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Sample records for acoustic imaging applied

  1. Symmetry analysis for nonlinear time reversal methods applied to nonlinear acoustic imaging

    NASA Astrophysics Data System (ADS)

    Dos Santos, Serge; Chaline, Jennifer

    2015-10-01

    Using symmetry invariance, nonlinear Time Reversal (TR) and reciprocity properties, the classical NEWS methods are supplemented and improved by new excitations having the intrinsic property of enlarging frequency analysis bandwidth and time domain scales, with now both medical acoustics and electromagnetic applications. The analysis of invariant quantities is a well-known tool which is often used in nonlinear acoustics in order to simplify complex equations. Based on a fundamental physical principle known as symmetry analysis, this approach consists in finding judicious variables, intrinsically scale dependant, and able to describe all stages of behaviour on the same theoretical foundation. Based on previously published results within the nonlinear acoustic areas, some practical implementation will be proposed as a new way to define TR-NEWS based methods applied to NDT and medical bubble based non-destructive imaging. This paper tends to show how symmetry analysis can help us to define new methodologies and new experimental set-up involving modern signal processing tools. Some example of practical realizations will be proposed in the context of biomedical non-destructive imaging using Ultrasound Contrast Agents (ACUs) where symmetry and invariance properties allow us to define a microscopic scale-invariant experimental set-up describing intrinsic symmetries of the microscopic complex system.

  2. 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

  3. Image processing techniques for acoustic images

    NASA Astrophysics Data System (ADS)

    Murphy, Brian P.

    1991-06-01

    The primary goal of this research is to test the effectiveness of various image processing techniques applied to acoustic images generated in MATLAB. The simulated acoustic images have the same characteristics as those generated by a computer model of a high resolution imaging sonar. Edge detection and segmentation are the two image processing techniques discussed in this study. The two methods tested are a modified version of the Kalman filtering and median filtering.

  4. Eigenspace based minimum variance beamforming applied to ultrasound imaging of acoustically hard tissues.

    PubMed

    Mehdizadeh, Saeed; Austeng, Andreas; Johansen, Tonni F; Holm, Sverre

    2012-10-01

    Minimum variance (MV) based beamforming techniques have been successfully applied to medical ultrasound imaging. These adaptive methods offer higher lateral resolution, lower sidelobes, and better definition of edges compared to delay and sum beamforming (DAS). In standard medical ultrasound, the bone surface is often visualized poorly, and the boundaries region appears unclear. This may happen due to fundamental limitations of the DAS beamformer, and different artifacts due to, e.g., specular reflection, and shadowing. The latter can degrade the robustness of the MV beamformers as the statistics across the imaging aperture is violated because of the obstruction of the imaging beams. In this study, we employ forward/backward averaging to improve the robustness of the MV beamforming techniques. Further, we use an eigen-spaced minimum variance technique (ESMV) to enhance the edge detection of hard tissues. In simulation, in vitro, and in vivo studies, we show that performance of the ESMV beamformer depends on estimation of the signal subspace rank. The lower ranks of the signal subspace can enhance edges and reduce noise in ultrasound images but the speckle pattern can be distorted.

  5. Random matrix theory applied to acoustic backscattering and imaging in complex media.

    PubMed

    Aubry, Alexandre; Derode, Arnaud

    2009-02-27

    The singular values distribution of the propagation operator in a random medium is investigated in a backscattering configuration. Experiments are carried out with pulsed ultrasonic waves around 3 MHz, using an array of transducers. Coherent backscattering and field correlations are taken into account. Interestingly, the distribution of singular values shows a dramatically different behavior in the single and multiple-scattering regimes. Based on a matrix separation of single and multiple-scattered waves, an experimental illustration of imaging through a highly scattering slab is presented.

  6. 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.

  7. Electromagnetic acoustic imaging.

    PubMed

    Emerson, Jane F; Chang, David B; McNaughton, Stuart; Jeong, Jong Seob; Shung, K K; Cerwin, Stephen A

    2013-02-01

    Electromagnetic acoustic imaging (EMAI) is a new imaging technique that uses long-wavelength RF electromagnetic (EM) waves to induce ultrasound emission. Signal intensity and image contrast have been found to depend on spatially varying electrical conductivity of the medium in addition to conventional acoustic properties. The resultant conductivity- weighted ultrasound data may enhance the diagnostic performance of medical ultrasound in cancer and cardiovascular applications because of the known changes in conductivity of malignancy and blood-filled spaces. EMAI has a potential advantage over other related imaging techniques because it combines the high resolution associated with ultrasound detection with the generation of the ultrasound signals directly related to physiologically important electrical properties of the tissues. Here, we report the theoretical development of EMAI, implementation of a dual-mode EMAI/ultrasound apparatus, and successful demonstrations of EMAI in various phantoms designed to establish feasibility of the approach for eventual medical applications.

  8. Acoustic Daylight Imaging

    DTIC Science & Technology

    1999-09-30

    response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and...information to improve image quality. Many different types of targets have also been deployed from ORB at ranges up to 80 m, although most data were...correlation with the acoustic data . Data are recorded continually onto a large hard drive and later transcribed to CD ROM for permanent storage. WORK

  9. Nondestructive Acoustic Imaging Techniques

    NASA Astrophysics Data System (ADS)

    Schmitz, Volker

    Acoustic imaging techniques are used in the field of nondestructive testing of technical components to measure defects such as lack of side wall fusion or cracks in welded joints. Data acquisition is performed by a remote-controlled manipulator and a PC for the mass storage of the high-frequency time-of-flight data at each probe position. The quality of the acoustic images and the interpretation relies on the proper understanding of the transmitted wave fronts and the arrangement of the probes in pulse-echo mode or in pitch-and-catch arrangement. The use of the Synthetic Aperture Focusing Technique allows the depth-dependent resolution to be replaced by a depth-independent resolution and the signal-to-noise ratio to be improved. Examples with surface-connected cracks are shown to demonstrate the improved features. The localization accuracy could be improved by entering 2-dimensional or 3-dimensional reconstructed data into the environment of a 3-dimensional CAD drawing. The propagation of ultrasonic waves through austenitic welds is disturbed by the anisotropic and inhomogeneous structure of the material. The effect is more or less severe depending upon the longitudinal or shear wave modes. To optimize the performance of an inspection software tool, a 3-dimensional CAD-Ray program has been implemented, where the shape of the inhomogeneous part of a weld can be simulated together with the grain structure based on the elastic constants. Ray-tracing results are depicted for embedded and for surface-connected defects.

  10. 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.

  11. Magnetic resonance acoustic radiation force imaging.

    PubMed

    McDannold, Nathan; Maier, Stephan E

    2008-08-01

    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.

  12. Acoustic imaging system

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Jr.

    1977-01-01

    Tool detects noise sources by scanning sound "scene" and displaying relative location of noise-producing elements in area. System consists of ellipsoidal acoustic mirror and microphone and a display device.

  13. Student design projects in applied acoustics.

    PubMed

    Bös, Joachim; Moritz, Karsten; Skowronek, Adam; Thyes, Christian; Tschesche, Johannes; Hanselka, Holger

    2012-03-01

    This paper describes a series of student projects which are intended to complement theoretical education in acoustics and engineering noise control with practical experience. The projects are also intended to enhance the students' ability to work in a team, to manage a project, and to present their results. The projects are carried out in close cooperation with industrial partners so that the students can get a taste of the professional life of noise control engineers. The organization of such a project, its execution, and some of the results from the most recent student project are presented as a demonstrative example. This latest project involved the creation of noise maps of a production hall, the acoustic analysis of a packaging machine, and the acoustic analysis of a spiral vibratory conveyor. Upon completion of the analysis, students then designed, applied, and verified some simple preliminary noise reduction measures to demonstrate the potential of these techniques.

  14. 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.

  15. 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

  16. Acoustic waves in medical imaging and diagnostics.

    PubMed

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

    2013-07-01

    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. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the 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 is presented. We discuss the potential for future shear wave imaging applications. Copyright © 2013 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  17. 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.

  18. Acoustic Daylight Imaging

    DTIC Science & Technology

    1998-09-30

    information to improve image quality. Many different types of targets have also been deployed from ORB at ranges up to 80 m, although most data were...estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the... data needed, and completing and reviewing the collection of information Send comments regarding this burden estimate or any other aspect of this

  19. Acoustic imaging of objects buried in soil.

    PubMed

    Frazier, C H; Cadalli, N; Munson, D C; O'Brien, W D

    2000-07-01

    In this study, we demonstrate an acoustic system for high-resolution imaging of objects buried in soil. Our goal is to image cultural artifacts in order to assess in a rapid manner the historical significance of a potential construction site. We describe the imaging system and present preliminary images produced from data collected from a soil phantom. A mathematical model and associated computer software are developed in order to simulate the signals acquired by the system. We have built the imaging system, which incorporates a single element source transducer and a receiver array. The source and receiver array are moved together along a linear path to collect data. Using this system, we have obtained B-mode images of several targets by using delay-and-sum beamforming, and we have also applied synthetic aperture theory to this problem.

  20. Transformational Acoustics Applied to Scattering from a Thin Elastic Shell

    DTIC Science & Technology

    2011-06-01

    invariant form.” New Journal of Physics, 8 (248), 2006. [6] H. Chen and C. T. Chan. “ Acoustic cloaking in three dimensions using acoustic metamaterials ...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS TRANSFORMATIONAL ACOUSTICS APPLIED TO SCATTERING FROM A THIN ELASTIC SHELL by Ana Margarida R...Prescribed by ANSI Std. Z39.18 22–6–2011 Master’s Thesis 2102-06-01—2104-10-31 Transformational Acoustics Applied to Scattering From a Thin Elastic

  1. 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.

  2. 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.

  3. 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.

  4. Acoustic Imaging of Combustion Noise

    NASA Technical Reports Server (NTRS)

    Ramohalli, K. N.; Seshan, P. K.

    1984-01-01

    Elliposidal acoustic mirror used to measure sound emitted at discrete points in burning turbulent jets. Mirror deemphasizes sources close to target source and excludes sources far from target. At acoustic frequency of 20 kHz, mirror resolves sound from region 1.25 cm wide. Currently used by NASA for research on jet flames. Produces clearly identifiable and measurable variation of acoustic spectral intensities along length of flame. Utilized in variety of monitoring or control systems involving flames or other reacting flows.

  5. The feedback phenomenon applied to underwater acoustics

    NASA Astrophysics Data System (ADS)

    Roux, Philippe; Jordan, Jason E.; Kuperman, W. A.

    2002-11-01

    People are familiar with the feedback phenomenon that results in the loud sound heard when a musician plays an electric instrument directly into a speaker. Feedback occurs when a source and a receiver are connected both acoustically through the propagation medium and electrically through an amplifier in such way that the received signal is simultaneously and continuously added to the emitted signal. A resonance is then obtained when the emitter and the receiver are in phase. The resonant frequency appears to be highly sensitive to fluctuations of the propagation medium. The feedback phenomenon has been experimentally demonstrated as a means to monitor the temperature fluctuation of a shallow water environment [''Acoustic monitoring of the sea medium variability: experimental testing of new methods,'' by A. V. Furduev, Acoust. Phys. 47, No. 3, 361-368 (2001)]. The goal of our work is to reproduce the feedback experiment using an alternative method that decomposes the feedback phenomenon into an iterative process. Successful reproduction of the feedback is accomplished using a step-by-step algorithm which details the evolution of the system from the initial signal to its steady-state form. These experimental and numerical results illustrate the potential of the feedback process for use in narrow-band acoustical tomography.

  6. Acoustic noise during functional magnetic resonance imaging.

    PubMed

    Ravicz, M E; Melcher, J R; Kiang, N Y

    2000-10-01

    Functional magnetic resonance imaging (fMRI) enables sites of brain activation to be localized in human subjects. For studies of the auditory system, acoustic noise generated during fMRI can interfere with assessments of this activation by introducing uncontrolled extraneous sounds. As a first step toward reducing the noise during fMRI, this paper describes the temporal and spectral characteristics of the noise present under typical fMRI study conditions for two imagers with different static magnetic field strengths. Peak noise levels were 123 and 138 dB re 20 microPa in a 1.5-tesla (T) and a 3-T imager, respectively. The noise spectrum (calculated over a 10-ms window coinciding with the highest-amplitude noise) showed a prominent maximum at 1 kHz for the 1.5-T imager (115 dB SPL) and at 1.4 kHz for the 3-T imager (131 dB SPL). The frequency content and timing of the most intense noise components indicated that the noise was primarily attributable to the readout gradients in the imaging pulse sequence. The noise persisted above background levels for 300-500 ms after gradient activity ceased, indicating that resonating structures in the imager or noise reverberating in the imager room were also factors. The gradient noise waveform was highly repeatable. In addition, the coolant pump for the imager's permanent magnet and the room air-handling system were sources of ongoing noise lower in both level and frequency than gradient coil noise. Knowledge of the sources and characteristics of the noise enabled the examination of general approaches to noise control that could be applied to reduce the unwanted noise during fMRI sessions.

  7. Synthetic modelling of acoustical propagation applied to seismic oceanography experiments

    NASA Astrophysics Data System (ADS)

    Kormann, Jean; Cobo, Pedro; Biescas, Berta; Sallarés, Valentí; Papenberg, Cord; Recuero, Manuel; Carbonell, Ramón

    2010-03-01

    Recent work shows that multichannel seismic (MCS) systems provide detailed information on the oceans' finestructure. The aim of this paper is to analyze if high order numerical algorithms are suitable to accurately model the extremely weak wavefield scattered by the oceans' finestructures. For this purpose, we generate synthetic shot records along a coincident seismic and oceanographic profile acquired across a Mediterranean salt lens in the Gulf of Cadiz. We apply a 2D finite-difference time-domain propagation model, together with second-order Complex Frequency Shifted Perfectly Matched Layers at the numerical boundaries, using as reference a realistic sound speed map with the lateral resolution of the seismic data. We show that our numerical propagator creates an acoustical image of the ocean finestructures including the salt lens that reproduces with outstanding detail the real acquired one.

  8. 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").

  9. Optical and opto-acoustic interventional imaging.

    PubMed

    Sarantopoulos, Athanasios; Beziere, Nicolas; Ntziachristos, Vasilis

    2012-02-01

    Many clinical interventional procedures, such as surgery or endoscopy, are today still guided by human vision and perception. Human vision however is not sensitive or accurate in detecting a large range of disease biomarkers, for example cellular or molecular processes characteristic of disease. For this reason advanced optical and opto-acoustic (photo-acoustic) methods are considered for enabling a more versatile, sensitive and accurate detection of disease biomarkers and complement human vision in clinical decision making during interventions. Herein, we outline developments in emerging fluorescence and opto-acoustic sensing and imaging techniques that can lead to practical implementations toward improving interventional vision.

  10. Acoustical bubble trapper applied to hemodialysis.

    PubMed

    Palanchon, P; Birmelé, B; Tranquart, F

    2008-04-01

    Gaseous microemboli can arise in extracorporeal lines and devices such as dialysis machines. They are associated with severe pulmonary side effects in patients undergoing chronic hemodialysis sessions. The goal of this study was to develop a gaseous emboli trapper using ultrasound waves to remove any air bubble from the tubing system before they reach the patient. A homemade bubble trapper, developed in the laboratory, consists of a Perspex block containing a main channel connected to the tubing of a hemodialysis machine and a second subchannel positioned perpendicularly to the main one, used to trap the air microemboli. The microemboli flowing in the main channel were insonified through an acoustic window with an ultrasound wave, at a frequency of 500 kHz and with a maximal acoustic pressure of 500 kPa, generated by a single-element transducer positioned 3 cm away from the main flow. The radiation force induced by the ultrasound beam acts directly on the flowing air emboli, by pushing them into the subchannel. Two Doppler probes operating both at 2 MHz, connected to a DWL Doppler machine were placed before and after the bubble trapper to count sequentially the number of embolic events. The flow of the machine was varied between 200 mL/min and 500 mL/min. Depending on the flow velocity, the number of microembolic signals (MES) detected by the Doppler probes before and after the trapping system was identical and ranged from 5 to 150 MES/min in absence of the ultrasound irradiation. When the air bubble trapper was activated, a reduction of the number of MES, up to 70%, was achieved. Doppler recordings suggest that the circulating bubbles were either fragmented into smaller bubble fragments or directly got pushed into the second subchannel where they were collected. This simple approach using an ultrasound-based trapping system was shown to operate adequately with the current settings and can be used to filter air microemboli.

  11. 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

  12. Assessing the variability in respiratory acoustic thoracic imaging (RATHI).

    PubMed

    Charleston-Villalobos, S; Torres-Jiménez, A; González-Camarena, R; Chi-Lem, G; Aljama-Corrales, T

    2014-02-01

    Multichannel analysis of lung sounds (LSs) has enabled the generation of a functional image for the temporal and spatial study of LS intensities in healthy and diseased subjects; this method is known as respiratory acoustic thoracic imaging (RATHI). This acoustic imaging technique has been applied to diverse pulmonary conditions, but it is important to contribute to the understanding of RATHI characteristics, such as acoustic spatial distribution, dependence on airflow and variability. The purpose of the current study is to assess the intra-subject and inter-subject RATHI variabilities in a cohort of 12 healthy male subjects (24.3±1.5 years) using diverse quantitative indices. The indices were obtained directly from the acoustic image and did not require scores from human raters, which helps to prevent inter-observer variability. To generate the acoustic image, LSs were acquired at 25 positions on the posterior thoracic surface by means of airborne sound sensors with a wide frequency band from 75 up to 1000 Hz under controlled airflow conditions at 1.0, 1.5 and 2.0 L/s. To assess intra-subject variability, the degree of similitude between inspiratory acoustic images was evaluated through quadratic mutual information based on the Cauchy-Schwartz inequality (I(CS)). The inter-subject variability was assessed by an image registration procedure between RATHIs and X-ray images to allow the computation of average and variance acoustic image in the same coordinate space. The results indicated that intra-subject RATHI similitude, reflected by I(CS-global), averaged 0.960±0.008, 0.958±0.008 and 0.960±0.007 for airflows of 1.0, 1.5, and 2L/s, respectively. As for the inter-subject variability, the variance image values for three airflow conditions indicated low image variability as they ranged from 0.01 to 0.04. In conclusion, the assessment of intra-subject and inter-subject variability by similitude indices indicated that the acoustic image pattern is repeatable along

  13. 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.

  14. Imaging and detection of mines from acoustic measurements

    NASA Astrophysics Data System (ADS)

    Witten, Alan J.; DiMarzio, Charles A.; Li, Wen; McKnight, Stephen W.

    1999-08-01

    A laboratory-scale acoustic experiment is described where a buried target, a hockey puck cut in half, is shallowly buried in a sand box. To avoid the need for source and receiver coupling to the host sand, an acoustic wave is generated in the subsurface by a pulsed laser suspended above the air-sand interface. Similarly, an airborne microphone is suspended above this interface and moved in unison with the laser. After some pre-processing of the data, reflections for the target, although weak, could clearly be identified. While the existence and location of the target can be determined by inspection of the data, its unique shape can not. Since target discrimination is important in mine detection, a 3D imaging algorithm was applied to the acquired acoustic data. This algorithm yielded a reconstructed image where the shape of the target was resolved.

