Science.gov

Sample records for acoustic wavefield imaging

  1. Passive imaging in nondiffuse acoustic wavefields.

    PubMed

    Mulargia, Francesco; Castellaro, Silvia

    2008-05-30

    A main property of diffuse acoustic wavefields is that, taken any two points, each of them can be seen as the source of waves and the other as the recording station. This property is shown to follow simply from array azimuthal selectivity and Huygens principle in a locally isotropic wavefield. Without time reversal, this property holds approximately also in anisotropic azimuthally uniform wavefields, implying much looser constraints for undistorted passive imaging than those required by a diffuse field. A notable example is the seismic noise field, which is generally nondiffuse, but is found to be compatible with a finite aperture anisotropic uniform wavefield. The theoretical predictions were confirmed by an experiment on seismic noise in the mainland of Venice, Italy. PMID:18518643

  2. Passive Imaging in Nondiffuse Acoustic Wavefields

    SciTech Connect

    Mulargia, Francesco; Castellaro, Silvia

    2008-05-30

    A main property of diffuse acoustic wavefields is that, taken any two points, each of them can be seen as the source of waves and the other as the recording station. This property is shown to follow simply from array azimuthal selectivity and Huygens principle in a locally isotropic wavefield. Without time reversal, this property holds approximately also in anisotropic azimuthally uniform wavefields, implying much looser constraints for undistorted passive imaging than those required by a diffuse field. A notable example is the seismic noise field, which is generally nondiffuse, but is found to be compatible with a finite aperture anisotropic uniform wavefield. The theoretical predictions were confirmed by an experiment on seismic noise in the mainland of Venice, Italy.

  3. Damage Detection in Plate Structures Using Sparse Ultrasonic Transducer Arrays and Acoustic Wavefield Imaging

    SciTech Connect

    Michaels, T.E.; Michaels, J.E.; Mi, B.; Ruzzene, M.

    2005-04-09

    A methodology is presented for health monitoring and subsequent inspection of critical structures. Algorithms have been developed to detect and approximately locate damaged regions by analyzing signals recorded from a permanently mounted, sparse array of transducers. Followup inspections of suspected flaw locations are performed using a dual transducer ultrasonic approach where a permanently mounted transducer is the source and an externally scanned transducer is the receiver. Scan results are presented as snapshots of the propagating ultrasonic wavefield radiating out from the attached transducers. This method, referred to here as Acoustic Wavefield Imaging (AWI), provides an excellent visual representation of the interaction of propagating ultrasonic waves with the structure. Pre-flaw and post-flaw ultrasonic waveforms are analyzed from an aluminum plate specimen with artificially induced damage, and the AWI results show the location and spatial extent of all of the defects.

  4. Wavefield imaging using the energy norm

    NASA Astrophysics Data System (ADS)

    Rocha, Daniel Carvalho, Junior

    For various wavefield types, one can formulate a measurement of the mechanical energy that satisfies conservation laws. Based on this formulation, one can derive an energy norm that is applicable to wavefield imaging. Extending the concept of the norm to an inner product, one can compare two related wavefields. Therefore, an imaging condition can be defined as the inner product between the source and receiver wavefields at every spatial location. In this regard, the imaging condition based on the energy inner product accounts for wavefield directionality in space and time, overcoming some problems present in the conventional imaging condition. I exploit the wavefield directionality information from the energy imaging condition to attenuate unwanted events in reverse time migrated (RTM) images. For acoustic wavefields, these unwanted events are characterized by the collinearity of the source and receiver raypaths, and they are described as RTM backscattering artifacts. For elastic wavefields, these events are characterized by the fact that source and receiver displacement fields have the same polarization and wave propagation directions. In both acoustic and elastic cases, one can to attenuate these artifacts and produce high quality images. Another application that uses the wavefield directionality is to enhance the full waveform inversion (FWI) gradient for acoustic wavefields. By enhancing wave events that are collinear and suppressing all other wave events, I am able to compute gradients that are more suitable for the inversion process. Numerical experiments show the efficacy of these applications for synthetic models that emulate the complexity of subsurface structures found in exploration seismology, such as salt bodies, diffractors, dipping layers and faults.

  5. Numerical Modeling of Ocean Acoustic Wavefields

    NASA Astrophysics Data System (ADS)

    Tappert, Frederick

    1997-08-01

    The U.S. Navy requires real-time ``acoustic performance prediction'' models in order to optimize sonar tactics in naval combat situations. The need for numerical models that solve the acoustic wave equation in realistic ocean environments is being met by a collaborative effort between university researchers, industrial contractors, and navy laboratory workers. This paper discusses one particularly successful numerical model, called the PE/SSF model, that was originally developed by the author. Here PE stands for Parabolic Equation, a good approximation to the elliptic Helmholtz equation; and SSF stands for the Split-Step Fourier algorithm, a highly efficient marching algorithm for solving parabolic type equations. These techniques are analyzed, and examples are displayed of ocean acoustic wavefields generated by the PE/SSF model.

  6. Wavefield tomography using extended images

    NASA Astrophysics Data System (ADS)

    Yang, Tongning

    Estimating an accurate velocity model is crucial for seismic imaging to obtain a good understanding of the subsurface structure. The objective of this thesis is to investigate methods of velocity analysis by optimizing seismic images. A conventional seismic image is obtained by zero-lag crosscorrelation of wavefields extrapolated from a source wavelet and recorded data on the surface using a velocity model. The velocity model provides the kinematic information needed by the imaging algorithm to position the reflectors at correct locations and to focus the image. In complex geology, wave-equation migration is a powerful tool for accurately imaging the earth's interior; the quality of the output image, however, depends on the accuracy of the velocity model. Given such a dependency between the image and model, analyzing the velocity information from the image is still not intuitive and often ambiguous. If the nonzero space- and time-lags information are preserved in the crosscorrelation, the output are image hypercube defined as extended images. Compared to the conventional image, the extended images provide a straightforward way to analyze the image quality and to characterize the velocity model accuracy. Understanding the reflection moveout is the key to developing velocity model building methods using extended images. In the extended image space, reflections form coherent objects which depend on space (lags) and time (lags). These objects resemble cones which ideally have their apex at zero space and time lags. The symmetry axis of the cone lies along the time-lag axis. The apex of the cone is located at zero lags only if the velocity model is accurate. This corresponds to the situation when reflection energy focuses at origin in both the space- and time-lag common-image gathers (the slices at zero time and space lags, respectively). When the velocity model is inaccurate, the cone shifts along the time-lag axis. This results in residual moveout in space-lag gathers

  7. INVERSION OF FULL ACOUSTIC WAVEFIELD IN LOCAL HELIOSEISMOLOGY: A STUDY WITH SYNTHETIC DATA

    SciTech Connect

    Cobden, L. J.; Warner, M. R.; Tong, C. H.

    2011-02-01

    We present the first results from the inversion of full acoustic wavefield in the helioseismic context. In contrast to time-distance helioseismology, which involves analyzing the travel times of seismic waves propagating into the solar interior, wavefield tomography models both the travel times and amplitude variations present in the entire seismic record. Unlike the use of ray-based, Fresnel-zone, Born, or Rytov approximations in previous time-distance studies, this method does not require any simplifications to be made to the sensitivity kernel in the inversion. In this study, the acoustic wavefield is simulated for all iterations in the inversion. The sensitivity kernel is therefore updated while lateral variations in sound-speed structure in the model emerge during the course of the inversion. Our results demonstrate that the amplitude-based inversion approach is capable of resolving sound-speed structures defined by relatively sharp vertical and horizontal boundaries. This study therefore provides the foundation for a new type of subsurface imaging in local helioseismology that is based on the inversion of the entire seismic wavefield.

  8. Adaptive finite difference for seismic wavefield modelling in acoustic media.

    PubMed

    Yao, Gang; Wu, Di; Debens, Henry Alexander

    2016-01-01

    Efficient numerical seismic wavefield modelling is a key component of modern seismic imaging techniques, such as reverse-time migration and full-waveform inversion. Finite difference methods are perhaps the most widely used numerical approach for forward modelling, and here we introduce a novel scheme for implementing finite difference by introducing a time-to-space wavelet mapping. Finite difference coefficients are then computed by minimising the difference between the spatial derivatives of the mapped wavelet and the finite difference operator over all propagation angles. Since the coefficients vary adaptively with different velocities and source wavelet bandwidths, the method is capable to maximise the accuracy of the finite difference operator. Numerical examples demonstrate that this method is superior to standard finite difference methods, while comparable to Zhang's optimised finite difference scheme. PMID:27491333

  9. Adaptive finite difference for seismic wavefield modelling in acoustic media

    NASA Astrophysics Data System (ADS)

    Yao, Gang; Wu, Di; Debens, Henry Alexander

    2016-08-01

    Efficient numerical seismic wavefield modelling is a key component of modern seismic imaging techniques, such as reverse-time migration and full-waveform inversion. Finite difference methods are perhaps the most widely used numerical approach for forward modelling, and here we introduce a novel scheme for implementing finite difference by introducing a time-to-space wavelet mapping. Finite difference coefficients are then computed by minimising the difference between the spatial derivatives of the mapped wavelet and the finite difference operator over all propagation angles. Since the coefficients vary adaptively with different velocities and source wavelet bandwidths, the method is capable to maximise the accuracy of the finite difference operator. Numerical examples demonstrate that this method is superior to standard finite difference methods, while comparable to Zhang’s optimised finite difference scheme.

  10. Adaptive finite difference for seismic wavefield modelling in acoustic media

    PubMed Central

    Yao, Gang; Wu, Di; Debens, Henry Alexander

    2016-01-01

    Efficient numerical seismic wavefield modelling is a key component of modern seismic imaging techniques, such as reverse-time migration and full-waveform inversion. Finite difference methods are perhaps the most widely used numerical approach for forward modelling, and here we introduce a novel scheme for implementing finite difference by introducing a time-to-space wavelet mapping. Finite difference coefficients are then computed by minimising the difference between the spatial derivatives of the mapped wavelet and the finite difference operator over all propagation angles. Since the coefficients vary adaptively with different velocities and source wavelet bandwidths, the method is capable to maximise the accuracy of the finite difference operator. Numerical examples demonstrate that this method is superior to standard finite difference methods, while comparable to Zhang’s optimised finite difference scheme. PMID:27491333

  11. ELASTIC-WAVEFIELD SEISMIC STRATIGRAPHY: A NEW SEISMIC IMAGING TECHNOLOGY

    SciTech Connect

    Bob A. Hardage

    2004-05-06

    The focus of elastic-wavefield seismic stratigraphy research shifted from onshore prospects to marine environments during this report period. Four-component ocean-bottom-cable (4-C OBC) seismic data acquired in water depths of 2400 to 2500 feet across Green Canyon Block 237 in the Gulf of Mexico were processed and analyzed. The P-P and P-SV images of strata immediately below the seafloor exhibit amazing differences in P-P and P-SV seismic facies. These data may be one of the classic examples of the basic concepts of elastic-wavefield seismic stratigraphy.

  12. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    SciTech Connect

    Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava

    2006-07-31

    The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.

  13. Imaging the North Anatolian Fault using the scattered teleseismic wavefield

    NASA Astrophysics Data System (ADS)

    Thompson, D. A.; Rost, S.; Houseman, G. A.; Cornwell, D. G.; Turkelli, N.; Teoman, U.; Kahraman, M.; Altuncu Poyraz, S.; Gülen, L.; Utkucu, M.; Frederiksen, A. W.; Rondenay, S.

    2013-12-01

    The North Anatolian Fault Zone (NAFZ) is a major continental strike-slip fault system, similar in size and scale to the San Andreas system, that extends ˜1200 km across Turkey. In 2012, a new multidisciplinary project (FaultLab) was instigated to better understand deformation throughout the entire crust in the NAFZ, in particular the expected transition from narrow zones of brittle deformation in the upper crust to possibly broader shear zones in the lower crust/upper mantle and how these features contribute to the earthquake loading cycle. This contribution will discuss the first results from the seismic component of the project, a 73 station network encompassing the northern and southern branches of the NAFZ in the Sakarya region. The Dense Array for North Anatolia (DANA) is arranged as a 6×11 grid with a nominal station spacing of 7 km, with a further 7 stations located outside of the main grid. With the excellent resolution afforded by the DANA network, we will present images of crustal structure using the technique of teleseismic scattering tomography. The method uses a full waveform inversion of the teleseismic scattered wavefield coupled with array processing techniques to infer the properties and location of small-scale heterogeneities (with scales on the order of the seismic wavelength) within the crust. We will also present preliminary results of teleseismic scattering migration, another powerful method that benefits from the dense data coverage of the deployed seismic network. Images obtained using these methods together with other conventional imaging techniques will provide evidence for how the deformation is distributed within the fault zone at depth, providing constraints that can be used in conjunction with structural analyses of exhumed fault segments and models of geodetic strain-rate across the fault system. By linking together results from the complementary techniques being employed in the FaultLab project, we aim to produce a comprehensive

  14. The Utility of the Extended Images in Ambient Seismic Wavefield Migration

    NASA Astrophysics Data System (ADS)

    Girard, A. J.; Shragge, J. C.

    2015-12-01

    Active-source 3D seismic migration and migration velocity analysis (MVA) are robust and highly used methods for imaging Earth structure. One class of migration methods uses extended images constructed by incorporating spatial and/or temporal wavefield correlation lags to the imaging conditions. These extended images allow users to directly assess whether images focus better with different parameters, which leads to MVA techniques that are based on the tenets of adjoint-state theory. Under certain conditions (e.g., geographical, cultural or financial), however, active-source methods can prove impractical. Utilizing ambient seismic energy that naturally propagates through the Earth is an alternate method currently used in the scientific community. Thus, an open question is whether extended images are similarly useful for ambient seismic migration processing and verifying subsurface velocity models, and whether one can similarly apply adjoint-state methods to perform ambient migration velocity analysis (AMVA). Herein, we conduct a number of numerical experiments that construct extended images from ambient seismic recordings. We demonstrate that, similar to active-source methods, there is a sensitivity to velocity in ambient seismic recordings in the migrated extended image domain. In synthetic ambient imaging tests with varying degrees of error introduced to the velocity model, the extended images are sensitive to velocity model errors. To determine the extent of this sensitivity, we utilize acoustic wave-equation propagation and cross-correlation-based migration methods to image weak body-wave signals present in the recordings. Importantly, we have also observed scenarios where non-zero correlation lags show signal while zero-lags show none. This may be a valuable missing piece for ambient migration techniques that have yielded largely inconclusive results, and might be an important piece of information for performing AMVA from ambient seismic recordings.

  15. Simultaneous source wavefield separation by signal apparition

    NASA Astrophysics Data System (ADS)

    Robertsson, Johan O. A.; Amundsen, Lasse; Pedersen, Åsmund Sjøen

    2016-06-01

    A new method for discrete sampling of signals is presented with specific applications to the reconstruction of recorded interfering wavefields from two or more sources excited simultaneously at discrete positions along lines. By utilizing a periodic sequence of source signatures along one of the source lines, the corresponding wavefield becomes separately visible in a part of the spectral domain where it can be isolated, processed, and subtracted from the interfering wavefields. As a result, interfering wavefields from multiple sources recorded at a single location can be fully separated from each other. The concept is referred to as signal apparition which we suggest refers to "the act of becoming visible". It may find applications in a wide range of disciplines relying on wave experimentation such as acoustic, seismic, and electromagnetic imaging of the Earth's interior for instance to significantly enhance resolution of sub-surface images.

  16. Signal apparition for simultaneous source wavefield separation

    NASA Astrophysics Data System (ADS)

    Robertsson, Johan O. A.; Amundsen, Lasse; Pedersen, Åsmund Sjøen

    2016-08-01

    A new method for discrete sampling of signals is presented with specific applications to the reconstruction of recorded interfering wavefields from two or more sources excited simultaneously at discrete positions along lines. By utilizing a periodic sequence of source signatures along one of the source lines, the corresponding wavefield becomes separately visible in a part of the spectral domain where it can be isolated, processed and subtracted from the interfering wavefields. As a result, interfering wavefields from multiple sources recorded at a single location can be fully separated from each other. The concept is referred to as signal apparition which we suggest refers to `the act of becoming visible'. It may find applications in a wide range of disciplines relying on wave experimentation, such as acoustic, seismic and electromagnetic imaging of the Earth's interior for instance to significantly enhance resolution of subsurface images.

  17. The seismic noise wavefield is not diffuse.

    PubMed

    Mulargia, Francesco

    2012-04-01

    Passive seismology is burgeoning under the apparent theoretical support of diffuse acoustics. However, basic physical arguments suggest that this theory may not be applicable to seismic noise. A procedure is developed to establish the applicability of the diffuse field paradigm to a wavefield, based on testing the latter for azimuthal isotropy and spatial homogeneity. This procedure is then applied to the seismic noise recorded at 65 sites covering a wide variety of environmental and subsoil conditions. Considering the instantaneous oscillation vector measured at single triaxial stations, the hypothesis of azimuthal isotropy is rejected in all cases with high confidence, which makes the spatial homogeneity test unnecessary and leads directly to conclude that the seismic noise wavefield is not diffuse. However, such a conclusion has no practical effect on passive imaging, which is also possible in non-diffuse wavefields. PMID:22501063

  18. Wireless ultrasonic wavefield imaging via laser for hidden damage detection inside a steel box girder bridge

    NASA Astrophysics Data System (ADS)

    An, Yun-Kyu; Song, Homin; Sohn, Hoon

    2014-09-01

    This paper presents a wireless ultrasonic wavefield imaging (WUWI) technique for detecting hidden damage inside a steel box girder bridge. The proposed technique allows (1) complete wireless excitation of piezoelectric transducers and noncontact sensing of the corresponding responses using laser beams, (2) autonomous damage visualization without comparing against baseline data previously accumulated from the pristine condition of a target structure and (3) robust damage diagnosis even for real structures with complex structural geometries. First, a new WUWI hardware system was developed by integrating optoelectronic-based signal transmitting and receiving devices and a scanning laser Doppler vibrometer. Next, a damage visualization algorithm, self-referencing f-k filter (SRF), was introduced to isolate and visualize only crack-induced ultrasonic modes from measured ultrasonic wavefield images. Finally, the performance of the proposed technique was validated through hidden crack visualization at a decommissioned Ramp-G Bridge in South Korea. The experimental results reveal that the proposed technique instantaneously detects and successfully visualizes hidden cracks even in the complex structure of a real bridge.

  19. 3D Elastic Wavefield Tomography

    NASA Astrophysics Data System (ADS)

    Guasch, L.; Warner, M.; Stekl, I.; Umpleby, A.; Shah, N.

    2010-12-01

    or less than 300x300x300 nodes, and it under-samples the wavefield reducing the number of stored time-steps by an order of magnitude. For bigger models the wavefield is stored only at the boundaries of the model and then re-injected while the residuals are backpropagated allowing to compute the correlation 'on the fly'. In terms of computational resource, the elastic code is an order of magnitude more demanding than the equivalent acoustic code. We have combined shared memory with distributed memory parallelisation using OpenMP and MPI respectively. Thus, we take advantage of the increasingly common multi-core architecture processors. We have successfully applied our inversion algorithm to different realistic complex 3D models. The models had non-linear relations between pressure and shear wave velocities. The shorter wavelengths of the shear waves improve the resolution of the images obtained with respect to a purely acoustic approach.

  20. Development of Active Seismic Vector-Wavefield Imaging Technology for Geothermal Applications

    SciTech Connect

    B. A. Hardage; J. L. Simmons, Jr.; M. DeAngelo

    1999-10-01

    This report describes the development and testing of vector-wavefield seismic sources that can generate shear (S) waves that may be valuable in geothermal exploration and reservoir characterization. Also described is a 3-D seismic data-processing effort to create images of Rye Patch geothermal reservoir from 3-D sign-bit data recorded over the geothermal prospect. Two seismic sources were developed and tested in this study that can be used to illuminate geothermal reservoirs with S-waves. The first was an explosive package that generates a strong, azimuth-oriented, horizontal force vector when deployed in a conventional shot hole. This vector-explosive source has never been available to industry before. The second source was a dipole formed by operating two vertical vibrators in either a force or phase imbalance. Field data are shown that document the strong S-wave modes generated by these sources.

  1. Appraising the reliability of converted wavefield imaging: application to USArray imaging of the 410-km discontinuity

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Pavlis, Gary L.

    2013-03-01

    We develop a generic method to appraise the reliability of wavefield imaging methods and use it to validate some novel observations on the 410-km discontinuity. The core concept of the error appraisal method is to produce a simulated data set that replicates the geometry of the real data. Here we implemented two simulation methods: (1) flat layer primary P to S conversions, and (2) a point source scattering model for P to S conversion data based on the Born approximation and ray theory propagators. We show how the approach can be extended for any simulation algorithm. We apply this new approach to appraise recent results using a 3-D, three-component P to S conversion imaging method applied to data collected by the USArray. Multiple metrics show that the amplitude of P to S converted energy scattered from the 410-km discontinuity varies by 18 dB with a systematically lower amplitude in an irregular band running from Idaho through northern Arizona. In addition, we observe strong lateral changes in the ratio of amplitudes recovered on the radial versus the transverse component. We compute point resolution functions and a checkerboard test to demonstrate we can reliably recover relative amplitudes with a lateral scale of the order of 200 km and a vertical scale of approximately 10 km. Irregular coverage locally distorts the amplitudes recovered in the checkerboard, but a 156 km scale checkerboard pattern is recovered. Flat layer simulations show we can recover relative amplitudes to within a range of 1 dB and the reconstructed transverse to radial amplitude is everywhere less than 0.1. A model with north-south oriented ridges with a 3° wavelength and 12.5 km amplitude shows of the order of ±6 dB amplitude variations and small, but clear correlation of the transverse/radial amplitude ratio topography in the model. Finally, we model the 410-km discontinuity as a rough surface characterized by variations in amplitude and depth derived from the USArray data. The rough

  2. Characterization of propagation and scattering via wavefield imaging for improved in situ imaging of damage in composites

    NASA Astrophysics Data System (ADS)

    Williams, Westin B.; Michaels, Jennifer E.; Michaels, Thomas E.

    2016-04-01

    Detection, localization, and characterization of impact damage in composites using in situ transducers are important objectives for the aerospace industry to both reduce maintenance costs and prevent failures. A network of piezoelectric transducers spatially distributed over an area of interest is one practical configuration for utilizing guided waves to accomplish these objectives. Detecting and localizing barely visible impact damage with such a sparse array has been demonstrated in prior work, and improvements in localization were demonstrated by incorporating fairly crude estimates of scattering patterns in the imaging algorithms. Here we obtain more estimates of scattering patterns from a simulated defect by employing baseline subtraction of wavefield data recorded in a circle centered at the scatterer. Scattering patterns are estimated from the wavefield residual signals before and after simulated damage is introduced and the estimated scattering patterns are then incorporated into sparse array imaging via the minimum variance imaging method. Images created with different scattering patterns are compared and the efficacy of the methodology is assessed.

  3. A General-applications Direct Global Matrix Algorithm for Rapid Seismo-acoustic Wavefield Computations

    NASA Technical Reports Server (NTRS)

    Schmidt, H.; Tango, G. J.; Werby, M. F.

    1985-01-01

    A new matrix method for rapid wave propagation modeling in generalized stratified media, which has recently been applied to numerical simulations in diverse areas of underwater acoustics, solid earth seismology, and nondestructive ultrasonic scattering is explained and illustrated. A portion of recent efforts jointly undertaken at NATOSACLANT and NORDA Numerical Modeling groups in developing, implementing, and testing a new fast general-applications wave propagation algorithm, SAFARI, formulated at SACLANT is summarized. The present general-applications SAFARI program uses a Direct Global Matrix Approach to multilayer Green's function calculation. A rapid and unconditionally stable solution is readily obtained via simple Gaussian ellimination on the resulting sparsely banded block system, precisely analogous to that arising in the Finite Element Method. The resulting gains in accuracy and computational speed allow consideration of much larger multilayered air/ocean/Earth/engineering material media models, for many more source-receiver configurations than previously possible. The validity and versatility of the SAFARI-DGM method is demonstrated by reviewing three practical examples of engineering interest, drawn from ocean acoustics, engineering seismology and ultrasonic scattering.

  4. Airborne infrasound: A new way to explore the 3D acoustic wavefield

    NASA Astrophysics Data System (ADS)

    Jones, K. R.

    2015-12-01

    As a part of the Source Physics Experiment (SPE) site characterization and explosive test series, we developed and deployed an airborne octocopter infrasound platform. Traditionally, infrasound data is collected with sensors and arrays that are installed on the ground. For most applications this is sufficient but can be limiting when observing non-isotropic sources, such as underground explosions, at close range. To develop and test the airborne infrasound platform we recorded data from a seismo-acoustic hammer source at the Nevada National Security Site (NNSS). During early field-testing of the hammer source we found that, as the 13 metric ton mass hit the ground, a significant downward deflection of the surrounding surface imparted an observable infrasound pressure wave into the atmosphere. We compared waveforms collected at various vertical and horizontal offsets from the hammer source and found that the peak frequencies differed when observed directly above the source compared to the horizontal offsets. This work was done under award number DE-AC52-06NA25946. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Acoustic imaging system

    DOEpatents

    Smith, Richard W.

    1979-01-01

    An acoustic imaging system for displaying an object viewed by a moving array of transducers as the array is pivoted about a fixed point within a given plane. A plurality of transducers are fixedly positioned and equally spaced within a laterally extending array and operatively directed to transmit and receive acoustic signals along substantially parallel transmission paths. The transducers are sequentially activated along the array to transmit and receive acoustic signals according to a preestablished sequence. Means are provided for generating output voltages for each reception of an acoustic signal, corresponding to the coordinate position of the object viewed as the array is pivoted. Receptions from each of the transducers are presented on the same display at coordinates corresponding to the actual position of the object viewed to form a plane view of the object scanned.

  6. Modeling and Processing of Continuous 3D Elastic Wavefield Data

    NASA Astrophysics Data System (ADS)

    Milkereit, B.; Bohlen, T.

    2001-12-01

    Continuous seismic wavefields are excited by earthquake clustering, induced seismicity in reservoirs, and mining. In hydrocarbon reservoirs, for example, pore pressure changes and fluid flow (mass transfer) will cause incremental deviatoric stresses sufficient to trigger and sustain seismic activity. Here we address three aspects of seismic wavefields in three-dimensional heterogeneous media triggered by distributed sources in space and time: forward modeling, multichannel data processing, and source location imaging. A power law distribution of seismic sources (such as the Gutenberg-Richter law) is used for the modeling of viscoelastic/elastic wave propagation through a realistic earth model. 3D modeling provides new insight in the interaction of multi-source wavefields and the role of scale-dependend elastic model parameters on transmitted and reflected/back-scattered wavefields. There exists a strong correlation between the spatial properties of the compressional, shear wave and density perturbations and the lateral correlation length of the resulting reflected or transmitted seismic wavefields. Modeling is based on the implementation of 3D elastic/viscoelastic FD codes on massive parallel and/or distributed computing resources using MPI (message passing interface). For parallelization, large grid 3D earth models are decomposed into subvolume processing elements whereby each processing element is updating the wavefield within its portion of the grid. Processing of continuous seismic wavefields excited by multiple distributed sources is based on a combination of crosscorrelated or slowness-transformed array data and Kirchhoff or reverse time migration for source location or source volume imaging. The appearance of slowness in both migration and array data processing suggests the possibility of combining them into a single process. In order to place further constraints on the migration, the directivity properties of 3-component receiver arrays can be included in

  7. Characterizing the ambient seismic wavefield for upper crustal imaging: energy sources and station deployment protocols in an ocean island setting

    NASA Astrophysics Data System (ADS)

    Reading, A. M.; Heckscher, N.; Graham, L.; Arroucau, P.; Rawlinson, N.

    2009-12-01

    Techniques using ambient seismic energy have become powerful tools in the imaging of the Earth's lithosphere. In this work we investigate the potential for using ambient energy to image the upper crust at the highest possible resolution. Such images are sought-after in deducing regional-scale 3D geological structure. They are critical to activities which use the Earth's crust (e.g. hot dry rock geothermal energy production, carbon sequestration) as well as placing fundamental constraints on the crustal architecture which defines tectonic structure and evolution. We have deployed a line of variously spaced seismic stations in a region of relatively well-constrained regional geology in Eastern Tasmania. Located south of mainland Australia, in the 'roaring 40's' southerly latitudes, the ambient seismic energy is of considerable amplitude. We are able to characterise the ambient seismic wavefield: investigating the influence of station deployment geometry, deployment and processing protocols, and ocean and atmospheric conditions on the amplitude and frequency content of the signals derived from correlated waveforms. We also investigate the potential of using diffuse seismic sources from a highway and railway using ambient energy techniques. We find that, in this ocean-dominated island setting, a correlated signal of sufficient strength to model for structure is obtained in a few days. The relationship between station separation and the dominant wavelengths in the correlated signals places a minimum limit on station separations which are usable with standard modelling techniques. Hence, in this environment, crustal imaging may be best carried out using deployments with overlapping, frequently moved (or numerous and short-deployed), sets of station pairs. The potential for using cultural noise sources is limited by the dominance of the natural noise sources in the ambient wavefield.

  8. Volumetric Imaging Using Acoustical Holography

    NASA Astrophysics Data System (ADS)

    Garlick, T. F.; Garlick, G. F.

    Transmission acoustical holography holds tremendous promise for medical imaging applications. As with optical holography, an image is obtained using the interference of two coherent acoustic sources, the transmitted object wave with a reference wave. Although resultant images are true holograms, depth can be difficult to quantify and an entire volume in one image can often result in "too much" information. Since Physicians/Radiologists are often interested in viewing a single plane at a time, techniques have been developed to generate acoustic holograms of "slices" within a volume. These primarily include focused transmission holography with spatial and frequency filtering techniques. These techniques along with an overview and current status of acoustical holography in medical imaging applications will be presented

  9. Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens

    SciTech Connect

    Cheng, Ying; Liu, XiaoJun; Zhou, Chen; Wei, Qi; Wu, DaJian

    2013-11-25

    Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

  10. Seismic imaging of crust and upper mantle structure in western North America via surface wave inversion and wavefield depropagation

    NASA Astrophysics Data System (ADS)

    Stachnik, Joshua C.

    Surface wave analysis of both earthquake and ambient noise seismic data from arrays of broadband seismic stations provides new high resolution images of shear wave velocity of the crust and upper mantle in western North America. In the Yellowstone Hotspot region, new constraints are shown on the high velocity midcrustal layer of the eastern Snake River Plain that represents approximately 10 km of magmatic thickening and subsequent forcing of lower crustal outflow. In the Coast Mountain Batholith area of western British Columbia, the lack of a significant region of high velocities in the lower crust indicates that the foundering of negatively buoyant eclogitic lower crust has been efficient. A high resolution shear velocity model of the Sierra Nevada batholith region finds crustal thickening beneath the batholith, sinking material beneath the central Sierras with adjacent upwelling asthenospheric mantle, and the new image suggests that the Isabella (San Joaquin Valley) anomaly has a quasi-planar NW-SE striking geometry perhaps more consistent with being a Monterey plate slab remnant than an eclogite dominated feature. In addition to the surface wave results, new constraints are found on the sharpness of the 410-km velocity discontinuity via the wave-field continuation approach applied to five regional earthquakes in western North America. The 410-km discontinuity gradient ranges from 7-25 km, indicating the presence of water atop the transition zone in the two regions with large 410 km discontinuity gradient widths.

  11. ADVANCED HIGH RESOLUTION SEISMIC IMAGING, MATERIAL PROPERTIES ESTIMATION AND FULL WAVEFIELD INVERSION FOR THE SHALLOW SUBSURFACE

    EPA Science Inventory

    We propose to develop and test an integrated suite of imaging and inverse techniques appropriate to the range of wave propagation regimes customarily recorded in shallow seismic surveys. These techniques will address the extreme physical conditions found in the shallow environmen...

  12. Acoustic Waves in Medical Imaging and Diagnostics

    PubMed Central

    Sarvazyan, Armen P.; Urban, Matthew W.; Greenleaf, James F.

    2013-01-01

    Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term “ultrasonography,” or its abbreviated version “sonography” meant an imaging modality based on the use of ultrasonic compressional bulk waves. Since the 1990s numerous acoustic imaging modalities started to emerge based on the use of a different mode of acoustic wave: shear waves. It was demonstrated that imaging with these waves can provide very useful and very different information about the biological tissue being examined. We will discuss physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities, and frequencies that have been used in different imaging applications will be presented. We will discuss the potential for future shear wave imaging applications. PMID:23643056

  13. Acoustic imaging microscope

    DOEpatents

    Deason, Vance A.; Telschow, Kenneth L.

    2006-10-17

    An imaging system includes: an object wavefront source and an optical microscope objective all positioned to direct an object wavefront onto an area of a vibrating subject surface encompassed by a field of view of the microscope objective, and to direct a modulated object wavefront reflected from the encompassed surface area through a photorefractive material; and a reference wavefront source and at least one phase modulator all positioned to direct a reference wavefront through the phase modulator and to direct a modulated reference wavefront from the phase modulator through the photorefractive material to interfere with the modulated object wavefront. The photorefractive material has a composition and a position such that interference of the modulated object wavefront and modulated reference wavefront occurs within the photorefractive material, providing a full-field, real-time image signal of the encompassed surface area.

  14. Geometry of the Farallon Slab Revealed by Joint Interpretation of Wavefield Imaging and Tomography Results from the Earthscope Transportable Array

    NASA Astrophysics Data System (ADS)

    Pavlis, G. L.; Wang, Y.

    2015-12-01

    A significant number of P and S wave tomography models have been produced in the past decade using various subsets of data from the Earthscope USArray and different inversion algorithms. We focus here on published tomography results that span large portions of the final footprint of the USArray. We use 3D visualization techniques to search for common features in different tomography models. We also compare tomography results to features seen in our current generation wavefield images. Recent innovations of our plane wave migration method have yielded what is arguably the highest resolution image ever produced of the mantle in the vicinity of the transition zone. The new results reveal a rich collection of coherent, dipping structures seen throughout the upper mantle and transition zone. These dipping interfaces are judged significant according to a coherence metric. We treat these surfaces as strain markers to assess proposed models for geometry of the 3D geometry of the Farallon Slab under North America. We find the following geologic interpretations are well supported by independent results: 1. The old Farallon under eastern North America and below the base of transition zone is universally seen as a high velocity anomaly. 2. All results support a simple, 3D kinematic model of the updip limit of the Farallon slab window that follows a track from Cape Mendocino, across Nevada, and northern Arizona and New Mexico. 3. All models show a strong low-velocity mantle under the southwestern U.S. 4. A low-velocity features is universally seen related to the Yellowstone-Snake River system. Shorter wavelength features observed in different tomography models are inconsistent showing that the theme of this session is very important to understand what features are in current results are real. Isopach maps of the thickness of the transition show a systematic difference in transition zone thickness in the western and eastern US. The transition zone thickens in the eastern US in

  15. Reflective echo tomographic imaging using acoustic beams

    DOEpatents

    Kisner, Roger; Santos-Villalobos, Hector J

    2014-11-25

    An inspection system includes a plurality of acoustic beamformers, where each of the plurality of acoustic beamformers including a plurality of acoustic transmitter elements. The system also includes at least one controller configured for causing each of the plurality of acoustic beamformers to generate an acoustic beam directed to a point in a volume of interest during a first time. Based on a reflected wave intensity detected at a plurality of acoustic receiver elements, an image of the volume of interest can be generated.

  16. First images of thunder: Acoustic imaging of triggered lightning

    NASA Astrophysics Data System (ADS)

    Dayeh, M. A.; Evans, N. D.; Fuselier, S. A.; Trevino, J.; Ramaekers, J.; Dwyer, J. R.; Lucia, R.; Rassoul, H. K.; Kotovsky, D. A.; Jordan, D. M.; Uman, M. A.

    2015-07-01

    An acoustic camera comprising a linear microphone array is used to image the thunder signature of triggered lightning. Measurements were taken at the International Center for Lightning Research and Testing in Camp Blanding, FL, during the summer of 2014. The array was positioned in an end-fire orientation thus enabling the peak acoustic reception pattern to be steered vertically with a frequency-dependent spatial resolution. On 14 July 2014, a lightning event with nine return strokes was successfully triggered. We present the first acoustic images of individual return strokes at high frequencies (>1 kHz) and compare the acoustically inferred profile with optical images. We find (i) a strong correlation between the return stroke peak current and the radiated acoustic pressure and (ii) an acoustic signature from an M component current pulse with an unusual fast rise time. These results show that acoustic imaging enables clear identification and quantification of thunder sources as a function of lightning channel altitude.

  17. Acoustic 3D imaging of dental structures

    SciTech Connect

    Lewis, D.K.; Hume, W.R.; Douglass, G.D.

    1997-02-01

    Our goals for the first year of this three dimensional electodynamic imaging project was to determine how to combine flexible, individual addressable; preprocessing of array source signals; spectral extrapolation or received signals; acoustic tomography codes; and acoustic propagation modeling code. We investigated flexible, individually addressable acoustic array material to find the best match in power, sensitivity and cost and settled on PVDF sheet arrays and 3-1 composite material.

  18. Imaging marine geophysical environments with vector acoustics.

    PubMed

    Lindwall, Dennis

    2006-09-01

    Using vector acoustic sensors for marine geoacoustic surveys instead of the usual scalar hydrophones enables one to acquire three-dimensional (3D) survey data with instrumentation and logistics similar to current 2D surveys. Vector acoustic sensors measure the sound wave direction directly without the cumbersome arrays that hydrophones require. This concept was tested by a scaled experiment in an acoustic water tank that had a well-controlled environment with a few targets. Using vector acoustic data from a single line of sources, the three-dimensional tank environment was imaged by directly locating the source and all reflectors. PMID:17004497

  19. Finite-difference modelling of wavefield constituents

    NASA Astrophysics Data System (ADS)

    Robertsson, Johan O. A.; van Manen, Dirk-Jan; Schmelzbach, Cedric; Van Renterghem, Cederic; Amundsen, Lasse

    2015-11-01

    The finite-difference method is among the most popular methods for modelling seismic wave propagation. Although the method has enjoyed huge success for its ability to produce full wavefield seismograms in complex models, it has one major limitation which is of critical importance for many modelling applications; to naturally output up- and downgoing and P- and S-wave constituents of synthesized seismograms. In this paper, we show how such wavefield constituents can be isolated in finite-difference-computed synthetics in complex models with high numerical precision by means of a simple algorithm. The description focuses on up- and downgoing and P- and S-wave separation of data generated using an isotropic elastic finite-difference modelling method. However, the same principles can also be applied to acoustic, electromagnetic and other wave equations.

  20. A Klein-Gordon acoustic theory

    SciTech Connect

    Anno, P.D.

    1992-12-01

    Geophysicists do not associate traveltime variation with density variation in acoustic or elastic wavefield interpretation. Rather, given a constant index of refraction, density variation within the medium of propagation is associated only with amplitudes. This point of view prevails because density does not occur as a variable in classical results such as Snell's Law or the eikonal equation. Nevertheless, in this paper I predict, analytically, a continuum of density effects on acoustic wavefields-including a dispersive traveltime delay when density variation is rapid. I also examine the ability of a common imaging algorithm to cope with this time delay.

  1. A Klein-Gordon acoustic theory

    SciTech Connect

    Anno, P.D.

    1992-12-01

    Geophysicists do not associate traveltime variation with density variation in acoustic or elastic wavefield interpretation. Rather, given a constant index of refraction, density variation within the medium of propagation is associated only with amplitudes. This point of view prevails because density does not occur as a variable in classical results such as Snell`s Law or the eikonal equation. Nevertheless, in this paper I predict, analytically, a continuum of density effects on acoustic wavefields-including a dispersive traveltime delay when density variation is rapid. I also examine the ability of a common imaging algorithm to cope with this time delay.

  2. Pulsed-Source Interferometry in Acoustic Imaging

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill; Gutierrez, Roman; Tang, Tony K.

    2003-01-01

    A combination of pulsed-source interferometry and acoustic diffraction has been proposed for use in imaging subsurface microscopic defects and other features in such diverse objects as integrated-circuit chips, specimens of materials, and mechanical parts. A specimen to be inspected by this technique would be mounted with its bottom side in contact with an acoustic transducer driven by a continuous-wave acoustic signal at a suitable frequency, which could be as low as a megahertz or as high as a few hundred gigahertz. The top side of the specimen would be coupled to an object that would have a flat (when not vibrating) top surface and that would serve as the acoustical analog of an optical medium (in effect, an acoustical "optic").

  3. Finite element modelling for the investigation of edge effect in acoustic micro imaging of microelectronic packages

    NASA Astrophysics Data System (ADS)

    Shen Lee, Chean; Zhang, Guang-Ming; Harvey, David M.; Ma, Hong-Wei; Braden, Derek R.

    2016-02-01

    In acoustic micro imaging of microelectronic packages, edge effect is often presented as artifacts of C-scan images, which may potentially obscure the detection of defects such as cracks and voids in the solder joints. The cause of edge effect is debatable. In this paper, a 2D finite element model is developed on the basis of acoustic micro imaging of a flip-chip package using a 230 MHz focused transducer to investigate acoustic propagation inside the package in attempt to elucidate the fundamental mechanism that causes the edge effect. A virtual transducer is designed in the finite element model to reduce the coupling fluid domain, and its performance is characterised against the physical transducer specification. The numerical results showed that the under bump metallization (UBM) structure inside the package has a significant impact on the edge effect. Simulated wavefields also showed that the edge effect is mainly attributed to the horizontal scatter, which is observed in the interface of silicon die-to-the outer radius of solder bump. The horizontal scatter occurs even for a flip-chip package without the UBM structure.

  4. Isolation of ultrasonic scattering by wavefield baseline subtraction

    NASA Astrophysics Data System (ADS)

    Dawson, Alexander J.; Michaels, Jennifer E.; Michaels, Thomas E.

    2016-03-01

    Wavefield imaging generally refers to the measurement of signals over a two-dimensional rectilinear grid that originate from a spatially fixed source. Subtraction of such wavefields is investigated as a means of separating scattered signals from the total wavefield; that is, baseline wavefield data acquired from a defect-free specimen are subtracted from analogous data acquired after introduction of a defect. The wavefields considered here are generated by a 5 MHz angle-beam probe and measured over an area of the accessible specimen surface using a laser vibrometer. The primary challenge in isolating the scattered waves is imperfect temporal and spatial alignment of the two wavefields. Two methods for aligning the wavefields in space and time prior to performing baseline subtraction are presented and their efficacy is evaluated using data acquired before and after introducing notches that originate from a through-hole. Although perfect baseline subtraction is not achieved, the improvement in performance after alignment using either method allows for scattered waves from small defects to be separated and visualized, even when their amplitudes are much smaller than those of the incident waves.

  5. Imaging of Acoustic Waves in Sand

    SciTech Connect

    Deason, Vance Albert; Telschow, Kenneth Louis; Watson, Scott Marshall

    2003-08-01

    There is considerable interest in detecting objects such as landmines shallowly buried in loose earth or sand. Various techniques involving microwave, acoustic, thermal and magnetic sensors have been used to detect such objects. Acoustic and microwave sensors have shown promise, especially if used together. In most cases, the sensor package is scanned over an area to eventually build up an image or map of anomalies. We are proposing an alternate, acoustic method that directly provides an image of acoustic waves in sand or soil, and their interaction with buried objects. The INEEL Laser Ultrasonic Camera utilizes dynamic holography within photorefractive recording materials. This permits one to image and demodulate acoustic waves on surfaces in real time, without scanning. A video image is produced where intensity is directly and linearly proportional to surface motion. Both specular and diffusely reflecting surfaces can be accomodated and surface motion as small as 0.1 nm can be quantitatively detected. This system was used to directly image acoustic surface waves in sand as well as in solid objects. Waves as frequencies of 16 kHz were generated using modified acoustic speakers. These waves were directed through sand toward partially buried objects. The sand container was not on a vibration isolation table, but sat on the lab floor. Interaction of wavefronts with buried objects showed reflection, diffraction and interference effects that could provide clues to location and characteristics of buried objects. Although results are preliminary, success in this effort suggests that this method could be applied to detection of buried landmines or other near-surface items such as pipes and tanks.

  6. Wavefield separation and polarity reversal correction in elastic reverse time migration

    NASA Astrophysics Data System (ADS)

    Li, Zhiyuan; Ma, Xiaona; Fu, Chao; Liang, Guanghe

    2016-04-01

    In elastic reverse time migration (RTM), one of the problems that are often encountered is the cross-talk between P- and S-wavefields. A useful processing technique to reduce the cross-talk is separating the P- and S-wavefields by using divergence and curl operators before applying an elastic imaging condition. However, the separated wavefields lose their physical meaning because their phase and amplitude are changed. In this paper, we modify the divergence and curl operators to give the separated wavefields a clear physical meaning: the separated wavefield is the first derivative of the input wavefield with respect to time. Another problem often encountered is polarity reversals in PS and SP images, which can cause destructive interference in the final stacked image and thus destroy the migrated events. In this paper we also develop a procedure for polarity reversal correction based on the polarization vectors of the P- and S-wavefields in the common-shot domain. The correction factor is first calculated at every imaging point during the wavefield reconstruction and is then multiplied by the PS and SP images at each time step when an elastic imaging condition is applied. Numerical examples with synthetic data have shown that the modified wavefield separation method is correct, and the procedure of polarity reversal correction is effective for a complex model.

  7. Acoustic imaging systems (for robotic object acquisition)

    NASA Astrophysics Data System (ADS)

    Richardson, J. M.; Martin, J. F.; Marsh, K. A.; Schoenwald, J. S.

    1985-03-01

    The long-term objective of the effort is to establish successful approaches for 3D acoustic imaging of dense solid objects in air to provide the information required for acquisition and manipulation of these objects by a robotic system. The objective of this first year's work was to achieve and demonstrate the determination of the external geometry (shape) of such objects with a fixed sparse array of sensors, without the aid of geometrical models or extensive training procedures. Conventional approaches for acoustic imaging fall into two basic categories. The first category is used exclusively for dense solid objects. It involves echo-ranging from a large number of sensor positions, achieved either through the use of a larger array of transducers or through extensive physical scanning of a small array. This approach determines the distance to specular reflection points from each sensor position; with suitable processing an image can be inferred. The second category uses the full acoustic waveforms to provide an image, but is strictly applicable only to weak inhomogeneities. The most familiar example is medical imaging of the soft tissue portions of the body where the range of acoustic impedance is relatively small.

  8. Advanced high resolution seismic imaging, material properties estimation and full wavefield inversion for the shallow subsurface. 1998 annual progress report

    SciTech Connect

    Levander, A.; Zelt, C.A.; Symes, W.W.

    1998-06-01

    'The authors are developing advanced seismic data processing, imaging, and inversion methods for high resolution seismic reflection/refraction imaging and material property estimation of the shallow subsurface. The imaging methods are being developed to map the structural and material properties of aquifers and aquitards. This report summarizes work completed in the first seven months of a three year project which began in November 1997. The research is proceeding along three lines: data acquisition, data processing, and algorithm development.'

  9. Magnetic resonance acoustic radiation force imaging

    PubMed Central

    McDannold, Nathan; Maier, Stephan E.

    2008-01-01

    Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery. PMID:18777934

  10. Underwater imaging with a moving acoustic lens.

    PubMed

    Kamgar-Parsi, B; Rosenblum, L J; Belcher, E O

    1998-01-01

    The acoustic lens is a high-resolution, forward-looking sonar for three dimensional (3-D) underwater imaging. We discuss processing the lens data for recreating and visualizing the scene. Acoustical imaging, compared to optical imaging, is sparse and low resolution. To achieve higher resolution, we obtain a denser sample by mounting the lens on a moving platform and passing over the scene. This introduces the problem of data fusion from multiple overlapping views for scene formation, which we discuss. We also discuss the improvements in object reconstruction by combining data from several passes over an object. We present algorithms for pass registration and show that this process can be done with enough accuracy to improve the image and provide greater detail about the object. The results of in-water experiments show the degree to which size and shape can be obtained under (nearly) ideal conditions. PMID:18267382

  11. Explicit Fourier wavefield operators

    NASA Astrophysics Data System (ADS)

    Ferguson, R. J.; Margrave, G. F.

    2006-04-01

    Explicit wavefield extrapolators are based on direct analytic mathematical formulae that express the output as an extrapolation operator acting on the input, while implicit methods usually require the calculation of the numerical inverse of a matrix to obtain the output. Typically, explicit methods are faster than implicit methods, and they often give more insight into the physics of the wave propagation, but they often suffer from instability. Four different explicit extrapolators based on Fourier theory are presented and analysed. They are: PS (ordinary phase shift), GPSPI (generalized phase shift plus interpolation), NSPS (non-stationary phase shift) and SNPS (symmetric non-stationary phase shift). A formal proof is given that NSPS in a direction orthogonal to the velocity gradient is the mathematical adjoint process to GPSPI in the opposite direction. This motivates the construction of SNPS that combines NSPS and GPSPI in a symmetric fashion. This symmetry (under interchange of input and output lateral coordinates) is required by reciprocity arguments. PS and SNPS are symmetric while NSPS and GPSPI are not. A numerical stability study using SVD (singular value decomposition) shows that all of these extrapolators can become unstable for strong lateral velocity gradients. Unstable operators allow amplitudes to grow non-physically in a recursion. Stability is enhanced by introducing a small (~3 per cent) imaginary component to the velocities. This causes a numerical attenuation that tends to stabilize the operators but does not address the cause of the instability. For the velocity model studied (a very challenging case) GPSPI and NSPS have exactly the same instability while SNPS is always more stable. Instability manifests in a complicated way as a function of extrapolation step size, frequency, velocity gradient, and strength of numerical attenuation. The SNPS operator can be stabilized over a wide range of conditions with considerably less attenuation than is

  12. Roughness of the Mantle Transition Zone Discontinuities Revealed by High Resolution Wavefield Imaging with the Earthscope Transportable Array

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Pavlis, G. L.

    2015-12-01

    We post-processed 141,080 pairs of high quality radial and transverse receiver functions from the Earthscope Automated Receiver Survey using a variant of what we have called generalized iterative deconvolution method and reshaped the spiking output into different scales of Ricker wavelets. We then used these data as input to our 3D plane wave migration method to produce an image volume of P to S scattering surfaces under all of the lower 48 states. The result is arguably the highest resolution image ever produce of the mantle transition zone. Due to the effect of migration impulse response, different scales of Ricker wavelets provide another important means of controlling the resolution of the image produced by 3D plane wave migration method. Model simulation shows that comparing to the widely used CCP stacking method with receiver functions shaped by Gaussian wavelet, the application of our methods is capable of resolving not only dipping discontinuities but also more subtle details of the discontinuities. Application to the latest USArray data reveals several previously unobserved features of the 410 and 660 discontinuities. Both discontinuities are resolved to a precision approaching 1 km under the stable interior, but degrading to the order of 10 km in the western US due to a probably combination of higher attenuation and velocity heterogeneity not resolved by current generation tomography models. Topography with many 10s of km is resolved at a range of scales. In addition, we observe large variation of relative amplitude on the radial component and large variations in the radial to transverse amplitude ratio that correlate with inferred variations in discontinuity topography. We argue this combination of observations can be explained by roughness at a range of scales. Roughness is consistent with the phase-change model for these discontinuities given there is little reason to think the mantle is homogeneous at these distance scales. Continental scale isopach

  13. Challenges in the separation and analysis of scattered waves in angle-beam wavefield data

    SciTech Connect

    Dawson, Alexander J.; Michaels, Jennifer E.; Michaels, Thomas E.

    2015-03-31

    The measurement of ultrasonic signals on a 2-D rectilinear grid resulting from a fixed source, referred to as wavefield imaging, is a powerful tool for visualizing wave propagation and scattering. Wavefield imaging provides a more complete picture of wave propagation than conventional single-point measurements, but creates more challenges for analysis. This work considers the development of wavefield-based methods for analyzing angle-beam wave propagation and scattering in plates. Methods of analysis focus on the separation of scattered waves from the total wavefield with the eventual goal of quantitative scatterer characterization in a laboratory environment. Two methods for wave separation are considered: frequency-wavenumber filtering and wavefield baseline subtraction. Frequency-wavenumber filtering is applied to wavefield data that are finely sampled in both space and time, whereas baseline subtraction is a technique that has typically been applied to individual signals recorded from fixed transducers rather than to full wavefield data. Baseline subtraction of wavefields, particularly for the frequency range considered here, is sensitive to both specimen alignment and temperature variations, whereas frequency-wavenumber methods are limited in their ability to separate waves traveling in the same direction. Results are shown for both methods with a focus on investigating and overcoming the challenges to full wavefield baseline subtraction.

  14. Quantitative Ultrasound Imaging Using Acoustic Backscatter Coefficients.

    NASA Astrophysics Data System (ADS)

    Boote, Evan Jeffery

    Current clinical ultrasound scanners render images which have brightness levels related to the degree of backscattered energy from the tissue being imaged. These images offer the interpreter a qualitative impression of the scattering characteristics of the tissue being examined, but due to the complex factors which affect the amplitude and character of the echoed acoustic energy, it is difficult to make quantitative assessments of scattering nature of the tissue, and thus, difficult to make precise diagnosis when subtle disease effects are present. In this dissertation, a method of data reduction for determining acoustic backscatter coefficients is adapted for use in forming quantitative ultrasound images of this parameter. In these images, the brightness level of an individual pixel corresponds to the backscatter coefficient determined for the spatial position represented by that pixel. The data reduction method utilized rigorously accounts for extraneous factors which affect the scattered echo waveform and has been demonstrated to accurately determine backscatter coefficients under a wide range of conditions. The algorithms and procedures used to form backscatter coefficient images are described. These were tested using tissue-mimicking phantoms which have regions of varying scattering levels. Another phantom has a fat-mimicking layer for testing these techniques under more clinically relevant conditions. Backscatter coefficient images were also formed of in vitro human liver tissue. A clinical ultrasound scanner has been adapted for use as a backscatter coefficient imaging platform. The digital interface between the scanner and the computer used for data reduction are described. Initial tests, using phantoms are presented. A study of backscatter coefficient imaging of in vivo liver was performed using several normal, healthy human subjects.

  15. Acoustic Imaging of Snowpack Physical Properties

    NASA Astrophysics Data System (ADS)

    Kinar, N. J.; Pomeroy, J. W.

    2011-12-01

    Measurements of snowpack depth, density, structure and temperature have often been conducted by the use of snowpits and invasive measurement devices. Previous research has shown that acoustic waves passing through snow are capable of measuring these properties. An experimental observation device (SAS2, System for the Acoustic Sounding of Snow) was used to autonomously send audible sound waves into the top of the snowpack and to receive and process the waves reflected from the interior and bottom of the snowpack. A loudspeaker and microphone array separated by an offset distance was suspended in the air above the surface of the snowpack. Sound waves produced from a loudspeaker as frequency-swept sequences and maximum length sequences were used as source signals. Up to 24 microphones measured the audible signal from the snowpack. The signal-to-noise ratio was compared between sequences in the presence of environmental noise contributed by wind and reflections from vegetation. Beamforming algorithms were used to reject spurious reflections and to compensate for movement of the sensor assembly during the time of data collection. A custom-designed circuit with digital signal processing hardware implemented an inversion algorithm to relate the reflected sound wave data to snowpack physical properties and to create a two-dimensional image of snowpack stratigraphy. The low power consumption circuit was powered by batteries and through WiFi and Bluetooth interfaces enabled the display of processed data on a mobile device. Acoustic observations were logged to an SD card after each measurement. The SAS2 system was deployed at remote field locations in the Rocky Mountains of Alberta, Canada. Acoustic snow properties data was compared with data collected from gravimetric sampling, thermocouple arrays, radiometers and snowpit observations of density, stratigraphy and crystal structure. Aspects for further research and limitations of the acoustic sensing system are also discussed.

  16. Impact Induced Delamination Detection and Quantification With Guided Wavefield Analysis

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Leckey, Cara A. C.; Yu, Lingyu; Seebo, Jeffrey P.

    2015-01-01

    This paper studies impact induced delamination detection and quantification by using guided wavefield data and spatial wavenumber imaging. The complex geometry impact-like delamination is created through a quasi-static indentation on a CFRP plate. To detect and quantify the impact delamination in the CFRP plate, PZT-SLDV sensing and spatial wavenumber imaging are performed. In the PZT-SLDV sensing, the guided waves are generated from the PZT, and the high spatial resolution guided wavefields are measured by the SLDV. The guided wavefield data acquired from the PZT-SLDV sensing represent guided wave propagation in the composite laminate and include guided wave interaction with the delamination damage. The measured guided wavefields are analyzed through the spatial wavenumber imaging method, which generates an image containing the dominant local wavenumber at each spatial location. The spatial wavenumber imaging result for the simple single layer Teflon insert delamination provided quantitative information on delamination damage size and location. The location of delamination damage is indicated by the area with larger wavenumbers in the spatial wavenumber image. The impact-like delamination results only partially agreed with the damage size and shape. The results also demonstrated the dependence on excitation frequency. Future work will further investigate the accuracy of the wavenumber imaging method for real composite damage and the dependence on frequency of excitation.

  17. Imaging of 3D Ocean Turbulence Microstructure Using Low Frequency Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Minakov, Alexander; Kolyukhin, Dmitriy; Keers, Henk

    2015-04-01

    In the past decade the technique of imaging the ocean structure with low-frequency signal (Hz), produced by air-guns and typically employed during conventional multichannel seismic data acquisition, has emerged. The method is based on extracting and stacking the acoustic energy back-scattered by the ocean temperature and salinity micro- and meso-structure (1 - 100 meters). However, a good understanding of the link between the scattered wavefield utilized by the seismic oceanography and physical processes in the ocean is still lacking. We describe theory and the numerical implementation of a 3D time-dependent stochastic model of ocean turbulence. The velocity and temperature are simulated as homogeneous Gaussian isotropic random fields with the Kolmogorov-Obukhov energy spectrum in the inertial subrange. Numerical modeling technique is employed for sampling of realizations of random fields with a given spatial-temporal spectral tensor. The model used is shown to be representative for a wide range of scales. Using this model, we provide a framework to solve the forward and inverse acoustic scattering problem using marine seismic data. Our full-waveform inversion method is based on the ray-Born approximation which is specifically suitable for the modelling of small velocity perturbations in the ocean. This is illustrated by showing a good match between synthetic seismograms computed using ray-Born and synthetic seismograms produced with a more computationally expensive finite-difference method.

  18. Three-dimensional full-wavefield seismic tomography on field data (Invited)

    NASA Astrophysics Data System (ADS)

    Warner, M.; Umpleby, A.; Stekl, I.; Guasch, L.

    2010-12-01

    In contrast to conventional seismic tomography, where we minimise the mismatch between observed and calculated seismic travel times, in full-wavefield tomography we seek a model that is able to match the entire observed wavefield, wiggle-for-wiggle. Wavefield tomography has a long history, but it is only recently that advances in algorithms and in hardware have made the technique feasible on realistic-sized datasets in three dimensions. With sponsorship from the petroleum industry, we have developed full 3D codes for anisotropic acoustic, and isotropic elastic, wavefield tomography in the time-domain, and for visco-acoustic tomography in the frequency domain. In both domains, we solve the wave equation using finite differences on a regular mesh; we use explicit time-stepping in the time domain, and use an implicit iterative solver in the frequency domain. The codes are parallelised to run on a cluster of multi-core nodes, and they are able to deal with large irregular 3D datasets efficiently. We report here the results of applying these codes to a 3D ocean-bottom seismic dataset acquired over the Tommeliten oil field in the North Sea. The field data are composed of 1920 four-component ocean-bottom receivers, recording about 30,000 air-gun sources over an area of 12 x 9 km. A low-velocity, high-attenuation gas cloud is located at a depth of 1 to 2 km; this gas cloud partially obscures the geology of the underlying oil field. There is significant anisotropy within the section; vertical and horizontal p-wave velocities can differ by more than 15%. Wavefield tomography is successful in imaging the complex velocity structure in 3D within this gas cloud with a lateral resolution of about 25 m. This resolution is much better than that obtained using reflection travel-time tomography or migration velocity analysis. Subsequent pre-stack reverse-time depth migration of the underlying reflection data demonstrates that the recovered velocity structure is real. It is necessary

  19. True-amplitude wavefield separation using staggered-grid interpolation in the wavenumber domain

    NASA Astrophysics Data System (ADS)

    Du, Qi-Zhen; Zhang, Ming-Qiang; Chen, Xiao-Ran; Gong, Xu-Fei; Guo, Cheng-Feng

    2014-12-01

    Wavefield separation of multicomponent seismic data to image subsurface structures can be realized in either the space domain or the wavenumber domain. However, as the particle velocity components used in the wavenumber-domain wavefield separation are not defined at the same grid point with the staggered-grid finite-difference method for elastic wavefield simulation, we propose the wavenumber-domain interpolation method to estimate the required values at the common grid points prior to the wavenumber-domain true-amplitude wavefield separation. Moreover, numerical experiments show that the wavenumber-domain interpolation method has high interpolation accuracy and the trueamplitude wavefield separation method shows good amplitude preservation. The application of the proposed methodology to elastic reverse-time migration can obtain good amplitudepreserved images even in the case of some velocity error.

  20. Method and apparatus for acoustic imaging of objects in water

    DOEpatents

    Deason, Vance A.; Telschow, Kenneth L.

    2005-01-25

    A method, system and underwater camera for acoustic imaging of objects in water or other liquids includes an acoustic source for generating an acoustic wavefront for reflecting from a target object as a reflected wavefront. The reflected acoustic wavefront deforms a screen on an acoustic side and correspondingly deforms the opposing optical side of the screen. An optical processing system is optically coupled to the optical side of the screen and converts the deformations on the optical side of the screen into an optical intensity image of the target object.

  1. Imaging of acoustic fields using optical feedback interferometry.

    PubMed

    Bertling, Karl; Perchoux, Julien; Taimre, Thomas; Malkin, Robert; Robert, Daniel; Rakić, Aleksandar D; Bosch, Thierry

    2014-12-01

    This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes. PMID:25606963

  2. Interpreting Underwater Acoustic Images of the Upper Ocean Boundary Layer

    ERIC Educational Resources Information Center

    Ulloa, Marco J.

    2007-01-01

    A challenging task in physical studies of the upper ocean using underwater sound is the interpretation of high-resolution acoustic images. This paper covers a number of basic concepts necessary for undergraduate and postgraduate students to identify the most distinctive features of the images, providing a link with the acoustic signatures of…

  3. Efficient elastic reverse-time migration for the decomposed P-wavefield using stress tensor in the time domain

    NASA Astrophysics Data System (ADS)

    Ha, Jiho; Shin, Sungryul; Shin, Changsoo; Chung, Wookeen

    2015-05-01

    Because complex mixed waves are typically generated in elastic media, wavefield decomposition is required for such media to obtain migration images accurately. In isotropic media, this is achieved according to the Helmholtz decomposition theorem; in particular, the divergence operator is commonly applied to P-wavefield decomposition. In this study, two types of elastic reverse-time migration algorithms are proposed for decomposition of the P-wavefield without requiring the divergence operator. The first algorithm involves formulation of the stress tensor by spatially differentiated displacement according to the stress-strain relationship and is utilized to construct an imaging condition for the decomposed P-wavefield. We demonstrate this approach through numerical testing. The second algorithm allows us to obtain emphasized interfaces through the application of the absolute value function to decomposed wavefield in imaging condition. Because reverse-time migration can be defined by a zero-lag cross-correlation relationship between the partial-derivative wavefield and the observed wavefield data, we derive the virtual source to construct the partial-derivative wavefield based on a 2D staggered-grid finite-difference modeling method in the time domain. The explicitly computed partial-derivative wavefield from virtual sources with the stress tensor is in agreement with the partial-derivative wavefield directly computed from residual by between with and without a perturbation point in the subsurface. Moreover, the back-propagation technique is used to enhance the computational efficiency. To validate our two types of imaging conditions, numerical tests are conducted. The migration images created according to our imaging conditions can represent the subsurface structure accurately. Thus, we can confirm the feasibility of obtaining migration images of the decomposed P-wavefield without requiring the application of the divergence operator.

  4. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Bradway, David Pierson

    This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal

  5. Laser-induced acoustic imaging of underground objects

    NASA Astrophysics Data System (ADS)

    Li, Wen; DiMarzio, Charles A.; McKnight, Stephen W.; Sauermann, Gerhard O.; Miller, Eric L.

    1999-02-01

    This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO2 laser. Research has been focused on the signal acquisition and signal processing. A deconvolution method using Wiener filters is utilized in data processing. Using a uniform spatial distribution of laser pulses at the ground's surface, we obtained 3D images of buried objects. The images give us a clear representation of the shapes of the underground objects. The quality of the images depends on the mismatch of acoustic impedance of the buried objects, the bandwidth and center frequency of the acoustic sensors and the selection of filter functions.

