By Topic

Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 1 • Date Jan. 1994

Filter Results

Displaying Results 1 - 22 of 22
  • Bidirectional Doppler signal analysis based on a single RF sampling channel

    Page(s): 1 - 3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB)  

    Recent introductions of low-cost high-performance devices have finally made feasible the implementation of "undersampling" techniques in different application areas. A significant example is represented by Doppler analysis, which typically involves the inspection of narrowband spectra around an RF carrier. This letter describes the implementation of an aliasing-free CW ultrasound Doppler system employing a "single" undersampling channel, in place of the two "quadrature" sampling channels already proposed by other authors. Implications in terms of clutter rejection are also discussed.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • (Electro-) mechanical characteristics of electrostatically driven vacuum encapsulated polysilicon resonators

    Page(s): 4 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB)  

    The design, fabrication and performance of vacuum-encapsulated electrostatically driven polysilicon resonating beams, 210-510 /spl mu/m long, 100 /spl mu/m wide, and 1.5 /spl mu/m thick, are described. The shortest beams have a fundamental frequency of 324 kHz, a gauge factor of 2400 and a quality factor of 600 at cavity pressures of 0.15 mbar. Intrinsic quality factors of 18000 were measured below 0.01 mbar.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Graphical simulation of superluminal acoustic localized wave pulses

    Page(s): 7 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    This paper investigates, graphically, a simulation of the launching of recently obtained superluminal localized wave solutions of the homogeneous wave equation. These solutions represent focused interference patterns that travel with speed greater than c in the direction of propagation. Graphical simulation indicates that approximations to these solutions may be launched from a finite array of point sources, and the superluminal nature of the launched pulses is maintained in the near field of the array.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coupled-mode analysis of Love waves in a filter film with periodically corrugated surfaces

    Page(s): 13 - 18
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (473 KB)  

    Mode coupling of Love waves in an orthotropic thin film having periodically corrugated surfaces over an isotropic elastic half space is considered. Six modes are coupled by both surfaces by means of three simultaneous resonant conditions. On the basis of the weakness of the corrugations, the method of multiple scales is used to derive the coupled-mode equations. These equations together with relevant boundary conditions form a two-point boundary-value problem, which is solved numerically. The filter frequency response of a corrugated film designed as a stop-band filter is calculated. Enhanced filter characteristics are achieved when tapered corrugations are imposed. A narrow pass-band filter is also designed. Its high quality factor presents the fascinating features that might be realized by including the periodic corrugations in the design of SAW devices.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A facet ensemble approach for evaluation of array performance in ultrasonic NDE

    Page(s): 19 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB)  

    The use of ultrasonic array systems, in conjunction with a synthetic aperture focusing technique (SAFT) has recognized potential for flaw characterization in nondestructive evaluation (NDE). However, defect type, location, orientation and geometrical constraints imposed by the test specimen can reduce the effectiveness of nonoptimal array systems. To assist with design, a simulation approach for evaluation of array performance for NDE imaging was developed and is described in this paper. In the development of the model, several key factors were identified as being critical in defining the response of a linear ultrasonic transducer array. These include the ultrasonic wavelet generated by each array element, the directivity of the transducers and the interaction of the ultrasonic wave field with the surface which is to be imaged. Following several simplifying assumptions, and employing a linear systems approach, the cumulative response of all these factors was formulated. Thus a low-cost, yet powerful, interactive model for system design evaluation could be implemented. To illustrate the model, a range of simulation results is presented, concerning the imaging of a fatigue crack in a solid medium. The influence of array element spacing and centre frequency is considered, in conjunction with aperture size, defect orientation and surface roughness. In each case, the principal factors governing final image quality are discussed and where possible, recommendations are made concerning array design and imaging strategy.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic nondestructive evaluation of highly scattering materials using adaptive filtering and detection

    Page(s): 26 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (775 KB)  