  15. 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.

  16. Femtosecond imaging of nonlinear acoustics in gold.

    PubMed

    Pezeril, Thomas; Klieber, Christoph; Shalagatskyi, Viktor; Vaudel, Gwenaelle; Temnov, Vasily; Schmidt, Oliver G; Makarov, Denys

    2014-02-24

    We have developed a high-sensitivity, low-noise femtosecond imaging technique based on pump-probe time-resolved measurements with a standard CCD camera. The approach used in the experiment is based on lock-in acquisitions of images generated by a femtosecond laser probe synchronized to modulation of a femtosecond laser pump at the same rate. This technique allows time-resolved imaging of laser-excited phenomena with femtosecond time resolution. We illustrate the technique by time-resolved imaging of the nonlinear reshaping of a laser-excited picosecond acoustic pulse after propagation through a thin gold layer. Image analysis reveals the direct 2D visualization of the nonlinear acoustic propagation of the picosecond acoustic pulse. Many ultrafast pump-probe investigations can profit from this technique because of the wealth of information it provides over a typical single diode and lock-in amplifier setup, for example it can be used to image ultrasonic echoes in biological samples.

  17. Acoustic imaging for diagnostics of chemically reacting systems

    NASA Technical Reports Server (NTRS)

    Ramohalli, K.; Seshan, P.

    1983-01-01

    The concept of local diagnostics, in chemically reacting systems, with acoustic imaging is developed. The elements of acoustic imaging through ellipsoidal mirrors are theoretically discussed. In a general plan of the experimental program, the first system is chosen in these studies to be a simple open jet, non premixed turbulent flame. Methane is the fuel and enriched air is the oxidizer. This simple chemically reacting flow system is established at a Reynolds number (based on cold viscosity) of 50,000. A 1.5 m diameter high resolution acoustic mirror with an f-number of 0.75 is used to map the acoustic source zone along the axis of the flame. The results are presented as acoustic power spectra at various distances from the nozzle exit. It is seen that most of the reaction intensity is localized in a zone within 8 diameters from the exit. The bulk reactions (possibly around the periphery of the larger eddies) are evenly distributed along the length of the flame. Possibilities are seen for locally diagnosing single zones in a multiple cluster of reaction zones that occur frequently in practice. A brief outline is given of the future of this work which will be to apply this technique to chemically reacting flows not limited to combustion.

  18. Quantitative imaging of acoustic reflection and interference

    NASA Astrophysics Data System (ADS)

    Malkin, Robert; Todd, Thomas; Robert, Daniel

    2015-01-01

    This paper presents a method for time resolved quantitative imaging of acoustic waves. We present the theoretical background, the experimental method and the comparison between experimental and numerical reconstructions of acoustic reflection and interference. Laser Doppler vibrometry is used to detect the modulation of the propagation velocity of light, c, due to pressure-dependant changes in the refractive index of air. Variation in c is known to be proportional to variation in acoustic pressure and thus can be used to quantify sound pressure fluctuations. The method requires the laser beam to travel through the sound field, in effect integrating pressure along a transect line. We investigate the applicability of the method, in particular the effect of the geometry of the sound radiator on line integration. Both experimental and finite element reconstructions of the sound field are in good agreement, corroborating punctual pressure measurements from a precision microphone. Spatial limitations and accuracy of the method are presented and discussed.

  19. Scanning Michelson interferometer for imaging surface acoustic wave fields.

    PubMed

    Knuuttila, J V; Tikka, P T; Salomaa, M M

    2000-05-01

    A scanning homodyne Michelson interferometer is constructed for two-dimensional imaging of high-frequency surface acoustic wave (SAW) fields in SAW devices. The interferometer possesses a sensitivity of ~10(-5)nm/ radicalHz , and it is capable of directly measuring SAW's with frequencies ranging from 0.5 MHz up to 1 GHz. The fast scheme used for locating the optimum operation point of the interferometer facilitates high measuring speeds, up to 50,000 points/h. The measured field image has a lateral resolution of better than 1 mu;m . The fully optical noninvasive scanning system can be applied to SAW device development and research, providing information on acoustic wave distribution that cannot be obtained by merely electrical measurements.

  20. 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.

  1. Synchrotron x-ray imaging of acoustic cavitation bubbles induced by acoustic excitation

    NASA Astrophysics Data System (ADS)

    Jung, Sung Yong; Park, Han Wook; Park, Sung Ho; Lee, Sang Joon

    2017-04-01

    The cavitation induced by acoustic excitation has been widely applied in various biomedical applications because cavitation bubbles can enhance the exchanges of mass and energy. In order to minimize the hazardous effects of the induced cavitation, it is essential to understand the spatial distribution of cavitation bubbles. The spatial distribution of cavitation bubbles visualized by the synchrotron x-ray imaging technique is compared to that obtained with a conventional x-ray tube. Cavitation bubbles with high density in the region close to the tip of the probe are visualized using the synchrotron x-ray imaging technique, however, the spatial distribution of cavitation bubbles in the whole ultrasound field is not detected. In this study, the effects of the ultrasound power of acoustic excitation and working medium on the shape and density of the induced cavitation bubbles are examined. As a result, the synchrotron x-ray imaging technique is useful for visualizing spatial distributions of cavitation bubbles, and it could be used for optimizing the operation conditions of acoustic cavitation.

  2. Nonlinear ultrasound imaging of nanoscale acoustic biomolecules

    NASA Astrophysics Data System (ADS)

    Maresca, David; Lakshmanan, Anupama; Lee-Gosselin, Audrey; Melis, Johan M.; Ni, Yu-Li; Bourdeau, Raymond W.; Kochmann, Dennis M.; Shapiro, Mikhail G.

    2017-02-01

    Ultrasound imaging is widely used to probe the mechanical structure of tissues and visualize blood flow. However, the ability of ultrasound to observe specific molecular and cellular signals is limited. Recently, a unique class of gas-filled protein nanostructures called gas vesicles (GVs) was introduced as nanoscale (˜250 nm) contrast agents for ultrasound, accompanied by the possibilities of genetic engineering, imaging of targets outside the vasculature and monitoring of cellular signals such as gene expression. These possibilities would be aided by methods to discriminate GV-generated ultrasound signals from anatomical background. Here, we show that the nonlinear response of engineered GVs to acoustic pressure enables selective imaging of these nanostructures using a tailored amplitude modulation strategy. Finite element modeling predicted a strongly nonlinear mechanical deformation and acoustic response to ultrasound in engineered GVs. This response was confirmed with ultrasound measurements in the range of 10 to 25 MHz. An amplitude modulation pulse sequence based on this nonlinear response allows engineered GVs to be distinguished from linear scatterers and other GV types with a contrast ratio greater than 11.5 dB. We demonstrate the effectiveness of this nonlinear imaging strategy in vitro, in cellulo, and in vivo.

  3. Nonlinear ultrasound imaging of nanoscale acoustic biomolecules.

    PubMed

    Maresca, David; Lakshmanan, Anupama; Lee-Gosselin, Audrey; Melis, Johan M; Ni, Yu-Li; Bourdeau, Raymond W; Kochmann, Dennis M; Shapiro, Mikhail G

    2017-02-13

    Ultrasound imaging is widely used to probe the mechanical structure of tissues and visualize blood flow. However, the ability of ultrasound to observe specific molecular and cellular signals is limited. Recently, a unique class of gas-filled protein nanostructures called gas vesicles (GVs) was introduced as nanoscale (∼250 nm) contrast agents for ultrasound, accompanied by the possibilities of genetic engineering, imaging of targets outside the vasculature and monitoring of cellular signals such as gene expression. These possibilities would be aided by methods to discriminate GV-generated ultrasound signals from anatomical background. Here, we show that the nonlinear response of engineered GVs to acoustic pressure enables selective imaging of these nanostructures using a tailored amplitude modulation strategy. Finite element modeling predicted a strongly nonlinear mechanical deformation and acoustic response to ultrasound in engineered GVs. This response was confirmed with ultrasound measurements in the range of 10 to 25 MHz. An amplitude modulation pulse sequence based on this nonlinear response allows engineered GVs to be distinguished from linear scatterers and other GV types with a contrast ratio greater than 11.5 dB. We demonstrate the effectiveness of this nonlinear imaging strategy in vitro, in cellulo, and in vivo.

  4. Acoustic imaging of subtle porosity variations in ceramics

    NASA Technical Reports Server (NTRS)

    Generazio, E. R.; Roth, D. J.; Baaklini, G. Y.

    1988-01-01

    Acoustic images of silicon carbide ceramic disks were obtained using a precision scanning contact pulse-echo technique. Phase and cross-correlation velocity and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with X-radiography.

  5. 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.

  6. Acoustic and photoacoustic molecular imaging of cancer.

    PubMed

    Wilson, Katheryne E; Wang, Tzu Yin; Willmann, Jürgen K

    2013-11-01

    Ultrasound and combined optical and ultrasonic (photoacoustic) molecular imaging have shown great promise in the visualization and monitoring of cancer through imaging of vascular and extravascular molecular targets. Contrast-enhanced ultrasound with molecularly targeted microbubbles can detect early-stage cancer through the visualization of targets expressed on the angiogenic vasculature of tumors. Ultrasonic molecular imaging can be extended to the imaging of extravascular targets through use of nanoscale, phase-change droplets and photoacoustic imaging, which provides further molecular information on cancer given by the chemical composition of tissues and by targeted nanoparticles that can interact with extravascular tissues at the receptor level. A new generation of targeted contrast agents goes beyond merely increasing imaging signal at the site of target expression but shows activatable and differential contrast depending on their interactions with the tumor microenvironment. These innovations may further improve our ability to detect and characterize tumors. In this review, recent developments in acoustic and photoacoustic molecular imaging of cancer are discussed.

  7. A method of imaging viscoelastic parameters with acoustic radiation force.

    PubMed

    Walker, W F; Fernandez, F J; Negron, L A

    2000-06-01

    Acoustic radiation force has been proposed as a method of interrogating the mechanical properties of tissue. One simple approach applies a series of focused ultrasonic pulses to generate an acoustic radiation force, then processes the echoes returned from these pulses to estimate the radiation-force-induced displacement as a function of time. This process can be repeated at a number of locations to acquire data for image formation. In previous work we have formed images of tissue stiffness by depicting the maximum displacement induced at each tissue location after a finite period of insonification. While these maximum displacement images are able to differentiate materials of disparate mechanical properties, they exploit only a fraction of the information available. In this paper we show that the time-displacement curves acquired from tissue mimicking phantoms exhibit a viscoelastic response which is accurately described by the Voigt model. We describe how the viscous and elastic parameters of this model may be determined from experimental data. Finally, we show phantom images that depict not only the maximum local displacement, but also the viscous and elastic model parameters. These images offer complementary information about the target.

  8. 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.

  9. Acoustical Imaging Cameras for the Inspection and Condition Assessment of Hydraulic Structures

    DTIC Science & Technology

    2010-08-01

    feasibility of using acoustical imaging for underwater inspection of structures. INTRODUCTION: Visibility in clear water for the human eye and optical ...but higher resolution than sidescan or multibeam acoustical images • Nonhomogeneity of returned signal caused by variation in angles of signals...acoustical imaging. To obtain higher resolutions than other acoustical imaging technologies such as multibeam and sidescan systems, acoustical camera

  10. 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…

  11. 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…

  12. High-Frequency Acoustic Impedance Imaging of Cancer Cells.

    PubMed

    Fadhel, Muhannad N; Berndl, Elizabeth S L; Strohm, Eric M; Kolios, Michael C

    2015-10-01

    Variations in the acoustic impedance throughout cells and tissue can be used to gain insight into cellular microstructures and the physiologic state of the cell. Ultrasound imaging can be used to create a map of the acoustic impedance, on which fluctuations can be used to help identify the dominant ultrasound scattering source in cells, providing information for ultrasound tissue characterization. The physiologic state of a cell can be inferred from the average acoustic impedance values, as many cellular physiologic changes are linked to an alteration in their mechanical properties. A recently proposed method, acoustic impedance imaging, has been used to measure the acoustic impedance maps of biological tissues, but the method has not been used to characterize individual cells. Using this method to image cells can result in more precise acoustic impedance maps of cells than obtained previously using time-resolved acoustic microscopy. We employed an acoustic microscope using a transducer with a center frequency of 375 MHz to calculate the acoustic impedance of normal (MCF-10 A) and cancerous (MCF-7) breast cells. The generated acoustic impedance maps and simulations suggest that the position of the nucleus with respect to the polystyrene substrate may have an effect on the measured acoustic impedance value of the cell. Fluorescence microscopy and confocal microscopy were used to correlate acoustic impedance images with the position of the nucleus within the cell. The average acoustic impedance statistically differed between normal and cancerous breast cells (1.636 ± 0.010 MRayl vs. 1.612 ± 0.006 MRayl), indicating that acoustic impedance could be used to differentiate between normal and cancerous cells. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  13. Magneto-acoustic imaging by continuous-wave excitation.

    PubMed

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

    2017-04-01

    The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10(-7) Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

  14. Acoustic images of gel dosimetry phantoms

    NASA Astrophysics Data System (ADS)

    Vieira, Silvio L.; Baggio, André; Kinnick, Randall R.; Fatemi, M.; Carneiro, Antonio Adilton O.

    2010-01-01

    This work presents Vibro-acoustography (VA) as a tool to visualize absorbed dose in a polymer gel dosimetry phantom. VA relies on the mechanical excitation introduced by the acoustic radiation force of focused modulated ultrasound in a small region of the object. A hydrophone or microphone is used to measure the sound emitted from the object in response to the excitation, and by using the amplitude or phase of this signal, an image of the object can be generated. To study the phenomena of dose distribution in a gel dosimetry phantom, continuous wave (CW), tone burst and multi-frequency VA were used to image this phantom. The phantom was designed using 'MAGIC' gel polymer with addition of glass microspheres at 2% w/w having an average diameter range between 40-75 μm. The gel was irradiated using conventional 10 MeV X-rays from a linear accelerator. The field size in the surface of the phantom was 1.0×1.0 cm2 and a source-surface distance (SSD) of 100 cm. The irradiated volume corresponds to an approximately 8.0 cm3, where a dose of 50 gray was delivered to the gel. Polymer gel dosimeters are sensitive to radiation-induced chemical changes that occur in the irradiated polymer. VA images of the gel dosimeter showed the irradiate area. It is concluded that VA imaging has potential to visualize dose distribution in a polymer gel dosimeter.

  15. 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.

  16. 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.

  17. Acoustic Radiation Force Impulse Imaging of Human Prostates ex vivo

    PubMed Central

    Zhai, Liang; Madden, John; Foo, Wen-Chi; Palmeri, Mark L.; Mouraviev, Vladimir; Polascik, Thomas J.; Nightingale, Kathryn R.

    2010-01-01

    It has been challenging for clinicians using current imaging modalities to visualize internal structures and detect lesions inside human prostates. Lack of contrast among prostatic tissues and high false positive or negative detection rates of prostate lesions have limited the use of current imaging modalities in the diagnosis of prostate cancer. In this study, Acoustic Radiation Force Impulse (ARFI) imaging is introduced to visualize the anatomic and abnormal structures in freshly excised human prostates. A modified Siemens Antares™ ultrasound scanner and a Siemens VF10-5 linear array were used to acquire ARFI images. The transducer was attached to a three-dimensional (3D) translation stage, which was programmed to automate volumetric data acquisition. A depth dependent gain (DDG) method was developed and applied to 3D ARFI datasets to compensate for the displacement gradients associated with spatially varying radiation force magnitudes as a function of depth. Nine human prostate specimens were collected and imaged immediately after surgical excision. Prostate anatomical structures such as seminal vesicles, ejaculatory ducts, peripheral zone, central zone, transition zone and verumontanum were visualized with high spatial resolution and in good agreement with McNeal's zonal anatomy. The characteristic appearance of prostate pathologies, such as prostate cancerous lesions, benign prostatic hyperplasia, calcified tissues and atrophy were identified in ARFI images based upon correlation with the corresponding histological slides. This study demonstrates that ARFI imaging can be used to visualize internal structures and detecting suspicious lesions in the prostate and appears promising for image guidance of prostate biopsy. PMID:20350685

  18. Far-field image magnification for acoustic waves using anisotropic acoustic metamaterials.

    PubMed

    Ao, Xianyu; Chan, C T

    2008-02-01

    A kind of two-dimensional acoustic metamaterial is designed so that it exhibits strong anisotropy along two orthogonal directions. Based on the rectangular equal frequency contour of this metamaterial, magnifying lenses for acoustic waves, analogous to electromagnetic hyperlenses demonstrated recently in the optical regime, can be realized. Such metamaterial may offer applications in imaging for systems that obey scalar wave equations.

  19. 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.

  20. 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.

  1. 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

  2. Pressure Sensitivity Kernels Applied to Time-reversal Acoustics

    DTIC Science & Technology

    2009-06-29

    diversity in passive time reversal com- munications,” Journal of the Acoustical Society of America, October 2006, Vol. 120, Issue 4, pp. 2067-2076. xvi 5...communications. J. Acoustic Soc. Am., 115:2468–2468, 2004. [3] P. Gerstoft. Inversion of seismo-acoustic data using genetic algorithms and a posteriori...average of focal spots tends to have high stability.[6] The presence of spatial diversity (large arrays) has the same effect as an ensemble average and

  3. Image reconstruction in photoacoustic tomography involving layered acoustic media

    PubMed Central

    Schoonover, Robert W.; Anastasio, Mark A.

    2012-01-01

    Photoacoustic tomography (PAT), also known as thermoacoustic or optoacoustic tomography, is a rapidly emerging biomedical imaging technique that combines optical image contrast with ultrasound detection principles. Most existing reconstruction algorithms for PAT assume the object of interest possesses homogeneous acoustic properties. The images produced by such algorithms can contain significant distortions and artifacts when the object’s acoustic properties are spatially variant. In this work, we establish an image reconstruction formula for PAT applications in which a planar detection surface is employed and the to-be-imaged optical absorber is embedded in a known planar layered acoustic medium. The reconstruction formula is exact in a mathematical sense and accounts for multiple acoustic reflections between the layers of the medium. Computer-simulation studies are conducted to demonstrate and investigate the proposed method. PMID:21643397

  4. Acoustic-noise-optimized diffusion-weighted imaging.

    PubMed

    Ott, Martin; Blaimer, Martin; Grodzki, David M; Breuer, Felix A; Roesch, Julie; Dörfler, Arnd; Heismann, Björn; Jakob, Peter M

    2015-12-01

    This work was aimed at reducing acoustic noise in diffusion-weighted MR imaging (DWI) that might reach acoustic noise levels of over 100 dB(A) in clinical practice. A diffusion-weighted readout-segmented echo-planar imaging (EPI) sequence was optimized for acoustic noise by utilizing small readout segment widths to obtain low gradient slew rates and amplitudes instead of faster k-space coverage. In addition, all other gradients were optimized for low slew rates. Volunteer and patient imaging experiments were conducted to demonstrate the feasibility of the method. Acoustic noise measurements were performed and analyzed for four different DWI measurement protocols at 1.5T and 3T. An acoustic noise reduction of up to 20 dB(A) was achieved, which corresponds to a fourfold reduction in acoustic perception. The image quality was preserved at the level of a standard single-shot (ss)-EPI sequence, with a 27-54% increase in scan time. The diffusion-weighted imaging technique proposed in this study allowed a substantial reduction in the level of acoustic noise compared to standard single-shot diffusion-weighted EPI. This is expected to afford considerably more patient comfort, but a larger study would be necessary to fully characterize the subjective changes in patient experience.