  6. Optimization of a Biometric System Based on Acoustic Images

    PubMed Central

    Izquierdo Fuente, Alberto; Del Val Puente, Lara; Villacorta Calvo, Juan J.; Raboso Mateos, Mariano

    2014-01-01

    On the basis of an acoustic biometric system that captures 16 acoustic images of a person for 4 frequencies and 4 positions, a study was carried out to improve the performance of the system. On a first stage, an analysis to determine which images provide more information to the system was carried out showing that a set of 12 images allows the system to obtain results that are equivalent to using all of the 16 images. Finally, optimization techniques were used to obtain the set of weights associated with each acoustic image that maximizes the performance of the biometric system. These results improve significantly the performance of the preliminary system, while reducing the time of acquisition and computational burden, since the number of acoustic images was reduced. PMID:24616643

  7. Optimization of a biometric system based on acoustic images.

    PubMed

    Izquierdo Fuente, Alberto; Del Val Puente, Lara; Villacorta Calvo, Juan J; Raboso Mateos, Mariano

    2014-01-01

    On the basis of an acoustic biometric system that captures 16 acoustic images of a person for 4 frequencies and 4 positions, a study was carried out to improve the performance of the system. On a first stage, an analysis to determine which images provide more information to the system was carried out showing that a set of 12 images allows the system to obtain results that are equivalent to using all of the 16 images. Finally, optimization techniques were used to obtain the set of weights associated with each acoustic image that maximizes the performance of the biometric system. These results improve significantly the performance of the preliminary system, while reducing the time of acquisition and computational burden, since the number of acoustic images was reduced. PMID:24616643

  8. Local Guided Wavefield Analysis for Characterization of Delaminations in Composites

    NASA Technical Reports Server (NTRS)

    Rogge, Matthew D.; Campbell Leckey, Cara A.

    2012-01-01

    Delaminations in composite laminates resulting from impact events may be accompanied by minimal indication of damage at the surface. As such, inspection techniques are required to ensure defects are within allowable limits. Conventional ultrasonic scanning techniques have been shown to effectively characterize the size and depth of delaminations but require physical contact with the structure. Alternatively, a noncontact scanning laser vibrometer may be used to measure guided wave propagation in the laminate structure. A local Fourier domain analysis method is presented for processing guided wavefield data to estimate spatially-dependent wavenumber values, which can be used to determine delamination depth. The technique is applied to simulated wavefields and results are analyzed to determine limitations of the technique with regards to determining defect size and depth. Finally, experimental wavefield data obtained in quasi-isotropic carbon fiber reinforced polymer (CFRP) laminates with impact damage is analyzed and wavenumber is measured to an accuracy of 8.5% in the region of shallow delaminations. Keywords: Ultrasonic wavefield imaging, Windowed Fourier transforms, Guided waves, Structural health monitoring, Nondestructive evaluation

  9. Laser Acoustic Imaging of Film Bulk Acoustic Resonator (FBAR) Lateral Mode Dispersion

    SciTech Connect

    Ken L. Telschow

    2004-07-01

    A laser acoustic imaging microscope has been developed that measures acoustic motion with high spatial resolution without scanning. Images are recorded at normal video frame rates and heterodyne principles are used to allow operation at any frequency from Hz to GHz. Fourier transformation of the acoustic amplitude and phase displacement images provides a direct quantitative determination of excited mode wavenumbers at any frequency. Results are presented at frequencies near the first longitudinal thickness mode (~ 900 MHz) demonstrating simultaneous excitation of lateral modes with nonzero wavenumbers in an electrically driven AlN thin film acoustic resonator. Images combined at several frequencies form a direct visualization of lateral mode dispersion relations for the device under test allowing mode identification and a direct measure of specific lateral mode properties. Discussion and analysis of the results are presented in comparison with plate wave modeling of these devices taking account for material anisotropy and multilayer films.

  10. A single-sided homogeneous Green's function representation for holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval

    NASA Astrophysics Data System (ADS)

    Wapenaar, Kees; Thorbecke, Jan; van der Neut, Joost

    2016-04-01

    Green's theorem plays a fundamental role in a diverse range of wavefield imaging applications, such as holographic imaging, inverse scattering, time-reversal acoustics and interferometric Green's function retrieval. In many of those applications, the homogeneous Green's function (i.e. the Green's function of the wave equation without a singularity on the right-hand side) is represented by a closed boundary integral. In practical applications, sources and/or receivers are usually present only on an open surface, which implies that a significant part of the closed boundary integral is by necessity ignored. Here we derive a homogeneous Green's function representation for the common situation that sources and/or receivers are present on an open surface only. We modify the integrand in such a way that it vanishes on the part of the boundary where no sources and receivers are present. As a consequence, the remaining integral along the open surface is an accurate single-sided representation of the homogeneous Green's function. This single-sided representation accounts for all orders of multiple scattering. The new representation significantly improves the aforementioned wavefield imaging applications, particularly in situations where the first-order scattering approximation breaks down.

  11. Combined Photoacoustic-Acoustic Technique for Crack Imaging

    NASA Astrophysics Data System (ADS)

    Zakrzewski, J.; Chigarev, N.; Tournat, V.; Gusev, V.

    2010-01-01

    Nonlinear imaging of a crack by combination of a common photoacoustic imaging technique with additional acoustic loading has been performed. Acoustic signals at two different fundamental frequencies were launched in the sample, one photoacoustically through heating of the sample surface by the intensity-modulated scanning laser beam and another by a piezoelectrical transducer. The acoustic signal at mixed frequencies, generated due to system nonlinearity, has been detected by an accelerometer. Different physical mechanisms of the nonlinearity contributing to the contrast in linear and nonlinear photoacoustic imaging of the crack are discussed.

  12. Axial resolution of laser opto-acoustic imaging: influence of acoustic attenuation and diffraction

    NASA Astrophysics Data System (ADS)

    Esenaliev, Rinat O.; Alma, Herve; Tittel, Frank K.; Oraevsky, Alexander A.

    1998-05-01

    Laser optoacoustic imaging can be applied for characterization of layered and heterogeneous tissue structures in vivo. Accurate tissue characterization may provide: (1) means for medical diagnoses, and (2) pretreatment tissue properties important for therapeutic laser procedures. Axial resolution of the optoacoustic imaging is higher than that of optical imaging. However, the resolution may degrade due to either attenuation of high-frequency ultrasonic waves in tissue, or/and diffraction of low-frequency acoustic waves. The goal of this study was to determine the axial resolution as a function of acoustic attenuation and diffraction upon propagation of laser-induced pressure waves in water with absorbing layer, in breast phantoms, and in biological tissues. Acoustic pressure measurements were performed in absolute values using piezoelectric transducers. A layer or a small sphere of absorbing medium was placed within a medium with lower optical absorption. The distance between the acoustic transducer and the absorbing object was varied, so that the effects of acoustic attenuation and diffraction could be observed. The location of layers or spheres was measured from recorded optoacoustic pressure profiles and compared with real values measured with a micrometer. The experimental results were analyzed using theoretical models for spherical and planar acoustic waves. Our studies demonstrated that despite strong acoustic attenuation of high-frequency ultrasonic waves, the axial resolution of laser optoacoustic imaging may be as high as 20 micrometers for tissue layers located at a 5-mm depth. An axial resolution of 10 micrometers to 20 micrometers was demonstrated for an absorbing layer at a distance of 5 cm in water, when the resolution is affected only by diffraction. Acoustic transducers employed in optoacoustic imaging can have either high sensitivity or fast temporal response. Therefore, a high resolution may not be achieved with sensitive transducers utilized in

  13. Magnetic resonance imaging of acoustic streaming: absorption coefficient and acoustic field shape estimation.

    PubMed

    Madelin, Guillaume; Grucker, Daniel; Franconi, Jean-Michel; Thiaudiere, Eric

    2006-07-01

    In this study, magnetic resonance imaging (MRI) is used to visualize acoustic streaming in liquids. A single-shot spin echo sequence (HASTE) with a saturation band perpendicular to the acoustic beam permits the acquisition of an instantaneous image of the flow due to the application of ultrasound. An average acoustic streaming velocity can be estimated from the MR images, from which the ultrasonic absorption coefficient and the bulk viscosity of different glycerol-water mixtures can be deduced. In the same way, this MRI method could be used to assess the acoustic field and time-average power of ultrasonic transducers in water (or other liquids with known physical properties), after calibration of a geometrical parameter that is dependent on the experimental setup. PMID:16650447

  14. Acoustic radiation force-based elasticity imaging methods

    PubMed Central

    Palmeri, Mark L.; Nightingale, Kathryn R.

    2011-01-01

    Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies. PMID:22419986

  15. Acoustic Radiation Force Elasticity Imaging in Diagnostic Ultrasound

    PubMed Central

    Doherty, Joshua R.; Trahey, Gregg E.; Nightingale, Kathryn R.; Palmeri, Mark L.

    2013-01-01

    The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo, elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed non-invasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods. PMID:23549529

  16. Acoustic force mapping in a hybrid acoustic-optical micromanipulation device supporting high resolution optical imaging.

    PubMed

    Thalhammer, Gregor; McDougall, Craig; MacDonald, Michael Peter; Ritsch-Marte, Monika

    2016-04-12

    Many applications in the life-sciences demand non-contact manipulation tools for forceful but nevertheless delicate handling of various types of sample. Moreover, the system should support high-resolution optical imaging. Here we present a hybrid acoustic/optical manipulation system which utilizes a transparent transducer, making it compatible with high-NA imaging in a microfluidic environment. The powerful acoustic trapping within a layered resonator, which is suitable for highly parallel particle handling, is complemented by the flexibility and selectivity of holographic optical tweezers, with the specimens being under high quality optical monitoring at all times. The dual acoustic/optical nature of the system lends itself to optically measure the exact acoustic force map, by means of direct force measurements on an optically trapped particle. For applications with (ultra-)high demand on the precision of the force measurements, the position of the objective used for the high-NA imaging may have significant influence on the acoustic force map in the probe chamber. We have characterized this influence experimentally and the findings were confirmed by model simulations. We show that it is possible to design the chamber and to choose the operating point in such a way as to avoid perturbations due to the objective lens. Moreover, we found that measuring the electrical impedance of the transducer provides an easy indicator for the acoustic resonances. PMID:27025398

  17. Wavefield tomography in three dimensions: application to field data in the absence of a realistic starting model

    NASA Astrophysics Data System (ADS)

    Warner, Michael; Shah, Nikhil; Guasch, Lluís.; Umpleby, Adrian; Stekl, Ivan; Morgan, Joanna

    2010-05-01

    Wavefield tomography (AKA full waveform inversion) is a method of inverting geophysical field data that seeks to find a quantitative model of physical properties in the subsurface that can be used to generate synthetic data that match field data "wiggle-for-wiggle". It is most often applied to active-source seismic data, but it can also be applied to passive seismic data and to controlled-source electro-magnetic data. The method has significantly higher spatial resolution and fidelity than can be achieved using conventional imaging methods. The first practical methods were developed in 2D, mostly in the frequency domain. Here we report recent algorithmic developments which, coupled with hardware advances, make these methods tractable in three dimensions. We have implemented finite-difference computer codes for 3D acoustic and elastic wavefield tomography by explicit time-stepping in the time-domain, and for visco-acoustic tomography by iterative solution of the implicit matrix equations in the frequency-domain. Unlike the situation in two dimensions, where frequency-domain methods have proven to be far more efficient, in three dimensions both methods require approximately similar computational resource, and have largely complementary properties in terms of their effectiveness. We have applied these methods to a variety of synthetic and real-world problems taken from petroleum, mining and academic field datasets with a variety of 3D acquisition geometries and target depths. These include conventional marine multi-streamer acquisition, multi-azimuth marine OBC, high-resolution land surveys, and deep-ocean single-streamer acquisition. In each case, wavefield tomography was able to obtain a high-resolution high-fidelity velocity model of the heterogeneous overburden, and consequently to improve subsequent depth imaging of an underlying target. One of the serious practical limitations on the wider applicability of wavefield tomography is the necessity to have low

  18. Combination of acoustical radiosity and the image source method.

    PubMed

    Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho; Jacobsen, Finn

    2013-06-01

    A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part. The model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated allows for a dynamic control of the image source production, so that no fixed maximum reflection order is required. The model is optimized for energy impulse response predictions in arbitrary polyhedral rooms. The predictions are validated by comparison with published measured data for a real music studio hall. The proposed model turns out to be promising for acoustic predictions providing a high level of detail and accuracy. PMID:23742350

  19. Acoustic imaging in a water filled metallic pipe

    SciTech Connect

    Kolbe, W.F.; Turko, B.T.; Leskovar, B.

    1984-04-01

    A method is described for the imaging of the interior of a water filled metallic pipe using acoustical techniques. The apparatus consists of an array of 20 acoustic transducers mounted circumferentially around the pipe. Each transducer is pulsed in sequence, and the echos resulting from bubbles in the interior are digitized and processed by a computer to generate an image. The electronic control and digitizing system and the software processing of the echo signals are described. The performance of the apparatus is illustrated by the imaging of simulated bubbles consisting of thin walled glass spheres suspended in the pipe.

  20. Time-Reversal Acoustics and Maximum-Entropy Imaging

    SciTech Connect

    Berryman, J G

    2001-08-22

    Target location is a common problem in acoustical imaging using either passive or active data inversion. Time-reversal methods in acoustics have the important characteristic that they provide a means of determining the eigenfunctions and eigenvalues of the scattering operator for either of these problems. Each eigenfunction may often be approximately associated with an individual scatterer. The resulting decoupling of the scattered field from a collection of targets is a very useful aid to localizing the targets, and suggests a number of imaging and localization algorithms. Two of these are linear subspace methods and maximum-entropy imaging.

  1. Acoustic Radiation Force Impulse (ARFI) Imaging: a Review

    PubMed Central

    Nightingale, Kathy

    2012-01-01

    Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. PMID:22545033

  2. Acoustic-optical imaging without immersion

    NASA Technical Reports Server (NTRS)

    Liu, H.

    1979-01-01

    System using membraneous end wall of Bragg cell to separate test specimen from acoustic transmission medium, operates in real time and uses readily available optical components. System can be easily set up and maintained by people with little or no training in holography.

  3. Quantitative Determination of Lateral Mode Dispersion in Film Bulk Acoustic Resonators through Laser Acoustic Imaging

    SciTech Connect

    Ken Telschow; John D. Larson III

    2006-10-01

    Film Bulk Acoustic Resonators are useful for many signal processing applications. Detailed knowledge of their operation properties are needed to optimize their design for specific applications. The finite size of these resonators precludes their use in single acoustic modes; rather, multiple wave modes, such as, lateral wave modes are always excited concurrently. In order to determine the contributions of these modes, we have been using a newly developed full-field laser acoustic imaging approach to directly measure their amplitude and phase throughout the resonator. This paper describes new results comparing modeling of both elastic and piezoelectric effects in the active material with imaging measurement of all excited modes. Fourier transformation of the acoustic amplitude and phase displacement images provides a quantitative determination of excited mode amplitude and wavenumber at any frequency. Images combined at several frequencies form a direct visualization of lateral mode excitation and dispersion for the device under test allowing mode identification and comparison with predicted operational properties. Discussion and analysis are presented for modes near the first longitudinal thickness resonance (~900 MHz) in an AlN thin film resonator. Plate wave modeling, taking account of material crystalline orientation, elastic and piezoelectric properties and overlayer metallic films, will be discussed in relation to direct image measurements.

  4. Synthetic aperture acoustic imaging of non-metallic cords

    NASA Astrophysics Data System (ADS)

    Glean, Aldo A. J.; Good, Chelsea E.; Vignola, Joseph F.; Judge, John A.; Ryan, Teresa J.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

    2012-06-01

    This work presents a set of measurements collected with a research prototype synthetic aperture acoustic (SAA) imaging system. SAA imaging is an emerging technique that can serve as an inexpensive alternative or logical complement to synthetic aperture radar (SAR). The SAA imaging system uses an acoustic transceiver (speaker and microphone) to project acoustic radiation and record backscatter from a scene. The backscattered acoustic energy is used to generate information about the location, morphology, and mechanical properties of various objects. SAA detection has a potential advantage when compared to SAR in that non-metallic objects are not readily detectable with SAR. To demonstrate basic capability of the approach with non-metallic objects, targets are placed in a simple, featureless scene. Nylon cords of five diameters, ranging from 2 to 15 mm, and a joined pair of 3 mm fiber optic cables are placed in various configurations on flat asphalt that is free of clutter. The measurements were made using a chirp with a bandwidth of 2-15 kHz. The recorded signal is reconstructed to form a two-dimensional image of the distribution of acoustic scatterers within the scene. The goal of this study was to identify basic detectability characteristics for a range of sizes and configurations of non-metallic cord. It is shown that for sufficiently small angles relative to the transceiver path, the SAA approach creates adequate backscatter for detectability.

  5. Performance evaluation of a biometric system based on acoustic images.

    PubMed

    Izquierdo-Fuente, Alberto; del Val, Lara; Jiménez, María I; Villacorta, Juan J

    2011-01-01

    An acoustic electronic scanning array for acquiring images from a person using a biometric application is developed. Based on pulse-echo techniques, multifrequency acoustic images are obtained for a set of positions of a person (front, front with arms outstretched, back and side). Two Uniform Linear Arrays (ULA) with 15 λ/2-equispaced sensors have been employed, using different spatial apertures in order to reduce sidelobe levels. Working frequencies have been designed on the basis of the main lobe width, the grating lobe levels and the frequency responses of people and sensors. For a case-study with 10 people, the acoustic profiles, formed by all images acquired, are evaluated and compared in a mean square error sense. Finally, system performance, using False Match Rate (FMR)/False Non-Match Rate (FNMR) parameters and the Receiver Operating Characteristic (ROC) curve, is evaluated. On the basis of the obtained results, this system could be used for biometric applications. PMID:22163708

  6. Performance Evaluation of a Biometric System Based on Acoustic Images

    PubMed Central

    Izquierdo-Fuente, Alberto; del Val, Lara; Jiménez, María I.; Villacorta, Juan J.

    2011-01-01

    An acoustic electronic scanning array for acquiring images from a person using a biometric application is developed. Based on pulse-echo techniques, multifrequency acoustic images are obtained for a set of positions of a person (front, front with arms outstretched, back and side). Two Uniform Linear Arrays (ULA) with 15 λ/2-equispaced sensors have been employed, using different spatial apertures in order to reduce sidelobe levels. Working frequencies have been designed on the basis of the main lobe width, the grating lobe levels and the frequency responses of people and sensors. For a case-study with 10 people, the acoustic profiles, formed by all images acquired, are evaluated and compared in a mean square error sense. Finally, system performance, using False Match Rate (FMR)/False Non-Match Rate (FNMR) parameters and the Receiver Operating Characteristic (ROC) curve, is evaluated. On the basis of the obtained results, this system could be used for biometric applications. PMID:22163708

  7. Two-dimensional acoustic metamaterial structure for potential image processing

    NASA Astrophysics Data System (ADS)

    Sun, Hongwei; Han, Yu; Li, Ying; Pai, Frank

    2015-12-01

    This paper presents modeling, analysis techniques and experiment of for two-Dimensional Acoustic metamaterial Structure for filtering acoustic waves. For a unit cell of an infinite two-Dimensional Acoustic metamaterial Structure, governing equations are derived using the extended Hamilton principle. The concepts of negative effective mass and stiffness and how the spring-mass-damper subsystems create a stopband are explained in detail. Numerical simulations reveal that the actual working mechanism of the proposed acoustic metamaterial structure is based on the concept of conventional mechanical vibration absorbers. It uses the incoming wave in the structure to resonate the integrated membrane-mass-damper absorbers to vibrate in their optical mode at frequencies close to but above their local resonance frequencies to create shear forces and bending moments to straighten the panel and stop the wave propagation. Moreover, a two-dimension acoustic metamaterial structure consisting of lumped mass and elastic membrane is fabricated in the lab. We do experiments on the model and The results validate the concept and show that, for two-dimension acoustic metamaterial structure do exist two vibration modes. For the wave absorption, the mass of each cell should be considered in the design. With appropriate design calculations, the proposed two-dimension acoustic metamaterial structure can be used for absorption of low-frequency waves. Hence this special structure can be used in filtering the waves, and the potential using can increase the ultrasonic imaging quality.

  8. Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects

    NASA Astrophysics Data System (ADS)

    Solodov, Igor; Döring, Daniel; Busse, Gerd

    2008-06-01

    Strongly nonlinear vibrations of near-surface fractured defects driven by an elastic wave radiate acoustic energy into adjacent air in a wide frequency range. The variations of pressure in the emitted airborne waves change the refractive index of air thus providing an acoustooptic interaction with a collimated laser beam. Such an air-coupled vibrometry (ACV) is proposed for detecting and imaging of acoustic radiation of nonlinear spectral components by cracked defects. The photoelastic relation in air is used to derive induced phase modulation of laser light in the heterodyne interferometer setup. The sensitivity of the scanning ACV to different spatial components of the acoustic radiation is analyzed. The animated airborne emission patterns are visualized for the higher harmonic and frequency mixing fields radiated by planar defects. The results confirm a high localization of the nonlinear acoustic emission around the defects and complicated directivity patterns appreciably different from those observed for fundamental frequencies.

  9. Acoustic angiography: a new imaging modality for assessing microvasculature architecture.

    PubMed

    Gessner, Ryan C; Frederick, C Brandon; Foster, F Stuart; Dayton, Paul A

    2013-01-01

    The purpose of this paper is to provide the biomedical imaging community with details of a new high resolution contrast imaging approach referred to as "acoustic angiography." Through the use of dual-frequency ultrasound transducer technology, images acquired with this approach possess both high resolution and a high contrast-to-tissue ratio, which enables the visualization of microvascular architecture without significant contribution from background tissues. Additionally, volumetric vessel-tissue integration can be visualized by using b-mode overlays acquired with the same probe. We present a brief technical overview of how the images are acquired, followed by several examples of images of both healthy and diseased tissue volumes. 3D images from alternate modalities often used in preclinical imaging, contrast-enhanced micro-CT and photoacoustics, are also included to provide a perspective on how acoustic angiography has qualitatively similar capabilities to these other techniques. These preliminary images provide visually compelling evidence to suggest that acoustic angiography may serve as a powerful new tool in preclinical and future clinical imaging. PMID:23997762

  10. Scanning tomographic acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Hua

    2002-11-01

    This paper provides an overview of the design and development of the scanning tomographic acoustic microscopy (STAM). This research effort spans over a period of more than 12 years, which successfully elevated the acoustic microscopy from the traditional intensity-mapping mode to the level of holographic and tomographic imaging. The tomographic imaging capability of STAM was developed on the platform of the scanning laser acoustic microscope (SLAM), which operates in a coherent transmission mode with plane-wave illumination and scanning laser wavefield detection. The image formation techniques were based on the backward propagation method implemented in the plane-to-plane format. In this paper, the key elements of the design and development, including the modification of the data-acquisition hardware, implementation of image reconstruction algorithms for multiple-frequency and multiple-angle tomography, and the high-precision phase-correction and image registration techniques for the superposition of coherent sub-images, will be discussed. Results of full-scale experiments will also be included to demonstrate the capability of holographic and tomographic image formation in microscopic scale.

  11. Optimal flushing agents for integrated optical and acoustic imaging systems

    PubMed Central

    Li, Jiawen; Minami, Hataka; Steward, Earl; Ma, Teng; Mohar, Dilbahar; Robertson, Claire; Shung, Kirk; Zhou, Qifa; Patel, Pranav; Chen, Zhongping

    2015-01-01

    Abstract. An increasing number of integrated optical and acoustic intravascular imaging systems have been developed and hold great promise for accurately diagnosing vulnerable plaques and guiding atherosclerosis treatment. However, in any intravascular environment, the vascular lumen is filled with blood, a high-scattering source for optical and high-frequency ultrasound signals. Blood must be flushed away to provide clearer images. To our knowledge, no research has been performed to find the ideal flushing agent for combined optical and acoustic imaging techniques. We selected three solutions as potential flushing agents for their image-enhancing effects: mannitol, dextran, and iohexol. Testing of these flushing agents was performed in a closed-loop circulation model and in vivo on rabbits. We found that a high concentration of dextran was the most useful for simultaneous intravascular ultrasound and optical coherence tomography imaging. PMID:25985096

  12. Optimal flushing agents for integrated optical and acoustic imaging systems.

    PubMed

    Li, Jiawen; Minami, Hataka; Steward, Earl; Ma, Teng; Mohar, Dilbahar; Robertson, Claire; Shung, Kirk; Zhou, Qifa; Patel, Pranav; Chen, Zhongping

    2015-05-01

    An increasing number of integrated optical and acoustic intravascular imaging systems have been developed and hold great promise for accurately diagnosing vulnerable plaques and guiding atherosclerosis treatment. However, in any intravascular environment, the vascular lumen is filled with blood, a high-scattering source for optical and high-frequency ultrasound signals. Blood must be flushed away to provide clearer images. To our knowledge, no research has been performed to find the ideal flushing agent for combined optical and acoustic imaging techniques. We selected three solutions as potential flushing agents for their image-enhancing effects: mannitol, dextran, and iohexol. Testing of these flushing agents was performed in a closed-loop circulation model and in vivo on rabbits. We found that a high concentration of dextran was the most useful for simultaneous intravascular ultrasound and optical coherence tomography imaging. PMID:25985096

  13. Optimal flushing agents for integrated optical and acoustic imaging systems

    NASA Astrophysics Data System (ADS)

    Li, Jiawen; Minami, Hataka; Steward, Earl; Ma, Teng; Mohar, Dilbahar; Robertson, Claire; Shung, Kirk; Zhou, Qifa; Patel, Pranav; Chen, Zhongping

    2015-05-01

    An increasing number of integrated optical and acoustic intravascular imaging systems have been developed and hold great promise for accurately diagnosing vulnerable plaques and guiding atherosclerosis treatment. However, in any intravascular environment, the vascular lumen is filled with blood, a high-scattering source for optical and high-frequency ultrasound signals. Blood must be flushed away to provide clearer images. To our knowledge, no research has been performed to find the ideal flushing agent for combined optical and acoustic imaging techniques. We selected three solutions as potential flushing agents for their image-enhancing effects: mannitol, dextran, and iohexol. Testing of these flushing agents was performed in a closed-loop circulation model and in vivo on rabbits. We found that a high concentration of dextran was the most useful for simultaneous intravascular ultrasound and optical coherence tomography imaging.

  14. Epipolar geometry of opti-acoustic stereo imaging.

    PubMed

    Negahdaripour, Shahriar

    2007-10-01

    Optical and acoustic cameras are suitable imaging systems to inspect underwater structures, both in regular maintenance and security operations. Despite high resolution, optical systems have limited visibility range when deployed in turbid waters. In contrast, the new generation of high-frequency (MHz) acoustic cameras can provide images with enhanced target details in highly turbid waters, though their range is reduced by one to two orders of magnitude compared to traditional low-/midfrequency (10s-100s KHz) sonar systems. It is conceivable that an effective inspection strategy is the deployment of both optical and acoustic cameras on a submersible platform, to enable target imaging in a range of turbidity conditions. Under this scenario and where visibility allows, registration of the images from both cameras arranged in binocular stereo configuration provides valuable scene information that cannot be readily recovered from each sensor alone. We explore and derive the constraint equations for the epipolar geometry and stereo triangulation in utilizing these two sensing modalities with different projection models. Theoretical results supported by computer simulations show that an opti-acoustic stereo imaging system outperforms a traditional binocular vision with optical cameras, particularly for increasing target distance and (or) turbidity. PMID:17699922

  15. Application of acoustic reflection tomography to sonar imaging.

    PubMed

    Ferguson, Brian G; Wyber, Ron J

    2005-05-01

    Computer-aided tomography is a technique for providing a two-dimensional cross-sectional view of a three-dimensional object through the digital processing of many one-dimensional views (or projections) taken at different look directions. In acoustic reflection tomography, insonifying the object and then recording the backscattered signal provides the projection information for a given look direction (or aspect angle). Processing the projection information for all possible aspect angles enables an image to be reconstructed that represents the two-dimensional spatial distribution of the object's acoustic reflectivity function when projected on the imaging plane. The shape of an idealized object, which is an elliptical cylinder, is reconstructed by applying standard backprojection, Radon transform inversion (using both convolution and filtered backprojections), and direct Fourier inversion to simulated projection data. The relative merits of the various reconstruction algorithms are assessed and the resulting shape estimates compared. For bandpass sonar data, however, the wave number components of the acoustic reflectivity function that are outside the passband are absent. This leads to the consideration of image reconstruction for bandpass data. Tomographic image reconstruction is applied to real data collected with an ultra-wideband sonar transducer to form high-resolution acoustic images of various underwater objects when the sonar and object are widely separated. PMID:15957762

  16. Ideal flushing agents for integrated optical acoustic imaging systems

    NASA Astrophysics Data System (ADS)

    Li, Jiawen; Minami, Hataka; Steward, Earl; Ma, Teng; Mohar, Dilbahar; Robertson, Claire; Shung, K. Kirk; Zhou, Qifa; Patel, Pranav M.; Chen, Zhongping

    2015-02-01

    An increased number of integrated optical acoustic intravascular imaging systems have been researched and hold great hope for accurate diagnosing of vulnerable plaques and for guiding atherosclerosis treatment. However, in any intravascular environment, vascular lumen is filled with blood, which is a high-scattering source for optical and high frequency ultrasound signals. Blood must be flushed away to make images clear. To our knowledge, no research has been performed to find the ideal flushing agent that works for both optical and acoustic imaging techniques. We selected three solutions, mannitol, dextran and iohexol, as flushing agents because of their image-enhancing effects and low toxicities. Quantitative testing of these flushing agents was performed in a closed loop circulation model and in vivo on rabbits.

  17. Wavefield Compression for Full-Waveform Inversion

    NASA Astrophysics Data System (ADS)

    Boehm, Christian; Fichtner, Andreas; de la Puente, Josep; Hanzich, Mauricio

    2015-04-01

    We present compression techniques tailored to iterative nonlinear minimization methods that significantly reduce the memory requirements to store the forward wavefield for the computation of sensitivity kernels. Full-waveform inversion on 3d data sets requires massive computing and memory capabilities. Adjoint techniques offer a powerful tool to compute the first and second derivatives. However, due to the asynchronous nature of forward and adjoint simulations, a severe bottleneck is introduced by the necessity to access both wavefields simultaneously when computing sensitivity kernels. There exist two opposing strategies to deal with this challenge. On the one hand, conventional approaches save the whole forward wavefield to the disk, which yields a significant I/O overhead and might require several terabytes of storage capacity per seismic event. On the other hand, checkpointing techniques allow to trade an almost arbitrary amount of memory requirements for a - potentially large - number of additional forward simulations. We propose an alternative approach that strikes a balance between memory requirements and the need for additional computations. Here, we aim at compressing the forward wavefield in such a way that (1) the I/O overhead is reduced substantially without the need for additional simulations, (2) the costs for compressing/decompressing the wavefield are negligible, and (3) the approximate derivatives resulting from the compressed forward wavefield do not affect the rate of convergence of a Newton-type minimization method. To this end, we apply an adaptive re-quantization of the displacement field that uses dynamically adjusted floating-point accuracies - i.e., a locally varying number of bits - to store the data. Furthermore, the spectral element functions are adaptively downsampled to a lower polynomial degree. In addition, a sliding-window cubic spline re-interpolates the temporal snapshots to recover a smooth signal. Moreover, a preprocessing step

  18. Visualization of elastic wavefields computed with a finite difference code

    SciTech Connect

    Larsen, S.; Harris, D.

    1994-11-15

    The authors have developed a finite difference elastic propagation model to simulate seismic wave propagation through geophysically complex regions. To facilitate debugging and to assist seismologists in interpreting the seismograms generated by the code, they have developed an X Windows interface that permits viewing of successive temporal snapshots of the (2D) wavefield as they are calculated. The authors present a brief video displaying the generation of seismic waves by an explosive source on a continent, which propagate to the edge of the continent then convert to two types of acoustic waves. This sample calculation was part of an effort to study the potential of offshore hydroacoustic systems to monitor seismic events occurring onshore.

  19. Opto-acoustic breast imaging with co-registered ultrasound

    NASA Astrophysics Data System (ADS)

    Zalev, Jason; Clingman, Bryan; Herzog, Don; Miller, Tom; Stavros, A. Thomas; Oraevsky, Alexander; Kist, Kenneth; Dornbluth, N. Carol; Otto, Pamela

    2014-03-01

    We present results from a recent study involving the ImagioTM breast imaging system, which produces fused real-time two-dimensional color-coded opto-acoustic (OA) images that are co-registered and temporally inter- leaved with real-time gray scale ultrasound using a specialized duplex handheld probe. The use of dual optical wavelengths provides functional blood map images of breast tissue and tumors displayed with high contrast based on total hemoglobin and oxygen saturation of the blood. This provides functional diagnostic information pertaining to tumor metabolism. OA also shows morphologic information about tumor neo-vascularity that is complementary to the morphological information obtained with conventional gray scale ultrasound. This fusion technology conveniently enables real-time analysis of the functional opto-acoustic features of lesions detected by readers familiar with anatomical gray scale ultrasound. We demonstrate co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical study that provide new insight into the function of tumors in-vivo. Results from the Feasibility Study show preliminary evidence that the technology may have the capability to improve characterization of benign and malignant breast masses over conventional diagnostic breast ultrasound alone and to improve overall accuracy of breast mass diagnosis. In particular, OA improved speci city over that of conventional diagnostic ultrasound, which could potentially reduce the number of negative biopsies performed without missing cancers.

  20. Acoustic and photoacoustic microscopy imaging of single leukocytes

    NASA Astrophysics Data System (ADS)

    Strohm, Eric M.; Moore, Michael J.; Kolios, Michael C.

    2016-03-01

    An acoustic/photoacoustic microscope was used to create micrometer resolution images of stained cells from a blood smear. Pulse echo ultrasound images were made using a 1000 MHz transducer with 1 μm resolution. Photoacoustic images were made using a fiber coupled 532 nm laser, where energy losses through stimulated Raman scattering enabled output wavelengths from 532 nm to 620 nm. The laser was focused onto the sample using a 20x objective, and the laser spot co-aligned with the 1000 MHz transducer opposite the laser. The blood smear was stained with Wright-Giemsa, a common metachromatic dye that differentially stains the cellular components for visual identification. A neutrophil, lymphocyte and a monocyte were imaged using acoustic and photoacoustic microscopy at two different wavelengths, 532 nm and 600 nm. Unique features in each imaging modality enabled identification of the different cell types. This imaging method provides a new way of imaging stained leukocytes, with applications towards identifying and differentiating cell types, and detecting disease at the single cell level.

  1. Ultra high frequency imaging acoustic microscope

    DOEpatents

    Deason, Vance A.; Telschow, Kenneth L.

    2006-05-23

    An imaging system includes: an object wavefront source and an optical microscope objective all positioned to direct an object wavefront onto an area of a vibrating subject surface encompassed by a field of view of the microscope objective, and to direct a modulated object wavefront reflected from the encompassed surface area through a photorefractive material; and a reference wavefront source and at least one phase modulator all positioned to direct a reference wavefront through the phase modulator and to direct a modulated reference wavefront from the phase modulator through the photorefractive material to interfere with the modulated object wavefront. The photorefractive material has a composition and a position such that interference of the modulated object wavefront and modulated reference wavefront occurs within the photorefractive material, providing a full-field, real-time image signal of the encompassed surface area.

  2. Delamination detection in foam core composite structures using transient flexural wavefields

    NASA Astrophysics Data System (ADS)

    Lamboul, B.; Osmont, D.

    2016-03-01

    This paper investigates a health monitoring technique for foam sandwich structures based on flexural wavefields imaged by Laser Doppler vibrometry. A study of calibrated artificial defect responses in harmonic regime demonstrates that the use of a low frequency regime (below 30 kHz) makes it possible to excite defects in their first flexural resonance modes. The analysis performed in harmonic regime is used to interpret signature patterns obtained with accumulated energy maps from transient wavefield recordings. The potential of the technique is demonstrated on a real impact-induced defect. The robustness of the method relatively to the excitation center frequency selection and to the presence of wave reverberation is demonstrated.

  3. Frequency-wavenumber domain analysis of guided wavefields.

    PubMed

    Michaels, Thomas E; Michaels, Jennifer E; Ruzzene, Massimo

    2011-05-01

    Full wavefield measurements obtained with either an air-coupled transducer mounted on a scanning stage or a scanning laser vibrometer can be combined with effective signal and imaging processing algorithms to support characterization of guided waves as well as detection, localization and quantification of structural damage. These wavefield images contain a wealth of information that clearly shows details of guided waves as they propagate outward from the source, reflect from specimen boundaries, and scatter from discontinuities within the structure. The analysis of weaker scattered waves is facilitated by the removal of source waves and the separation of wave modes, which is effectively achieved via frequency-wavenumber domain filtering in conjunction with the subsequent analysis of the resulting residual signals. Incident wave removal highlights the presence and the location of weak scatterers, while the separation of individual guided wave modes allows the characterization of their separate contribution to the scattered field and the evaluation of mode conversion phenomena. The effectiveness of these methods is demonstrated through their application to detection of a delamination in a composite plate and detection of a crack emanating from a hole. PMID:21190706

  4. Vector Acoustics, Vector Sensors, and 3D Underwater Imaging

    NASA Astrophysics Data System (ADS)

    Lindwall, D.

    2007-12-01

    Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

  5. a Three-Dimensional Acoustical Imaging System for Zooplankton Observations

    NASA Astrophysics Data System (ADS)

    McGehee, Duncan Ewell

    This dissertation describes the design, testing, and use of a three-dimensional acoustical imaging system, called Fish TV, or FTV, for tracking zooplankton swimming in situ. There is an increasing recognition that three -dimensional tracks of individual plankters are needed for some studies in behavioral ecology including, for example, the role of individual behavior in patch formation and maintenance. Fish TV was developed in part to provide a means of examining zooplankton swimming behavior in a non-invasive way. The system works by forming a set of 64 acoustic beams in an 8 by 8 pattern, each beam 2 ^circ by 2^circ , for a total coverage of 16^circ by 16^circ. The 8 by 8 beams form two dimensions of the image; range provides the third dimension. The system described in the thesis produces three-dimensional images at the rate of approximately one per second. A set of laboratory and field experiments is described that demonstrates the capabilities of the system. The final field experiment was the in situ observation of zooplankton swimming behavior at a site in the San Diego Trough, 15 nautical miles southwest of San Diego. 314 plankters were tracked for one minute. It was observed that there was no connection between the acoustic size of the animals and their repertoire of swimming behaviors. Other contributions of the dissertation include the development of two novel methods for generating acoustic beams with low side lobes. The first is the method of dense random arrays. The second is the optimum mean square quantized aperture method. Both methods were developed originally as ways to "build a better beam pattern" for Fish TV, but also have general significance with respect to aperture theory.

  6. 1-D seismic inversion of dual wavefield data. Part 2: A Gulf of Mexico example

    SciTech Connect

    Hildebrand, S.T. ); McMechan, G.A. . Center for Lithospheric Studies)

    1994-05-01

    Stable estimates for angle-dependent acoustic impedance are obtained from a dual wavefield data set that consists of pressure and vertical particle velocity measurements. Using these acoustic impedance estimates, a nonlocal inversion procedure predicts sediment material impedance, interval velocity, density, and their associated relative errors as a function of depth. The method is successfully applied to data from a marine seismic experiment conducted by Halliburton Geophysical Services in the Gulf of Mexico in 1989. The inverted values for the seafloor sediment density and interval velocity lie close to those obtained independently by other methods, implying that the inversion illustrated is valid for use with field data.

  7. Guided wavefield reconstruction from sparse measurements

    NASA Astrophysics Data System (ADS)

    Mesnil, Olivier; Ruzzene, Massimo

    2016-02-01

    Guided wave measurements are at the basis of several Non-Destructive Evaluation (NDE) techniques. Although sparse measurements of guided wave obtained using piezoelectric sensors can efficiently detect and locate defects, extensive informa-tion on the shape and subsurface location of defects can be extracted from full-field measurements acquired by Laser Doppler Vibrometers (LDV). Wavefield acquisition from LDVs is generally a slow operation due to the fact that the wave propagation to record must be repeated for each point measurement and the initial conditions must be reached between each measurement. In this research, a Sparse Wavefield Reconstruction (SWR) process using Compressed Sensing is developed. The goal of this technique is to reduce the number of point measurements needed to apply NDE techniques by at least one order of magnitude by extrapolating the knowledge of a few randomly chosen measured pixels over an over-sampled grid. To achieve this, the Lamb wave propagation equation is used to formulate a basis of shape functions in which the wavefield has a sparse representation, in order to comply with the Compressed Sensing requirements and use l1-minimization solvers. The main assumption of this reconstruction process is that every material point of the studied area is a potential source. The Compressed Sensing matrix is defined as being the contribution that would have been received at a measurement location from each possible source, using the dispersion relations of the specimen computed using a Semi-Analytical Finite Element technique. The measurements are then processed through an l1-minimizer to find a minimum corresponding to the set of active sources and their corresponding excitation functions. This minimum represents the best combination of the parameters of the model matching the sparse measurements. Wavefields are then reconstructed using the propagation equation. The set of active sources found by minimization contains all the wave

  8. Airframe noise measurements by acoustic imaging

    NASA Technical Reports Server (NTRS)

    Kendall, J. M.

    1977-01-01

    Studies of the noise produced by flow past wind tunnel models are presented. The central objective of these is to find the specific locations within a flow which are noisy, and to identify the fluid dynamic processes responsible, with the expectation that noise reduction principles will be discovered. The models tested are mostly simple shapes which result in types of flow that are similar to those occurring on, for example, aircraft landing gear and wheel cavities. A model landing gear and a flap were also tested. Turbulence has been intentionally induced as appropriate in order to simulate full-scale effects more closely. The principal technique involves use of a highly directional microphone system which is scanned about the flow field to be analyzed. The data so acquired are presented as a pictorial image of the noise source distribution. An important finding is that the noise production is highly variable within a flow field and that sources can be attributed to various fluid dynamic features of the flow. Flow separation was not noisy, but separation closure usually was.

  9. Application of time reversal acoustics focusing for nonlinear imaging ms

    NASA Astrophysics Data System (ADS)

    Sarvazyan, Armen; Sutin, Alexander

    2001-05-01

    Time reversal acoustic (TRA) focusing of ultrasound appears to be an effective tool for nonlinear imaging in industrial and medical applications because of its ability to efficiently concentrate ultrasonic energy (close to diffraction limit) in heterogeneous media. In this study, we used two TRA systems to focus ultrasonic beams with different frequencies in coinciding focal points, thus causing the generation of ultrasonic waves with combination frequencies. Measurements of the intensity of these combination frequency waves provide information on the nonlinear parameter of medium in the focal region. Synchronized stirring of two TRA focused beams enables obtaining 3-D acoustic nonlinearity images of the object. Each of the TRA systems employed an aluminum resonator with piezotransducers glued to its facet. One of the free facets of each resonator was submerged into a water tank and served as a virtual phased array capable of ultrasound focusing and beam steering. To mimic a medium with spatially varying acoustical nonlinearity a simplest model such as a microbubble column in water was used. Microbubbles were generated by electrolysis of water using a needle electrode. An order of magnitude increase of the sum frequency component was observed when the ultrasound beams were focused in the area with bubbles.

  10. Unsupervised pattern recognition in continuous seismic wavefield records using Self-Organizing Maps

    NASA Astrophysics Data System (ADS)

    Köhler, Andreas; Ohrnberger, Matthias; Scherbaum, Frank

    2010-09-01

    Modern acquisition of seismic data on receiver networks worldwide produces an increasing amount of continuous wavefield recordings. In addition to manual data inspection, seismogram interpretation requires therefore new processing utilities for event detection, signal classification and data visualization. The use of machine learning techniques automatises decision processes and reveals the statistical properties of data. This approach is becoming more and more important and valuable for large and complex seismic records. Unsupervised learning allows the recognition of wavefield patterns, such as short-term transients and long-term variations, with a minimum of domain knowledge. This study applies an unsupervised pattern recognition approach for the discovery, imaging and interpretation of temporal patterns in seismic array recordings. For this purpose, the data is parameterized by feature vectors, which combine different real-valued wavefield attributes for short time windows. Standard seismic analysis tools are used as feature generation methods, such as frequency-wavenumber, polarization and spectral analysis. We use Self-Organizing Maps (SOMs) for a data-driven feature selection, visualization and clustering procedure. The application to continuous recordings of seismic signals from an active volcano (Mount Merapi, Java, Indonesia) shows that volcano-tectonic and rockfall events can be detected and distinguished by clustering the feature vectors. Similar results are obtained in terms of correctly classifying events compared to a previously implemented supervised classification system. Furthermore, patterns in the background wavefield, that is the 24-hr cycle due to human activity, are intuitively visualized by means of the SOM representation. Finally, we apply our technique to an ambient seismic vibration record, which has been acquired for local site characterization. Disturbing wavefield patterns are identified which affect the quality of Love wave dispersion

  11. Wavefield properties of a shallow long-period event and tremor at Kilauea Volcano, Hawaii

    USGS Publications Warehouse

    Saccorotti, G.; Chouet, B.; Dawson, P.

    2001-01-01

    The wavefields of tremor and a long-period (LP) event associated with the ongoing eruptive activity at Kilauea Volcano, Hawaii, are investigated using a combination of dense small-aperture (300 m) and sparse large-aperture (5 km) arrays deployed in the vicinity of the summit caldera. Measurements of azimuth and slowness for tremor recorded on the small-aperture array indicate a bimodal nature of the observed wavefield. At frequencies below 2 Hz, the wavefield is dominated by body waves impinging the array with steep incidence. These arrivals are attributed to the oceanic microseismic noise. In the 2-6 Hz band, the wavefield is dominated by waves propagating from sources located at shallow depths (<1 km) beneath the eastern edge of the Halemaumau pit crater. The hypocenter of the LP event, determined from frequency-slowness analyses combined with phase picks, appears to be located close to the source of tremor but at a shallower depth (<0.1 km). The wavefields of tremor and LP event are characterized by a complex composition of body and surface waves, whose propagation and polarization properties are strongly affected by topographic and structural features in the summit caldera region. Analyses of the directional properties of the wavefield in the 2-6 Hz band point to the directions of main scattering sources, which are consistent with pronounced velocity contrasts imaged in a high-resolution three-dimensional velocity model of the caldera region. The frequency and Q of the dominant peak observed in the spectra of the LP event may be explained as the dominant oscillation mode of a crack with scale length 20-100 m and aperture of a few centimeters filled with bubbly water. The mechanism driving the shallow tremor appears to be consistent with a sustained excitation originating in the oscillations of a bubbly cloud resulting from vesiculation and degassing in the magma. ?? 2001 Elsevier Science B.V. All rights reserved.

  12. Identifying Vulnerable Plaques with Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Joshua Ryan

    The rupture of arterial plaques is the most common cause of ischemic complications including stroke, the fourth leading cause of death and number one cause of long term disability in the United States. Unfortunately, because conventional diagnostic tools fail to identify plaques that confer the highest risk, often a disabling stroke and/or sudden death is the first sign of disease. A diagnostic method capable of characterizing plaque vulnerability would likely enhance the predictive ability and ultimately the treatment of stroke before the onset of clinical events. This dissertation evaluates the hypothesis that Acoustic Radiation Force Impulse (ARFI) imaging can noninvasively identify lipid regions, that have been shown to increase a plaque's propensity to rupture, within carotid artery plaques in vivo. The work detailed herein describes development efforts and results from simulations and experiments that were performed to evaluate this hypothesis. To first demonstrate feasibility and evaluate potential safety concerns, finite- element method simulations are used to model the response of carotid artery plaques to an acoustic radiation force excitation. Lipid pool visualization is shown to vary as a function of lipid pool geometry and stiffness. A comparison of the resulting Von Mises stresses indicates that stresses induced by an ARFI excitation are three orders of magnitude lower than those induced by blood pressure. This thesis also presents the development of a novel pulse inversion harmonic tracking method to reduce clutter-imposed errors in ultrasound-based tissue displacement estimates. This method is validated in phantoms and was found to reduce bias and jitter displacement errors for a marked improvement in image quality in vivo. Lastly, this dissertation presents results from a preliminary in vivo study that compares ARFI imaging derived plaque stiffness with spatially registered composition determined by a Magnetic Resonance Imaging (MRI) gold standard

  13. Micro-nondestructive evaluation of microelectronics using three-dimensional acoustic imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Guang-Ming; Harvey, David M.; Burton, David R.

    2011-02-01

    Holographic-like three-dimensional (3D) acoustic imaging is developed for micro-nondestructive evaluation of microelectronics. It is implemented by stacking all the interface slices together to locate and identify hidden defects. Matching pursuit based acoustic time-frequency domain imaging is proposed to overcome the wavelength limit of axial resolution so that ultra-thin slices are generated. Experiments are performed on 3D acoustic data collected from microelectronic packages. Results show that the proposed technique resolves closely spaced features that are unavailable by conventional acoustic imaging, revealing more image details of defects.

  14. A Dual Communication and Imaging Underwater Acoustic System

    NASA Astrophysics Data System (ADS)

    Fu, Tricia C.

    A dual communication and imaging underwater acoustic system is proposed and developed throughout this dissertation. Due to the wide variation in underwater channel characteristics, the research here focuses more on robustness to multipath in the shallow underwater acoustic environment, rather than high bit-rate applications and signaling schemes. Lower bit-rate (in the hundreds of bits per second (bps) to low kbps), applications such as the transfer of ecological telemetry data, e.g. conductivity or temperature data, are the primary focus of this dissertation. The parallels between direct sequence spread spectrum in digital communication and pulse-echo with pulse compression in imaging, and channel estimation in communication and range profile estimation in imaging are drawn, leading to a unified communications and imaging platform. A digital communication algorithm for channel order and channel coefficient estimation and symbol demodulation using Matching Pursuit (MP) with Generalized Multiple Hypothesis Testing (GMHT) is implemented in programmable DSP in real time with field experiment results in varying underwater environments for the single receiver (Rx), single transmitter (Tx) case. The custom and off-the-shelf hardware used in the single receiver, single transmitter set of experiments are detailed as well. This work is then extended to the single-input multiple-output (SIMO) case, and then to the full multiple-input multiple-output (MIMO) case. The results of channel estimation are used for simple range profile imaging reconstructions. Successful simulated and experimental results for both transducer array configurations are presented and analyzed. Non-real-time symbol demodulation and channel estimation is performed using experimental data from a scaled testing environment. New hardware based on cost-effective fish-finder transducers for a 6 Rx--1 Tx and 6 Rx--4 Tx transducer array is detailed. Lastly, in an application that is neither communication nor

  15. Acoustic Radiation Force Impulse (ARFI) Imaging-Based Needle Visualization

    PubMed Central

    Rotemberg, Veronica; Palmeri, Mark; Rosenzweig, Stephen; Grant, Stuart; Macleod, David; Nightingale, Kathryn

    2011-01-01

    Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARFI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18, 21 and 25 gauge needles between 0–4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10° and 35° from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm off set in elevation from the transducer imaging plane and on-axis angled needles between 10°–35° above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications. PMID:21608445

  16. Feasibility of High Frequency Acoustic Imaging for Inspection of Containments

    SciTech Connect

    C.N. Corrado; J.E. Bondaryk; V. Godino

    1998-08-01

    The Nuclear Regulatory Commission has a program at the Oak Ridge National Laboratory to provide assistance in their assessment of the effects of potential degradation on the structural integrity and Ieaktightness of metal containment vessels and steel liners of concrete containment in nuclear power plants. One of the program objectives is to identify a technique(s) for inspection of inaccessible portions of the containment pressure boundary. Acoustic imaging has been identified as one of these potential techniques. A numerical feasibility study investigated the use of high-frequency bistatic acoustic imaging techniques for inspection of inaccessible portions of the metallic pressure boundary of nuclear power plant containment. The range-dependent version of the OASES Code developed at the Massachusetts Institute of Technology was utilized to perform a series of numerical simulations. OASES is a well developed and extensively tested code for evaluation of the acoustic field in a system of stratified fluid and/or elastic layers. Using the code, an arbitrary number of fluid or solid elastic layers are interleaved, with the outer layers modeled as halfspaces. High frequency vibrational sources were modeled to simulate elastic waves in the steel. The received field due to an arbitrary source array can be calculated at arbitrary depth and range positions. In this numerical study, waves that reflect and scatter from surface roughness caused by modeled degradations (e.g., corrosion) are detected and used to identify and map the steel degradation. Variables in the numerical study included frequency, flaw size, interrogation distance, and sensor incident angle.Based on these analytical simulations, it is considered unlikely that acoustic imaging technology can be used to investigate embedded steel liners of reinforced concrete containment. The thin steel liner and high signal losses to the concrete make this application difficult. Results for portions of steel containment

  17. Multi-crack imaging using nonclassical nonlinear acoustic method

    NASA Astrophysics Data System (ADS)

    Zhang, Lue; Zhang, Ying; Liu, Xiao-Zhou; Gong, Xiu-Fen

    2014-10-01

    Solid materials with cracks exhibit the nonclassical nonlinear acoustical behavior. The micro-defects in solid materials can be detected by nonlinear elastic wave spectroscopy (NEWS) method with a time-reversal (TR) mirror. While defects lie in viscoelastic solid material with different distances from one another, the nonlinear and hysteretic stress—strain relation is established with Preisach—Mayergoyz (PM) model in crack zone. Pulse inversion (PI) and TR methods are used in numerical simulation and defect locations can be determined from images obtained by the maximum value. Since false-positive defects might appear and degrade the imaging when the defects are located quite closely, the maximum value imaging with a time window is introduced to analyze how defects affect each other and how the fake one occurs. Furthermore, NEWS-TR-NEWS method is put forward to improve NEWS-TR scheme, with another forward propagation (NEWS) added to the existing phases (NEWS and TR). In the added phase, scanner locations are determined by locations of all defects imaged in previous phases, so that whether an imaged defect is real can be deduced. NEWS-TR-NEWS method is proved to be effective to distinguish real defects from the false-positive ones. Moreover, it is also helpful to detect the crack that is weaker than others during imaging procedure.

  18. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, W. D.; Brennan, Kevin F.

    1994-01-01

    The primary goal of this research is to develop a solid-state high definition television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels per frame. This imager offers an order of magnitude improvement in speed over CCD designs and will allow for monolithic imagers operating from the IR to the UV. The technical approach of the project focuses on the development of the three basic components of the imager and their integration. The imager chip can be divided into three distinct components: (1) image capture via an array of avalanche photodiodes (APD's), (2) charge collection, storage and overflow control via a charge transfer transistor device (CTD), and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the development of manufacturable designs for each of these component devices. In addition to the development of each of the three distinct components, work towards their integration is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail in Sections 2-4.

  19. Object detection and imaging with acoustic time reversal mirrors

    NASA Astrophysics Data System (ADS)

    Fink, Mathias

    1993-11-01

    Focusing an acoustic wave on an object of unknown shape through an inhomogeneous medium of any geometrical shape is a challenge in underground detection. Optimal detection and imaging of objects needs the development of such focusing techniques. The use of a time reversal mirror (TRM) represents an original solution to this problem. It realizes in real time a focusing process matched to the object shape, to the geometries of the acoustic interfaces and to the geometries of the mirror. It is a self adaptative technique which compensates for any geometrical distortions of the mirror structure as well as for diffraction and refraction effects through the interfaces. Two real time 64 and 128 channel prototypes have been built in our laboratory and TRM experiments demonstrating the TRM performance through inhomogeneous solid and liquid media are presented. Applications to medical therapy (kidney stone detection and destruction) and to nondestructive testing of metallurgical samples of different geometries are described. Extension of this study to underground detection and imaging will be discussed.

  20. Efficient strategies and imaging conditions for elastic prestack reverse-time migration of reflection seismic data

    NASA Astrophysics Data System (ADS)

    Nguyen, Bao D.

    Imaging with prestack reverse-time migration (RTM) is typically approached via a zero-lag crosscorrelation between source and receiver wavefields, which imposes unnecessarily stringent requirements for computational resources and disk storage. The imaging principle for reflectivity is analyzed and we demonstrate that a single maximal energy arrival event is often sufficient for migration imaging. Methods to alleviate the cost of crosscorrelation imaging are proposed and categorized into reconstructive and non-reconstructive schemes. Source wavefield reconstruction treats the source extrapolation as a method of providing the auxiliary conditions for an initial-boundary value problem. A first-pass (forward-time) extrapolation for the source wavefield identifies the boundary and/or initial values necessary to uniquely reconstruct it using a second (reverse-time) backward propagation. Mixed value, or hybrid, reconstruction is proposed as the most accurate alternative to storing the source wavefield time history. Reconstructing the source wavefield reduces storage costs by up to two orders of magnitude without an appreciable loss of image quality. Boundary value and initial value reconstruction methods are extended from acoustic to elastic RTM. Non-reconstructive approaches deviate from the conventional imaging paradigm, as only the most salient information required for imaging is kept. A maximal energy arrival event (termed the `excitation amplitude') imaging condition is explored as the direct analog for the theoretical reflection coefficient for acoustic isotropic media, and extended for elastic RTM. Sparse crosscorrelation is proposed as an equivalent method to standard crosscorrelation where the migrated image is now represented with a minimized data set. Time-binning is dynamic sorting algorithm with linear time complexity proposed for use with both excitation amplitude and sparse crosscorrelation approches to further expedite imaging. These parsimonious imaging

  1. Scanning tomographic acoustic microscopy: principles and recent developments (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Wade, G.; Meyyappan, A.

    1987-09-01

    Acoustic Microscopy is an important branch of non-destructive evaluation which provides high resolution for imaging the detailed structure of a small object. When an acoustic microscope operates in the transmission mode, the micrograph is simply a shadowgraph of all the structures encountered by the acoustic wave passing through the object. Because of diffraction and overlapping, the resultant images are difficult to comprehend in the case of specimens of substantial thickness and structural complexity. We used the principles of diffraction tomography and acoustical holography along with digital calcuations of wavefield propagation to overcome this problem. We have described in previously-published work how a scanning laser acoustic microscope (SLAM) can be modified to obtain data for subsurface tomographic imaging. In this paper, we review the principles of scanning tomographic acoustic microscopy (STAM). The required modification of SLAM to obtain STAM and the reconstruction process are described. We show how we are able to accurately acquire the complex-amplitude information necessary for image reconstruction. We demonstrate the power of this technique by comparing digitally-computed images thus obtained with analogue images of a conventional SLAM. The results show that high-quality, high-resolution subsurface images can be obtained from experimentally acquired data. We also describe techniques to obtain projection data from different angles of wave incidence enabling us to tomographically reconstruct different planes of a complex specimen in microscopic detail. With these modifications in place, STAM should shortly become a powerful tool in non-destructive evaluation.

  2. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, W. D.; Brennan, K. F.; Summers, C. J.

    1994-01-01

    The primary goal of this research is to develop a solid-state television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels/frame. This imager will offer an order of magnitude improvements in speed over CCD designs and will allow for monolithic imagers operating from the IR to UV. The technical approach of the project focuses on the development of the three basic components of the imager and their subsequent integration. The camera chip can be divided into three distinct functions: (1) image capture via an array of avalanche photodiodes (APD's); (2) charge collection, storage, and overflow control via a charge transfer transistor device (CTD); and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the optimization of each of these component devices. In addition to the development of each of the three distinct components, work towards their integration and manufacturability is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail.

  3. An analytical solution to separate P-waves and S-waves in the VSP wavefield

    SciTech Connect

    Amano, Hiroshi

    1994-12-31

    An analytical solution to separate P-waves and S-waves in the VSP wavefield is derived with combinations of the formal solution of a forward VSP modeling. Some practical applications of this method to synthetic seismograms and field data are investigated and evaluated. Little wave distortion is recognized and the weak wavefield masked by dominant wave trains can be extracted with this method. The decomposed wavefield is expressed in frequency-depth (f-z) domain as a linear combination of up to the third order differential of traces, which is approximated by trace difference sin the practical separation process. In general, five traces with single-component data are required in this process, but the same process is implemented with only three traces in the acoustic case. Two-trace extrapolation is applied to each edge of data gather in order to enhance the accuracy of trace difference. Since the formulas are developed in f-z domain, the influence of anelasticity is taken into account with simplicity and the calculation is carried out fast enough with the benefit of fast Fourier transform (FFT).

  4. Acoustical imaging of spheres above a reflecting surface

    NASA Astrophysics Data System (ADS)

    Chambers, David; Berryman, James

    2003-04-01

    An analytical study using the MUSIC method of subspace imaging is presented for the case of spheres above a reflecting boundary. The field scattered from the spheres and the reflecting boundary is calculated analytically, neglecting interactions between spheres. The singular value decomposition of the response matrix is calculated and the singular vectors divided into signal and noise subspaces. Images showing the estimated sphere locations are obtained by backpropagating the noise vectors using either the free space Green's function or the Green's function that incorporates reflections from the boundary. We show that the latter Green's function improves imaging performance after applying a normalization that compensates for the interference between direct and reflected fields. We also show that the best images are attained in some cases when the number of singular vectors in the signal subspace exceeds the number of spheres. This is consistent with previous analysis showing multiple eigenvalues of the time reversal operator for spherical scatterers [Chambers and Gautesen, J. Acoust. Soc. Am. 109 (2001)]. [Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  5. Implementation of elastic reverse-time migration using wavefield separation in the frequency domain

    NASA Astrophysics Data System (ADS)

    Chung, Wookeen; Pyun, Sukjoon; Bae, Ho Seuk; Shin, Changsoo; Marfurt, Kurt J.

    2012-06-01

    Considerable effort has been devoted to the migration of multicomponent data in elastic media with wavefield separation techniques being the most successful. Most of this work has been carried out in the time domain. In this paper, we formulate a multicomponent migration technique in the frequency domain. Reverse-time migration can be viewed as the zero-lag cross-correlation between virtual source and back-propagated wavefields. Cross-correlating the Helmholtz decomposed wavefields rather than directly correlating the vector displacement fields results in sharper, more interpretable images, contaminated by fewer crosstalk artefacts. The end products are separate P and S wave (and if desired, PS and SP) migration images. We test our migration algorithm on synthetic seismic data generated using the SEG/EAGE salt-dome, Overthrust and Marmousi-2 models. We correctly image the location and shape of the target zone for oil exploration using these data sets. Furthermore, we demonstrate that our new migration technique provides good images even when the initial velocity model is only approximate.

  6. Comparison of active millimeter-wave and acoustic imaging for weapon detection

    NASA Astrophysics Data System (ADS)

    Sheen, David M.; Collins, H. D.; Gribble, R. Parks; McMakin, Douglas L.

    1997-02-01

    Millimeter-wave holographic imaging techniques have recently been developed for personnel surveillance applications at airports and other high-security checkpoints. Millimeter- wave imaging is useful for this application since millimeter-waves easily pass through common clothing materials yet are reflected from the human body and any items concealed by clothing. This allows a high-resolution imaging system to form an image revealing items concealed on the person imaged. A prototype imaging system developed at Pacific Northwest National Laboratory uses a scanned linear array of millimeter-wave antennas to capture wideband millimeter-wave data in approximately one second. This data is then mathematically reconstructed to form a high- resolution 3D image of the person being scanned. Millimeter- wave imaging has been demonstrated to be effective for detecting concealed weapons on personnel. Another imaging technique which could be applied to the weapon detection problem is acoustic imaging. Like millimeter-waves, ultrasonic acoustic waves can also penetrate clothing, and can be used to form relatively high-resolution images which can reveal concealed weapons on personnel. Acoustic imaging results have been obtained using wideband holographic imaging techniques nearly identical to the imaging techniques used for millimeter-wave imaging. Preliminary imaging results at 50 kHz indicate that acoustic imaging can be used to penetrate some types of common clothing materials. Hard clothing materials, such as leather on vinyl, are essentially opaque to acoustic waves at 50 kHz. In this paper, millimeter-wave and acoustic wave imaging techniques are compared for their effectiveness and suitability in weapon detection imaging systems. Experimental results from both imaging modalities are shown.

  7. Acoustics

    NASA Astrophysics Data System (ADS)

    The acoustics research activities of the DLR fluid-mechanics department (Forschungsbereich Stroemungsmechanik) during 1988 are surveyed and illustrated with extensive diagrams, drawings, graphs, and photographs. Particular attention is given to studies of helicopter rotor noise (high-speed impulsive noise, blade/vortex interaction noise, and main/tail-rotor interaction noise), propeller noise (temperature, angle-of-attack, and nonuniform-flow effects), noise certification, and industrial acoustics (road-vehicle flow noise and airport noise-control installations).

  8. Dual-frequency acoustic droplet vaporization detection for medical imaging.

    PubMed

    Arena, Christopher B; Novell, Anthony; Sheeran, Paul S; Puett, Connor; Moyer, Linsey C; Dayton, Paul A

    2015-09-01

    Liquid-filled perfluorocarbon droplets emit a unique acoustic signature when vaporized into gas-filled microbubbles using ultrasound. Here, we conducted a pilot study in a tissue-mimicking flow phantom to explore the spatial aspects of droplet vaporization and investigate the effects of applied pressure and droplet concentration on image contrast and axial and lateral resolution. Control microbubble contrast agents were used for comparison. A confocal dual-frequency transducer was used to transmit at 8 MHz and passively receive at 1 MHz. Droplet signals were of significantly higher energy than microbubble signals. This resulted in improved signal separation and high contrast-to-tissue ratios (CTR). Specifically, with a peak negative pressure (PNP) of 450 kPa applied at the focus, the CTR of B-mode images was 18.3 dB for droplets and -0.4 for microbubbles. The lateral resolution was dictated by the size of the droplet activation area, with lower pressures resulting in smaller activation areas and improved lateral resolution (0.67 mm at 450 kPa). The axial resolution in droplet images was dictated by the size of the initial droplet and was independent of the properties of the transmit pulse (3.86 mm at 450 kPa). In post-processing, time-domain averaging (TDA) improved droplet and microbubble signal separation at high pressures (640 kPa and 700 kPa). Taken together, these results indicate that it is possible to generate high-sensitivity, high-contrast images of vaporization events. In the future, this has the potential to be applied in combination with droplet-mediated therapy to track treatment outcomes or as a standalone diagnostic system to monitor the physical properties of the surrounding environment. PMID:26415125

  9. Acoustic and Elastodynamic Redatuming for VSP Salt Dome Flank Imaging

    NASA Astrophysics Data System (ADS)

    Lu, R.; Willis, M.; Toksoz, N.