    Adaptive filtering and detection has been applied to the problem of detecting ultrasonic echo signals from test targets where the wanted signals are masked by coherent scattering from grain boundaries present in highly scattering materials. The filter is based on the normalized least mean square (LMS) error algorithm, and can be operated with either an independent reference signal or by using the delayed input signal as the reference. Tests made on a collection of 64 ultrasonic A-scans using the same processing parameters show that an up to 10 dB improvement in signal-to-noise ratio can typically be obtained. A cell-averaging constant false alarm rate (CFAR) detector is used to detect the signals automatically. The performance of the method is compared to that of split spectrum processing, both with and without polarity thresholding.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Phase aberration correction and motion compensation for ultrasonic hyperthermia phased arrays: experimental results

    Page(s): 34 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (889 KB)  

    In ultrasound hyperthermia, focal patterns generated by phased arrays can be degraded by phase errors due to tissue inhomogeneities, digitization of the driving signals, and imperfect fabrication of the transducers. The degree of degradation depends on the severity of phase aberrations. As predicted by simulation and verified by experimental results, focal degradation scales with the circular variance of phase errors. However, degraded power deposition patterns can be significantly improved after phase aberration correction, especially where patterns are complicated and the aberrations are severe. Also, as shown in motion compensation experiments, an aberration corrected pattern can be particularly sensitive to aberrator movement greater than the correlation length of the aberrator. After motion compensation, new sharply focused patterns can be accomplished, thus reducing the unwanted influence of "body" movement by stabilizing the positions of foci with respect to patient anatomy.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Real-time angular scatter imaging system for improved tissue contrast in diagnostic ultrasound images

    Page(s): 44 - 52
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB)  

    A new type of real-time ultrasound imaging system has been developed. In contrast to conventional systems, which process only echoes scattered directly back from tissue to form an image, this system images tissue by displaying energy scattered at other angles. In its present form, the system uses one 32 element, 2.4 MHz phased array transducer in transmit and a second, spatially separate 32 element, 2.4 MHz phased array transducer in receive, to detect sound which is scattered away from the transmit transducer. In order to form an image line, the transmit transducer sends into the body a steered pulse, which is tracked dynamically from the side by the receive transducer. The signal detected by the receive transducer is processed in the same manner as in a standard B-mode phased array system. The final display format is a gray scale sector originating from the transmit transducer. Real-time angular scatter images of phantom and in vivo targets have been formed and compared to standard backscatter B-mode images of the same targets.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Piezoelectric materials for acoustic wave applications

    Page(s): 53 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Piezoelectric materials for acoustic wave applications have changed markedly over the past 20 years in terms of both the types of materials available and the quality of individual samples. The total family of acoustic wave materials now includes piezoelectric glass-ceramics having crystallographic and polar orientation and crystals having symmetry classes mm2, 32, 3m, 4mm, 6mm, and 4/spl macr/3m. The symmetry classes 6mm and 4/spl macr/3m also occur frequently in piezoelectric semiconductor materials that are now available in both bulk and thin-film configurations. In this paper, we bring together and extract the various reported values of the material constants mainly of interest for surface acoustic wave (SAW) device applications. We identify for the user community those sets of constants from which SAW design calculations can reliably be made, and discuss the constants and their reliability for langasite, lithium niobate/lithium tantalate, and dilithium tetraborate. The relevant material constants include: mass density /spl rho/, elastic stiffness c/sub ij/, piezoelectric stress e/sub ij/, dielectric permittivity /spl epsiv//sub ii/, and the thermal expansion coefficients /spl alpha//sub ii/. Except for the semiconductor materials, only data published after 1978 are included, since the reference literature (Landolt-Bornstein) amply covers those years prior to 1978.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Controlled-source analogous circuits and SPICE models for piezoelectric transducers

    Page(s): 60 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB)  