  5. 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

  6. 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.

  7. Acoustic radiation force elasticity imaging in diagnostic ultrasound.

    PubMed

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

    2013-04-01

    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 noninvasively 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.

  8. 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

  9. CO2 leak detection through acoustic sensing and infrared imaging

    NASA Astrophysics Data System (ADS)

    Cui, Xiwang; Yan, Yong; Ma, Lin; Ma, Yifan; Han, Xiaojuan

    2014-04-01

    When CO2 leakage occurs from a high pressure enclosure, the CO2 jet formed can produce fierce turbulent flow generating acoustic emission with possible phase change, depending on the pressure of the enclosure, and a significant temperature drop in the region close to the releasing point. Acoustic Emission (AE) and infrared imaging technologiesare promising methods for on-line monitoring of such accidental leakage. In this paper, leakage experiments were carried out with a CO2 container under well controlled conditions in a laboratory. Acoustic signals and temperature distribution at the leakage area were acquired using an acoustic sensor and an infraredthermalimaging camera. The acoustic signal was analyzed in both time and frequency domains. The characteristics of the signal frequencies areidentified, and their suitability for leakage detectionis investigated. The location of the leakage can be identified by seeking the lowest temperature area or point in the infrared image.

  10. Ultrasonic phased array with surface acoustic wave for imaging cracks

    NASA Astrophysics Data System (ADS)

    Ohara, Yoshikazu; Oshiumi, Taro; Nakajima, Hiromichi; Yamanaka, Kazushi; Wu, Xiaoyang; Uchimoto, Tetsuya; Takagi, Toshiyuki; Tsuji, Toshihiro; Mihara, Tsuyoshi

    2017-06-01

    To accurately measure crack lengths, we developed a real-time surface imaging method (SAW PA) combining an ultrasonic phased array (PA) with a surface acoustic wave (SAW). SAW PA using a Rayleigh wave with a high sensitivity to surface defects was implemented for contact testing using a wedge with the third critical angle that allows the Rayleigh wave to be generated. Here, to realize high sensitivity imaging, SAW PA was optimized in terms of the wedge and the imaging area. The improved SAW PA was experimentally demonstrated using a fatigue crack specimen made of an aluminum alloy. For further verification in more realistic specimens, SAW PA was applied to stainless-steel specimens with a fatigue crack and stress corrosion cracks (SCCs). The fatigue crack was visualized with a high signal-to-noise ratio (SNR) and its length was measured with a high accuracy of better than 1 mm. The SCCs generated in the heat-affected zones (HAZs) of a weld were successfully visualized with a satisfactory SNR, although responses at coarse grains appeared throughout the imaging area. The SCC lengths were accurately measured. The imaging results also precisely showed complicated distributions of SCCs, which were in excellent agreement with the optically observed distributions.

  11. Sparse Reconstruction for Micro Defect Detection in Acoustic Micro Imaging

    PubMed Central

    Zhang, Yichun; Shi, Tielin; Su, Lei; Wang, Xiao; Hong, Yuan; Chen, Kepeng; Liao, Guanglan

    2016-01-01

    Acoustic micro imaging has been proven to be sufficiently sensitive for micro defect detection. In this study, we propose a sparse reconstruction method for acoustic micro imaging. A finite element model with a micro defect is developed to emulate the physical scanning. Then we obtain the point spread function, a blur kernel for sparse reconstruction. We reconstruct deblurred images from the oversampled C-scan images based on l1-norm regularization, which can enhance the signal-to-noise ratio and improve the accuracy of micro defect detection. The method is further verified by experimental data. The results demonstrate that the sparse reconstruction is effective for micro defect detection in acoustic micro imaging. PMID:27783040

  12. Incident Wave Removal for Defect Enhancement in Acoustic Wavefield Imaging

    NASA Astrophysics Data System (ADS)

    Master, Zubin M.; Michaels, Thomas E.; Michaels, Jennifer E.

    2007-03-01

    The method of Acoustic Wavefield Imaging (AWI) offers many advantages over conventional ultrasonic techniques for nondestructive evaluation, and also provides a means of incorporating fixed ultrasonic sensors used for structural health monitoring into subsequent inspections. AWI utilizes these fixed sensors as wave sources and an externally scanned ultrasonic transducer (or laser interferometer) as a receiver to acquire complete waveform data over the surface. When displayed as time-dependent images, these signals show the propagation of acoustic waves through a structure and subsequent interactions of these waves with both defects and structural geometry. Defect areas appear as stationary scattering sources on these images, but such scattered wave energy is often obscured by the stronger incident acoustic wavefield. The objective of the work presented here is to develop multidimensional signal processing algorithms to enhance the appearance of structural defects on wavefield images via removal of the incident wave. Results are presented for analysis of images from aluminum plate and solid laminate composite specimens.

  13. Sparse Reconstruction for Micro Defect Detection in Acoustic Micro Imaging.

    PubMed

    Zhang, Yichun; Shi, Tielin; Su, Lei; Wang, Xiao; Hong, Yuan; Chen, Kepeng; Liao, Guanglan

    2016-10-24

    Acoustic micro imaging has been proven to be sufficiently sensitive for micro defect detection. In this study, we propose a sparse reconstruction method for acoustic micro imaging. A finite element model with a micro defect is developed to emulate the physical scanning. Then we obtain the point spread function, a blur kernel for sparse reconstruction. We reconstruct deblurred images from the oversampled C-scan images based on l₁-norm regularization, which can enhance the signal-to-noise ratio and improve the accuracy of micro defect detection. The method is further verified by experimental data. The results demonstrate that the sparse reconstruction is effective for micro defect detection in acoustic micro imaging.

  14. Shape-adaptable hyperlens for acoustic magnifying imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Hongkuan; Zhou, Xiaoming; Hu, Gengkai

    2016-11-01

    Previous prototypes of acoustic hyperlens consist of rigid channels, which are unable to adapt in shape to the object under detection. We propose to overcome this limitation by employing soft plastic tubes that could guide acoustics with robustness against bending deformation. Based on the idea of soft-tube acoustics, acoustic magnifying hyperlens with planar input and output surfaces has been fabricated and validated experimentally. The shape-adaption capability of the soft-tube hyperlens is demonstrated by a controlled experiment, in which the magnifying super-resolution images remain stable when the lens input surface is curved. Our study suggests a feasible route toward constructing the flexible channel-structured acoustic metamaterials with the shape-adaption capability, opening then an additional degree of freedom for full control of sound.

  15. 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.

  16. Dual Frequency Acoustic Droplet Vaporization Detection for Medical Imaging

    PubMed Central

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

    2017-01-01

    Liquid-filled perfluorocarbon droplets emit a unique acoustic signature when vaporized into to 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 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 stand-alone diagnostic system to monitor the physical properties of the surrounding environment. PMID:26415125

  17. Applied topology optimization of vibro-acoustic hearing instrument models

    NASA Astrophysics Data System (ADS)

    Søndergaard, Morten Birkmose; Pedersen, Claus B. W.

    2014-02-01

    Designing hearing instruments remains an acoustic challenge as users request small designs for comfortable wear and cosmetic appeal and at the same time require sufficient amplification from the device. First, to ensure proper amplification in the device, a critical design challenge in the hearing instrument is to minimize the feedback between the outputs (generated sound and vibrations) from the receiver looping back into the microphones. Secondly, the feedback signal is minimized using time consuming trial-and-error design procedures for physical prototypes and virtual models using finite element analysis. In the present work it is demonstrated that structural topology optimization of vibro-acoustic finite element models can be used to both sufficiently minimize the feedback signal and to reduce the time consuming trial-and-error design approach. The structural topology optimization of a vibro-acoustic finite element model is shown for an industrial full scale model hearing instrument.

  18. Nested sampling applied in Bayesian room-acoustics decay analysis.

    PubMed

    Jasa, Tomislav; Xiang, Ning

    2012-11-01

    Room-acoustic energy decays often exhibit single-rate or multiple-rate characteristics in a wide variety of rooms/halls. Both the energy decay order and decay parameter estimation are of practical significance in architectural acoustics applications, representing two different levels of Bayesian probabilistic inference. This paper discusses a model-based sound energy decay analysis within a Bayesian framework utilizing the nested sampling algorithm. The nested sampling algorithm is specifically developed to evaluate the Bayesian evidence required for determining the energy decay order with decay parameter estimates as a secondary result. Taking the energy decay analysis in architectural acoustics as an example, this paper demonstrates that two different levels of inference, decay model-selection and decay parameter estimation, can be cohesively accomplished by the nested sampling algorithm.

  19. Vibro-acoustic Imaging at the Breazeale Reactor

    SciTech Connect

    Smith, James Arthur; Jewell, James Keith; Lee, James Edwin

    2016-09-01

    The INL is developing Vibro-acoustic imaging technology to characterize microstructure in fuels and materials in spent fuel pools and within reactor vessels. A vibro-acoustic development laboratory has been established at the INL. The progress in developing the vibro-acoustic technology at the INL is the focus of this report. A successful technology demonstration was performed in a working TRIGA research reactor. Vibro-acoustic imaging was performed in the reactor pool of the Breazeale reactor in late September of 2015. A confocal transducer driven at a nominal 3 MHz was used to collect the 60 kHz differential beat frequency induced in a spent TRIGA fuel rod and empty gamma tube located in the main reactor water pool. Data was collected and analyzed with the INLDAS data acquisition software using a short time Fourier transform.

  20. Photoacoustic imaging using acoustic reflectors to enhance planar arrays.

    PubMed

    Ellwood, Robert; Zhang, Edward; Beard, Paul; Cox, Ben

    2014-12-01

    Planar sensor arrays have advantages when used for photoacoustic imaging: they do not require the imaging target to be enclosed, and they are easier to manufacture than curved arrays. However, planar arrays have a limited view of the acoustic field due to their finite size; therefore, not all of the acoustic waves emitted from a photoacoustic source can be recorded. This loss of data results in artifacts in the reconstructed photoacoustic image. A detection array configuration which combines a planar Fabry–Pérot sensor with perpendicular acoustic reflectors is described and experimentally implemented. This retains the detection advantages of the planar sensor while increasing the effective detection aperture in order to improve the reconstructed photoacoustic image.

  1. Acoustic imaging in a water filled metallic pipe

    NASA Astrophysics Data System (ADS)

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

    1984-04-01

    A method is described for imaging 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.

  2. 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.

  3. 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.

  4. Modified electron acoustic field and energy applied to observation data

    SciTech Connect

    Abdelwahed, H. G. E-mail: hgomaa-eg@mans.edu.eg; El-Shewy, E. K.

    2016-08-15

    Improved electrostatic acoustic field and energy have been debated in vortex trapped hot electrons and fluid of cold electrons with pressure term plasmas. The perturbed higher-order modified-Korteweg-de Vries equation (PhomKdV) has been worked out. The effect of trapping and electron temperatures on the electro-field and energy properties in auroral plasmas has been inspected.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Acoustical properties of selected tissue phantom materials for ultrasound imaging.

    PubMed

    Zell, K; Sperl, J I; Vogel, M W; Niessner, R; Haisch, C

    2007-10-21

    This note summarizes the characterization of the acoustic properties of four materials intended for the development of tissue, and especially breast tissue, phantoms for the use in photoacoustic and ultrasound imaging. The materials are agar, silicone, polyvinyl alcohol gel (PVA) and polyacrylamide gel (PAA). The acoustical properties, i.e., the speed of sound, impedance and acoustic attenuation, are determined by transmission measurements of sound waves at room temperature under controlled conditions. Although the materials are tested for application such as photoacoustic phantoms, we focus here on the acoustic properties, while the optical properties will be discussed elsewhere. To obtain the acoustic attenuation in a frequency range from 4 MHz to 14 MHz, two ultrasound sources of 5 MHz and 10 MHz core frequencies are used. For preparation, each sample is cast into blocks of three different thicknesses. Agar, PVA and PAA show similar acoustic properties as water. Within silicone polymer, a significantly lower speed of sound and higher acoustical attenuation than in water and human tissue were found. All materials can be cast into arbitrary shapes and are suitable for tissue-mimicking phantoms. Due to its lower speed of sound, silicone is generally less suitable than the other presented materials.

  11. Acoustically modulated x-ray phase contrast imaging.

    PubMed

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

    2004-11-07

    We report the use of ultrasonic radiation pressure with phase contrast x-ray imaging to give an image proportional to the space derivative of a conventional phase contrast image in the direction of propagation of an ultrasonic beam. Intense ultrasound is used to exert forces on objects within a body giving displacements of the order of tens to hundreds of microns. Subtraction of images made with and without the ultrasound field gives an image that removes low spatial frequency features and highlights high frequency features. The method acts as an acoustic 'contrast agent' for phase contrast x-ray imaging, which in soft tissue acts to highlight small density changes.

  12. 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.

  13. Imaging of Acoustic Waves in Piezoelectric Ceramics by Coulomb Coupling

    NASA Astrophysics Data System (ADS)

    Habib, Anowarul; Shelke, Amit; Pluta, Mieczyslaw; Kundu, Tribikram; Pietsch, Ullrich; Grill, Wolfgang

    2012-07-01

    The transport properties of bulk and guided acoustic waves travelling in a lead zirconate titanate (PZT) disc, originally manufactured to serve as ultrasonic transducer, have been monitored by scanned Coulomb coupling. The images are recorded by excitation and detection of ultrasound with local electric field probes via piezoelectric coupling. A narrow pulse has been used for excitation. Broadband coupling is achieved since neither mechanical nor electrical resonances are involved. The velocities of the traveling acoustic waves determined from the images are compared with characteristic velocities calculated from material properties listed by the manufacturer of the PZT plate.

  14. High-Speed Vortex Wind Velocity Imaging by Acoustic Tomography

    NASA Astrophysics Data System (ADS)

    Li, H.; Ueki, T.; Hayashi, K.; Yamada, A.

    A technique for monitoring strong vortex wind fields is highly desired due to the rapid development of global warming. Vortex wind velocity imaging using an acoustic travel time tomography technique was developed to meet this need. The method can be implemented with a small number of parallel facing pairs of acoustic transmitters/receivers from just a single illumination view direction, so that high-speed data acquisition compatible with instantaneous wind-flow imaging was accomplished. A test using an indoor wind velocity tomography system demonstrated that vortex wind velocity profiles generated by an electric fan could be instantaneously reconstructed with satisfactory quantitative precision.

  15. Acoustic Mine Imaging (AMI) project: An underwater acoustic camera for use in mine warfare

    NASA Astrophysics Data System (ADS)

    Ellis, Colin; Murphy, Ed

    2004-05-01

    This paper is submitted to detail the advances in sonar and imaging techniques and synthetic apertures being made in Australia by Thales Underwater Systems within a Australian Defence Acquisition Project termed Acoustic Mine Imaging (AMI). This paper will detail the development of the AMI underwater acoustic camera for the detection, classification and characterization of mines and other underwater objects in turbid water where optical imaging is ineffective. It will explain the history of the development from a DSTO concept to the current system. It will detail how the acoustic camera provides real-time milimetric resolution three-dimensional images and how the design has had to meet practical operational constraints to allow seamless mounting onto a small, remotely controlled underwater vehicle for mine disposal operations. An overview of the processing architecture and technical complexity of the AMI will be provided, including detail on the design and development of the required submilimeter transducers and 2D matrix array. The paper will reflect on the technical and operational challenges that had to be addressed. Finally, trial results will be presented that will demonstrate the real-time capability of the acoustic camera in various environments.

  16. Acoustic imaging of underground storage tank wastes

    SciTech Connect

    Mech, S.J.

    1995-09-01

    Acoustics is a potential tool to determine the properties of high level wastes stored in Underground Storage Tanks. Some acoustic properties were successfully measured by a limited demonstration conducted in 114-TX. This accomplishment provides the basis for expanded efforts to qualify techniques which depend on the acoustic properties of tank wastes. This work is being sponsored by the Department of Energy under the Office of Science and Technology. In FY-1994, limited Tank Waste Remediation Systems EM-30 support was available at Hanford and Los Alamos National Laboratory. The Massachusetts Institute of Technology (MIT) and Earth Resources Laboratory (ERL) were engaged for analysis support, and Elohi Geophysics, Inc. for seismic testing services. Westinghouse-Hanford Company provided the testing and training, supplied the special engineering and safety analysis equipment and procedures, and provided the trained operators for the actual tank operations. On 11/9/94, limited in-tank tests were successfully conducted in tank 114-TX. This stabilized Single Shell Tank was reported as containing 16.8 feet of waste, the lower 6.28 feet of which contained interstitial liquid. Testing was conducted over the lower 12 feet, between two Liquid Observation Wells thirty feet apart. The ``quick-look`` data was reviewed on-site by MIT and Elohi.

  17. A combined microphone and camera calibration technique with application to acoustic imaging.

    PubMed

    Legg, Mathew; Bradley, Stuart

    2013-10-01

    We present a calibration technique for an acoustic imaging microphone array, combined with a digital camera. Computer vision and acoustic time of arrival data are used to obtain microphone coordinates in the camera reference frame. Our new method allows acoustic maps to be plotted onto the camera images without the need for additional camera alignment or calibration. Microphones and cameras may be placed in an ad-hoc arrangement and, after calibration, the coordinates of the microphones are known in the reference frame of a camera in the array. No prior knowledge of microphone positions, inter-microphone spacings, or air temperature is required. This technique is applied to a spherical microphone array and a mean difference of 3 mm was obtained between the coordinates obtained with this calibration technique and those measured using a precision mechanical method.

  18. Acoustic-resolution photoacoustic imaging system with simple fiber illumination

    NASA Astrophysics Data System (ADS)

    Tsunoi, Yasuyuki; Sato, Shunichi; Watanabe, Ryota; Kawauchi, Satoko; Ashida, Hiroshi; Terakawa, Mitsuhiro

    2013-03-01

    Acoustic-resolution photoacoustic microscopy (AR-PAM) with dark-field confocal illumination enables unique high-resolution visualization of chromophores in tissue, such as microvasculatures, within depths of a few millimeters. However, most current systems are bulky and use complex optical components for illumination, thus requiring highly sensitive alignment. In this study, we developed a compact alignment-free acoustic-resolution photoacoustic imaging system with simple fiber illumination. Four optical fibers were placed in four directions around a high-frequency (30-MHz) ultrasound sensor attached with the high-numerical-aperture acoustic lens. The setting angle of the fibers were determined to form a dark field on the tissue surface under the acoustic lens and for the four light beams from the fibers to be combined near the focal point of the acoustic lens, i.e., at a depth of around 1.2 mm in the tissue. The acoustic lens and output ends of the fibers were capped with an acoustically and optically transparent engineering plastic sheet, whose surface can be directly placed and scanned on the tissue surface with ultrasound gel. The diameter and height of this imaging head were as small as 32 mm and 27 mm respectively. The phantom study showed that the lateral signal spreading was 120 μm, which agreed well with the theoretical value of 112 μm. With the system, we attempted to image vasculatures in the rat skin, demonstrating high-contrast visualization of the blood vessels of a few hundred micrometers in diameter in the tissue.