    2007-12-01

    We apply an extension of the concept of Time Reversed Acoustics (TRA) for imaging salt dome flanks using Vertical Seismic Profile (VSP) data. We demonstrate its performance and capabilities on both synthetic acoustic and elastic seismic data from a Gulf of Mexico (GOM) model. This target-oriented strategy eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove the effects of the salt canopy and surrounding overburden. In this study, we use data from surface shots recorded in a well from a walkaway VSP survey. The method, called redatuming, creates a geometry as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process generates effective downhole shot gathers without any knowledge of the overburden velocity structure. The resulting shot gathers are less complex since the VSP ray paths from the surface source are shortened and moved to be as if they started in the borehole, then reflected off the salt flank region and captured in the borehole. After redatuming, we apply multiple passes of prestack migration from the reference datum of the borehole. In our example, the first pass migration, using only simple vertical velocity gradient model, reveals the outline of the salt edge. A second pass of reverse-time prestack depth migration using the full, two-way wave equation, is performed with an updated velocity model that now consists of the velocity gradient and the salt dome. The second pass migration brings out the dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank forming prismatic reflections.

  10. Quantitatively understanding the imprint of fractures in the seismic wave-field

    NASA Astrophysics Data System (ADS)

    Vsemirnova, Ekaterina; Roberts, Alan; Long, Jon; Jones, Richard; McCaffrey, Ken; Hobbs, Richard

    2015-04-01

    Understanding fracture connectivity in the shallow crust is of major importance for the development and production of hydrocarbon fields. Fracture datasets collected from wells have limited spatial coverage compared to remote sensing methods such as seismic imaging, Ground Penetrating Radar (GPR), electromagnetic recording, Terrestrial Laser Scanning (TLS), and Unmanned Aerial Vehicles ("drones"). In this study we focus on quantitatively understanding the imprint of several classes of realistic fracture network on the seismic wave-field. The thin, often rough sheet-like form of fractures poses challenges for reliable imaging of fracture networks using seismic methods, and the seismic response can be significantly altered by the highly variable dip of the fractures. A number of studies have been published showing the effect of the presence of simple fracture configurations on the synthetic seismic wave-field. At present, however, due to the inherent complexity of real fracture networks, there is limited understanding regarding the extraction of network characteristics from seismic data. Our work involves forward seismic wave-field simulation of a range of complex fracture networks derived from detailed quantitative characterisation of fractures in outcrop. We aim to build a library of calibrated examples from which to both develop understanding of the information contained in a seismic dataset related to the fracture network, and further research into the quantitative inversion and imaging of such information.

  11. Full-Field Imaging of GHz Film Bulk Acoustic Resonator Motion

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Cottle, David Lynn; Larson III, J. D.

    2003-10-01

    A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by using dynamic holography with photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed that is capable of operation at gigahertz frequency and micron length scales. Both acoustic amplitude and phase are recorded, allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies of 800-900 MHz, illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric-to-acoustic coupling of these devices and their performance. Images of 256 /spl times/ 240 pixels are recorded at 18 fps rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level at each pixel calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

  12. Acoustic multimode interference and self-imaging phenomena realized in multimodal phononic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Zou, Qiushun; Yu, Tianbao; Liu, Jiangtao; Liu, Nianhua; Wang, Tongbiao; Liao, Qinghua

    2015-09-01

    We report an acoustic multimode interference effect and self-imaging phenomena in an acoustic multimode waveguide system which consists of M parallel phononic crystal waveguides (M-PnCWs). Results show that the self-imaging principle remains applicable for acoustic waveguides just as it does for optical multimode waveguides. To achieve the dispersions and replicas of the input acoustic waves produced along the propagation direction, we performed the finite element method on M-PnCWs, which support M guided modes within the target frequency range. The simulation results show that single images (including direct and mirrored images) and N-fold images (N is an integer) are identified along the propagation direction with asymmetric and symmetric incidence discussed separately. The simulated positions of the replicas agree well with the calculated values that are theoretically decided by self-imaging conditions based on the guided mode propagation analysis. Moreover, the potential applications based on this self-imaging effect for acoustic wavelength de-multiplexing and beam splitting in the acoustic field are also presented.

  13. Negative refraction induced acoustic concentrator and the effects of scattering cancellation, imaging, and mirage

    NASA Astrophysics Data System (ADS)

    Wei, Qi; Cheng, Ying; Liu, Xiao-jun

    2012-07-01

    We present a three-dimensional acoustic concentrator capable of significantly enhancing the sound intensity in the compressive region with scattering cancellation, imaging, and mirage effects. The concentrator shell is built by isotropic gradient negative-index materials, which together with an exterior host medium slab constructs a pair of complementary media. The enhancement factor, which can approach infinity by tuning the geometric parameters, is always much higher than that of a traditional concentrator made by positive-index materials with the same size. The acoustic scattering theory is applied to derive the pressure field distribution of the concentrator, which is consistent with the numerical full-wave simulations. The inherent acoustic impedance match at the interfaces of the shell as well as the inverse processes of “negative refraction—progressive curvature—negative refraction” for arbitrary sound rays can exactly cancel the scattering of the concentrator. In addition, the concentrator shell can also function as an acoustic spherical magnifying superlens, which produces a perfect image with the same shape, with bigger geometric and acoustic parameters located at a shifted position. Then some acoustic mirages are observed whereby the waves radiated from (scattered by) an object located in the center region may seem to be radiated from (scattered by) its image. Based on the mirage effect, we further propose an intriguing acoustic transformer which can transform the sound scattering pattern of one object into another object at will with arbitrary geometric, acoustic, and location parameters.

  14. Acoustics

    NASA Technical Reports Server (NTRS)

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  15. Tracking Energy Flow Using a Volumetric Acoustic Intensity Imager (VAIM)

    NASA Technical Reports Server (NTRS)

    Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas P.

    2006-01-01

    A new measurement device has been invented at the Naval Research Laboratory which images instantaneously the intensity vector throughout a three-dimensional volume nearly a meter on a side. The measurement device consists of a nearly transparent spherical array of 50 inexpensive microphones optimally positioned on an imaginary spherical surface of radius 0.2m. Front-end signal processing uses coherence analysis to produce multiple, phase-coherent holograms in the frequency domain each related to references located on suspect sound sources in an aircraft cabin. The analysis uses either SVD or Cholesky decomposition methods using ensemble averages of the cross-spectral density with the fixed references. The holograms are mathematically processed using spherical NAH (nearfield acoustical holography) to convert the measured pressure field into a vector intensity field in the volume of maximum radius 0.4 m centered on the sphere origin. The utility of this probe is evaluated in a detailed analysis of a recent in-flight experiment in cooperation with Boeing and NASA on NASA s Aries 757 aircraft. In this experiment the trim panels and insulation were removed over a section of the aircraft and the bare panels and windows were instrumented with accelerometers to use as references for the VAIM. Results show excellent success at locating and identifying the sources of interior noise in-flight in the frequency range of 0 to 1400 Hz. This work was supported by NASA and the Office of Naval Research.

  16. Negative refraction imaging of acoustic metamaterial lens in the supersonic range

    SciTech Connect

    Han, Jianning; Wen, Tingdun; Yang, Peng; Zhang, Lu

    2014-05-15

    Acoustic metamaterials with negative refraction index is the most promising method to overcome the diffraction limit of acoustic imaging to achieve ultrahigh resolution. In this paper, we use localized resonant phononic crystal as the unit cell to construct the acoustic negative refraction lens. Based on the vibration model of the phononic crystal, negative quality parameters of the lens are obtained while excited near the system resonance frequency. Simulation results show that negative refraction of the acoustic lens can be achieved when a sound wave transmiting through the phononic crystal plate. The patterns of the imaging field agree well with that of the incident wave, while the dispersion is very weak. The unit cell size in the simulation is 0.0005 m and the wavelength of the sound source is 0.02 m, from which we show that acoustic signal can be manipulated through structures with dimensions much smaller than the wavelength of incident wave.

  17. Breaking the acoustic diffraction limit in photoacoustic imaging with multiple speckle illumination

    NASA Astrophysics Data System (ADS)

    Chaigne, Thomas; Gateau, Jérôme; Allain, Marc; Katz, Ori; Gigan, Sylvain; Sentenac, Anne; Bossy, Emmanuel

    2016-03-01

    In deep photoacoustic imaging, resolution is inherently limited by acoustic diffraction, and ultrasonic frequencies cannot be arbitrarily increased because of attenuation in tissue. Here we report on the use of multiple speckle illumination to perform super resolution photoacoustic imaging. We show that the analysis of speckle-induced second-order fluctuations of the photoacoustic signal combined with deconvolution enables to resolve optically absorbing structures below the acoustic diffraction limit.

  18. An Acoustic Charge Transport Imager for High Definition Television

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin; May, Gary; Glenn, William E.; Richardson, Mike; Solomon, Richard

    1999-01-01

    This project, over its term, included funding to a variety of companies and organizations. In addition to Georgia Tech these included Florida Atlantic University with Dr. William E. Glenn as the P.I., Kodak with Mr. Mike Richardson as the P.I. and M.I.T./Polaroid with Dr. Richard Solomon as the P.I. The focus of the work conducted by these organizations was the development of camera hardware for High Definition Television (HDTV). The focus of the research at Georgia Tech was the development of new semiconductor technology to achieve a next generation solid state imager chip that would operate at a high frame rate (I 70 frames per second), operate at low light levels (via the use of avalanche photodiodes as the detector element) and contain 2 million pixels. The actual cost required to create this new semiconductor technology was probably at least 5 or 6 times the investment made under this program and hence we fell short of achieving this rather grand goal. We did, however, produce a number of spin-off technologies as a result of our efforts. These include, among others, improved avalanche photodiode structures, significant advancement of the state of understanding of ZnO/GaAs structures and significant contributions to the analysis of general GaAs semiconductor devices and the design of Surface Acoustic Wave resonator filters for wireless communication. More of these will be described in the report. The work conducted at the partner sites resulted in the development of 4 prototype HDTV cameras. The HDTV camera developed by Kodak uses the Kodak KAI-2091M high- definition monochrome image sensor. This progressively-scanned charge-coupled device (CCD) can operate at video frame rates and has 9 gm square pixels. The photosensitive area has a 16:9 aspect ratio and is consistent with the "Common Image Format" (CIF). It features an active image area of 1928 horizontal by 1084 vertical pixels and has a 55% fill factor. The camera is designed to operate in continuous mode

  19. Analysis of Particle Image Velocimetry (PIV) Data for Acoustic Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Blackshire, James L.

    1997-01-01

    Acoustic velocity measurements were taken using Particle Image Velocimetry (PIV) in a Normal Incidence Tube configuration at various frequency, phase, and amplitude levels. This report presents the results of the PIV analysis and data reduction portions of the test and details the processing that was done. Estimates of lower measurement sensitivity levels were determined based on PIV image quality, correlation, and noise level parameters used in the test. Comparison of measurements with linear acoustic theory are presented. The onset of nonlinear, harmonic frequency acoustic levels were also studied for various decibel and frequency levels ranging from 90 to 132 dB and 500 to 3000 Hz, respectively.

  20. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr.; Younane Abousleiman

    2004-04-01

    The research during this project has concentrated on developing a correlation between rock deformation mechanisms and their acoustic velocity signature. This has included investigating: (1) the acoustic signature of drained and undrained unconsolidated sands, (2) the acoustic emission signature of deforming high porosity rocks (in comparison to their low porosity high strength counterparts), (3) the effects of deformation on anisotropic elastic and poroelastic moduli, and (4) the acoustic tomographic imaging of damage development in rocks. Each of these four areas involve triaxial experimental testing of weak porous rocks or unconsolidated sand and involves measuring acoustic properties. The research is directed at determining the seismic velocity signature of damaged rocks so that 3-D or 4-D seismic imaging can be utilized to image rock damage. These four areas of study are described in the report: (1) Triaxial compression experiments have been conducted on unconsolidated Oil Creek sand at high confining pressures. (2) Initial experiments on measuring the acoustic emission activity from deforming high porosity Danian chalk were accomplished and these indicate that the AE activity was of a very low amplitude. (3) A series of triaxial compression experiments were conducted to investigate the effects of induced stress on the anisotropy developed in dynamic elastic and poroelastic parameters in rocks. (4) Tomographic acoustic imaging was utilized to image the internal damage in a deforming porous limestone sample. Results indicate that the deformation damage in rocks induced during laboratory experimentation can be imaged tomographically in the laboratory. By extension the results also indicate that 4-D seismic imaging of a reservoir may become a powerful tool for imaging reservoir deformation (including imaging compaction and subsidence) and for imaging zones where drilling operation may encounter hazardous shallow water flows.

  1. Acoustic and optical borehole-wall imaging for fractured-rock aquifer studies

    USGS Publications Warehouse

    Williams, J.H.; Johnson, C.D.

    2004-01-01

    Imaging with acoustic and optical televiewers results in continuous and oriented 360?? views of the borehole wall from which the character, relation, and orientation of lithologic and structural planar features can be defined for studies of fractured-rock aquifers. Fractures are more clearly defined under a wider range of conditions on acoustic images than on optical images including dark-colored rocks, cloudy borehole water, and coated borehole walls. However, optical images allow for the direct viewing of the character of and relation between lithology, fractures, foliation, and bedding. The most powerful approach is the combined application of acoustic and optical imaging with integrated interpretation. Imaging of the borehole wall provides information useful for the collection and interpretation of flowmeter and other geophysical logs, core samples, and hydraulic and water-quality data from packer testing and monitoring. ?? 2003 Elsevier B.V. All rights reserved.

  2. High-quality photoacoustic imaging by using of concentration-adjustable glycerin as an acoustic couplant

    NASA Astrophysics Data System (ADS)

    Yang, Sihua; Gu, Huaimin

    2007-01-01

    The influences of mismatch of ultrasonic propagation velocities on photoacoustic imaging are studied. The concentration-adjustable glycerin is used as an ultrasonic couplant to match the ultrasonic velocities in different media in order to eliminate the acoustic refraction, reduce the acoustic reflection, and rectify the acoustic path difference. Two biological phantoms are tested by using water and glycerin as ultrasonic couplant, respectively. The spatial resolution of reconstructed image by experimental evaluation also is estimated to be 0.12mm. The experimental results demonstrate that the high-quality photoacoustic imaging can be obtained by matching the ultrasonic propagation velocities in different media. The contrast of reconstructed image is significantly improved and the image artifacts are obviously reduced after matching ultrasonic velocity. It has potential to promote photoacoustic imaging as a clinical diagnosis technique.

  3. OASIS in the sea: Measurement of the acoustic reflectivity of zooplankton with concurrent optical imaging

    NASA Astrophysics Data System (ADS)

    Jaffe, J. S.; Ohman, M. D.; De Robertis, A.

    A new instrument Optical-Acoustic Submersible Imaging System (OASIS) has been developed for three-dimensional acoustic tracking of zooplankton with concurrent optical imaging to verify the identity of the insonified organisms. OASIS also measures in situ target strengths (TS) of freely swimming zooplankton and nekton of known identity and 3-D orientation. The system consists of a three-dimensional acoustic imaging system (FishTV), a sensitive optical CCD camera with red-filtered strobe illumination, and ancillary oceanographic sensors. The sonar triggers the acquisition of an optical image when it detects the presence of a significant target in the precise location where the camera, strobe and sonar are co-registered. Acoustic TS can then be related to the optical image, which permits identification of the animal and its 3-D aspect. The system was recently deployed (August 1996) in Saanich Inlet, B.C., Canada. Motile zooplankton and nekton were imaged with no evidence of reaction to or avoidance of the OASIS instrument package. Target strengths of many acoustic reflectors were recorded in parallel with the optical images, triggered by the presence of an animal in the correct location of the sonar system. Inspection of the optical images, corroborated with zooplankton sampling with a MOCNESS net, revealed that the joint optically and acoustically sensed taxa at the site were the euphausiid Euphausia pacifica, the gammarid amphipod Orchomene obtusa, and a gadid fish. The simultaneous optical and acoustic images permitted an exact correlation of TS and taxa. Computer simulations from a model of the backscattered strength from euphausiids are in good agreement with the observed data.

  4. The path to COVIS: A review of acoustic imaging of hydrothermal flow regimes

    NASA Astrophysics Data System (ADS)

    Bemis, Karen G.; Silver, Deborah; Xu, Guangyu; Light, Russ; Jackson, Darrell; Jones, Christopher; Ozer, Sedat; Liu, Li

    2015-11-01

    Acoustic imaging of hydrothermal flow regimes started with the incidental recognition of a plume on a routine sonar scan for obstacles in the path of the human-occupied submersible ALVIN. Developments in sonar engineering, acoustic data processing and scientific visualization have been combined to develop technology which can effectively capture the behavior of focused and diffuse hydrothermal discharge. This paper traces the development of these acoustic imaging techniques for hydrothermal flow regimes from their conception through to the development of the Cabled Observatory Vent Imaging Sonar (COVIS). COVIS has monitored such flow eight times a day for several years. Successful acoustic techniques for estimating plume entrainment, bending, vertical rise, volume flux, and heat flux are presented as is the state-of-the-art in diffuse flow detection.

  5. Scattered Wavefield Within the San Andreas Fault System, California

    NASA Astrophysics Data System (ADS)

    Taira, T.; Silver, P. G.; Niu, F.; Nadeau, R. M.

    2004-12-01

    reveals that they are relatively large (> 2.1 times) along the north-western part of the fault. This result suggests that heterogeneities are concentrated in the north-western segment of this fault, manifested locally as a large degree of scattering. This spatial variation of the scattered wavefield along the Hayward Fault may be related to variations in the stress/strain field. In the case of the Parkfield segment, the high density of borehole seismographs permits the identification of individual scatterers. We applied the imaging method of Taira and Yomogida (2004) incorporating the source array technique presented by Spudich and Bostwick (1987). We selected seismograms from a cluster of 23 aftershocks of the December 20, 1994, M=4.7 Parkfield earthquake, recorded at 10 stations of the HRSN. First, we relocated these aftershocks, using the earthquake catalog data (location and phase) produced by the Northern California Seismic Network and the double-difference earthquake relocation algorithm introduced by Waldhauser and Ellsworth (2000). We then analyzed the coda of observed seismograms in the frequency range 2 - 4 Hz where the signal level was highest, and found what we interpret as a strong S-to-S scatterer located in the south-eastern part of this area at a depth of between 6 - 12 km. We test the hypothesis that this scatterer is related to the 1993 Parkfield aseismic transient event (Gao et al., 2000) by assessing possible time dependence in scatterer properties, through the use of a larger suite of events that spans the time period of the transient.

  6. PhotoAcoustic-guided Focused UltraSound imaging (PAFUSion) for reducing reflection artifacts in photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Singh, Mithun K.; Steenbergen, Wiendelt

    2015-07-01

    Reflection artifacts caused by acoustic reflectors is an important problem in reflection-mode photoacoustic imaging. The light absorbed by skin and superficial optical absorbers may produce high photoacoustic signals, which traverse into the tissue and get reflected from structures having different acoustic impedance. These reflected photoacoustic signals, when reconstructed may appear in the region of interest, which causes complications in interpreting the images. We propose a novel method to identify and reduce reflection artifacts in photoacoustic images by making use of PhotoAcoustic-guided Focused UltraSound [PAFUSion]. Our method ultrasonically mimics the photoacoustic image formation process and thus delivers a clinically feasible way to reduce reflection artifacts. Simulation and phantom measurement results are presented to demonstrate the validity and impact of this method. Results show that PAFUSion technique can identify and differentiate reflection signals from the signals of interest and thus foresees good potential for improving photoacoustic imaging of deep tissue.

  7. RGB representation of two-dimensional multi-spectral acoustic data for object surface profile imaging

    NASA Astrophysics Data System (ADS)

    Guo, Xinhua; Wada, Yuji; Mizuno, Yosuke; Nakamura, Kentaro

    2013-10-01

    Conventionally, acoustic imaging has been performed using a single frequency or a limited number of frequencies. However, the rich information on surface profiles, structures hidden under surfaces and material properties of objects may exhibit frequency dependence. In this study, acoustic imaging on object surface was conducted over a wide frequency range with a fine frequency step, and a method for displaying the acquired multi-spectral acoustic data was proposed. A complicated rigid surface with different profiles was illuminated by sound waves sweeping over the frequency range from 1 to 20 kHz with a 30 Hz step. The reflected sound was two-dimensionally recorded using a scanning microphone, and processed using a holographic reconstruction method. The two-dimensional distributions of obtained sound pressure at each frequency were defined as ‘multi-spectral acoustic imaging data’. Next, the multi-spectral acoustic data were transformed into a single RGB-based picture for easy understanding of the surface characteristics. The acoustic frequencies were allocated to red, green and blue using the RGB filter technique. The depths of the grooves were identified by their colours in the RGB image.

  8. Reconstructed imaging of acoustic cloak using time-lapse reversal method

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Cheng, Ying; Xu, Jian-yi; Li, Bo; Liu, Xiao-jun

    2014-08-01

    We proposed and investigated a solution to the inverse acoustic cloak problem, an anti-stealth technology to make cloaks visible, using the time-lapse reversal (TLR) method. The TLR method reconstructs the image of an unknown acoustic cloak by utilizing scattered acoustic waves. Compared to previous anti-stealth methods, the TLR method can determine not only the existence of a cloak but also its exact geometric information like definite shape, size, and position. Here, we present the process for TLR reconstruction based on time reversal invariance. This technology may have potential applications in detecting various types of cloaks with different geometric parameters.

  9. Opti-acoustic stereo imaging: on system calibration and 3-D target reconstruction.

    PubMed

    Negahdaripour, Shahriar; Sekkati, Hicham; Pirsiavash, Hamed

    2009-06-01

    Utilization of an acoustic camera for range measurements is a key advantage for 3-D shape recovery of underwater targets by opti-acoustic stereo imaging, where the associated epipolar geometry of optical and acoustic image correspondences can be described in terms of conic sections. In this paper, we propose methods for system calibration and 3-D scene reconstruction by maximum likelihood estimation from noisy image measurements. The recursive 3-D reconstruction method utilized as initial condition a closed-form solution that integrates the advantages of two other closed-form solutions, referred to as the range and azimuth solutions. Synthetic data tests are given to provide insight into the merits of the new target imaging and 3-D reconstruction paradigm, while experiments with real data confirm the findings based on computer simulations, and demonstrate the merits of this novel 3-D reconstruction paradigm. PMID:19380272

  10. Liver reserve function assessment by acoustic radiation force impulse imaging

    PubMed Central

    Sun, Xiao-Lan; Liang, Li-Wei; Cao, Hui; Men, Qiong; Hou, Ke-Zhu; Chen, Zhen; Zhao, Ya-E

    2015-01-01

    AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors. METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy. RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively

  11. Image quality, tissue heating, and frame rate trade-offs in acoustic radiation force impulse imaging.

    PubMed

    Bouchard, Richard R; Dahl, Jeremy J; Hsu, Stephen J; Palmeri, Mark L; Trahey, Gregg E

    2009-01-01

    The real-time application of acoustic radiation force impulse (ARFI) imaging requires both short acquisition times for a single ARFI image and repeated acquisition of these frames. Due to the high energy of pulses required to generate appreciable radiation force, however, repeated acquisitions could result in substantial transducer face and tissue heating. We describe and evaluate several novel beam sequencing schemes which, along with parallel-receive acquisition, are designed to reduce acquisition time and heating. These techniques reduce the total number of radiation force impulses needed to generate an image and minimize the time between successive impulses. We present qualitative and quantitative analyses of the trade-offs in image quality resulting from the acquisition schemes. Results indicate that these techniques yield a significant improvement in frame rate with only moderate decreases in image quality. Tissue and transducer face heating resulting from these schemes is assessed through finite element method modeling and thermocouple measurements. Results indicate that heating issues can be mitigated by employing ARFI acquisition sequences that utilize the highest track-to-excitation ratio possible. PMID:19213633

  12. Segmentation of the spinous process and its acoustic shadow in vertebral ultrasound images.

    PubMed

    Berton, Florian; Cheriet, Farida; Miron, Marie-Claude; Laporte, Catherine

    2016-05-01

    Spinal ultrasound imaging is emerging as a low-cost, radiation-free alternative to conventional X-ray imaging for the clinical follow-up of patients with scoliosis. Currently, deformity measurement relies almost entirely on manual identification of key vertebral landmarks. However, the interpretation of vertebral ultrasound images is challenging, primarily because acoustic waves are entirely reflected by bone. To alleviate this problem, we propose an algorithm to segment these images into three regions: the spinous process, its acoustic shadow and other tissues. This method consists, first, in the extraction of several image features and the selection of the most relevant ones for the discrimination of the three regions. Then, using this set of features and linear discriminant analysis, each pixel of the image is classified as belonging to one of the three regions. Finally, the image is segmented by regularizing the pixel-wise classification results to account for some geometrical properties of vertebrae. The feature set was first validated by analyzing the classification results across a learning database. The database contained 107 vertebral ultrasound images acquired with convex and linear probes. Classification rates of 84%, 92% and 91% were achieved for the spinous process, the acoustic shadow and other tissues, respectively. Dice similarity coefficients of 0.72 and 0.88 were obtained respectively for the spinous process and acoustic shadow, confirming that the proposed method accurately segments the spinous process and its acoustic shadow in vertebral ultrasound images. Furthermore, the centroid of the automatically segmented spinous process was located at an average distance of 0.38 mm from that of the manually labeled spinous process, which is on the order of image resolution. This suggests that the proposed method is a promising tool for the measurement of the Spinous Process Angle and, more generally, for assisting ultrasound-based assessment of scoliosis

  13. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin F.; Summers, Chris J.

    1992-01-01

    In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program.

  14. Segmentation and classification of shallow subbottom acoustic data, using image processing and neural networks

    NASA Astrophysics Data System (ADS)

    Yegireddi, Satyanarayana; Thomas, Nitheesh

    2014-06-01

    Subbottom acoustic profiler provides acoustic imaging of the subbottom structure constituting the upper sediment layers of the seabed, which is essential for geological and offshore geo-engineering studies. Delineation of the subbottom structure from a noisy acoustic data and classification of the sediment strata is a challenging task with the conventional signal processing techniques. Image processing techniques utilise the spatial variability of the image characteristics, known for their potential in medical imaging and pattern recognition applications. In the present study, they are found to be good in demarcating the boundaries of the sediment layers associated with weak acoustic reflectivity, masked by noisy background. The study deals with application of image processing techniques, like segmentation in identification of subbottom features and extraction of textural feature vectors using grey level co-occurrence matrix statistics. And also attempted classification using Self Organised Map, an unsupervised neural network model utilising these feature vectors. The methodology was successfully demonstrated in demarcating the different sediment layers from the subbottom images and established the sediments constituting the inferred four subsurface sediment layers differ from each other. The network model was also tested for its consistency, with repeated runs of different configuration of the network. Also the ability of simulated network was tested using a few untrained test images representing the similar environment and the classification results show a good agreement with the anticipated.

  15. Local guided wavefield analysis for characterization of delaminations in composites

    NASA Astrophysics Data System (ADS)

    Rogge, M. D.; Leckey, C. A. C.

    2013-01-01

    Delaminations in composite laminates resulting from impact events may be accompanied by minimal indication of damage at the surface. As such, inspection techniques are required to ensure defects are within allowable limits. Conventional ultrasonic scanning techniques have been shown to effectively characterize the size and depth of delaminations but require physical contact with the structure. Alternatively, a noncontact scanning laser vibrometer may be used to measure guided wave propagation in the laminate structure. A local Fourier domain analysis method is presented for processing guided wavefield data to estimate spatially-dependent wavenumber values, which can be used to determine delamination depth. The technique is applied to simulated wavefields and results are analyzed to determine limitations of the technique with regards to determining defect size and depth. Finally, experimental wavefield data obtained in quasi-isotropic carbon fiber reinforced polymer (CFRP) laminates with impact damage is analyzed and wavenumber is measured to an accuracy of 8.5% in the region of shallow delaminations.

  16. Method and apparatus for detecting internal structures of bulk objects using acoustic imaging

    DOEpatents

    Deason, Vance A.; Telschow, Kenneth L.

    2002-01-01

    Apparatus for producing an acoustic image of an object according to the present invention may comprise an excitation source for vibrating the object to produce at least one acoustic wave therein. The acoustic wave results in the formation of at least one surface displacement on the surface of the object. A light source produces an optical object wavefront and an optical reference wavefront and directs the optical object wavefront toward the surface of the object to produce a modulated optical object wavefront. A modulator operatively associated with the optical reference wavefront modulates the optical reference wavefront in synchronization with the acoustic wave to produce a modulated optical reference wavefront. A sensing medium positioned to receive the modulated optical object wavefront and the modulated optical reference wavefront combines the modulated optical object and reference wavefronts to produce an image related to the surface displacement on the surface of the object. A detector detects the image related to the surface displacement produced by the sensing medium. A processing system operatively associated with the detector constructs an acoustic image of interior features of the object based on the phase and amplitude of the surface displacement on the surface of the object.

  17. Enhancement of time-domain acoustic imaging based on generalized cross-correlation and spatial weighting

    NASA Astrophysics Data System (ADS)

    Quaegebeur, Nicolas; Padois, Thomas; Gauthier, Philippe-Aubert; Masson, Patrice

    2016-06-01

    In this paper, an alternative formulation of the time-domain beamforming is proposed using the generalized cross-correlation of measured signals. This formulation uses spatial weighting functions adapted to microphone positions and imaging points. The proposed approach is demonstrated for acoustic source localization using a microphone array, both theoretically and experimentally. An increase in accuracy of acoustic imaging results is shown for both narrow and broadband sources, while a factor of reduction up to 20 in the computation time can be achieved, allowing real-time or volumetric source localization over very large grids.

  18. Apparatus for real-time acoustic imaging of Rayleigh-Benard convection.

    PubMed

    Kuehn, Kerry; Polfer, Jonathan; Furno, Joanna; Finke, Nathan

    2007-11-01

    We have designed and built an apparatus for real-time acoustic imaging of convective flow patterns in optically opaque fluids. This apparatus takes advantage of recent advances in two-dimensional ultrasound transducer array technology; it employs a modified version of a commercially available ultrasound camera, similar to those employed in nondestructive testing of solids. Images of convection patterns are generated by observing the lateral variation of the temperature dependent speed of sound via refraction of acoustic plane waves passing vertically through the fluid layer. The apparatus has been validated by observing convection rolls in both silicone oil and ferrofluid. PMID:18052477

  19. Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

    NASA Astrophysics Data System (ADS)

    Wen, Jihong; Shen, Huijie; Yu, Dianlong; Wen, Xisen

    2013-11-01

    The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.

  20. Acoustic Imaging of Ferroelectric Domains in BaTiO3 Single Crystals Using Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Zeng, Huarong; Shimamura, Kiyoshi; Kannan, Chinna Venkadasamy; Villora, Encarnacion G.; Takekawa, Shunji; Kitamura, Kenji; Yin, Qingrui

    2007-01-01

    An “alternating-force-modulated” atomic force microscope (AFM) operating in the acoustic mode, generated by launching acoustic waves on the piezoelectric transducer that is attached to the cantilever, was used to visualize the ferroelectric domains in barium titanate (BaTiO3) single crystals by detecting acoustic vibrations generated by the tip and transmitted through the sample placed beneath it to the transducer. The acoustic signal was found to reflect locally elastic microstructures at low frequencies, while high-frequency acoustic images revealed strip like domain configurations of internal substructures in BaTiO3 single crystals. The underlying acoustic imaging mechanism using the AFM was discussed in terms of the interaction between the excited acoustic wave and ferroelectric domains.

  1. Biologically relevant photoacoustic imaging phantoms with tunable optical and acoustic properties.

    PubMed

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

    2016-10-01

    Established medical imaging technologies such as magnetic resonance imaging and computed tomography rely on well-validated tissue-simulating phantoms for standardized testing of device image quality. The availability of high-quality phantoms for optical-acoustic diagnostics such as photoacoustic tomography (PAT) will facilitate standardization and clinical translation of these emerging approaches. Materials used in prior PAT phantoms do not provide a suitable combination of long-term stability and realistic acoustic and optical properties. Therefore, we have investigated the use of custom polyvinyl chloride plastisol (PVCP) formulations for imaging phantoms and identified a dual-plasticizer approach that provides biologically relevant ranges of relevant properties. Speed of sound and acoustic attenuation were determined over a frequency range of 4 to 9 MHz and optical absorption and scattering over a wavelength range of 400 to 1100 nm. We present characterization of several PVCP formulations, including one designed to mimic breast tissue. This material is used to construct a phantom comprised of an array of cylindrical, hemoglobin-filled inclusions for evaluation of penetration depth. Measurements with a custom near-infrared PAT imager provide quantitative and qualitative comparisons of phantom and tissue images. Results indicate that our PVCP material is uniquely suitable for PAT system image quality evaluation and may provide a practical tool for device validation and intercomparison. PMID:26886681

  2. Seismic interferometry by multidimensional deconvolution without wavefield separation

    NASA Astrophysics Data System (ADS)

    Ravasi, Matteo; Meles, Giovanni; Curtis, Andrew; Rawlinson, Zara; Yikuo, Liu

    2015-07-01

    Seismic interferometry comprises a suite of methods to redatum recorded wavefields to those that would have been recorded if different sources (so-called virtual sources) had been activated. Seismic interferometry by cross-correlation has been formulated using either two-way (for full wavefields) or one-way (for directionally decomposed wavefields) representation theorems. To obtain improved Green's function estimates, the cross-correlation result can be deconvolved by a quantity that identifies the smearing of the virtual source in space and time, the so-called point-spread function. This type of interferometry, known as interferometry by multidimensional deconvolution (MDD), has so far been applied only to one-way directionally decomposed fields, requiring accurate wavefield decomposition from dual (e.g. pressure and velocity) recordings. Here we propose a form of interferometry by multidimensional deconvolution that uses full wavefields with two-way representations, and simultaneously invert for pressure and (normal) velocity Green's functions, rather than only velocity responses as for its one-way counterpart. Tests on synthetic data show that two-way MDD improves on results of interferometry by cross-correlation, and generally produces estimates of similar quality to those obtained by one-way MDD, suggesting that the preliminary decomposition into up- and downgoing components of the pressure field is not required if pressure and velocity data are jointly used in the deconvolution. We also show that constraints on the directionality of the Green's functions sought can be added directly into the MDD inversion process to further improve two-way multidimensional deconvolution. Finally, as a by-product of having pressure and particle velocity measurements, we adapt one- and two-way representation theorems to convert any particle velocity receiver into its corresponding virtual dipole/gradient source by means of MDD. Thus data recorded from standard monopolar (e

  3. An echolocation model for the restoration of an acoustic image from a single-emission echo

    NASA Astrophysics Data System (ADS)

    Matsuo, Ikuo; Yano, Masafumi

    2004-12-01

    Bats can form a fine acoustic image of an object using frequency-modulated echolocation sound. The acoustic image is an impulse response, known as a reflected-intensity distribution, which is composed of amplitude and phase spectra over a range of frequencies. However, bats detect only the amplitude spectrum due to the low-time resolution of their peripheral auditory system, and the frequency range of emission is restricted. It is therefore necessary to restore the acoustic image from limited information. The amplitude spectrum varies with the changes in the configuration of the reflected-intensity distribution, while the phase spectrum varies with the changes in its configuration and location. Here, by introducing some reasonable constraints, a method is proposed for restoring an acoustic image from the echo. The configuration is extrapolated from the amplitude spectrum of the restricted frequency range by using the continuity condition of the amplitude spectrum at the minimum frequency of the emission and the minimum phase condition. The determination of the location requires extracting the amplitude spectra, which vary with its location. For this purpose, the Gaussian chirplets with a carrier frequency compatible with bat emission sweep rates were used. The location is estimated from the temporal changes of the amplitude spectra. .

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

    NASA Technical Reports Server (NTRS)

    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.

  5. Source Stacking for Numerical Wavefield Computations - Application to Global Scale Seismic Mantle Tomography

    NASA Astrophysics Data System (ADS)

    MacLean, L. S.; Romanowicz, B. A.; French, S.

    2015-12-01

    Seismic wavefield computations using the Spectral Element Method are now regularly used to recover tomographic images of the upper mantle and crust at the local, regional, and global scales (e.g. Fichtner et al., GJI, 2009; Tape et al., Science 2010; Lekic and Romanowicz, GJI, 2011; French and Romanowicz, GJI, 2014). However, the heaviness of the computations remains a challenge, and contributes to limiting the resolution of the produced images. Using source stacking, as suggested by Capdeville et al. (GJI,2005), can considerably speed up the process by reducing the wavefield computations to only one per each set of N sources. This method was demonstrated through synthetic tests on low frequency datasets, and therefore should work for global mantle tomography. However, the large amplitudes of surface waves dominates the stacked seismograms and these cases can no longer be separated by windowing in the time domain. We have developed a processing approach that helps address this issue and demonstrate its usefulness through a series of synthetic tests performed at long periods (T >60 s) on toy upper mantle models. The summed synthetics are computed using the CSEM code (Capdeville et al., 2002). As for the inverse part of the procedure, we use a quasi-Newton method, computing Frechet derivatives and Hessian using normal mode perturbation theory.

  6. A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

    PubMed Central

    Sou, In Mei; Layman, Christopher N.; Ray, Chittaranjan

    2013-01-01

    Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

  7. Time-resolved coherent X-ray diffraction imaging of surface acoustic waves

    PubMed Central

    Nicolas, Jan-David; Reusch, Tobias; Osterhoff, Markus; Sprung, Michael; Schülein, Florian J. R.; Krenner, Hubert J.; Wixforth, Achim; Salditt, Tim

    2014-01-01

    Time-resolved coherent X-ray diffraction experiments of standing surface acoustic waves, illuminated under grazing incidence by a nanofocused synchrotron beam, are reported. The data have been recorded in stroboscopic mode at controlled and varied phase between the acoustic frequency generator and the synchrotron bunch train. At each time delay (phase angle), the coherent far-field diffraction pattern in the small-angle regime is inverted by an iterative algorithm to yield the local instantaneous surface height profile along the optical axis. The results show that periodic nanoscale dynamics can be imaged at high temporal resolution in the range of 50 ps (pulse length). PMID:25294979

  8. A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow.

    PubMed

    Sou, In Mei; Allen, John S; Layman, Christopher N; Ray, Chittaranjan

    2011-11-01

    Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

  9. Characterization of acoustic streaming and heating using synchronized infrared thermography and particle image velocimetry.

    PubMed

    Layman, Christopher N; Sou, In Mei; Bartak, Rico; Ray, Chittaranjan; Allen, John S

    2011-09-01

    Real-time measurements of acoustic streaming velocities and surface temperature fields using synchronized particle image velocimetry and infrared thermography are reported. Measurements were conducted using a 20 kHz Langevin type acoustic horn mounted vertically in a model sonochemical reactor of either degassed water or a glycerin-water mixture. These dissipative phenomena are found to be sensitive to small variations in the medium viscosity, and a correlation between the heat flux and vorticity was determined for unsteady convective heat transfer. PMID:21514205

  10. Modern Techniques in Acoustical Signal and Image Processing

    SciTech Connect

    Candy, J V

    2002-04-04

    Acoustical signal processing problems can lead to some complex and intricate techniques to extract the desired information from noisy, sometimes inadequate, measurements. The challenge is to formulate a meaningful strategy that is aimed at performing the processing required even in the face of uncertainties. This strategy can be as simple as a transformation of the measured data to another domain for analysis or as complex as embedding a full-scale propagation model into the processor. The aims of both approaches are the same--to extract the desired information and reject the extraneous, that is, develop a signal processing scheme to achieve this goal. In this paper, we briefly discuss this underlying philosophy from a ''bottom-up'' approach enabling the problem to dictate the solution rather than visa-versa.

  11. An acoustic charge transport imager for high definition television applications

    NASA Technical Reports Server (NTRS)

    Hunt, William D.; Brennan, Kevin F.; Summers, Christopher J.

    1993-01-01

    This report covers: (1) invention of a new, ultra-low noise, low operating voltage APD which is expected to offer far better performance than the existing volume doped APD device; (2) performance of a comprehensive series of experiments on the acoustic and piezoelectric properties of ZnO films sputtered on GaAs which can possibly lead to a decrease in the required rf drive power for ACT devices by 15dB; (3) development of an advanced, hydrodynamic, macroscopic simulator used for evaluating the performance of ACT and CTD devices and aiding in the development of the next generation of devices; (4) experimental development of CTD devices which utilize a p-doped top barrier demonstrating charge storage capacity and low leakage currents; (5) refinements in materials growth techniques and in situ controls to lower surface defect densities to record levels as well as increase material uniformity and quality.

  12. Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2003-12-01

    A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

  13. Investigation of an acoustical holography system for real-time imaging

    NASA Astrophysics Data System (ADS)

    Fecht, Barbara A.; Andre, Michael P.; Garlick, George F.; Shelby, Ronald L.; Shelby, Jerod O.; Lehman, Constance D.

    1998-07-01

    A new prototype imaging system based on ultrasound transmission through the object of interest -- acoustical holography -- was developed which incorporates significant improvements in acoustical and optical design. This system is being evaluated for potential clinical application in the musculoskeletal system, interventional radiology, pediatrics, monitoring of tumor ablation, vascular imaging and breast imaging. System limiting resolution was estimated using a line-pair target with decreasing line thickness and equal separation. For a swept frequency beam from 2.6 - 3.0 MHz, the minimum resolution was 0.5 lp/mm. Apatite crystals were suspended in castor oil to approximate breast microcalcifications. Crystals from 0.425 - 1.18 mm in diameter were well resolved in the acoustic zoom mode. Needle visibility was examined with both a 14-gauge biopsy needle and a 0.6 mm needle. The needle tip was clearly visible throughout the dynamic imaging sequence as it was slowly inserted into a RMI tissue-equivalent breast biopsy phantom. A selection of human images was acquired in several volunteers: a 25 year-old female volunteer with normal breast tissue, a lateral view of the elbow joint showing muscle fascia and tendon insertions, and the superficial vessels in the forearm. Real-time video images of these studies will be presented. In all of these studies, conventional sonography was used for comparison. These preliminary investigations with the new prototype acoustical holography system showed favorable results in comparison to state-of-the-art pulse-echo ultrasound and demonstrate it to be suitable for further clinical study. The new patient interfaces will facilitate orthopedic soft tissue evaluation, study of superficial vascular structures and potentially breast imaging.

  14. Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging

    NASA Technical Reports Server (NTRS)

    Chou, Dean-Yi; Duvall, Thomas L.; Sun, Ming-Tsung; Chang, Hsiang-Kuang; Jimenez, Antonio; Rabello-Soares, Maria Cristina; Ai, Guoxiang; Wang, Gwo-Ping; Goode Philip; Marquette, William; Ehgamberdiev, Shuhrat; Landenkov, Oleg

    1999-01-01

    Time-distance analysis and acoustic imaging are two related techniques to probe the local properties of solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. The location of the envelope peak of the cross correlation function in time-distance analysis is identified as the travel time of the wave packet formed by modes with the same w/l. The phase time of the cross correlation function provides information of the phase change accumulated along the wave path, including the phase change at the boundaries of the mode cavity. The acoustic signals constructed with the technique of acoustic imaging contain both phase and intensity information. The phase of constructed signals can be studied by computing the cross correlation function between time series constructed with ingoing and outgoing waves. In this study, we use the data taken with the Taiwan Oscillation Network (TON) instrument and the Michelson Doppler Imager (MDI) instrument. The analysis is carried out for the quiet Sun. We use the relation of envelope time versus distance measured in time-distance analyses to construct the acoustic signals in acoustic imaging analyses. The phase time of the cross correlation function of constructed ingoing and outgoing time series is twice the difference between the phase time and envelope time in time-distance analyses as predicted. The envelope peak of the cross correlation function between constructed ingoing and outgoing time series is located at zero time as predicted for results of one-bounce at 3 mHz for all four data sets and two-bounce at 3 mHz for two TON data sets. But it is different from zero for other cases. The cause of the deviation of the envelope peak from zero is not known.

  15. Numerical Simulation of Target Range Estimation Using Ambient Noise Imaging with Acoustic Lens

    NASA Astrophysics Data System (ADS)

    Kazuyoshi Mori,; Hanako Ogasawara,; Toshiaki Nakamura,; Takenobu Tsuchiya,; Nobuyuki Endoh,

    2010-07-01

    In ambient noise imaging (ANI), each pixel of a target image is mapped by either monochrome or pseudo color to represent its acoustic intensity in each direction. This intensity is obtained by measuring the target object’s reflecting or scattering wave, with ocean background noise serving as the sound source. In the case of using an acoustic lens, the ANI system creates a C-mode-like image, where receivers are arranged on a focal plane and each pixel’s color corresponds to the intensity of each receiver output. There is no consideration for estimating a target range by this method, because it is impossible to measure the traveling time between a transducer and a target by a method like an active imaging sonar. In this study, we tried to estimate a target range using the ANI system with an acoustic lens. Here, we conducted a numerical simulation of sound propagation based on the principle of the time reversal mirror. First, instead of actual ocean measurements in the forward propagation, we calculated the scattering wave from a rigid target object in an acoustic noise field generated by a large number of point sources using the two-dimensional (2D) finite difference time domain (FDTD) method. The time series of the scattering wave converged by the lens was then recorded on each receiver. The sound pressure distribution assuming that the time-reversed wave of the scattering wave was reradiated from each receiver position was also calculated using the 2D FDTD method in the backward propagation. It was possible to estimate a target range using the ANI system with an acoustic lens, because the maximum position of the reradiated sound pressure field was close to the target position.

  16. Numerical Simulation of Target Range Estimation Using Ambient Noise Imaging with Acoustic Lens

    NASA Astrophysics Data System (ADS)

    Mori, Kazuyoshi; Ogasawara, Hanako; Nakamura, Toshiaki; Tsuchiya, Takenobu; Endoh, Nobuyuki

    2010-07-01

    In ambient noise imaging (ANI), each pixel of a target image is mapped by either monochrome or pseudo color to represent its acoustic intensity in each direction. This intensity is obtained by measuring the target object's reflecting or scattering wave, with ocean background noise serving as the sound source. In the case of using an acoustic lens, the ANI system creates a C-mode-like image, where receivers are arranged on a focal plane and each pixel's color corresponds to the intensity of each receiver output. There is no consideration for estimating a target range by this method, because it is impossible to measure the traveling time between a transducer and a target by a method like an active imaging sonar. In this study, we tried to estimate a target range using the ANI system with an acoustic lens. Here, we conducted a numerical simulation of sound propagation based on the principle of the time reversal mirror. First, instead of actual ocean measurements in the forward propagation, we calculated the scattering wave from a rigid target object in an acoustic noise field generated by a large number of point sources using the two-dimensional (2D) finite difference time domain (FDTD) method. The time series of the scattering wave converged by the lens was then recorded on each receiver. The sound pressure distribution assuming that the time-reversed wave of the scattering wave was reradiated from each receiver position was also calculated using the 2D FDTD method in the backward propagation. It was possible to estimate a target range using the ANI system with an acoustic lens, because the maximum position of the reradiated sound pressure field was close to the target position.

  17. The Effects of Nonlinear Propagation on Acoustic Source Imaging in One-Dimension

    NASA Astrophysics Data System (ADS)

    Shepherd, Micah; Gee, Kent L.

    2006-10-01

    The acoustics of finite-amplitude (nonlinear) sound sources, such as rockets and jets, are not well understood. Characterization of sound pressure amplitudes, aeroacoustic source locations and frequency dependence of these sources is needed to assess the impact of the acoustic field on the launch equipment and surrounding environment. Nonlinear propagation of high-amplitude sound is being studied to determine if a source-imaging method called near-field acoustical holography (NAH), which is based on linear assumptions, can be used to estimate the source information mentioned. A one-dimensional numerical algorithm is being used to linearly and nonlinearly propagate the radiation from a monofrequency source. NAH is used to reconstruct the source information from the simulated data and the error is determined in decibels.

  18. Schlieren imaging of the standing wave field in an ultrasonic acoustic levitator

    NASA Astrophysics Data System (ADS)

    Rendon, Pablo Luis; Boullosa, Ricardo R.; Echeverria, Carlos; Porta, David

    2015-11-01

    We consider a model of a single axis acoustic levitator consisting of two cylinders immersed in air and directed along the same axis. The first cylinder has a flat termination and functions as a sound emitter, and the second cylinder, which is simply a refector, has the side facing the first cylinder cut out by a spherical surface. By making the first cylinder vibrate at ultrasonic frequencies a standing wave is produced in the air between the cylinders which makes it possible, by means of the acoustic radiation pressure, to levitate one or several small objects of different shapes, such as spheres or disks. We use schlieren imaging to observe the acoustic field resulting from the levitation of one or several objects, and compare these results to previous numerical approximations of the field obtained using a finite element method. The authors acknowledge financial support from DGAPA-UNAM through project PAPIIT IN109214.

  19. Imaging of transient surface acoustic waves by full-field photorefractive interferometry

    SciTech Connect

    Xiong, Jichuan; Xu, Xiaodong E-mail: christ.glorieux@fys.kuleuven.be; Glorieux, Christ E-mail: christ.glorieux@fys.kuleuven.be; Matsuda, Osamu; Cheng, Liping

    2015-05-15

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz.

  20. Acoustic imaging with time reversal methods: From medicine to NDT

    NASA Astrophysics Data System (ADS)

    Fink, Mathias

    2015-03-01

    This talk will present an overview of the research conducted on ultrasonic time-reversal methods applied to biomedical imaging and to non-destructive testing. We will first describe iterative time-reversal techniques that allow both focusing ultrasonic waves on reflectors in tissues (kidney stones, micro-calcifications, contrast agents) or on flaws in solid materials. We will also show that time-reversal focusing does not need the presence of bright reflectors but it can be achieved only from the speckle noise generated by random distributions of non-resolved scatterers. We will describe the applications of this concept to correct distortions and aberrations in ultrasonic imaging and in NDT. In the second part of the talk we will describe the concept of time-reversal processors to get ultrafast ultrasonic images with typical frame rates of order of 10.000 F/s. It is the field of ultrafast ultrasonic imaging that has plenty medical applications and can be of great interest in NDT. We will describe some applications in the biomedical domain: Quantitative Elasticity imaging of tissues by following shear wave propagation to improve cancer detection and Ultrafast Doppler imaging that allows ultrasonic functional imaging.

  1. Multi-acoustic lens design methodology for a low cost C-scan photoacoustic imaging camera

    NASA Astrophysics Data System (ADS)

    Chinni, Bhargava; Han, Zichao; Brown, Nicholas; Vallejo, Pedro; Jacobs, Tess; Knox, Wayne; Dogra, Vikram; Rao, Navalgund

    2016-03-01

    We have designed and implemented a novel acoustic lens based focusing technology into a prototype photoacoustic imaging camera. All photoacoustically generated waves from laser exposed absorbers within a small volume get focused simultaneously by the lens onto an image plane. We use a multi-element ultrasound transducer array to capture the focused photoacoustic signals. Acoustic lens eliminates the need for expensive data acquisition hardware systems, is faster compared to electronic focusing and enables real-time image reconstruction. Using this photoacoustic imaging camera, we have imaged more than 150 several centimeter size ex-vivo human prostate, kidney and thyroid specimens with a millimeter resolution for cancer detection. In this paper, we share our lens design strategy and how we evaluate the resulting quality metrics (on and off axis point spread function, depth of field and modulation transfer function) through simulation. An advanced toolbox in MATLAB was adapted and used for simulating a two-dimensional gridded model that incorporates realistic photoacoustic signal generation and acoustic wave propagation through the lens with medium properties defined on each grid point. Two dimensional point spread functions have been generated and compared with experiments to demonstrate the utility of our design strategy. Finally we present results from work in progress on the use of two lens system aimed at further improving some of the quality metrics of our system.

  2. Vibro-acoustography: An imaging modality based on ultrasound-stimulated acoustic emission

    PubMed Central

    Fatemi, Mostafa; Greenleaf, James F.

    1999-01-01

    We describe theoretical principles of an imaging modality that uses the acoustic response of an object to a highly localized dynamic radiation force of an ultrasound field. In this method, named ultrasound-stimulated vibro-acoustography (USVA), ultrasound is used to exert a low-frequency (in kHz range) force on the object. In response, a portion of the object vibrates sinusoidally in a pattern determined by its viscoelastic properties. The acoustic emission field resulting from object vibration is detected and used to form an image that represents both the ultrasonic and low-frequency (kHz range) mechanical characteristics of the object. We report the relation between the emitted acoustic field and the incident ultrasonic pressure field in terms of object parameters. Also, we present the point-spread function of the imaging system. The experimental images in this report have a resolution of about 700 μm, high contrast, and high signal-to-noise ratio. USVA is sensitive enough to detect object motions on the order of nanometers. Possible applications include medical imaging and material evaluation. PMID:10359758

  3. Multifrequency microwave-induced thermal acoustic imaging for breast cancer detection.

    PubMed

    Guo, Bin; Li, Jian; Zmuda, Henry; Sheplak, Mark

    2007-11-01

    Microwave-induced thermal acoustic imaging (TAI) is a promising early breast cancer detection technique, which combines the advantages of microwave stimulation and ultrasound imaging and offers a high imaging contrast, as well as high spatial resolution at the same time. A new multifrequency microwave-induced thermal acoustic imaging scheme for early breast cancer detection is proposed in this paper. Significantly more information about the human breast can be gathered using multiple frequency microwave stimulation. A multifrequency adaptive and robust technique (MART) is presented for image formation. Due to its data-adaptive nature, MART can achieve better resolution and better interference rejection capability than its data-independent counterparts, such as the delay-and-sum method. The effectiveness of this procedure is shown by several numerical examples based on 2-D breast models. The finite-difference time-domain method is used to simulate the electromagnetic field distribution, the absorbed microwave energy density, and the thermal acoustic field in the breast model. PMID:18018695

  4. Acoustical and optical scattering and imaging of tissues: an overview

    NASA Astrophysics Data System (ADS)

    Ishimaru, Akira

    2001-05-01

    This talk will first give a general discussion on the ultrasound media characteristics of blood and spectral densities of tissues. The first-order scattering theory, multiple scattering theory, Doppler spectrum, cw and pulse scattering, focused beam, beam spot-size, speckle, texture, and rough interface effects will be presented. Imaging through tissues will then be discussed in terms of temporal and spatial resolutions, contrast, MTF (modulation transfer function), SAR and confocal imaging techniques, tomographic and holographic imaging, and inverse scattering. Next, we discuss optical diffusion in blood and tissues, radiative transfer theory, photon density waves, and polarization effects.

  5. Measurement of acoustic velocity in the stack of a thermoacoustic refrigerator using particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Berson, Arganthaël; Michard, Marc; Blanc-Benon, Philippe

    2008-06-01

    Thermoacoustic refrigeration systems generate cooling power from a high-amplitude acoustic standing wave. There has recently been a growing interest in this technology because of its simple and robust architecture and its use of environmentally safe gases. With the prospect of commercialization, it is necessary to enhance the efficiency of thermoacoustic cooling systems and more particularly of some of their components such as the heat exchangers. The characterization of the flow field at the end of the stack plates is a crucial step for the understanding and optimization of heat transfer between the stack and the heat exchangers. In this study, a specific particle image velocimetry measurement is performed inside a thermoacoustic refrigerator. Acoustic velocity is measured using synchronization and phase-averaging. The measurement method is validated inside a void resonator by successfully comparing experimental data with an acoustic plane wave model. Velocity is measured inside the oscillating boundary layers, between the plates of the stack, and compared to a linear model. The flow behind the stack is characterized, and it shows the generation of symmetric pairs of counter-rotating vortices at the end of the stack plates at low acoustic pressure level. As the acoustic pressure level increases, detachment of the vortices and symmetry breaking are observed.

  6. Methods And Systems For Using Reference Images In Acoustic Image Processing

    DOEpatents

    Moore, Thomas L.; Barter, Robert Henry

    2005-01-04

    A method and system of examining tissue are provided in which a field, including at least a portion of the tissue and one or more registration fiducials, is insonified. Scattered acoustic information, including both transmitted and reflected waves, is received from the field. A representation of the field, including both the tissue and the registration fiducials, is then derived from the received acoustic radiation.

  7. Three dimensional full-wave nonlinear acoustic simulations: Applications to ultrasound imaging

    SciTech Connect

    Pinton, Gianmarco

    2015-10-28

    Characterization of acoustic waves that propagate nonlinearly in an inhomogeneous medium has significant applications to diagnostic and therapeutic ultrasound. The generation of an ultrasound image of human tissue is based on the complex physics of acoustic wave propagation: diffraction, reflection, scattering, frequency dependent attenuation, and nonlinearity. The nonlinearity of wave propagation is used to the advantage of diagnostic scanners that use the harmonic components of the ultrasonic signal to improve the resolution and penetration of clinical scanners. One approach to simulating ultrasound images is to make approximations that can reduce the physics to systems that have a low computational cost. Here a maximalist approach is taken and the full three dimensional wave physics is simulated with finite differences. This paper demonstrates how finite difference simulations for the nonlinear acoustic wave equation can be used to generate physically realistic two and three dimensional ultrasound images anywhere in the body. A specific intercostal liver imaging scenario for two cases: with the ribs in place, and with the ribs removed. This configuration provides an imaging scenario that cannot be performed in vivo but that can test the influence of the ribs on image quality. Several imaging properties are studied, in particular the beamplots, the spatial coherence at the transducer surface, the distributed phase aberration, and the lesion detectability for imaging at the fundamental and harmonic frequencies. The results indicate, counterintuitively, that at the fundamental frequency the beamplot improves due to the apodization effect of the ribs but at the same time there is more degradation from reverberation clutter. At the harmonic frequency there is significantly less improvement in the beamplot and also significantly less degradation from reverberation. It is shown that even though simulating the full propagation physics is computationally challenging it

  8. Full-wave Nonlinear Inverse Scattering for Acoustic and Electromagnetic Breast Imaging

    NASA Astrophysics Data System (ADS)

    Haynes, Mark Spencer

    Acoustic and electromagnetic full-wave nonlinear inverse scattering techniques are explored in both theory and experiment with the ultimate aim of noninvasively mapping the material properties of the breast. There is evidence that benign and malignant breast tissue have different acoustic and electrical properties and imaging these properties directly could provide higher quality images with better diagnostic certainty. In this dissertation, acoustic and electromagnetic inverse scattering algorithms are first developed and validated in simulation. The forward solvers and optimization cost functions are modified from traditional forms in order to handle the large or lossy imaging scenes present in ultrasonic and microwave breast imaging. An antenna model is then presented, modified, and experimentally validated for microwave S-parameter measurements. Using the antenna model, a new electromagnetic volume integral equation is derived in order to link the material properties of the inverse scattering algorithms to microwave S-parameters measurements allowing direct comparison of model predictions and measurements in the imaging algorithms. This volume integral equation is validated with several experiments and used as the basis of a free-space inverse scattering experiment, where images of the dielectric properties of plastic objects are formed without the use of calibration targets. These efforts are used as the foundation of a solution and formulation for the numerical characterization of a microwave near-field cavity-based breast imaging system. The system is constructed and imaging results of simple targets are given. Finally, the same techniques are used to explore a new self-characterization method for commercial ultrasound probes. The method is used to calibrate an ultrasound inverse scattering experiment and imaging results of simple targets are presented. This work has demonstrated the feasibility of quantitative microwave inverse scattering by way of a self

  9. Three dimensional full-wave nonlinear acoustic simulations: Applications to ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Pinton, Gianmarco

    2015-10-01

    Characterization of acoustic waves that propagate nonlinearly in an inhomogeneous medium has significant applications to diagnostic and therapeutic ultrasound. The generation of an ultrasound image of human tissue is based on the complex physics of acoustic wave propagation: diffraction, reflection, scattering, frequency dependent attenuation, and nonlinearity. The nonlinearity of wave propagation is used to the advantage of diagnostic scanners that use the harmonic components of the ultrasonic signal to improve the resolution and penetration of clinical scanners. One approach to simulating ultrasound images is to make approximations that can reduce the physics to systems that have a low computational cost. Here a maximalist approach is taken and the full three dimensional wave physics is simulated with finite differences. This paper demonstrates how finite difference simulations for the nonlinear acoustic wave equation can be used to generate physically realistic two and three dimensional ultrasound images anywhere in the body. A specific intercostal liver imaging scenario for two cases: with the ribs in place, and with the ribs removed. This configuration provides an imaging scenario that cannot be performed in vivo but that can test the influence of the ribs on image quality. Several imaging properties are studied, in particular the beamplots, the spatial coherence at the transducer surface, the distributed phase aberration, and the lesion detectability for imaging at the fundamental and harmonic frequencies. The results indicate, counterintuitively, that at the fundamental frequency the beamplot improves due to the apodization effect of the ribs but at the same time there is more degradation from reverberation clutter. At the harmonic frequency there is significantly less improvement in the beamplot and also significantly less degradation from reverberation. It is shown that even though simulating the full propagation physics is computationally challenging it

  10. Focused acoustic beam imaging of grain structure and local Young's modulus with Rayleigh and surface skimming longitudinal waves

    SciTech Connect

    Martin, R. W.; Sathish, S.; Blodgett, M. P.

    2013-01-25

    The interaction of a focused acoustic beam with materials generates Rayleigh surface waves (RSW) and surface skimming longitudinal waves (SSLW). Acoustic microscopic investigations have used the RSW amplitude and the velocity measurements, extensively for grain structure analysis. Although, the presence of SSLW has been recognized, it is rarely used in acoustic imaging. This paper presents an approach to perform microstructure imaging and local elastic modulus measurements by combining both RSW and SSLW. The acoustic imaging of grain structure was performed by measuring the amplitude of RSW and SSLW signal. The microstructure images obtained on the same region of the samples with RSW and SSLW are compared and the difference in the contrast observed is discussed based on the propagation characteristics of the individual surface waves. The velocity measurements are determined by two point defocus method. The surface wave velocities of RSW and SSLW of the same regions of the sample are combined and presented as average Young's modulus image.

  11. Quantitative high-resolution acoustic imaging of the seafloor

    NASA Astrophysics Data System (ADS)

    Holland, C. W.; Dettmer, J.; Steininger, G.; Dosso, S. E.

    2013-12-01

    Quantifying the properties of the seafloor interface and near surface (a few tens of meters) is of considerable interest to science as well as industry. Scales of interest range from the order of tens of kilometers (survey size) down to less than a centimeter. These scales can be probed using an AUV equipped with a broadband source and a short streamer. The data are processed for energy (rather than peak) reflection coefficients and scattering cross-section versus bi-static angle. In order to tackle spatial scales ranging over 8 orders of magnitude of, it is useful to divide the parameter space into deterministic and stochastic parameters. The energy reflection coefficients contain information on deterministic properties including sound speed, density and attenuation vs depth in the upper tens of meters of sediment. Vertical resolution is a function of depth, but typically of order 0.1 m near surface. The statistical properties of the smaller scales, i.e., seafloor roughness and/or volume heterogeneities are obtained from the bi-static scattering data. Physics-based models are used to relate the sediment micro-structure (the Buckingham model) and sediment fluctuations (the Von Karman spectrum) to the acoustic observables. Quantitative parameter and inter-parameter uncertainties are obtained from Bayesian methods for both deterministic and stochastic parameters.

  12. Analysis and verification of dominant factor to obtain the high resolution photo-acoustic imaging

    NASA Astrophysics Data System (ADS)

    Hirasawa, T.; Ishihara, M.; Kitagaki, M.; Bansaku, I.; Fujita, M.; Kikuchi, M.

    2011-03-01

    Our goal is to develop a photo-acoustic imaging (PAI) system which offers functional image of living tissues and organs with high resolution. In order to obtain high resolution image, we implemented the Fourier transform reconstruction algorithm which determines an optical absorption distribution from photo-acoustic (PA) signals. However, resolutions of reconstructed images were restricted by the sensor directionality, finite scan width and frequency band width. There was an essential requirement to optimize the sensor specification. In this study, we demonstrated relationship between image resolution and sensor specification by simulation and experiment. In our experimental system, PA signals were acquired by line scanning of our fabricated P(VDF/TrFE) film sensor. As results of simulations and experiments, lateral resolutions of PA images were restricted by the directionality of sensor. Furthermore, by limiting scan width and frequency band width, lateral resolution is decreased at deep region. The optimum sensor specification depends on the imaging region due to some trade-offs, for example, a sensor with wider directionality has less sensitivity, wider scan in same step increases acquisition time. Therefore, the results could indicate the possibility of optimizing sensor directionality, scan width and frequency band width for various depths and volumes of imaging region.

  13. Synthetic aperture acoustic imaging of canonical targets with a 2-15 kHz linear FM chirp

    NASA Astrophysics Data System (ADS)

    Vignola, Joseph F.; Judge, John A.; Good, Chelsea E.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

    2011-06-01

    Synthetic aperture image reconstruction applied to outdoor acoustic recordings is presented. Acoustic imaging is an alternate method having several military relevant advantages such as being immune to RF jamming, superior spatial resolution, capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to 0.5 - 3 GHz ground penetrating radar technologies. Synthetic aperture acoustic imaging is similar to synthetic aperture radar, but more akin to synthetic aperture sonar technologies owing to the nature of longitudinal or compressive wave propagation in the surrounding acoustic medium. The system's transceiver is a quasi mono-static microphone and audio speaker pair mounted on a rail 5meters in length. Received data sampling rate is 80 kHz with a 2- 15 kHz Linear Frequency Modulated (LFM) chirp, with a pulse repetition frequency (PRF) of 10 Hz and an inter-pulse period (IPP) of 50 milliseconds. Targets are positioned within the acoustic scene at slant range of two to ten meters on grass, dirt or gravel surfaces, and with and without intervening metallic chain link fencing. Acoustic image reconstruction results in means for literal interpretation and quantifiable analyses. A rudimentary technique characterizes acoustic scatter at the ground surfaces. Targets within the acoustic scene are first digitally spotlighted and further processed, providing frequency and aspect angle dependent signature information.