    Transmission line analogous circuits for piezoelectric transducers are developed which employ controlled sources rather than the traditional transformer to model the coupling between the electrical and the mechanical systems. A novel method is used to derive each model that consists of adding a term that is equal to zero to one of the device electromechanical equations. When this is done, it is shown that the equations can be cast into the form of the familiar telegraphist's equations for the voltage and current on an electrical transmission line. The circuits are derived for both the thickness-mode piezoelectric transducer and the side-electrode bar piezoelectric transducer. SPICE models of the analogous circuits are presented and an example simulation is given.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Physics of ultrasound contrast imaging: scattering in the linear range

    Page(s): 70 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1102 KB)  

    A simple model for B-mode image formation in diagnostic ultrasound is presented. It is used to give a general description of the effects, which scattering ultrasound contrast agents have on B- or M-mode images, as long as linear propagation of ultrasound is prevailing. The results of the model calculations are illustrated for the case of a homogeneous medium. It turns out that acoustical shadowing is limiting the maximum attainable backscatter enhancement. This becomes obvious when the model is also applied to the slightly more complicated case of cardiac and especially myocardial (or tissue) contrast. Conditions for optimum enhancement are derived for a number of typical diagnostic situations. Some possible pitfalls, which may prevent good results, are also called to attention. Microbubble suspensions are discussed as an important special example for contrast agents. In this case, the limits of the linear range can be estimated from the acoustically driven pulsations of a microbubble in a viscous fluid. The properties of contrast agents in the linear range described here should also provide a basis for later discussion of their nonlinear properties, which may help to overcome limitations imposed on tissue contrast in the linear range.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Exposimetry of unfocused pulsed ultrasound

    Page(s): 80 - 83
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (459 KB)  

    Therapeutic applications of unfocused pulsed ultrasound have recently been identified and require specialized exposimetry. Spatial distributions of pressure and several measures of intensity are presented for an unfocused pulsed ultrasound field produced by a PZT-4 transducer with diameter 3.8 cm and center frequency 2 MHz. Distributions of pressure I/sub tp/ and I/sub m/ were adequately uniform over a 4-cm/sup 2/ area in a transverse plane at an axial distance of 7 cm, but not so for I/sub ta/ and I/sub pa/, which both exhibited off-axis asymmetric maxima.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A review of experimental transverse Doppler studies

    Page(s): 84 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    The possibility of detecting useful Doppler information when the ultrasound beam is transversely oriented to the flow, has so far been studied by several authors. A new theory, in particular, has demonstrated that the focusing properties of piezoelectric transducers involve a Doppler signal bandwidth proportional to the transverse velocity component. The key element to perform reliable "transverse" Doppler experimental studies is thus an efficient spectrum analyzer, capable of performing accurate and repeatable bandwidth measurements. The authors review here experimental tests of the new theory, independently done in several laboratories by means of a specially developed computerized spectrum analyzer. The results of these tests include the demonstration that the "transverse" Doppler bandwidth is invariant with the range of cell depth and dimensions. It is also discussed how the basic transverse Doppler technique can be conveniently extended to allow the two- and three-dimensional estimation of the flow vector. Experimental evidence about the possibility of using the new theory to give a correct interpretation of in vivo transverse spectrograms is also presented.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional vector flow estimation using two transducers and spectral width

    Page(s): 90 - 95
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    Current ultrasonic blood flow measurement systems estimate only that component of flow which is parallel to the incident ultrasound beam. This is done by relating the mean backscattered frequency shift to the axial velocity component through the classical Doppler equation. A number of ultrasonic techniques for estimating the two-dimensional (2D) blood velocity vector have been published, both Doppler and non-Doppler. Several three-dimensional (3D) blood velocity vector techniques have also been proposed, all of which require a multiplicity of transducers or lines of sight. Here a technique is described for estimating the total velocity vector, using only two transducers. This is achieved by measuring not only the frequency shifts but also the bandwidths of the backscattered spectra, making use of the fact that the bandwidth of a Doppler spectrum has been shown to be proportional to the velocity component normal to the sound beam. Partial experimental verification of the proposed vector flow estimation scheme is demonstrated by using a constant velocity thread phantom.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasound methods for investigating the non-Newtonian characteristics of whole blood