  19. Acoustic Molecular Imaging and Targeted Drug Delivery with Perfluorocarbon Nanoparticles

    NASA Astrophysics Data System (ADS)

    Lanza, Gregory M.; Hughes, Michael. S.; Marsh, Jon N.; Scott, Michael J.; Zhang, Huiying; Lacy, Elizabeth K.; Allen, John S.; Wickline, Samuel A.

    2005-03-01

    Advances in molecular biology and cellular biochemistry are providing new opportunities for diagnostic medical imaging to "see" beyond the anatomical manifestations of disease to the earliest biochemical signatures of disease. Liquid perfluorocarbon nanoparticles provide inherent acoustic contrast when bound to targets, e.g., fibrin deposits in a thrombus, but unbound nanoparticles are undetectable. This nanoparticle platform may be further functionalized with paramagnetic metals, such as gadolinium, or radionuclides, with homing ligands, like anti-αvβ3-integrins, and therapeutic agents. Acoustic imaging of densely distributed biomarkers, e.g., fibrin epitopes, is readily accommodated with fundamental imaging, but for sparse biomarkers, e.g., integrins, we have developed and implemented novel, nonlinear imaging techniques based upon information-theoretic receivers (i.e., thermodynamic receivers). These novel receivers allow sensitive direct imaging of contrast development.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Equivalent Source Method Applied to Launch Acoustic Simulations

    NASA Technical Reports Server (NTRS)

    Housman, Jeffrey A.; Barad, Michael F.; Kiris, Cetin

    2012-01-01

    Aeroacoustic simulations of the launch environment are described. A hybrid computational fluid dynamics (CFD)/computational aeroacoustic (CAA) approach is developed in order to accurately and efficiently predict the sound pressure level spectrum on the launch vehicle and surrounding structures. The high-fidelity CFD code LAVA (Launch Ascent and Vehicle Analysis), is used to generate pressure time history at select locations in the flow field. A 3D exterior Helmholtz solver is then used to iteratively determine a set of monopole sources which mimic the noise generating mechanisms identified by the CFD solver. The acoustic pressure field generated from the Helmholtz solver is then used to evaluate the sound pressure levels.

  5. Acoustic emission applied to detect workpiece burn during grinding

    SciTech Connect

    Aguiar, P.R. de; Willett, P.; Webster, J.

    1999-07-01

    Overly-aggressive or otherwise inappropriate grinding of metals can produce an undesirable change in metallurgical properties of the material being processed; usually this is referred to as workpiece burn. In this experimental paper the acoustic signature of grinding is collected, and compared to the processed workpiece condition, for thirteen data sets including both relatively hard (Inconel) and soft (52100 bearing steel) metals. This work is distinguished by its use of a high sampling rate (2.56 MHz) in data acquisition and in its processing of the raw, rather than RMS/filtered, data samples. Signs of burn are seen in the frequency domain, and in the correlation between wheel rotations.

  6. 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.

  7. Photoacoustic image reconstruction: material detection and acoustical heterogeneities

    NASA Astrophysics Data System (ADS)

    Schoeder, S.; Kronbichler, M.; Wall, W. A.

    2017-05-01

    The correct consideration of acoustical heterogeneities in the context of photoacoustic image reconstruction is an open topic. In this publication a physically motivated algorithm is proposed that reconstructs the optical absorption and diffusion coefficients using a gradient-based scheme. The simultaneous reconstruction of both material properties allows for a subsequent material identification and an accordant update of the acoustical material properties. The algorithm is general in terms of illumination scenarios, detection geometries and applications. No prior knowledge on material distributions needs to be provided, only expected materials have to be specified. Numerical experiments are performed to gain insight into the complex inverse problem and to validate the proposed method. Results show that acoustical heterogeneities are correctly detected improving the optical images.

  8. Matrix methods applied to acoustic waves in multilayers

    NASA Astrophysics Data System (ADS)

    Adler, Eric L.

    1990-11-01

    Matrix methods for analyzing the electroacoustic characteristics of anisotropic piezoelectric multilayers are described. The conceptual usefulness of the methods is demonstrated in a tutorial fashion by examples showing how formal statements of propagation, transduction, and boundary-value problems in complicated acoustic layered geometries such as those which occur in surface acoustic wave (SAW) devices, in multicomponent laminates, and in bulk-wave composite transducers are simplified. The formulation given reduces the electroacoustic equations to a set of first-order matrix differential equations, one for each layer, in the variables that must be continuous across interfaces. The solution to these equations is a transfer matrix that maps the variables from one layer face to the other. Interface boundary conditions for a planar multilayer are automatically satisfied by multiplying the individual transfer matrices in the appropriate order, thus reducing the problem to just having to impose boundary conditions appropriate to the remaining two surfaces. The computational advantages of the matrix method result from the fact that the problem rank is independent of the number of layers, and from the availability of personal computer software that makes interactive numerical experimentation with complex layered structures practical.

  9. Acoustic imaging for temperature distribution reconstruction

    NASA Astrophysics Data System (ADS)

    Jia, Ruixi; Xiong, Qingyu; Liang, Shan

    2016-12-01

    For several industrial processes, such as burning and drying, temperature distribution is important because it can reflect the internal running state of industrial equipment and assist to develop control strategy and ensure safety in operation of industrial equipment. The principle of this technique is mainly based on the relationship between acoustic velocity and temperature. In this paper, an algorithm for temperature distribution reconstruction is considered. Compared with reconstruction results of simulation experiments with the least square algorithm and the proposed one, the latter indicates a better information reflection of temperature distribution and relatively higher reconstruction accuracy.

  10. 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.

  11. Acoustic Pyrometry Applied to Gas Turbines and Jet Engines

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.

    1999-01-01

    Internal gas temperature is one of the most fundamental parameters related to engine efficiency and emissions production. The most common methods for measuring gas temperature are physical probes, such as thermocouples and thermistors, and optical methods, such as Coherent Anti Stokes Raman Spectroscopy (CARS) or Rayleigh scattering. Probes are relatively easy to use, but they are intrusive, their output must be corrected for errors due to radiation and conduction, and their upper use temperature is limited. Optical methods are nonintrusive, and they measure some intrinsic property of the gas that is directly related to its temperature (e.g., lifetime or the ratio of line strengths). However, optical methods are usually difficult to use, and optical access is not always available. Lately, acoustic techniques have been receiving some interest as a way to overcome these limitations.

  12. Synthetic Aperture Acoustic Imaging for Roadside Detection of Solid Objects

    DTIC Science & Technology

    2014-11-20

    policy or decision, unless so designated by other documentation. 14. ABSTRACT A synthetic apertme acoustic system was developed to detect roadside...threats including IEDs and landmines. The technique uses audio-band sound broadcast from a compact trailer-mounted system to image the roadside...landmines. The technique uses audio-band sound broadcast from a compact trailer-mounted system to image the roadside perpendicular to the travel path. The

  13. Estimation of the Tool Condition by Applying the Wavelet Transform to Acoustic Emission Signals

    SciTech Connect

    Gomez, M. P.; Piotrkowski, R.; Ruzzante, J. E.; D'Attellis, C. E.

    2007-03-21

    This work follows the search of parameters to evaluate the tool condition in machining processes. The selected sensing technique is acoustic emission and it is applied to a turning process of steel samples. The obtained signals are studied using the wavelet transformation. The tool wear level is quantified as a percentage of the final wear specified by the Standard ISO 3685. The amplitude and relevant scale obtained of acoustic emission signals could be related with the wear level.

  14. A Correlated Microwave-Acoustic Imaging method for early-stage cancer detection.

    PubMed

    Gao, Fei; Zheng, Yuanjin

    2012-01-01

    Microwave-based imaging technique shows large potential in detecting early-stage cancer due to significant dielectric contrast between tumor and surrounding healthy tissue. In this paper, we present a new way named Correlated Microwave-Acoustic Imaging (CMAI) of combining two microwave-based imaging modalities: confocal microwave imaging(CMI) by detecting scattered microwave signal, and microwave-induced thermo-acoustic imaging (TAI) by detecting induced acoustic signal arising from microwave energy absorption and thermal expansion. Necessity of combining CMI and TAI is analyzed theoretically, and by applying simple algorithm to CMI and TAI separately, we propose an image correlation approach merging CMI and TAI together to achieve better performance in terms of resolution and contrast. Preliminary numerical simulation shows promising results in case of low contrast and large variation scenarios. A UWB transmitter is designed and tested for future complete system implementation. This preliminary study inspires us to develop a new medical imaging modality CMAI to achieve real-time, high resolution and high contrast simultaneously.

  15. Pressure sensitivity kernels applied to time-reversal acoustics

    NASA Astrophysics Data System (ADS)

    Raghukumar, Kaustubha

    Time-reversal is a method of focusing sound in the ocean that has found a variety of applications in recent years, ranging from underwater communications to biological stone destruction. In order to produce a focal spot, the time-reversal process first needs to acquire the Green's function between source and receiver. This Green's function is time-reversed and retransmitted in order to produce a spatio-temporal focal spot at the original source location. If the medium properties in between the source and receiver change between the acquisition of the Green's function and the subsequent retransmission, the quality of the focal spot can degrade or even disappear. However, the time-reversal focal spot has been found to be surprisingly robust to changes in medium properties, which are chiefly sound speed fluctuations in underwater acoustics. At 445 Hz, the focal spot was seen to persist for a week, while at 3.5 kHz, the focal spot persists for about an hour. Sensitivity kernels have the ability to linearly map sound speed perturbations to a perturbation of an acoustic parameter such as travel-time or pressure. Sensitivity kernels have a Fresnel-like interference pattern with regions of positive and negative sensitivities in the medium. Time-reversal, which causes different arrival paths to arrive at the same time, results in overlapping sensitivity kernels that leads to a net reduction in pressure sensitivity at the focal spot. Upon expressing the pressure at the focal spot in terms of sensitivity kernels, source transmissions are derived that are even more robust than time-reversal. The theory developed using pressure sensitivity kernels is tested on experimental data, along with an internal wave model, using various metrics. The linear limitations of the kernels are explored in the context of time-evolving Green's functions. The optimized source functions are then tested using experimental Green's functions and their behavior is seen to be in the right sense. Finally

  16. Acoustic property measurements in a photoacoustic imager

    NASA Astrophysics Data System (ADS)

    Willemink, René G. H.; Manohar, Srirang; Slump, Cornelis H.; van der Heijden, Ferdi; van Leeuwen, Ton

    2007-07-01

    Photoacoustics is a hybrid imaging technique that combines the contrast available to optical imaging with the resolution that is possessed by ultrasound imaging. The technique is based on generating ultrasound from absorbing structures in tissue using pulsed light. In photoacoustic (PA) computerized tomography (CT) imaging, reconstruction of the optical absorption in a subject, is performed for example by filtered backprojection. The backprojection is performed along circular paths in image space instead of along straight lines as in X-ray CT imaging. To achieve this, the speed-of-sound through the subject is usually assumed constant. An unsuitable speed-of-sound can degrade resolution and contrast. We discuss here a method of actually measuring the speed-of- sound distribution using ultrasound transmission through the subject under photoacoustic investigation. This is achieved in a simple approach that does not require any additional ultrasound transmitter. The method uses a passive element (carbon fiber) that is placed in the imager in the path of the illumination which generates ultrasound by the photoacoustic effect and behaves as an ultrasound source. Measuring the time-of-flight of this ultrasound transient by the same detector used for conventional photoacoustics, allows a speed-of-sound image to be reconstructed. This concept is validated on phantoms.

  17. Arterial stiffness measurements with acoustic radiation force impulse imaging

    NASA Astrophysics Data System (ADS)

    Trahey, Gregg E.; Dahl, Jeremy J.; McAleavey, Stephen A.; Gallippi, Caterina M.; Nightingale, Kathryn R.

    2003-05-01

    We have developed a new method of imaging the mechanical properties of tissues based on very brief (<1msec) and localized applications of acoustic radiation force and the ultrasonic measurement of local tissues' responses to that force. Initial results with this technique demonstrate its ability to image mechanical properties of the medial and adventitial layers within ex vivo and in vivo arteries, and to distinguish hard and soft atherosclerotic plaques from normal vessel wall. We have labeled this method Acoustic Radiation Force Impulse (ARFI) imaging. We describe studies to utilize this technique in the characterization of diffuse and focal atherosclerosis. We describe phantom trials and finite element simulations which explore the fundamental resolution and contrast achievable with this method. We describe in vivo and ex vivo trials in the popliteal, femoral and brachial arteries to assess the relationship between the mechanical properties of healthy and diseased arteries provided by this method and those obtained by alternative methods.

  18. Cylindrical acoustical holography applied to full-scale jet noise.

    PubMed

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; Krueger, David W; James, Michael M

    2014-09-01

    Near-field acoustical holography methods are used to predict sound radiation from an engine installed on a high-performance military fighter aircraft. Cylindrical holography techniques are an efficient approach to measure the large and complex sound fields produced by full-scale jets. It is shown that a ground-based, one-dimensional array of microphones can be used in conjunction with a cylindrical wave function field representation to provide a holographic reconstruction of the radiated sound field at low frequencies. In the current work, partial field decomposition methods and numerical extrapolation of data beyond the boundaries of the hologram aperture are required prior to holographic projection. Predicted jet noise source distributions and directionality are shown for four frequencies between 63 and 250 Hz. It is shown that the source distribution narrows and moves upstream, and that radiation directionality shifts toward the forward direction, with increasing frequency. A double-lobe feature of full-scale jet radiation is also demonstrated.

  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. Optical and opto-acoustic imaging.

    PubMed

    Ntziachristos, Vasilis; Razansky, Daniel

    2013-01-01

     Since the inception of the microscope, optical imaging is serving the biological discovery for more than four centuries. With the recent emergence of methods appropriate for in vivo staining, such as bioluminescence, fluorescent molecular probes, and proteins, as well as nanoparticle-based targeted agents, significant attention has been shifted toward in vivo interrogations of different dynamic biological processes at the molecular level. This progress has been largely supported by the development of advanced optical tomographic imaging technologies suitable for obtaining volumetric visualization of biomarker distributions in small animals at a whole-body or whole-organ scale, an imaging frontier that is not accessible by the existing tissue-sectioning microscopic techniques due to intensive light scattering beyond the depth of a few hundred microns. Biomedical optoacoustics has also emerged in the recent decade as a powerful tool for high-resolution visualization of optical contrast, overcoming a variety of longstanding limitations imposed by light scattering in deep tissues. By detecting tiny sound vibrations, resulting from selective absorption of light at multiple wavelengths, multispectral optoacoustic tomography methods can now "hear color" in three dimensions, i.e., deliver volumetric spectrally enriched (color) images from deep living tissues at high spatial resolution and in real time. These new-found imaging abilities directly relate to preclinical screening applications in animal models and are foreseen to significantly impact clinical decision making as well.

  1. 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.

  2. Image reconstruction with acoustic radiation force induced shear waves

    NASA Astrophysics Data System (ADS)

    McAleavey, Stephen A.; Nightingale, Kathryn R.; Stutz, Deborah L.; Hsu, Stephen J.; Trahey, Gregg E.

    2003-05-01

    Acoustic radiation force may be used to induce localized displacements within tissue. This phenomenon is used in Acoustic Radiation Force Impulse Imaging (ARFI), where short bursts of ultrasound deliver an impulsive force to a small region. The application of this transient force launches shear waves which propagate normally to the ultrasound beam axis. Measurements of the displacements induced by the propagating shear wave allow reconstruction of the local shear modulus, by wave tracking and inversion techniques. Here we present in vitro, ex vivo and in vivo measurements and images of shear modulus. Data were obtained with a single transducer, a conventional ultrasound scanner and specialized pulse sequences. Young's modulus values of 4 kPa, 13 kPa and 14 kPa were observed for fat, breast fibroadenoma, and skin. Shear modulus anisotropy in beef muscle was observed.

  3. Heavy-Ion Imaging Applied To Medicine

    NASA Astrophysics Data System (ADS)

    Fabrikant, J. I.; Tobias, C. A.; Capp, M. P.; Benton, E. V.; Holley, W. R.

    1980-08-01

    Heavy particle radiography is a newly developed noninvasive low dose imaging procedure with increased resolution of minute density differences in soft tissues of the body. The method utilizes accelerated high energy ions, primarily carbon and neon, at the BEVALAC accelerator at the Lawrence Berkeley Laboratory. The research program applied to medicine utilizes heavy-ion radiography for low dose mammography, for treatment planning for cancer patients, and for imaging and accurate densitometry of skeletal structures and brain and spinal neoplasms. The presentation will be illustrated with clinical cases under study. Discussion will include the potential of heavy-ion imaging, and particularly reconstruction tomography, as an adjunct to existing diagnostic imaging procedures in medicine, both for the applications to the diagnosis, management and treatment of clinical cancer in man, but also for the early detection of small soft tissue tumors at low radiation dose.

  4. Photo acoustic imaging: technology, systems and market trends

    NASA Astrophysics Data System (ADS)

    Faucheux, Marc; d'Humières, Benoît; Cochard, Jacques

    2017-03-01

    Although the Photo Acoustic effect was observed by Graham Bell in 1880, the first applications (gas analysis) occurred in 1970's using the required energetic light pulses from lasers. During mid 1990's medical imaging research begun to use Photo Acoustic effect and in vivo images were obtained in mid-2000. Since 2009, the number of patent related to Photo Acoustic Imaging (PAI) has dramatically increased. PAI machines for pre-clinical and small animal imaging have been being used in a routine way for several years. Based on its very interesting features (non-ionizing radiation, noninvasive, high depth resolution ratio, scalability, moderate price) and because it is able to deliver not only anatomical, but functional and molecular information, PAI is a very promising clinical imaging modality. It penetrates deeper into tissue than OCT (Optical Coherence Tomography) and provides a higher resolution than ultrasounds. The PAI is one of the most growing imaging modality and some innovative clinical systems are planned to be on market in 2017. Our study analyzes the different approaches such as photoacoustic computed tomography, 3D photoacoustic microscopy, multispectral photoacoustic tomography and endoscopy with the recent and tremendous technological progress over the past decade: advances in image reconstruction algorithms, laser technology, ultrasound detectors and miniaturization. We analyze which medical domains and applications are the most concerned and explain what should be the forthcoming medical system in the near future. We segment the market in four parts: Components and R&D, pre-clinical, analytics, clinical. We analyzed what should be, quantitatively and qualitatively, the PAI medical markets in each segment and its main trends. We point out the market accessibility (patents, regulations, clinical evaluations, clinical acceptance, funding). In conclusion, we explain the main market drivers and challenges to overcome and give a road map for medical

  5. 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.