  14. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2001-01-31

    During this phase of the project the research team concentrated on acquisition of acoustic emission data from the high porosity rock samples. The initial experiments indicated that the acoustic emission activity from high porosity Danian chalk were of a very low amplitude. Even though the sample underwent yielding and significant plastic deformation the sample did not generate significant AE activity. This was somewhat surprising. These initial results call into question the validity of attempting to locate AE activity in this weak rock type. As a result the testing program was slightly altered to include measuring the acoustic emission activity from many of the rock types listed in the research program. The preliminary experimental results indicate that AE activity in the sandstones is much higher than in the carbonate rocks (i.e., the chalks and limestones). This observation may be particularly important for planning microseismic imaging of reservoir rocks in the field environment. The preliminary results suggest that microseismic imaging of reservoir rock from acoustic emission activity generated from matrix deformation (during compaction and subsidence) would be extremely difficult to accomplish.

  15. Acoustic Reciprocity of Spatial Coherence in Ultrasound Imaging

    PubMed Central

    Bottenus, Nick; Üstüner, Kutay F.

    2015-01-01

    A conventional ultrasound image is formed by transmitting a focused wave into tissue, time-shifting the backscattered echoes received on an array transducer and summing the resulting signals. The van Cittert-Zernike theorem predicts a particular similarity, or coherence, of these focused signals across the receiving array. Many groups have used an estimate of the coherence to augment or replace the B-mode image in an effort to suppress noise and stationary clutter echo signals, but this measurement requires access to individual receive channel data. Most clinical systems have efficient pipelines for producing focused and summed RF data without any direct way to individually address the receive channels. We describe a method for performing coherence measurements that is more accessible for a wide range of coherence-based imaging. The reciprocity of the transmit and receive apertures in the context of coherence is derived and equivalence of the coherence function is validated experimentally using a research scanner. The proposed method is implemented on a Siemens ACUSON SC2000™ultrasound system and in vivo short-lag spatial coherence imaging is demonstrated using only summed RF data. The components beyond the acquisition hardware and beamformer necessary to produce a real-time ultrasound coherence imaging system are discussed. PMID:25965679

  16. Three-dimensional ghost imaging using acoustic transducer

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Guo, Shuxu; Guan, Jian; Cao, Junsheng; Gao, Fengli

    2016-06-01

    We propose a novel three-dimensional (3D) ghost imaging method using unfocused ultrasonic transducer, where the transducer is used as the bucket detector to collect the total photoacoustic signal intensity from spherical surfaces with different radius circling the transducer. This collected signal is a time sequence corresponding to the optic absorption information on the spherical surfaces, and the values at the same moments in all the sequences are used as the bucket signals to restore the corresponding spherical images, which are assembled as the object 3D reconstruction. Numerical experiments show this method can effectively accomplish the 3D reconstruction and by adding up each sequence on time domain as a bucket signal it can also realize two dimensional (2D) ghost imaging. The influence of the measurement times on the 3D and 2D reconstruction is analyzed with Peak Signal to Noise Ratio (PSNR) as the yardstick, and the transducer as a bucket detector is also discussed.

  17. Automated detection framework of the calcified plaque with acoustic shadowing in IVUS images.

    PubMed

    Gao, Zhifan; Guo, Wei; Liu, Xin; Huang, Wenhua; Zhang, Heye; Tan, Ning; Hau, William Kongto; Zhang, Yuan-Ting; Liu, Huafeng

    2014-01-01

    Intravascular Ultrasound (IVUS) is one ultrasonic imaging technology to acquire vascular cross-sectional images for the visualization of the inner vessel structure. This technique has been widely used for the diagnosis and treatment of coronary artery diseases. The detection of the calcified plaque with acoustic shadowing in IVUS images plays a vital role in the quantitative analysis of atheromatous plaques. The conventional method of the calcium detection is manual drawing by the doctors. However, it is very time-consuming, and with high inter-observer and intra-observer variability between different doctors. Therefore, the computer-aided detection of the calcified plaque is highly desired. In this paper, an automated method is proposed to detect the calcified plaque with acoustic shadowing in IVUS images by the Rayleigh mixture model, the Markov random field, the graph searching method and the prior knowledge about the calcified plaque. The performance of our method was evaluated over 996 in-vivo IVUS images acquired from eight patients, and the detected calcified plaques are compared with manually detected calcified plaques by one cardiology doctor. The experimental results are quantitatively analyzed separately by three evaluation methods, the test of the sensitivity and specificity, the linear regression and the Bland-Altman analysis. The first method is used to evaluate the ability to distinguish between IVUS images with and without the calcified plaque, and the latter two methods can respectively measure the correlation and the agreement between our results and manual drawing results for locating the calcified plaque in the IVUS image. High sensitivity (94.68%) and specificity (95.82%), good correlation and agreement (>96.82% results fall within the 95% confidence interval in the Student t-test) demonstrate the effectiveness of the proposed method in the detection of the calcified plaque with acoustic shadowing in IVUS images. PMID:25372784

  18. Guided Wave Delamination Detection and Quantification With Wavefield Data Analysis

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Campbell Leckey, Cara A.; Seebo, Jeffrey P.; Yu, Lingyu

    2014-01-01

    Unexpected damage can occur in aerospace composites due to impact events or material stress during off-nominal loading events. In particular, laminated composites are susceptible to delamination damage due to weak transverse tensile and inter-laminar shear strengths. Developments of reliable and quantitative techniques to detect delamination damage in laminated composites are imperative for safe and functional optimally-designed next-generation composite structures. In this paper, we investigate guided wave interactions with delamination damage and develop quantification algorithms by using wavefield data analysis. The trapped guided waves in the delamination region are observed from the wavefield data and further quantitatively interpreted by using different wavenumber analysis methods. The frequency-wavenumber representation of the wavefield shows that new wavenumbers are present and correlate to trapped waves in the damage region. These new wavenumbers are used to detect and quantify the delamination damage through the wavenumber analysis, which can show how the wavenumber changes as a function of wave propagation distance. The location and spatial duration of the new wavenumbers can be identified, providing a useful means not only for detecting the presence of delamination damage but also allowing for estimation of the delamination size. Our method has been applied to detect and quantify real delamination damage with complex geometry (grown using a quasi-static indentation technique). The detection and quantification results show the location, size, and shape of the delamination damage.

  19. Near-Field Imaging with Sound: An Acoustic STM Model

    ERIC Educational Resources Information Center

    Euler, Manfred

    2012-01-01

    The invention of scanning tunneling microscopy (STM) 30 years ago opened up a visual window to the nano-world and sparked off a bunch of new methods for investigating and controlling matter and its transformations at the atomic and molecular level. However, an adequate theoretical understanding of the method is demanding; STM images can be…

  20. HF Doppler Acoustic Imaging of the Ocean Surface and Interior

    NASA Astrophysics Data System (ADS)

    Pinkel, Robert; Smith, Jerome A.

    2004-11-01

    HF phased array Doppler sonar represents a new tool for obtaining Three-dimensional (r,q,t) images of the oceanic surface and interior velocity field. While the capabilities of the approach are unique, the design constraints are also unusual. Examples of both are presented in this work.

  1. Observations of Brine Pool Surface Characteristics and Internal Structure Through Remote Acoustic and Structured Light Imaging

    NASA Astrophysics Data System (ADS)

    Smart, C.; Roman, C.; Michel, A.; Wankel, S. D.

    2015-12-01

    Observations and analysis of the surface characteristics and internal structure of deep-sea brine pools are currently limited to discrete in-situ observations. Complementary acoustic and structured light imaging sensors mounted on a remotely operated vehicle (ROV) have demonstrated the ability systematically detect variations in surface characteristics of a brine pool, reveal internal stratification and detect areas of active hydrocarbon activity. The presented visual and acoustic sensors combined with a stereo camera pair are mounted on the 4000m rated ROV Hercules (Ocean Exploration Trust). These three independent sensors operate simultaneously from a typical 3m altitude resulting in visual and bathymetric maps with sub-centimeter resolution. Applying this imaging technology to 2014 and 2015 brine pool surveys in the Gulf of Mexico revealed acoustic and visual anomalies due to the density changes inherent in the brine. Such distinct changes in acoustic impedance allowed the high frequency 1350KHz multibeam sonar to detect multiple interfaces. For instance, distinct acoustic reflections were observed at 3m and 5.5m below the vehicle. Subsequent verification using a CDT and lead line indicated the acoustic return from the brine surface was the signal at 3m, while a thicker muddy and more saline interface occurred at 5.5m, the bottom of the brine pool was not located but is assumed to be deeper than 15m. The multibeam is also capable of remotely detecting emitted gas bubbles within the brine pool, indicative of active hydrocarbon seeps. Bubbles associated with these seeps were not consistently visible above the brine while using the HD camera on the ROV. Additionally, while imaging the surface of brine pool the structured light sheet laser became diffuse, refracting across the main interface. Analysis of this refraction combined with varying acoustic returns allow for systematic and remote detection of the density, stratification and activity levels within and

  2. Tunable caustic phenomena in electron wavefields.

    PubMed

    Tavabi, Amir Hossein; Migunov, Vadim; Dwyer, Christian; Dunin-Borkowski, Rafal E; Pozzi, Giulio

    2015-10-01

    Novel caustic phenomena, which contain fold, butterfly and elliptic umbilic catastrophes, are observed in defocused images of two approximately collinear oppositely biased metallic tips in a transmission electron microscope. The observed patterns depend sensitively on defocus, on the applied voltage between the tips and on their separation and lateral offset. Their main features are interpreted on the basis of a projected electrostatic potential model for the electron-optical phase shift. PMID:26069930

  3. Underwater Acoustic Matched Field Imaging Based on Compressed Sensing

    PubMed Central

    Yan, Huichen; Xu, Jia; Long, Teng; Zhang, Xudong

    2015-01-01

    Matched field processing (MFP) is an effective method for underwater target imaging and localizing, but its performance is not guaranteed due to the nonuniqueness and instability problems caused by the underdetermined essence of MFP. By exploiting the sparsity of the targets in an imaging area, this paper proposes a compressive sensing MFP (CS-MFP) model from wave propagation theory by using randomly deployed sensors. In addition, the model’s recovery performance is investigated by exploring the lower bounds of the coherence parameter of the CS dictionary. Furthermore, this paper analyzes the robustness of CS-MFP with respect to the displacement of the sensors. Subsequently, a coherence-excluding coherence optimized orthogonal matching pursuit (CCOOMP) algorithm is proposed to overcome the high coherent dictionary problem in special cases. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed CS-MFP method. PMID:26457708

  4. Underwater Acoustic Matched Field Imaging Based on Compressed Sensing.

    PubMed

    Yan, Huichen; Xu, Jia; Long, Teng; Zhang, Xudong

    2015-01-01

    Matched field processing (MFP) is an effective method for underwater target imaging and localizing, but its performance is not guaranteed due to the nonuniqueness and instability problems caused by the underdetermined essence of MFP. By exploiting the sparsity of the targets in an imaging area, this paper proposes a compressive sensing MFP (CS-MFP) model from wave propagation theory by using randomly deployed sensors. In addition, the model's recovery performance is investigated by exploring the lower bounds of the coherence parameter of the CS dictionary. Furthermore, this paper analyzes the robustness of CS-MFP with respect to the displacement of the sensors. Subsequently, a coherence-excluding coherence optimized orthogonal matching pursuit (CCOOMP) algorithm is proposed to overcome the high coherent dictionary problem in special cases. Finally, some numerical experiments are provided to demonstrate the effectiveness of the proposed CS-MFP method. PMID:26457708

  5. Three-Dimensional Acoustic Tissue Model: A Computational Tissue Phantom for Image Analyses

    NASA Astrophysics Data System (ADS)

    Mamou, J.; Oelze, M. L.; O'Brien, W. D.; Zachary, J. F.

    A novel methodology to obtain three-dimensional (3D) acoustic tissue models (3DATMs) is introduced. 3DATMs can be used as computational tools for ultrasonic imaging algorithm development and analysis. In particular, 3D models of biological structures can provide great benefit to better understand fundamentally how ultrasonic waves interact with biological materials. As an example, such models were used to generate ultrasonic images that characterize tumor tissue microstructures. 3DATMs can be used to evaluate a variety of tissue types. Typically, excised tissue is fixed, embedded, serially sectioned, and stained. The stained sections are digitally imaged (24-bit bitmap) with light microscopy. Contrast of each stained section is equalized and an automated registration algorithm aligns consecutive sections. The normalized mutual information is used as a similarity measure, and simplex optimization is conducted to find the best alignment. Both rigid and non-rigid registrations are performed. During tissue preparation, some sections are generally lost; thus, interpolation prior to 3D reconstruction is performed. Interpolation is conducted after registration using cubic Hermite polynoms. The registered (with interpolated) sections yield a 3D histologic volume (3DHV). Acoustic properties are then assigned to each tissue constituent of the 3DHV to obtain the 3DATMs. As an example, a 3D acoustic impedance tissue model (3DZM) was obtained for a solid breast tumor (EHS mouse sarcoma) and used to estimate ultrasonic scatterer size. The 3DZM results yielded an effective scatterer size of 32.9 (±6.1) μm. Ultrasonic backscatter measurements conducted on the same tumor tissue in vivo yielded an effective scatterer size of 33 (±8) μm. This good agreement shows that 3DATMs may be a powerful modeling tool for acoustic imaging applications

  6. A magnetic resonance imaging study on the articulatory and acoustic speech parameters of Malay vowels

    PubMed Central

    2014-01-01

    The phonetic properties of six Malay vowels are investigated using magnetic resonance imaging (MRI) to visualize the vocal tract in order to obtain dynamic articulatory parameters during speech production. To resolve image blurring due to the tongue movement during the scanning process, a method based on active contour extraction is used to track tongue contours. The proposed method efficiently tracks tongue contours despite the partial blurring of MRI images. Consequently, the articulatory parameters that are effectively measured as tongue movement is observed, and the specific shape of the tongue and its position for all six uttered Malay vowels are determined. Speech rehabilitation procedure demands some kind of visual perceivable prototype of speech articulation. To investigate the validity of the measured articulatory parameters based on acoustic theory of speech production, an acoustic analysis based on the uttered vowels by subjects has been performed. As the acoustic speech and articulatory parameters of uttered speech were examined, a correlation between formant frequencies and articulatory parameters was observed. The experiments reported a positive correlation between the constriction location of the tongue body and the first formant frequency, as well as a negative correlation between the constriction location of the tongue tip and the second formant frequency. The results demonstrate that the proposed method is an effective tool for the dynamic study of speech production. PMID:25060583

  7. Frequency-space prediction filtering for acoustic clutter and random noise attenuation in ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Shin, Junseob; Huang, Lianjie

    2016-04-01

    Frequency-space prediction filtering (FXPF), also known as FX deconvolution, is a technique originally developed for random noise attenuation in seismic imaging. FXPF attempts to reduce random noise in seismic data by modeling only real signals that appear as linear or quasilinear events in the aperture domain. In medical ultrasound imaging, channel radio frequency (RF) signals from the main lobe appear as horizontal events after receive delays are applied while acoustic clutter signals from off-axis scatterers and electronic noise do not. Therefore, FXPF is suitable for preserving only the main-lobe signals and attenuating the unwanted contributions from clutter and random noise in medical ultrasound imaging. We adapt FXPF to ultrasound imaging, and evaluate its performance using simulated data sets from a point target and an anechoic cyst. Our simulation results show that using only 5 iterations of FXPF achieves contrast-to-noise ratio (CNR) improvements of 67 % in a simulated noise-free anechoic cyst and 228 % in a simulated anechoic cyst contaminated with random noise of 15 dB signal-to-noise ratio (SNR). Our findings suggest that ultrasound imaging with FXPF attenuates contributions from both acoustic clutter and random noise and therefore, FXPF has great potential to improve ultrasound image contrast for better visualization of important anatomical structures and detection of diseased conditions.

  8. Acoustic radiation pressure: A 'phase contrast' agent for x-ray phase contrast imaging

    SciTech Connect

    Bailat, Claude J.; Hamilton, Theron J.; Rose-Petruck, Christoph; Diebold, Gerald J.

    2004-11-08

    We show that the radiation pressure exerted by a beam of ultrasound can be used for contrast enhancement in high-resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. The potential of the method is demonstrated by imaging microscopic tumor phantoms embedded into tissue with a thickness typically presented in mammography. The detection limit of micrometer size masses exceeds the resolution of currently available mammography imaging systems. The directionality of the acoustic radiation force and its localization in space permits the imaging of ultrasound-selected tissue volumes. The results presented here suggest that the method may permit the detection of tumors in soft tissue in their early stage of development.

  9. Acoustic property reconstruction of a pygmy sperm whale (Kogia breviceps) forehead based on computed tomography imaging.

    PubMed

    Song, Zhongchang; Xu, Xiao; Dong, Jianchen; Xing, Luru; Zhang, Meng; Liu, Xuecheng; Zhang, Yu; Li, Songhai; Berggren, Per

    2015-11-01

    Computed tomography (CT) imaging and sound experimental measurements were used to reconstruct the acoustic properties (density, velocity, and impedance) of the forehead tissues of a deceased pygmy sperm whale (Kogia breviceps). The forehead was segmented along the body axis and sectioned into cross section slices, which were further cut into sample pieces for measurements. Hounsfield units (HUs) of the corresponding measured pieces were obtained from CT scans, and regression analyses were conducted to investigate the linear relationships between the tissues' HUs and velocity, and HUs and density. The distributions of the acoustic properties of the head at axial, coronal, and sagittal cross sections were reconstructed, revealing that the nasal passage system was asymmetric and the cornucopia-shaped spermaceti organ was in the right nasal passage, surrounded by tissues and airsacs. A distinct dense theca was discovered in the posterior-dorsal area of the melon, which was characterized by low velocity in the inner core and high velocity in the outer region. Statistical analyses revealed significant differences in density, velocity, and acoustic impedance between all four structures, melon, spermaceti organ, muscle, and connective tissue (p < 0.001). The obtained acoustic properties of the forehead tissues provide important information for understanding the species' bioacoustic characteristics. PMID:26627786

  10. Military jet noise source imaging using multisource statistically optimized near-field acoustical holography.

    PubMed

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M

    2016-04-01

    The identification of acoustic sources is critical to targeted noise reduction efforts for jets on high-performance tactical aircraft. This paper describes the imaging of acoustic sources from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated source location; sources farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped source regions, which is a phenomenon relatively recently reported for full-scale jets. PMID:27106340

  11. Propagation of large-wavevector acoustic phonons new perspectives from phonon imaging

    NASA Astrophysics Data System (ADS)

    Wolfe, James P.

    Within the last decade a number of attempts have been made to observe the ballistic propagation of large wavevector acoustic phonons in crystals at low temperatures. Time-of-flight heat-pulse methods have difficulty in distinguishing between scattered phonons and ballistic phonons which travel dispersively at subsonic velocities. Fortunately, ballistic phonons can be identified by their highly anisotropic flux, which is observed by phonon imaging techniques. In this paper, several types of phonon imaging experiments are described which reveal the dispersive propagation of large-wavevector phonons and expose interesting details of the phonon scattering processes.

  12. A comparison of traffic estimates of nocturnal flying animals using radar, thermal imaging, and acoustic recording.

    PubMed

    Horton, Kyle G; Shriver, W Gregory; Buler, Jeffrey J

    2015-03-01

    There are several remote-sensing tools readily available for the study of nocturnally flying animals (e.g., migrating birds), each possessing unique measurement biases. We used three tools (weather surveillance radar, thermal infrared camera, and acoustic recorder) to measure temporal and spatial patterns of nocturnal traffic estimates of flying animals during the spring and fall of 2011 and 2012 in Lewes, Delaware, USA. Our objective was to compare measures among different technologies to better understand their animal detection biases. For radar and thermal imaging, the greatest observed traffic rate tended to occur at, or shortly after, evening twilight, whereas for the acoustic recorder, peak bird flight-calling activity was observed just prior to morning twilight. Comparing traffic rates during the night for all seasons, we found that mean nightly correlations between acoustics and the other two tools were weakly correlated (thermal infrared camera and acoustics, r = 0.004 ± 0.04 SE, n = 100 nights; radar and acoustics, r = 0.14 ± 0.04 SE, n = 101 nights), but highly variable on an individual nightly basis (range = -0.84 to 0.92, range = -0.73 to 0.94). The mean nightly correlations between traffic rates estimated by radar and by thermal infrared camera during the night were more strongly positively correlated (r = 0.39 ± 0.04 SE, n = 125 nights), but also were highly variable for individual nights (range = -0.76 to 0.98). Through comparison with radar data among numerous height intervals, we determined that flying animal height above the ground influenced thermal imaging positively and flight call detections negatively. Moreover, thermal imaging detections decreased with the presence of cloud cover and increased with mean ground flight speed of animals, whereas acoustic detections showed no relationship with cloud cover presence but did decrease with increased flight speed. We found sampling methods to be positively correlated when comparing mean nightly

  13. The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization.

    PubMed

    Allen, Jason D; Ham, Katherine L; Dumont, Douglas M; Sileshi, Bantayehu; Trahey, Gregg E; Dahl, Jeremy J

    2011-08-01

    Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50-69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability. PMID:21447606

  14. Microstructure Imaging Using Frequency Spectrum Spatially Resolved Acoustic Spectroscopy F-Sras

    NASA Astrophysics Data System (ADS)

    Sharples, S. D.; Li, W.; Clark, M.; Somekh, M. G.

    2010-02-01

    Material microstructure can have a profound effect on the mechanical properties of a component, such as strength and resistance to creep and fatigue. SRAS—spatially resolved acoustic spectroscopy—is a laser ultrasonic technique which can image microstructure using highly localized surface acoustic wave (SAW) velocity as a contrast mechanism, as this is sensitive to crystallographic orientation. The technique is noncontact, nondestructive, rapid, can be used on large components, and is highly tolerant of acoustic aberrations. Previously, the SRAS technique has been demonstrated using a fixed frequency excitation laser and a variable grating period (к-vector) to determine the most efficiently generated SAWs, and hence the velocity. Here, we demonstrate an implementation which uses a fixed grating period with a broadband laser excitation source. The velocity is determined by analyzing the measured frequency spectrum. Experimental results using this "frequency spectrum SRAS" (f-SRAS) method are presented. Images of microstructure on an industrially relevant material are compared to those obtained using the previous SRAS method ("k-SRAS"), excellent agreement is observed. Moreover, f-SRAS is much simpler and potentially much more rapid than k-SRAS as the velocity can be determined at each sample point in one single laser shot, rather than scanning the grating period.

  15. Eigenfunction analysis of stochastic backscatter for characterization of acoustic aberration in medical ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Varslot, Trond; Krogstad, Harald; Mo, Eirik; Angelsen, Bjørn A.

    2004-06-01

    Presented here is a characterization of aberration in medical ultrasound imaging. The characterization is optimal in the sense of maximizing the expected energy in a modified beamformer output of the received acoustic backscatter. Aberration correction based on this characterization takes the form of an aberration correction filter. The situation considered is frequently found in applications when imaging organs through a body wall: aberration is introduced in a layer close to the transducer, and acoustic backscatter from a scattering region behind the body wall is measured at the transducer surface. The scattering region consists of scatterers randomly distributed with very short correlation length compared to the acoustic wavelength of the transmit pulse. The scatterer distribution is therefore assumed to be δ correlated. This paper shows how maximizing the expected energy in a modified beamformer output signal naturally leads to eigenfunctions of a Fredholm integral operator, where the associated kernel function is a spatial correlation function of the received stochastic signal. Aberration characterization and aberration correction are presented for simulated data constructed to mimic aberration introduced by the abdominal wall. The results compare well with what is obtainable using data from a simulated point source.

  16. Bond-selective photoacoustic imaging by converting molecular vibration into acoustic waves

    PubMed Central

    Hui, Jie; Li, Rui; Phillips, Evan H.; Goergen, Craig J.; Sturek, Michael; Cheng, Ji-Xin

    2016-01-01

    The quantized vibration of chemical bonds provides a way of detecting specific molecules in a complex tissue environment. Unlike pure optical methods, for which imaging depth is limited to a few hundred micrometers by significant optical scattering, photoacoustic detection of vibrational absorption breaks through the optical diffusion limit by taking advantage of diffused photons and weak acoustic scattering. Key features of this method include both high scalability of imaging depth from a few millimeters to a few centimeters and chemical bond selectivity as a novel contrast mechanism for photoacoustic imaging. Its biomedical applications spans detection of white matter loss and regeneration, assessment of breast tumor margins, and diagnosis of vulnerable atherosclerotic plaques. This review provides an overview of the recent advances made in vibration-based photoacoustic imaging and various biomedical applications enabled by this new technology. PMID:27069873

  17. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-11-18

    During the sixth quarter of this research project the research team developed a method and the experimental procedures for acquiring the data needed for ultrasonic tomography of rock core samples under triaxial stress conditions as outlined in Task 10. Traditional triaxial compression experiments, where compressional and shear wave velocities are measured, provide little or no information about the internal spatial distribution of mechanical damage within the sample. The velocities measured between platen-to-platen or sensor-to-sensor reflects an averaging of all the velocities occurring along that particular raypath across the boundaries of the rock. The research team is attempting to develop and refine a laboratory equivalent of seismic tomography for use on rock samples deformed under triaxial stress conditions. Seismic tomography, utilized for example in crosswell tomography, allows an imaging of the velocities within a discrete zone within the rock. Ultrasonic or acoustic tomography is essentially the extension of that field technology applied to rock samples deforming in the laboratory at high pressures. This report outlines the technical steps and procedures for developing this technology for use on weak, soft chalk samples. Laboratory tests indicate that the chalk samples exhibit major changes in compressional and shear wave velocities during compaction. Since chalk is the rock type responsible for the severe subsidence and compaction in the North Sea it was selected for the first efforts at tomographic imaging of soft rocks. Field evidence from the North Sea suggests that compaction, which has resulted in over 30 feet of subsidence to date, is heterogeneously distributed within the reservoir. The research team will attempt to image this very process in chalk samples. The initial tomographic studies (Scott et al., 1994a,b; 1998) were accomplished on well cemented, competent rocks such as Berea sandstone. The extension of the technology to weaker samples is

  18. Acoustic Image Models for Obstacle Avoidance with Forward-Looking Sonar

    NASA Astrophysics Data System (ADS)

    Masek, T.; Kölsch, M.

    Long-range forward-looking sonars (FLS) have recently been deployed in autonomous unmanned vehicles (AUV). We present models for various features in acoustic images, with the goal of using this sensor for altitude maintenance, obstacle detection and obstacle avoidance. First, we model the backscatter and FLS noise as pixel-based, spatially-varying intensity distributions. Experiments show that these models predict noise with an accuracy of over 98%. Next, the presence of acoustic noise from two other sources including a modem is reliably detected with a template-based filter and a threshold learned from training data. Lastly, the ocean floor location and orientation is estimated with a gradient-descent method using a site-independent template, yielding sufficiently accurate results in 95% of the frames. Temporal information is expected to further improve the performance.

  19. Acoustic imaging of the Mediterranean water outflowing through the Strait of Gibraltar

    NASA Astrophysics Data System (ADS)

    Biescas Gorriz, Berta; Carniel, Sandro; Sallarès, Valentí; Rodriguez Ranero, Cesar

    2016-04-01

    Acoustic imaging of the Mediterranean water outflowing through the Strait of Gibraltar Berta Biescas (1), Sandro Carniel (2) , Valentí Sallarès (3) and Cesar R. Ranero(3) (1) Istituto di Scienze Marine, CNR, Bologna, Italy (2) Istituto di Scienze Marine, CNR, Venice, Italy (3) Institut de Ciències del Mar, CSIC, Barcelona, Spain Acoustic reflectivity acquired with multichannel seismic reflection (MCS) systems allow to detect and explore the thermohaline structure in the ocean with vertical and lateral resolutions in the order of 10 m, covering hundreds of kilometers in the lateral dimension and the full-depth water column. In this work we present a MCS 2D profile that crosses the Strait of Gibraltar, from the Alboran Sea to the internal Gulf of Cadiz (NE Atlantic Ocean). The MCS data was acquired during the Topomed-Gassis Cruise (European Science Foundation TopoEurope), which was carried out on board of the Spanish R/V Sarmiento de Gamboa in October 2011. The strong thermohaline contrast between the Mediterranean water and the Atlantic water, characterizes this area and allows to visualize, with unprecedented resolution, the acoustic reflectivity associated to the dense flow of the Mediterranean water outflowing through the prominent slope of the Strait of Gibraltar. During the first kilometers, the dense flow drops attached to the continental slope until it reaches the buoyancy depth at 700 m. Then, it detaches from the sea floor and continues flowing towards the Atlantic Ocean, occupying the layer at 700-1500 m deep and developing clear staircase layers. The reflectivity images display near seabed reflections that could well correspond to turbidity layers. The XBT data acquired coincident in time and space with the MCS data will help us in the interpretation and analysis of the acoustic data.

  20. Imaging living cells with a combined high-resolution multi-photon-acoustic microscope

    NASA Astrophysics Data System (ADS)

    Schenkl, Selma; Weiss, Eike; Stark, Martin; Stracke, Frank; Riemann, Iris; Lemor, Robert; König, Karsten

    2007-02-01

    With increasing demand for in-vivo observation of living cells, microscope techniques that do not need staining become more and more important. In this talk we present a combined multi-photon-acoustic microscope with the possibility to measure synchronously properties addressed by ultrasound and two-photon fluorescence. Ultrasound probes the local mechanical properties of a cell, while the high resolution image of the two-photon fluorescence delivers insight in cell morphology and activity. In the acoustic part of the microscope an ultrasound wave, with a frequency of GHz, is focused by an acoustic sapphire lens and detected by a piezo electric transducer assembled to the lens. The achieved lateral resolution is in the range of 1μm. Contrast in the images arises mainly from the local absorption of sound in the cells, related to properties, such as mass density, stiffness and viscose damping. Additionally acoustic microscopy can access the cell shape and the state of the cell membrane as it is a intrinsic volume scanning technique.The optical part bases on the emission of fluorescent biomolecules naturally present in cells (e.g. NAD(P)H, protophorphyrin IX, lipofuscin, melanin). The nonlinear effect of two-photon absorption provides a high lateral and axial resolution without the need of confocal detection. In addition, in the near-IR cell damages are drastically reduced in comparison to direct excitation in the visible or UV. Both methods can be considered as minimal invasive, as they relay on intrinsic contrast mechanisms and dispense with the need of staining. First results on living cells are presented and discussed.

  1. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-11-18

    During the seven quarter of the project the research team analyzed some of the acoustic velocity data and rock deformation data. The goal is to create a series of ''deformation-velocity maps'' which can outline the types of rock deformational mechanisms which can occur at high pressures and then associate those with specific compressional or shear wave velocity signatures. During this quarter, we began to analyze both the acoustical and deformational properties of the various rock types. Some of the preliminary velocity data from the Danian chalk will be presented in this report. This rock type was selected for the initial efforts as it will be used in the tomographic imaging study outlined in Task 10. This is one of the more important rock types in the study as the Danian chalk is thought to represent an excellent analog to the Ekofisk chalk that has caused so many problems in the North Sea. Some of the preliminary acoustic velocity data obtained during this phase of the project indicates that during pore collapse and compaction of this chalk, the acoustic velocities can change by as much as 200 m/s. Theoretically, this significant velocity change should be detectable during repeated successive 3-D seismic images. In addition, research continues with an analysis of the unconsolidated sand samples at high confining pressures obtained in Task 9. The analysis of the results indicate that sands with 10% volume of fines can undergo liquefaction at lower stress conditions than sand samples which do not have fines added. This liquefaction and/or sand flow is similar to ''shallow water'' flows observed during drilling in the offshore Gulf of Mexico.

  2. Voice assessment: Updates on perceptual, acoustic, aerodynamic, and endoscopic imaging methods

    PubMed Central

    Mehta, Daryush D.; Hillman, Robert E.

    2013-01-01

    Purpose of review This paper describes recent advances in perceptual, acoustic, aerodynamic, and endoscopic imaging methods for assessing voice production. Recent findings Perceptual assessment Speech-language pathologists are being encouraged to use the new CAPE-V inventory for auditory perceptual assessment of voice quality, and recent studies have provided new insights into listener reliability issues that have plagued subjective perceptual judgments of voice quality. Acoustic assessment Progress is being made on the development of algorithms that are more robust for analyzing disordered voices, including the capability to extract voice quality-related measures from running speech segments. Aerodynamic assessment New devices for measuring phonation threshold air pressures and air flows have the potential to serve as sensitive indices of glottal phonatory conditions, and recent developments in aeroacoustic theory may provide new insights into laryngeal sound production mechanisms. Endoscopic imaging The increased light sensitivity of new ultra high-speed color digital video processors is enabling high-quality endoscopic imaging of vocal fold tissue motion at unprecedented image capture rates, which promises to provide new insights into mechanisms of normal and disordered voice production. Summary Some of the recent research advances in voice quality assessment could be more readily adopted into clinical practice, while others will require further development. PMID:18475073

  3. Using numerical models and volume rendering to interpret acoustic imaging of hydrothermal flow

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Bennett, K.; Takle, J.; Rona, P. A.; Silver, D.

    2009-12-01

    Our acoustic imaging system will be installed onto the Neptune Canada observatory at the Main Endeavour Field, Juan de Fuca Ridge, which is a Ridge 2000 Integrated Study Site. Thereafter, 16-30 Gb of acoustic imaging data will be collected daily. We are developing a numerical model of merging plumes that will be used to guide expectations and volume rendering software that transforms volumetric acoustic data into photo-like images. Hydrothermal flow is modeled as a combination of merged point sources which can be configured in any geometry. The model stipulates the dissipation or dilution of the flow and uses potential fields and complex analysis to combine the entrainment fields produced by each source. The strengths of this model are (a) the ability to handle a variety of scales especially the small scale as the potential fields can be specified with an effectively infinite boundary condition, (b) the ability to handle line, circle and areal source configurations, and (c) the ability to handle both high temperature focused flow and low temperature diffuse flow. This model predicts the vertical and horizontal velocities and the spatial distribution of effluent from combined sources of variable strength in a steady ambient velocity field. To verify the accuracy of the model’s results, we compare the model predictions of plume centerlines for the merging of two relatively strong point sources with the acoustic imaging data collected at Clam Acres, Southwest Vent Field, EPR 21°N in 1990. The two chimneys are 3.5 m apart and the plumes emanating from their tops merge approximately 18 mab. The model is able to predict the height of merging and the bending of the centerlines. Merging is implicitly observed at Grotto Vent, Main Endeavour Field, in our VIP 2000 data from July 2000: although there are at least 5 vigorous black smokers only a single plume is discernable in the acoustic imaging data. Furthermore, the observed Doppler velocity data increases with height

  4. Sensing the delivery and endocytosis of nanoparticles using magneto-photo-acoustic imaging

    PubMed Central

    Qu, M.; Mehrmohammadi, M.; Emelianov, S.Y.

    2015-01-01

    Many biomedical applications necessitate a targeted intracellular delivery of the nanomaterial to specific cells. Therefore, a non-invasive and reliable imaging tool is required to detect both the delivery and cellular endocytosis of the nanoparticles. Herein, we demonstrate that magneto-photo-acoustic (MPA) imaging can be used to monitor the delivery and to identify endocytosis of magnetic and optically absorbing nanoparticles. The relationship between photoacoustic (PA) and magneto-motive ultrasound (MMUS) signals from the in vitro samples were analyzed to identify the delivery and endocytosis of nanoparticles. The results indicated that during the delivery of nanoparticles to the vicinity of the cells, both PA and MMUS signals are almost linearly proportional. However, accumulation of nanoparticles within the cells leads to nonlinear MMUS-PA relationship, due to non-linear MMUS signal amplification. Therefore, through longitudinal MPA imaging, it is possible to monitor the delivery of nanoparticles and identify the endocytosis of the nanoparticles by living cells. PMID:26640773

  5. Ultrasound-Stimulated Acoustic Emission in Thermal Image-Guided HIFU Therapy: A Phantom Study

    SciTech Connect

    Jiang, C. P.; Lin, W. T.; Chen, W. S.

    2006-05-08

    Magnetic resonance image (MRI) is a promising monitoring tool for non-invasive real-time thermal guidance in high intensity focused ultrasound (HIFU) during thermal ablation surgery. However, this approach has two main drawbacks: 1) majority of components need to be redesigned to be MR compatible in order to avoid effecting MR images, and 2) the cost of operating MRI facilities is high. Alternately, ultrasound-stimulated acoustic emission (USAE) method has been applied for detecting thermal variations in tissues. An optical transparent phantom, made from polyacrylamide, containing thermal sensitive indicator protein (Bovine Serum Albumin), was prepared for observing the HIFU-induced denaturalization. A thermal-couple was set up for validation of temperature distribution. Experimental results show that thermal image can be captured clearly under stationary conditions.

  6. Modeling scattering from azimuthally symmetric bathymetric features using wavefield superposition.

    PubMed

    Fawcett, John A

    2007-12-01

    In this paper, an approach for modeling the scattering from azimuthally symmetric bathymetric features is described. These features are useful models for small mounds and indentations on the seafloor at high frequencies and seamounts, shoals, and basins at low frequencies. A bathymetric feature can be considered as a compact closed region, with the same sound speed and density as one of the surrounding media. Using this approach, a number of numerical methods appropriate for a partially buried target or facet problem can be applied. This paper considers the use of wavefield superposition and because of the azimuthal symmetry, the three-dimensional solution to the scattering problem can be expressed as a Fourier sum of solutions to a set of two-dimensional scattering problems. In the case where the surrounding two half spaces have only a density contrast, a semianalytic coupled mode solution is derived. This provides a benchmark solution to scattering from a class of penetrable hemispherical bosses or indentations. The details and problems of the numerical implementation of the wavefield superposition method are described. Example computations using the method for a simple scattering feature on a seabed are presented for a wide band of frequencies. PMID:18247740

  7. Breaking the acoustic diffraction limit via nonlinear effect and thermal confinement for potential deep-tissue high-resolution imaging

    PubMed Central

    Yuan, Baohong; Pei, Yanbo; Kandukuri, Jayanth

    2013-01-01

    Our recently developed ultrasound-switchable fluorescence (USF) imaging technique showed that it was feasible to conduct high-resolution fluorescence imaging in a centimeter-deep turbid medium. Because the spatial resolution of this technique highly depends on the ultrasound-induced temperature focal size (UTFS), minimization of UTFS becomes important for further improving the spatial resolution USF technique. In this study, we found that UTFS can be significantly reduced below the diffraction-limited acoustic intensity focal size via nonlinear acoustic effects and thermal confinement by appropriately controlling ultrasound power and exposure time, which can be potentially used for deep-tissue high-resolution imaging. PMID:23479498

  8. Contribution of the supraglottic larynx to the vocal product: imaging and acoustic analysis

    NASA Astrophysics Data System (ADS)

    Gracco, L. Carol

    1996-04-01

    Horizontal supraglottic laryngectomy is a surgical procedure to remove a mass lesion located in the region of the pharynx superior to the true vocal folds. In contrast to full or partial laryngectomy, patients who undergo horizontal supraglottic laryngectomy often present with little or nor involvement to the true vocal folds. This population provides an opportunity to examine the acoustic consequences of altering the pharynx while sparing the laryngeal sound source. Acoustic and magnetic resonance imaging (MRI) data were acquired in a group of four patients before and after supraglottic laryngectomy. Acoustic measures included the identification of vocal tract resonances and the fundamental frequency of the vocal fold vibration. 3D reconstruction of the pharyngeal portion of each subjects' vocal tract were made from MRIs taken during phonation and volume measures were obtained. These measures reveal a variable, but often dramatic difference in the surgically-altered area of the pharynx and changes in the formant frequencies of the vowel/i/post surgically. In some cases the presence of the tumor created a deviation from the expected formant values pre-operatively with post-operative values approaching normal. Patients who also underwent radiation treatment post surgically tended to have greater constriction in the pharyngeal area of the vocal tract.

  9. Acoustic Property Reconstruction of a Neonate Yangtze Finless Porpoise's (Neophocaena asiaeorientalis) Head Based on CT Imaging

    PubMed Central

    Wei, Chong; Wang, Zhitao; Song, Zhongchang; Wang, Kexiong; Wang, Ding; Au, Whitlow W. L.; Zhang, Yu

    2015-01-01

    The reconstruction of the acoustic properties of a neonate finless porpoise’s head was performed using X-ray computed tomography (CT). The head of the deceased neonate porpoise was also segmented across the body axis and cut into slices. The averaged sound velocity and density were measured, and the Hounsfield units (HU) of the corresponding slices were obtained from computed tomography scanning. A regression analysis was employed to show the linear relationships between the Hounsfield unit and both sound velocity and density of samples. Furthermore, the CT imaging data were used to compare the HU value, sound velocity, density and acoustic characteristic impedance of the main tissues in the porpoise’s head. The results showed that the linear relationships between HU and both sound velocity and density were qualitatively consistent with previous studies on Indo-pacific humpback dolphins and Cuvier’s beaked whales. However, there was no significant increase of the sound velocity and acoustic impedance from the inner core to the outer layer in this neonate finless porpoise’s melon. PMID:25856588

  10. Acoustic property reconstruction of a neonate Yangtze finless porpoise's (Neophocaena asiaeorientalis) head based on CT imaging.

    PubMed

    Wei, Chong; Wang, Zhitao; Song, Zhongchang; Wang, Kexiong; Wang, Ding; Au, Whitlow W L; Zhang, Yu

    2015-01-01

    The reconstruction of the acoustic properties of a neonate finless porpoise's head was performed using X-ray computed tomography (CT). The head of the deceased neonate porpoise was also segmented across the body axis and cut into slices. The averaged sound velocity and density were measured, and the Hounsfield units (HU) of the corresponding slices were obtained from computed tomography scanning. A regression analysis was employed to show the linear relationships between the Hounsfield unit and both sound velocity and density of samples. Furthermore, the CT imaging data were used to compare the HU value, sound velocity, density and acoustic characteristic impedance of the main tissues in the porpoise's head. The results showed that the linear relationships between HU and both sound velocity and density were qualitatively consistent with previous studies on Indo-pacific humpback dolphins and Cuvier's beaked whales. However, there was no significant increase of the sound velocity and acoustic impedance from the inner core to the outer layer in this neonate finless porpoise's melon. PMID:25856588

  11. The concept of cyclic sound intensity and its application to acoustical imaging

    NASA Astrophysics Data System (ADS)

    Lafon, B.; Antoni, J.; Sidahmed, M.; Polac, L.

    2011-04-01

    This paper demonstrates how to take advantage of the cyclostationarity property of engine signals to define a new acoustical quantity, the cyclic sound intensity, which displays the instantaneous flux of acoustical energy in the angle-frequency domain during an average engine cycle. This quantity is attractive in that it possesses the ability of being instantaneous and averaged at the same time, thus reconciling two conflicting properties into a rigourous and unambiguous framework. Cyclic sound intensity is a rich concept with several original ramifications. Among other things, it returns a unique decomposition into instantaneous active and reactive parts. Associated to acoustical imaging techniques, it allows the construction of sound radiation movies that evolve within the engine cycle and whose each frame is a sound intensity map calculated at a specific time - or crankshaft angle - in the engine cycle. This enables the accurate localisation of sources in space, in frequency and in time (crankshaft angle). Furthermore, associated to cyclic Wiener filtering, this methodology makes it possible to decompose the overall radiated sound into several noise source contributions whose cyclic sound intensities can then be analysed independently.

  12. Imaging of transient surface acoustic waves by full-field photorefractive interferometry.

    PubMed

    Xiong, Jichuan; Xu, Xiaodong; Glorieux, Christ; Matsuda, Osamu; Cheng, Liping

    2015-05-01

    A stroboscopic full-field imaging technique based on photorefractive interferometry for the visualization of rapidly changing surface displacement fields by using of a standard charge-coupled device (CCD) camera is presented. The photorefractive buildup of the space charge field during and after probe laser pulses is simulated numerically. The resulting anisotropic diffraction upon the refractive index grating and the interference between the polarization-rotated diffracted reference beam and the transmitted signal beam are modeled theoretically. The method is experimentally demonstrated by full-field imaging of the propagation of photoacoustically generated surface acoustic waves with a temporal resolution of nanoseconds. The surface acoustic wave propagation in a 23 mm × 17 mm area on an aluminum plate was visualized with 520 × 696 pixels of the CCD sensor, yielding a spatial resolution of 33 μm. The short pulse duration (8 ns) of the probe laser yields the capability of imaging SAWs with frequencies up to 60 MHz. PMID:26026514

  13. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P. Oshkai; M. Geveci; D. Rockwell; M. Pollack

    2002-12-12

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of,these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  14. Investigating the emotional response to room acoustics: A functional magnetic resonance imaging study.

    PubMed

    Lawless, M S; Vigeant, M C

    2015-10-01

    While previous research has demonstrated the powerful influence of pleasant and unpleasant music on emotions, the present study utilizes functional magnetic resonance imaging (fMRI) to assess the positive and negative emotional responses as demonstrated in the brain when listening to music convolved with varying room acoustic conditions. During fMRI scans, subjects rated auralizations created in a simulated concert hall with varying reverberation times. The analysis detected activations in the dorsal striatum, a region associated with anticipation of reward, for two individuals for the highest rated stimulus, though no activations were found for regions associated with negative emotions in any subject. PMID:26520354

  15. Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.

    PubMed

    Park, Jinhyoung; Lee, Jungwoo; Lau, Sien Ting; Lee, Changyang; Huang, Ying; Lien, Ching-Ling; Kirk Shung, K

    2012-04-01

    Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2-10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells. This article thus presents a high-frequency coded excitation ARFI technique, with the ultimate goal of displaying elastic characteristics of cellular structures. Tissue mimicking phantoms and zebrafish embryos are imaged with a 100-MHz lithium niobate (LiNbO₃) transducer, by cross-correlating tracked RF echoes with the reference. The phantom results show that the contrast of ARFI image (14 dB) with coded excitation is better than that of the conventional ARFI image (9 dB). The depths of penetration are 2.6 and 2.2 mm, respectively. The stiffness data of the zebrafish demonstrate that the envelope is harder than the embryo region. The temporal displacement change at the embryo and the chorion is as large as 36 and 3.6 μm. Consequently, this high-frequency ARFI approach may serve as a remote palpation imaging tool that reveals viscoelastic properties of small biological samples. PMID:22101757

  16. Homogenization of Electromagnetic and Seismic Wavefields for Joint Inverse Modeling

    NASA Astrophysics Data System (ADS)

    Newman, G. A.; Commer, M.; Petrov, P.; Um, E. S.

    2011-12-01

    ) possibilities to image across multiple scale lengths, incorporating different types of geophysical data and attributes in the process. Important numerical details of 3D seismic wave field simulation in the Laplace-Fourier domain for both acoustic and elastic cases will also be discussed.

  17. Acoustic structure quantification by using ultrasound Nakagami imaging for assessing liver fibrosis

    PubMed Central

    Tsui, Po-Hsiang; Ho, Ming-Chih; Tai, Dar-In; Lin, Ying-Hsiu; Wang, Chiao-Yin; Ma, Hsiang-Yang

    2016-01-01

    Acoustic structure quantification (ASQ) is a recently developed technique widely used for detecting liver fibrosis. Ultrasound Nakagami parametric imaging based on the Nakagami distribution has been widely used to model echo amplitude distribution for tissue characterization. We explored the feasibility of using ultrasound Nakagami imaging as a model-based ASQ technique for assessing liver fibrosis. Standard ultrasound examinations were performed on 19 healthy volunteers and 91 patients with chronic hepatitis B and C (n = 110). Liver biopsy and ultrasound Nakagami imaging analysis were conducted to compare the METAVIR score and Nakagami parameter. The diagnostic value of ultrasound Nakagami imaging was evaluated using receiver operating characteristic (ROC) curves. The Nakagami parameter obtained through ultrasound Nakagami imaging decreased with an increase in the METAVIR score (p < 0.0001), representing an increase in the extent of pre-Rayleigh statistics for echo amplitude distribution. The area under the ROC curve (AUROC) was 0.88 for the diagnosis of any degree of fibrosis (≥F1), whereas it was 0.84, 0.69, and 0.67 for ≥F2, ≥F3, and ≥F4, respectively. Ultrasound Nakagami imaging is a model-based ASQ technique that can be beneficial for the clinical diagnosis of early liver fibrosis. PMID:27605260

  18. Acoustic structure quantification by using ultrasound Nakagami imaging for assessing liver fibrosis.

    PubMed

    Tsui, Po-Hsiang; Ho, Ming-Chih; Tai, Dar-In; Lin, Ying-Hsiu; Wang, Chiao-Yin; Ma, Hsiang-Yang

    2016-01-01

    Acoustic structure quantification (ASQ) is a recently developed technique widely used for detecting liver fibrosis. Ultrasound Nakagami parametric imaging based on the Nakagami distribution has been widely used to model echo amplitude distribution for tissue characterization. We explored the feasibility of using ultrasound Nakagami imaging as a model-based ASQ technique for assessing liver fibrosis. Standard ultrasound examinations were performed on 19 healthy volunteers and 91 patients with chronic hepatitis B and C (n = 110). Liver biopsy and ultrasound Nakagami imaging analysis were conducted to compare the METAVIR score and Nakagami parameter. The diagnostic value of ultrasound Nakagami imaging was evaluated using receiver operating characteristic (ROC) curves. The Nakagami parameter obtained through ultrasound Nakagami imaging decreased with an increase in the METAVIR score (p < 0.0001), representing an increase in the extent of pre-Rayleigh statistics for echo amplitude distribution. The area under the ROC curve (AUROC) was 0.88 for the diagnosis of any degree of fibrosis (≥F1), whereas it was 0.84, 0.69, and 0.67 for ≥F2, ≥F3, and ≥F4, respectively. Ultrasound Nakagami imaging is a model-based ASQ technique that can be beneficial for the clinical diagnosis of early liver fibrosis. PMID:27605260

  19. Acoustic quasi-holographic images of scattering by vertical cylinders from one-dimensional bistatic scans.

    PubMed

    Baik, Kyungmin; Dudley, Christopher; Marston, Philip L

    2011-12-01

    When synthetic aperture sonar (SAS) is used to image elastic targets in water, subtle features can be present in the images associated with the dynamical response of the target being viewed. In an effort to improve the understanding of such responses, as well as to explore alternative image processing methods, a laboratory-based system was developed in which targets were illuminated by a transient acoustic source, and bistatic responses were recorded by scanning a hydrophone along a rail system. Images were constructed using a relatively conventional bistatic SAS algorithm and were compared with images based on supersonic holography. The holographic method is a simplification of one previously used to view the time evolution of a target's response [Hefner and Marston, ARLO 2, 55-60 (2001)]. In the holographic method, the space-time evolution of the scattering was used to construct a two-dimensional image with cross range and time as coordinates. Various features for vertically hung cylindrical targets were interpreted using high frequency ray theory. This includes contributions from guided surface elastic waves, as well as transmitted-wave features and specular reflection. PMID:22225041

  20. Stress-Induced Fracturing of Reservoir Rocks: Acoustic Monitoring and μCT Image Analysis

    NASA Astrophysics Data System (ADS)

    Pradhan, Srutarshi; Stroisz, Anna M.; Fjær, Erling; Stenebråten, Jørn F.; Lund, Hans K.; Sønstebø, Eyvind F.

    2015-11-01

    Stress-induced fracturing in reservoir rocks is an important issue for the petroleum industry. While productivity can be enhanced by a controlled fracturing operation, it can trigger borehole instability problems by reactivating existing fractures/faults in a reservoir. However, safe fracturing can improve the quality of operations during CO2 storage, geothermal installation and gas production at and from the reservoir rocks. Therefore, understanding the fracturing behavior of different types of reservoir rocks is a basic need for planning field operations toward these activities. In our study, stress-induced fracturing of rock samples has been monitored by acoustic emission (AE) and post-experiment computer tomography (CT) scans. We have used hollow cylinder cores of sandstones and chalks, which are representatives of reservoir rocks. The fracture-triggering stress has been measured for different rocks and compared with theoretical estimates. The population of AE events shows the location of main fracture arms which is in a good agreement with post-test CT image analysis, and the fracture patterns inside the samples are visualized through 3D image reconstructions. The amplitudes and energies of acoustic events clearly indicate initiation and propagation of the main fractures. Time evolution of the radial strain measured in the fracturing tests will later be compared to model predictions of fracture size.

  1. Negative refraction and imaging of acoustic waves in a two-dimensional square chiral lattice structure

    NASA Astrophysics Data System (ADS)

    Zhao, Sheng-Dong; Wang, Yue-Sheng

    2016-05-01

    The negative refraction behavior and imaging effect for acoustic waves in a kind of two-dimensional square chiral lattice structure are studied in this paper. The unit cell of the proposed structure consists of four zigzag arms connected through a thin circular ring at the central part. The relation of the symmetry of the unit cell and the negative refraction phenomenon is investigated. Using the finite element method, we calculate the band structures and the equi-frequency surfaces of the system, and confirm the frequency range where the negative refraction is present. Due to the rotational symmetry of the unit cell, a phase difference is induced to the waves propagating from a point source through the structure to the other side. The phase difference is related to the width of the structure and the frequency of the source, so we can get a tunable deviated imaging. This kind of phenomenon is also demonstrated by the numerical simulation of two Gaussian beams that are symmetrical about the interface normal with the same incident angle, and the different negative refractive indexes are presented. Based on this special performance, a double-functional mirror-symmetrical slab is proposed for realizing acoustic focusing and beam separation. xml:lang="fr"

  2. Image formation and system analysis of a scanning tomographic acoustic microscope

    NASA Astrophysics Data System (ADS)

    Kent, Samuel Davis, III

    This dissertation focuses on research that has been conducted to implement an automated Scanning Tomographic Acoustic Microscope (STAM), and research that has been performed to increase the understanding of the performance characteristics of the STAM. STAM technology permits high resolution microscopy which yields important information on the internal structure and acoustic properties of thick specimens, provided that technology is utilized in a cohesive manner. Prior to the research conducted for this dissertation, only a proof-of-concept STAM had been developed; actual STAM imaging was difficult and impractical. This dissertation describes the hardware and software development that has led to the first automated STAM. It focuses on significant problems that were encountered and their solutions. Specifically, accurate data acquisition necessitated the development of special-purpose data acquisition hardware, rotational controls, frequency controls, and automation controls. Inaccuracies in the laser scanning hardware were identified as a significant source of reconstruction error. This error was removed by estimation and correction algorithms. Rotation of the specimen for multiple-angle tomography required the development of a noise-tolerant projection-pose estimation algorithm. An iterative technique for image enhancement is also presented. The resulting STAM system is evaluated to determine its performance characteristics. A component-wise resolution analysis is presented that specifies the resolution-limit in both range and cross-range. The dependency of reconstruction quality on accurate representation of the magnitude and phase of the detected wave fields is also provided.

  3. A novel imaging technique based on the spatial coherence of backscattered waves: demonstration in the presence of acoustical clutter

    NASA Astrophysics Data System (ADS)

    Dahl, Jeremy J.; Pinton, Gianmarco F.; Lediju, Muyinatu; Trahey, Gregg E.

    2011-03-01

    In the last 20 years, the number of suboptimal and inadequate ultrasound exams has increased. This trend has been linked to the increasing population of overweight and obese individuals. The primary causes of image degradation in these individuals are often attributed to phase aberration and clutter. Phase aberration degrades image quality by distorting the transmitted and received pressure waves, while clutter degrades image quality by introducing incoherent acoustical interference into the received pressure wavefront. Although significant research efforts have pursued the correction of image degradation due to phase aberration, few efforts have characterized or corrected image degradation due to clutter. We have developed a novel imaging technique that is capable of differentiating ultrasonic signals corrupted by acoustical interference. The technique, named short-lag spatial coherence (SLSC) imaging, is based on the spatial coherence of the received ultrasonic wavefront at small spatial distances across the transducer aperture. We demonstrate comparative B-mode and SLSC images using full-wave simulations that include the effects of clutter and show that SLSC imaging generates contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) that are significantly better than B-mode imaging under noise-free conditions. In the presence of noise, SLSC imaging significantly outperforms conventional B-mode imaging in all image quality metrics. We demonstrate the use of SLSC imaging in vivo and compare B-mode and SLSC images of human thyroid and liver.

  4. Imaging the position-dependent 3D force on microbeads subjected to acoustic radiation forces and streaming.

    PubMed

    Lamprecht, Andreas; Lakämper, Stefan; Baasch, Thierry; Schaap, Iwan A T; Dual, Jurg

    2016-07-01

    Acoustic particle manipulation in microfluidic channels is becoming a powerful tool in microfluidics to control micrometer sized objects in medical, chemical and biological applications. By creating a standing acoustic wave in the channel, the resulting pressure field can be employed to trap or sort particles. To design efficient and reproducible devices, it is important to characterize the pressure field throughout the volume of the microfluidic device. Here, we used an optically trapped particle as probe to measure the forces in all three dimensions. By moving the probe through the volume of the channel, we imaged spatial variations in the pressure field. In the direction of the standing wave this revealed a periodic energy landscape for 2 μm beads, resulting in an effective stiffness of 2.6 nN m(-1) for the acoustic trap. We found that multiple fabricated devices showed consistent pressure fields. Surprisingly, forces perpendicular to the direction of the standing wave reached values of up to 20% of the main-axis-values. To separate the direct acoustic force from secondary effects, we performed experiments with different bead sizes, which attributed some of the perpendicular forces to acoustic streaming. This method to image acoustically generated forces in 3D can be used to either minimize perpendicular forces or to employ them for specific applications in novel acoustofluidic designs. PMID:27302661

  5. Uniform asymptotic formula for the Aharonov Bohm wavefield

    NASA Astrophysics Data System (ADS)

    Hannay, J. H.

    2016-06-01

    A uniform asymptotic formula for the Aharonov–Bohm wavefield (that of a plane quantum wave scattered by a thin straight solenoid) far away from the solenoid is obtained in a direct way. Actually quite good accuracy is achieved even down to one wavelength away. The error is numerically of order radius^(‑3/2) for all values of polar angle, including directly forwards. Several previous formulas, uniform and otherwise, for the far field limit exist in the literature. All contain the essential ingredient: the Fresnel integral (complex error function), but ordinarily the error in these formulas is of order radius^(‑1/2) in the forwards direction where the Fresnel contribution is most important.

  6. Multicomponent wavefield characterization with a novel scanning laser interferometer.

    PubMed

    Blum, Thomas E; van Wijk, Kasper; Pouet, Bruno; Wartelle, Alexis

    2010-07-01

    The in-plane component of the wavefield provides valuable information about media properties from seismology to nondestructive testing. A new compact scanning laser ultrasonic interferometer collects light scattered away from the angle of incidence to provide the absolute ultrasonic displacement for both the out-of-plane and an in-plane components. This new system is tested by measuring the radial and vertical polarization of a Rayleigh wave in an aluminum half-space. The estimated amplitude ratio of the horizontal and vertical displacement agrees well with the theoretical value. The phase difference exhibits a small bias between the two components due to a slightly different frequency response between the two processing channels of the prototype electronic circuitry. PMID:20687699

  7. Multicomponent wavefield characterization with a novel scanning laser interferometer

    SciTech Connect

    Blum, Thomas E.; Wijk, Kasper van; Pouet, Bruno; Wartelle, Alexis

    2010-07-15

    The in-plane component of the wavefield provides valuable information about media properties from seismology to nondestructive testing. A new compact scanning laser ultrasonic interferometer collects light scattered away from the angle of incidence to provide the absolute ultrasonic displacement for both the out-of-plane and an in-plane components. This new system is tested by measuring the radial and vertical polarization of a Rayleigh wave in an aluminum half-space. The estimated amplitude ratio of the horizontal and vertical displacement agrees well with the theoretical value. The phase difference exhibits a small bias between the two components due to a slightly different frequency response between the two processing channels of the prototype electronic circuitry.

  8. Green's Function Retrieval and Marchenko Imaging in a Dissipative Acoustic Medium.

    PubMed

    Slob, Evert

    2016-04-22

    Single-sided Marchenko equations for Green's function construction and imaging relate the measured reflection response of a lossless heterogeneous medium to an acoustic wave field inside this medium. I derive two sets of single-sided Marchenko equations for the same purpose, each in a heterogeneous medium, with one medium being dissipative and the other a corresponding medium with negative dissipation. Double-sided scattering data of the dissipative medium are required as input to compute the surface reflection response in the corresponding medium with negative dissipation. I show that each set of single-sided Marchenko equations leads to Green's functions with a virtual receiver inside the medium: one exists inside the dissipative medium and one in the medium with negative dissipation. This forms the basis of imaging inside a dissipative heterogeneous medium. I relate the Green's functions to the reflection response inside each medium, from which the image can be constructed. I illustrate the method with a one-dimensional example that shows the image quality. The method has a potentially wide range of imaging applications where the material under test is accessible from two sides. PMID:27152808

  9. Green's Function Retrieval and Marchenko Imaging in a Dissipative Acoustic Medium

    NASA Astrophysics Data System (ADS)

    Slob, Evert

    2016-04-01

    Single-sided Marchenko equations for Green's function construction and imaging relate the measured reflection response of a lossless heterogeneous medium to an acoustic wave field inside this medium. I derive two sets of single-sided Marchenko equations for the same purpose, each in a heterogeneous medium, with one medium being dissipative and the other a corresponding medium with negative dissipation. Double-sided scattering data of the dissipative medium are required as input to compute the surface reflection response in the corresponding medium with negative dissipation. I show that each set of single-sided Marchenko equations leads to Green's functions with a virtual receiver inside the medium: one exists inside the dissipative medium and one in the medium with negative dissipation. This forms the basis of imaging inside a dissipative heterogeneous medium. I relate the Green's functions to the reflection response inside each medium, from which the image can be constructed. I illustrate the method with a one-dimensional example that shows the image quality. The method has a potentially wide range of imaging applications where the material under test is accessible from two sides.

  10. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography

    NASA Astrophysics Data System (ADS)

    Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-05-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular acoustic angiography transducers.

  11. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography.

    PubMed

    Ma, Jianguo; Martin, K Heath; Li, Yang; Dayton, Paul A; Shung, K Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-05-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for the design of intravascular acoustic angiography transducers. PMID:25856384

  12. Design factors of intravascular dual frequency transducers for super-harmonic contrast imaging and acoustic angiography

    PubMed Central

    Ma, Jianguo; Martin, K. Heath; Li, Yang; Dayton, Paul A.; Shung, K. Kirk; Zhou, Qifa; Jiang, Xiaoning

    2015-01-01

    Imaging of coronary vasa vasorum may lead to assessment of the vulnerable plaque development in diagnosis of atherosclerosis diseases. Dual frequency transducers capable of detection of microbubble super-harmonics have shown promise as a new contrast-enhanced intravascular ultrasound (CE-IVUS) platform with the capability of vasa vasorum imaging. Contrast-to-tissue ratio (CTR) in CE-IVUS imaging can be closely associated with the low frequency transmitter performance. In this paper, transducer designs encompassing different transducer layouts, transmitting frequencies, and transducer materials are compared for optimization of imaging performance. In the layout selection, the stacked configuration showed superior super-harmonic imaging compared with the interleaved configuration. In the transmitter frequency selection, a decrease in frequency from 6.5 MHz to 5 MHz resulted in an increase of CTR from 15 dB to 22 dB when receiving frequency was kept constant at 30 MHz. In the material selection, the dual frequency transducer with the lead magnesium niobate-lead titanate (PMN-PT) 1-3 composite transmitter yielded higher axial resolution compared to single crystal transmitters (70 μm compared to 150 μm pulse length). These comparisons provide guidelines for design of intravascular acoustic angiography transducers. PMID:25856384

  13. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Musharraf Zaman, Ph.D.; Younane Abousleiman, Ph.D.

    2001-04-01

    The oil and gas industry has encountered significant problems in the production of oil and gas from weak rocks (such as chalks and limestones) and from unconsolidated sand formations. Problems include subsidence, compaction, sand production, and catastrophic shallow water sand flows during deep water drilling. Together these cost the petroleum industry hundreds of millions of dollars annually. The goals of this first quarterly report is to document the progress on the project to provide data on the acoustic imaging and mechanical properties of soft rock and marine sediments. The project is intended to determine the geophysical (acoustic velocities) rock properties of weak, poorly cemented rocks and unconsolidated sands. In some cases these weak formations can create problems for reservoir engineers. For example, it cost Phillips Petroleum 1 billion dollars to repair of offshore production facilities damaged during the unexpected subsidence and compaction of the Ekofisk Field in the North Sea (Sulak 1991). Another example is the problem of shallow water flows (SWF) occurring in sands just below the seafloor encountered during deep water drilling operations. In these cases the unconsolidated sands uncontrollably flow up around the annulus of the borehole resulting in loss of the drill casing. The $150 million dollar loss of the Ursa development project in the U.S. Gulf Coast resulted from an uncontrolled SWF (Furlow 1998a,b; 1999a,b). The first three tasks outlined in the work plan are: (1) obtain rock samples, (2) construct new acoustic platens, (3) calibrate and test the equipment. These have been completed as scheduled. Rock Mechanics Institute researchers at the University of Oklahoma have obtained eight different types of samples for the experimental program. These include: (a) Danian Chalk, (b) Cordoba Cream Limestone, (c) Indiana Limestone, (d) Ekofisk Chalk, (e) Oil Creek Sandstone, (f) unconsolidated Oil Creek sand, and (g) unconsolidated Brazos river sand

  14. Variable ultrasound trigger delay for improved magnetic resonance acoustic radiation force imaging

    NASA Astrophysics Data System (ADS)

    Mougenot, Charles; Waspe, Adam; Looi, Thomas; Drake, James M.