    Page(s): 96 - 104
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    The development and evaluation of new techniques for investigating the non-Newtonian characteristics of blood are described. Ultrasound B-mode imaging (7 MHz) was used to measure simultaneously the echogenicity and velocity profiles of 28% hematocrit porcine whole blood. Measurements were made at various locations in a large diameter (D=2.54 cm) long (>60 D) tube, under steady flow conditions. A block matching (correlation) technique between successive digitized images was used to determine the velocity profiles, and from these, shear rate profiles were calculated. The optimal block dimensions were found to be dependent on the magnitude and direction of the flow shear rate. Echogenicity profiles were determined from ensemble averaged images. It is shown how such profiles in combination with the corresponding shear rate profiles enables information to be obtained concerning the dependence of aggregation on shear rate. Pulsed Doppler ultrasound (20 MHz) was also used to measure the velocity and backscattered power profiles at 60 D from the tube entrance. Velocity profiles measured using B-mode were in good agreement with those obtained using both pulsed Doppler and magnetic resonance imaging and mean velocity errors of less that 5% were achieved.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Speckle motion artifact under tissue rotation

    Page(s): 105 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1980 KB)  

    Speckle patterns in ultrasound images may move in a way which bears no simple relationship to the motion of the corresponding tissues. In some instances the speckle motion replicates the underlying tissue motion, in others it does not. The authors name "speckle motion artifact" the difference between the speckle and the underlying tissue motion. An echographic image formation model is used to study the motion artifact produced by a rotating phantom and observed by a linear scan imaging system with a Gaussian beam. The authors propose that when the tissue is modeled as a random array of small and numerous scatterers, such motion aberration be accounted for by the 2D phase characteristics of the imaging system. An analytic prediction of this motion artifact in relation to the imaging system characteristics (beam width, transducer frequency, pulse duration) is presented. It is shown that the artifact results from the curvature of the system point spread function, which in turn determines the curvature of the 2D phase characteristics. To the authors' knowledge, it is the first time a comprehensive model of ultrasonic speckle motion artifact is presented. The model has been developed to study rotation-induced artifact; the method is however quite general and can be extended to study the effects of other tissue motion, in particular deformation and shear.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reciprocity calibration of ultrasonic contact transducers

    Page(s): 123 - 129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (643 KB)  

    The extension of the reciprocity calibration method widely used in medical ultrasonics to nondestructive pulse-echo transducers is presented. It is shown that the self-reciprocity procedure originally developed for immersion transducers can also be applied to contact transducers, which are mainly used for the investigation of solids. The sensitivity of the contact transducers used was calculated with the help of two models which simulate the behavior of the transmitter-receiver arrangement within the whole frequency range investigated, namely 2-12 MHz. The procedure needed to determine the diffraction losses associated with the test objects such as half cylinders and half spheres is also presented. Half cylinders or half spheres are needed when the ultrasonic wave does not have a normal incidence on the test object. The calculated diffraction loss for the half cylinder was also experimentally verified. Good agreement obtained between diffraction loss measurements and the model predictions confirms that the calculated diffraction loss of the half cylinder is suitable for use in practical investigations. The calibration procedure described enables ultrasonic measurements performed with different contact transducers and devices to be compared. This is of great importance in many applications, as for example in periodic routine inspections of the components of nuclear facilities.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Shock wave pulse pressure after penetration of kidney tissue

    Page(s): 130 - 133
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Lithotripter generated compressional peak pressure (p/sup +/) was measured after penetrating tissue samples 0.5, 1, 2.5, and 4 cm thick. The samples were taken from fresh pig kidneys and insonated by shock wave pulses with positive peak pressures varying from 14 to 72 MPa. The measurement results allow one to draw some qualitative conclusions concerning the attenuation process in the lithotripter beam and show that in practice the compressional peak pressure values generated in the lithotripter may decrease almost by a factor of two before reaching the kidney stone. On the contrary, theoretical estimates indicate that negative pressures are practically not influenced by attenuation due to their different spectral composition.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Impingement angle and scan direction influence on B-scan imaging in tissue classification

