit is recovered.

  10. Coefficient inequalities for starlikeness and convexity

    Directory of Open Access Journals (Sweden)

    Ali Rosihan M.

    2013-06-01

    Full Text Available For an analytic function $f(z=z+\\sum_{n=2}^\\infty a_n z^n$ satisfying the inequality $\\sum_{n=2}^\\infty n(n-1|a_n|\\leq \\beta$, sharp bound on $\\beta$ is determined so that $f$ is either starlike or convex of order $\\alpha$. Several other coefficient inequalities related to certain subclasses are also investigated.

  11. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique.

    Directory of Open Access Journals (Sweden)

    Samuel Pichardo

    Full Text Available Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13:135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode. The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d. resonance frequency of the samples was 465.1 (± 1.5 kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field.

  12. When is multidimensional screening a convex program?

    CERN Document Server

    Figalli, Alessio; McCann, Robert J

    2009-01-01

    A principal wishes to transact business with a multidimensional distribution of agents whose preferences are known only in the aggregate. Assuming a twist (= generalized Spence-Mirrlees single-crossing) hypothesis and that agents can choose only pure strategies, we identify a structural condition on the preference b(x,y) of agent type x for product type y -- and on the principal's costs c(y) -- which is necessary and sufficient for reducing the profit maximization problem faced by the principal to a convex program. This is a key step toward making the principal's problem theoretically and computationally tractable; in particular, it allows us to derive uniqueness and stability of the principal's optimum strategy -- and similarly of the strategy maximizing the expected welfare of the agents when the principal's profitability is constrained. We call this condition non-negative cross-curvature: it is also (i) necessary and sufficient to guarantee convexity of the set of b-convex functions, (ii) invariant under r...

  13. On convex relaxation of graph isomorphism.

    Science.gov (United States)

    Aflalo, Yonathan; Bronstein, Alexander; Kimmel, Ron

    2015-03-10

    We consider the problem of exact and inexact matching of weighted undirected graphs, in which a bijective correspondence is sought to minimize a quadratic weight disagreement. This computationally challenging problem is often relaxed as a convex quadratic program, in which the space of permutations is replaced by the space of doubly stochastic matrices. However, the applicability of such a relaxation is poorly understood. We define a broad class of friendly graphs characterized by an easily verifiable spectral property. We prove that for friendly graphs, the convex relaxation is guaranteed to find the exact isomorphism or certify its inexistence. This result is further extended to approximately isomorphic graphs, for which we develop an explicit bound on the amount of weight disagreement under which the relaxation is guaranteed to find the globally optimal approximate isomorphism. We also show that in many cases, the graph matching problem can be further harmlessly relaxed to a convex quadratic program with only n separable linear equality constraints, which is substantially more efficient than the standard relaxation involving n2 equality and n2 inequality constraints. Finally, we show that our results are still valid for unfriendly graphs if additional information in the form of seeds or attributes is allowed, with the latter satisfying an easy to verify spectral characteristic.

  14. Prostate Ultrasound

    Medline Plus

    Full Text Available ... as detailed as with the transrectal probe. An MRI of the pelvis may be obtained as an ... Benign Prostatic Hyperplasia (BPH) Prostate Cancer Ultrasound- and MRI-Guided Prostate Biopsy Images related to Ultrasound - Prostate ...

  15. Prostate Ultrasound

    Medline Plus

    Full Text Available ... is done because a potential abnormality needs further evaluation with additional views or a special imaging technique. ... other imaging methods. Ultrasound imaging uses no ionizing radiation. Ultrasound scanning may be able to give a ...

  16. Ultrasound -- Pelvis

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    Full Text Available ... needles are used to extract a sample of cells from organs for laboratory testing. Doppler ultrasound images ... ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of ...

  17. Ultrasound -- Pelvis

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    Full Text Available ... the procedure? In women, a pelvic ultrasound is most often performed to evaluate the: uterus cervix ovaries ... page How is the procedure performed? Transabdominal: For most ultrasound exams, you will be positioned lying face- ...

  18. Ultrasound -- Pelvis

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    Full Text Available ... menstrual problems Ultrasound exams also help identify: palpable masses such as ovarian cysts and uterine fibroids ovarian ... In children, pelvic ultrasound can help evaluate: pelvic masses pelvic pain ambiguous genitalia and anomalies of pelvic ...

  19. Ultrasound -- Pelvis

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    Full Text Available ... bladder seminal vesicles prostate Transrectal ultrasound, a special study usually done to provide detailed evaluation of the ... time to the procedure. If a Doppler ultrasound study is performed, you may actually hear pulse-like ...

  20. Ultrasound -- Pelvis

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    Full Text Available ... of page What are some common uses of the procedure? In women, a pelvic ultrasound is most ... child's favorite channel. top of page What does the equipment look like? Ultrasound scanners consist of a ...

  1. Ultrasound -- Pelvis

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    Full Text Available ... ultrasound: abdominal, vaginal (for women), and rectal (for men). These exams are frequently used to evaluate the ... vaginal ( transvaginal , endovaginal ) for women rectal ( transrectal ) for men A Doppler ultrasound exam may be part of ...