    2016-01-01

    Magnetic resonance acoustic radiation force imaging (MR-ARFI) allows the quantification of microscopic displacements induced by ultrasound pulses, which are proportional to the local acoustic intensity. This study describes a new method to acquire MR-ARFI maps, which reduces the measurement noise in the quantification of displacement as well as improving its robustness in the presence of motion. Two MR-ARFI sequences were compared in this study. The first sequence ‘variable MSG’ involves switching the polarity of the motion sensitive gradient (MSG) between odd and even image frames. The second sequence named ‘static MSG’ involves a variable ultrasound trigger delay to sonicate during the first or second MSG for odd and even image frames, respectively. As previously published, the data acquired with a variable MSG required the use of reference data acquired prior to any sonication to process displacement maps. In contrary, data acquired with a static MSG were converted to displacement maps without using reference data acquired prior to the sonication. Displacement maps acquired with both sequences were compared by performing sonications for three different conditions: in a polyacrylamide phantom, in the leg muscle of a freely breathing pig and in the leg muscle of pig under apnea. The comparison of images acquired at even image frames and odd image frames indicates that the sequence with a static MSG provides a significantly better steady state (p  <  0.001 based on a Student’s t-test) than the images acquired with a variable MSG. In addition no reference data prior to sonication were required to process displacement maps for data acquired with a static MSG. The absence of reference data prior to sonication provided a 41% reduction of the spatial distribution of noise (p  <  0.001 based on a Student’s t-test) and reduced the sensitivity to motion for displacements acquired with a static MSG. No significant differences were expected and

  15. The utility of acoustic radiation force impulse imaging in diagnosing acute appendicitis and staging its severity

    PubMed Central

    Göya, Cemil; Hamidi, Cihad; Okur, Mehmet Hanifi; İçer, Mustafa; Oğuz, Abdullah; Hattapoğlu, Salih; Çetinçakmak, Mehmet Güli; Teke, Memik

    2014-01-01

    PURPOSE The aim of this study was to investigate the feasibility of using acoustic radiation force impulse (ARFI) imaging to diagnose acute appendicitis. METHODS Abdominal ultrasonography (US) and ARFI imaging were performed in 53 patients that presented with right lower quadrant pain, and the results were compared with those obtained in 52 healthy subjects. Qualitative evaluation of the patients was conducted by Virtual Touch™ tissue imaging (VTI), while quantitative evaluation was performed by Virtual Touch™ tissue quantification (VTQ) measuring the shear wave velocity (SWV). The severity of appendix inflammation was observed and rated using ARFI imaging in patients diagnosed with acute appendicitis. Alvarado scores were determined for all patients presenting with right lower quadrant pain. All patients diagnosed with appendicitis received appendectomies. The sensitivity and specificity of ARFI imaging relative to US was determined upon confirming the diagnosis of acute appendicitis via histopathological analysis. RESULTS The Alvarado score had a sensitivity and specificity of 70.8% and 20%, respectively, in detecting acute appendicitis. Abdominal US had 83.3% sensitivity and 80% specificity, while ARFI imaging had 100% sensitivity and 98% specificity, in diagnosing acute appendicitis. The median SWV value was 1.11 m/s (range, 0.6–1.56 m/s) for healthy appendix and 3.07 m/s (range, 1.37–4.78 m/s) for acute appendicitis. CONCLUSION ARFI imaging may be useful in guiding the clinical management of acute appendicitis, by helping its diagnosis and determining the severity of appendix inflammation. PMID:25323836

  16. Evaluation of real-time acoustical holography for breast imaging and biopsy guidance

    NASA Astrophysics Data System (ADS)

    Lehman, Constance D.; Andre, Michael P.; Fecht, Barbara A.; Johansen, Jennifer M.; Shelby, Ronald L.; Shelby, Jerod O.

    1999-05-01

    Ultrasound is an attractive modality for adjunctive characterization of certain breast lesions, but it is not considered specific for cancer and it is not recommended for screening. An imaging technique remarkably different from pulse-echo ultrasound, termed Optical SonographyTM (Advanced Diagnostics, Inc.), uses the through-transmission signal. The method was applied to breast examinations in 41 asymptomatic and symptomatic women ranging in age from 18 to 83 years to evaluate this imaging modality for detection and characterization of breast disease and normal tissue. This approach uses coherent sound and coherent light to produce real-time, large field-of-view images with pronounced edge definition in soft tissues of the body. The system patient interface was modified to improve coupling to the breast and bring the chest wall to within 3 cm of the sound beam. System resolution (full width half maximum of the line-spread function) was 0.5 mm for a swept-frequency beam centered at 2.7 MHz. Resolution degrades slightly in the periphery of the very large 15.2-cm field of view. Dynamic range of the reconstructed 'raw' images (no post processing) was 3000:1. Included in the study population were women with dense parenchyma, palpable ductal carcinoma in situ with negative mammography, superficial and deep fibroadenomas, and calcifications. Successful breast imaging was performed in 40 of 41 women. These images were then compared with images generated using conventional X-ray mammography and pulse-echo ultrasound. Margins of lesions and internal textures were particularly well defined and provided substantial contrast to fatty and dense parenchyma. In two malignant lesions, Optical SonographyTM appeared to approximate more closely tumor extent compared to mammography than pulse-echo sonography. These preliminary studies indicate the method has unique potential for detecting, differentiating, and guiding the biopsy of breast lesions using real-time acoustical holography.

  17. Preliminary study of copper oxide nanoparticles acoustic and magnetic properties for medical imaging

    NASA Astrophysics Data System (ADS)

    Perlman, Or; Weitz, Iris S.; Azhari, Haim

    2015-03-01

    The implementation of multimodal imaging in medicine is highly beneficial as different physical properties may provide complementary information, augmented detection ability, and diagnosis verification. Nanoparticles have been recently used as contrast agents for various imaging modalities. Their significant advantage over conventional large-scale contrast agents is the ability of detection at early stages of the disease, being less prone to obstacles on their path to the target region, and possible conjunction to therapeutics. Copper ions play essential role in human health. They are used as a cofactor for multiple key enzymes involved in various fundamental biochemistry processes. Extremely small size copper oxide nanoparticles (CuO-NPs) are readily soluble in water with high colloidal stability yielding high bioavailability. The goal of this study was to examine the magnetic and acoustic characteristics of CuO-NPs in order to evaluate their potential to serve as contrast imaging agent for both MRI and ultrasound. CuO-NPs 7nm in diameter were synthesized by hot solution method. The particles were scanned using a 9.4T MRI and demonstrated a concentration dependent T1 relaxation time shortening phenomenon. In addition, it was revealed that CuO-NPs can be detected using the ultrasonic B-scan imaging. Finally, speed of sound based ultrasonic computed tomography was applied and showed that CuO-NPs can be clearly imaged. In conclusion, the preliminary results obtained, positively indicate that CuO-NPs may be imaged by both MRI and ultrasound. The results motivate additional in-vivo studies, in which the clinical utility of fused images derived from both modalities for diagnosis improvement will be studied.

  18. A method for the frequency control in time-resolved two-dimensional gigahertz surface acoustic wave imaging

    SciTech Connect

    Kaneko, Shogo; Tomoda, Motonobu; Matsuda, Osamu

    2014-01-15

    We describe an extension of the time-resolved two-dimensional gigahertz surface acoustic wave imaging based on the optical pump-probe technique with periodic light source at a fixed repetition frequency. Usually such imaging measurement may generate and detect acoustic waves with their frequencies only at or near the integer multiples of the repetition frequency. Here we propose a method which utilizes the amplitude modulation of the excitation pulse train to modify the generation frequency free from the mentioned limitation, and allows for the first time the discrimination of the resulted upper- and lower-side-band frequency components in the detection. The validity of the method is demonstrated in a simple measurement on an isotropic glass plate covered by a metal thin film to extract the dispersion curves of the surface acoustic waves.

  19. Full-Wave Iterative Image Reconstruction in Photoacoustic Tomography With Acoustically Inhomogeneous Media

    PubMed Central

    Huang, Chao; Wang, Kun; Nie, Liming; Wang, Lihong V.; Anastasio, Mark A.

    2014-01-01

    Existing approaches to image reconstruction in photoacoustic computed tomography (PACT) with acoustically heterogeneous media are limited to weakly varying media, are computationally burdensome, and/or cannot effectively mitigate the effects of measurement data incompleteness and noise. In this work, we develop and investigate a discrete imaging model for PACT that is based on the exact photoacoustic (PA) wave equation and facilitates the circumvention of these limitations. A key contribution of the work is the establishment of a procedure to implement a matched forward and backprojection operator pair associated with the discrete imaging model, which permits application of a wide-range of modern image reconstruction algorithms that can mitigate the effects of data incompleteness and noise. The forward and backprojection operators are based on the k-space pseudospectral method for computing numerical solutions to the PA wave equation in the time domain. The developed reconstruction methodology is investigated by use of both computer-simulated and experimental PACT measurement data. PMID:23529196

  20. Acoustically active liposome-nanobubble complexes for enhanced ultrasonic imaging and ultrasound-triggered drug delivery.

    PubMed

    Nguyen, An T; Wrenn, Steven P

    2014-01-01

    Ultrasound is well known as a safe, reliable imaging modality. A historical limitation of ultrasound, however, was its inability to resolve structures at length scales less than nominally 20 µm, which meant that classical ultrasound could not be used in applications such as echocardiography and angiogenesis where one requires the ability to image small blood vessels. The advent of ultrasound contrast agents, or microbubbles, removed this limitation and ushered in a new wave of enhanced ultrasound applications. In recent years, the microbubbles have been designed to achieve yet another application, namely ultrasound-triggered drug delivery. Ultrasound contrast agents are thus tantamount to 'theranostic' vehicles, meaning they can do both therapy (drug delivery) and imaging (diagnostics). The use of ultrasound contrast agents as drug delivery vehicles, however, is perhaps less than ideal when compared to traditional drug delivery vehicles (e.g., polymeric microcapsules and liposomes) which have greater drug carrying capacities. The drawback of the traditional drug delivery vehicles is that they are not naturally acoustically active and cannot be used for imaging. The notion of a theranostic vehicle is sufficiently intriguing that many attempts have been made in recent years to achieve a vehicle that combines the echogenicity of microbubbles with the drug carrying capacity of liposomes. The attempts can be classified into three categories, namely entrapping, tethering, and nesting. Of these, nesting is the newest-and perhaps the most promising. PMID:24459007

  1. Photoacoustic and ultrasound imaging with a gas-coupled laser acoustic line detector

    NASA Astrophysics Data System (ADS)

    Johnson, Jami L.; van Wijk, Kasper; Caron, James N.; Timmerman, Miriam

    2016-03-01

    Conventional contacting transducers are highly sensitive and readily available for ultrasonic and photoacoustic imaging. On the other hand, optical detection can be advantageous when a small sensor footprint, large bandwidth and no contact are essential. However, most optical methods utilizing interferometry or Doppler vibrometry rely on the reflection of light from the object. We present a non-contact detection method for photoacoustic and ultrasound imaging--termed Gas-Coupled Laser Acoustic Detection (GCLAD)--that does not involve surface reflectivity. GCLAD measures the displacement along a line in the air parallel to the object. Information about point displacements along the line is lost with this method, but resolution is increased over techniques that utilize finite point-detectors when used as an integrating line detector. In this proceeding, we present a formula for quantifying surface displacement remotely with GCLAD. We will validate this result by comparison with a commercial vibrometer. Finally, we will present two-dimensional imaging results using GCLAD as a line detector for photoacoustic and laser-ultrasound imaging.

  2. Measurement of microbubble-induced acoustic microstreaming using microparticle image velocimetry

    NASA Astrophysics Data System (ADS)

    Tho, Paul; Zhu, Yonggang; Manasseh, Richard; Ooi, Andrew

    2005-02-01

    Micro particle image velocimetry (PIV) measurements of the velocity fields around oscillating gas bubbles in microfluidic geometries were undertaken. Two sets of experiments were performed. The first measured the acoustic microstreaming around a gas bubble with a radius of 195 μm attached to a wall in a chamber of 30 mm× 30 mm× 0.66 mm. Under acoustic excitation, vigorous streaming in the form of a circulation around on the bubble was observed. The streaming flow was highest near the surface of the bubble with velocities around 1mm/s measured. The velocity magnitude decreased rapidly with increasing distance from the bubble. The velocity field determined by micro-PIV matched the streaklines of the fluorescent particles very well. The second set of experiments measured the streaming at the interface between a trapped air bubble and water inside a microchannel of cross section 100 μm × 90 μm. The streaming flow was limited to within a short distance from the interface and was observed as a looping flow, moving towards the interface from the top and being circulated back from the bottom of the channel. The characteristic streaming velocity was in the order of 100 μm/s.

  3. Anisotropic Shear Velocity Models of the North American Upper Mantle Based on Waveform Inversion and Numerical Wavefield Computations.

    NASA Astrophysics Data System (ADS)

    Pierre, C.

    2015-12-01

    The Earthscope TA deployment across the continental United-State (US) has reached its eastern part, providing the opportunity for high-resolution 3D seismic velocity imaging of both lithosphere and asthenosphere across the entire north-American continent (NA). Previously (Yuan et al., 2014), we presented a 3D radially anisotropic shear wave (Vs) model of North America (NA) lithospheric mantle based on full waveform tomography, combining teleseismic and regional distance data sampling the NA. Regional wavefield computations were performed numerically, using a regional Spectral Element code (RegSEM, Cupillard et al., 2012), while teleseismic computations were performed approximately, using non-linear asymptotic coupling theory (NACT, Li and Romanowicz, 1995). For both datasets, the inversion was performed iteratively, using a Gauss-Newton scheme, with kernels computed using either NACT or the surface wave, path average approximation (PAVA), depending on the source-station distance. We here present a new radially anisotropic lithospheric/asthenospheric model of Vs for NA based entirely on SEM-based numerical waveforms from an augmented dataset of 155 regional events and 70 teleseismic events. The forward wavefield computations are performed using RegSEM down to 40s, starting from our most recent whole mantle 3D radially anisotropic Vs model (SEMUCB-wm1, French and Romanowicz, 2014). To model teleseismic wavefields within our regional computational domain, we developed a new modeling technique which allows us to replace a distant source by virtual sources at the boundary of the computational domain (Masson et al., 2014). Computing virtual sources requires one global simulation per teleseismic events.We then compare two models obtained: one using NACT/PAVA kernels as in our previous work, and another using hybrid kernels, where the Hessian is computed using NACT/PAVA, but the gradient is computed numerically from the adjoint wavefield, providing more accurate kernels

  4. Evaluating the intensity of the acoustic radiation force impulse (ARFI) in intravascular ultrasound (IVUS) imaging: Preliminary in vitro results.

    PubMed

    Shih, Cho-Chiang; Lai, Ting-Yu; Huang, Chih-Chung

    2016-08-01

    The ability to measure the elastic properties of plaques and vessels is significant in clinical diagnosis, particularly for detecting a vulnerable plaque. A novel concept of combining intravascular ultrasound (IVUS) imaging and acoustic radiation force impulse (ARFI) imaging has recently been proposed. This method has potential in elastography for distinguishing between the stiffness of plaques and arterial vessel walls. However, the intensity of the acoustic radiation force requires calibration as a standard for the further development of an ARFI-IVUS imaging device that could be used in clinical applications. In this study, a dual-frequency transducer with 11MHz and 48MHz was used to measure the association between the biological tissue displacement and the applied acoustic radiation force. The output intensity of the acoustic radiation force generated by the pushing element ranged from 1.8 to 57.9mW/cm(2), as measured using a calibrated hydrophone. The results reveal that all of the acoustic intensities produced by the transducer in the experiments were within the limits specified by FDA regulations and could still displace the biological tissues. Furthermore, blood clots with different hematocrits, which have elastic properties similar to the lipid pool of plaques, with stiffness ranging from 0.5 to 1.9kPa could be displaced from 1 to 4μm, whereas the porcine arteries with stiffness ranging from 120 to 291kPa were displaced from 0.4 to 1.3μm when an acoustic intensity of 57.9mW/cm(2) was used. The in vitro ARFI images of the artery with a blood clot and artificial arteriosclerosis showed a clear distinction of the stiffness distributions of the vessel wall. All the results reveal that ARFI-IVUS imaging has the potential to distinguish the elastic properties of plaques and vessels. Moreover, the acoustic intensity used in ARFI imaging has been experimentally quantified. Although the size of this two-element transducer is unsuitable for IVUS imaging, the

  5. Comparison of ultrasound B-mode, strain imaging, acoustic radiation force impulse displacement and shear wave velocity imaging using real time clinical breast images

    NASA Astrophysics Data System (ADS)

    Manickam, Kavitha; Machireddy, Ramasubba Reddy; Raghavan, Bagyam

    2016-04-01

    It has been observed that many pathological process increase the elastic modulus of soft tissue compared to normal. In order to image tissue stiffness using ultrasound, a mechanical compression is applied to tissues of interest and local tissue deformation is measured. Based on the mechanical excitation, ultrasound stiffness imaging methods are classified as compression or strain imaging which is based on external compression and Acoustic Radiation Force Impulse (ARFI) imaging which is based on force generated by focused ultrasound. When ultrasound is focused on tissue, shear wave is generated in lateral direction and shear wave velocity is proportional to stiffness of tissues. The work presented in this paper investigates strain elastography and ARFI imaging in clinical cancer diagnostics using real time patient data. Ultrasound B-mode imaging, strain imaging, ARFI displacement and ARFI shear wave velocity imaging were conducted on 50 patients (31 Benign and 23 malignant categories) using Siemens S2000 machine. True modulus contrast values were calculated from the measured shear wave velocities. For ultrasound B-mode, ARFI displacement imaging and strain imaging, observed image contrast and Contrast to Noise Ratio were calculated for benign and malignant cancers. Observed contrast values were compared based on the true modulus contrast values calculated from shear wave velocity imaging. In addition to that, student unpaired t-test was conducted for all the four techniques and box plots are presented. Results show that, strain imaging is better for malignant cancers whereas ARFI imaging is superior than strain imaging and B-mode for benign lesions representations.

  6. Toward a Better Understanding of the Seismolectric Logging Wavefields and the Earthquake Coseismic Electrokinetic Signals

    NASA Astrophysics Data System (ADS)

    Hu, H.; Guan, W.; Wang, Z.

    2014-12-01

    Borehole electrokinetic wavefields have been theoretically simulated and experimentally recorded. However, it is still challenging to explain some of the signals in the full seismoeletric waveform. Similarly, while earthquake coseismic electric and magnetic signals were recorded and theoretically modeled, there are some basic questions to be answered regarding the formulation of the earthquake electrokinetic field. First, an electromagnetic signal appears at the same time in all recorded full waveforms when an acoustic wave is incident on the borehole wall or an interface between two porous media. Is it a traveling electromagnetic wave or a field? This is explained by a comparison between the waveforms obtained by solving the full Pride equations and those by a quasi-static approximation to the seismic-to-electric conversion. Second, a magnetic signal accompanies the borehole P-wave. Does that contradicts to Pride's prediction that no magnetic signal travels with a P-wave? We will show that the borehole P-wave consists of plane fast-P, slow-P and shear waves. It is the plane S-wave that brings about the magnetic field. Thirdly, it was proposed that there were no seismoelectric signal accompanying the collar wave during seismoelectric logging while drilling, because the electrokinetic conversion occurs only in the porous formation. Why there is an electric signal accompanies the acoustic collar wave? A detailed study of the acoustic field in the formation reveals that there is a wave propagates with the collar wave speed in the formation. This wave is present in the calculated full waveforms, either by the discrete wavenumber method or by the finite-difference-time-domain algorithm. That explains the existence of a noise signal with collar-wave speed in the full waveform of the electric field recorded during seismoelectric logging while drilling. Finally, an earthquake is usually modeled by a double couple in an elastic medium, and the displacement field is

  7. Failure prediction in ceramic composites using acoustic emission and digital image correlation

    NASA Astrophysics Data System (ADS)

    Whitlow, Travis; Jones, Eric; Przybyla, Craig

    2016-02-01

    The objective of the work performed here was to develop a methodology for linking in-situ detection of localized matrix cracking to the final failure location in continuous fiber reinforced CMCs. First, the initiation and growth of matrix cracking are measured and triangulated via acoustic emission (AE) detection. High amplitude events at relatively low static loads can be associated with initiation of large matrix cracks. When there is a localization of high amplitude events, a measurable effect on the strain field can be observed. Full field surface strain measurements were obtained using digital image correlation (DIC). An analysis using the combination of the AE and DIC data was able to predict the final failure location.

  8. Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement

    NASA Astrophysics Data System (ADS)

    Shen, Changle; Xie, Wenjun; Wei, Bingbo

    2010-12-01

    A type of non-axisymmetric oscillations of acoustically levitated drops is excited by modulating the ultrasound field at proper frequencies. These oscillations are recorded by a high speed camera and analyzed with a digital image processing method. They are demonstrated to be the third mode sectorial oscillations, and their frequencies are found to decrease with the increase of equatorial radius of the drops, which can be described by a modified Rayleigh equation. These oscillations decay exponentially after the cessation of ultrasound field modulation. The decaying rates agree reasonably with Lamb's prediction. The rotating rate of the drops accompanying the shape oscillations is found to be less than 1.5 rounds per second. The surface tension of aqueous ethanol has been measured according to the modified Rayleigh equation. The results agree well with previous reports, which demonstrates the possible application of this kind of sectorial oscillations in noncontact measurement of liquid surface tension.

  9. Acoustic characterization of ultrasound contrast microbubbles and echogenic liposomes: Applications to imaging and drug-delivery

    NASA Astrophysics Data System (ADS)

    Paul, Shirshendu

    Micron- to nanometer - sized ultrasound agents, like encapsulated microbubbles and echogenic liposomes (ELIPs), are being actively developed for possible clinical implementations in diagnostic imaging and ultrasound mediated drug/gene delivery. The primary objective of this thesis is to characterize the acoustic behavior of and the ultrasound-mediated contents release from these contrast agents for developing multi-functional ultrasound contrast agents. Subharmonic imaging using contrast microbubbles can improve image quality by providing a higher signal to noise ratio. However, the design and development of contrast microbubbles with favorable subharmonic behavior requires accurate mathematical models capable of predicting their nonlinear dynamics. To this goal, 'strain-softening' viscoelastic interfacial models of the encapsulation were developed and subsequently utilized to simulate the dynamics of encapsulated microbubbles. A hierarchical two-pronged approach of modeling --- a model is applied to one set of experimental data to obtain the model parameters (material characterization), and then the model is validated against a second independent experiment --- is demonstrated in this thesis for two lipid coated (SonazoidRTM and DefinityRTM) and a few polymer (polylactide) encapsulated microbubbles. The proposed models were successful in predicting several experimentally observed behaviors e.g., low subharmonic thresholds and "compression-only" radial oscillations. Results indicate that neglecting the polydisperse size distribution of contrast agent suspensions, a common practice in the literature, can lead to inaccurate results. In vitro experimental investigation of the dependence of subharmonic response from these microbubbles on the ambient pressure is also in conformity with the recent numerical investigations, showing both increase or decrease under appropriate excitation conditions. Experimental characterization of the ELIPs and polymersomes was performed

  10. A Spinal Cord Window Chamber Model for In Vivo Longitudinal Multimodal Optical and Acoustic Imaging in a Murine Model

    PubMed Central

    Maeda, Azusa; Conroy, Leigh; McMullen, Jesse D.; Silver, Jason I.; Stapleton, Shawn; Vitkin, Alex; Lindsay, Patricia; Burrell, Kelly; Zadeh, Gelareh; Fehlings, Michael G.; DaCosta, Ralph S.

    2013-01-01

    In vivo and direct imaging of the murine spinal cord and its vasculature using multimodal (optical and acoustic) imaging techniques could significantly advance preclinical studies of the spinal cord. Such intrinsically high resolution and complementary imaging technologies could provide a powerful means of quantitatively monitoring changes in anatomy, structure, physiology and function of the living cord over time after traumatic injury, onset of disease, or therapeutic intervention. However, longitudinal in vivo imaging of the intact spinal cord in rodent models has been challenging, requiring repeated surgeries to expose the cord for imaging or sacrifice of animals at various time points for ex vivo tissue analysis. To address these limitations, we have developed an implantable spinal cord window chamber (SCWC) device and procedures in mice for repeated multimodal intravital microscopic imaging of the cord and its vasculature in situ. We present methodology for using our SCWC to achieve spatially co-registered optical-acoustic imaging performed serially for up to four weeks, without damaging the cord or induction of locomotor deficits in implanted animals. To demonstrate the feasibility, we used the SCWC model to study the response of the normal spinal cord vasculature to ionizing radiation over time using white light and fluorescence microscopy combined with optical coherence tomography (OCT) in vivo. In vivo power Doppler ultrasound and photoacoustics were used to directly visualize the cord and vascular structures and to measure hemoglobin oxygen saturation through the complete spinal cord, respectively. The model was also used for intravital imaging of spinal micrometastases resulting from primary brain tumor using fluorescence and bioluminescence imaging. Our SCWC model overcomes previous in vivo imaging challenges, and our data provide evidence of the broader utility of hybridized optical-acoustic imaging methods for obtaining multiparametric and rich

  11. Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale

    SciTech Connect

    P Oshkai; M Geveci; D Rockwell; M Pollack

    2004-05-24

    Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

  12. A Bayesian approach for characterization of soft tissue viscoelasticity in acoustic radiation force imaging.

    PubMed

    Zhao, Xiaodong; Pelegri, Assimina A

    2016-04-01

    Biomechanical imaging techniques based on acoustic radiation force (ARF) have been developed to characterize the viscoelasticity of soft tissue by measuring the motion excited by ARF non-invasively. The unknown stress distribution in the region of excitation limits an accurate inverse characterization of soft tissue viscoelasticity, and single degree-of-freedom simplified models have been applied to solve the inverse problem approximately. In this study, the ARF-induced creep imaging is employed to estimate the time constant of a Voigt viscoelastic tissue model, and an inverse finite element (FE) characterization procedure based on a Bayesian formulation is presented. The Bayesian approach aims to estimate a reasonable quantification of the probability distributions of soft tissue mechanical properties in the presence of measurement noise and model parameter uncertainty. Gaussian process metamodeling is applied to provide a fast statistical approximation based on a small number of computationally expensive FE model runs. Numerical simulation results demonstrate that the Bayesian approach provides an efficient and practical estimation of the probability distributions of time constant in the ARF-induced creep imaging. In a comparison study with the single degree of freedom models, the Bayesian approach with FE models improves the estimation results even in the presence of large uncertainty levels of the model parameters. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26255624

  13. IRIS Arrays: Observing Wavefields at Multiple Scales and Frequencies

    NASA Astrophysics Data System (ADS)

    Sumy, D. F.; Woodward, R.; Frassetto, A.

    2014-12-01

    The Incorporated Research Institutions for Seismology (IRIS) provides instruments for creating and operating seismic arrays at a wide range of scales. As an example, for over thirty years the IRIS PASSCAL program has provided instruments to individual Principal Investigators to deploy arrays of all shapes and sizes on every continent. These arrays have ranged from just a few sensors to hundreds or even thousands of sensors, covering areas with dimensions of meters to thousands of kilometers. IRIS also operates arrays directly, such as the USArray Transportable Array (TA) as part of the EarthScope program. Since 2004, the TA has rolled across North America, at any given time spanning a swath of approximately 800 km by 2,500 km, and thus far sampling 2% of the Earth's surface. This achievement includes all of the lower-48 U.S., southernmost Canada, and now parts of Alaska. IRIS has also facilitated specialized arrays in polar environments and on the seafloor. In all cases, the data from these arrays are freely available to the scientific community. As the community of scientists who use IRIS facilities and data look to the future they have identified a clear need for new array capabilities. In particular, as part of its Wavefields Initiative, IRIS is exploring new technologies that can enable large, dense array deployments to record unaliased wavefields at a wide range of frequencies. Large-scale arrays might utilize multiple sensor technologies to best achieve observing objectives and optimize equipment and logistical costs. Improvements in packaging and power systems can provide equipment with reduced size, weight, and power that will reduce logistical constraints for large experiments, and can make a critical difference for deployments in harsh environments or other situations where rapid deployment is required. We will review the range of existing IRIS array capabilities with an overview of previous and current deployments and examples of data and results. We

  14. Numerical Resolution of Seismic Wavefield Simulations in Southern California

    NASA Astrophysics Data System (ADS)

    Tape, C.; Casarotti, E.

    2014-12-01

    Seismic wavefield simulations can provide accurate solutions to the wave equation, even for three-dimensional seismic velocity models with topography, basin structures, anisotropy, attenuation, and other complexities. But how accurate are these numerical solutions? In many cases the effect of numerical dispersion on the synthetic seismograms looks quite similar to the effects of structural complexities. Therefore it is important to know the numerical resolution of the synthetic seismograms, that is, the minimum period that provides a quantifiably numerically accurate solution to the wave equation. Numerical resolution can be discussed in terms of a combined mesh and velocity model, or in terms of an individual source-station path within the same mesh and velocity model. Here we discuss two approaches for quantifying the numerical resolution. In the first approach we estimate the minimum resolvable period of each element within the finite element mesh. This calculation, performed within SPECFEM3D, requires no wavefield simulations and is based only on the size of each element and the minimum velocity within each element. The calculation produces a volumetric field that shows the estimated minimum resolvable period within each element of the (generally unstructured) mesh. In the second approach we choose a set of earthquakes to be used within a tomographic inversion. For each earthquake we compute one simulation using a fine discretization of gridpoints on the finite-element mesh and another simulation using a coarse discretization. We filter both sets of seismograms over a range of periods and then quantify the waveform differences. The minimum resolvable period (or numerical resolution) is identified by the minimum period for which the synthetic seismogram from the coarse-mesh and fine-mesh simulations is quantifiably the same. This calculation provides a path-specific minimum resolvable period that can be used to guide the choice of measurement filtering for a

  15. SIMULTANEOUS BILATERAL REAL-TIME 3-D TRANSCRANIAL ULTRASOUND IMAGING AT 1 MHZ THROUGH POOR ACOUSTIC WINDOWS

    PubMed Central

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

    2013-01-01

    Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%–29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging—the ultrasound brain helmet—and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field. PMID:23415287

  16. Underwater Acoustics

    NASA Astrophysics Data System (ADS)

    Kuperman, William A.; Roux, Philippe

    It is well underwater established that sound waves, compared to electromagnetic waves, propagate long distances in the ocean. Hence, in the ocean as opposed to air or a vacuum, one uses sound navigation and ranging (SONAR) instead navigation and ranging (SONAR) of radar, acoustic communication instead of radio, and acoustic imaging and tomography instead of microwave or optical imaging or X-ray tomography. Underwater acoustics is the science of sound in water (most commonly in the ocean) and encompasses not only the study of sound propagation, but also the masking of sound signals by interfering phenomenon and signal processing for extracting these signals from interference. This chapter we will present the basics physics of ocean acoustics and then discuss applications.

  17. Quantitative observations of a deep-sea hydrothermal plume using an acoustic imaging sonar

    NASA Astrophysics Data System (ADS)

    Xu, Guangyu

    The Cabled Observatory Vent Imaging Sonar (COVIS) is used to quantitatively monitor the hydrothermal discharge from the Grotto mound, a venting sulfide structure on the Endeavour Segment of the Juan de Fuca Ridge. Since its deployment in September 2010, COVIS has recorded a multi-year long, near-continuous acoustic backscatter dataset. Further analysis of this dataset sheds light on the backscattering mechanisms within the buoyant plumes above Grotto and yields quantitative information on the influences of oceanic, atmospheric, and geological processes on the dynamics and heat source of the plumes. An investigation of the acoustic scattering mechanisms within the buoyant plumes issuing from Grotto suggests the dominant scattering mechanism within the plumes is the temperature fluctuations caused by the turbulent mixing of the buoyant plumes with the ambient seawater. In comparison, the backscatter from plume particles is negligible at lower levels of the plume but can potentially be significant at higher levels. Furthermore, this finding demonstrates the potential of inverting the acoustic backsatter to estimate the temperature fluctuations within the plumes. Processing the backscatter dataset recorded by COVIS yields time-series measurements of the vertical flow rate, volume transport, expansion rate of the largest buoyant plume above Grotto. Further analysis of those time-series measurements suggests the rate at which the ambient seawater is entrained into the plume increases with the magnitude of the ambient ocean currents---the current-driven entrainment. Furthermore, the oscillations in the ambient ocean currents that are driven by tidal and atmospheric forcing are introduced into the flow field within the plume through the current-driven entrainment. An inverse method has been developed to estimate the source heat transport driving the largest plume above Grotto from its volume transport estimates. The result suggests the heat transport driving the plume was

  18. A Compressive Multi-Frequency Linear Sampling Method for Underwater Acoustic Imaging.

    PubMed

    Alqadah, Hatim F

    2016-06-01

    This paper investigates the use of a qualitative inverse scattering method known as the linear sampling method (LSM) for imaging underwater scenes using limited aperture receiver configurations. The LSM is based on solving a set of unstable integral equations known as the far-field equations and whose stability breaks down even further for under-sampled observation aperture data. Based on the results of a recent study concerning multi-frequency LSM imaging, we propose an iterative inversion method that is founded upon a compressive sensing framework. In particular, we leverage multi-frequency diversity in the data by imposing a partial frequency variation prior on the solution which we show is justified when the frequency bandwidth is sampled finely enough. We formulate an alternating direction method of multiplier approach to minimize the proposed cost function. Proof of concept is established through numerically generated data as well as experimental acoustic measurements taken in a shallow pool facility at the U.S Naval Research Laboratory. PMID:27093719

  19. Acoustic logging on ultralow density cement bonded quality evaluation in cased hole

    NASA Astrophysics Data System (ADS)

    Wang, H.; Shang, X.; Chen, T.; Tao, G.

    2011-12-01

    Cementing operation after drilling boreholes ensures oil and gas to be extracted effectively and avoids oil spill events such as BP Mexico oil leakage events. However, the loss of cement in deep formation due to its high density happens and raises issues. In order to overcome this problem, ultralow density cement or gas-based cements are used more and more commonly in recent years. Current acoustic evaluation tools, used to determine the cement bond quality, are designed for conventional high density cement. Therefore, they are not capable to image the ultralow density cement, whose acoustic properties are similar to borehole drilling mud. In this paper, a new acoustic technique is developed to image the ultralow density cement behind case. Finite difference method and analytical methods are used to simulate the wave-field of cased borehole which ultralow density cement bonded on. Based on the simulations, the optimal parameters of the evaluation tool design are proposed including spacing (from source to the nearest receiver and between the two neighboring receiver), frequency of source.

  20. Rapid acquisition of high resolution full wave-field borehole seismic data

    SciTech Connect

    Sleefe, G.E.; Harding, R.S. Jr.; Fairborn, J.W.; Paulsson, B.N.P.

    1993-04-01

    An essential requirement for both Vertical Seismic Profiling (VSP) and Cross-Hole Seismic Profiling (CHSP) is the rapid acquisition of high resolution borehole seismic data. Additionally, full wave-field recording using three-component receivers enables the use of both transmitted and reflected elastic wave events in the resulting seismic images of the subsurface. To this end, an advanced three- component multi-station borehole seismic receiver system has been designed and developed by Sandia National Laboratory (SNL) and OYO Geospace. The system requires data from multiple three-component wall-locking accelerometer packages and telemeters digital data to the surface in real-time. Due to the multiplicity of measurement stations and the real-time data link, acquisition time for the borehole seismic survey is significantly reduced. The system was tested at the Chevron La Habra Test Site using Chevron`s clamped axial borehole vibrator as the seismic source. Several source and receiver fans were acquired using a four-station version of the advanced system. For comparison purposes, an equivalent data set was acquired using a standard analog wall-locking geophone receiver. The test data indicate several enhancements provided by the multi-station receiver relative to the standard, drastically improved signal-to-noise ratio, increased signal bandwidth, the detection of multiple reflectors, and a true 4:1 reduction in survey time.

  1. Inferences of Particle Size and Composition From Video-like Images Based on Acoustic Data: Grotto Plume, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Santilli, K.; Dastur, J.; Silver, D.

    2004-12-01

    Optical and acoustic scattering from particles in a seafloor hydrothermal plume can be related if the particle properties and scattering mechanisms are known. We assume Rayleigh backscattering of sound and Mie forward scattering of light. We then use the particle concentrations implicit in the observed acoustic backscatter intensity to recreate the optical image a camera would see given a particular lighting level. The motivation for this study is to discover what information on particle size and composition in the buoyant plume can be inferred from a comparison of the calculated optical images (based on acoustic data) with actual video images from the acoustic acquisition cruise and the IMAX film "Volcanoes of the Deep Sea" (Stephen Low Productions, Inc.). Because the geologists, biologists and oceanographers involved in the study of seafloor hydrothermal plumes all "see" plumes in different ways, an additional motivation is to create more realistic plume images from the acoustic data. By using visualization techniques, with realistic lighting models, we can convert the plume image from mechanical waves (sound) to electromagnetic waves (light). The resulting image depends on assumptions about the particle size distribution and composition. Conversion of the volume scattering coefficients from Rayleigh to Mie scattering is accomplished by an extinction scale factor that depends on the wavelengths of light and sound and on the average particle size. We also make an adjustment to the scattered light based on the particles reflectivity (albedo) and color. We present a series of images of acoustic data for Grotto Plume, Main Endeavour Field (within the Endeavour ISS Site) using both realistic lighting models and traditional visualization techniques to investigate the dependence of the images on assumptions about particle composition and size. Sensitivity analysis suggests that the visibility of the buoyant plume increases as the intensity of supplied light increases

  2. Experimental results for a prototype 3-D acoustic imaging system using an ultra-sparse planar array

    NASA Astrophysics Data System (ADS)

    Impagliazzo, John M.; Chiang, Alice M.; Broadstone, Steven R.

    2002-11-01

    A handheld high resolution sonar has been under development to provide Navy Divers with a 3-D acoustic imaging system for mine reconnaissance. An ultra-sparse planar array, consisting of 121 1 mm x1 mm, 2 MHz elements, was fabricated to provide 3-D acoustic images. The array was 10 cm x10 cm. A full array at this frequency with elements at half-wavelength spacing would consist of 16384 elements. The first phase of testing of the planar array was completed in September 2001 with the characterization of the array in the NUWC Acoustic Test Facility (ATF). The center frequency was 2 MHz with a 667 kHz bandwidth. A system-level technology demonstration will be conducted in July 2002 with a real-time beamformer and near real-time 3-D imaging software. The demonstration phase consists of imaging simple targets at a range of 3 m in the ATF. Experimental results obtained will be reported on. [Work supported by the Defense Applied Research Project Agency, Advance Technology Office, Dr. Theo Kooij, Program Manager.

  3. In vivo study of transverse carpal ligament stiffness using acoustic radiation force impulse (ARFI) imaging.

    PubMed

    Shen, Zhilei Liu; Vince, D Geoffrey; Li, Zong-Ming

    2013-01-01

    The transverse carpal ligament (TCL) forms the volar boundary of the carpal tunnel and may provide mechanical constraint to the median nerve, leading to carpal tunnel syndrome. Therefore, the mechanical properties of the TCL are essential to better understand the etiology of carpal tunnel syndrome. The purpose of this study was to investigate the in vivo TCL stiffness using acoustic radiation force impulse (ARFI) imaging. The shear wave velocity (SWV) of the TCL was measured using Virtual Touch IQ(TM) software in 15 healthy, male subjects. The skin and the thenar muscles were also examined as reference tissues. In addition, the effects of measurement location and ultrasound transducer compression on the SWV were studied. The SWV of the TCL was dependent on the tissue location, with greater SWV values within the muscle-attached region than those outside of the muscle-attached region. The SWV of the TCL was significantly smaller without compression (5.21 ± 1.08 m/s) than with compression (6.62 ± 1.18 m/s). The SWV measurements of the skin and the thenar muscles were also affected by transducer compression, but to different extents than the SWV of the TCL. Therefore to standardize the ARFI imaging procedure, it is recommended that a layer of ultrasound gel be maintained to minimize the effects of tissue compression. This study demonstrated the feasibility of ARFI imaging for assessing the stiffness characteristics of the TCL in vivo, which has the potential to identify pathomechanical changes of the tissue. PMID:23861919

  4. The performance of acoustic radiation force impulse imaging in predicting liver fibrosis in chronic liver diseases.

    PubMed

    Lin, Yi-Hung; Yeh, Ming-Lun; Huang, Ching-I; Yang, Jeng-Fu; Liang, Po-Cheng; Huang, Chung-Feng; Dai, Chia-Yen; Lin, Zu-Yau; Chen, Shinn-Cherng; Huang, Jee-Fu; Yu, Ming-Lung; Chuang, Wan-Long

    2016-07-01

    Sonography-based noninvasive liver fibrosis assessment is promising in the prediction of treatment efficacy and prognosis in chronic liver disease (CLD) patients. Acoustic radiation force impulse imaging (ARFI) is a newly-developed transient elastography (TE) method integrated into a conventional ultrasound machine. The study aimed to assess the performance of ARFI imaging in the diagnosis of liver fibrosis in Taiwanese CLD patients. We also aimed to search for the optimal cut-off values in different fibrosis stages. A total of 60 CLD patients (40 males; mean age, 51.8±11 years) were consecutively included. They received standard ARFI measurement within 2 weeks at the time of liver biopsy. There were eight patients with Metavir fibrosis stage 0 (F0), 16 patients with F1, 20 patients with F2, eight patients with F3, and eight patients with F4, respectively. The mean values among patient with F0, F1, F2, F3, and F4 were 1.17±0.13, 1.30±0.17, 1.31±0.24, 2.01±0.45, and 2.69±0.91, respectively (p<0.001). The optimal cut-off ARFI value for significant fibrosis (F≥2) was 1.53 with the accuracy of 0.733, while it was 1.66 for advanced fibrosis (F≥3) with the accuracy of 0.957. Our study demonstrated that ARFI imaging is competent for fibrosis diagnosis, particularly in CLD patients with advanced fibrosis. PMID:27450025

  5. High resolution imaging beyond the acoustic diffraction limit in deep tissue via ultrasound-switchable NIR fluorescence

    NASA Astrophysics Data System (ADS)

    Pei, Yanbo; Wei, Ming-Yuan; Cheng, Bingbing; Liu, Yuan; Xie, Zhiwei; Nguyen, Kytai; Yuan, Baohong

    2014-04-01

    Fluorescence imaging in deep tissue with high spatial resolution is highly desirable because it can provide details about tissue's structural, functional, and molecular information. Unfortunately, current fluorescence imaging techniques are limited either in penetration depth (microscopy) or spatial resolution (diffuse light based imaging) as a result of strong light scattering in deep tissue. To overcome this limitation, we developed an ultrasound-switchable fluorescence (USF) imaging technique whereby ultrasound was used to switch on/off the emission of near infrared (NIR) fluorophores. We synthesized and characterized unique NIR USF contrast agents. The excellent switching properties of these agents, combined with the sensitive USF imaging system developed in this study, enabled us to image fluorescent targets in deep tissue with spatial resolution beyond the acoustic diffraction limit.

  6. Acquisition and analysis of angle-beam wavefield data

    SciTech Connect

    Dawson, Alexander J.; Michaels, Jennifer E.; Levine, Ross M.; Chen, Xin; Michaels, Thomas E.

    2014-02-18

    Angle-beam ultrasonic testing is a common practical technique used for nondestructive evaluation to detect, locate, and characterize a variety of material defects and damage. Greater understanding of the both the incident wavefield produced by an angle-beam transducer and the subsequent scattering from a variety of defects and geometrical features is anticipated to increase the reliability of data interpretation. The focus of this paper is on acquiring and analyzing propagating waves from angle-beam transducers in simple, defect-free plates as a first step in the development of methods for flaw characterization. Unlike guided waves, which excite the plate throughout its thickness, angle-beam bulk waves bounce back and forth between the plate surfaces, resulting in the well-known multiple “skips” or “V-paths.” The experimental setup consists of a laser vibrometer mounted on an XYZ scanning stage, which is programmed to move point-to-point on a rectilinear grid to acquire waveform data. Although laser vibrometry is now routinely used to record guided waves for which the frequency content is below 1 MHz, it is more challenging to acquire higher frequency bulk waves in the 1–10 MHz range. Signals are recorded on the surface of an aluminum plate that were generated from a 5 MHz, 65° refracted angle, shear wave transducer-wedge combination. Data are analyzed directly in the x-t domain, via a slant stack Radon transform in the τ-p (offset time-slowness) domain, and via a 2-D Fourier transform in the ω-k domain, thereby enabling identification of specific arrivals and modes. Results compare well to those expected from a simple ray tracing analysis except for the unexpected presence of a strong Rayleigh wave.

  7. Exploring the Seismic Wavefield with EarthScope's Transportable Array

    NASA Astrophysics Data System (ADS)

    Ammon, C. J.; Lay, T.

    2007-12-01

    The unprecedented aperture and dense station spacing of EarthScope's Transportable Array (TA) provide opportunities to explore subtle features of the seismic wave field using array methods, including stacking to enhance signals from small, distant events, and using spatial animations and slowness spectra to investigate the origin and nature of long-period (tens to hundreds of seconds) seismic coda. We illustrate the TA's capabilities using teleseismic short-period P waves and complete broadband ground motion recordings. The high quality and uniform installation procedures of the TA produce many stations with superb short-period signal- to-noise ratios enabling direct detection of tiny amplitude (~2nm) P-waves from the mb 4.2, 09 October, 2006 North Korean nuclear test. Stacking of many TA signals resolves subtle complexity in the source signals. Guided by seismic wavefield animations from large earthquakes, which display many wavefronts sweeping across the array, visual inspection and seismic slowness spectra of the extended coda resolve off-great circle Rayleigh-wave arrivals. The scattered waves approach the array from preferred directions depending on the source location relative to the TA. For example, scattered signals from the 01 April, 2007 Solomon Islands earthquakes are preferentially located to the west and northwest, with timing that suggests scattering from subduction zones along the margin of the western and north Pacific ocean. For the 16 August, 2007 Central Peru earthquake, Rayleigh wave coda contains significant energy arriving from the north and northeast, scattered near the North American margin. Analysis of scattered arrivals may lead to improved constraints on lateral gradients in lithospheric structures.

  8. 3D Finite-Difference Modeling of Acoustic Radiation from Seismic Sources

    NASA Astrophysics Data System (ADS)

    Chael, E. P.; Aldridge, D. F.; Jensen, R. P.

    2013-12-01

    Shallow seismic events, earthquakes as well as explosions, often generate acoustic waves in the atmosphere observable at local or even regional distances. Recording both the seismic and acoustic signals can provide additional constraints on source parameters such as epicenter coordinates, depth, origin time, moment, and mechanism. Recent advances in finite-difference (FD) modeling methods enable accurate numerical treatment of wave propagation across the ground surface between the (solid) elastic and (fluid) acoustic domains. Using a fourth-order, staggered-grid, velocity-stress FD algorithm, we are investigating the effects of various source parameters on the acoustic (or infrasound) signals transmitted from the solid earth into the atmosphere. Compressional (P), shear (S), and Rayleigh waves all radiate some acoustic energy into the air at the ground surface. These acoustic wavefronts are typically conical in shape, since their phase velocities along the surface exceed the sound speed in air. Another acoustic arrival with a spherical wavefront can be generated from the vicinity of the epicenter of a shallow event, due to the strong vertical ground motions directly above the buried source. Images of acoustic wavefields just above the surface reveal the radiation patterns and relative amplitudes of the various arrivals. In addition, we compare the relative effectiveness of different seismic source mechanisms for generating acoustic energy. For point sources at a fixed depth, double-couples with almost any orientation produce stronger acoustic signals than isotropic explosions, due to higher-amplitude S and Rayleigh waves. Of course, explosions tend to be shallower than most earthquakes, which can offset the differences due to mechanism. Low-velocity material in the shallow subsurface acts to increase vertical seismic motions there, enhancing the coupling to acoustic waves in air. If either type of source breaks the surface (e.g., an earthquake with surface rupture

  9. Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force

    NASA Astrophysics Data System (ADS)

    Nightingale, Kathryn R.; Palmeri, Mark L.; Congdon, Amy N.; Frinkely, Kristin D.; Trahey, Gregg E.

    2001-05-01

    Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.

  10. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    NASA Astrophysics Data System (ADS)

    Cassiède, M.; Shaw, J. M.

    2015-04-01

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [-35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

  11. Non-intrusive, high-resolution, real-time, two-dimensional imaging of multiphase materials using acoustic array sensors

    SciTech Connect

    Cassiède, M.; Shaw, J. M.

    2015-04-15

    Two parallel multi-element ultrasonic acoustic arrays combined with sets of focal laws for acoustic signal generation and a classical tomographic inversion algorithm are used to generate real-time two-dimensional micro seismic acoustic images of multiphase materials. Proof of concept and calibration measurements were performed for single phase and two phase liquids, uniform polyvinyl chloride (PVC) plates, and aluminum cylinders imbedded in PVC plates. Measurement artefacts, arising from the limited range of viewing angles, and the compromise between data acquisition rate and image quality are discussed. The angle range of scanning and the image resolution were varied, and the effects on the quality of the reproduction of the speed of sound profiles of model solids and liquids with known geometries and compositions were analysed in detail. The best image quality results were obtained for a scanning angle range of [−35°, 35°] at a step size of 2.5° post processed to generate images on a 40 μm square grid. The data acquisition time for high quality images with a 30 mm × 40 mm view field is 10 min. Representation of two-phase solids with large differences in speed of sound between phases and where one phase is dispersed in the form of macroscopic objects (greater than 1 mm in diameter) proved to be the most difficult to image accurately. Liquid-liquid and liquid-vapor phase boundaries, in micro porous solids by contrast, were more readily defined. Displacement of air by water and water by heptane in natural porous limestone provides illustrative kinetic examples. Measurement results with these realistic cases demonstrate the feasibility of the technique to monitor in real time and on the micrometer length scale local composition and flow of organic liquids in inorganic porous media, one of many envisioned engineering applications. Improvement of data acquisition rate is an area for future collaborative study.

  12. On the reliability and limitations of the SPAC method with a directional wavefield

    NASA Astrophysics Data System (ADS)

    Luo, Song; Luo, Yinhe; Zhu, Lupei; Xu, Yixian

    2016-03-01

    The spatial autocorrelation (SPAC) method is one of the most efficient ways to extract phase velocities of surface waves from ambient seismic noise. Most studies apply the method based on the assumption that the wavefield of ambient noise is diffuse. However, the actual distribution of sources is neither diffuse nor stationary. In this study, we examined the reliability and limitations of the SPAC method with a directional wavefield. We calculated the SPAC coefficients and phase velocities from a directional wavefield for a four-layer model and characterized the limitations of the SPAC. We then applied the SPAC method to real data in Karamay, China. Our results show that, 1) the SPAC method can accurately measure surface wave phase velocities from a square array with a directional wavefield down to a wavelength of twice the shortest interstation distance; and 2) phase velocities obtained from real data by the SPAC method are stable and reliable, which demonstrates that this method can be applied to measure phase velocities in a square array with a directional wavefield.

  13. Testicular microlithiasis and preliminary experience of acoustic radiation force impulse imaging

    PubMed Central

    Osther, Palle Jørn Sloth; Rafaelsen, Søren Rafael

    2016-01-01

    Background Elastography of the testis can be used as a part of multiparametric examination of the scrotum. Purpose To determine the testicular stiffness using acoustic radiation force impulse imaging (ARFI) technique in men with testicular microlithiasis (TML). Material and Methods In 2013, 12 patients with diagnosed testicular microlithiasis in 2008 (mean age, 51 years; age range, 25–76 years) underwent a 5-year follow-up B-mode ultrasonography with three ARFI elastography measurements of each testis. We used a Siemens Acuson S3000 machine. Results No malignancy was found at the 5-year follow-up B-mode and elastography in 2013. However, we found an increase in TML; in the previous ultrasonography in 2008, eight men had bilateral TML, whereas in 2013, 10 men were diagnosed with bilateral TML. The mean elasticity of testicles with TML was 0.82 m/s (interquartile range [IQR], 0.72–0.88 m/s; range, 65–1.08 m/s). Conclusion Elastography velocity of testis with TML seems to be in the same velocity range as in men with normal testis tissue. PMID:27504193

  14. Super-resolution imaging by resonant tunneling in anisotropic acoustic metamaterials.

    PubMed

    Liu, Aiping; Zhou, Xiaoming; Huang, Guoliang; Hu, Gengkai

    2012-10-01

    The resonant tunneling effects that could result in complete transmission of evanescent waves are examined in acoustic metamaterials of anisotropic effective mass. The tunneling conditions are first derived for the metamaterials composed of classical mass-in-mass structures. It is found that the tunneling transmission occurs when the total length of metamaterials is an integral number of half-wavelengths of the periodic Bloch wave. Due to the local resonance of building units of metamaterials, the Bloch waves are spatially modulated within the periodic structures, leading to the resonant tunneling occurring in the low-frequency region. The metamaterial slab lens with anisotropic effective mass is designed by which the physics of resonant tunneling and the features for evanescent field manipulations are examined. The designed lens interacts with evanescent waves in the way of the propagating wavenumber weakly dependent on the spatial frequency of evanescent waves. Full-wave simulations validate the imaging performance of the proposed lens with the spatial resolution beyond the diffraction limit. PMID:23039546

  15. Reflection-artifact-free photoacoustic imaging using PAFUSion (photoacoustic-guided focused ultrasound)

    NASA Astrophysics Data System (ADS)

    Kuniyil Ajith Singh, Mithun; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-03-01

    Reflection artifacts caused by acoustic inhomogeneities are a main challenge to deep-tissue photoacoustic imaging. Photoacoustic transients generated by the skin surface and superficial vasculature will propagate into the tissue and reflect back from echogenic structures to generate reflection artifacts. These artifacts can cause problems in image interpretation and limit imaging depth. In its basic version, PAFUSion mimics the inward travelling wave-field from blood vessel-like PA sources by applying focused ultrasound pulses, and thus provides a way to identify reflection artifacts. In this work, we demonstrate reflection artifact correction in addition to identification, towards obtaining an artifact-free photoacoustic image. In view of clinical applications, we implemented an improved version of PAFUSion in which photoacoustic data is backpropagated to imitate the inward travelling wave-field and thus the reflection artifacts of a more arbitrary distribution of PA sources that also includes the skin melanin layer. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. We present a phantom experiment and initial in vivo measurements on human volunteers where we demonstrate significant reflection artifact reduction using our technique. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can reduce these artifacts significantly to improve the deep-tissue photoacoustic imaging.

  16. Development and validation of a combined phased acoustical radiosity and image source model for predicting sound fields in rooms.

    PubMed

    Marbjerg, Gerd; Brunskog, Jonas; Jeong, Cheol-Ho; Nilsson, Erling

    2015-09-01

    A model, combining acoustical radiosity and the image source method, including phase shifts on reflection, has been developed. The model is denoted Phased Acoustical Radiosity and Image Source Method (PARISM), and it has been developed in order to be able to model both specular and diffuse reflections with complex-valued and angle-dependent boundary conditions. This paper mainly describes the combination of the two models and the implementation of the angle-dependent boundary conditions. It furthermore describes how a pressure impulse response is obtained from the energy-based acoustical radiosity by regarding the model as being stochastic. Three methods of implementation are proposed and investigated, and finally, recommendations are made for their use. Validation of the image source method is done by comparison with finite element simulations of a rectangular room with a porous absorber ceiling. Results from the full model are compared with results from other simulation tools and with measurements. The comparisons of the full model are done for real-valued and angle-independent surface properties. The proposed model agrees well with both the measured results and the alternative theories, and furthermore shows a more realistic spatial variation than energy-based methods due to the fact that interference is considered. PMID:26428783

  17. Test-bench system for a borehole azimuthal acoustic reflection imaging logging tool

    NASA Astrophysics Data System (ADS)

    Liu, Xianping; Ju, Xiaodong; Qiao, Wenxiao; Lu, Junqiang; Men, Baiyong; Liu, Dong

    2016-06-01

    The borehole azimuthal acoustic reflection imaging logging tool (BAAR) is a new generation of imaging logging tool, which is able to investigate stratums in a relatively larger range of space around the borehole. The BAAR is designed based on the idea of modularization with a very complex structure, so it has become urgent for us to develop a dedicated test-bench system to debug each module of the BAAR. With the help of a test-bench system introduced in this paper, test and calibration of BAAR can be easily achieved. The test-bench system is designed based on the client/server model. The hardware system mainly consists of a host computer, an embedded controlling board, a bus interface board, a data acquisition board and a telemetry communication board. The host computer serves as the human machine interface and processes the uploaded data. The software running on the host computer is designed based on VC++. The embedded controlling board uses Advanced Reduced Instruction Set Machines 7 (ARM7) as the micro controller and communicates with the host computer via Ethernet. The software for the embedded controlling board is developed based on the operating system uClinux. The bus interface board, data acquisition board and telemetry communication board are designed based on a field programmable gate array (FPGA) and provide test interfaces for the logging tool. To examine the feasibility of the test-bench system, it was set up to perform a test on BAAR. By analyzing the test results, an unqualified channel of the electronic receiving cabin was discovered. It is suggested that the test-bench system can be used to quickly determine the working condition of sub modules of BAAR and it is of great significance in improving production efficiency and accelerating industrial production of the logging tool.

  18. A simulation technique for 3D MR-guided acoustic radiation force imaging

    PubMed Central

    Payne, Allison; de Bever, Josh; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.

    2015-01-01

    Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison

  19. A simulation technique for 3D MR-guided acoustic radiation force imaging

    SciTech Connect

    Payne, Allison; Bever, Josh de; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.

    2015-02-15

    Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic radiation force imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the radiation force exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source force acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The radiation force field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the force field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the radiation force of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison

  20. Single- and Multiple- Track Location Shear Wave and Acoustic Radiation Force Impulse Imaging: Matched Comparison of Contrast, CNR, and Resolution

    PubMed Central

    Hollender, Peter J.; Rosenzweig, Stephen J.; Nightingale, Kathryn R.; Trahey, Gregg E.

    2014-01-01

    Acoustic radiation force impulse (ARFI) imaging and shear wave elasticity imaging (SWEI) use the dynamic response of tissue to impulsive mechanical stimulus to characterize local elasticity. A variant of conventional, multiple track location SWEI (MTL-SWEI), denoted single track location SWEI (STL-SWEI) offers the promise of creating speckle-free shear wave images. This work compares the three imaging modalities using a high push and track beam density combined acquisition sequence to image inclusions of different sizes and contrasts. STL-SWEI is shown to have significantly higher CNR than MTL-SWEI, allowing for operation at higher resolution. ARFI and STL-SWEI perform similarly in the larger inclusions, with STL-SWEI providing better visualization of small targets ≤2.5 mm in diameter. The processing of each modality introduces different trade-offs between smoothness and resolution of edges and structures; these are discussed in detail. PMID:25701531

  1. Anisotropic Shear Velocity Models of the North American Upper Mantle Based on Waveform Inversion and Numerical Wavefield Computations.

    NASA Astrophysics Data System (ADS)

    Pierre, C.; Masson, Y.; Romanowicz, B. A.; French, S. W.; Yuan, H.

    2014-12-01

    The Earthscope TA deployment across the continental US now has reached the eastern part of the United States, providing the opportunity for high-resolution 3D seismic velocity imaging of both lithosphere and asthenosphere across the entire north-American continent (NA). Previously (Yuan et al., 2014), we presented a 3D radially anisotropic shear wave model of North America (NA) lithospheric mantle based on full waveform tomography, combining teleseismic and regional distance data sampling the NA. Regional wavefield computations were performed numerically, using a regional Spectral Element code (RegSEM, Cupillard et al., 2012), while teleseismic computations were performed approximately, using non-linear asymptotic coupling theory (NACT, Li and Romanowicz, 1995). For both datasets, the inversion was performed iteratively, using a Gauss-Newton scheme, with kernels computed using either NACT or the surface wave, path average approximation (PAVA), depending on the source-station distance. Building upon our previous work, we here present a new radially anisotropic lithospheric/asthenospheric model of shear velocity for North America based entirely on regional waveforms from an augmented dataset of ~150 events contained and observed inside the study region, with forward wavefield computations performed using RegSEM down to 40s, starting from our most recent whole mantle 3D radially anisotropic shear velocity model (SEMUCB-wm1, French and Romanowicz, 2014). Several iterations of inversion are performed using a Gauss-Newton scheme. We present and compare two models obtained, on the one hand, using NACT/PAVA kernels as in our previous work, and on the other, using hybrid kernels, where the Hessian is computed using NACT/PAVA, but the gradient is computed numerically from the adjoint wavefield, providing more accurate kernels while preserving the fast convergence properties of the Gauss-Newton inversion scheme. We also present an update to our azimuthally anisotropic shear

  2. Toward global waveform tomography of the whole mantle using SEM: Efficient simulation of the global wavefield using a homogenized crust

    NASA Astrophysics Data System (ADS)

    French, S. W.; Lekic, V.; Romanowicz, B. A.

    2010-12-01

    As global waveform-modeling schemes rooted in perturbation theory are supplanted by fully numerical alternatives, such as the Spectral Element Method (e.g. SEM: Komatitsch and Tromp, 2002), the improved wavefield accuracy for complex 3D structures also carries increased computational cost. Lekic and Romanowicz (2010) inverted waveforms of fundamental and higher mode surface waves for a radially anisotropic upper-mantle Vs model using SEM (SEMum). The SEM computations were made feasible by an appropriate choice of cutoff period (T≥ 60 s.), as well as the implementation of a homogenized anisotropic crustal layer based on fitting of short period group velocity dispersion curves. These choices allowed for an efficient SEM mesh undeformed by true Moho topography. Further, instead of homogenization of a possibly biased a priori crustal model, Lekic and Romanowicz jointly inverted for the crustal layer, constrained by surface wave group velocity dispersion maps for T≥ 25 s. We are currently developing a radially anisotropic Vs model of the whole mantle using SEM, following an approach broadly similar to that employed in SEMum. Extension of this methodology to imaging of lower-mantle structure requires the inclusion of a body wave dataset, and thus shorter-period modeling of the global wavefield (T≥ 32 s.). While this period range dictates finer sampling of our SEM mesh, reduced computational cost is still possible through the crustal homogenization scheme. Here, we first discuss the development of an analogous homogenized crustal model and its validity for both the fundamental and higher mode surface wave and the body wave datasets. We focus on maintaining a simplified Moho topography, thus obviating expensive deformation of the SEM mesh, while accurately treating valuable surface-reflected body wave phases (ex: multiple ScS). Second, we discuss implications of treating the crust in this manner for the overall inversion methodology. In particular, we intend to

  3. Elasticity imaging of speckle-free tissue regions with moving acoustic radiation force and phase-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Hsieh, Bao-Yu; Song, Shaozhen; Nguyen, Thu-Mai; Yoon, Soon Joon; Shen, Tueng; Wang, Ruikang; O'Donnell, Matthew

    2016-03-01

    Phase-sensitive optical coherence tomography (PhS-OCT) can be utilized for quantitative shear-wave elastography using speckle tracking. However, current approaches cannot directly reconstruct elastic properties in speckle-less or speckle-free regions, for example within the crystalline lens in ophthalmology. Investigating the elasticity of the crystalline lens could improve understanding and help manage presbyopia-related pathologies that change biomechanical properties. We propose to reconstruct the elastic properties in speckle-less regions by sequentially launching shear waves with moving acoustic radiation force (mARF), and then detecting the displacement at a specific speckle-generating position, or limited set of positions, with PhS-OCT. A linear ultrasound array (with a center frequency of 5 MHz) interfaced with a programmable imaging system was designed to launch shear waves by mARF. Acoustic sources were electronically translated to launch shear waves at laterally shifted positions, where displacements were detected by speckle tracking images produced by PhS-OCT operating in M-B mode with a 125-kHz A-line rate. Local displacements were calculated and stitched together sequentially based on the distance between the acoustic source and the detection beam. Shear wave speed, and the associated elasticity map, were then reconstructed based on a time-of-flight algorithm. In this study, moving-source shear wave elasticity imaging (SWEI) can highlight a stiff inclusion within an otherwise homogeneous phantom but with a CNR increased by 3.15 dB compared to a similar image reconstructed with moving-detector SWEI. Partial speckle-free phantoms were also investigated to demonstrate that the moving-source sequence could reconstruct the elastic properties of speckle-free regions. Results show that harder inclusions within the speckle-free region can be detected, suggesting that this imaging method may be able to detect the elastic properties of the crystalline lens.