  6. Synchronized imaging and acoustic analysis of the upper airway in patients with sleep-disordered breathing.

    PubMed

    Chang, Yi-Chung; Huon, Leh-Kiong; Pham, Van-Truong; Chen, Yunn-Jy; Jiang, Sun-Fen; Shih, Tiffany Ting-Fang; Tran, Thi-Thao; Wang, Yung-Hung; Lin, Chen; Tsao, Jenho; Lo, Men-Tzung; Wang, Pa-Chun

    2014-12-01

    Progressive narrowing of the upper airway increases airflow resistance and can produce snoring sounds and apnea/hypopnea events associated with sleep-disordered breathing due to airway collapse. Recent studies have shown that acoustic properties during snoring can be altered with anatomic changes at the site of obstruction. To evaluate the instantaneous association between acoustic features of snoring and the anatomic sites of obstruction, a novel method was developed and applied in nine patients to extract the snoring sounds during sleep while performing dynamic magnetic resonance imaging (MRI). The degree of airway narrowing during the snoring events was then quantified by the collapse index (ratio of airway diameter preceding and during the events) and correlated with the synchronized acoustic features. A total of 201 snoring events (102 pure retropalatal and 99 combined retropalatal and retroglossal events) were recorded, and the collapse index as well as the soft tissue vibration time were significantly different between pure retropalatal (collapse index, 2 ± 11%; vibration time, 0.2 ± 0.3 s) and combined (retropalatal and retroglossal) snores (collapse index, 13 ± 7% [P ≤ 0.0001]; vibration time, 1.2 ± 0.7 s [P ≤ 0.0001]). The synchronized dynamic MRI and acoustic recordings successfully characterized the sites of obstruction and established the dynamic relationship between the anatomic site of obstruction and snoring acoustics.

  7. Automatic segmentation applied to obstetric images

    NASA Astrophysics Data System (ADS)

    Vuwong, Vanee; Hiller, John B.; Jin, Jesse S.

    1998-06-01

    This paper presents a shape-based approach for searching and extracting fetal skull boundaries from an obstetric image. The proposed method relies on two major steps. Firstly, we apply the reference axes to scan the image for all potential skull boundaries. The possible skull boundaries are determined whether they are candidates. The candidate with the highest confident value will be selected as the expected head boundary. Then, the position of the expected head boundary is initialized. Secondly, we refine the initial skull boundary using the fuzzy contour model modified from the active contour basis. This results the continuous and smooth fetal skull boundary that we can use for the medical parameter measurement.

  8. Structural changes and imaging signatures of acoustically sensitive microcapsules under ultrasound.

    PubMed

    Sridhar-Keralapura, Mallika; Thirumalai, Shruthi; Mobed-Miremadi, Maryam

    2013-07-01

    The ultrasound drug delivery field is actively designing new agents that would obviate the problems of just using microbubbles for drug delivery. Microbubbles have very short circulation time (minutes), low payload and large size (2-10μm), all of these aspects are not ideal for systemic drug delivery. However, microbubble carriers provide excellent image contrast and their use for image guidance can be exploited. In this paper, we suggest an alternative approach by developing acoustically sensitive microcapsule reservoirs that have future applications for treating large ischemic tumors through intratumoral therapy. We call these agents Acoustically Sensitized Microcapsules (ASMs) and these are not planned for the circulation. ASMs are very simple in their formulation, robust and reproducible. They have been designed to offer high payload (because of their large size), be acoustically sensitive and reactive (because of the Ultrasound Contrast Agents (UCAs) encapsulated) and mechanically robust for future injections/implantations within tumors. We describe three different aspects - (1) effect of therapeutic ultrasound; (2) mechanical properties and (3) imaging signatures of these agents. Under therapeutic ultrasound, the formation of a cavitational bubble was seen prior to rupture. The time to rupture was size dependent. Size dependency was also seen when measuring mechanical properties of these ASMs. % Alginate and permeability also affected the Young's modulus estimates. For study of imaging signatures of these agents, we show six schemes. For example, with harmonic imaging, tissue phantoms and controls did not generate higher harmonic components. Only ASM phantoms created a harmonic signal, whose sensitivity increased with applied acoustic pressure. Future work includes developing schemes combining both sonication and imaging to help detect ASMs before, during and after release of drug substance.

  9. Acoustical imaging and processing of blood vessel and the related materials using ultrasound Doppler effect.

    PubMed

    Yokobori, A T; Ohkuma, T; Yoshinari, H; Yokobori, T; Ohuchi, H; Mori, S

    1991-01-01

    In the present paper a method is proposed to measure the degree of the degradation of the elasticity in natural blood vessel and the related materials by using ultrasound Doppler effect. It was found that the deformation rate and its acceleration in the radial direction of the blood vessel can be detected by acoustical imaging and processing using this method. These results were proven to correspond to the degree of the degradation of the elasticity, that is, the degree of viscoelasticity in the blood vessel from the wave versus time pattern detected and its simple analysis. This method was applied to predicting the arteriosclerosis of blood vessels of humans by acoustical imaging and processing uninvadedly, as the characteristics of viscoelasticity in blood vessels.

  10. Non-equilibrium plasma jet induced thermo-acoustic resistivity imaging for higher contrast and resolution.

    PubMed

    Guo, Liang; Li, Linbo; Dong, Fanqing; Jiang, Wencong

    2017-08-25

    A thermo-acoustic imaging modality induced by non-equilibrium atmospheric pressure plasma jet is reported. A tiny plasma jet is generated by a fast-rising pulsed dielectric barrier discharge and applied to the surface of the biological tissues. The pulsed conductive current induced by the conductive plasma jet is injected into the biological tissues. The Joule heating inside the tissue stimulates the ultrasound signals effectively. The amplitude of the ultrasound is related to the resistivity of the biological tissues near the contact point and takes the maximum at the certain conductivity of the certain frequency. Accordingly the thermo-acoustic resistivity imaging modality of high contrast and resolution is demonstrated theoretically and experimentally.

  11. Multiple digital watermarking applied to medical imaging.

    PubMed

    Giakoumaki, A; Pavlopoulos, S; Koutsouris, D

    2005-01-01

    Beyond its already established wide range of applications, digital watermarking has recently started to gain a foothold in the healthcare sector. The paper discusses the potential of multiple watermarking to address a number of health information management issues, such as protection of sensitive data, origin and data authentication, image archiving and retrieval. A wavelet-based multiple watermarking scheme focusing on these medical-oriented applications is presented; the scheme allows the physician to define a Region of Interest, whose diagnostic value is explicitly protected throughout the embedding process, since the only additional information inserted therein is for the purpose of integrity control. The rest part of the image casts multiple watermarks conveying the physician's digital signature, patient's sensitive data, and keywords allowing image retrieval. In order to increase data robustness, a form of hybrid coding is applied, which includes repetitive embedding of BCH encoded watermarks.

  12. 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.

  13. Blind deconvolution applied to acoustical systems identification with supporting experimental results

    NASA Astrophysics Data System (ADS)

    Roan, Michael J.; Gramann, Mark R.; Erling, Josh G.; Sibul, Leon H.

    2003-10-01

    Many acoustical applications require the analysis of a signal that is corrupted by an unknown filtering function. Examples arise in the areas of noise or vibration control, room acoustics, structural vibration analysis, and speech processing. Here, the observed signal can be modeled as the convolution of the desired signal with an unknown system impulse response. Blind deconvolution refers to the process of learning the inverse of this unknown impulse response and applying it to the observed signal to remove the filtering effects. Unlike classical deconvolution, which requires prior knowledge of the impulse response, blind deconvolution requires only reasonable prior estimates of the input signal's statistics. The significant contribution of this work lies in experimental verification of a blind deconvolution algorithm in the context of acoustical system identification. Previous experimental work concerning blind deconvolution in acoustics has been minimal, as previous literature concerning blind deconvolution uses computer simulated data. This paper examines experiments involving three classical acoustic systems: driven pipe, driven pipe with open side branch, and driven pipe with Helmholtz resonator side branch. Experimental results confirm that the deconvolution algorithm learns these systems' inverse impulse responses, and that application of these learned inverses removes the effects of the filters.

  14. Image analysis applied to luminescence microscopy

    NASA Astrophysics Data System (ADS)

    Maire, Eric; Lelievre-Berna, Eddy; Fafeur, Veronique; Vandenbunder, Bernard

    1998-04-01

    We have developed a novel approach to study luminescent light emission during migration of living cells by low-light imaging techniques. The equipment consists in an anti-vibration table with a hole for a direct output under the frame of an inverted microscope. The image is directly captured by an ultra low- light level photon-counting camera equipped with an image intensifier coupled by an optical fiber to a CCD sensor. This installation is dedicated to measure in a dynamic manner the effect of SF/HGF (Scatter Factor/Hepatocyte Growth Factor) both on activation of gene promoter elements and on cell motility. Epithelial cells were stably transfected with promoter elements containing Ets transcription factor-binding sites driving a luciferase reporter gene. Luminescent light emitted by individual cells was measured by image analysis. Images of luminescent spots were acquired with a high aperture objective and time exposure of 10 - 30 min in photon-counting mode. The sensitivity of the camera was adjusted to a high value which required the use of a segmentation algorithm dedicated to eliminate the background noise. Hence, image segmentation and treatments by mathematical morphology were particularly indicated in these experimental conditions. In order to estimate the orientation of cells during their migration, we used a dedicated skeleton algorithm applied to the oblong spots of variable intensities emitted by the cells. Kinetic changes of luminescent sources, distance and speed of migration were recorded and then correlated with cellular morphological changes for each spot. Our results highlight the usefulness of the mathematical morphology to quantify kinetic changes in luminescence microscopy.

  15. KAIRUAIN-algorithm applied on electromagnetic imaging

    NASA Astrophysics Data System (ADS)

    Lakhal, A.

    2013-09-01

    For time-harmonic Maxwell equations, we consider an inverse scattering problem for the 3D imaging of the constitutive material of an unknown object from the boundary measurements of the electric field. This problem is ill-posed and nonlinear. We introduce the KAIRUAIN-algorithm which is an iterative method of Newton-Kaczmarz type, where we use the approximate inverse for regularizing the solution of the linearized equation at each Newton iteration. We study the convergence of the algorithm and develop a strategy for the choice of the regularizing parameter in a quite general setting. We apply the KAIRUAIN-algorithm to derive an efficient and stable reconstruction method for electromagnetic imaging. We use experimental data provided by the Institut Fresnel, France, to validate the capability of the reconstruction algorithm to retrieve blindly, without any a priori information, the geometry and the dielectric permittivity of the scattering object.

  16. 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

  17. Hot Stuff? Thermal Imaging Applied to Cryocrystallography

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2004-01-01

    In the past we have used thermal imaging techniques to visualize the cryocooling processes of macromolecular crystals. From these images it was clear that a cold wave progresses through a crystal starting at the face closest to the origin of the cold stream and ending at the point furthest away. During these studies we used large volume crystals, which were clearly distinguished fiom the loop holding them. These large crystals, originally grown for neutron diffiaction studies, were chosen deliberately to enhance the imaging. As an extension to this work, we present used thermal imaging to study small crystals, held in a cryo-loop, in the presence of vitrified mother liquor. The different d a r e d transmission and reflectance properties of the crystal in comparison to the mother liquor surrounding it are thought to be the parameter that produces the contrast that makes the crystal visible. An application of this technology may be the determination of the exact location of small crystals in a cryo-loop. Data fkom initial tests in support of application development was recorded for lysozyme crystals and for bFGF/dna complex crystals, which were cryocooled and imaged in large loops, both with visible light mad with h i k e d rdi&tion. The crystals were clearly distinguished from the vitrified solution in the infiared spectrum, while in the case of the bFGF/dna complex the illumination had to be carefully manipulated to make the crystal visible in the visible spectrum. These results suggest that the thermal imaging may be more sensitive than visual imaging for automated location of small crystals. However, further work on small crystals robotically mounted at SSRL did not clearly visualize those crystals. The depth of field of the camera proved to be limiting and a different cooling geometry was used, compared to the previous, successful experiments. Analysis to exploit multiple images to improve depth of field and experimental work to understand cooling geometry

  18. Hot Stuff? Thermal Imaging Applied to Cryocrystallography

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2004-01-01

    In the past we have used thermal imaging techniques to visualize the cryocooling processes of macromolecular crystals. From these images it was clear that a cold wave progresses through a crystal starting at the face closest to the origin of the cold stream and ending at the point furthest away. During these studies we used large volume crystals, which were clearly distinguished fiom the loop holding them. These large crystals, originally grown for neutron diffiaction studies, were chosen deliberately to enhance the imaging. As an extension to this work, we present used thermal imaging to study small crystals, held in a cryo-loop, in the presence of vitrified mother liquor. The different d a r e d transmission and reflectance properties of the crystal in comparison to the mother liquor surrounding it are thought to be the parameter that produces the contrast that makes the crystal visible. An application of this technology may be the determination of the exact location of small crystals in a cryo-loop. Data fkom initial tests in support of application development was recorded for lysozyme crystals and for bFGF/dna complex crystals, which were cryocooled and imaged in large loops, both with visible light mad with h i k e d rdi&tion. The crystals were clearly distinguished from the vitrified solution in the infiared spectrum, while in the case of the bFGF/dna complex the illumination had to be carefully manipulated to make the crystal visible in the visible spectrum. These results suggest that the thermal imaging may be more sensitive than visual imaging for automated location of small crystals. However, further work on small crystals robotically mounted at SSRL did not clearly visualize those crystals. The depth of field of the camera proved to be limiting and a different cooling geometry was used, compared to the previous, successful experiments. Analysis to exploit multiple images to improve depth of field and experimental work to understand cooling geometry

  19. Mutual conversion between B-mode image and acoustic impedance image

    NASA Astrophysics Data System (ADS)

    Chean, Tan Wei; Hozumi, Naohiro; Yoshida, Sachiko; Kobayashi, Kazuto; Ogura, Yuki

    2017-07-01

    To study the acoustic properties of a B-mode image, two ways of analysis methods were proposed in this report. The first method is the conversion of an acoustic impedance image into a B-mode image (Z to B). The time domain reflectometry theory and transmission line model were used as reference in the calculation. The second method is the direct a conversion of B-mode image into an acoustic impedance image (B to Z). The theoretical background of the second method is similar to that of the first method; however, the calculation is in the opposite direction. Significant scatter, refraction, and attenuation were assumed not to take place during the propagation of an ultrasonic wave. Hence, they were ignored in both calculations. In this study, rat cerebellar tissue and human cheek skin were used to determine the feasibility of the first and second methods respectively. Some good results are obtained and hence both methods showed their possible applications in the study of acoustic properties of B-mode images.

  20. 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

  1. 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.

  2. 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

  3. Hyperspectral imaging applied to forensic medicine

    NASA Astrophysics Data System (ADS)

    Malkoff, Donald B.; Oliver, William R.

    2000-03-01

    Remote sensing techniques now include the use of hyperspectral infrared imaging sensors covering the mid-and- long wave regions of the spectrum. They have found use in military surveillance applications due to their capability for detection and classification of a large variety of both naturally occurring and man-made substances. The images they produce reveal the spatial distributions of spectral patterns that reflect differences in material temperature, texture, and composition. A program is proposed for demonstrating proof-of-concept in using a portable sensor of this type for crime scene investigations. It is anticipated to be useful in discovering and documenting the affects of trauma and/or naturally occurring illnesses, as well as detecting blood spills, tire patterns, toxic chemicals, skin injection sites, blunt traumas to the body, fluid accumulations, congenital biochemical defects, and a host of other conditions and diseases. This approach can significantly enhance capabilities for determining the circumstances of death. Potential users include law enforcement organizations (police, FBI, CIA), medical examiners, hospitals/emergency rooms, and medical laboratories. Many of the image analysis algorithms already in place for hyperspectral remote sensing and crime scene investigations can be applied to the interpretation of data obtained in this program.

  4. 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

  5. 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.

  6. 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.

  7. A review of acoustic dampers applied to combustion chambers in aerospace industry

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Li, X. Y.

    2015-04-01

    In engine combustion systems such as rockets, aero-engines and gas turbines, pressure fluctuations are always present, even during normal operation. One of design prerequisites for the engine combustors is stable operation, since large-amplitude self-sustained pressure fluctuations (also known as combustion instability) have the potential to cause serious structural damage and catastrophic engine failure. To dampen pressure fluctuations and to reduce noise, acoustic dampers are widely applied as a passive control means to stabilize combustion/engine systems. However, they cannot respond to the dynamic changes of operating conditions and tend to be effective over certain narrow range of frequencies. To maintain their optimum damping performance over a broad frequency range, extensive researches have been conducted during the past four decades. The present work is to summarize the status, challenges and progress of implementing such acoustic dampers on engine systems. The damping effect and mechanism of various acoustic dampers, such as Helmholtz resonators, perforated liners, baffles, half- and quarter-wave tube are introduced first. A summary of numerical, experimental and theoretical studies are then presented to review the progress made so far. Finally, as an alternative means, ';tunable acoustic dampers' are discussed. Potential, challenges and issues associated with the dampers practical implementation are highlighted.

  8. Echo planar imaging at 4 Tesla with minimum acoustic noise.

    PubMed

    Tomasi, Dardo G; Ernst, Thomas

    2003-07-01

    To minimize the acoustic sound pressure levels of single-shot echo planar imaging (EPI) acquisitions on high magnetic field MRI scanners. The resonance frequencies of gradient coil vibrations, which depend on the coil length and the elastic properties of the materials in the coil assembly, were measured using piezoelectric transducers. The frequency of the EPI-readout train was adjusted to avoid the frequency ranges of mechanical resonances. Our MRI system exhibited two sharp mechanical resonances (at 720 and 1220 Hz) that can increase vibrational amplitudes up to six-fold. A small adjustment of the EPI-readout frequency made it possible to reduce the sound pressure level of EPI-based perfusion and functional MRI scans by 12 dB. Normal vibrational modes of MRI gradient coils can dramatically increase the sound pressure levels during echo planar imaging (EPI) scans. To minimize acoustic noise, the frequency of EPI-readout trains and the resonance frequencies of gradient coil vibrations need to be different. Copyright 2003 Wiley-Liss, Inc.