    Page(s): 134 - 139
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    The potential critical influence of impingement angle and scan direction on B-scan imaging for tissue classification is explored in this work. The effects of variations of other system parameters on B-scan images are also investigated. Particular attention is paid to the influence of the direction of propagation of the interrogating wave within the tissue structure. This is done in order to explore the hypothesis that the detection of malignant areas embedded inside a host ordered tissue can be improved by exploiting the disordered structure of the diseased region. Results of preliminary experiments performed on a phantom give an indication that speckle pattern variations due to impingement angle and/or scan direction can occur that relates to the structural properties of the tissue from a scattering point of view. Sample problems are presented to differentiate the structural variations within a tissue by analyzing a phantom constructed of unidirectional fibers arranged in layers that are staggered with respect to each other.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A survey of developments in ultrasonic NDE of concrete

    Page(s): 140 - 143
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (469 KB)  

    The goal of this paper is to develop an understanding of the current state of ultrasonic nondestructive evaluation in the concrete community. Methods supplemental to the less than satisfactory procedure specified in ASTM C-597 are discussed. It is hoped that such an understanding, in conjunction with a feeling for the nature of reinforced concrete as a material, will promote research interest in this important field. Following an introductory problem statement, a literature review concerning the existing use of stress waves for the nondestructive evaluation of concrete is presented. An examination of current practice is offered. Next, new approaches are selected and reviewed from the current literature. In all cases, these are approaches that have been successful in applications to advanced engineering materials other than concrete. Where appropriate, potential benefits and pitfalls of each new technique, as applied to concrete, are discussed.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic attenuation based on the Roney generalized theory and multiple power-law grain-size distributions

    Page(s): 144 - 149
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (458 KB)  

    We investigate ultrasonic attenuation as a nondestructive determination of grain-size distributions. Previous work showed power-law relationships between the wavelength dependence of ultrasonic attenuation and a single power-law grain-size distribution, along with experimental verification. The work presented here further validates the previously reported relationship for single power-law grain-size distributions, and generalizes the relationships to cases where the grain-size distribution follows multiple power-laws. Roney's generalized approach to ultrasonic attenuation is used. Numerical results are presented for the single power-law and multiple power-law cases. The attenuation exponents computed from the numerical calculations correspond well with theoretical expectations. For wavelengths greater than all the grain sizes, Rayleigh scattering dominates and the attenuation exponent approaches 4. For single power-laws and wavelengths between the smallest and largest grain size, the attenuation exponent equals the grain-size distribution exponent. When multiple power-laws are used to describe the grain-size distribution, the attenuation exponent is a combination of the grain-size distribution exponent, and therefore cannot be directly measured from the attenuation curve.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrasonic flaw detection based on mathematical morphology

    Page(s): 150 - 160
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    The deterministic and statistical properties of morphological filters and their application in ultrasonic flaw detection have studied utilizing different structuring elements. It has been shown the effectiveness of the filtering process depends on the frequency content of input signals, the combination of morphological operations, and the parameters of the structuring elements. The statistical parameters (mean, variance, and skewness) of sequential morphological operations (i.e., dilation, closing, clos-erosion, and clos-opening) are examined in order to determine the noise suppression capability of morphological filters and their biasing effects. Experimental evaluation of morphological filters for flaw detection in the presence of strong scattering echoes is presented for A- and B-scans. The processed experimental results show that morphological filters can improve flaw visibility by suppressing microstructure scattering echoes. The performance of morphological filters is compared with that of recursive median filters and ensemble averaging using experimental data. Results indicate that morphological filters perform better than recursive median filters in preserving the geometric structure of the signal and can replace ensemble averaging which requires numerous measurements.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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

Full Aims & Scope

Meet Our Editors

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