  4. Acoustic radiation force impulse imaging for assessing liver fibrosis in alcoholic liver disease

    PubMed Central

    Kiani, Anita; Brun, Vanessa; Lainé, Fabrice; Turlin, Bruno; Morcet, Jeff; Michalak, Sophie; Le Gruyer, Antonia; Legros, Ludivine; Bardou-Jacquet, Edouard; Gandon, Yves; Moirand, Romain

    2016-01-01

    AIM: To evaluate the performance of elastography by ultrasound with acoustic radiation force impulse (ARFI) in determining fibrosis stage in patients with alcoholic liver disease (ALD) undergoing alcoholic detoxification in relation to biopsy. METHODS: Eighty-three patients with ALD undergoing detoxification were prospectively enrolled. Each patient underwent ARFI imaging and a liver biopsy on the same day. Fibrosis was staged according to the METAVIR scoring system. The median of 10 valid ARFI measurements was calculated for each patient. RESULTS: Sixty-nine males and thirteen females (one patient excluded due to insufficient biopsy size) were assessed with a mean alcohol consumption of 132.4 ± 128.8 standard drinks per week and mean cumulative year duration of 17.6 ± 9.5 years. Sensitivity and specificity were respectively 82.4% (0.70-0.95) and 83.3% (0.73-0.94) (AUROC = 0.87) for F ≥ 2 with a cut-off value of 1.63m/s; 82.4% (0.64-1.00) and 78.5% (0.69-0.89) (AUROC = 0.86) for F ≥ 3 with a cut-off value of 1.84m/s; and 92.3% (0.78-1.00] and 81.6% (0.72-0.90) (AUROC = 0.89) for F = 4 with a cut-off value of 1.94 m/s. CONCLUSION: ARFI is an accurate, non-invasive and easy method for assessing liver fibrosis in patients with ALD undergoing alcoholic detoxification. PMID:27239119

  5. Breast Lesions Evaluated by Color-Coded Acoustic Radiation Force Impulse (ARFI) Imaging.

    PubMed

    Zhou, JianQiao; Yang, ZhiFang; Zhan, WeiWei; Zhang, JingWen; Hu, Na; Dong, YiJie; Wang, YingYing

    2016-07-01

    The goal of our study was to investigate the value of color-coded Virtual Touch tissue imaging (VTI) using acoustic radiation force impulse (ARFI) technology in the characterization of breast lesions and to compare it with conventional ultrasound (US). Conventional US and color-coded VTI were performed in 196 solid breast lesions in 196 consecutive women (age range 17-91 y; mean 48.17 ± 14.46 y). A four-point scale VTI score was assigned for each lesion according to the color pattern both in the lesion and in the surrounding breast tissue. The mean VTI score was significantly higher for malignant lesions (3.80 ± 0.66, range 1-4) than for benign ones (2.02 ± 1.20, range 1-4) (p < 0.001), and the optimal cut-off value was between score 3 and score 4. The area under the receiver operating characteristic (ROC) curve for combined conventional US and VTI (0.945) was significantly higher than that for conventional US (0.902) and for VTI (0.871) (p = 0.0021 and p < 0.001, respectively). It was concluded that color-coded VTI with the proposed four-point scale score system combined with conventional US might have the potential to aid in the characterization of benign and malignant breast lesions. PMID:27131841

  6. An analysis and retrofit of the acoustics at Image Creators Health and Beauty Salon

    NASA Astrophysics Data System (ADS)

    Ellis, Donna

    2002-11-01

    This paper discusses the analysis and retrofit of the acoustics in a high-volume beauty salon in Severna Park, MD. The major issues in what was designed to be a serene environment are reverberation times of 1-1.68 s in the mid- to upper-frequency range. Employee and customer complaints include heightened stress, vocal strain, headaches, and poor intelligibility. Existing analysis and acoustical retrofit solutions will be demonstrated.

  7. High-speed imaging, acoustic features, and aeroacoustic computations of jet noise from Strombolian (and Vulcanian) explosions

    NASA Astrophysics Data System (ADS)

    Taddeucci, J.; Sesterhenn, J.; Scarlato, P.; Stampka, K.; Del Bello, E.; Pena Fernandez, J. J.; Gaudin, D.

    2014-05-01

    High-speed imaging of explosive eruptions at Stromboli (Italy), Fuego (Guatemala), and Yasur (Vanuatu) volcanoes allowed visualization of pressure waves from seconds-long explosions. From the explosion jets, waves radiate with variable geometry, timing, and apparent direction and velocity. Both the explosion jets and their wave fields are replicated well by numerical simulations of supersonic jets impulsively released from a pressurized vessel. The scaled acoustic signal from one explosion at Stromboli displays a frequency pattern with an excellent match to those from the simulated jets. We conclude that both the observed waves and the audible sound from the explosions are jet noise, i.e., the typical acoustic field radiating from high-velocity jets. Volcanic jet noise was previously quantified only in the infrasonic emissions from large, sub-Plinian to Plinian eruptions. Our combined approach allows us to define the spatial and temporal evolution of audible jet noise from supersonic jets in small-scale volcanic eruptions.

  8. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion)

    PubMed Central

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-01-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging. PMID:27570690

  9. Polarity-consistent excitation amplitude imaging condition for elastic reverse time migration

    NASA Astrophysics Data System (ADS)

    Du, Qizhen; Zhang, Mingqiang; Gong, Xufei; Chen, Xiaoran

    2015-02-01

    Imaging conditions can not only affect the computational efficiency and storage cost of reverse time migration (RTM) but determine the quality of the final migrated images. This paper extends the idea of the well amplitude-preserved and highly-efficient excitation amplitude imaging condition from acoustic RTM to elastic RTM. For elastic RTM, the maximum amplitude of the separated P-wave and the corresponding image time of each grid point are saved during the forward modeling of the source wavefield and then PP and PS images are obtained by dividing the separated P- and S-waves of the backward-propagated receiver wavefield by the precomputed P-waves at each grid point that satisfies the image time. However, polarity reversals of the PS image will cause destructive interference when the stacked image is needed. In order to solve this problem, we propose the polarity-consistent excitation amplitude imaging condition by combining the excitation amplitude imaging condition with a shot-domain polarity reversal correction method. Then we provide the detailed realization process of this imaging condition in elastic RTM. By utilizing the relatively stable and well amplitude-preserved source-normalized cross-correlation imaging condition as a comparison, we testify to the feasibility and validity of the proposed imaging condition in the aspects of amplitude preservation property, imaging capability of complex structures, storage cost and computational efficiency. Considering the balance between the efficiency and image quality, the polarity-consistent excitation amplitude imaging condition can be a good choice for elastic RTM.

  10. Apparatus for real-time acoustic imaging of Rayleigh-Bénard convection

    SciTech Connect

    Kuehn, Kerry, K.

    2008-10-28

    We have successfully designed, built and tested an experimental apparatus which is capable of providing the first real-time ultrasound images of Rayleigh-B\\'{e}nard convection in optically opaque fluids confined to large aspect ratio experimental cells. The apparatus employs a modified version of a commercially available ultrasound camera to capture images (30 frames per second) of flow patterns in a fluid undergoing Rayleigh Bénard convection. The apparatus was validated by observing convection rolls in 5cSt polydimethylsiloxane (PDMS) polymer fluid. Our first objective, after having built the apparatus, was to use it to study the sequence of transitions from diffusive to time--dependent heat transport in liquid mercury. The aim was to provide important information on pattern formation in the largely unexplored regime of very low Prandtl number fluids. Based on the theoretical stability diagram for liquid mercury, we anticipated that straight rolls should be stable over a range of Rayleigh numbers, between 1708 and approximately 1900. Though some of our power spectral densities were suggestive of the existence of weak convection, we have been unable to unambiguously visualize stable convection rolls above the theoretical onset of convection in liquid mercury. Currently, we are seeking ways to increase the sensitivity of our apparatus, such as (i) improving the acoustic impedance matching between our materials in the ultrasound path and (ii) reducing the noise level in our acoustic images due to turbulence and cavitation in the cooling fluids circulating above and below our experimental cell. If we are able to convincingly improve the sensitivity of our apparatus, and we still do not observe stable convection rolls in liquid mercury, then it may be the case that the theoretical stability diagram requires revision. In that case, either (i) straight rolls are not stable in a large aspect ratio cell at the Prandtl numbers associated with liquid mercury, or (ii) they

  11. Inter-station coda wavefield studies using a novel icequake database on Erebus volcano

    NASA Astrophysics Data System (ADS)

    Chaput, J. A.; Campillo, M.; Roux, P.; Aster, R. C.

    2013-12-01

    Recent theoretical advances pertaining to the properties of multiply scattered wavefields have yielded a plethora of numerical and controlled source studies aiming to better understand what information may be derived from these otherwise chaotic signals. Practically, multiply scattered wavefields are difficult to compare to numerically derived models due to a combination of source paucity/directionality and array density limitations, particularly in passive seismology scenarios. Furthermore, in situations where data quantities are abundant, such as for ambient noise correlations, it remains very difficult to recover pseudo-Green's function symmetry in the ballistic components of the wavefield, let alone in the coda of the correlations. In this study, we use a large network of short period and broadband instruments on Erebus volcano to show that actual Green's function recovery is indeed possible in some cases. We make use of a large database of small impulsive icequakes distributed randomly on the summit plateau and, using fundamental theoretical properties of equipartitioned wavefields and interstation icequake coda correlations, are able to directly derive notoriously difficult quantities such as the bulk elastic mean free path for the volcano, demonstrations of correlation coda symmetry and its dependence on the number of icequakes used, and a theoretically predicted coherent backscattering amplification factor associated with weak localization. We furthermore show that stable equipartition and H^2/V^2 ratios may be consistently observed for icequake coda, and we perform simple depth inversions of these frequency dependent quantities to compare with known structures.

  12. Pre-stack full wavefield inversion for elastic parameters of TI media

    NASA Astrophysics Data System (ADS)

    Zhang, Meigen; Huang, Zhongyu; Li, Xiaofan; Wang, Miaoyue; Xu, Guangyin

    2006-03-01

    Pre-stack full wavefield inversion for the elastic parameters of transversely isotropical media is implemented. The Jacobian matrix is derived directly with the finite element method, just like the full wavefield forward modelling. An absorbing boundary scheme combining Liao's transparent boundary condition with Sarma's attenuation boundary condition is applied to the forward modelling and Jacobian calculation. The input data are the complete ground-recorded wavefields containing full kinematic and dynamic information for the seismic waves. Inversion with such data is desirable as it should improve the accuracy of the estimated parameters and also reduce data pre-processing, such as wavefield identification and separation. A scheme called energy grading inversion is presented to deal with the instability caused by the large energy difference between different arrivals in the input data. With this method, parameters in the shallow areas, which mainly affect wave patterns with strong energy, converge before those of deeper media. Thus, the number of unknowns in each inversion step is reduced, and the stability and reliability of the inversion process is greatly improved. As a result, the scheme is helpful to reduce the non-uniqueness in the inversion. Two synthetic examples show that the inversion system is reliable and accurate even though initial models deviate significantly from the actual models. Also, the system can accurately invert for transversely isotropic model parameters even with the introduction of strong random noise.

  13. Surprises and anomalies in acoustical and optical scattering and radiation forces

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2015-09-01

    Experiments on radiation torques and negative radiation forces by various researchers display how the underlying wave-field geometry influences radiation forces. Other situations strongly influenced by wave-field geometry include high-order caustics present in light-scattering patterns of objects as simple as oblate drops of water or oblate bubbles of air in water. Related theoretical and experimental investigations are considered. Acoustic scattering enhancements associated with various guided waves are also examined. These include guided waves having negative group velocities and guided wave radiating wavefronts having a vanishing Gaussian curvature.

  14. Optical-resolution photoacoustic imaging through thick tissue with a thin capillary as a dual optical-in acoustic-out waveguide

    NASA Astrophysics Data System (ADS)

    Simandoux, Olivier; Stasio, Nicolino; Gateau, Jérome; Huignard, Jean-Pierre; Moser, Christophe; Psaltis, Demetri; Bossy, Emmanuel

    2015-03-01

    We demonstrate the ability to guide high-frequency photoacoustic waves through thick tissue with a water-filled silica-capillary (150 μm inner diameter and 30 mm long). An optical-resolution photoacoustic image of a 30 μm diameter absorbing nylon thread was obtained by guiding the acoustic waves in the capillary through a 3 cm thick fat layer. The transmission loss through the capillary was about -20 dB, much lower than the -120 dB acoustic attenuation through the fat layer. The overwhelming acoustic attenuation of high-frequency acoustic waves by biological tissue can therefore be avoided by the use of a small footprint capillary acoustic waveguide for remote detection. We finally demonstrate that the capillary can be used as a dual optical-in acoustic-out waveguide, paving the way for the development of minimally invasive optical-resolution photoacoustic endoscopes free of any acoustic or optical elements at their imaging tip.

  15. Time-frequency-wavenumber Decomposition To Investigate Seismic Wavefield: Application To The Annot Experiment

    NASA Astrophysics Data System (ADS)

    Schissele, E.; Cansi, Y.; Gaffet, S.

    Many observations and studies as well as numerical simulations have been done in order to completely understand the whole seismogram recorded during an earthquake. At regional distances, the seismic wavefield is strongly influenced by crustal hetero- geneities. The primary wavefield constituted by Pn, Pg, Sn, Sg, Rg, Lg.... phases is diffracted and refracted by these heterogeneities and hence forms the coda of the seis- mogram. But the different mechanisms of propagation in a heterogeneous medium are not fully understood. The identification of the different phases contributing to the coda seems to be essential to progress in the comprehension of the seismic wavefield propagation. Seismic arrays are then well-adapted tools since they provide the spatio-temporal evo- lution of the wavefield. In 1998, 4 small-scales arrays were deployed for 2 months around the Annot region, located in the southern French Alps. Each array was constituted by 9 short-period seismometers, recording frequencies greater than 0.2 Hz. Its aperture was 250 meters, with a minimal distance between 2 adjacent sensors of 20 meters. That allows us to study the seismic wavefield for very low wavelength without any problem of spatial aliasing. It will be interesting to characterize in terms of wavefield deformation the signature of the different kinds of heterogeneities (fault system, topographic relief, impedance contrast...) surrounding this area. We expect the primary wavefield to be diffracted or refracted by all these heterogeneities. A time-frequency-wavenumber technique which allows us to characterize the whole coherent part of the energy which prop- agates through the seismic array has been derived. Such a characterization involves, for each coherent wavelet, an estimate of: (i) an arrival time and a frequency content and (ii) an azimuth and an apparent velocity. This way, the principal phases will be described. What will be more interesting, is the extraction of the deterministic part of the

  16. Acoustic imaging of a duct spinning mode by the use of an in-duct circular microphone array.

    PubMed

    Wei, Qingkai; Huang, Xun; Peers, Edward

    2013-06-01

    An imaging method of acoustic spinning modes propagating within a circular duct simply with surface pressure information is introduced in this paper. The proposed method is developed in a theoretical way and is demonstrated by a numerical simulation case. Nowadays, the measurements within a duct have to be conducted using in-duct microphone array, which is unable to provide information of complete acoustic solutions across the test section. The proposed method can estimate immeasurable information by forming a so-called observer. The fundamental idea behind the testing method was originally developed in control theory for ordinary differential equations. Spinning mode propagation, however, is formulated in partial differential equations. A finite difference technique is used to reduce the associated partial differential equations to a classical form in control. The observer method can thereafter be applied straightforwardly. The algorithm is recursive and, thus, could be operated in real-time. A numerical simulation for a straight circular duct is conducted. The acoustic solutions on the test section can be reconstructed with good agreement to analytical solutions. The results suggest the potential and applications of the proposed method. PMID:23742352

  17. Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method.

    PubMed

    Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping

    2015-05-01

    We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan. PMID:25927794

  18. Imaging and characterizing shear wave and shear modulus under orthogonal acoustic radiation force excitation using OCT Doppler variance method

    PubMed Central

    Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K. Kirk; Zhou, Qifa; Chen, Zhongping

    2015-01-01

    We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan. PMID:25927794

  19. A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing

    NASA Astrophysics Data System (ADS)

    Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Constanciel Colas, Elodie; Drake, James M.

    2016-08-01

    Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum.

  20. Primary biliary cirrhosis degree assessment by acoustic radiation force impulse imaging and hepatic fibrosis indicators

    PubMed Central

    Zhang, Hai-Chun; Hu, Rong-Fei; Zhu, Ting; Tong, Ling; Zhang, Qiu-Qin

    2016-01-01

    AIM: To evaluate the assessment of primary biliary cirrhosis degree by acoustic radiation force impulse imaging (ARFI) and hepatic fibrosis indicators. METHODS: One hundred and twenty patients who developed liver cirrhosis secondary to primary biliary cirrhosis were selected as the observation group, with the degree of patient liver cirrhosis graded by Child-Pugh (CP) score. Sixty healthy individuals were selected as the control group. The four indicators of hepatic fibrosis were detected in all research objects, including hyaluronic acid (HA), laminin (LN), type III collagen (PC III), and type IV collagen (IV-C). The liver parenchyma hardness value (LS) was then measured by ARFI technique. LS and the four indicators of liver fibrosis (HA, LN, PC III, and IV-C) were observed in different grade CP scores. The diagnostic value of LS and the four indicators of liver fibrosis in determining liver cirrhosis degree with PBC, whether used alone or in combination, were analyzed by receiver operating characteristic (ROC) curve. RESULTS: LS and the four indicators of liver fibrosis within the three classes (A, B, and C) of CP scores in the observation group were higher than in the control group, with C class > B class > A class; the differences were statistically significant (P < 0.01). Although AUC values of LS within the three classes of CP scores were higher than in the four indicators of liver fibrosis, sensitivity and specificity were unstable. The ROC curves of LS combined with the four indicators of liver fibrosis revealed that: AUC and sensitivity in all indicators combined in the A class of CP score were higher than in LS alone, albeit with slightly decreased specificity; AUC and specificity in all indicators combined in the B class of CP score were higher than in LS alone, with unchanged sensitivity; AUC values (0.967), sensitivity (97.4%), and specificity (90%) of all indicators combined in the C class of CP score were higher than in LS alone (0.936, 92.1%, 83

  1. A rapid magnetic resonance acoustic radiation force imaging sequence for ultrasonic refocusing.

    PubMed

    Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Colas, Elodie Constanciel; Drake, James M

    2016-08-01

    Magnetic resonance guided acoustic radiation force imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In addition, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum. PMID:27401452

  2. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2001-07-01

    Mechanically weak formations, such as chalks, high porosity sandstones, and marine sediments, pose significant problems for oil and gas operators. Problems such as compaction, subsidence, and loss of permeability can affect reservoir production operations. For example, the unexpected subsidence of the Ekofisk chalk in the North Sea required over one billion dollars to re-engineer production facilities to account for losses created during that compaction (Sulak 1991). Another problem in weak formations is that of shallow water flows (SWF). Deep water drilling operations sometimes encounter cases where the marine sediments, at shallow depths just below the seafloor, begin to uncontrollably flow up and around the drill pipe. SWF problems created a loss of $150 million for the Ursa development project in the U.S. Gulf Coast SWF (Furlow 1998a,b; 1999a,b). The goal of this project is to provide a database on both the rock mechanical properties and the geophysical properties of weak rocks and sediments. These could be used by oil and gas companies to detect, evaluate, and alleviate potential production and drilling problems. The results will be useful in, for example, pre-drill detection of events such as SWF's by allowing a correlation of seismic data (such as hazard surveys) to rock mechanical properties. The data sets could also be useful for 4-D monitoring of the compaction and subsidence of an existing reservoir and imaging the zones of damage. During the second quarter of the project the research team has: (1) completed acoustic sensor construction, (2) conducted reconnaissance tests to map the deformational behaviors of the various rocks, (3) developed a sample assembly for the measurement of dynamic elastic and poroelastic parameters during triaxial testing, and (4) conducted a detailed review of the scientific literature and compiled a bibliography of that review. During the first quarter of the project the research team acquired several rock types for testing

  3. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor ... Acoustic neuromas have been linked with the genetic disorder neurofibromatosis type 2 (NF2). Acoustic neuromas are uncommon.

  4. Integration of acoustic radiation force and optical imaging for blood plasma clot stiffness measurement.

    PubMed

    Wang, Caroline W; Perez, Matthew J; Helmke, Brian P; Viola, Francesco; Lawrence, Michael B

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood's transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  5. Integration of Acoustic Radiation Force and Optical Imaging for Blood Plasma Clot Stiffness Measurement

    PubMed Central

    Wang, Caroline W.; Perez, Matthew J.; Helmke, Brian P.; Viola, Francesco; Lawrence, Michael B.

    2015-01-01

    Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood’s transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic radiation force (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic radiation force allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic radiation force microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic radiation force based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775

  6. Acoustic profiles and images of the Palos Verdes Margin: Implications concerning deposition from the White's Point outfall

    SciTech Connect

    Hampton, M A.; Karl, H; Murray, Christopher J. )

    2001-12-01

    Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km{sup 2}, which encompasses a volume of about 3.2 million m{sup 3}. The deposit's basal reflector is acoustically distinct over most of the mapped area, implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30 m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs.

  7. Acoustic profiles and images of the Palos Verdes margin: Implications concerning deposition from the White's Point outfall

    USGS Publications Warehouse

    Hampton, M.A.; Karl, Herman A.; Murray, C.J.

    2002-01-01

    Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes Shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km2, which encompasses a volume of about 3.2 million m3. The deposit's basal reflector is acoustically distinct over most of the mapped area. implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs. ?? 2002 Elsevier Science Ltd. All rights

  8. Investigations into Ebb Tidal Fronts Using in Situ Acoustic Backscatter and Optical Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Sun, D.; Ortiz-Suslow, D. G.; Haus, B. K.; Laxague, N.; Graber, H. C.; Hargrove, J.; Williams, N. J.

    2014-12-01

    The Office of Naval Research sponsored the Riverine and Estuarine Transport (RIVET) experiment during May 2012 at New River Inlet, North Carolina, in an effort to better understand the complex wave-current-wind interactions typical of tidal inlets. Over the course of a month, this highly sheared zone was intensely sampled with an array of Eulerian and Lagrangian instruments, in part, as a means of creating a synoptic, three-dimensional data set for validating various satellite remote sensing platforms. A component of this project was to deploy the Surface Physics Experimental Catamaran (SPEC), which is a mobile vessel designed specifically for collecting detailed meteorological and oceanographic data in coastal waters. Among its suite of instruments, SPEC was outfitted with a pair of acoustic doppler velocimeters (ADV), an acoustic doppler current profiler (ADCP), and an optical backscatter sensor (OBS). This instrument package allowed for high resolution mapping of the acoustic signature of the ebb tidal plume and the sub-surface, two-dimensional flow field. On May 8th, at 18:40 UTC, a panchromatic satellite image with a 0.6 m resolution, covering 122 km2, was taken of the New River Inlet Estuary and the inner shelf waters just off-shore. Numerous interesting features are visible in the image, such as the river outflow plume, surface streaks and slicks, a complex wave-field, and a remnant frontal edge from the past ebb tide. Interpretation of the surface features in these types of optical images remains a significant challenge and we have used data collected by SPEC immediately after the image acquisition to help illuminate the processes underlying these signatures.

  9. Clinical feasibility study of combined opto-acoustic and ultrasonic imaging modality providing coregistered functional and anatomical maps of breast tumors

    NASA Astrophysics Data System (ADS)

    Zalev, Jason; Clingman, Bryan; Smith, Remie J.; Herzog, Don; Miller, Tom; Stavros, A. Thomas; Ermilov, Sergey; Conjusteau, André; Tsyboulski, Dmitri; Oraevsky, Alexander A.; Kist, Kenneth; Dornbluth, N. C.; Otto, Pamela

    2013-03-01

    We report on findings from the clinical feasibility study of the ImagioTM. Breast Imaging System, which acquires two-dimensional opto-acoustic (OA) images co-registered with conventional ultrasound using a specialized duplex hand-held probe. Dual-wavelength opto-acoustic technology is used to generate parametric maps based upon total hemoglobin and its oxygen saturation in breast tissues. This may provide functional diagnostic information pertaining to tumor metabolism and microvasculature, which is complementary to morphological information obtained with conventional gray-scale ultrasound. We present co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical feasibility study. The clinical results illustrate that the technology may have the capability to improve the efficacy of breast tumor diagnosis. In doing so, it may have the potential to reduce biopsies and to characterize cancers that were not seen well with conventional gray-scale ultrasound alone.

  10. Comparison of temporal and spectral scattering methods using acoustically large breast models derived from magnetic resonance images

    PubMed Central

    Hesford, Andrew J.; Tillett, Jason C.; Astheimer, Jeffrey P.; Waag, Robert C.

    2014-01-01

    Accurate and efficient modeling of ultrasound propagation through realistic tissue models is important to many aspects of clinical ultrasound imaging. Simplified problems with known solutions are often used to study and validate numerical methods. Greater confidence in a time-domain k-space method and a frequency-domain fast multipole method is established in this paper by analyzing results for realistic models of the human breast. Models of breast tissue were produced by segmenting magnetic resonance images of ex vivo specimens into seven distinct tissue types. After confirming with histologic analysis by pathologists that the model structures mimicked in vivo breast, the tissue types were mapped to variations in sound speed and acoustic absorption. Calculations of acoustic scattering by the resulting model were performed on massively parallel supercomputer clusters using parallel implementations of the k-space method and the fast multipole method. The efficient use of these resources was confirmed by parallel efficiency and scalability studies using large-scale, realistic tissue models. Comparisons between the temporal and spectral results were performed in representative planes by Fourier transforming the temporal results. An RMS field error less than 3% throughout the model volume confirms the accuracy of the methods for modeling ultrasound propagation through human breast. PMID:25096103

  11. Comparison of temporal and spectral scattering methods using acoustically large breast models derived from magnetic resonance images.

    PubMed

    Hesford, Andrew J; Tillett, Jason C; Astheimer, Jeffrey P; Waag, Robert C

    2014-08-01

    Accurate and efficient modeling of ultrasound propagation through realistic tissue models is important to many aspects of clinical ultrasound imaging. Simplified problems with known solutions are often used to study and validate numerical methods. Greater confidence in a time-domain k-space method and a frequency-domain fast multipole method is established in this paper by analyzing results for realistic models of the human breast. Models of breast tissue were produced by segmenting magnetic resonance images of ex vivo specimens into seven distinct tissue types. After confirming with histologic analysis by pathologists that the model structures mimicked in vivo breast, the tissue types were mapped to variations in sound speed and acoustic absorption. Calculations of acoustic scattering by the resulting model were performed on massively parallel supercomputer clusters using parallel implementations of the k-space method and the fast multipole method. The efficient use of these resources was confirmed by parallel efficiency and scalability studies using large-scale, realistic tissue models. Comparisons between the temporal and spectral results were performed in representative planes by Fourier transforming the temporal results. An RMS field error less than 3% throughout the model volume confirms the accuracy of the methods for modeling ultrasound propagation through human breast. PMID:25096103

  12. Experimental Study of High-Range-Resolution Medical Acoustic Imaging for Multiple Target Detection by Frequency Domain Interferometry

    NASA Astrophysics Data System (ADS)

    Kimura, Tomoki; Taki, Hirofumi; Sakamoto, Takuya; Sato, Toru

    2009-07-01

    We employed frequency domain interferometry (FDI) for use as a medical acoustic imager to detect multiple targets with high range resolution. The phase of each frequency component of an echo varies with the frequency, and target intervals can be estimated from the phase variance. This processing technique is generally used in radar imaging. When the interference within a range gate is coherent, the cross correlation between the desired signal and the coherent interference signal is nonzero. The Capon method works under the guiding principle that output power minimization cancels the desired signal with a coherent interference signal. Therefore, we utilize frequency averaging to suppress the correlation of the coherent interference. The results of computational simulations using a pseudoecho signal show that the Capon method with adaptive frequency averaging (AFA) provides a higher range resolution than a conventional method. These techniques were experimentally investigated and we confirmed the effectiveness of the proposed method of processing by FDI.

  13. Evidence from acoustic imaging for submarine volcanic activity in 2012 off the west coast of El Hierro (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Pérez, Nemesio M.; Somoza, Luis; Hernández, Pedro A.; de Vallejo, Luis González; León, Ricardo; Sagiya, Takeshi; Biain, Ander; González, Francisco J.; Medialdea, Teresa; Barrancos, José; Ibáñez, Jesús; Sumino, Hirochika; Nogami, Kenji; Romero, Carmen

    2014-12-01

    We report precursory geophysical, geodetic, and geochemical signatures of a new submarine volcanic activity observed off the western coast of El Hierro, Canary Islands. Submarine manifestation of this activity has been revealed through acoustic imaging of submarine plumes detected on the 20-kHz chirp parasound subbottom profiler (TOPAS PS18) mounted aboard the Spanish RV Hespérides on June 28, 2012. Five distinct "filament-shaped" acoustic plumes emanating from the flanks of mounds have been recognized at water depth between 64 and 88 m on a submarine platform located NW El Hierro. These plumes were well imaged on TOPAS profiles as "flares" of high acoustic contrast of impedance within the water column. Moreover, visible plumes composed of white rafts floating on the sea surface and sourcing from the location of the submarine plumes were reported by aerial photographs on July 3, 2012, 5 days after acoustic plumes were recorded. In addition, several geophysical and geochemical data support the fact that these submarine vents were preceded by several precursory signatures: (i) a sharp increase of the seismic energy release and the number of daily earthquakes of magnitude ≥2.5 on June 25, 2012, (ii) significant vertical and horizontal displacements observed at the Canary Islands GPS network (Nagoya University-ITER-GRAFCAN) with uplifts up to 3 cm from June 25 to 26, 2012, (iii) an anomalous increase of the soil gas radon activity, from the end of April until the beginning of June reaching peak values of 2.7 kBq/m3 on June 3, 2012, and (iv) observed positive peak in the air-corrected value of 3He/4He ratio monitored in ground waters (8.5 atmospheric 3He/4He ratio ( R A)) at the northwestern El Hierro on June 16, 2012. Combining these submarine and subaerial information, we suggest these plumes are the consequence of submarine vents exhaling volcanic gas mixed with fine ash as consequence of an event of rapid rise of volatile-rich magma beneath the NW submarine ridge

  14. The Acoustic Lens Design and in Vivo Use of a Multifunctional Catheter Combining Intracardiac Ultrasound Imaging and Electrophysiology Sensing

    PubMed Central

    Stephens, Douglas N.; Cannata, Jonathan; Liu, Ruibin; Zhao, Jian Zhong; Shung, K. Kirk; Nguyen, Hien; Chia, Raymond; Dentinger, Aaron; Wildes, Douglas; Thomenius, Kai E.; Mahajan, Aman; Shivkumar, Kalyanam; Kim, Kang; O’Donnell, Matthew; Sahn, David

    2009-01-01

    A multifunctional 9F intracardiac imaging and electrophysiology mapping catheter was developed and tested to help guide diagnostic and therapeutic intracardiac electrophysiology (EP) procedures. The catheter tip includes a 7.25-MHz, 64-element, side-looking phased array for high resolution sector scanning. Multiple electrophysiology mapping sensors were mounted as ring electrodes near the array for electrocardiographic synchronization of ultrasound images. The catheter array elevation beam performance in particular was investigated. An acoustic lens for the distal tip array designed with a round cross section can produce an acceptable elevation beam shape; however, the velocity of sound in the lens material should be approximately 155 m/s slower than in tissue for the best beam shape and wide bandwidth performance. To help establish the catheter’s unique ability for integration with electrophysiology interventional procedures, it was used in vivo in a porcine animal model, and demonstrated both useful intracardiac echocardiographic visualization and simultaneous 3-D positional information using integrated electroanatomical mapping techniques. The catheter also performed well in high frame rate imaging, color flow imaging, and strain rate imaging of atrial and ventricular structures. PMID:18407850

  15. On the seismic noise wavefield in a weakly dissipative layered Earth

    NASA Astrophysics Data System (ADS)

    Lunedei, Enrico; Albarello, Dario

    2009-06-01

    Proceeding on the assumption that the seismic noise wavefield mainly consists of surface waves generated by a random distribution of independent, point-like and harmonic sources, we modelled a set of relationships that allows us to interpret empirical H/V and apparent dispersion curves in terms of the dynamic properties of a viscoelastic layered Earth. This formalization can be used to determine the effect of material damping on the expected noise wavefield in cases where the sources are relatively distant from the receivers and where the frequencies taken into account are higher than the fundamental resonance frequency of the local subsoil. Numerical experiments indicate that such effects are significant on the H/V ratio curve, whereas the apparent dispersion curve appears to be less strongly influenced by damping. This finding opens new perspectives for the use of noise measurements to infer the in situ anelastic properties of subsoil from passive seismic measurements made at the surface.

  16. Effects of using inclined parametric echosounding on sub-bottom acoustic imaging and advances in buried object detection

    NASA Astrophysics Data System (ADS)

    Schneider von Deimling, Jens; Held, Philipp; Feldens, Peter; Wilken, Dennis

    2016-04-01

    This study reports an adaptation of a parametric echosounder system using 15 kHz as secondary frequency to investigate the angular response of sub-bottom backscatter strength of layered mud, providing a new method for enhanced acoustic detection of buried targets. Adaptions to achieve both vertical (0°) and non-vertical inclination (1-15°, 30°, 45° and 60°) comprise mechanical tilting of the acoustic transducer and electronic beam steering. Data were acquired at 18 m water depth at a study site characterized by a flat, muddy seafloor where a 0.1 m diameter power cable lies 1-2 m below the seafloor. Surveying the cable with vertical incidence revealed that the buried cable can hardly be discriminated against the backscatter strength of the layered mud. However, the backscatter strength of layered mud decreases strongly at >3±0.5° incidence and the layered mud echo pattern vanishes beyond 5°. As a consequence, the backscatter pattern of the buried cable is very pronounced in acoustic images gathered at 15°, 30°, 45° and 60° incidence. The size of the cable echo pattern increases linearly with incidence. These effects are attributed to reflection loss from layered mud at larger incidence and to the scattering of the 0.1 m diameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to 2.6-fold increase of the signal-to-noise ratio at 40° incidence compared to the vertical incidence case.

  17. Investigation of the acoustic field in a standing wave thermoacoustic refrigerator using time-resolved particule image velocimetry

    NASA Astrophysics Data System (ADS)

    Blanc-Benon, Ph.; Poignand, G.; Jondeau, E.

    2012-09-01

    In thermoacoustic devices, the full understanding of the heat transfer between the stack and the heat exchangers is a key issue to improve the global efficiency of these devices. The goal of this paper is to investigate the vortex structures, which appear at the stack plates extremities and may impact the heat transfer. Here, the aerodynamic field between a stack and a heat exchanger is characterised with a time-resolved particle image velocimetry (TR- PIV) set-up. Measurements are performed in a standing wave thermoacoustic refrigerator operating at a frequency of 200 Hz. The employed TR-PIV set-up offers the possibility to acquire 3000 instantaneous velocity fields at a frequency of 3125 Hz (15 instantaneous velocity fields per acoustic period). Measurements show that vortex shedding can occur at high pressure level, when a nonlinear acoustic regime preveals, leading to an additional heating generated by viscous dissipation in the gap between the stack and the heat exchangers and a loss of efficiency.

  18. Detecting the activation of a self-healing mechanism in concrete by acoustic emission and digital image correlation.

    PubMed

    Tsangouri, E; Aggelis, D G; Van Tittelboom, K; De Belie, N; Van Hemelrijck, D

    2013-01-01

    Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process. PMID:24381518

  19. Amplitude-Preserving Propagator and its Applications in Computational Wave Propagation and Seismic Imaging

    NASA Astrophysics Data System (ADS)

    Eslaminia, Mehran

    A novel method is developed to approximately solve acoustic wave equation in the frequency domain. The key idea of the method is to partition the domain into smaller subdomains and solve for the wavefield in each subdomain sequentially, which is facilitated by special interface (continuity) conditions. The sequential solution is performed in two steps: First the downward propagating wavefield is computed considering only downward propagation and transmission at the interfaces. The wavefield is then corrected by adding the upward propagating wavefield resulting from reflections and body forces. It is shown that the proposed method results in accurate amplitudes for downward propagation and primary reflections and is hence called the Amplitude-Preserving Propagator. This novel wave propagator leads to three disparate contributions in large scale computational wave modeling and seismic imaging: forward modeling, migration imaging and full waveform inversion. Forward Modeling: The amplitude-preserving propagator is implemented as a preconditioner to iteratively solve the Helmholtz equation. The effectiveness of the proposed preconditioner is studied using various numerical experiments. We show three significant properties of the proposed preconditioner. First, number of iterations grows very slowly with increasing frequency which is a significant advantage compared to other methods, e.g. sweeping preconditioner. Second, the mesh size (i.e. number of elements per wavelength) does not change number of iterations. Third, and the most important one, the computational time is much less than many other preconditioners. Migration Imaging: In the context of migration imaging, the amplitude-preserving propagator is implemented as an efficient forward solver to perform wave propagation simulation in the frequency domain. We show that the propagator results in a new migration algorithm that is almost as accurate as full-wave migration, while being significantly more efficient

  20. Compressive sensing beamforming based on covariance for acoustic imaging with noisy measurements.

    PubMed

    Zhong, Siyang; Wei, Qingkai; Huang, Xun

    2013-11-01

    Compressive sensing, a newly emerging method from information technology, is applied to array beamforming and associated acoustic applications. A compressive sensing beamforming method (CSB-II) is developed based on sampling covariance matrix, assuming spatially sparse and incoherent signals, and then examined using both simulations and aeroacoustic measurements. The simulation results clearly show that the proposed CSB-II method is robust to sensing noise. In addition, aeroacoustic tests of a landing gear model demonstrate the good performance in terms of resolution and sidelobe rejection. PMID:24181989

  1. Experimental demonstration of passive acoustic imaging in the human skull cavity using CT-based aberration corrections

    PubMed Central

    Jones, Ryan M.; O’Reilly, Meaghan A.; Hynynen, Kullervo

    2015-01-01

    Purpose: Experimentally verify a previously described technique for performing passive acoustic imaging through an intact human skull using noninvasive, computed tomography (CT)-based aberration corrections Jones et al. [Phys. Med. Biol. 58, 4981–5005 (2013)]. Methods: A sparse hemispherical receiver array (30 cm diameter) consisting of 128 piezoceramic discs (2.5 mm diameter, 612 kHz center frequency) was used to passively listen through ex vivo human skullcaps (n = 4) to acoustic emissions from a narrow-band fixed source (1 mm diameter, 516 kHz center frequency) and from ultrasound-stimulated (5 cycle bursts, 1 Hz pulse repetition frequency, estimated in situ peak negative pressure 0.11–0.33 MPa, 306 kHz driving frequency) Definity™ microbubbles flowing through a thin-walled tube phantom. Initial in vivo feasibility testing of the method was performed. The performance of the method was assessed through comparisons to images generated without skull corrections, with invasive source-based corrections, and with water-path control images. Results: For source locations at least 25 mm from the inner skull surface, the modified reconstruction algorithm successfully restored a single focus within the skull cavity at a location within 1.25 mm from the true position of the narrow-band source. The results obtained from imaging single bubbles are in good agreement with numerical simulations of point source emitters and the authors’ previous experimental measurements using source-based skull corrections O’Reilly et al. [IEEE Trans. Biomed. Eng. 61, 1285–1294 (2014)]. In a rat model, microbubble activity was mapped through an intact human skull at pressure levels below and above the threshold for focused ultrasound-induced blood–brain barrier opening. During bursts that led to coherent bubble activity, the location of maximum intensity in images generated with CT-based skull corrections was found to deviate by less than 1 mm, on average, from the position

  2. Enhanced delivery of gold nanoparticles by acoustic cavitation for photoacoustic imaging and photothermal therapy

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Hsin; Liao, Ai-Ho; Lin, Jia-Yu; Lee, Cheng-Ru; Wu, Cheng-Ham; Liu, Tzu-Min; Wang, Churng-Ren; Li, Pai-Chi

    2013-03-01

    Gold-nanorods incorporated with microbubbles (AuMBs) were introduced as a photoacoustic/ultrasound dual- modality contrast agent in our previous study. The application can be extended to theragnosis purpose. With the unique physical characteristics of AuMBs, we propose an enhanced delivery method for the encapsulated particles. For example, laser thermotherapy mediated by plasmonic nanoparticles can be made more effective by using microbubbles as a targeted carrier and acoustic cavitation for enhanced sonoporation. The hypothesis was experimentally tested. Firts, these AuMBs first act as molecular probes with binding to specific ligands. The improved targeting efficacy was macroscopically observed by an ultrasound system. The extended retention of targeted AuMB was observed and recorded for 30 minutes in a CT-26 tumor bearing mouse. Secondly, cavitation induced by time-varying acoustic field was also applied to disrupt the microbubbles and cause increased transient cellular permeability (a.k.a., sonoporation). Multimodal optical microscope based on a Cr:forsterite laser was used to directly observe these effects. The microscope can acquired third-harmonic generation (THG) and two-photon fluorescent (2PF) signals produced by the AuMBs. In vitro examination shows approximately a 60% improvement in terms of fluorescence signals from the cellular uptake of gold nanoparticles after sonoporation treatment. Therefore, we conclude that the controlled release is feasible and can further improve the therapeutic effects of the nanoparticles.

  3. The Broad-Band Seismic Noise Wavefield at the Larderello-Travale Geothermal Field (Italy)

    NASA Astrophysics Data System (ADS)

    Zupo, M.; Saccorotti, G.; Piccinini, D.

    2013-12-01

    Cross-correlation of ambient noise wave-field between a pair of receivers (NCF), provides an estimate of the Green's Function between the two sites, thus allowing extraction of the associated group velocity dispersion curve. This is valid under the assumption that noise sources and/or scatterers are isotropically distributed and uncorrelated each other. These conditions are usually met once the cross-correlations are averaged over long time intervals. At frequencies lower than 1 Hz, ambient noise wavefield is essentially composed by surface waves that are mostly associated with oceanic sources; as a consequence, the noise wavefield may exhibit marked directional properties over short (day) to intermediate (weeks) time scales. A detailed assessment of the nature and duration of these sources is therefore required in order to define the optimal conditions for retrieving the Green's functions from NCF analysis. This study presents ambient noise analysis for the Larderello-Travale Geothermal Field (Italy). We use data collected by a temporary seismic array consisting of 20 broad-band instruments, with station spacing ranging from 6 to 50 Km. Below 1 Hz, the most energetic sources are those associated with both primary and secondary microseisms, with dominant spectral peaks spanning the 0.05-0.5 Hz frequency range. Focusing on the secondary microseism sources (f > 0.1 Hz), we test the validity of the isotropic-wavefield assumption by determining the kinematic properties of the wavefield using frequency-domain beamforming. For the May-November 2012 time span, our results show that the most energetic and persistent wavefield components propagate from WNW (Gulf of Marseille and Genova) and SW (Sardinia channel). In the late part of the observation period, additional wavefield components are observed to propagate from the NE-SE azimuthal range, corresponding to sources located throughout the Adriatic sea. This suggests that the conditions for the application of the NCF

  4. Near-infrared absorbing polymer nano-particle as a sensitive contrast agent for photo-acoustic imaging.

    PubMed

    Aoki, Hiroyuki; Nojiri, Mayumi; Mukai, Rieko; Ito, Shinzaburo

    2015-01-01

    Polymer nano-particles (PNPs) with a near-infrared (NIR) light absorption were prepared by the nano-emulsion method to develop contrast agents for photo-acoustic (PA) imaging. The PNP containing silicon naphthalocyanine showed a high absorption coefficient up to 10(10) M(-1) cm(-1). This is comparable to plasmonic gold nano-particles, which have been studied as PA contrast agents. For the PNP larger than 100 nm, the enhancement of the PA signal was observed compared to the gold nano-particle with a similar absorption coefficient and size. In the case of the PNP, the heat by the light absorption is confined in the particle due to the low thermal diffusivity of polymer materials. We showed that the strong thermal confinement effect of PNP results in the enhancement of the efficiency of the PA signal generation and that the PA intensity can be enhanced by the increase of the Grüneisen parameter of the matrix polymer of PNP. The PA signal from the PNP of poly(methyl methacrylate) was 9-fold larger than that of gold nano-particles with the same absorption coefficient. We demonstrated that in the in vivo PA imaging the detection limit of PNP was of the order of 10(-13) M. The NIR absorbing PNP will be a promising candidate of a sensitive contrast agent for PA imaging. PMID:25407911

  5. Gas-coupled laser acoustic detection as a non-contact line detector for photoacoustic and ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Johnson, Jami L.; van Wijk, Kasper; Caron, James N.; Timmerman, Miriam

    2016-02-01

    Conventional contacting transducers for ultrasonic wave detection are highly sensitive and tuned for real-time imaging with fixed array geometries. However, optical detection provides an alternative to contacting transducers when a small sensor footprint, a large frequency bandwidth, or non-contacting detection is required. Typical optical detection relies on a Doppler-shifted reflection of light from the target, but gas coupled-laser acoustic detection (GCLAD) provides an alternative optical detection method for photoacoustic (PA) and ultrasound imaging that does not involve surface reflectivity. Instead, GCLAD is a line-detector that measures the deflection of an optical beam propagating parallel to the sample, as the refractive index of the air near the sample is affected by particle displacement on the sample surface. We describe the underlying principles of GCLAD and derive a formula for quantifying the surface displacement from a remote GCLAD measurement. We discuss a design for removing the location-dependent displacement bias along the probe beam and a method for measuring the attenuation coefficient of the surrounding air. GCLAD results are used to quantify the surface displacement in a laser-ultrasound experiment, which shows 94% agreement to line-integrated data from a commercial laser vibrometer point detector. Finally, we demonstrate the feasibility of PA imaging of an artery-sized absorber using a detector 5.8 cm from a phantom surface.

  6. Reducing the Impacts of Hydroelectric Dams on Juvenile Anadromous Fishes: Bioengineering Evaluations Using Acoustic Imaging in the Columbia River, USA

    SciTech Connect

    Johnson, Gary E.; Ploskey, Gene R.; Hedgepeth, J.; Khan, Fenton; Mueller, Robert P.; Nagy, William T.; Richmond, Marshall C.; Weiland, Mark A.

    2008-07-29

    Dams impact the survival of juvenile anadromous fishes by obstructing migration corridors, lowering water quality, delaying migrations, and entraining fish in turbine discharge. To reduce these impacts, structural and operational modifications to dams— such as voluntary spill discharge, turbine intake guidance screens, and surface flow outlets—are instituted. Over the last six years, we have used acoustic imaging technology to evaluate the effects of these modifications on fish behavior, passage rates, entrainment zones, and fish/flow relationships at hydroelectric projects on the Columbia River. The imaging technique has evolved from studies documenting simple movement patterns to automated tracking of images to merging and analysis with concurrent hydraulic data. This chapter chronicles this evolution and shows how the information gleaned from the scientific evaluations has been applied to improve passage conditions for juvenile salmonids. We present data from Bonneville and The Dalles dams that document fish behavior and entrainment zones at sluiceway outlets (14 to 142 m3/s), fish passage rates through a gap at a turbine intake screen, and the relationship between fish swimming effort and hydraulic conditions. Dam operators and fisheries managers have applied these data to support decisions on operational and structural changes to the dams for the benefit of anadromous fish populations in the Columbia River basin.

  7. Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface.

    PubMed

    Xie, Yangbo; Wang, Wenqi; Chen, Huanyang; Konneker, Adam; Popa, Bogdan-Ioan; Cummer, Steven A

    2014-01-01

    Metasurfaces are a family of novel wavefront-shaping devices with planar profile and subwavelength thickness. Acoustic metasurfaces with ultralow profile yet extraordinary wave manipulating properties would be highly desirable for improving the performance of many acoustic wave-based applications. However, designing acoustic metasurfaces with similar functionality to their electromagnetic counterparts remains challenging with traditional metamaterial design approaches. Here we present a design and realization of an acoustic metasurface based on tapered labyrinthine metamaterials. The demonstrated metasurface can not only steer an acoustic beam as expected from the generalized Snell's law, but also exhibits various unique properties such as conversion from propagating wave to surface mode, extraordinary beam-steering and apparent negative refraction through higher-order diffraction. Such designer acoustic metasurfaces provide a new design methodology for acoustic signal modulation devices and may be useful for applications such as acoustic imaging, beam steering, ultrasound lens design and acoustic surface wave-based applications. PMID:25418084

  8. Localized acoustic surface modes

    NASA Astrophysics Data System (ADS)

    Farhat, Mohamed; Chen, Pai-Yen; Bağcı, Hakan

    2016-04-01

    We introduce the concept of localized acoustic surface modes. We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.

  9. Opto-acoustic imaging system for early breast cancer diagnostics: experimental and numerical studies

    NASA Astrophysics Data System (ADS)

    Khokhlova, Tanya D.; Zharinov, Alexei M.; Kozhushko, Viktor V.; Pelivanov, Ivan M.; Karabutov, Alexander A.

    2006-03-01

    Optoacoustic (OA) imaging is based on the generation of thermoelastic stress waves by heating an object in an optically heterogeneous medium with a short laser pulse. The stress waves contain information on the distribution of structures with enhanced optical absorption that can be used for early cancer diagnostics. This technique has already been applied in-vivo for breast cancer diagnostics and yielded higher contrast of obtained images than that of X-ray or ultrasonic images. The resolution was comparable with that yielded by ultrasonic imaging. Therefore, OA imaging is a very promising technique and it is being rapidly developed. Research in the area is now mostly targeted to the development of OA wave detection systems and image reconstruction algorithms. In this work a new design of receiving array transducer, that allows to enhance image resolution is proposed. The array consists of 64 focused piezo-elements made of PVDF slabs imposed on a spherical surface. Resolution yielded by the array in different directions is determined. Several tissue irradiation geometries and laser wavelengths are considered for optimization of the OA image contrast. Obtained results are used for maximum imaging depth studies. All the investigations include both numerical modelling and experiment.

  10. ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS

    SciTech Connect

    Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

    2002-04-30

    Three major goals were accomplished during this phase. First, a study was completed of the effects of stress-induced changes in anisotropic elastic moduli in sandstone. Second, a new method for measuring the anisotropic poroelastic moduli from acoustic data was developed. Third, a series of triaxial experiments were conducted on unconsolidated sands to identify pressure/stress conditions where liquefaction occurs under high confining pressures. Stress-induced changes in anisotropic Young's moduli and shear moduli were observed during deformational pathway experiments. A new method was made for the acquisition of compressional and shear wave velocities along a series of 3-dimensional raypaths through a core sample as it is subjected to deformation. Three different deformational pathway experiments were conducted. During the hydrostatic deformation experiment, little or no anisotropy was observed in either the Young's moduli or shear moduli. Significant deformational anisotropies were observed in both moduli during the uniaxial strain test and the triaxial compression experiment but each had a different nature. During the triaxial experiment the axial and lateral Young's moduli and shear moduli continued to diverge as load was applied. During the uniaxial strain experiment the anisotropy was ''locked in'' early in the loading phase but then remained steady as both the confining pressure and axial stress were applied. A new method for measuring anisotropic Biot's effective stress parameters has also been developed. The method involves measuring the compressional and shear wave velocities in the aforementioned acoustic velocity experiments while varying stress paths. For a stress-induced transversely isotropic medium the acoustic velocity data are utilized to calculate the five independent elastic stiffness components. Once the elastic stiffness components are determined these can be used to calculate the anisotropic Biot's effective stress parameters, {alpha}{sub v

  11. Full-Wavefield Modeling and Pre-Stack Depth Migration of Common-Source Seismic Data

    NASA Astrophysics Data System (ADS)

    Chen, How-Wei

    1992-01-01

    The goal of solving geophysical problems can be thought of as a data mapping or transform procedure. Through various techniques, the observed seismic data can be transformed into the solution domain to estimate the Earth properties. Seismic wave field simulation is a forward process used to synthesize the seismic responses of an Earth model. Seismic wave field imaging is an inverse process used to estimate the Earth parameters from observed seismic data. In this dissertation, finite-difference and pseudo-spectral computations, in two- and three-dimensional space, are used for full wave field simulations and imaging of common-source data. Numerical simulation is developed for seismic sources and multi-attribute wave fields in two-dimensional acoustic and elastic media. P- and S-waves can be primarily separated in the resulting seismograms by vector operators in simulated surface survey, Vertical Seismic Profile (VSP) and cross-hole recording geometries. Three-component displacement seismograms can be approximately simulated by treating the acoustic field as a scalar potential field. The algorithm is applied to a complex multi-component, multi-offset walkaway circular VSP data from offshore California. Numerical modeling of large-scale, wide-aperture 3-D seismic data volumes is performed using a 3-D pseudo-spectral approach. Asymmetrical source and 3-D wave propagation effects in physical model data are identified and interpreted through iterative numerical modeling. Prestack reverse-time migration algorithms based on finite-difference and pseudo-spectral wave field extrapolators are developed for acoustic media in two- and three-dimensions. The excitation time imaging condition is computed by ray tracing and by finite-difference solution of the Eikonal equation. I generalize the concept of reverse-time migration and apply it for the correction of near-surface static effects. The feasibility of using very large scale, very wide-aperture 3-D seismic data recorded on a

  12. Pre- and post-stimulation characterization of geothermal well GRT-1, Rittershoffen, France: insights from acoustic image logs of hard fractured rock

    NASA Astrophysics Data System (ADS)

    Vidal, Jeanne; Genter, Albert; Schmittbuhl, Jean

    2016-08-01

    Geothermal well GRT-1 (Rittershoffen, Alsace) was drilled in 2012. Its open-hole section (extending down to a depth of 2.6 km) penetrated fractured sandstones and granite. In 2013, the well was subjected to Thermal, Chemical and Hydraulic (TCH) stimulation, which improved the injectivity index fivefold. The goal of the study was to assess the impact of the stimulation by comparing pre- and post-stimulation well-logging (acoustic and temperature [T] logs) and mud-logging data. This comparison revealed modifications of almost all the natural fractures. However, not all of these fractures are associated with permeability enhancement, and the post-stimulation T logs are important for characterizing this enhancement. Chemical alteration due to mechanical erosion at the tops and bottoms of the fractures was observed in the sandstones. These zones display indications of very small new permeability after the TCH stimulation. Because a major fault zone caved extensively where it crosses the borehole, it was not imaged in the acoustic logs. However, this originally permeable zone was enhanced as demonstrated by the T logs. Based on the natural injectivity of this fault zone, hydraulic erosion and thermal microcracking of its internal quartz veins are associated with this permeability enhancement. Although local changes in the borehole wall observed in the acoustic images cannot be directly linked to the improved injectivity index, the comparison of the acoustic image logs allows for identification of fracture zones impacted by the TCH stimulation.

  13. Fast photo-acoustic imaging based on multi-element linear transducer array

    NASA Astrophysics Data System (ADS)

    Yin, Bangzheng; Xing, Da; Yang, Diwu; Tan, Yi; Chen, Qun

    2005-04-01

    Photoacoustic imaging combines the contrast advantage of pure optical imaging and the resolution advantage of pure ultrasonic imaging. It has become a popular research subject at present. A fast photoacoustic imaging system based on multi-element linear transducer array and phase-controlled focus method was developed and tested on phantoms and tissues. A Q switched Nd:YAG laser operating at 532nm was used in our experiment as thermal source. The multi-element linear transducer array consists of 320 elements. By phase-controlled focus method, 64 signals, one of which gathered by 11-group element, make up of an image. Experiment results can map the distribution of the optical absorption correctly. The same transducer array also can operate as a conventional phase array and produced ultrasound imaging. Compared to other existing technology and algorithm, the PA imaging based on transducer array was characterize by speediness and convenience. It can provide a new approach for tissue functional imaging in vivo, and may have potentials in developing into an appliance for clinic diagnosis.

  14. Comparison of analytical and numerical approaches for CT-based aberration correction in transcranial passive acoustic imaging

    NASA Astrophysics Data System (ADS)

    Jones, Ryan M.; Hynynen, Kullervo

    2016-01-01

    Computed tomography (CT)-based aberration corrections are employed in transcranial ultrasound both for therapy and imaging. In this study, analytical and numerical approaches for calculating aberration corrections based on CT data were compared, with a particular focus on their application to transcranial passive imaging. Two models were investigated: a three-dimensional full-wave numerical model (Connor and Hynynen 2004 IEEE Trans. Biomed. Eng. 51 1693-706) based on the Westervelt equation, and an analytical method (Clement and Hynynen 2002 Ultrasound Med. Biol. 28 617-24) similar to that currently employed by commercial brain therapy systems. Trans-skull time delay corrections calculated from each model were applied to data acquired by a sparse hemispherical (30 cm diameter) receiver array (128 piezoceramic discs: 2.5 mm diameter, 612 kHz center frequency) passively listening through ex vivo human skullcaps (n  =  4) to emissions from a narrow-band, fixed source emitter (1 mm diameter, 516 kHz center frequency). Measurements were taken at various locations within the cranial cavity by moving the source around the field using a three-axis positioning system. Images generated through passive beamforming using CT-based skull corrections were compared with those obtained through an invasive source-based approach, as well as images formed without skull corrections, using the main lobe volume, positional shift, peak sidelobe ratio, and image signal-to-noise ratio as metrics for image quality. For each CT-based model, corrections achieved by allowing for heterogeneous skull acoustical parameters in simulation outperformed the corresponding case where homogeneous parameters were assumed. Of the CT-based methods investigated, the full-wave model provided the best imaging results at the cost of computational complexity. These results highlight the importance of accurately modeling trans-skull propagation when calculating CT-based aberration corrections

  15. B-Mode and Acoustic Radiation Force Impulse (ARFI) Imaging of Prostate Zonal Anatomy: Comparison with 3T T2-Weighted MR Imaging

    PubMed Central

    Palmeri, Mark L.; Miller, Zachary A.; Glass, Tyler J.; Garcia-Reyes, Kirema; Gupta, Rajan T.; Rosenzweig, Stephen J.; Kauffman, Christopher; Polascik, Thomas J.; Buck, Andrew; Kulbacki, Evan; Madden, John; Lipman, Samantha L.; Rouze, Ned C.; Nightingale, Kathryn R.

    2015-01-01

    Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R2 = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and −10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R2 = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (−28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management. PMID:25060914

  16. B-mode and acoustic radiation force impulse (ARFI) imaging of prostate zonal anatomy: comparison with 3T T2-weighted MR imaging.

    PubMed

    Palmeri, Mark L; Miller, Zachary A; Glass, Tyler J; Garcia-Reyes, Kirema; Gupta, Rajan T; Rosenzweig, Stephen J; Kauffman, Christopher; Polascik, Thomas J; Buck, Andrew; Kulbacki, Evan; Madden, John; Lipman, Samantha L; Rouze, Ned C; Nightingale, Kathryn R

    2015-01-01

    Prostate cancer (PCa) is the most common non-cutaneous malignancy among men in the United States and the second leading cause of cancer-related death. Multi-parametric magnetic resonance imaging (mpMRI) has gained recent popularity to characterize PCa. Acoustic Radiation Force Impulse (ARFI) imaging has the potential to aid PCa diagnosis and management by using tissue stiffness to evaluate prostate zonal anatomy and lesions. MR and B-mode/ARFI in vivo imaging datasets were compared with one another and with gross pathology measurements made immediately after radical prostatectomy. Images were manually segmented in 3D Slicer to delineate the central gland (CG) and prostate capsule, and 3D models were rendered to evaluate zonal anatomy dimensions and volumes. Both imaging modalities showed good correlation between estimated organ volume and gross pathologic weights. Ultrasound and MR total prostate volumes were well correlated (R(2) = 0.77), but B-mode images yielded prostate volumes that were larger (16.82% ± 22.45%) than MR images, due to overestimation of the lateral dimension (18.4% ± 13.9%), with less significant differences in the other dimensions (7.4% ± 17.6%, anterior-to-posterior, and -10.8% ± 13.9%, apex-to-base). ARFI and MR CG volumes were also well correlated (R(2) = 0.85). CG volume differences were attributed to ARFI underestimation of the apex-to-base axis (-28.8% ± 9.4%) and ARFI overestimation of the lateral dimension (21.5% ± 14.3%). B-mode/ARFI imaging yielded prostate volumes and dimensions that were well correlated with MR T2-weighted image (T2WI) estimates, with biases in the lateral dimension due to poor contrast caused by extraprostatic fat. B-mode combined with ARFI imaging is a promising low-cost, portable, real-time modality that can complement mpMRI for PCa diagnosis, treatment planning, and management. PMID:25060914

  17. Characterization of a Broadband All-Optical Ultrasound Transducer—From Optical and Acoustical Properties to Imaging

    PubMed Central

    Hou, Yang; Kim, Jin-Sung; Huang, Sheng-Wen; Ashkenazi, Shai; Guo, L. Jay; O’Donnell, Matthew

    2009-01-01

    A broadband all-optical ultrasound transducer has been designed, fabricated, and evaluated for high-frequency ultrasound imaging. The device consists of a 2-D gold nanostructure imprinted on top of a glass substrate, followed by a 3 μm PDMS layer and a 30 nm gold layer. A laser pulse at the resonance wavelength of the gold nanostructure is focused onto the surface for ultrasound generation, while the gold nanostructure, together with the 30 nm thick gold layer and the PDMS layer in between, forms an etalon for ultrasound detection, which uses a CW laser at a wavelength far from resonance as the probing beam. The center frequency of a pulse-echo signal recorded in the far field of the transducer is 40 MHz with -6 dB bandwidth of 57 MHz. The signal to noise ratio (SNR) from a 70 μm diameter transmit element combined with a 20 μm diameter receive element probing a near perfect reflector positioned 1.5 mm from the transducer surface is more than 10 dB and has the potential to be improved by at least another 40 dB. A high-frequency ultrasound array has been emulated using multiple measurements from the transducer while mechanically scanning an imaging target. Characterization of the device’s optical and acoustical properties, as well as preliminary imaging results, strongly suggest that all-optical ultrasound transducers can be used to build high-frequency arrays for real-time high-resolution ultrasound imaging. PMID:18986929

  18. Active and passive acoustic imaging inside a large-scale polyaxial hydraulic fracture test

    SciTech Connect

    Glaser, S.D.; Dudley, J.W. II; Shlyapobersky, J.

    1999-07-01

    An automated laboratory hydraulic fracture experiment has been assembled to determine what rock and treatment parameters are crucial to improving the efficiency and effectiveness of field hydraulic fractures. To this end a large (460 mm cubic sample) polyaxial cell, with servo-controlled X,Y,Z, pore pressure, crack-mouth-opening-displacement, and bottom hole pressure, was built. Active imaging with embedded seismic diffraction arrays images the geometry of the fracture. Preliminary tests indicate fracture extent can be imaged to within 5%. Unique embeddible high-fidelity particle velocity AE sensors were designed and calibrated to allow determination of fracture source kinematics.

  19. Imaging Acoustic Phonon Dynamics on the Nanometer-Femtosecond Spatiotemporal Length-Scale with Ultrafast Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Plemmons, Dayne; Flannigan, David

    Coherent collective lattice oscillations known as phonons dictate a broad range of physical observables in condensed matter and act as primary energy carriers across a wide range of material systems. Despite this omnipresence, analysis of phonon dynamics on their ultrashort native spatiotemporal length scale - that is, the combined nanometer (nm), spatial and femtosecond (fs), temporal length-scales - has largely remained experimentally inaccessible. Here, we employ ultrafast electron microscopy (UEM) to directly image discrete acoustic phonons in real-space with combined nm-fs resolution. By directly probing electron scattering in the image plane (as opposed to the diffraction plane), we retain phase information critical for following the evolution, propagation, scattering, and decay of phonons in relation to morphological features of the specimen (i.e. interfaces, grain boundaries, voids, ripples, etc.). We extract a variety of morphologically-specific quantitative information from the UEM videos including phonon frequencies, phase velocities, and decays times. We expect these direct manifestations of local elastic properties in the vicinity of material defects and interfaces will aide in the understanding and application of phonon-mediated phenomena in nanostructures. Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, 55455, USA.

  20. Evaluation of Stiffness of the Spastic Lower Extremity Muscles in Early Spinal Cord Injury by Acoustic Radiation Force Impulse Imaging

    PubMed Central

    Cho, Kang Hee

    2015-01-01

    Objective To investigate intrinsic viscoelastic changes using shear wave velocities (SWVs) of spastic lower extremity muscles in patients with early spinal cord injury (SCI) via acoustic radiation force impulse (ARFI) imaging and to evaluate correlation between the SWV values and spasticity. Methods Eighteen patients with SCI within 3 months and 10 healthy adults participated. We applied the ARFI technique to measure SWV of gastrocnemius muscle (GCM) and long head of biceps femoris muscle. Spasticity of ankle and knee joint was assessed by original Ashworth Scale. Results Ten patients with SCI had spasticity. Patients with spasticity had significantly faster SWV for GCM and biceps femoris muscle than those without spasticity (Mann-Whitney U test, p=0.007 and p=0.008) and normal control (p=0.011 and p=0.037, respectively). The SWV values of GCM correlated with the ankle spasticity (Spearman rank teat, p=0.026). There was significant correlation between the SWV values for long head of biceps femoris muscle and knee spasticity (Spearman rank teat, p=0.022). Conclusion ARFI demonstrated a difference in muscle stiffness in the GCM between patients with spastic SCI and those without spasticity. This finding suggested that stiffness of muscles increased in spastic lower extremity of early SCI patients. ARFI imaging is a valuable tool for noninvasive assessment of the stiffness of the spastic muscle and has the potential to identify pathomechanical changes of the tissue associated with SCI. PMID:26161345

  1. Basic investigation on acoustic velocity change imaging method for quantitative assessment of fat content in human liver

    NASA Astrophysics Data System (ADS)

    Mano, Kazune; Tanigawa, Shohei; Hori, Makoto; Yokota, Daiki; Wada, Kenji; Matsunaka, Toshiyuki; Morikawa, Hiroyasu; Horinaka, Hiromichi

    2016-07-01

    Fatty liver is a disease caused by the excess accumulation of fat in the human liver. The early diagnosis of fatty liver is very important, because fatty liver is the major marker linked to metabolic syndrome. We already proposed the ultrasonic velocity change imaging method to diagnose fatty liver by using the fact that the temperature dependence of ultrasonic velocity is different in water and in fat. For the diagonosis of a fatty liver stage, we attempted a feasibility study of the quantitative assessment of the fat content in the human liver using our ultrasonic velocity change imaging method. Experimental results showed that the fat content in the tissue mimic phantom containing lard was determined by its ultrasonic velocity change in the flat temperature region formed by a circular warming ultrasonic transducer with an acoustic lens having an appropriate focal length. By considering the results of our simulation using a thermal diffusion equation, we determined whether this method could be applied to fatty liver assessment under the condition that the tissue had the thermal relaxation effect caused by blood flow.