  9. From Acoustic Segmentation to Language Processing: Evidence from Optical Imaging

    PubMed Central

    Obrig, Hellmuth; Rossi, Sonja; Telkemeyer, Silke; Wartenburger, Isabell

    2010-01-01

    During language acquisition in infancy and when learning a foreign language, the segmentation of the auditory stream into words and phrases is a complex process. Intuitively, learners use “anchors” to segment the acoustic speech stream into meaningful units like words and phrases. Regularities on a segmental (e.g., phonological) or suprasegmental (e.g., prosodic) level can provide such anchors. Regarding the neuronal processing of these two kinds of linguistic cues a left-hemispheric dominance for segmental and a right-hemispheric bias for suprasegmental information has been reported in adults. Though lateralization is common in a number of higher cognitive functions, its prominence in language may also be a key to understanding the rapid emergence of the language network in infants and the ease at which we master our language in adulthood. One question here is whether the hemispheric lateralization is driven by linguistic input per se or whether non-linguistic, especially acoustic factors, “guide” the lateralization process. Methodologically, functional magnetic resonance imaging provides unsurpassed anatomical detail for such an enquiry. However, instrumental noise, experimental constraints and interference with EEG assessment limit its applicability, pointedly in infants and also when investigating the link between auditory and linguistic processing. Optical methods have the potential to fill this gap. Here we review a number of recent studies using optical imaging to investigate hemispheric differences during segmentation and basic auditory feature analysis in language development. PMID:20725516

  10. Imaging of contact acoustic nonlinearity using synthetic aperture technique.

    PubMed

    Yun, Dongseok; Kim, Jongbeom; Jhang, Kyung-Young

    2013-09-01

    The angle beam incidence and reflection technique for the evaluation of contact acoustic nonlinearity (CAN) at solid-solid contact interfaces (e.g., closed cracks) has recently been developed to overcome the disadvantage of accessing both the inner and outer surfaces of structures for attaching pulsing and receiving transducers in the through-transmission of normal incidence technique. This paper proposes a technique for B-mode imaging of CAN based on the above reflection technique, which uses the synthetic aperture focusing technique (SAFT) and short-time Fourier transform (STFT) to visualize the distribution of the CAN-induced second harmonic magnitude as well as the nonlinear parameter. In order to verify the usefulness of the proposed method, a solid-solid contact interface was tested and the change of the contact acoustic nonlinearity according to the increasing contact pressure was visualized in images of the second harmonic magnitude and the relative nonlinear parameter. The experimental results showed good agreement with the previously developed theory identifying the dependence of the scattered second harmonics on the contact pressure. This technique can be used for the detection and improvement of the sizing accuracy of closed cracks that are difficult to detect using the conventional linear ultrasonic technique.

  11. Respiratory acoustic thoracic imaging (RATHI): assessing intrasubject variability.

    PubMed

    Torres-Jimenez, A; Charleston-Villalobos, S; Gonzalez-Camarena, R; Chi-Lem, G; Aljama-Corrales, T

    2008-01-01

    Respiratory acoustic thoracic imaging (RATHI) permits analysing lung sounds (LS) temporal and spatial distribution, however, a deep understanding of RATHI repeatability associated with the pulmonary function is necessary. As a consequence, in the current work intrasubject variability of RATHI is evaluated at different airflows. For generating RATHIs, LS were acquired at the posterior thoracic surface. The associated image was computed at the inspiratory phases by interpolation through a Hermite function. The acoustic information of eleven subjects was considered at airflows of 1.0, 1.5 and 2.0 L/s. Several RATHIs were generated for each subject according to the number of acquired inspiratory phases. Quadratic mutual information based on Cauchy-Schwartz inequality (I(CS)) was used to evaluate the degree of similitude between intrasubject RATHIs. The results indicated that, for the same subject, I(CS) averaged 0.893, 0.897, and 0.902, for airflows of 1.0, 1.5, and 2 L/s, respectively. In addition, when the airflow was increased, increments in intensity values and in the dispersion of the spatial distribution reflected in RATHI were observed. In conclusion, since the intrasubject variability of RATHI was low for airflows between 1.0 and 2.0 L/s, the pattern of sound distribution during airflow variations is repeatable but differences in sound intensity should be considered.

  12. 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.

  13. Long range acoustic imaging of the continental shelf environment: the Acoustic Clutter Reconnaissance Experiment 2001.

    PubMed

    Ratilal, Purnima; Lai, Yisan; Symonds, Deanelle T; Ruhlmann, Lilimar A; Preston, John R; Scheer, Edward K; Garr, Michael T; Holland, Charles W; Goff, John A; Makris, Nicholas C

    2005-04-01

    An active sonar system is used to image wide areas of the continental shelf environment by long-range echo sounding at low frequency. The bistatic system, deployed in the STRATAFORM area south of Long Island in April-May of 2001, imaged a large number of prominent clutter events over ranges spanning tens of kilometers in near real time. Roughly 3000 waveforms were transmitted into the water column. Wide-area acoustic images of the ocean environment were generated in near real time for each transmission. Between roughly 10 to more than 100 discrete and localized scatterers were registered for each image. This amounts to a total of at least 30000 scattering events that could be confused with those from submerged vehicles over the period of the experiment. Bathymetric relief in the STRATAFORM area is extremely benign, with slopes typically less than 0.5 degrees according to high resolution (30 m sampled) bathymetric data. Most of the clutter occurs in regions where the bathymetry is locally level and does not coregister with seafloor features. No statistically significant difference is found in the frequency of occurrence per unit area of repeatable clutter inside versus outside of areas occupied by subsurface river channels.

  14. Quantifying Image Quality Improvement Using Elevated Acoustic Output in B-Mode Harmonic Imaging.

    PubMed

    Deng, Yufeng; Palmeri, Mark L; Rouze, Ned C; Trahey, Gregg E; Haystead, Clare M; Nightingale, Kathryn R

    2017-10-01

    Tissue harmonic imaging has been widely used in abdominal imaging because of its significant reduction in acoustic noise compared with fundamental imaging. However, tissue harmonic imaging can be limited by both signal-to-noise ratio and penetration depth during clinical imaging, resulting in decreased diagnostic utility. A logical approach would be to increase the source pressure, but the in situ pressures used in diagnostic ultrasound are subject to a de facto upper limit based on the U.S. Food and Drug Administration guideline for the mechanical index (<1.9). A recent American Institute of Ultrasound in Medicine report concluded that an effective mechanical index ≤4.0 could be warranted without concern for increased risk of cavitation in non-fetal tissues without gas bodies, but would only be justified if there were a concurrent improvement in image quality and diagnostic utility. This work evaluates image quality differences between normal and elevated acoustic output hepatic harmonic imaging using a transmit frequency of 1.8 MHz. The results indicate that harmonic imaging using elevated acoustic output leads to modest improvements (3%-7%) in contrast-to-noise ratio of hypo-echoic hepatic vessels and increases in imaging penetration depth on the order of 4 mm per mechanical index increase of 0.1 for a given focal depth. Difficult-to-image patients who suffer from poor ultrasound image quality exhibited larger improvements than easy-to-image study participants. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  15. Fast transforms for acoustic imaging--part II: applications.

    PubMed

    Ribeiro, Flávio P; Nascimento, Vítor H

    2011-08-01

    In Part I ["Fast Transforms for Acoustic Imaging-Part I: Theory," IEEE Transactions on Image Processing], we introduced the Kronecker array transform (KAT), a fast transform for imaging with separable arrays. Given a source distribution, the KAT produces the spectral matrix which would be measured by a separable sensor array. In Part II, we establish connections between the KAT, beamforming and 2-D convolutions, and show how these results can be used to accelerate classical and state of the art array imaging algorithms. We also propose using the KAT to accelerate general purpose regularized least-squares solvers. Using this approach, we avoid ill-conditioned deconvolution steps and obtain more accurate reconstructions than previously possible, while maintaining low computational costs. We also show how the KAT performs when imaging near-field source distributions, and illustrate the trade-off between accuracy and computational complexity. Finally, we show that separable designs can deliver accuracy competitive with multi-arm logarithmic spiral geometries, while having the computational advantages of the KAT.

  16. 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.

  17. Combining passive acoustics and imaging sonar techniques to study sperm whales' foraging strategies.

    PubMed

    Giorli, Giacomo; Au, Whitlow W L

    2017-09-01

    Sperm whales forage in the deep ocean, hunting for squid. An innovative approach for the study of sperm whale foraging behavior and habitat selection is reported in this letter. A DIDSON imaging sonar mounted on a profiler with a conductivity, temperature, and depth sensor was used to count and measure potential prey in the deep ocean during sperm whales' acoustical foraging encounters in Hawaii. Preliminary results show how this technique can be applied to the study of deep diving whale foraging and habitat selection. Sperm whales foraged where the density of prey decreased with depth and where the size of prey increased with depth.

  18. Comparison of sonochemiluminescence images using image analysis techniques and identification of acoustic pressure fields via simulation.

    PubMed

    Tiong, T Joyce; Chandesa, Tissa; Yap, Yeow Hong

    2017-05-01

    One common method to determine the existence of cavitational activity in power ultrasonics systems is by capturing images of sonoluminescence (SL) or sonochemiluminescence (SCL) in a dark environment. Conventionally, the light emitted from SL or SCL was detected based on the number of photons. Though this method is effective, it could not identify the sonochemical zones of an ultrasonic systems. SL/SCL images, on the other hand, enable identification of 'active' sonochemical zones. However, these images often provide just qualitative data as the harvesting of light intensity data from the images is tedious and require high resolution images. In this work, we propose a new image analysis technique using pseudo-colouring images to quantify the SCL zones based on the intensities of the SCL images and followed by comparison of the active SCL zones with COMSOL simulated acoustic pressure zones.

  19. Magneto-thermal-acoustic differential-frequency imaging of magnetic nanoparticle with magnetic spatial localization: a theoretical prediction

    NASA Astrophysics Data System (ADS)

    Piao, Daqing

    2017-02-01

    The magneto-thermo-acoustic effect that we predicted in 2013 refers to the generation of acoustic-pressure wave from magnetic nanoparticle (MNP) when thermally mediated under an alternating magnetic field (AMF) at a pulsed or frequency-chirped application. Several independent experimental studies have since validated magneto-thermoacoustic effect, and a latest report has discovered acoustic-wave generation from MNP at the second-harmonic frequency of the AMF when operating continuously. We propose that applying two AMFs with differing frequencies to MNP will produce acoustic-pressure wave at the summation and difference of the two frequencies, in addition to the two second-harmonic frequencies. Analysis of the specific absorption dynamics of the MNP when exposed to two AMFs of differing frequencies has shown some interesting patterns of acoustic-intensity at the multiple frequency components. The ratio of the acoustic-intensity at the summation-frequency over that of the difference-frequency is determined by the frequency-ratio of the two AMFs, but remains independent of the AMF strengths. The ratio of the acoustic-intensity at the summation- or difference-frequency over that at each of the two second-harmonic frequencies is determined by both the frequency-ratio and the field-strength-ratio of the two AMFs. The results indicate a potential strategy for localization of the source of a continuous-wave magneto-thermalacoustic signal by examining the frequency spectrum of full-field non-differentiating acoustic detection, with the field-strength ratio changed continuously at a fixed frequency-ratio. The practicalities and challenges of this magnetic spatial localization approach for magneto-thermo-acoustic imaging using a simple envisioned set of two AMFs arranged in parallel to each other are discussed.

  20. Quantitative enhancement of fatigue crack monitoring by imaging surface acoustic wave reflection in a space-cycle-load domain

    SciTech Connect

    Connolly, G. D.; Rokhlin, S. I.

    2011-06-23

    The surface wave acoustic method is applied to the in-situ monitoring of fatigue crack initiation and evolution on tension specimens. A small low-frequency periodic loading is also applied, resulting in a nonlinear modulation of reflected pulses. The acoustic wave reflections are collected for: each experimental cycle; a range of applied tension and modulation load levels; and a range of spatial propagation positions, and are presented in image form to aid pattern identification. Salient features of the image are then extracted and processed to evaluate the initiation time of the crack and its subsequent size evolution until sample failure. Additionally, a method for enhancing signal to noise ratio in Ti-6242 alloy samples is demonstrated.

  1. Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations.

    PubMed

    Hagsäter, S M; Jensen, T Glasdam; Bruus, H; Kutter, J P

    2007-10-01

    We show that full-image micro-PIV analysis in combination with images of transient particle motion is a powerful tool for experimental studies of acoustic radiation forces and acoustic streaming in microfluidic chambers under piezo-actuation in the MHz range. The measured steady-state motion of both large 5 microm and small 1 microm particles can be understood in terms of the acoustic eigenmodes or standing ultra-sound waves in the given experimental microsystems. This interpretation is supported by numerical solutions of the corresponding acoustic wave equation.

  2. 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

  3. Acoustic sources of opportunity in the marine environment - Applied to source localization and ocean sensing

    NASA Astrophysics Data System (ADS)

    Verlinden, Christopher M.

    Controlled acoustic sources have typically been used for imaging the ocean. These sources can either be used to locate objects or characterize the ocean environment. The processing involves signal extraction in the presence of ambient noise, with shipping being a major component of the latter. With the advent of the Automatic Identification System (AIS) which provides accurate locations of all large commercial vessels, these major noise sources can be converted from nuisance to beacons or sources of opportunity for the purpose of studying the ocean. The source localization method presented here is similar to traditional matched field processing, but differs in that libraries of data-derived measured replicas are used in place of modeled replicas. In order to account for differing source spectra between library and target vessels, cross-correlation functions are compared instead of comparing acoustic signals directly. The library of measured cross-correlation function replicas is extrapolated using waveguide invariant theory to fill gaps between ship tracks, fully populating the search grid with estimated replicas allowing for continuous tracking. In addition to source localization, two ocean sensing techniques are discussed in this dissertation. The feasibility of estimating ocean sound speed and temperature structure, using ship noise across a drifting volumetric array of hydrophones suspended beneath buoys, in a shallow water marine environment is investigated. Using the attenuation of acoustic energy along eigenray paths to invert for ocean properties such as temperature, salinity, and pH is also explored. In each of these cases, the theory is developed, tested using numerical simulations, and validated with data from acoustic field experiments.

  4. Standing tree decay detection by using acoustic tomography images

    NASA Astrophysics Data System (ADS)

    Espinosa, Luis F.; Arciniegas, Andres F.; Prieto, Flavio A.; Cortes, Yolima; Brancheriau, Loïc.

    2015-04-01

    The acoustic tomographic technique is used in the diagnosis process of standing trees. This paper presents a segmentation methodology to separate defective regions in cross-section tomographic images obtained with Arbotom® device. A set of experiments was proposed using two trunk samples obtained from a eucalyptus tree, simulating defects by drilling holes with known geometry, size and position and using different number of sensors. Also, tomographic images from trees presenting real defects were studied, by testing two different species with significant internal decay. Tomographic images and photographs from the trunk cross-section were processed to align the propagation velocity data with a corresponding region, healthy or defective. The segmentation was performed by finding a velocity threshold value to separate the defective region; a logistic regression model was fitted to obtain the value that maximizes a performance criterion, being selected the geometric mean. Accuracy segmentation values increased as the number of sensors augmented; also the position influenced the result, obtaining improved results in the case of centric defects.

  5. 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

  6. Acoustic-integrated dynamic MR imaging for a patient with obstructive sleep apnea.

    PubMed

    Chen, Yunn-Jy; Shih, Tiffany Ting-Fang; Chang, Yi-Chung; Hsu, Ying-Chieh; Huon, Leh-Kiong; Lo, Men-Tzung; Pham, Van-Truong; Lin, Chen; Wang, Pa-Chun

    2015-12-01

    Obstructive sleep apnea syndrome (OSAS) is caused by multi-level upper airway obstruction. Anatomic changes at the sites of obstruction may modify the physical or acoustic properties of snores. The surgical success of OSA depends upon precise localization of obstructed levels. We present a case of OSAS who received simultaneous dynamic MRI and snore acoustic recordings. The synchronized image and acoustic information successfully characterize the sites of temporal obstruction during sleep-disordered breathing events.

  7. Bessel filters applied in biomedical image processing

    NASA Astrophysics Data System (ADS)

    Mesa Lopez, Juan Pablo; Castañeda Saldarriaga, Diego Leon

    2014-06-01

    A magnetic resonance is an image obtained by means of an imaging test that uses magnets and radio waves to create body images, however, in some images it's difficult to recognize organs or foreign agents present in the body. With these Bessel filters the objective is to significantly increase the resolution of magnetic resonance images taken to make them much clearer in order to detect anomalies and diagnose the illness. As it's known, Bessel filters appear to solve the Schrödinger equation for a particle enclosed in a cylinder and affect the image distorting the colors and contours of it, therein lies the effectiveness of these filters, since the clear outline shows more defined and easy to recognize abnormalities inside the body.

  8. OSA Imaging and Applied Optics Congress Support

    DTIC Science & Technology

    2017-02-16

    and Computational Optical Sensing and Imaging (COSI) .The meetings exposed attendees to in-depth learning of optical sensing and imaging and their...were supported by this grant. The meetings exposed attendees to in-depth learning of optical sensing and imaging and their applications from...Participants can hear about the latest products and services, but more importantly, learn about entrepreneurial opportunities and how scientific

  9. Subsurface defect of amorphous carbon film imaged by near field acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Zeng, J. T.; Zhao, K. Y.; Zeng, H. R.; Song, H. Z.; Zheng, L. Y.; Li, G. R.; Yin, Q. R.

    2008-05-01

    Amorphous carbon films were examined by low frequency scanning-probe acoustic microscopy (LF-SPAM). Local elastic properties as well as topography were imaged in the acoustic mode. Two kinds of subsurface defects were revealed by the LF-SPAM method. The influence of the subsurface defects on the elastic properties was also discussed. The ability to image subsurface defects was dependent on the scan area and the scan speed. Our results showed that the low frequency scanning-probe acoustic microscopy is a useful method for imaging subsurface defects with high resolution.

  10. Platforms for hyperspectral imaging, in-situ optical and acoustical imaging in urbanized regions

    NASA Astrophysics Data System (ADS)

    Bostater, Charles R.; Oney, Taylor

    2016-10-01

    Hyperspectral measurements of the water surface of urban coastal waters are presented. Oblique bidirectional reflectance factor imagery was acquired made in a turbid coastal sub estuary of the Indian River Lagoon, Florida and along coastal surf zone waters of the nearby Atlantic Ocean. Imagery was also collected using a pushbroom hyperspectral imager mounted on a fixed platform with a calibrated circular mechatronic rotation stage. Oblique imagery of the shoreline and subsurface features clearly shows subsurface bottom features and rip current features within the surf zone water column. In-situ hyperspectral optical signatures were acquired from a vessel as a function of depth to determine the attenuation spectrum in Palm Bay. A unique stationary platform methodology to acquire subsurface acoustic images showing the presence of moving bottom boundary nephelometric layers passing through the acoustic fan beam. The acoustic fan beam imagery indicated the presence of oscillatory subsurface waves in the urbanized coastal estuary. Hyperspectral imaging using the fixed platform techniques are being used to collect hyperspectral bidirectional reflectance factor (BRF) measurements from locations at buildings and bridges in order to provide new opportunities to advance our scientific understanding of aquatic environments in urbanized regions.

  11. A transversal substructuring mode matching method applied to the acoustic analysis of dissipative mufflers

    NASA Astrophysics Data System (ADS)

    Albelda, J.; Denia, F. D.; Torres, M. I.; Fuenmayor, F. J.

    2007-06-01

    To carry out the acoustic analysis of dissipative silencers with uniform cross-section, the application of the mode matching method at the geometrical discontinuities is an attractive option from a computational point of view. The consideration of this methodology assumes, in general, that the modes associated with the transversal geometry of each element with uniform cross-section are known for the excitation frequencies considered in the analysis. The calculation of the transversal modes is not, however, a simple task when the acoustic system involves perforated elements and absorbent materials. The current work presents a modal approach to calculate the transversal modes and the corresponding axial wavenumbers for dissipative mufflers of uniform (but arbitrary) cross-section. The proposed technique is based on the division of the transversal section into subdomains and the subsequent use of a substructuring procedure with two sets of modes to improve the convergence. The former set of modes fulfils the condition of zero pressure at the common boundary between transversal subdomains while the latter satisfies the condition of zero derivative in the direction normal to the boundary. The approach leads to a versatile methodology with a moderate computational effort that can be applied to mufflers commonly found in real applications. To validate the procedure presented in this work, comparisons are provided with finite element predictions and results available in the literature, showing a good agreement. In addition, the procedure is applied to an example of practical interest.