  2. Ultrasound -- Pelvis

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    Full Text Available ... ultrasound: abdominal, vaginal (for women), and rectal (for men). These exams are frequently used to evaluate the ... vaginal ( transvaginal / endovaginal ) for women rectal ( transrectal ) for men A Doppler ultrasound exam may be part of ...

  3. Prostate Ultrasound

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  4. Ultrasound -- Pelvis

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    Full Text Available ... insertion. top of page How does the procedure work? Ultrasound imaging is based on the same principles ... to-use and less expensive than other imaging methods. Ultrasound imaging is extremely safe and does not ...

  5. Prostate Ultrasound

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    Full Text Available ... top of page What are the benefits vs. risks? Benefits Ultrasound is widely available, easy-to-use ... procedures such as needle biopsies and fluid aspiration. Risks For standard diagnostic ultrasound , there are no known ...

  6. Ultrasound -- Pelvis

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    Full Text Available ... diagnose symptoms experienced by women such as: pelvic pain abnormal vaginal bleeding other menstrual problems Ultrasound exams ... pelvic ultrasound can help evaluate: pelvic masses pelvic pain ambiguous genitalia and anomalies of pelvic organs early ...

  7. Ultrasound -- Pelvis

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    Full Text Available ... Most ultrasound scanning is noninvasive (no needles or injections). Occasionally, an ultrasound exam may be temporarily uncomfortable, ... the following text box: Comment: E-mail: Area code: Phone no: Thank you! Images × Image Gallery Radiologist ...

  8. Ultrasound -- Pelvis

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    Full Text Available ... investigation of the uterine cavity . Three-dimensional (3-D) ultrasound permits evaluation of the uterus and ovaries ... abnormal uterine bleeding Some physicians also use 3-D ultrasound or sonohysterography for patients with infertility. Three- ...

  9. Ultrasound -- Pelvis

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    Full Text Available ... For most ultrasound exams, you will be positioned lying face-up on an examination table that can ... ovaries. Transvaginal ultrasound is usually performed with you lying on your back, possibly with your feet in ...

  10. Ultrasound -- Pelvis

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    Full Text Available ... investigation of the uterine cavity . Three-dimensional (3-D) ultrasound permits evaluation of the uterus and ovaries ... abnormal uterine bleeding Some physicians also use 3-D ultrasound or sonohysterography for patients with infertility. In ...

  11. Endoscopic ultrasound

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/007646.htm Endoscopic ultrasound To use the sharing features on this page, please enable JavaScript. Endoscopic ultrasound is a type of imaging test. It is ...

  12. Prostate Ultrasound

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    Full Text Available ... evaluation with additional views or a special imaging technique. A follow-up examination may also be necessary ... to-use and less expensive than other imaging methods. Ultrasound imaging uses no ionizing radiation. Ultrasound scanning ...

  13. Ultrasound -- Pelvis

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    Full Text Available ... by women such as: pelvic pain abnormal vaginal bleeding other menstrual problems Ultrasound exams also help identify: ... fibroids cancer, especially in patients with abnormal uterine bleeding Some physicians also use 3-D ultrasound or ...

  14. Ultrasound -- Pelvis

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    Full Text Available ... insertion. top of page How does the procedure work? Ultrasound imaging is based on the same principles ... time to the procedure. If a Doppler ultrasound study is performed, you may actually hear pulse-like ...

  15. Ultrasound -- Pelvis

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    Full Text Available ... in x-rays ), thus there is no radiation exposure to the patient. Because ultrasound images are captured ... system disorders in both sexes without x-ray exposure. Risks For standard diagnostic ultrasound , there are no ...

  16. Ultrasound -- Pelvis

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    Full Text Available ... needles are used to extract a sample of cells from organs for laboratory testing. Doppler ultrasound images ... ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of ...

  17. Prostate Ultrasound

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    Full Text Available ... ultrasound images are captured in real-time, they can show the structure and movement of the body's ... Because ultrasound provides real-time images, it also can be used to guide procedures such as needle ...

  18. Ultrasound -- Pelvis

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    Full Text Available ... ultrasound: abdominal, vaginal (for women), and rectal (for men). These exams are frequently used to evaluate the ... vaginal ( transvaginal / endovaginal ) for women rectal ( transrectal ) for men A Doppler ultrasound exam may be part of ...

  19. Ultrasound -- Pelvis

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    Full Text Available ... Ultrasound is safe, noninvasive and does not use ionizing radiation. This procedure requires little to no special preparation. ... create an image. Ultrasound examinations do not use ionizing radiation (as used in x-rays ), thus there is ...

  20. Ultrasound -- Pelvis

    Medline Plus

    Full Text Available ... and fluid aspiration. Pelvic ultrasound can help to identify and evaluate a variety of urinary and reproductive system disorders in both sexes without x-ray exposure. Risks For standard diagnostic ultrasound , there are no known ...