  2. Ultrasonic imaging of an object at the presence of Fourier and non-Fourier transformation in the transmitted through the object acoustic field.

    PubMed

    Andreeva, A; Burova, M; Burov, J

    2007-06-01

    A metal object is computer visualized by registration of the amplitudes of the transmitted through the object short acoustic pulses. The pulses are separated by time, because of the presence of holes and internal compact components in the longitudinal section (structure along the propagation direction of acoustic wave). The acoustic field transmitted through the object is composited from a field presenting Fourier transformation of the hole shape and field, transmitted through the metal components in the longitudinal section of the object. A computer Fourier transformation of the digital data of the amplitude fields transmitted through the object components is performed instead of converging lens. The Fourier series of the object obtained as digital data after the transformation is multiplied with a term, describing the angle distribution of the field on spatial frequencies. The reconstruction of the image of the metal components is performed by reverse transformation, i.e. summing up in all spatial frequencies. 3D visualization of the transmitted through the hole acoustic field determines the hole geometry (circular, square, rectangular). It is shown that at the transmission of a short acoustic pulse through the components with different thicknesses and holes, presenting Fourier and non-Fourier transformation can be registered separately in contrast to the optics. PMID:17395232

  3. Nonlinear acoustic enhancement in photoacoustic imaging with wideband absorptive nanoemulsion beads

    NASA Astrophysics Data System (ADS)

    Wei, Chen-wei; Lombardo, Michael; Xia, Jinjun; Pelivanov, Ivan; Perez, Camilo; Larson-Smith, Kjersta; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew

    2014-03-01

    A nanoemulsion contrast agent with a perfluorohexane core and optically absorptive gold nanospheres (GNSs) assembled on the surface, is presented to improve the specificity of photoacoustic (PA) molecular imaging in differentiating targeted cells or aberrant regions from heterogeneous background signals. Compared to distributed GNSs, clustered GNSs at the emulsion oil-water interface produce a red-shifted and broadened absorption spectrum, exhibiting fairly high absorption in the near-infrared region commonly used for deep tissue imaging. Above a certain laser irradiation fluence threshold, a phase transition creating a microbubble in the emulsion core leads to more than 10 times stronger PA signals compared with conventional thermal-expansion-induced PA signals. These signals are also strongly non-linear, as verified by a differential scheme using recorded PA images at different laser fluences. Assuming a linear relation between laser fluence and the PA signal amplitude, differential processing results in nearly perfect suppression of linear sources, but retains a significant residue for the non-linear nanoemulsion with more than 35 dB enhancement. This result demonstrates that contrast specificity can be improved using the nanoemulsion as a targeting agent in PA molecular imaging by suppressing all background signals related to a linear PA response. Furthermore, combined with a system providing simultaneous laser/ultrasound excitation, cavitation-generated bubbles have the potential to be a highly specific contrast agent for ultrasound molecular imaging and harmonic imaging, as well as a targeted means for noninvasive ultrasound-based therapies.

  4. Towards an acoustic model-based poroelastic imaging method: I. Theoretical foundation.

    PubMed

    Berry, Gearóid P; Bamber, Jeffrey C; Armstrong, Cecil G; Miller, Naomi R; Barbone, Paul E

    2006-04-01

    The ultrasonic measurement and imaging of tissue elasticity is currently under wide investigation and development as a clinical tool for the assessment of a broad range of diseases, but little account in this field has yet been taken of the fact that soft tissue is porous and contains mobile fluid. The ability to squeeze fluid out of tissue may have implications for conventional elasticity imaging, and may present opportunities for new investigative tools. When a homogeneous, isotropic, fluid-saturated poroelastic material with a linearly elastic solid phase and incompressible solid and fluid constituents is subjected to stress, the behaviour of the induced internal strain field is influenced by three material constants: the Young's modulus (E(s)) and Poisson's ratio (nu(s)) of the solid matrix and the permeability (k) of the solid matrix to the pore fluid. New analytical expressions were derived and used to model the time-dependent behaviour of the strain field inside simulated homogeneous cylindrical samples of such a poroelastic material undergoing sustained unconfined compression. A model-based reconstruction technique was developed to produce images of parameters related to the poroelastic material constants (E(s), nu(s), k) from a comparison of the measured and predicted time-dependent spatially varying radial strain. Tests of the method using simulated noisy strain data showed that it is capable of producing three unique parametric images: an image of the Poisson's ratio of the solid matrix, an image of the axial strain (which was not time-dependent subsequent to the application of the compression) and an image representing the product of the aggregate modulus E(s)(1-nu(s))/(1+nu(s))(1-2nu(s)) of the solid matrix and the permeability of the solid matrix to the pore fluid. The analytical expressions were further used to numerically validate a finite element model and to clarify previous work on poroelastography. PMID:16616601

  5. FAST TRACK PAPER: Evaluation of elastodynamic interferometric redatuming: a synthetic study on salt dome flank imaging

    NASA Astrophysics Data System (ADS)

    Lu, Rongrong; Willis, Mark E.; Campman, Xander H.; Toksöz, M. Nafi

    2009-03-01

    The recent introduction of novel redatuming techniques, based on the principles of time-reversed acoustics and source-receiver reciprocity, has allowed seismic measurements collected on one datum to be extrapolated to another datum. Under favourable conditions, this process can approximately remove the complicated overburden structures without any velocity information. We introduce an elastic redatuming scheme for walkaway vertical seismic profiles (WVSPs) based on these principles, using P- and S-wave potentials, which are derived from the spatial derivatives of the measured wavefields. Additional field acquisition is utilized to directly measure these derivatives. We test our elastic redatuming scheme on data simulated with an elastic finite difference algorithm. The elastodynamic Green's functions between multicomponent receivers in a borehole are then extracted from data recorded using multicomponent (P- and S-wave) sources at the surface. The wavefields are redatumed as four parts: two related to the P-wave potential, and another two related to the S-wave potential. These parts are migrated separately and form four independent images of the salt dome flank, providing a more complete elastic description of the subsurface.

  6. Application of computed tomography to the acoustic imaging of sea mines at safe standoff distances

    NASA Astrophysics Data System (ADS)

    Wyber, Ron; Ferguson, Brian

    2002-05-01

    Typical imaging sonars make use of very high frequencies and arrays with a large number of sensors to provide high angular resolution. With such arrays the spatial resolution degrades and high propagation losses occur as the sonar is moved away from the target being imaged and operational ranges are generally 5 m or less. An alternative imaging technique has been implemented using computed tomography in which the target is insonified with a broad beam from multiple aspects. The spatial resolution achievable with this method is determined only by the bandwidth of the test signal and not by the beamwidth of the sonar or the distance of the sonar from the target. Results are presented showing clear images of mines and mine-like objects in which a spatial resolution of better than 2 cm is achieved at a range of 60 m, even for low target strength mines. Features are evident in the images that are related to both the internal and external shape of the targets as well as structural waves propagating within the targets. This offers the potential to provide unambiguous classification of mines from long ranges, even in a harsh operational environment.

  7. Imaging of offset VSP data with an elastic iterative migration scheme

    SciTech Connect

    Mittet, R.; Hokstad, K.; Helgesen, J.; Canadas, G.

    1997-03-01

    VSP data are usually acquired in order to obtain high-resolution images of complex structures in reservoirs and near boreholes. The authors present an elastic iterative migration scheme which has few limitations regarding the complexity of the geology, and where the macromodel for both P- and S-wave velocities is automatically improved and updated at each iteration. They avoid wavefield separation (up/down and P/S) and the simplifying assumptions of small dips underlying most such methods. The migration scheme is based on elastic inversion theory. The wavefield extrapolation is based on a high-order, coarse-grid, finite-difference solution to the elastic two-way wave equation. At each iteration, the macromodel is updated using a gradient method, in which the gradient is computed by correlation of forward-modelled fields with back-propagated residual fields. The first iteration of the migration scheme is equivalent to elastic reverse-time migration with an imaging condition similar to Claerbout`s principle. Both P- and S-wave reflections contribute to the images. In numerical examples with both synthetic and real offset VSP data, they find that increasing the number of iterations improves the image quality. Images based on both P- and S-wave energy give more near-well information and higher spatial resolution than images on only acoustic energy. In the real data example the authors show that the iterative migration scheme can image a relatively complex geological structure. A fault and a small graben intersecting the well can be identified.

  8. Accurate acoustic and elastic beam migration without slant stack for complex topography

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Yuan, Maolin; Liao, Wenyuan; Li, Zhenchun; Yue, Yubo

    2015-06-01

    Recent trends in seismic exploration have led to the collection of more surveys, often with multi-component recording, in onshore settings where both topography and subsurface targets are complex, leading to challenges for processing methods. Gaussian beam migration (GBM) is an alternative to single-arrival Kirchhoff migration, although there are some issues resulting in unsatisfactory GBM images. For example, static correction will give rise to the distortion of wavefields when near-surface elevation and velocity vary rapidly. Moreover, Green’s function compensated for phase changes from the beam center to receivers is inaccurate when receivers are not placed within some neighborhood of the beam center, that is, GBM is slightly inflexible for irregular acquisition system and complex topography. As a result, the differences of both the near-surface velocity and the surface slope from the beam center to the receivers and the poor spatial sampling of the land data lead to inaccuracy and aliasing of the slant stack, respectively. In order to improve the flexibility and accuracy of GBM, we propose accurate acoustic, PP and polarity-corrected PS beam migration without slant stack for complex topography. The applications of this method to one-component synthetic data from a 2D Canadian Foothills model and a Zhongyuan oilfield fault model, one-component field data and an unseparated multi-component synthetic data demonstrate that the method is effective for structural and relatively amplitude-preserved imaging, but significantly more time-consuming.

  9. Assessment of liver fibrosis with 2-D shear wave elastography in comparison to transient elastography and acoustic radiation force impulse imaging in patients with chronic liver disease.

    PubMed

    Gerber, Ludmila; Kasper, Daniela; Fitting, Daniel; Knop, Viola; Vermehren, Annika; Sprinzl, Kathrin; Hansmann, Martin L; Herrmann, Eva; Bojunga, Joerg; Albert, Joerg; Sarrazin, Christoph; Zeuzem, Stefan; Friedrich-Rust, Mireen

    2015-09-01

    Two-dimensional shear wave elastography (2-D SWE) is an ultrasound-based elastography method integrated into a conventional ultrasound machine. It can evaluate larger regions of interest and, therefore, might be better at determining the overall fibrosis distribution. The aim of this prospective study was to compare 2-D SWE with the two best evaluated liver elastography methods, transient elastography and acoustic radiation force impulse (point SWE using acoustic radiation force impulse) imaging, in the same population group. The study included 132 patients with chronic hepatopathies, in which liver stiffness was evaluated using transient elastography, acoustic radiation force impulse imaging and 2-D SWE. The reference methods were liver biopsy for the assessment of liver fibrosis (n = 101) and magnetic resonance imaging/computed tomography for the diagnosis of liver cirrhosis (n = 31). No significant difference in diagnostic accuracy, assessed as the area under the receiver operating characteristic curve (AUROC), was found between the three elastography methods (2-D SWE, transient elastography, acoustic radiation force impulse imaging) for the diagnosis of significant and advanced fibrosis and liver cirrhosis in the "per protocol" (AUROCs for fibrosis stages ≥2: 0.90, 0.95 and 0.91; for fibrosis stage [F] ≥3: 0.93, 0.95 and 0.94; for F = 4: 0.92, 0.96 and 0.92) and "intention to diagnose" cohort (AUROCs for F ≥2: 0.87, 0.92 and 0.91; for F ≥3: 0.91, 0.93 and 0.94; for F = 4: 0.88, 0.90 and 0.89). Therefore, 2-D SWE, ARFI imaging and transient elastography seem to be comparably good methods for non-invasive assessment of liver fibrosis. PMID:26116161

  10. Seismic Imaging Of The South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Sheen, K.; White, N.; Hobbs, R.

    2008-12-01

    Seismic oceanography is a powerful, new technique which utilises seismic reflection profiling to yield detailed acoustic images of ocean finestructure. The method uses seismic reflections generated by acoustic impedance changes which occur across water mass boundaries as a result of variations in temperature and salinity. Here we present a series of seismic images of the water column from a region in the southwest Atlantic using legacy seismic reflection datasets shot in the 1990s. The seismic surveys follow the Antarctic Circumpolar Current as it veers northward after exiting Drake Passage, looping around the Falkland Trough and finally entering the Argentinian Basin, largely following the Sub Antarctic Front route. Finestructure imaged in the data occurs dominantly in the boundary layer between Antarctic Intermediate Water and underlying Upper Circumpolar Deep Water, and correlates well with hydrographic interpretations. Structures such as dipping bands of heterogeneous water and eddies characterized by homogeneous cores and strong reflective inter-leaving edges are seen in the vicinity of ocean fronts. Further to the north, interesting thermohaline structures associated with the intrusion of North Atlantic Deep Water into the region have been captured. Seasonal variations in the time of data acquisition and the subsequent differences in the acoustic images provide interesting insights into the temporal variability of the water masses. Turbulent mixing in this part of the Southern Ocean is known to be remarkably intense and widespread and thought to contribute significantly to driving the upward transport of water closing the ocean's meridional overturning circulation. The deformation of thermohaline finestructure by such mixing and the ambient internal wavefield results in small undulations along seismic reflection horizons. Spectral analysis of these sinusoidal displacements has been used to extract quantitative information on internal wave energy and deduce

  11. Method for imaging with low frequency electromagnetic fields

    DOEpatents

    Lee, Ki H.; Xie, Gan Q.

    1994-01-01

    A method for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The traveltimes corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter .alpha. for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography.

  12. Method for imaging with low frequency electromagnetic fields

    DOEpatents

    Lee, K.H.; Xie, G.Q.

    1994-12-13

    A method is described for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The travel times corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter [alpha] for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography. 13 figures.

  13. Development of Acoustic Model-Based Iterative Reconstruction Technique for Thick-Concrete Imaging

    SciTech Connect

    Almansouri, Hani; Clayton, Dwight A; Kisner, Roger A; Polsky, Yarom; Bouman, Charlie; Santos-Villalobos, Hector J

    2015-01-01

    Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well s health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.

  14. Development of Acoustic Model-Based Iterative Reconstruction Technique for Thick-Concrete Imaging

    SciTech Connect

    Almansouri, Hani; Clayton, Dwight A; Kisner, Roger A; Polsky, Yarom; Bouman, Charlie; Santos-Villalobos, Hector J

    2016-01-01

    Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well's health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.

  15. Development of acoustic model-based iterative reconstruction technique for thick-concrete imaging

    NASA Astrophysics Data System (ADS)

    Almansouri, Hani; Clayton, Dwight; Kisner, Roger; Polsky, Yarom; Bouman, Charles; Santos-Villalobos, Hector

    2016-02-01

    Ultrasound signals have been used extensively for non-destructive evaluation (NDE). However, typical reconstruction techniques, such as the synthetic aperture focusing technique (SAFT), are limited to quasi-homogenous thin media. New ultrasonic systems and reconstruction algorithms are in need for one-sided NDE of non-homogenous thick objects. An application example space is imaging of reinforced concrete structures for commercial nuclear power plants (NPPs). These structures provide important foundation, support, shielding, and containment functions. Identification and management of aging and degradation of concrete structures is fundamental to the proposed long-term operation of NPPs. Another example is geothermal and oil/gas production wells. These multi-layered structures are composed of steel, cement, and several types of soil and rocks. Ultrasound systems with greater penetration range and image quality will allow for better monitoring of the well's health and prediction of high-pressure hydraulic fracturing of the rock. These application challenges need to be addressed with an integrated imaging approach, where the application, hardware, and reconstruction software are highly integrated and optimized. Therefore, we are developing an ultrasonic system with Model-Based Iterative Reconstruction (MBIR) as the image reconstruction backbone. As the first implementation of MBIR for ultrasonic signals, this paper document the first implementation of the algorithm and show reconstruction results for synthetically generated data.1

  16. Photo-acoustic imaging of blue nanoparticle targeted brain tumor for intra-operative glioma delineation

    NASA Astrophysics Data System (ADS)

    Ray, Aniruddha; Wang, Xueding; Koo Lee, Yong-Eun; Hah, HoeJin; Kim, Gwangseong; Chen, Thomas; Orrienger, Daniel; Sagher, Oren; Kopelman, Raoul

    2011-07-01

    Distinguishing the tumor from the background neo-plastic tissue is challenging for cancer surgery such as surgical resection of glioma. Attempts have been made to use visible or fluorescent markers to delineate the tumors during surgery. However, the systemic injection of the dyes requires high dose, resulting in negative side effects. A novel method to delineate rat brain tumors intra-operatively, as well as post-operatively, using a highly sensitive photoacoustic imaging technique enhanced by tumor targeting blue nanoparticle as contrast agent is demonstrated. The nanoparticles are made of polyacrylamide (PAA) matrix with covalently linked Coomassie-Blue dye. They contain 7.0% dye and the average size is 80nm. Their surface was conjugated with F3 peptide for active tumor targeting. These nanoparticles are nontoxic, chemically inert and have long plasma circulation lifetime, making them suitable as nanodevices for imaging using photoacoustics. Experiments on phantoms and rat brains tumors ex-vivo demonstrate the high sensitivity of photoacoustic imaging in delineating the tumor, containing contrast agent at concentrations too low to be visualized by eye. The control tumors without nanoparticles did not show any enhanced signal. This study shows that photoacoustic imaging facilitated with the nanoparticle contrast agent could contribute to future surgical procedures for glioma.

  17. Towards an acoustic model-based poroelastic imaging method: II. experimental investigation.

    PubMed

    Berry, Gearóid P; Bamber, Jeffrey C; Miller, Naomi R; Barbone, Paul E; Bush, Nigel L; Armstrong, Cecil G

    2006-12-01

    Soft biological tissue contains mobile fluid. The volume fraction of this fluid and the ease with which it may be displaced through the tissue could be of diagnostic significance and may also have consequences for the validity with which strain images can be interpreted according to the traditional idealizations of elastography. In a previous paper, under the assumption of frictionless boundary conditions, the spatio-temporal behavior of the strain field inside a compressed cylindrical poroelastic sample was predicted (Berry et al. 2006). In this current paper, experimental evidence is provided to confirm these predictions. Finite element modeling was first used to extend the previous predictions to allow for the existence of contact friction between the sample and the compressor plates. Elastographic techniques were then applied to image the time-evolution of the strain inside cylindrical samples of tofu (a suitable poroelastic material) during sustained unconfined compression. The observed experimental strain behavior was found to be consistent with the theoretical predictions. In particular, every sample studied confirmed that reduced values of radial strain advance with time from the curved cylindrical surface inwards towards the axis of symmetry. Furthermore, by fitting the predictions of an analytical model to a time sequence of strain images, parametric images of two quantities, each related to one or more of three poroelastic material constants were produced. The two parametric images depicted the Poisson's ratio (nu(s)) of the solid matrix and the product of the aggregate modulus (H(A)) of the solid matrix with the permeability (k) of the solid matrix to the pore fluid. The means of the pixel values in these images, nu(s) = 0.088 (standard deviation 0.023) and H(A)k = 1.449 (standard deviation 0.269) x 10(-7) m(2) s(-1), were in agreement with values derived from previously published data for tofu (Righetti et al. 2005). The results provide the first

  18. Innovative acoustic reflection imaging techniques and application to clinical breast tomography

    NASA Astrophysics Data System (ADS)

    Schmidt, Steve P.

    Conventional ultrasound techniques use beam-formed, constant sound speed ray models for fast image reconstruction. However, these techniques are inadequate for the emerging new field of ultrasound tomography (UST). We present a new technique for reconstruction of reflection images from UST data. We have extended the planar Kirchhoff migration method used in geophysics, and combined it with sound speed and attenuation data obtained from the transmission signals to create reflection ultrasound images that are corrected for refractive and attenuative effects. The resulting techniques were applied to simulated numerical phantom data, physical phantom data and in-vivo breast data obtained with an experimental ring transducer prototype. Additionally, the ring transducer was customized to test compatibility with an existing ultrasound workstation. We were able to obtain independently recorded radio-frequency (RF) data for individual transmit-receive pair combinations for all 128 transducers. The signal data was then successfully reconstructed into reflection data using the Kirchhoff migration techniques. The results from the use of sound speed and attenuation corrections lead to significant improvements in image quality, particularly in dense tissues where the refractive and scattering effects are the greatest. The procedure was applied to a variety of breast densities and masses of different natures. The resulting reflection images successfully resolved boundaries and textures. The reflection characteristics of tomographic ultrasound maintain an indispensible position in the quantification of proper mass identification. The results of this project indicate the clinical significance of the invocation of properly compensated Kirchhoff based reconstruction method with the use of sound speed and attenuation parameters for the visualization and classification of masses and tissue.

  19. Acoustic hemostasis

    NASA Astrophysics Data System (ADS)

    Crum, L.; Andrew, M.; Bailey, M.; Beach, K.; Brayman, A.; Curra, F.; Kaczkowski, P.; Kargl, S.; Martin, R.; Vaezy, S.

    2003-04-01

    Over the past several years, the Center for Industrial and Medical Ultrasound (CIMU) at the Applied Physics Laboratory in the University of Washington has undertaken a broad research program in the general area of High Intensity Focused Ultrasound (HIFU). Our principal emphasis has been on the use of HIFU to induce hemostasis; in particular, CIMU has sought to develop a small, lightweight, portable device that would use ultrasound for both imaging and therapy. Such a technology is needed because nearly 50% of combat casualty mortality results from exsanguinations, or uncontrolled bleeding. A similar percentage occurs for civilian death due to trauma. In this general review, a presentation of the general problem will be given, as well as our recent approaches to the development of an image-guided, transcutaneous, acoustic hemostasis device. [Work supported in part by the USAMRMC, ONR and the NIH.

  20. Acoustic mapping velocimetry

    NASA Astrophysics Data System (ADS)

    Muste, M.; Baranya, S.; Tsubaki, R.; Kim, D.; Ho, H.; Tsai, H.; Law, D.

    2016-05-01

    Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments.

  1. Statistical redundancy of instantaneous phases: theory and application to the seismic ambient wavefield

    NASA Astrophysics Data System (ADS)

    Gaudot, I.; Beucler, É.; Mocquet, A.; Schimmel, M.; Le Feuvre, M.

    2016-02-01

    In order to detect possible signal redundancies in the ambient seismic wavefield, we develop a new method based on pairwise comparisons among a set of synchronous time-series. This approach is based on instantaneous phase coherence statistics. The first and second moments of the pairwise phase coherence distribution are used to characterize the phase randomness. For perfect phase randomness, the theoretical values of the mean and variance are equal to 0 and √{1-2/π }, respectively. As a consequence, any deviation from these values indicates the presence of a redundant phase in the raw continuous signal. A previously detected microseismic source in the Gulf of Guinea is used to illustrate one of the possible ways of handling phase coherence statistics. The proposed approach allows us to properly localize this persistent source, and to quantify its contribution to the overall seismic ambient wavefield. The strength of the phase coherence statistics relies in its ability to quantify the redundancy of a given phase among a set of time-series with various useful applications in seismic noise-based studies (tomography and/or source characterization).

  2. Interaction of an acoustical 2D-beam with an elastic cylinder with arbitrary location in a non-viscous fluid.

    PubMed

    Mitri, F G

    2015-09-01

    The classical Resonance Scattering Theory (RST) for plane waves in acoustics is generalized for the case of a 2D arbitrarily-shaped beam incident upon an elastic cylinder with arbitrary location that is immersed in a nonviscous fluid. The formulation is valid for an elastic (or viscoelastic) cylinder (or a cylindrical shell, a layered cylinder/shell, or a multilayered cylindrical shell, etc.) of any size and material. Partial-wave series expansions (PWSEs) for the incident, internal and scattered fields are derived, and numerical examples illustrate the theory. The wave-fields are expressed using a generalized PWSE involving the beam-shape coefficients (BSCs) and the scattering coefficients of the cylinder. When the beam is shifted off the center of the cylinder, the off-axial BSCs are evaluated by performing standard numerical integration. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. The properties related to the arbitrary scattering of a zeroth-order quasi-Gaussian cylindrical beam (chosen as an example) by an elastic brass cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed. Moreover, the total and resonance backscattering form function moduli are numerically computed, and the results discussed with emphasis on the contribution of the surface waves circumnavigating the cylinder circular surface to the resonance backscattering. Furthermore, the analysis is extended to derive general expressions for the axial and transverse acoustic radiation force functions for the cylinder in any 2D beam of arbitrary shape. Examples are provided for a zeroth-order quasi Gaussian cylindrical beam with different waist. Potential applications are in underwater and physical acoustics, however, ongoing research in biomedical ultrasound, non-destructive evaluation, imaging, manufacturing, instrumentation, and

  3. Directly imaging steeply-dipping fault zones in geothermal fields with multicomponent seismic data

    DOE PAGESBeta

    Chen, Ting; Huang, Lianjie

    2015-07-30

    For characterizing geothermal systems, it is important to have clear images of steeply-dipping fault zones because they may confine the boundaries of geothermal reservoirs and influence hydrothermal flow. Elastic reverse-time migration (ERTM) is the most promising tool for subsurface imaging with multicomponent seismic data. However, conventional ERTM usually generates significant artifacts caused by the cross correlation of undesired wavefields and the polarity reversal of shear waves. In addition, it is difficult for conventional ERTM to directly image steeply-dipping fault zones. We develop a new ERTM imaging method in this paper to reduce these artifacts and directly image steeply-dipping fault zones.more » In our new ERTM method, forward-propagated source wavefields and backward-propagated receiver wavefields are decomposed into compressional (P) and shear (S) components. Furthermore, each component of these wavefields is separated into left- and right-going, or downgoing and upgoing waves. The cross correlation imaging condition is applied to the separated wavefields along opposite propagation directions. For converted waves (P-to-S or S-to-P), the polarity correction is applied to the separated wavefields based on the analysis of Poynting vectors. Numerical imaging examples of synthetic seismic data demonstrate that our new ERTM method produces high-resolution images of steeply-dipping fault zones.« less

  4. Directly imaging steeply-dipping fault zones in geothermal fields with multicomponent seismic data

    SciTech Connect

    Chen, Ting; Huang, Lianjie

    2015-07-30

    For characterizing geothermal systems, it is important to have clear images of steeply-dipping fault zones because they may confine the boundaries of geothermal reservoirs and influence hydrothermal flow. Elastic reverse-time migration (ERTM) is the most promising tool for subsurface imaging with multicomponent seismic data. However, conventional ERTM usually generates significant artifacts caused by the cross correlation of undesired wavefields and the polarity reversal of shear waves. In addition, it is difficult for conventional ERTM to directly image steeply-dipping fault zones. We develop a new ERTM imaging method in this paper to reduce these artifacts and directly image steeply-dipping fault zones. In our new ERTM method, forward-propagated source wavefields and backward-propagated receiver wavefields are decomposed into compressional (P) and shear (S) components. Furthermore, each component of these wavefields is separated into left- and right-going, or downgoing and upgoing waves. The cross correlation imaging condition is applied to the separated wavefields along opposite propagation directions. For converted waves (P-to-S or S-to-P), the polarity correction is applied to the separated wavefields based on the analysis of Poynting vectors. Numerical imaging examples of synthetic seismic data demonstrate that our new ERTM method produces high-resolution images of steeply-dipping fault zones.

  5. Bioacoustic systems: insights for acoustical imaging and pattern recognition (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Altes, Richard A.

    1987-09-01

    Standard performance measures and statistical tests must be altered for research on animal sonar. The narrowband range-Doppler ambiguity function must be redefined to analyze wideband signals. A new range, cross-range ambiguity function is needed to represent angle estimation and spatial resolution properties of animal sonar systems. Echoes are transformed into time-frequency (spectrogram-like) representations by the peripheral auditory system. Detection, estimation, and pattern recognition capabilities of animals should thus be analyzed in terms of operations on spectrograms. The methods developed for bioacoustic research yield new insights into the design of man-made imaging and pattern recognition systems. The range, cross-range ambiguity function can be used to improve imaging performance. Important features for echo pattern recognition are illustrated by time-frequency plots showing (i) principal components for spectrograms and (ii) templates for optimum discrimination between data classes.

  6. Acoustic Remote Sensing

    NASA Astrophysics Data System (ADS)

    Dowling, David R.; Sabra, Karim G.

    2015-01-01

    Acoustic waves carry information about their source and collect information about their environment as they propagate. This article reviews how these information-carrying and -collecting features of acoustic waves that travel through fluids can be exploited for remote sensing. In nearly all cases, modern acoustic remote sensing involves array-recorded sounds and array signal processing to recover multidimensional results. The application realm for acoustic remote sensing spans an impressive range of signal frequencies (10-2 to 107 Hz) and distances (10-2 to 107 m) and involves biomedical ultrasound imaging, nondestructive evaluation, oil and gas exploration, military systems, and Nuclear Test Ban Treaty monitoring. In the past two decades, approaches have been developed to robustly localize remote sources; remove noise and multipath distortion from recorded signals; and determine the acoustic characteristics of the environment through which the sound waves have traveled, even when the recorded sounds originate from uncooperative sources or are merely ambient noise.

  7. Pre- and post-stimulation characterization of geothermal well GRT-1, Rittershoffen, France: insights from acoustic image logs of hard fractured rock

    NASA Astrophysics Data System (ADS)

    Vidal, Jeanne; Genter, Albert; Schmittbuhl, Jean

    2016-05-01

    Geothermal well GRT-1 (Rittershoffen, Alsace) was drilled in 2012. Its open-hole section (extending down to a depth of 2.6 km) penetrated fractured sandstones and granite. In 2013, the well was subjected to Thermal, Chemical and Hydraulic (TCH) stimulation, which improved the injectivity index five-fold. The goal of the study was to assess the impact of the stimulation by comparing pre- and post-stimulation logs and well-logging (temperature [T] log) and mud-logging data. This comparison revealed modifications of almost all the natural fractures. However, not all of these fractures are associated with permeability enhancement, and the post-stimulation T logs are important for characterizing this enhancement. Chemical alteration due to mechanical erosion at the tops and bottoms of the fractures was observed in the sandstones. These zones display indications of very small new permeability after the TCH stimulation. Because a major fault zone caved extensively where it crosses the borehole, it was not imaged in the acoustic logs. However, this originally permeable zone was enhanced as demonstrated by the T logs. Based on the natural injectivity of this fault zone, hydraulic erosion and thermal microcracking of its internal quartz veins are associated with this permeability enhancement. Although local changes in the borehole wall observed in the acoustic images cannot be directly linked to the improved injectivity index, the comparison of the acoustic image logs allows for identification of fracture zones impacted by the TCH stimulation.

  8. Enhanced characterization of calcified areas in intravascular ultrasound virtual histology images by quantification of the acoustic shadow: validation against computed tomography coronary angiography.

    PubMed

    Broersen, Alexander; de Graaf, Michiel A; Eggermont, Jeroen; Wolterbeek, Ron; Kitslaar, Pieter H; Dijkstra, Jouke; Bax, Jeroen J; Reiber, Johan H C; Scholte, Arthur J

    2016-04-01

    We enhance intravascular ultrasound virtual histology (VH) tissue characterization by fully automatic quantification of the acoustic shadow behind calcified plaque. VH is unable to characterize atherosclerosis located behind calcifications. In this study, the quantified acoustic shadows are considered calcified to approximate the real dense calcium (DC) plaque volume. In total, 57 patients with 108 coronary lesions were included. A novel post-processing step is applied on the VH images to quantify the acoustic shadow and enhance the VH results. The VH and enhanced VH results are compared to quantitative computed tomography angiography (QTA) plaque characterization as reference standard. The correlation of the plaque types between enhanced VH and QTA differs significantly from the correlation with unenhanced VH. For DC, the correlation improved from 0.733 to 0.818. Instead of an underestimation of DC in VH with a bias of 8.5 mm(3), there was a smaller overestimation of 1.1 mm(3) in the enhanced VH. Although tissue characterization within the acoustic shadow in VH is difficult, the novel algorithm improved the DC tissue characterization. This algorithm contributes to accurate assessment of calcium on VH and could be applied in clinical studies. PMID:26667446

  9. Recent Advancements in Quantitative Full-Wavefield Electromagnetic Induction and Ground Penetrating Radar Inversion for Shallow Subsurface Characterization

    NASA Astrophysics Data System (ADS)

    Van Der Kruk, J.; Yang, X.; Klotzsche, A.; von Hebel, C.; Busch, S.; Mester, A.; Huisman, J. A.; Vereecken, H.

    2014-12-01

    Ray-based or approximate forward modeling techniques have been often used to reduce the computational demands for inversion purposes. Due to increasing computational power and possible parallelization of inversion algorithms, accurate forward modeling can be included in advanced inversion approaches such that the full-wavefield content can be exploited. Here, recent developments of large-scale quantitative electromagnetic induction (EMI) inversion and full-waveform ground penetrating radar (GPR) inversions are discussed that yield higher resolution of quantitative medium properties compared to conventional approaches due to the use of accurate modeling tools that are based on Maxwell's equations. For a limited number of parameters, a combined global and local search using the simplex search algorithm or the shuffled complex evolution (SCE) can be used for inversion. Examples will be shown where calibrated large-scale multi-configuration EMI data measured with new generation multi-offset EMI systems are inverted for a layered electrical conductivity earth, and quantitative permittivity and conductivity values of a layered subsurface can be obtained using on-ground GPR full-waveform inversion that includes the estimation of the unknown source wavelet. For a large number of unknowns, gradient-based optimization methods are commonly used that need a good start model to prevent it from being trapped in a local minimum. Examples will be shown where the non-linearity invoked by the presence of high contrast media can be tamed by using a novel combined frequency-time-domain full-waveform inversion, and a low-velocity waveguide layer can be imaged by using crosshole GPR full-waveform inversion, after adapting the starting model using waveguide identification in the measured data. Synthetic data calculated using the inverted permittivity and conductivity models show similar amplitudes and phases as observed in the measured data, which indicates the reliability of the

  10. Waveform Inversion of OBS Data and Illumination/Resolution Analyses on Marine Seismic Data Acquisitions by the Adjoint Wavefield Method

    NASA Astrophysics Data System (ADS)

    Chen, H.; Li, K.

    2012-12-01

    We applied a wave-equation based adjoint wavefield method for seismic illumination/resolution analyses and full waveform inversion. A two-way wave-equation is used to calculate directional and diffracted energy fluxes for waves propagating between sources and receivers to the subsurface target. The first-order staggered-grid pressure-velocity formulation, which lacks the characteristic of being self-adjoint is further validated and corrected to render the modeling operator before its practical application. Despite most published papers on synthetic kernel research, realistic applications to two field experiments are demonstrated and emphasize its practical needs. The Fréchet sensitivity kernels are used to quantify the target illumination conditions. For realistic illumination measurements and resolution analyses, two completely different survey geometries and nontrivial pre-conditioning strategies based on seismic data type are demonstrated and compared. From illumination studies, particle velocity responses are more sensitive to lateral velocity variations than pressure records. For waveform inversion, the more accurately estimated velocity model obtained the deeper the depth of investigation would be reached. To achieve better resolution and illumination, closely spaced OBS receiver interval is preferred. Based on the results, waveform inversion is applied for a gas hydrate site in Taiwan for shallow structure and BSR detection. Full waveform approach potentially provides better depth resolution than ray approach. The quantitative analyses, a by-product of full waveform inversion, are useful for quantifying seismic processing and depth migration strategies.llumination/resolution analysis for a 3D MCS/OBS survey in 2008. Analysis of OBS data shows that pressure (top), horizontal (middle) and vertical (bottom) velocity records produce different resolving power for gas hydrate exploration. ull waveform inversion of 8 OBS data along Yuan-An Ridge in SW Taiwan

  11. Acoustic microscopy of living cells.

    PubMed Central

    Hildebrand, J A; Rugar, D; Johnston, R N; Quate, C F

    1981-01-01

    This paper reports preliminary results of the observation by acoustic microscopy of living cells in vitro. The scanning acoustic microscope uses high-frequency sound waves to produce images with submicrometer resolution. The contrast observed in acoustic micrographs of living cells depends on the acoustic properties (i.e., density, stiffness, and attenuation) and on the topographic contour of the cell. Variation in distance separating the acoustic lens and the viewed cell also has a profound effect on the image. When the substratum is located at the focal plane, thick regions of the cell show a darkening that can be related to cellular acoustic attenuation (a function of cytoplasmic viscosity). When the top of the cell is placed near the focal plane, concentric bright and dark rings appear in the image. The location of the rings can be related to cell topography, and the ring contrast can be correlated to the stiffness and density of the cell. In addition, the character of the images of single cells varies dramatically when the substratum upon which they are grown is changed to a different material. By careful selection of the substratum, the information content of the acoustic images can be increased. Our analysis of acoustic images of actively motile cells indicates that leading lamella are less dense or stiff than the quiescent trailing processes of the cells. Images PMID:6940179

  12. An excitation potential imaging condition for elastic reverse time migration

    NASA Astrophysics Data System (ADS)

    Gu, Bingluo; Liu, Youshan; Li, Zhiyuan; Ma, Xiaona; Liang, Guanghe

    2014-09-01

    Elastic reverse time migration (ERTM) has been demonstrated to be more accurate than scalar RTM. However, low efficiency (large storage and heavy calculated amount) and strong artifacts caused by the crosstalk between different wave modes are the two primary barriers to the application of the ERTM during the processing of real data. The scalar (P) and vector (S) potentials of the elastic wavefield and the arrival times corresponding to the first energy extremum of the wavefield are saved at each grid point during the forward modeling of the source wavefield. The angle-dependent reflection coefficient images are subsequently obtained by dividing the scalar and vector potentials of the backward extrapolated receiver wavefield by the saved scalar and vector potentials at the grid points that satisfy the image time at each time step, respectively. The proposed imaging condition does not need to store the snapshots of the source wavefield, while it can considerably improve the computational efficiency and decrease the amount of storage and Input/Output manipulation (compared with the cross-correlation imaging condition) in addition to suppressing the crosstalk between compressive and shear wave modes. Compared with the excitation time imaging condition, the proposed imaging condition reduces the energy loss caused by the opposite polarity of the horizontal component at opposite sides of the source in stacked images. Numerical tests with synthetic data of the Sigsbee2a model have demonstrated that this imaging condition is a cost-effective and practical imaging condition for use in prestack ERTM.

  13. Acoustic Radiation Force Impulse Imaging: A New Tool for the Diagnosis of Papillary Thyroid Microcarcinoma

    PubMed Central

    Zhang, Yi-Feng; Xu, Jun-Mei; Zhang, Jing; Liu, Lin-Na; Xu, Xiao-Hong

    2014-01-01

    Purpose. To evaluate the diagnostic performance of ARFI imaging in differentiating between benign and malignant thyroid nodules <1 cm. Materials and Methods. 173 pathologically proven thyroid nodules (77 benign, 96 malignant) in 157 patients were included in this study. Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of conventional ultrasound (US) and ARFI imaging in papillary thyroid microcarcinoma (PTMC). The independent risk factors for predicting PTMC were evaluated. Results. The mean SWV value of benign and malignant thyroid nodules were 2.57 ± 0.79 m/s (range: 0.90–4.92 m/s) and 3.88 ± 2.24 m/s (range: 1.49–9.00 m/s) (P = 0.000). Az for VTI elastography score was higher than that for hypoechoic, absence of halo sign, and type III vascularity (P < 0.05). The optimal cut-offs for VTI elastography score and SWV were score 4 and 3.10 m/s. Gender, hypoechoic, taller than wide, VTI elastography score ≥ 4, and SWV > 3.10 m/s had been found to be independent risk factors for predicting PTMC. Conclusion. ARFI elastography can provide elasticity information of PTMC quantitatively (VTQ) and directly reflects the overall elastic properties (VTI). Gender, hypoechogenicity, taller than wide, VTI elastography score ≥ 4, and SWV > 3.10 m/s are independent risk factors for predicting PTMC. ARFI elastography seems to be a new tool for the diagnosis of PTMC. PMID:25045673

  14. Scanning Tomographic Acoustic Microscopy

    NASA Astrophysics Data System (ADS)

    Wade, G.; Meyyappan, A.

    1988-07-01

    The technology for "seeing" with sound has an important and interesting history. Some of nature's creatures have been using sound waves for many millenia to image otherwise unobservable objects. The human species, lacking this natural ability, have overcome this deficiency by developing several different ultrasonic imaging techniques. acoustic microscopy is one such technique, which produces high resolution images of detailed structure of small objects in a non-destructive fashion. Two types of acoustic microscopes have evolved for industrial exploitation. They are the scanning laser acoustic microscope (SLAM) and the scanning acoustic microscope (SAM). In this paper, we review the principles of SLAM and describe how we use elements of SLAM to realize the scanning tomographic acoustic microscope (STAM). We describe the data acquisition process and the image reconstruction procedure. We also describe techniques to obtain projection data from different angles of wave incidence enabling us to reconstruct different planes of a complex specimen tomo-graphically. Our experimental results show that STAM is capable of producing high-quality high-resolution subsurface images.

  15. Ocean acoustic reverberation tomography.

    PubMed

    Dunn, Robert A

    2015-12-01

    Seismic wide-angle imaging using ship-towed acoustic sources and networks of ocean bottom seismographs is a common technique for exploring earth structure beneath the oceans. In these studies, the recorded data are dominated by acoustic waves propagating as reverberations in the water column. For surveys with a small receiver spacing (e.g., <10 km), the acoustic wave field densely samples properties of the water column over the width of the receiver array. A method, referred to as ocean acoustic reverberation tomography, is developed that uses the travel times of direct and reflected waves to image ocean acoustic structure. Reverberation tomography offers an alternative approach for determining the structure of the oceans and advancing the understanding of ocean heat content and mixing processes. The technique has the potential for revealing small-scale ocean thermal structure over the entire vertical height of the water column and along long survey profiles or across three-dimensional volumes of the ocean. For realistic experimental geometries and data noise levels, the method can produce images of ocean sound speed on a smaller scale than traditional acoustic tomography. PMID:26723303

  16. Observations of the volume flux of a seafloor hydrothermal plume using an acoustic imaging sonar

    NASA Astrophysics Data System (ADS)

    Xu, G.; Jackson, D. R.; Bemis, K. G.; Rona, P. A.

    2013-07-01

    We present a 26 day time series (October 2010) of physical properties (volume flux, flow velocity, expansion rate) of a vigorous deep-sea hydrothermal plume measured using our Cabled Observatory Vent Imaging Sonar (COVIS), which is connected to the Northeast Pacific Time Series Underwater Experiment Canada Cabled Observatory at the Main Endeavour Field on the Juan de Fuca Ridge. COVIS quantitatively monitors the initial buoyant rise of the plume from ˜5 m to ˜15 m above the vents. The time series exhibits temporal variations of the plume vertical volume flux (1.93-5.09 m3/s ), centerline vertical velocity component (0.11-0.24 m/s ) and expansion rate (0.082-0.21 m/m ); these variations have major spectral peaks at semidiurnal (˜2 cycle/day) and inertial oscillation (˜1.5 cycle/day) frequencies. The plume expansion rate (average ˜0.14 m/m ) is inversely proportional to the plume centerline vertical velocity component (coefficient of determination R2˜0.5). This inverse proportionality, as well as the semidiurnal frequency, indicates interaction between the plume and ambient ocean currents consistent with an entrainment of ambient seawater that increases with the magnitude of ambient currents. The inertial oscillations observed in the time series provide evidence for the influence of surface storms on the dynamics of hydrothermal plumes.

  17. A method of construction of information images of the acoustic signals of the human bronchopulmonary system

    NASA Astrophysics Data System (ADS)

    Bureev, A. Sh.; Zhdanov, D. S.; Zemlyakov, I. Yu.; Kiseleva, E. Yu.; Khokhlova, L. A.

    2015-11-01

    The present study focuses on the development of a method of identification of respiratory sounds and noises of a human naturally and in various pathological conditions. The existing approaches based on a simple method of frequency and time signal analysis, have insufficient specificity, efficiency and unambiguous interpretation of the results of a clinical study. An algorithm for a phase selection of respiratory cycles and analysis of respiratory sounds resulting from bronchi examination of a patient has been suggested. The algorithm is based on the method of phase timing analysis of bronchi phonograms. The results of the phase-frequency algorithm with high resolution reflects a time position of the traceable signals and the individual structure of recorded signals. This allows using the proposed method for the formation of information images (models) of the diagnostically significant fragments. A weight function, frequency parameters of which can be selectively modified, is used for this purpose. The vision of the weighting function is specific to each type of respiratory noise, traditionally referred to quality characteristics (wet or dry noise, crackling, etc.).

  18. Photoacoustic imaging with an acoustic lens detects prostate cancer cells labeled with PSMA-targeting near-infrared dye-conjugates

    NASA Astrophysics Data System (ADS)

    Dogra, Vikram; Chinni, Bhargava; Singh, Shalini; Schmitthenner, Hans; Rao, Navalgund; Krolewski, John J.; Nastiuk, Kent L.

    2016-06-01

    There is an urgent need for sensitive and specific tools to accurately image early stage, organ-confined human prostate cancers to facilitate active surveillance and reduce unnecessary treatment. Recently, we developed an acoustic lens that enhances the sensitivity of photoacoustic imaging. Here, we report the use of this device in conjunction with two molecular imaging agents that specifically target the prostate-specific membrane antigen (PSMA) expressed on the tumor cell surface of most prostate cancers. We demonstrate successful imaging of phantoms containing cancer cells labeled with either of two different PSMA-targeting agents, the ribonucleic acid aptamer A10-3.2 and a urea-based peptidomimetic inhibitor, each linked to the near-infrared dye IRDye800CW. By specifically targeting cells with these agents linked to a dye chosen for optimal signal, we are able to discriminate prostate cancer cells that express PSMA.

  19. Feasibility of High Frequency Acoustic Imaging for Inspection of Containments: Phase II

    SciTech Connect

    Rudzinsky, J.; Bondaryk, J.; Conti, M.

    1999-07-01

    The nuclear power industry is concerned with corrosive thinning of portions of the metallic pressure boundary, particularly in areas that are not directly accessible for inspection. This study investigated the feasibility of detecting these thickness degradations using ultrasonic imaging. A commercial ultrasonic system was used to carry out several full-scale, controlled laboratory experiments. Measurements of 0.5 MHz shear wave levels propagated in 25-mm-thick steel plate embedded in concrete showed 1.4-1.6 dB of signal loss for each centimeter of two-way travel in the steel plate (compared to previous numerical predictions of 3-4 dB), and 1.3 dB of signal loss per centimeter of two-way travel in steel plates embedded in concrete prior to setting of the concrete (i.e., plastic). Negligible losses were measured in plates with a decoupling treatment applied between the steel and concrete to simulate the unbonded portions of the pressure boundary. Scattered signals from straight slots of different size and shape were investigated. The return from a 4-mm-deep rectangular slots exhibited levels 23 dB down relative to incidence and 4-6 dB higher than those obtained from both ''v'' shaped and rounded slots of similar depth. The system displayed an input/output dynamic range of 125 dB and measurement variability less than 1-2dB. Based on these results, a 4-mm-deep, rounded degradation embedded 30 cm in concrete has expected returns of -73dB relative to the input and should therefore be detectable. Results of this and a prior study indicate that the technique has merit and should be developed more fully and demonstrated in the field.

  20. Acoustic Neuroma

    MedlinePlus

    An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...

  1. Full Elastic Waveform Search Engine for Near Surface Imaging

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Zhang, X.

    2014-12-01

    For processing land seismic data, the near-surface problem is often very complex and may severely affect our capability to image the subsurface. The current state-of-the-art technology for near surface imaging is the early arrival waveform inversion that solves an acoustic wave-equation problem. However, fitting land seismic data with acoustic wavefield is sometimes invalid. On the other hand, performing elastic waveform inversion is very time-consuming. Similar to a web search engine, we develop a full elastic waveform search engine that includes a large database with synthetic elastic waveforms accounting for a wide range of interval velocity models in the CMP domain. With each CMP gather of real data as an entry, the search engine applies Multiple-Randomized K-Dimensional (MRKD) tree method to find approximate best matches to the entry in about a second. Interpolation of the velocity models at CMP positions creates 2D or 3D Vp, Vs, and density models for the near surface area. The method does not just return one solution; it gives a series of best matches in a solution space. Therefore, the results can help us to examine the resolution and nonuniqueness of the final solution. Further, this full waveform search method can avoid the issues of initial model and cycle skipping that the method of full waveform inversion is difficult to deal with.

  2. Seismic wavefield propagation in 2D anisotropic media: Ray theory versus wave-equation simulation

    NASA Astrophysics Data System (ADS)

    Bai, Chao-ying; Hu, Guang-yi; Zhang, Yan-teng; Li, Zhong-sheng

    2014-05-01

    Despite the ray theory that is based on the high frequency assumption of the elastic wave-equation, the ray theory and the wave-equation simulation methods should be mutually proof of each other and hence jointly developed, but in fact parallel independent progressively. For this reason, in this paper we try an alternative way to mutually verify and test the computational accuracy and the solution correctness of both the ray theory (the multistage irregular shortest-path method) and the wave-equation simulation method (both the staggered finite difference method and the pseudo-spectral method) in anisotropic VTI and TTI media. Through the analysis and comparison of wavefield snapshot, common source gather profile and synthetic seismogram, it is able not only to verify the accuracy and correctness of each of the methods at least for kinematic features, but also to thoroughly understand the kinematic and dynamic features of the wave propagation in anisotropic media. The results show that both the staggered finite difference method and the pseudo-spectral method are able to yield the same results even for complex anisotropic media (such as a fault model); the multistage irregular shortest-path method is capable of predicting similar kinematic features as the wave-equation simulation method does, which can be used to mutually test each other for methodology accuracy and solution correctness. In addition, with the aid of the ray tracing results, it is easy to identify the multi-phases (or multiples) in the wavefield snapshot, common source point gather seismic section and synthetic seismogram predicted by the wave-equation simulation method, which is a key issue for later seismic application.

  3. AxiSEM and instaseis: Fast simulation of global wavefields across the frequency band

    NASA Astrophysics Data System (ADS)

    Nissen-Meyer, T.; van Driel, M.; Krischer, L.; Stähler, S. C.; Hosseini, K.; Leng, K.

    2015-12-01

    We present our seismic modeling methods AxiSEM and instaseis. These methods exploit recent developments in high-performance computing and suitable numerical methods for seismic wave propagation, while operating efficiently across the vast observable frequency spectrum of global waves in sparse yet realistic structures. AxiSEM (www.axisem.info and geodynamics.org) relies upon axisymmetric (including spherically symmetric) models, thereby satisfying a large fraction of observable data. The benefit of this method lies in the resultant dimensional collapse to two numerical dimensions, whereby the third azimuthal dimension is tackled analytically. For high-frequency wave propagation, this leads to 3-4 orders of magnitude speedup in computational cost compared to 3D domain discretizations. AxiSEM is highly scalable and accommodates efficient implementations of viscoelasticity and anisotropy. We will present benchmarks, data comparisons, a diverse range of applications from inner-core anisotropy to noise modeling and lowermost mantle structures, and wavefields for sensitivity kernels. We also touch upon ongoing efforts for linking computational cost to structural complexity in the vein of Occam's razor, eventually allowing for an adaptive rendition of 1D, 2D and 3D structures at optimally low computational cost, as well as 1D/3D hybrid approaches. Instaseis (www.instaseis.net) is a methodology to extract full, broadband and accurate waveforms instantaneously from wavefield databases computed with AxiSEM. This "once-and-for-all solution" relies on reciprocity and requires only two AxiSEM simulations to construct the databases, while allowing for arbitrary parameter changes (e.g. source, processing, structure) instantaneously with modest computational cost and storage requirements. The instaseis python package is integrated with ObsPy, contains a graphical user interface, and can be used for source inversion, noise simulations, finite-fault modeling, waveform tomography

  4. Geometric effect on a laboratory-scale wavefield inferred from a three-dimensional numerical simulation

    NASA Astrophysics Data System (ADS)

    Yoshimitsu, Nana; Furumura, Takashi; Maeda, Takuto

    2016-09-01

    The coda part of a waveform transmitted through a laboratory sample should be examined for the high-resolution monitoring of the sample characteristics in detail. However, the origin and propagation process of the later phases in a finite-sized small sample are very complicated with the overlap of multiple unknown reflections and conversions. In this study, we investigated the three-dimensional (3D) geometric effect of a finite-sized cylindrical sample to understand the development of these later phases. This study used 3D finite difference method simulation employing a free-surface boundary condition over a curved model surface and a realistic circular shape of the source model. The simulated waveforms and the visualized 3D wavefield in a stainless steel sample clearly demonstrated the process of multiple reflections and the conversions of the P and S waves at the side surface as well as at the top and bottom of the sample. Rayleigh wave propagation along the curved side boundary was also confirmed, and these waves dominate in the later portion of the simulated waveform with much larger amplitudes than the P and S wave reflections. The feature of the simulated waveforms showed good agreement with laboratory observed waveforms. For the simulation, an introduction of an absorbing boundary condition at the top and bottom of the sample made it possible to efficiently separate the contribution of the vertical and horizontal boundary effects in the simulated wavefield. This procedure helped to confirm the additional finding of vertically propagating multiple surface waves and their conversion at the corner of the sample. This new laboratory-scale 3D simulation enabled the appearance of a variety of geometric effects that constitute the later phases of the transmitted waves.

  5. Shallow-velocity models at the Kilauea Volcano, Hawaii, determined from array analyses of tremor wavefields

    USGS Publications Warehouse

    Saccorotti, G.; Chouet, B.; Dawson, P.

    2003-01-01

    The properties of the surface wavefield at Kilauea Volcano are analysed using data from small-aperture arrays of short-period seismometers deployed in and around the Kilauea caldera. Tremor recordings were obtained during two Japan-US cooperative experiments conducted in 1996 and 1997. The seismometers were deployed in three semi-circular arrays with apertures of 300, 300 and 400 m, and a linear array with length of 1680 m. Data are analysed using a spatio-temporal correlation technique well suited for the study of the stationary stochastic wavefields of Rayleigh and Love waves associated with volcanic activity and scattering sources distributed in and around the summit caldera. Spatial autocorrelation coefficients are obtained as a function of frequency and are inverted for the dispersion characteristics of Rayleigh and Love waves using a grid search that seeks phase velocities for which the L-2 norm between data and forward modelling operators is minimized. Within the caldera, the phase velocities of Rayleigh waves range from 1400 to 1800 m s-1 at 1 Hz down to 300-400 m s-1 at 10 Hz, and the phase velocities of Love waves range from 2600 to 400 m s-1 within the same frequency band. Outside the caldera, Rayleigh wave velocities range from 1800 to 1600 m s-1 at 1 Hz down to 260-360 m s-1 at 10 Hz, and Love wave velocities range from 600 to 150 m s-1 within the same frequency band. The dispersion curves are inverted for velocity structure beneath each array, assuming these dispersions represent the fundamental modes of Rayleigh and Love waves. The velocity structures observed at different array sites are consistent with results from a recent 3-D traveltime tomography of the caldera region, and point to a marked velocity discontinuity associated with the southern caldera boundary.

  6. Acoustic Seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  7. Acoustic seal

    NASA Technical Reports Server (NTRS)

    Steinetz, Bruce M. (Inventor)

    2006-01-01

    The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

  8. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H.D.; Busse, L.J.; Lemon, D.K.

    1983-10-25

    This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.

  9. Evaluating the Acoustic Effect of Over-the-Rotor Foam-Metal Liner Installed on a Low Speed Fan Using Virtual Rotating Microphone Imaging

    NASA Technical Reports Server (NTRS)

    Sutliff, Daniel L.; Dougherty, Robert P.; Walker, Bruce E.

    2010-01-01

    An in-duct beamforming technique for imaging rotating broadband fan sources has been used to evaluate the acoustic characteristics of a Foam-Metal Liner installed over-the-rotor of a low-speed fan. The NASA Glenn Research Center s Advanced Noise Control Fan was used as a test bed. A duct wall-mounted phased array consisting of several rings of microphones was employed. The data are mathematically resampled in the fan rotating reference frame and subsequently used in a conventional beamforming technique. The steering vectors for the beamforming technique are derived from annular duct modes, so that effects of reflections from the duct walls are reduced.

  10. Imaging and quantitative data acquisition of biological cell walls with Atomic Force Microscopy and Scanning Acoustic Microscopy

    SciTech Connect

    Tittmann, B. R.; Xi, X.

    2014-09-01

    This chapter demonstrates the feasibility of Atomic Force Microscopy (AFM) and High Frequency Scanning Acoustic Microscopy (HF-SAM) as tools to characterize biological tissues. Both the AFM and the SAM have shown to provide imaging (with different resolution) and quantitative elasticity measuring abilities. Plant cell walls with minimal disturbance and under conditions of their native state have been examined with these two kinds of microscopy. After descriptions of both the SAM and AFM, their special features and the typical sample preparation is discussed. The sample preparation is focused here on epidermal peels of onion scales and celery epidermis cells which were sectioned for the AFM to visualize the inner surface (closest to the plasma membrane) of the outer epidermal wall. The nm-wide cellulose microfibrils orientation and multilayer structure were clearly observed. The microfibril orientation and alignment tend to be more organized in older scales compared with younger scales. The onion epidermis cell wall was also used as a test analog to study cell wall elasticity by the AFM nanoindentation and the SAM V(z) feature. The novelty in this work was to demonstrate the capability of these two techniques to analyze isolated, single layered plant cell walls in their natural state. AFM nanoindentation was also used to probe the effects of Ethylenediaminetetraacetic acid (EDTA), and calcium ion treatment to modify pectin networks in cell walls. The results suggest a significant modulus increase in the calcium ion treatment and a slight decrease in EDTA treatment. To complement the AFM measurements, the HF-SAM was used to obtain the V(z) signatures of the onion epidermis. These measurements were focused on documenting the effect of pectinase enzyme treatment. The results indicate a significant change in the V(z) signature curves with time into the enzyme treatment. Thus AFM and HF-SAM open the door to a systematic nondestructive structure and mechanical property

  11. Angle-domain imaging condition for elastic reverse time migration

    NASA Astrophysics Data System (ADS)

    Yan, R.; Xie, X.; Wu, R.

    2010-12-01

    In exploration seismology, elastic reverse time migration (RTM) has spurred much interest in recent years because of the increased imaging challenges posed by complex subsurface targets and affordable computer resources such as Linux clusters. Elastic RTM reconstructs the source wavefields forward in time and receiver wavefields backward in time by finite difference method. It then applies an imaging condition that evaluates the match between source and receiver wavefields. To construct the image which describes the physical property of the medium, we prefer to separate the wavefields into P and S modes, and implement the imaging condition as cross-correlation of pure wave mode rather than of Cartesian component of the displacement wavefields. However, simple cross-correlation can cause some image problems which impede the further seismic interpretation. For example, PP image is contaminated by strong artifacts resulted from unwanted cross-correlation between diving wave, turning wave or back-scattered wave and their time-reversed counterpart; PS image suffers from polarization problem due to the polarity reversal of converted S-wave. We found it necessary to apply certain intrinsic properties (e.g., the wave propagation directions and particle motion information) in reconstructed wavefields in order to solve the problems exhibited in elastic RTM image. This paper presents a procedure to decompose the source and receiver wavefields into local plane waves in pure P and S modes. We generate the partial PP and PS images in angle domain by cross-correlating any combination of decomposed plane wave component, and then formulate an imaging condition as a product of an angle-domain operator and the partial images. The new angle-domain imaging condition substantially reduces the artifacts in the PP image and produces the PS image with correct polarizations. Synthetic examples demonstrate that the imaging condition works very well on producing clean and consistent image

  12. INTERFERENCE FRINGES OF SOLAR ACOUSTIC WAVES AROUND SUNSPOTS

    SciTech Connect

    Chou, Dean-Yi; Zhao Hui; Yang, Ming-Hsu; Liang, Zhi-Chao

    2012-10-20

    Solar acoustic waves are scattered by a sunspot due to the interaction between the acoustic waves and the sunspot. The sunspot, excited by the incident wave, generates the scattered wave. The scattered wave is added to the incident wave to form the total wave around the sunspot. The interference fringes between the scattered wave and the incident wave are visible in the intensity of the total wave because the coherent time of the incident wave is of the order of a wave period. The strength of the interference fringes anti-correlates with the width of temporal spectra of the incident wave. The separation between neighboring fringes increases with the incident wavelength and the sunspot size. The strength of the fringes increases with the radial order n of the incident wave from n = 0 to n = 2, and then decreases from n = 2 to n = 5. The interference fringes play a role analogous to holograms in optics. This study suggests the feasibility of using the interference fringes to reconstruct the scattered wavefields of the sunspot, although the quality of the reconstructed wavefields is sensitive to the noise and errors in the interference fringes.

  13. Finite-Difference Algorithm for Simulating 3D Electromagnetic Wavefields in Conductive Media

    NASA Astrophysics Data System (ADS)

    Aldridge, D. F.; Bartel, L. C.; Knox, H. A.

    2013-12-01

    Electromagnetic (EM) wavefields are routinely used in geophysical exploration for detection and characterization of subsurface geological formations of economic interest. Recorded EM signals depend strongly on the current conductivity of geologic media. Hence, they are particularly useful for inferring fluid content of saturated porous bodies. In order to enhance understanding of field-recorded data, we are developing a numerical algorithm for simulating three-dimensional (3D) EM wave propagation and diffusion in heterogeneous conductive materials. Maxwell's equations are combined with isotropic constitutive relations to obtain a set of six, coupled, first-order partial differential equations governing the electric and magnetic vectors. An advantage of this system is that it does not contain spatial derivatives of the three medium parameters electric permittivity, magnetic permeability, and current conductivity. Numerical solution methodology consists of explicit, time-domain finite-differencing on a 3D staggered rectangular grid. Temporal and spatial FD operators have order 2 and N, where N is user-selectable. We use an artificially-large electric permittivity to maximize the FD timestep, and thus reduce execution time. For the low frequencies typically used in geophysical exploration, accuracy is not unduly compromised. Grid boundary reflections are mitigated via convolutional perfectly matched layers (C-PMLs) imposed at the six grid flanks. A shared-memory-parallel code implementation via OpenMP directives enables rapid algorithm execution on a multi-thread computational platform. Good agreement is obtained in comparisons of numerically-generated data with reference solutions. EM wavefields are sourced via point current density and magnetic dipole vectors. Spatially-extended inductive sources (current carrying wire loops) are under development. We are particularly interested in accurate representation of high-conductivity sub-grid-scale features that are common

  14. Topological Acoustics

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-01

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers.

  15. Topological acoustics.

    PubMed

    Yang, Zhaoju; Gao, Fei; Shi, Xihang; Lin, Xiao; Gao, Zhen; Chong, Yidong; Zhang, Baile

    2015-03-20

    The manipulation of acoustic wave propagation in fluids has numerous applications, including some in everyday life. Acoustic technologies frequently develop in tandem with optics, using shared concepts such as waveguiding and metamedia. It is thus noteworthy that an entirely novel class of electromagnetic waves, known as "topological edge states," has recently been demonstrated. These are inspired by the electronic edge states occurring in topological insulators, and possess a striking and technologically promising property: the ability to travel in a single direction along a surface without backscattering, regardless of the existence of defects or disorder. Here, we develop an analogous theory of topological fluid acoustics, and propose a scheme for realizing topological edge states in an acoustic structure containing circulating fluids. The phenomenon of disorder-free one-way sound propagation, which does not occur in ordinary acoustic devices, may have novel applications for acoustic isolators, modulators, and transducers. PMID:25839273

  16. Nondiffuse elastic and anelastic passive imaging.

    PubMed

    Mulargia, Francesco; Castellaro, Silvia

    2010-03-01

    The property at the basis of passive acoustic imaging is that, taken any two points, one of them can be seen as the source of the waves and the other as the recording station. This property, which was shown to hold also in nondiffuse fields, is here exploited: (1) to allow an undistorted passive imaging through the simple use of the statistical mode to estimate wave velocity, (2) to determine the azimuth of the instantaneous Huygens sources of the noise wavefield, and (3) to measure, provided that the noise bandwidth is wide with respect to that of the local system, the material dissipation constant as a function of frequency. The authors applied this theory to study the seismic noise field in the Ravenna, North-Central Italy, shore area and found it capable to provide velocity dispersion curves matching those of independent surveys, to track the sources of seismic noise to a few major firms in Ravenna port, with the prevailing source switching at the time scale of seconds, and to measure the dissipation quality factor Q at approximately 20 independent of frequency in the range 1-30 Hz. PMID:20329839

  17. Optimization of real-time acoustical and mechanical monitoring of high intensity focused ultrasound (HIFU) treatment using harmonic motion imaging for high focused ultrasound (HMIFU).