  12. Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery

    NASA Astrophysics Data System (ADS)

    Hojman, Eliel; Chaigne, Thomas; Solomon, Oren; Gigan, Sylvain; Bossy, Emmanuel; Eldar, Yonina C.; Katz, Ori

    2017-03-01

    In deep tissue photoacoustic imaging the spatial resolution is inherently limited by the acoustic wavelength. Recently, it was demonstrated that it is possible to surpass the acoustic diffraction limit by analyzing fluctuations in a set of photoacoustic images obtained under unknown speckle illumination patterns. Here, we purpose an approach to boost reconstruction fidelity and resolution, while reducing the number of acquired images by utilizing a compressed sensing computational reconstruction framework. The approach takes into account prior knowledge of the system response and sparsity of the target structure. We provide proof of principle experiments of the approach and demonstrate that improved performance is obtained when both speckle fluctuations and object priors are used. We numerically study the expected performance as a function of the measurements signal to noise ratio and sample spatial-sparsity. The presented reconstruction framework can be applied to analyze existing photoacoustic experimental datasets containing dynamic fluctuations.

  13. Three-dimensional photoacoustic imaging system with a 4f aspherical acoustic lens

    NASA Astrophysics Data System (ADS)

    Jen, En; Lin, Hsintien; Chiang, Huihua Kenny

    2016-08-01

    Photoacoustic (PA) imaging is a modality for achieving high-contrast images of blood vessels or tumors. Most PA imaging systems use complex reconstruction algorithms under conventional linear array transducers. We introduced the optical simulating method to improve the acoustic lens design and obtain a PA imaging system with improved spatial revolution (a 0.5-mm point spread function and a lateral image resolution of more than 1 mm) is realized using a 4f aspherical acoustic lens. The acoustic lens approach improved the image resolution and enabled direct reconstruction of three-dimensional (3-D) PA images. The system demonstrated a lateral resolution of more than 1 mm, a field of view of 8.5 deg, and a depth of focus of 10 mm. The system displays great potential for developing a real-time 3-D PA camera system for biomedical ultrasound imaging applications.

  14. Full-Field Imaging of Acoustic Motion at Nanosecond Time and Micron Length Scales

    SciTech Connect

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

    2002-10-01

    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 employing dynamic holography using photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed capable of operation on the nanosecond time 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 at 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 and performance of these devices. Images of 256x240 pixels are recorded at 18Hz rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level 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.

  15. 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.

  16. Characterizing response to elemental unit of acoustic imaging noise: an FMRI study.

    PubMed

    Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2009-07-01

    Acoustic imaging noise produced during functional magnetic resonance imaging (fMRI) studies can hinder auditory fMRI research analysis by altering the properties of the acquired time-series data. Acoustic imaging noise can be especially confounding when estimating the time course of the hemodynamic response (HDR) in auditory event-related fMRI (fMRI) experiments. This study is motivated by the desire to establish a baseline function that can serve not only as a comparison to other quantities of acoustic imaging noise for determining how detrimental is one's experimental noise, but also as a foundation for a model that compensates for the response to acoustic imaging noise. Therefore, the amplitude and spatial extent of the HDR to the elemental unit of acoustic imaging noise (i.e., a single ping) associated with echoplanar acquisition were characterized and modeled. Results from this fMRI study at 1.5 T indicate that the group-averaged HDR in left and right auditory cortex to acoustic imaging noise (duration of 46 ms) has an estimated peak magnitude of 0.29% (right) to 0.48% (left) signal change from baseline, peaks between 3 and 5 s after stimulus presentation, and returns to baseline and remains within the noise range approximately 8 s after stimulus presentation.

  17. 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.

  18. Acoustic angiography: a new high frequency contrast ultrasound technique for biomedical imaging

    NASA Astrophysics Data System (ADS)

    Shelton, Sarah E.; Lindsey, Brooks D.; Gessner, Ryan; Lee, Yueh; Aylward, Stephen; Lee, Hyunggyun; Cherin, Emmanuel; Foster, F. Stuart; Dayton, Paul A.

    2016-05-01

    Acoustic Angiography is a new approach to high-resolution contrast enhanced ultrasound imaging enabled by ultra-broadband transducer designs. The high frequency imaging technique provides signal separation from tissue which does not produce significant harmonics in the same frequency range, as well as high resolution. This approach enables imaging of microvasculature in-vivo with high resolution and signal to noise, producing images that resemble x-ray angiography. Data shows that acoustic angiography can provide important information about the presence of disease based on vascular patterns, and may enable a new paradigm in medical imaging.

  19. Acoustic teaching apparatus before 1929 at the Case School of Applied Science

    NASA Astrophysics Data System (ADS)

    Hoekje, Peter L.; Fickinger, William

    2004-05-01

    The acoustics apparatus found in the Physics Department of the Case School of Applied Science in the first decades of the 20th century included many items common to other acoustical teaching laboratories, such as organ pipes, tuning forks, Helmholtz resonators, sirens, and manometric flame sound analyzers. The European instrument makers Rudolf Koenig and Max Kohl supplied much of this. Equipment built at Case included the phonodeik, which Dayton C. Miller designed in 1908, and the waveform synthesizer. Miller supplied detailed descriptions of the operations of all this equipment in papers and books. In the phonodeik (to show sound), sound deflects a thin glass diaphragm, which by a silk thread turns a mirror on an axle, causing a spot of light to move across film or a projection screen. A working model of the phonodeik has been reconstructed from pieces of two original ones, and will be demonstrated. Photographs of other extant instruments in the collection, and a selection from Millers lantern slides, will be displayed.

  20. 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.

  1. Photo-Acoustic Ultrasound Imaging to Distinguish Benign from Malignant Prostate Cancer

    DTIC Science & Technology

    2016-09-01

    An ultrasound transducer delivers a pulse of acoustic energy into the area of interest and listens for the echoes which return as the sound waves... ultrasound probe developed in this project (Figure 13C). The images from the IVUS probe are relatively low quality and highly scattering targets...AWARD NUMBER: W81XWH-15-1-0137 TITLE: Photo-Acoustic Ultrasound Imaging to Distinguish Benign from Malignant Prostate Cancer PRINCIPAL

  2. Phase-sensitive imaging of tissue acoustic vibrations using spectrally encoded interferometry.

    PubMed

    Ilgayev, Ovadia; Yelin, Dvir

    2013-08-26

    Acoustic vibrations in tissue are often difficult to image, requiring high-speed scanning, high sensitivity and nanometer-scale axial resolution. Here we use spectrally encoded interferometry to measure the vibration pattern of two-dimensional surfaces, including the skin of a volunteer, at nanometric resolution, without the need for rapid lateral scanning and with no prior knowledge of the driving acoustic waveform. Our results demonstrate the feasibility of this technique for measuring tissue biomechanics using simple and compact imaging probes.

  3. Image quality metrics applied to digital pathology

    NASA Astrophysics Data System (ADS)

    Jiménez, Ana; Bueno, Gloria; Cristóbal, Gabriel; Déniz, Oscar; Toomey, David; Conway, Catherine

    2016-04-01

    Several full-reference and blind metrics from literature have been tested on a set of digitized pathology slides under different known distortion conditions. Those ones showing the most uniform behavior are presented in this paper. Also, an algorithm that provides a blur map of the whole slide images (WSIs) has been implemented based on one of such methods.

  4. Noncontact ultrasound imaging applied to cortical bone phantoms

    PubMed Central

    Bulman, J. B.; Ganezer, K. S.; Halcrow, P. W.; Neeson, Ian

    2012-01-01

    Purpose: The purpose of this paper was to take the first steps toward applying noncontact ultrasound (NCU) to the tasks of monitoring osteoporosis and quantitative ultrasound imaging (QUS) of cortical bone. The authors also focused on the advantages of NCU, such as its lack of reliance on a technologist to apply transducers and a layer of acoustical coupling gel, the ability of the transducers to operate autonomously as specified by preprogrammed software, and the likely reduction in statistical and systematic errors associated with the variability in the pressure applied by the clinician to the transmitting transducer that NCU might provide. The authors also undertook this study in order to find additional applications of NCU beyond its past limited usage in assessing the severity of third degree burns. Methods: A noncontact ultrasound imaging system using a pair of specially designed broadband, 1.5 MHz noncontact piezoelectric transducers and cortical bone phantoms, were used to determine bone mineral density (BMD), speed of sound (SOS), integrated response (IR), and ultrasonic transmittance. Air gaps of greater than 3 cm, two transmission and two reflection paths, and a digital signal processor were also used in the collection of data from phantoms of nominal mass densities that varied from 1.17 to 2.25 g/cm3 and in bone mineral density from 0 to 1.7 g/cm3. Results: Good correlations between known BMD and measured SOS, IR, and transmittance were obtained for all 17 phantoms, and methods for quantifying and minimizing sources of systematic errors were outlined. The BMD of the phantom sets extended through most of the in vivo range found in cortical bone. A total of 16–20 repeated measurements of the SOS, thickness, and IR for the phantom set that were conducted over a period of several months showed a small variation in the range of measurements of ±1%–2%. These NCU data were shown to be in agreement with similar results using contact ultrasound to be within

  5. 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.

  6. Temporal pattern of acoustic imaging noise asymmetrically modulates activation in the auditory cortex

    PubMed Central

    Ranaweera, Ruwan D.; Kwon, Minseok; Hu, Shuowen; Tamer, Gregory G.; Luh, Wen-Ming; Talavage, Thomas M.

    2015-01-01

    This study investigated the hemisphere-specific effects of the temporal pattern of imaging related acoustic noise on auditory cortex activation. Hemodynamic responses (HDRs) to five temporal patterns of imaging noise corresponding to noise generated by unique combinations of imaging volume and effective repetition time (TR), were obtained using a stroboscopic event-related paradigm with extra-long (≥27.5s) TR to minimize inter-acquisition effects. In addition to confirmation that fMRI responses in auditory cortex do not behave in a linear manner, temporal patterns of imaging noise were found to modulate both the shape and spatial extent of hemodynamic responses, with classically non-auditory areas exhibiting responses to longer duration noise conditions. Hemispheric analysis revealed the right primary auditory cortex to be more sensitive than the left to the presence of imaging related acoustic noise. Right primary auditory cortex responses were significantly larger during all the conditions. This asymmetry of response to imaging related acoustic noise could lead to different baseline activation levels during acquisition schemes using short TR, inducing an observed asymmetry in the responses to an intended acoustic stimulus through limitations of dynamic range, rather than due to differences in neuronal processing of the stimulus. These results emphasize the importance of accounting for the temporal pattern of the acoustic noise when comparing findings across different fMRI studies, especially those involving acoustic stimulation. PMID:26519093

  7. Temporal pattern of acoustic imaging noise asymmetrically modulates activation in the auditory cortex.

    PubMed

    Ranaweera, Ruwan D; Kwon, Minseok; Hu, Shuowen; Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2016-01-01

    This study investigated the hemisphere-specific effects of the temporal pattern of imaging related acoustic noise on auditory cortex activation. Hemodynamic responses (HDRs) to five temporal patterns of imaging noise corresponding to noise generated by unique combinations of imaging volume and effective repetition time (TR), were obtained using a stroboscopic event-related paradigm with extra-long (≥27.5 s) TR to minimize inter-acquisition effects. In addition to confirmation that fMRI responses in auditory cortex do not behave in a linear manner, temporal patterns of imaging noise were found to modulate both the shape and spatial extent of hemodynamic responses, with classically non-auditory areas exhibiting responses to longer duration noise conditions. Hemispheric analysis revealed the right primary auditory cortex to be more sensitive than the left to the presence of imaging related acoustic noise. Right primary auditory cortex responses were significantly larger during all the conditions. This asymmetry of response to imaging related acoustic noise could lead to different baseline activation levels during acquisition schemes using short TR, inducing an observed asymmetry in the responses to an intended acoustic stimulus through limitations of dynamic range, rather than due to differences in neuronal processing of the stimulus. These results emphasize the importance of accounting for the temporal pattern of the acoustic noise when comparing findings across different fMRI studies, especially those involving acoustic stimulation. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. Integral transformations applied to image encryption

    NASA Astrophysics Data System (ADS)

    Vilardy, Juan M.; Perez, Ronal; Torres, Cesar O.

    2017-01-01

    In this paper we consider the application of the integral transformations for image encryption through optical systems, a mathematical algorithm under Matlab platform using fractional Fourier transform (FrFT) and Random Phase Mask (RPM) for digital images encryption is implemented. The FrFT can be related to others integral transforms, such as: Fourier transform, Sine and Cosine transforms, Radial Hilbert transform, fractional Sine transform, fractional Cosine transform, fractional Hartley transform, fractional Wavelet transform and Gyrator transform, among other transforms. The encryption scheme is based on the use of the FrFT, the joint transform correlator and two RPMs, which provide security and robustness to the implemented security system. One of the RPMs used during encryption-decryption and the fractional order of the FrFT are the keys to improve security and make the system more resistant against security attacks.

  13. Image segmentation applied to atherosclerotic lesion

    NASA Astrophysics Data System (ADS)

    Morales, R. Rodríguez; Martínez, T. E. Alarcón; Cuello, L. Sánchez; Fernández-Britto, J. E.; Taylor, Charles

    2000-10-01

    The results obtained using two techniques: a supervised method and other unsupervised for image segmentation of atherosclerotic lesions of the thoracic aorta, are presented. Segmentation was used both with and without pre-processing. In this paper, the advantages of pre-processing prior to are shown for discriminating among the different atherosclerotic lesions (fatty streaks, fibrous plaque, complicated plaques and calcified plaques) and identifying them. The results using a supervised method were poor when searching vector consisted of two components, the mean and the variance. This digital image processing was done in order to use the automated atherometric system. This methodology has been considered to be suitable for the characterization of the atherosclerotic lesions in any artery and its organ-related damage in any vascular sector or group of patients. Final results were compared with manual segmentation realized by an expert, where difference errors less than 3% were observed. It is demonstrated by extensive experimentation, using real image data, that proposed strategy is fast and robust in the environment of a personal computer.

  14. 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.

  15. ADRPM-VII applied to the long-range acoustic detection problem

    NASA Technical Reports Server (NTRS)

    Shalis, Edward; Koenig, Gerald

    1990-01-01

    An acoustic detection range prediction model (ADRPM-VII) has been written for IBM PC/AT machines running on the MS-DOS operating system. The software allows the user to predict detection distances of ground combat vehicles and their associated targets when they are involved in quasi-military settings. The program can also calculate individual attenuation losses due to spherical spreading, atmospheric absorption, ground reflection and atmospheric refraction due to temperature and wind gradients while varying parameters effecting the source-receiver problem. The purpose here is to examine the strengths and limitations of ADRPM-VII by modeling the losses due to atmospheric refraction and ground absorption, commonly known as excess attenuation, when applied to the long range detection problem for distances greater than 3 kilometers.

  16. Compressed Sensing Techniques Applied to Ultrasonic Imaging of Cargo Containers.

    PubMed

    López, Yuri Álvarez; Lorenzo, José Ángel Martínez

    2017-01-15

    One of the key issues in the fight against the smuggling of goods has been the development of scanners for cargo inspection. X-ray-based radiographic system scanners are the most developed sensing modality. However, they are costly and use bulky sources that emit hazardous, ionizing radiation. Aiming to improve the probability of threat detection, an ultrasonic-based technique, capable of detecting the footprint of metallic containers or compartments concealed within the metallic structure of the inspected cargo, has been proposed. The system consists of an array of acoustic transceivers that is attached to the metallic structure-under-inspection, creating a guided acoustic Lamb wave. Reflections due to discontinuities are detected in the images, provided by an imaging algorithm. Taking into consideration that the majority of those images are sparse, this contribution analyzes the application of Compressed Sensing (CS) techniques in order to reduce the amount of measurements needed, thus achieving faster scanning, without compromising the detection capabilities of the system. A parametric study of the image quality, as a function of the samples needed in spatial and frequency domains, is presented, as well as the dependence on the sampling pattern. For this purpose, realistic cargo inspection scenarios have been simulated.

  17. Compressed Sensing Techniques Applied to Ultrasonic Imaging of Cargo Containers

    PubMed Central

    Álvarez López, Yuri; Martínez Lorenzo, José Ángel

    2017-01-01

    One of the key issues in the fight against the smuggling of goods has been the development of scanners for cargo inspection. X-ray-based radiographic system scanners are the most developed sensing modality. However, they are costly and use bulky sources that emit hazardous, ionizing radiation. Aiming to improve the probability of threat detection, an ultrasonic-based technique, capable of detecting the footprint of metallic containers or compartments concealed within the metallic structure of the inspected cargo, has been proposed. The system consists of an array of acoustic transceivers that is attached to the metallic structure-under-inspection, creating a guided acoustic Lamb wave. Reflections due to discontinuities are detected in the images, provided by an imaging algorithm. Taking into consideration that the majority of those images are sparse, this contribution analyzes the application of Compressed Sensing (CS) techniques in order to reduce the amount of measurements needed, thus achieving faster scanning, without compromising the detection capabilities of the system. A parametric study of the image quality, as a function of the samples needed in spatial and frequency domains, is presented, as well as the dependence on the sampling pattern. For this purpose, realistic cargo inspection scenarios have been simulated. PMID:28098841

  18. 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.

  19. Applying Zeeman Doppler imaging to solar spectra

    NASA Astrophysics Data System (ADS)

    Hussain, G. A. J.; Saar, S. H.; Collier Cameron, A.

    2004-03-01

    A new generation of spectro-polarimeters with high throughput (e.g. CFHT/ESPADONS and LBT/PEPSI) is becoming available. This opportunity can be exploited using Zeeman Doppler imaging (ZDI), a technique that inverts time-series of Stokes V spectra to map stellar surface magnetic fields (Semel 1989). ZDI is assisted by ``Least squares deconvolution'' (LSD), which sums up the signal from 1000's of photospheric lines to produce a mean deconvolved profile with higher S:N (Donati & Collier Cameron 1997).

  20. SEM imaging of acoustically stimulated charge transport in solids

    NASA Astrophysics Data System (ADS)

    Emelin, Evgeny; Cho, H. D.; Insepov, Zeke; Lee, J. C.; Kang, Tae Won; Panin, Gennady; Roshchupkin, Dmitry; Tynyshtykbayev, Kurbangali

    2017-06-01

    Acoustically stimulated charge transport in solids was studied using the scanning electron microscopy method (SEM). The surface acoustic wave on the surface of the YZ-cut of a LiNbO3 crystal was visualized by registration of low-energy secondary electrons in SEM, and the charge distribution on the crystal surface was visualized using the electron beam induced current method. To register the induced current, an interdigital transducer structure was formed from graphene on the crystal surface. It was shown that the charge distribution on the crystal surface corresponds to the distribution of the acoustic wave field on the crystal surface.