    PubMed

    Hou, Gary Y; Marquet, Fabrice; Wang, Shutao; Konofagou, Elisa E

    2013-01-01

    Harmonic Motion Imaging (HMI) for Focused Ultrasound (HMIFU) is a recently developed high-intensity focused ultrasound (HIFU) treatment monitoring method with feasibilities demonstrated in silica, in vitro and in vivo. Its principle is based on emission of an Amplitude-modulated therapeutic ultrasound beam utilizing a therapeutic transducer to induce an oscillatory radiation force while tracking the focal tissue mechanical response during the HIFU treatment using a confocally-aligned diagnostic transducer. In order to translate towards the clinical implementation of HMIFU, a complete assessment study is required in order to investigate the optimal radiation force threshold for reliable monitoring the local tissue mechanical property changes, i.e., the estimation HMIFU displacement under thermal, acoustical, and mechanical effects within focal medium (i.e., boiling, cavitation, and nonlinearity) using biological specimen. In this study, HMIFU technique is applied on HIFU treatment monitoring on freshly excised ex vivo canine liver specimens. In order to perform the multi-characteristic assessment, the diagnostic transducer was operated as either a pulse-echo imager or Passive Cavitation Detector (PCD) to assess the acoustic and mechanical response, while a bare-wire thermocouple was used to monitor the focal temperature change. As the acoustic power of HIFU treatment was ranged from 2.3 to 11.4 W, robust HMI displacement was observed across the entire range. Moreover, an optimized range for high quality displacement monitoring was found to be between 3.6 to 5.2W, where displacement showed an increase followed by significant decrease, indicating a stiffening of focal medium due to thermal lesion formation, while the correlation coefficient was maintained above 0.95. PMID:24111176

  18. Infrasonic tremor wavefield of the Pu`u `Ō`ō crater complex and lava tube system, Hawaii, in April 2007

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Fee, David; GarcéS, Milton A.

    2010-12-01

    Long-lived effusive volcanism at the Pu`u `Ō`ō crater complex, Kilauea Volcano, Hawaii produces persistent infrasonic tremor that has been recorded almost continuously for months to years. Previous studies showed that this infrasonic tremor wavefield can be recorded at a range of >10 km. However, the low signal power of this tremor relative to ambient noise levels results in significant propagation effects on signal detectability at this range. In April 2007, we supplemented a broadband infrasound array at ˜12.5 km from Pu`u `Ō`ō (MENE) with a similar array at ˜2.4 km from the source (KIPU). The additional closer-range data enable further evaluation of tropospheric propagation effects and provide higher signal-to-noise ratios for studying volcanic source processes. The infrasonic tremor source appears to consist of at least two separate physical processes. We suggest that bubble cloud oscillation in a roiling magma conduit beneath the crater complex may produce a broadband component of the tremor. Low-frequency sound sourced in a shallow magma conduit may radiate infrasound efficiently into the atmosphere due to the anomalous transparency of the magma-air interface. We further propose that more sharply peaked tones with complex temporal evolution may result from oscillatory interactions of a low-velocity gas jet with solid vent boundaries in a process analogous to the hole tone or whistler nozzle. The infrasonic tremor arrives with a median azimuth of ˜67° at KIPU. Additional infrasonic signals and audible sounds originating from the extended lava tube system to the south of the crater complex (median azimuth ˜77°) coincided with turbulent degassing activity at a new lava tube skylight. Our observations indicate that acoustic studies may aid in understanding persistent continuous degassing and unsteady flow dynamics at Kilauea Volcano.

  19. Acoustic neuroma

    MedlinePlus

    Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor ... 177. Battista RA. Gamma knife radiosurgery for vestibular schwannoma. Otolaryngol Clin North Am . 2009;42:635-654. ...

  20. Acoustic wave-equation-based earthquake location

    NASA Astrophysics Data System (ADS)

    Tong, Ping; Yang, Dinghui; Liu, Qinya; Yang, Xu; Harris, Jerry

    2016-04-01

    We present a novel earthquake location method using acoustic wave-equation-based traveltime inversion. The linear relationship between the location perturbation (δt0, δxs) and the resulting traveltime residual δt of a particular seismic phase, represented by the traveltime sensitivity kernel K(t0, xs) with respect to the earthquake location (t0, xs), is theoretically derived based on the adjoint method. Traveltime sensitivity kernel K(t0, xs) is formulated as a convolution between the forward and adjoint wavefields, which are calculated by numerically solving two acoustic wave equations. The advantage of this newly derived traveltime kernel is that it not only takes into account the earthquake-receiver geometry but also accurately honours the complexity of the velocity model. The earthquake location is obtained by solving a regularized least-squares problem. In 3-D realistic applications, it is computationally expensive to conduct full wave simulations. Therefore, we propose a 2.5-D approach which assumes the forward and adjoint wave simulations within a 2-D vertical plane passing through the earthquake and receiver. Various synthetic examples show the accuracy of this acoustic wave-equation-based earthquake location method. The accuracy and efficiency of the 2.5-D approach for 3-D earthquake location are further verified by its application to the 2004 Big Bear earthquake in Southern California.

  1. Regional seismic wavefield computation on a 3-D heterogeneous Earth model by means of coupled traveling wave synthesis

    USGS Publications Warehouse

    Pollitz, F.F.

    2002-01-01

    I present a new algorithm for calculating seismic wave propagation through a three-dimensional heterogeneous medium using the framework of mode coupling theory originally developed to perform very low frequency (f < ???0.01-0.05 Hz) seismic wavefield computation. It is a Greens function approach for multiple scattering within a defined volume and employs a truncated traveling wave basis set using the locked mode approximation. Interactions between incident and scattered wavefields are prescribed by mode coupling theory and account for the coupling among surface waves, body waves, and evanescent waves. The described algorithm is, in principle, applicable to global and regional wave propagation problems, but I focus on higher frequency (typically f ??????0.25 Hz) applications at regional and local distances where the locked mode approximation is best utilized and which involve wavefields strongly shaped by propagation through a highly heterogeneous crust. Synthetic examples are shown for P-SV-wave propagation through a semi-ellipsoidal basin and SH-wave propagation through a fault zone.

  2. Effectiveness of imaging seismic attenuation using visco-acoustic full waveform tomography: Examples from the Seattle Fault Zone and Northern Perth Basin

    NASA Astrophysics Data System (ADS)

    Takam Takougang, E.; Calvert, A. J.

    2012-12-01

    Attenuation characterizes the decrease in amplitude of seismic waves as they propagate away from the source. A seismic wave propagating in the subsurface will suffer from two types of attenuation: Intrinsic attenuation and scattering attenuation. Scattering attenuation is due to small scale heterogeneity in the subsurface, whereas intrinsic attenuation arises from inelastic rock properties. Intrinsic attenuation can provide key information about the subsurface, which can be of value to the mining as well as the oil and gas industry. However, accurate imaging of intrinsic seismic attenuation using visco-acoustic full-waveform tomography is not straight forward. Attenuation models recovered by visco-acoustic waveform tomography are often contain contaminated by scattering effects as well as elastic mode conversion artefacts due to the inability of the visco-acoustic approximation to perfectly predict the amplitude of visco-elastic field data. The effect of scattering can be reduced if a velocity model with a high resolution is used. This usually necessitates a two-step inversion approach consisting of first recovering the velocity model and later, the attenuation model. In this study, we present a specific preconditioning of the data based on matching the amplitude variation with offset (AVO) of the field and modelled visco-acoustic data, and a specific inversion approach based on a sequential recovering of the seismic velocity and attenuation models using the visco-acoustic approximation. Our purpose is to improve the quality of the recovered attenuation model by decoupling the reconstruction of velocity and attenuation, thus reducing artefacts. We apply the method to two different areas: The Seattle Fault Zone in Puget Sound in the northwestern USA, using marine seismic reflection data from the Seismic Hazards investigation in Puget Sound (SHIPS) survey collected in 1998, and the Allanooka area within the Northern Perth Basin using high resolution seismic

  3. Application Of The Time-Frequency Polarization Analysis Of The Wavefield For Seismic Noise Array Processing

    NASA Astrophysics Data System (ADS)

    Galiana-Merino, J. J.; Rosa-Cintas, S.; Rosa-Herranz, J. L.; Molina-Palacios, S.; Martinez-Espla, J. J.

    2011-12-01

    Microzonation studies using ambient noise measurements constitute an extended and useful procedure for determine the local soil characteristics and its response due to an earthquake. Several methods exist for analyzing the noise measurements, being the most popular the horizontal-to-vertical spectral ratio (H/V) and the array techniques, i.e. the frequency-wavenumber (F-K) transform. Many works exist about this topic and it stills being an ongoing debate about ambient noise composition, whether body or surface waves constitute most of it, showing the importance of identifying the different kinds of waves presents in a seismic record. In this work we utilize a new method of time-frequency polarization analysis, based on the stationary wavelet packet transform, to investigate how the polarization characteristics of the wavefield influence in the application of ambient noise techniques. The signals are divided in different bands, according to their reciprocal ellipticity values and then the H/V method and the F-K array analysis are computed for each band. The qualitative and quantitative comparison between the original curve and the obtained for the analyzed intervals provide information about the signals composition, showing that the major components of the seismic noise present reciprocal ellipticity values lower than 0.5. The efficient application of the studied techniques by using just the main a part of the entire signal, [0 - 0.5], is also evaluated, showing favorable results.

  4. Three-dimensional laser optoacoustic and laser ultrasound imaging system for biomedical research

    NASA Astrophysics Data System (ADS)

    Ermilov, Sergey A.; Su, Richard; Conjusteau, Andre; Oruganti, Tanmayi; Wang, Kun; Anis, Fatima; Anastasio, Mark A.; Oraevsky, Alexander A.

    2015-03-01

    In this work, we introduce an improved prototype of the imaging system that combines three-dimensional optoacoustic tomography (3D-OAT) and laser ultrasound tomography slicer (2D-LUT) to obtain coregistered maps of tissue optical absorption and speed of sound (SOS). The imaging scan is performed by a 360 degree rotation of a phantom/mouse with respect to a static arc-shaped array of ultrasonic transducers. A Q-switched laser system is used to establish optoacoustic illumination pattern appropriate for deep tissue imaging with a tunable (730-840 nm) output wavelengths operated at 10 Hz pulse repetition rate. For the LUT slicer scans, the array is pivoted by 90 degrees with respect to the central transducers providing accurate registration of optoacoustic and SOS maps, the latter being reconstructed using waveform inversion with source encoding (WISE) technique. The coregistered OAT-LUT modality is validated by imaging a phantom and a live mouse. SOS maps acquired in the imaging system can be employed by an iterative optoacoustic reconstruction algorithm capable of compensating for acoustic wavefield aberrations. The most promising applications of the imaging system include 3D angiography, cancer research, and longitudinal studies of biological distributions of optoacoustic contrast agents (carbon nanotubes, metal plasmonic nanoparticles, fluorophores, etc.).

  5. Acoustic hemostasis

    NASA Astrophysics Data System (ADS)

    Crum, Lawrence; Beach, Kirk; Carter, Stephen; Chandler, Wayne; Curra, Francesco; Kaczkowski, Peter; Keilman, George; Khokhlova, Vera; Martin, Roy; Mourad, Pierre; Vaezy, Shahram

    2000-07-01

    In cases of severe injury, physicians speak of a "golden hour"—a brief grace period in which quickly applied, proper therapy can save the life of the patient. Much of this mortality results from exsanguination, i.e., bleeding to death—often from internal hemorrhage. The inability of a paramedic to treat breaches in the vascular system deep within the body or to stem the loss of blood from internal organs is a major reason for the high level of mortality associated with blunt trauma. We have undertaken an extensive research program to treat the problem of internal bleeding. Our approach is as follows: (a) We use scanning ultrasound to identify internal bleeding and hemorrhage, (b) we use ultrasound imaging to locate specific breaches in the vascular system, both from damaged vessels and gross damage to the capillary bed, and (c) we use High Intensity Focused Ultrasound (HIFU) to treat the damaged region and to induce hemostasis. We present a general review of this research with some emphasis on the role of nonlinear acoustics.

  6. Musical Acoustics

    NASA Astrophysics Data System (ADS)

    Gough, Colin

    This chapter provides an introduction to the physical and psycho-acoustic principles underlying the production and perception of the sounds of musical instruments. The first section introduces generic aspects of musical acoustics and the perception of musical sounds, followed by separate sections on string, wind and percussion instruments.

  7. A rail system for circular synthetic aperture sonar imaging and acoustic target strength measurements: Design/operation/preliminary results

    NASA Astrophysics Data System (ADS)

    Kennedy, J. L.; Marston, T. M.; Lee, K.; Lopes, J. L.; Lim, R.

    2014-01-01

    A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [Work Supported by the U.S. Office of Naval Research and

  8. A rail system for circular synthetic aperture sonar imaging and acoustic target strength measurements: design/operation/preliminary results.

    PubMed

    Kennedy, J L; Marston, T M; Lee, K; Lopes, J L; Lim, R

    2014-01-01

    A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [Work Supported by the U.S. Office of Naval Research and

  9. Going to high frequency for full waveform inversion of teleseismic wavefields based upon a SEM-DSM hybrid method and massive High-Performance Computing

    NASA Astrophysics Data System (ADS)

    Komatitsch, Dimitri; Monteiller, Vadim; Chevrot, Sébastien; Wang, Yi; Durochat, Clément

    2015-04-01

    We present a method for high-resolution imaging of lithospheric structures based on full waveform inversion of teleseismic wavefields. We model the propagation of seismic waves using our recently developed Direct Solution Method (DSM) / Spectral-Element Method (SEM) hybrid technique, which allows us to simulate the propagation of short period teleseismic waves through a regional 3-D model. We implement an iterative quasi-Newton method based upon the L-BFGS algorithm, with a gradient of the misfit function computed with the adjoint-state method. Compared to gradient or conjugate-gradient methods, the L-BFGS algorithm finds solutions that better explain the observed waveforms, and at a much faster convergence rate. We illustrate the potential of this method on a synthetic test case that consists in a crustal model with a crustal discontinuity at 25 km depth and a sharp Moho jump. This simple model contains short and long wavelength heterogeneities along both the lateral and vertical dimensions. In order to do that successfully we resort to high-performance computing on supercomputing clusters using an improved version of our SPECFEM3D open-source software package, which exhibits excellent scalability on parallel machines.

  10. Radiation-force-based estimation of acoustic attenuation using harmonic motion imaging (HMI) in phantoms and in vitro livers before and after HIFU ablation.

    PubMed

    Chen, Jiangang; Hou, Gary Y; Marquet, Fabrice; Han, Yang; Camarena, Francisco; Konofagou, Elisa

    2015-10-01

    Acoustic attenuation represents the energy loss of the propagating wave through biological tissues and plays a significant role in both therapeutic and diagnostic ultrasound applications. Estimation of acoustic attenuation remains challenging but critical for tissue characterization. In this study, an attenuation estimation approach was developed using the radiation-force-based method of harmonic motion imaging (HMI). 2D tissue displacement maps were acquired by moving the transducer in a raster-scan format. A linear regression model was applied on the logarithm of the HMI displacements at different depths in order to estimate the acoustic attenuation. Commercially available phantoms with known attenuations (n = 5) and in vitro canine livers (n = 3) were tested, as well as HIFU lesions in in vitro canine livers (n = 5). Results demonstrated that attenuations obtained from the phantoms showed a good correlation (R² = 0.976) with the independently obtained values reported by the manufacturer with an estimation error (compared to the values independently measured) varying within the range of 15-35%. The estimated attenuation in the in vitro canine livers was equal to 0.32   ±   0.03 dB cm(-1) MHz(-1), which is in good agreement with the existing literature. The attenuation in HIFU lesions was found to be higher (0.58   ±   0.06 dB cm(-1) MHz(-1)) than that in normal tissues, also in agreement with the results from previous publications. Future potential applications of the proposed method include estimation of attenuation in pathological tissues before and after thermal ablation. PMID:26371501

  11. Radiation-force-based estimation of acoustic attenuation using harmonic motion imaging (HMI) in phantoms and in vitro livers before and after HIFU ablation

    NASA Astrophysics Data System (ADS)

    Chen, Jiangang; Hou, Gary Y.; Marquet, Fabrice; Han, Yang; Camarena, Francisco; Konofagou, Elisa

    2015-10-01

    Acoustic attenuation represents the energy loss of the propagating wave through biological tissues and plays a significant role in both therapeutic and diagnostic ultrasound applications. Estimation of acoustic attenuation remains challenging but critical for tissue characterization. In this study, an attenuation estimation approach was developed using the radiation-force-based method of harmonic motion imaging (HMI). 2D tissue displacement maps were acquired by moving the transducer in a raster-scan format. A linear regression model was applied on the logarithm of the HMI displacements at different depths in order to estimate the acoustic attenuation. Commercially available phantoms with known attenuations (n=5 ) and in vitro canine livers (n=3 ) were tested, as well as HIFU lesions in in vitro canine livers (n=5 ). Results demonstrated that attenuations obtained from the phantoms showed a good correlation ({{R}2}=0.976 ) with the independently obtained values reported by the manufacturer with an estimation error (compared to the values independently measured) varying within the range of 15-35%. The estimated attenuation in the in vitro canine livers was equal to 0.32   ±   0.03 dB cm-1 MHz-1, which is in good agreement with the existing literature. The attenuation in HIFU lesions was found to be higher (0.58   ±   0.06 dB cm-1 MHz-1) than that in normal tissues, also in agreement with the results from previous publications. Future potential applications of the proposed method include estimation of attenuation in pathological tissues before and after thermal ablation.

  12. Statistical redundancy of instantaneous phases: theory and application to the seismic ambient wavefield

    NASA Astrophysics Data System (ADS)

    Gaudot, Ianis; Beucler, Éric; Mocquet, Antoine; Schimmel, Martin; Le Feuvre, Mathieu

    2016-04-01

    In order to detect possible signal redundancies in the seismic ambient wavefield, we develop a new method based on pairwise comparisons among a set of synchronous time-series. This approach is based on instantaneous phase coherence statistics. The first and second moments of the pairwise phase coherence distribution are used to characterize the phase randomness. Both theory and synthetic experiments show that, for perfect phase randomness, the theoretical values of the mean and variance are equal to 0 and 1 ‑ 2/π, respectively. As a consequence, any deviation from these values indicates the presence of a redundant phase in the raw continuous signal. Using the ergodicity property of a random signal, we split an initial time-series into a set of synchronous signals. This allows us to detect and to quantify the repetitiveness of any possible temporally persistent and spatially localized source, during a given period of observation. In the case of the detection of a redundant phase, individual coherences (one trace against all others) quantify the contribution of each time-series independently. A previously detected 26 s period microseismic source located near the Gulf of Guinea is used to illustrate one of the possible ways of handling phase coherence statistics. We use the continuous vertical component data recorded during the month of 2004 August by four broad-band stations of the Federation of Digital Seismography Network. To compute coherence statistics among a set composed of a sufficient number of synchronous traces, the raw seismic signal is split into 372 2-hr sliding time windows. Only the basic signal processing steps (including removing the mean, trend and the instrumental response) are applied. After bandpass filtering the data between 23 and 32 s periods, the 2-hr time-series are cross-correlated, leading to a set of 372 synchronous cross-correlations for each station pair. We observe that, for all station pairs, the mean overall coherence value is

  13. Ray dynamics in a long-range acoustic propagation experiment.

    PubMed

    Beron-Vera, Francisco J; Brown, Michael G; Colosi, John A; Tomsovic, Steven; Virovlyansky, Anatoly L; Wolfson, Michael A; Zaslavsky, George M

    2003-09-01

    A ray-based wave-field description is employed in the interpretation of broadband basin-scale acoustic propagation measurements obtained during the Acoustic Thermometry of Ocean Climate program's 1994 Acoustic Engineering Test. Acoustic observables of interest are wavefront time spread, probability density function (PDF) of intensity, vertical extension of acoustic energy in the reception finale, and the transition region between temporally resolved and unresolved wavefronts. Ray-based numerical simulation results that include both mesoscale and internal-wave-induced sound-speed perturbations are shown to be consistent with measurements of all the aforementioned observables, even though the underlying ray trajectories are predominantly chaotic, that is, exponentially sensitive to initial and environmental conditions. Much of the analysis exploits results that relate to the subject of ray chaos; these results follow from the Hamiltonian structure of the ray equations. Further, it is shown that the collection of the many eigenrays that form one of the resolved arrivals is nonlocal, both spatially and as a function of launch angle, which places severe restrictions on theories that are based on a perturbation expansion about a background ray. PMID:14514177

  14. Array analysis of regional Pn and Pg wavefields from the Nevada Test Site

    SciTech Connect

    Leonard, M.A. . Dept. of Geology and Geophysics Lawrence Berkeley Lab., CA )

    1991-06-01

    Small-aperture high-frequency seismic arrays with dimensions of a few kilometers or less, can improve our ability to seismically monitor compliance with a low-yield Threshold Test Ban Treaty. This work studies the characteristics and effectiveness of array processing of the regional Pn and Pg wavefields generated by underground nuclear explosions at the Nevada Test Site. Waveform data from the explosion HARDIN (m{sub b} = 5.5) is recorded at a temporary 12-element, 3-component, 1.5 km-aperture array sited in an area of northern Nevada. The explosions VILLE (m{sub b} = 4.4) and SALUT (m{sub b} = 5.5) are recorded at two arrays sited in the Mojave desert, one a 96-element vertical-component 7 km-aperture array and the other a 155-element vertical-component 4 km-aperture array. Among the mean spectra for the m{sub b} = 5.5 events there are significant differences in low-frequency spectral amplitudes between array sites. The spectra become nearly identical beyond about 6 Hz. Spectral ratios are used to examine seismic source properties and the partitioning of energy between Pn and Pg. Frequency-wavenumber analysis at the 12-element array is used to obtain estimates of signal gain, phase velocity, and source azimuth. This analysis reveals frequency-dependent biases in velocity and azimuth of the coherent Pn and Pg arrivals. Signal correlation, the principal factor governing array performance, is examined in terms of spatial coherence estimates. The coherence is found to vary between the three sites. In all cases the coherence of Pn is greater than that for Pg. 81 refs., 92 figs., 5 tabs.

  15. Acoustic-emission linear-pulse holography

    SciTech Connect

    Collins, H.D.; Lemon, D.K.; Busse, L.J.

    1982-06-01

    This paper describes Acoustic Emission Linear Pulse Holography which combines the advantages of linear imaging and acoustic emission into a single NDE inspection system. This unique system produces a chronological linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. Conventional linear holographic imaging uses an ultrasonic transducer to transmit energy into the volume being imaged. When the crack or defect reflects that energy, the crack acts as a new source of acoustic waves. To formulate an image of that source, a receiving transducer is scanned over the volume of interest and the phase of the received signals is measured at successive points on the scan. The innovation proposed here is the utilization of the crack generated acoustic emission as the acoustic source and generation of a line image of the crack as it grows. A thirty-two point sampling array is used to construct phase-only linear holograms of simulated acoustic emission sources on large metal plates. The phases are calculated using the pulse time-of-flight (TOF) times from the reference transducer to the array of receivers. Computer reconstruction of the image is accomplished using a one-dimensional FFT algorithm (i.e., backward wave). Experimental results are shown which graphically illustrate the unique acoustic emission images of a single point and a linear crack in a 100 mm x 1220 mm x 1220 mm aluminum plate.

  16. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  17. Acoustic Neuroma

    MedlinePlus

    ... slow growing tumor which arise primarily from the vestibular portion of the VIII cranial nerve and lie ... you have a "brain tumor" called acoustic neuroma (vestibular schwannoma). You think you are the only one ...

  18. Acoustic Holography

    NASA Astrophysics Data System (ADS)

    Kim, Yang-Hann

    One of the subtle problems that make noise control difficult for engineers is the invisibility of noise or sound. A visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical (or numerical) means for visualizing the sound field have been attempted, and as a result, a great deal of progress has been made. However, most of these numerical methods are not quite ready for practical applications to noise control problems. In the meantime, rapid progress with instrumentation has made it possible to use multiple microphones and fast signal-processing systems. Although these systems are not perfect, they are useful. A state-of-the-art system has recently become available, but it still has many problematic issues; for example, how can one implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently, it is often difficult to determine the origin of the noise and the spatial distribution of the noise field. Section 26.2 of this chapter introduces a brief history, which is associated with sound visualization, acoustic source identification methods and what has been accomplished with a line or surface array. Section 26.2.3 introduces difficulties and recent studies, including de-Dopplerization and de-re verberation methods, both essential for visualizing a moving noise source, such as occurs for cars or trains. This section also addresses what produces ambiguity in realizing real sound sources in a room or closed space. Another major issue associated with sound/noise visualization is whether or not we can distinguish between mutual dependencies of noise in space (Sect. 26.2.4); for example, we are asked to answer the question, Can we see two birds singing or one bird with two beaks?

  19. Acoustic Holography

    NASA Astrophysics Data System (ADS)

    Kim, Yang-Hann

    One of the subtle problems that make noise control difficult for engineers is the invisibility of noise or sound. A visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical (or numerical) means for visualizing the sound field have been attempted, and as a result, a great deal of progress has been made. However, most of these numerical methods are not quite ready for practical applications to noise control problems. In the meantime, rapid progress with instrumentation has made it possible to use multiple microphones and fast signal-processing systems. Although these systems are not perfect, they are useful. A state-of-the-art system has recently become available, but it still has many problematic issues; for example, how can one implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently, it is often difficult to determine the origin of the noise and the spatial distribution of the noise field. Section 26.2 of this chapter introduces a brief history, which is associated with "sound visualization," acoustic source identification methods and what has been accomplished with a line or surface array. Section 26.2.3 introduces difficulties and recent studies, including de-Dopplerization and de-reverberation methods, both essentialfor visualizing a moving noise source, such as occurs for cars or trains. This section also addresses what produces ambiguity in realizing real sound sources in a room or closed space. Another major issue associated with sound/noise visualization is whether or not we can distinguish between mutual dependencies of noise in space (Sect. 26.2.4); for example, we are asked to answer the question, "Can we see two birds singing or one bird with two beaks?"

  20. Revealing, identifying, and assessing flaws in operating equipment by the acoustic emission image recognition method under strong background noise condition

    NASA Astrophysics Data System (ADS)

    Muravin, Gregory; Muravin, Boris; Lezvisky, Ludmila

    2004-05-01

    The analysis has shown that high pressure and high temperature piping in fossil and nuclear power plants suffer from unexpected and rarely predictable failures. To guarantee operational safety and to prevent failures authors have performed the complex investigations and have created Quantitative Acoustic Emission NDI technology for revealing, identifying and assessing flaws in equipment operated under strong background noise condition. These enabled: Overall inspection of the piping operated under stress, temperature, pressure, steam flow and loading, variation. Locating suspected zones and zones of flaw development with low J-integral value and the great variation of the dynamic range of flaws danger level. Identification of flaw types and their danger level. Detection of defective components in service prior to shut down. The continuous and the burst Acoustic Emission (AE) were used in combination as an information tool. As result, the significant number of flaws such as creep at stage 3a-3b, closed-edge micro-cracks, systems of randomly dispersed pores and inclusions, plastic deformation development around them, or/and individual micro-cracking were revealed, identified and assessed in 50 operating high energy piping. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods as TOFD, X-ray, replication, metallurgical investigations, etc. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods such as TOFD, X-ray, replication, metallurgical investigations, etc

  1. Wind, waves, and acoustic background levels at Station ALOHA

    NASA Astrophysics Data System (ADS)

    Duennebier, Fred K.; Lukas, Roger; Nosal, Eva-Marie; Aucan, JéRome; Weller, Robert A.

    2012-03-01

    Frequency spectra from deep-ocean near-bottom acoustic measurements obtained contemporaneously with wind, wave, and seismic data are described and used to determine the correlations among these data and to discuss possible causal relationships. Microseism energy appears to originate in four distinct regions relative to the hydrophone: wind waves above the sensors contribute microseism energy observed on the ocean floor; a fraction of this local wave energy propagates as seismic waves laterally, and provides a spatially integrated contribution to microseisms observed both in the ocean and on land; waves in storms generate microseism energy in deep water that travels as seismic waves to the sensor; and waves reflected from shorelines provide opposing waves that add to the microseism energy. Correlations of local wind speed with acoustic and seismic spectral time series suggest that the local Longuet-Higgins mechanism is visible in the acoustic spectrum from about 0.4 Hz to 80 Hz. Wind speed and acoustic levels at the hydrophone are poorly correlated below 0.4 Hz, implying that the microseism energy below 0.4 Hz is not typically generated by local winds. Correlation of ocean floor acoustic energy with seismic spectra from Oahu and with wave spectra near Oahu imply that wave reflections from Hawaiian coasts, wave interactions in the deep ocean near Hawaii, and storms far from Hawaii contribute energy to the seismic and acoustic spectra below 0.4 Hz. Wavefield directionality strongly influences the acoustic spectrum at frequencies below about 2 Hz, above which the acoustic levels imply near-isotropic surface wave directionality.

  2. 4-D imaging of seepage in earthen embankments with time-lapse inversion of self-potential data constrained by acoustic emissions localization

    NASA Astrophysics Data System (ADS)

    Rittgers, J. B.; Revil, A.; Planes, T.; Mooney, M. A.; Koelewijn, A. R.

    2015-02-01

    New methods are required to combine the information contained in the passive electrical and seismic signals to detect, localize and monitor hydromechanical disturbances in porous media. We propose a field experiment showing how passive seismic and electrical data can be combined together to detect a preferential flow path associated with internal erosion in a Earth dam. Continuous passive seismic and electrical (self-potential) monitoring data were recorded during a 7-d full-scale levee (earthen embankment) failure test, conducted in Booneschans, Netherlands in 2012. Spatially coherent acoustic emissions events and the development of a self-potential anomaly, associated with induced concentrated seepage and internal erosion phenomena, were identified and imaged near the downstream toe of the embankment, in an area that subsequently developed a series of concentrated water flows and sand boils, and where liquefaction of the embankment toe eventually developed. We present a new 4-D grid-search algorithm for acoustic emissions localization in both time and space, and the application of the localization results to add spatially varying constraints to time-lapse 3-D modelling of self-potential data in the terms of source current localization. Seismic signal localization results are utilized to build a set of time-invariant yet spatially varying model weights used for the inversion of the self-potential data. Results from the combination of these two passive techniques show results that are more consistent in terms of focused ground water flow with respect to visual observation on the embankment. This approach to geophysical monitoring of earthen embankments provides an improved approach for early detection and imaging of the development of embankment defects associated with concentrated seepage and internal erosion phenomena. The same approach can be used to detect various types of hydromechanical disturbances at larger scales.

  3. Microfiber interferometric acoustic transducers.

    PubMed

    Wang, Xiuxin; Jin, Long; Li, Jie; Ran, Yang; Guan, Bai-Ou

    2014-04-01

    Acoustic and ultrasonic transducers are key components in biomedical information technology, which has been applied in medical diagnosis, photoacoustic endoscopy and photoacoustic imaging. In this paper, an acoustic transducer based on Fabry-Perot interferometer (FPI) fabricated in a microscaled optical fiber is demonstrated. The transducer is fabricated by forming two wavelength-matched Bragg gratings into the microfiber by means of side illumination with a 193nm excimer laser. When placing the transducer in water, the applied acoustic signal periodically changes the refractive index (RI) of the surrounding liquid and modulates the transmission of the FPI based on the evanescent-field interaction between the liquid and the transmitting light. As a result, the acoustic signal can be constructed with a tunable laser whose output wavelength is located at the slope of the inteferometric fringes. The transducer presents a sensitivity of 10 times higher than the counterparts fabricated in conventional singlemode fibers and has great potential to achieve higher resolution for photoacoustic imaging due to its reduced diameter. PMID:24718189

  4. System and method to create three-dimensional images of non-linear acoustic properties in a region remote from a borehole

    DOEpatents

    Vu, Cung; Nihei, Kurt T.; Schmitt, Denis P.; Skelt, Christopher; Johnson, Paul A.; Guyer, Robert; TenCate, James A.; Le Bas, Pierre-Yves

    2013-01-01

    In some aspects of the disclosure, a method for creating three-dimensional images of non-linear properties and the compressional to shear velocity ratio in a region remote from a borehole using a conveyed logging tool is disclosed. In some aspects, the method includes arranging a first source in the borehole and generating a steered beam of elastic energy at a first frequency; arranging a second source in the borehole and generating a steerable beam of elastic energy at a second frequency, such that the steerable beam at the first frequency and the steerable beam at the second frequency intercept at a location away from the borehole; receiving at the borehole by a sensor a third elastic wave, created by a three wave mixing process, with a frequency equal to a difference between the first and second frequencies and a direction of propagation towards the borehole; determining a location of a three wave mixing region based on the arrangement of the first and second sources and on properties of the third wave signal; and creating three-dimensional images of the non-linear properties using data recorded by repeating the generating, receiving and determining at a plurality of azimuths, inclinations and longitudinal locations within the borehole. The method is additionally used to generate three dimensional images of the ratio of compressional to shear acoustic velocity of the same volume surrounding the borehole.

  5. Assessment of the Stiffness of Major Salivary Glands in Primary Sjögren's Syndrome through Quantitative Acoustic Radiation Force Impulse Imaging.

    PubMed

    Zhang, Shanshan; Zhu, Jiaan; Zhang, Xia; He, Jing; Li, Jianguo

    2016-03-01

    The purpose of the study described here was to evaluate salivary gland stiffness in primary Sjögren's syndrome (pSS) via acoustic radiation force impulse imaging, including Virtual Touch tissue quantification (VTQ) and Virtual Touch tissue imaging quantification (VTIQ). Twenty-one patients with pSS and 11 healthy patients were included, and the paired parotid and submandibular glands of all of the patients were examined using VTQ and VTIQ. Differences between the two groups were compared with independent and paired t-tests. The VTQ value for the parotid in the pSS group was significantly higher than that obtained for the control group (1.33 ± 0.22 and 1.18 ± 0.04 m/s, respectively, p < 0.01). The VTIQ values for the parotid and submandibular gland were both significantly higher in the pSS group than in the control group (p < 0.05). In the pSS group, a positive correlation was observed between the VTQ and VTIQ results for the parotid and submandibular glands. In summary, the stiffness of the major salivary glands in patients with pSS was increased compared with that of patients with normal glands. This finding indicates that VTQ and VTIQ imaging may be valuable adjuncts to gray-scale ultrasonography for the clinical diagnosis of pSS. PMID:26715188

  6. Identifying Clinically Significant Prostate Cancers using 3-D In Vivo Acoustic Radiation Force Impulse Imaging with Whole-Mount Histology Validation.

    PubMed

    Palmeri, Mark L; Glass, Tyler J; Miller, Zachary A; Rosenzweig, Stephen J; Buck, Andrew; Polascik, Thomas J; Gupta, Rajan T; Brown, Alison F; Madden, John; Nightingale, Kathryn R

    2016-06-01

    Overly aggressive prostate cancer (PCa) treatment adversely affects patients and places an unnecessary burden on our health care system. The inability to identify and grade clinically significant PCa lesions is a factor contributing to excessively aggressive PCa treatment, such as radical prostatectomy, instead of more focal, prostate-sparing procedures such as cryotherapy and high-dose radiation therapy. We have performed 3-D in vivo B-mode and acoustic radiation force impulse (ARFI) imaging using a mechanically rotated, side-fire endorectal imaging array to identify regions suspicious for PCa in 29 patients being treated with radical prostatectomies for biopsy-confirmed PCa. Whole-mount histopathology analyses were performed to identify regions of clinically significant/insignificant PCa lesions, atrophy and benign prostatic hyperplasia. Regions of suspicion for PCa were reader-identified in ARFI images based on boundary delineation, contrast, texture and location. These regions of suspicion were compared with histopathology identified lesions using a nearest-neighbor regional localization approach. Of all clinically significant lesions identified on histopathology, 71.4% were also identified using ARFI imaging, including 79.3% of posterior and 33.3% of anterior lesions. Among the ARFI-identified lesions, 79.3% corresponded to clinically significant PCa lesions, with these lesions having higher indices of suspicion than clinically insignificant PCa. ARFI imaging had greater sensitivity for posterior versus anterior lesions because of greater displacement signal-to-noise ratio and finer spatial sampling. Atrophy and benign prostatic hyperplasia can cause appreciable prostate anatomy distortion and heterogeneity that confounds ARFI PCa lesion identification; however, in general, ARFI regions of suspicion did not coincide with these benign pathologies. PMID:26947445

  7. Seismo-acoustic imaging of marine hard substrate habitats: a case study from the German Bight (SE North Sea)

    NASA Astrophysics Data System (ADS)

    Papenmeier, Svenja; Hass, H. Christian

    2016-04-01

    The detection of hard substrate habitats in sublittoral environments is a considerable challenge in spite of modern high resolution hydroacoustic techniques. In offshore areas those habitats are mainly represented by either cobbles and boulders (stones) often located in wide areas of soft sediments or by glacial relict sediments (heterogeneous mixture of medium sand to gravel size with cobbles and boulders). Sediment classification and object detection is commonly done on the basis of hydroacoustic backscatter intensities recorded with e.g. sidescan sonar (SSS) and multibeam echo sounder (MBES). Single objects lying on the sediment such as stones can generally be recognized by the acoustic shadow behind the object. However, objects close to the sonar's nadir may remain undetected because their shadows are below the data resolution. Further limitation in the detection of objects is caused by sessile communities that thrive on the objects. The bio-cover tends to absorb most of the acoustic signal. Automated identification based on the backscatter signal is often not satisfactory, especially when stones are present in a setting with glacial deposits. Areas characterized by glacial relict sediments are hardly differentiable in their backscatter characteristics from rippled coarse sand and fine gravel (rippled coarse sediments) without an intensive ground-truthing program. From the ecological point of view the relict and rippled coarse sediments are completely different habitats and need to be distinguished. The case study represents a seismo-acoustic approach in which SSS and nonlinear sediment echo sounder (SES) data are combined to enable a reliable and reproducible differentiation between relict sediments (with stones and coarse gravels) and rippled coarse sediments. Elevated objects produce hyperbola signatures at the sediment surface in the echo data which can be used to complement the SSS data. The nonlinear acoustic propagation of the SES sound pulses produces a

  8. Acoustic televiewer log images of natural fractures and bedding planes in the Toa Baja Borehole, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Paillet, Frederick L.; Goldberg, David

    Although borehole conditions made acoustic televiewer logging difficult in the Toa Baja borehole, more than 180 meters of continuous, acceptable quality televiewer logs were obtained in the intervals from 730 to 880 meters and from 2,515 to 2,675 meters in depth, indicating the presence of fractures that appear to be open in situ. Most of the largest, possibly open fractures in these intervals are either nearly parallel to directions given by the dipmeter log and may represent solution openings or minor washouts along bedding planes, or dip steeply to the south or southwest across bedding. The televiewer log confirms the presence of an apparently open set of fractures near 867 meters in depth, where circulation was lost during drilling, and in the interval from 2,600 to 2,650 meters in depth, where the temperature log indicates anomalous heat flow in the surrounding formation.

  9. Investigation of contact acoustic nonlinearity in delaminations by shearographic imaging, laser doppler vibrometric scanning and finite difference modeling.

    PubMed

    Sarens, Bart; Verstraeten, Bert; Glorieux, Christ; Kalogiannakis, Georgios; Van Hemelrijck, Danny

    2010-06-01

    Full-field dynamic shearography and laser Doppler vibrometric scanning are used to investigate the local contact acoustic nonlinear generation of delamination-induced effects on the vibration of a harmonically excited composite plate containing an artificial defect. Nonlinear elastic behavior caused by the stress-dependent boundary conditions at the delamination interfaces of a circular defect is also simulated by a 3-D second-order, finite-difference, staggered-grid model (displacement-stress formulation). Both the experimental and simulated data reveal an asymmetric motion of the layer above the delamination, which acts as a membrane vibrating with enhanced displacement amplitude around a finite offset displacement. The spectrum of the membrane motion is enriched with clapping-induced harmonics of the excitation frequency. In case of a sufficiently thin and soft membrane, the simulations reveal clear modal behavior at sub-harmonic frequencies caused by inelastic clapping. PMID:20529713

  10. Acoustic emission linear pulse holography

    DOEpatents

    Collins, H. Dale; Busse, Lawrence J.; Lemon, Douglas K.

    1985-01-01

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  11. Acoustic emission linear pulse holography

    SciTech Connect

    Collins, H. D.; Busse, L. J.; Lemon, D. K.

    1985-07-30

    Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

  12. Fracture-related wavefield polarization and seismic anisotropy across the Greendale Fault

    NASA Astrophysics Data System (ADS)

    Pischiutta, M.; Savage, M. K.; Holt, R. A.; Salvini, F.

    2015-10-01

    We investigate seismic signatures of fracturing in a newly ruptured strike-slip fault by determining the wavefield polarization in the New Zealand Canterbury Plains area and across the Greendale Fault, which was responsible for the 3 September 2010 Darfield Mw 7.1 earthquake. Previous studies suggested that fractured rocks in fault damage zones cause directional amplification and ground motion polarization in the fracture-perpendicular direction as an effect of stiffness anisotropy, and cause velocity anisotropy with shear wave velocity larger in the fracture-parallel component. An array of 14 stations was installed following the Darfield earthquake. We assess polarization both in the frequency and time domains through the individual-station horizontal-to-vertical spectral ratio and covariance matrix analysis, respectively, and compare the results to previously reported anisotropy measurements from shear wave splitting. Stations installed in the Canterbury Plains have an amplification peak between 0.1 and 0.3 Hz for both earthquakes and ambient noise. We relate the amplification to the resonance of a considerable thickness (c. 1 km) of soft sediments lying over the metamorphic bedrock. Analysis of seismic events revealed the existence of another peak in amplification between 2 and 5 Hz at two on-fault stations, which was not visible in the noise analysis. In contrast to the lower frequency peak, the ones between 2 and 5 Hz are more strongly anisotropic, attaining amplitudes up to a factor of 4 in the N52° direction. To interpret this effect we model the fracture pattern in the fault damage zone produced by the fault kinematics. We conclude that the horizontal polarization is orthogonal to extensional fractures, which predominate in the shallow layers (<2 km) with an expected strike of N139°. Fracture orientation is consistent with coseismic surface rupture observations, confirming the reliability of the model. S wave splitting is produced by velocity anisotropy

  13. Boundary element modeling of earthquake site effects including the complete incident wavefield

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Tae

    Numerical modeling of earthquake site effects in realistic, three-dimensional structures, including high frequencies, low surface velocities and surface topography, has not been possible simply because the amount of computer memory constrains the number of grid points available. In principle, this problem is reduced in the Boundary Element Method (BEM) since only the surface of the velocity discontinuity is discretized; wave propagation both inside and outside this boundary is computed analytically. Equivalent body forces are determined on the boundary by solving a matrix equation containing frequency-domain displacement and stress Green's functions from every point on the boundary to every other point. This matrix problem has imposed a practical limit on the size or maximum frequency of previous BEM models. Although the matrix can be quite large, it also seems to be fairly sparse. We have used iterative matrix algorithms of the PETSc package and direct solution algorithms of the ScaLAPACK on the massively parallel supercomputers at Cornell, San Diego and Michigan. Preconditioning has been applied using blockwise ILU decomposition for the iterative approach or LU decomposition for the direct approach. The matrix equation is solved using the GMRES method for the iterative approach and a tri-diagonal solver for the direct approach. Previous BEM applications typically have assumed a single, incident plane wave. However, it is clear that for more realistic ground motion simulations, we need to consider the complete incident wavefield. If we assume that the basin or three-dimensional structure of interest is embedded in a surrounding plane-layered medium, we may use the propagator matrix method to solve for the displacements and stresses at depth on the boundary. This is done in the frequency domain with integration over wavenumber so that all P, S, mode conversions, reverberations and surface waves are included. The Boundary Element Method succeeds in modeling

  14. Acoustic biosensors

    PubMed Central

    Fogel, Ronen; Seshia, Ashwin A.

    2016-01-01

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  15. Acoustic biosensors.

    PubMed

    Fogel, Ronen; Limson, Janice; Seshia, Ashwin A

    2016-06-30

    Resonant and acoustic wave devices have been researched for several decades for application in the gravimetric sensing of a variety of biological and chemical analytes. These devices operate by coupling the measurand (e.g. analyte adsorption) as a modulation in the physical properties of the acoustic wave (e.g. resonant frequency, acoustic velocity, dissipation) that can then be correlated with the amount of adsorbed analyte. These devices can also be miniaturized with advantages in terms of cost, size and scalability, as well as potential additional features including integration with microfluidics and electronics, scaled sensitivities associated with smaller dimensions and higher operational frequencies, the ability to multiplex detection across arrays of hundreds of devices embedded in a single chip, increased throughput and the ability to interrogate a wider range of modes including within the same device. Additionally, device fabrication is often compatible with semiconductor volume batch manufacturing techniques enabling cost scalability and a high degree of precision and reproducibility in the manufacturing process. Integration with microfluidics handling also enables suitable sample pre-processing/separation/purification/amplification steps that could improve selectivity and the overall signal-to-noise ratio. Three device types are reviewed here: (i) bulk acoustic wave sensors, (ii) surface acoustic wave sensors, and (iii) micro/nano-electromechanical system (MEMS/NEMS) sensors. PMID:27365040

  16. Acoustic backscattering enhancements for circular elastic plates and acrylic targets, the application of acoustic holography to the study of scattering from planar elastic objects, and other research on the radiation of sound

    NASA Astrophysics Data System (ADS)

    Hefner, Brian Todd

    2000-08-01

    Backscattering enhancements on both circular elastic plates and acrylic targets are investigated as well as several techniques for the study of the radiation of sound. For sound scattered from a circular plate, two backscattering enhancements associated with the extensional wave are observed. The first of these enhancements involves extensional wave excitation along the diameter of the plate. When the extensional wave strikes the plate edge, reflection occurs which produces radiation into the backscattering direction. For those portions of the leaky wave which strike the edge at oblique incidence, there is mode conversion into a trapped shear wave. For certain angles of incidence on the plate edge, this wave can undergo multiple reflections and convert back into a leaky wave directed in the backscattering direction. Each of these enhancements are modeled using quantitative ray methods. Acoustic holography is also used to image the surface motion of the plate to identify the causes of these enhancements and to assess the validity of the ray model. Backscattering enhancements associated with antisymmetric Lamb wave excitation are also investigated. Scattering at the first-order antisymmetric wave coupling angle is studied using acoustic holography. Significant mode- conversion between the zeroth and first-order antisymmetric waves is observed which plays a significant role in the scattering processes. Quantitative ray models were also used to examine the backscattering from acrylic targets. Polymer solids typically have shear and Rayleigh wave phase velocities which are less than the speed of sound in water. For solid acrylic spheres, low frequency resonances are observed both experimentally and in the exact backscattering form functions which are due to coupling between the incident field and the subsonic Rayleigh wave on the sphere. The effects of material absorption, which is generally high in polymers, is examined in both the exact solutions and the quantitative

  17. Acoustic lens-based swimmer's sonar

    NASA Astrophysics Data System (ADS)

    Linnenbrink, Thomas E.; Desilets, Charles S.; Folds, Donald L.; Quick, Marshall K.

    1999-07-01

    A new high resolution imaging sonar is begin developed for use by swimmers to identify objects in turbid water or under low light level conditions. Beam forming for both the transmit and receive functions is performed with acoustic lenses. The acoustic image is focused on an acoustic retina or focal pane. An acoustic video converter converts the acoustic image to an electronic from suitable for display with conventional electronics. The image will be presented to the swimmer as a heads-up display on the face of his or her mask. The system will provide 1 cm resolution in range and cross range from 1-5 meters from the object. A longer range search mode is being explored. Laboratory prototypes of key components have been fabricated and evaluated. Results to date are promising.

  18. A Preliminary Engineering Design of Intravascular Dual-Frequency Transducers for Contrast-Enhanced Acoustic Angiography and Molecular Imaging

    PubMed Central

    Ma, Jianguo; Martin, K. Heath; Dayton, Paul A.; Jiang, Xiaoning

    2014-01-01

    Current intravascular ultrasound (IVUS) probes are not optimized for contrast detection because of their design for high-frequency fundamental-mode imaging. However, data from transcutaneous contrast imaging suggests the possibility of utilizing contrast ultrasound for molecular imaging or vasa vasorum assessment to further elucidate atherosclerotic plaque deposition. This paper presents the design, fabrication, and characterization of a small-aperture (0.6 × 3 mm) IVUS probe optimized for high-frequency contrast imaging. The design utilizes a dual-frequency (6.5 MHz/30 MHz) transducer arrangement for exciting microbubbles at low frequencies (near their resonance) and detecting their broadband harmonics at high frequencies, minimizing detected tissue backscatter. The prototype probe is able to generate nonlinear microbubble response with more than 1.2 MPa of rarefractional pressure (mechanical index: 0.48) at 6.5 MHz, and is also able to detect microbubble response with a broadband receiving element (center frequency: 30 MHz, −6-dB fractional bandwidth: 58.6%). Nonlinear super-harmonics from microbubbles flowing through a 200-μm-diameter micro-tube were clearly detected with a signal-to-noise ratio higher than 12 dB. Preliminary phantom imaging at the fundamental frequency (30 MHz) and dual-frequency super-harmonic imaging results suggest the promise of small aperture, dual-frequency IVUS transducers for contrast-enhanced IVUS imaging. PMID:24801226

  19. Extending RTM Imaging With a Focus on Head Waves

    NASA Astrophysics Data System (ADS)

    Holicki, Max; Drijkoningen, Guy

    2016-04-01

    Conventional industry seismic imaging predominantly focuses on pre-critical reflections, muting post-critical arrivals in the process. This standard approach neglects a lot of information present in the recorded wave field. This negligence has been partially remedied with the inclusion of head waves in more advanced imaging techniques, like Full Waveform Inversion (FWI). We would like to see post-critical information leave the realm of labour-intensive travel-time picking and tomographic inversion towards full migration to improve subsurface imaging and parameter estimation. We present a novel seismic imaging approach aimed at exploiting post-critical information, using the constant travel path for head-waves between shots. To this end, we propose to generalize conventional Reverse Time Migration (RTM) to scenarios where the sources for the forward and backward propagated wave-fields are not coinciding. RTM functions on the principle that backward propagated receiver data, due to a source at some locations, must overlap with the forward propagated source wave field, from the same source location, at subsurface scatterers. Where the wave-fields overlap in the subsurface there is a peak at the zero-lag cross-correlation, and this peak is used for the imaging. For the inclusion of head waves, we propose to relax the condition of coincident sources. This means that wave-fields, from non-coincident-sources, will not overlap properly in the subsurface anymore. We can make the wave-fields overlap in the subsurface again, by time shifting either the forward or backward propagated wave-fields until the wave-fields overlap. This is the same as imaging at non-zero cross-correlation lags, where the lag is the travel time difference between the two wave-fields for a given event. This allows us to steer which arrivals we would like to use for imaging. In the simplest case we could use Eikonal travel-times to generate our migration image, or we exclusively image the subsurface

  20. Small-Scale Trial for Evaluating Directional Resolution of Single Spherical Biconcave Acoustic Lens in Designing of Ambient Noise Imaging System

    NASA Astrophysics Data System (ADS)

    Mori, Kazuyoshi; Ogasawara, Hanako; Nakamura, Toshiaki

    2008-05-01

    Ambient noise imaging (ANI) is the revolutionary idea of detecting objects by using natural ocean background noise. From the analysis results obtained by the finite difference time domain (FDTD) method in our previous studies, it was supposed that a spherical biconcave lens with an aperture diameter of 2.0 m has a sufficient directional resolution (for example, the beam width is 1° at 60 kHz) for realizing an ANI system. In this study, to confirm the analysis results, we performed a small-scale trial of one-fifth space in a water tank. The lens, made of acrylic resin, has an aperture diameter of 400 mm and a radius of curvature of 500 mm. A burst pulse of 25 cycles at 300 kHz, whose frequency increases 5 times, was radiated from the sound source. The sound pressure after passage through the acoustic lens was measured by moving the receiver around the image point. Results show that the shapes of -3 dB areas are similar to the FDTD analysis results at small incidence angles. It was verified that this lens has a sufficient directional resolution for use in the ANI system, because -3 dB areas do not overlap each other.

  1. Optimization of contrast-to-tissue ratio through pulse windowing in dual-frequency “acoustic angiography” imaging

    PubMed Central

    Lindsey, Brooks D.; Shelton, Sarah E.; Dayton, Paul A.

    2016-01-01

    Early-stage tumors in many cancers are characterized by vascular remodeling, indicative of transformations in cell function. We have previously presented a high-resolution ultrasound imaging approach for detecting these changes which is based on microbubble contrast agents. In this technique, images are formed from only the higher harmonics of microbubble contrast agents, producing images of vasculature alone with 100–200 μm resolution. In this article, shaped transmit pulses are applied to imaging the higher broadband harmonic echoes of microbubble contrast agents, and the effects of varying pulse window and phasing on microbubble and tissue harmonic echoes are evaluated using a dual-frequency transducer in vitro and in vivo. An increase in contrast-to-tissue ratio of 6.8 ± 2.3 dB was observed in vitro by using an inverted pulse with a cosine window relative to a non-inverted pulse with a rectangular window. The increase in mean image intensity due to contrast enhancement in vivo in five rodents was 13.9 ± 3.0 dB greater for an inverted cosine-windowed pulse and 17.8 ± 3.6 dB greater for a non-inverted Gaussian-windowed relative to a non-inverted pulse with a rectangular window. Implications for pre-clinical and diagnostic imaging are also discussed. PMID:25819467

  2. Controlling sound with acoustic metamaterials

    NASA Astrophysics Data System (ADS)

    Cummer, Steven A.; Christensen, Johan; Alù, Andrea

    2016-03-01

    Acoustic metamaterials can manipulate and control sound waves in ways that are not possible in conventional materials. Metamaterials with zero, or even negative, refractive index for sound offer new possibilities for acoustic imaging and for the control of sound at subwavelength scales. The combination of transformation acoustics theory and highly anisotropic acoustic metamaterials enables precise control over the deformation of sound fields, which can be used, for example, to hide or cloak objects from incident acoustic energy. Active acoustic metamaterials use external control to create effective material properties that are not possible with passive structures and have led to the development of dynamically reconfigurable, loss-compensating and parity-time-symmetric materials for sound manipulation. Challenges remain, including the development of efficient techniques for fabricating large-scale metamaterial structures and converting laboratory experiments into useful devices. In this Review, we outline the designs and properties of materials with unusual acoustic parameters (for example, negative refractive index), discuss examples of extreme manipulation of sound and, finally, provide an overview of future directions in the field.

  3. Acoustic Inversion in Optoacoustic Tomography: A Review

    PubMed Central

    Rosenthal, Amir; Ntziachristos, Vasilis; Razansky, Daniel

    2013-01-01

    Optoacoustic tomography enables volumetric imaging with optical contrast in biological tissue at depths beyond the optical mean free path by the use of optical excitation and acoustic detection. The hybrid nature of optoacoustic tomography gives rise to two distinct inverse problems: The optical inverse problem, related to the propagation of the excitation light in tissue, and the acoustic inverse problem, which deals with the propagation and detection of the generated acoustic waves. Since the two inverse problems have different physical underpinnings and are governed by different types of equations, they are often treated independently as unrelated problems. From an imaging standpoint, the acoustic inverse problem relates to forming an image from the measured acoustic data, whereas the optical inverse problem relates to quantifying the formed image. This review focuses on the acoustic aspects of optoacoustic tomography, specifically acoustic reconstruction algorithms and imaging-system practicalities. As these two aspects are intimately linked, and no silver bullet exists in the path towards high-performance imaging, we adopt a holistic approach in our review and discuss the many links between the two aspects. Four classes of reconstruction algorithms are reviewed: time-domain (so called back-projection) formulae, frequency-domain formulae, time-reversal algorithms, and model-based algorithms. These algorithms are discussed in the context of the various acoustic detectors and detection surfaces which are commonly used in experimental studies. We further discuss the effects of non-ideal imaging scenarios on the quality of reconstruction and review methods that can mitigate these effects. Namely, we consider the cases of finite detector aperture, limited-view tomography, spatial under-sampling of the acoustic signals, and acoustic heterogeneities and losses. PMID:24772060

  4. Acoustic Characterization of Mesoscale Objects

    SciTech Connect

    Chinn, D; Huber, R; Chambers, D; Cole, G; Balogun, O; Spicer, J; Murray, T

    2007-03-13

    This report describes the science and engineering performed to provide state-of-the-art acoustic capabilities for nondestructively characterizing mesoscale (millimeter-sized) objects--allowing micrometer resolution over the objects entire volume. Materials and structures used in mesoscale objects necessitate the use of (1) GHz acoustic frequencies and (2) non-contacting laser generation and detection of acoustic waves. This effort demonstrated that acoustic methods at gigahertz frequencies have the necessary penetration depth and spatial resolution to effectively detect density discontinuities, gaps, and delaminations. A prototype laser-based ultrasonic system was designed and built. The system uses a micro-chip laser for excitation of broadband ultrasonic waves with frequency components reaching 1.0 GHz, and a path-stabilized Michelson interferometer for detection. The proof-of-concept for mesoscale characterization is demonstrated by imaging a micro-fabricated etched pattern in a 70 {micro}m thick silicon wafer.

  5. Towards Simulating a Realistic Planetary Seismic Wavefield: The Contribution of the Megaregolith and Low-Velocity Waveguides

    NASA Technical Reports Server (NTRS)

    Schmerr, Nicholas C.; Weber, Renee C.; Lin, Pei-Ying Patty; Thorne, Michael Scott; Garnero, Ed J.

    2011-01-01

    Lunar seismograms are distinctly different from their terrestrial counterparts. The Apollo lunar seismometers recorded moonquakes without distinct P- or S-wave arrivals; instead waves arrive as a diffuse coda that decays over several hours making the identification of body waves difficult. The unusual character of the lunar seismic wavefield is generally tied to properties of the megaregolith: it consists of highly fractured and broken crustal rock, the result of extensive bombardment of the Moon. The megaregolith extends several kilometers into the lunar crust, possibly into the mantle in some regions, and is covered by a thin coating of fine-scale dust. These materials possess very low seismic velocities that strongly scatter the seismic wavefield at high frequencies. Directly modeling the effects of the megaregolith to simulate an accurate lunar seismic wavefield is a challenging computational problem, owing to the inherent 3-D nature of the problem and the high frequencies (greater than 1 Hz) required. Here we focus on modeling the long duration code, studying the effects of the low velocities found in the megaregolith. We produce synthetic seismograms using 1-D slowness integration methodologies, GEMINI and reflectivity, and a 3-D Cartesian finite difference code, Wave Propagation Program, to study the effect of thin layers of low velocity on the surface of a planet. These codes allow us generate seismograms with dominant frequencies of approximately 1 Hz. For background lunar seismic structure we explore several models, including the recent model of Weber et al., Science, 2011. We also investigate variations in megaregolithic thickness, velocity, attenuation, and seismogram frequency content. Our results are compared to the Apollo seismic dataset, using both a cross correlation technique and integrated envelope approach to investigate coda decay. We find our new high frequency results strongly support the hypothesis that the long duration of the lunar seismic

  6. Progress in acoustic holography

    NASA Astrophysics Data System (ADS)

    Hildebrand, B. P.

    1985-01-01

    The theory underlying the methods used in acoustic holography (the real-time liquid surface levitation and the scanning holography methods) and in electromagnetic holography, which uses electromagnetic impulses (radar) or electromagnetic waves (eddy current) is developed. These holographic techniques are illustrated with experimental results, including the use of the liquid surface levitation method for inspecting fiberglass laminate tubes, and examples of the time-of-flight holographic images, the coherent ultrasonic images, multifrequency ultrasonic images, and the synthetic aperture holography images obtained by the use of the scanning holography methodology. Other examples illustrate applications of radar holography and eddy current holography. These examples are used to refute some traditional negative comments on nonoptical holography.

  7. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, Butrus T.; Chou, Ching H.

    1990-01-01

    A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

  8. Acoustic transducer for acoustic microscopy

    DOEpatents

    Khuri-Yakub, B.T.; Chou, C.H.

    1990-03-20

    A shear acoustic transducer-lens system is described in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens. 9 figs.

  9. Real-time prediction of seismic ground motion (I) : real-time estimation of seismic wavefield using data assimilation technique and time evolutional prediction using Kirchhoff integral

    NASA Astrophysics Data System (ADS)

    Hoshiba, M.

    2013-05-01

    In this presentation, I propose a new approach for real-time prediction of seismic ground motion which is applicable to Earthquake Early Waning (EEW), in which hypocentral location and magnitude are not required. . Many methods of EEW are based on a network method in which hypocenter and magnitude (source parameters) are quickly determined, and then the ground motions are predicted, and warnings are issued depending on the strength of the predicted ground motion. In this method, it is necessary to determine the hypocenter and magnitude at first, and error of the source parameters leads directly to the error of the prediction. It is not easy to take the effects of rupture directivity and source extent into account, and it is impossible to fully reproduce the current wavefield from the interpreted source parameters. Time evolutional prediction is a method in which future wavefield is iteratively predicted from the wavefield at the certain time, that is u(x, t+Δt)=P(u(x, t)), where u is the wave motion at location x at lapse time t, and P is the prediction operator. Future wave motion, u(x, t+Δt), is predicted from the distribution of the current wave motion u(x, t) using P. For P, finite difference technique or boundary integral equation method, such as Kirchhoff integral, is used. Kirchhoff integral is qualitatively approximated by Huygens principle. The real time monitoring of wavefield are important for this method, but it is possible to predict ground motion without a hypocentral location and magnitude. In the time evolutional prediction, determination of detailed distribution of current wavefield is an important key, so that dense seismic observation network is required. Data assimilation is a technique to produce artificially denser network, which is widely used for numerical weather forecast and oceanography. Distribution of current wave motion is estimated from not only the current real observation of u(xi, t) where xi is the location of the i-th site, but

  10. Data analysis results of the second sea trial of ambient noise imaging with acoustic lens in 2014: Two-dimensional target images affected by direction of field of view and spatial noise distribution

    NASA Astrophysics Data System (ADS)

    Mori, Kazuyoshi; Ogasawara, Hanako; Tsuchiya, Takenobu; Endoh, Nobuyuki

    2016-07-01

    An aspherical lens with an aperture diameter of 1.0 m has been designed and fabricated to develop a prototype system for ambient noise imaging (ANI). A sea trial of silent target detection using the prototype ANI system was conducted under only natural ocean ambient noise at Uchiura Bay in November 2010. It was verified that targets are successfully detected under natural ocean ambient noise, mainly generated by snapping shrimps. Recently, we have built a second prototype ANI system using an acoustic lens with a two-dimensional (2D) receiver array with 127 elements corresponding to a field of view (FOV) spanning 15° horizontally by 9° vertically. In this study, we investigated the effects of the direction of the FOV and the spatial noise distribution on the 2D target image obtained by ANI. Here, the noise sources in front of the target are called “front light”, and those at the rear of the target are called “back light”. The second sea trial was conducted to image targets arranged in the FOV and measure the positions of noise sources at Uchiura Bay in November 10–14, 2014. For front light, the pixel values in the on-target directions were greater than those in other directions owing to the dominant target scatterings. Reversely, for back light, the pixel values in the on-target directions were lower than those in other directions owing to the dominant direct noises such as “silhouette”.

  11. Evaluation of damage accumulation behavior and strength anisotropy of NITE SiC/SiC composites by acoustic emission, digital image correlation and electrical resistivity monitoring

    NASA Astrophysics Data System (ADS)

    Nozawa, Takashi; Ozawa, Kazumi; Asakura, Yuuki; Kohyama, Akira; Tanigawa, Hiroyasu

    2014-12-01

    Understanding the cracking process of the composites is essential to establish the design basis for practical applications. This study aims to investigate the damage accumulation process and its anisotropy for nano-infiltration transient eutectic sintered (NITE) SiC/SiC composites by various characterization techniques such as the acoustic emission (AE), digital image correlation (DIC) and electrical resistivity (ER) measurements. Cracking behavior below the proportional limit stress (PLS) was specifically addressed. Similar to the other generic SiC/SiC composites, the 1st AE event was identified below the PLS for NITE SiC/SiC composites with a dependency of fabric orientation. The DIC results support that the primary failure mode depending on fiber orientation affected more than the other minor modes did. Detailed AE waveform analysis by wavelet shows a potential to classify the failure behavior depending on architecture. Cracking below the PLS is a potential concern in component deign but the preliminary ER measurements imply that the impact of cracking below the PLS on composite function was limited.

  12. Imaging sciences workshop

    SciTech Connect

    Candy, J.V.

    1994-11-15

    This workshop on the Imaging Sciences sponsored by Lawrence Livermore National Laboratory contains short abstracts/articles submitted by speakers. The topic areas covered include the following: Astronomical Imaging; biomedical imaging; vision/image display; imaging hardware; imaging software; Acoustic/oceanic imaging; microwave/acoustic imaging; computed tomography; physical imaging; imaging algorithms. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.

  13. Modification of Kirchhoff migration with variable sound speed and attenuation for acoustic imaging of media and application to tomographic imaging of the breast

    PubMed Central

    Schmidt, Steven; Duric, Nebojsa; Li, Cuiping; Roy, Olivier; Huang, Zhi-Feng

    2011-01-01

    Purpose: To explore the feasibility of improving cross-sectional reflection imaging of the breast using refractive and attenuation corrections derived from ultrasound tomography data. Methods: The authors have adapted the planar Kirchhoff migration method, commonly used in geophysics to reconstruct reflection images, for use in ultrasound tomography imaging of the breast. Furthermore, the authors extended this method to allow for refractive and attenuative corrections. Using clinical data obtained with a breast imaging prototype, the authors applied this method to generate cross-sectional reflection