  1. Biosonar acoustic images for target localization and classification by bats

    NASA Astrophysics Data System (ADS)

    Simmons, James A.

    1997-07-01

    Echolocating bats use sonar to guide interception of insects, recognize objects by shape, and even track prey in clutter. Broadcasts of the big brown bat are 0.5 to 20 ms FM signals in the 20-100 kHz ultrasonic band. Insects consist of several reflecting glints, each equivalent in cross- section to a small sphere of 2 mm to 2 cm radius, while clutter is typically composed of numerous glints distributed over a large volume. The bats' signals extend in space for many target lengths, while ka values for each glint are 0.5 to 30 across the broadcast band. Bats perceive acoustic images having echo delay as their primary dimension, and space is perceived in terms of the distribution of target glints in range. Range disparities between the ears provide two 'looks' at each target from slightly different locations as well as information about azimuth. The bats auditory system encodes the FM sweeps of broadcasts and echoes as linear-period spectrograms with integration-times of 300-400 micrometers . Bats nevertheless perceive individual glints in targets for echo-delay separations well inside the integration-time window. Deconvolution is achieved by spectrogram correlation in the time domain and spectral shape transformation in the frequency-domain, with all output evidently being displayed in the time domina. Neural responses in the bat's auditory system seem limited in time precision to 20-50 micrometers at best and 300 microsecond(s) to 3 ms in a broader sample, and stimulus phase is thought to be lost for frequencies above 1-3 kHz. Yet bats perceive echo delay with an accuracy of 10-15 ns and have two-echo resolution of about 2 microsecond(s) . Moreover, bats perceive echo phase-shifts as the correctly corresponding shifts in echo delay. Successive images are subtracted to enhance perception of shape from multiple 'looks', and echo phase is an integral part of this critical process. Utterly novel time-scale magnification appears in the bat's neural responses to

  2. Opto-acoustic image fusion technology for diagnostic breast imaging in a feasibility study

    NASA Astrophysics Data System (ADS)

    Zalev, Jason; Clingman, Bryan; Herzog, Don; Miller, Tom; Ulissey, Michael; Stavros, A. T.; Oraevsky, Alexander; Lavin, Philip; Kist, Kenneth; Dornbluth, N. C.; Otto, Pamela

    2015-03-01

    Functional opto-acoustic (OA) imaging was fused with gray-scale ultrasound acquired using a specialized duplex handheld probe. Feasibility Study findings indicated the potential to more accurately characterize breast masses for cancer than conventional diagnostic ultrasound (CDU). The Feasibility Study included OA imagery of 74 breast masses that were collected using the investigational Imagio® breast imaging system. Superior specificity and equal sensitivity to CDU was demonstrated, suggesting that OA fusion imaging may potentially obviate the need for negative biopsies without missing cancers in a certain percentage of breast masses. Preliminary results from a 100 subject Pilot Study are also discussed. A larger Pivotal Study (n=2,097 subjects) is underway to confirm the Feasibility Study and Pilot Study findings.

  3. Acoustic micro-Doppler radar for human gait imaging.

    PubMed

    Zhang, Zhaonian; Pouliquen, Philippe O; Waxman, Allen; Andreou, Andreas G

    2007-03-01

    A portable acoustic micro-Doppler radar system for the acquisition of human gait signatures in indoor and outdoor environments is reported. Signals from an accelerometer attached to the leg support the identification of the components in the measured micro-Doppler signature. The acoustic micro-Doppler system described in this paper is simpler and offers advantages over the widely used electromagnetic wave micro-Doppler radars.

  4. Precisely shaped acoustic ablation of tumors utilizing steerable needle and 3D ultrasound image guidance

    NASA Astrophysics Data System (ADS)

    Boctor, Emad M.; Stolka, Philipp; Kang, Hyun-Jae; Clarke, Clyde; Rucker, Caleb; Croom, Jordon; Burdette, E. Clif; Webster, Robert J., III

    2010-02-01

    Many recent studies have demonstrated the efficacy of interstitial ablative approaches for the treatment of hepatic tumors. Despite these promising results, current systems remain highly dependent on operator skill, and cannot treat many tumors because there is little control of the size and shape of the zone of necrosis, and no control over ablator trajectory within tissue once insertion has taken place. Additionally, tissue deformation and target motion make it extremely difficult to place the ablator device precisely into the target. Irregularly shaped target volumes typically require multiple insertions and several overlapping (thermal) lesions, which are even more challenging to accomplish in a precise, predictable, and timely manner without causing excessive damage to surrounding normal tissues. In answer to these problems, we have developed a steerable acoustic ablator called the ACUSITT with the ability of directional energy delivery to precisely shape the applied thermal dose . In this paper, we address image guidance for this device, proposing an innovative method for accurate tracking and tool registration with spatially-registered intra-operative three-dimensional US volumes, without relying on an external tracking device. This method is applied to guid-ance of the flexible, snake-like, lightweight, and inexpensive ACUSITT to facilitate precise placement of its ablator tip within the liver, with ablation monitoring via strain imaging. Recent advancements in interstitial high-power ultrasound applicators enable controllable and penetrating heating patterns which can be dynamically altered. This paper summarizes the design and development of the first synergistic system that integrates a novel steerable interstitial acoustic ablation device with a novel trackerless 3DUS guidance strategy.

  5. 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.

    2004-05-01

    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.

  6. Robustness of speckle imaging techniques applied to horizontal imaging scenarios

    NASA Astrophysics Data System (ADS)

    Bos, Jeremy P.

    Atmospheric turbulence near the ground severely limits the quality of imagery acquired over long horizontal paths. In defense, surveillance, and border security applications, there is interest in deploying man-portable, embedded systems incorporating image reconstruction to improve the quality of imagery available to operators. To be effective, these systems must operate over significant variations in turbulence conditions while also subject to other variations due to operation by novice users. Systems that meet these requirements and are otherwise designed to be immune to the factors that cause variation in performance are considered robust. In addition to robustness in design, the portable nature of these systems implies a preference for systems with a minimum level of computational complexity. Speckle imaging methods are one of a variety of methods recently been proposed for use in man-portable horizontal imagers. In this work, the robustness of speckle imaging methods is established by identifying a subset of design parameters that provide immunity to the expected variations in operating conditions while minimizing the computation time necessary for image recovery. This performance evaluation is made possible using a novel technique for simulating anisoplanatic image formation. I find that incorporate as few as 15 image frames and 4 estimates of the object phase per reconstructed frame provide an average reduction of 45% reduction in Mean Squared Error (MSE) and 68% reduction in deviation in MSE. In addition, the Knox-Thompson phase recovery method is demonstrated to produce images in half the time required by the bispectrum. Finally, it is shown that certain blind image quality metrics can be used in place of the MSE to evaluate reconstruction quality in field scenarios. Using blind metrics rather depending on user estimates allows for reconstruction quality that differs from the minimum MSE by as little as 1%, significantly reducing the deviation in

  7. 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.

  8. Spatial Prediction Filtering of Acoustic Clutter and Random Noise in Medical Ultrasound Imaging.

    PubMed

    Shin, Junseob; Huang, Lianjie

    2017-02-01

    One of the major challenges in array-based medical ultrasound imaging is the image quality degradation caused by sidelobes and off-axis clutter, which is an inherent limitation of the conventional delay-and-sum (DAS) beamforming operating on a finite aperture. Ultrasound image quality is further degraded in imaging applications involving strong tissue attenuation and/or low transmit power. In order to effectively suppress acoustic clutter from off-axis targets and random noise in a robust manner, we introduce in this paper a new adaptive filtering technique called frequency-space (F-X) prediction filtering or FXPF, which was first developed in seismic imaging for random noise attenuation. Seismologists developed FXPF based on the fact that linear and quasilinear events or wavefronts in the time-space (T-X) domain are manifested as a superposition of harmonics in the frequency-space (F-X) domain, which can be predicted using an auto-regressive (AR) model. We describe the FXPF technique as a spectral estimation or a direction-of-arrival problem, and explain why adaptation of this technique into medical ultrasound imaging is beneficial. We apply our new technique to simulated and tissue-mimicking phantom data. Our results demonstrate that FXPF achieves CNR improvements of 26% in simulated noise-free anechoic cyst, 109% in simulated anechoic cyst contaminated with random noise of 15 dB SNR, and 93% for experimental anechoic cyst from a custom-made tissue-mimicking phantom. Our findings suggest that FXPF is an effective technique to enhance ultrasound image contrast and has potential to improve the visualization of clinically important anatomical structures and diagnosis of diseased conditions.

  9. 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.

  10. Acoustic imaging and mirage effects with high transmittance in a periodically perforated metal slab

    NASA Astrophysics Data System (ADS)

    Zhao, Sheng-Dong; Wang, Yue-Sheng; Zhang, Chuanzeng

    2016-11-01

    In this paper, we present a high-quality superlens to focus acoustic waves using a periodically perforated metallic structure which is made of zinc and immersed in water. By changing a geometrical parameter gradually, a kind of gradient-index phononic crystal lens is designed to attain the mirage effects. The acoustic waves can propagate along an arc-shaped trajectory which is precisely controlled by the angle and frequency of the incident waves. The negative refraction imaging effect depends delicately on the transmittance of the solid structure. The acoustic impedance matching between the solid and the liquid proposed in this article, which is determined by the effective density and group velocity of the unit-cell, is significant for overcoming the inefficiency problem of acoustic devices. This study focuses on how to obtain the high transmittance imaging and mirage effects based on the adequate material selection and geometrical design.

  11. Sensitivity improvement of optical fiber acoustic probe for all-optical photoacoustic imaging system

    NASA Astrophysics Data System (ADS)

    Seki, Atsushi; Iwai, Katsumasa; Katagiri, Takashi; Matsuura, Yuji

    2017-07-01

    An acoustic probe based on a Fabry-Perot interferometer composed of a polymer film attached to the end of an optical fiber was designed and fabricated for an endoscopic, all-optical photoacoustic imaging system. The finesse of the interferometer was improved by forming a half-mirror at the end of the fiber and a partial reflection mirror on the outer surface of the polymer film. A photoacoustic imaging system was constructed by combining the fiber-optic acoustic probe with a bundle of hollow optical fibers used for the excitation of the photoacoustic wave, and an image of blood capillaries in a fish ovarian membrane was successfully obtained.

  12. Modeling Hemodynamic Responses in Auditory Cortex at 1.5T Using Variable Duration Imaging Acoustic Noise

    PubMed Central

    Hu, Shuowen; Olulade, Olumide; Gonzalez, Javier Castillo; Santos, Joseph; Kim, Sungeun; Tamer, Gregory G.; Luh, Wen-Ming; Talavage, Thomas M.

    2009-01-01

    A confound for functional magnetic resonance imaging (fMRI), especially for auditory studies, is the presence of imaging acoustic noise generated mainly as a byproduct of rapid gradient switching during volume acquisition and to a lesser extent, the radio-frequency transmit. This work utilized a novel pulse sequence to present actual imaging acoustic noise for characterization of the induced hemodynamic responses and assessment of linearity in the primary auditory cortex with respect to noise duration. Results show that responses to brief duration (46ms) imaging acoustic noise is highly nonlinear while responses to longer duration (>1s) imaging acoustic noise becomes approximately linear, with the right primary auditory cortex exhibiting a higher degree of nonlinearity than the left for the investigated noise durations. This study also assessed the spatial extent of activation induced by imaging acoustic noise, showing that the use of modeled responses (specific to imaging acoustic noise) as the reference waveform revealed additional activations in the auditory cortex not observed with a canonical gamma variate reference waveform, suggesting an improvement in detection sensitivity for imaging acoustic noise-induced activity. Longer duration (1.5s) imaging acoustic noise was observed to induce activity that expanded outwards from Heschl’s gyrus to cover the superior temporal gyrus as well as parts of the middle temporal gyrus and insula, potentially affecting higher level acoustic processing. PMID:19948232

  13. Contrast Enhancement for Thermal Acoustic Breast Cancer Imaging via Resonant Stimulation

    DTIC Science & Technology

    2009-03-01

    Olsen and J. C. Lin, “Acoustic imaging of a model of a human hand using pulsed microwave irradiation,” Bioelectromagnetics, vol. 4, pp. 397–400, 1983. [2...E. Steen and B. Olstad, “Volume rendering of 3-D medical ultrasound data using direct feature mapping,” IEEE Trans. Med. Imag., vol. 13, no. 6, pp

  14. Acoustic noise reduction in T 1- and proton-density-weighted turbo spin-echo imaging.

    PubMed

    Ott, Martin; Blaimer, Martin; Breuer, Felix; Grodzki, David; Heismann, Björn; Jakob, Peter

    2016-02-01

    To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice. Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison. An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1-4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved. The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.

  15. High-spatial-resolution sub-surface imaging using a laser-based acoustic microscopy technique.

    PubMed

    Balogun, Oluwaseyi; Cole, Garrett D; Huber, Robert; Chinn, Diane; Murray, Todd W; Spicer, James B

    2011-01-01

    Scanning acoustic microscopy techniques operating at frequencies in the gigahertz range are suitable for the elastic characterization and interior imaging of solid media with micrometer-scale spatial resolution. Acoustic wave propagation at these frequencies is strongly limited by energy losses, particularly from attenuation in the coupling media used to transmit ultrasound to a specimen, leading to a decrease in the depth in a specimen that can be interrogated. In this work, a laser-based acoustic microscopy technique is presented that uses a pulsed laser source for the generation of broadband acoustic waves and an optical interferometer for detection. The use of a 900-ps microchip pulsed laser facilitates the generation of acoustic waves with frequencies extending up to 1 GHz which allows for the resolution of micrometer-scale features in a specimen. Furthermore, the combination of optical generation and detection approaches eliminates the use of an ultrasonic coupling medium, and allows for elastic characterization and interior imaging at penetration depths on the order of several hundred micrometers. Experimental results illustrating the use of the laser-based acoustic microscopy technique for imaging micrometer-scale subsurface geometrical features in a 70-μm-thick single-crystal silicon wafer with a (100) orientation are presented.

  16. [Specifics of perception of acoustic image of intrinsic bioelectric brain activity].

    PubMed

    Konstantinov, K V; Leonova, M K; Miroshnikov, D B; Klimenko, V M

    2014-06-01

    We studied the particularities of perception of the acoustic image of intrinsic EEG. We found that the assessment of perception of sounds, the presentation of which was synchronized and was agreed with current bioelectric brain activity, is higher that assessment of perception of acoustic EEG image presented in recorded form. Presentation of recorded acoustic image of EEG is accompanied by increased activity of beta-band in the frontal areas, while real-time presentation of acoustic EEG image is accompanied by the increase of slow wave activity: theta- and delta-bands of occipital areas of the brain. Increase activity in theta- and delta-bands of occipital areas in sessions of hearing the acoustic image of EEG in real time depend on the baseline frequency structure of EEG and correlates with expression of alpha-, beta- and theta-bands of bioelectric brain activity in both frontal and occipital areas. We suppose that presentation of sounds synchronized and agreed with the current bioelectric activity, activated the regulatory brain structures.

  17. 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

  18. Dynamic simulation of viscoelastic soft tissue in acoustic radiation force creep imaging.

    PubMed

    Zhao, Xiaodong; Pelegri, Assimina A

    2014-09-01

    Acoustic radiation force (ARF) creep imaging applies step ARF excitation to induce creep displacement of soft tissue, and the corresponding time-dependent responses are used to estimate soft tissue viscoelasticity or its contrast. Single degree of freedom (SDF) and homogeneous analytical models have been used to characterize soft tissue viscoelasticity in ARF creep imaging. The purpose of this study is to investigate the fundamental limitations of the commonly used SDF and homogeneous assumptions in ARF creep imaging. In this paper, finite element (FE) models are developed to simulate the dynamic behavior of viscoelastic soft tissue subjected to step ARF. Both homogeneous and heterogeneous models are studied with different soft tissue viscoelasticity and ARF configurations. The results indicate that the SDF model can provide good estimations for homogeneous soft tissue with high viscosity, but exhibits poor performance for low viscosity soft tissue. In addition, a smaller focal region of the ARF is desirable to reduce the estimation error with the SDF models. For heterogeneous media, the responses of the focal region are highly affected by the local heterogeneity, which results in deterioration of the effectiveness of the SDF and homogeneous simplifications.

  19. Virtual Acoustics

    NASA Astrophysics Data System (ADS)

    Lokki, Tapio; Savioja, Lauri

    The term virtual acoustics is often applied when sound signal is processed to contain features of a simulated acoustical space and sound is spatially reproduced either with binaural or with multichannel techniques. Therefore, virtual acoustics consists of spatial sound reproduction and room acoustics modeling.

  20. Smart DNA Fabrication Using Sound Waves: Applying Acoustic Dispensing Technologies to Synthetic Biology.

    PubMed

    Kanigowska, Paulina; Shen, Yue; Zheng, Yijing; Rosser, Susan; Cai, Yizhi

    2016-02-01

    Acoustic droplet ejection (ADE) technology uses focused acoustic energy to transfer nanoliter-scale liquid droplets with high precision and accuracy. This noncontact, tipless, low-volume dispensing technology minimizes the possibility of cross-contamination and potentially reduces the costs of reagents and consumables. To date, acoustic dispensers have mainly been used in screening libraries of compounds. In this paper, we describe the first application of this powerful technology to the rapidly developing field of synthetic biology, for DNA synthesis and assembly at the nanoliter scale using a Labcyte Echo 550 acoustic dispenser. We were able to successfully downscale PCRs and the popular one-pot DNA assembly methods, Golden Gate and Gibson assemblies, from the microliter to the nanoliter scale with high assembly efficiency, which effectively cut the reagent cost by 20- to 100-fold. We envision that acoustic dispensing will become an instrumental technology in synthetic biology, in particular in the era of DNA foundries.

  1. 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

  2. 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.

  3. Delay-and-sum beamforming for direction of arrival estimation applied to gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, António L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2011-06-01

    Sniper positioning systems described in the literature use a two-step algorithm to estimate the sniper's location. First, the shockwave and the muzzle blast acoustic signatures must be detected and recognized, followed by an estimation of their respective direction-of-arrival (DOA). Second, the actual sniper's position is calculated based on the estimated DOA via an iterative algorithm that varies from system to system. The overall performance of such a system, however, is highly compromised when the first step is not carried out successfully. Currently available systems rely on a simple calculation of differences of time-of-arrival to estimate angles-of-arrival. This approach, however, lacks robustness by not taking full advantage of the array of sensors. This paper shows how the delay-and-sum beamforming technique can be applied to estimate the DOA for both the shockwave and the muzzle blast. The method has the twofold advantage of 1) adding an array gain of 10 logM, i.e., an increased SNR of 6 dB for a 4-microphone array, which is equivalent to doubling the detection range assuming free-field propagation; and 2) offering improved robustness in handling single- and multi-shots events as well as reflections by taking advantage of the spatial filtering capability.

  4. 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.

  5. 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.

  6. Tonpilz piezoelectric transducers with acoustic matching plates for underwater color image transmission.

    PubMed

    Inoue, T; Nada, T; Tsuchiya, T; Nakanishi, T; Miyama, T; Konno, M

    1993-01-01

    Tonpilz piezoelectric transducers with multiple acoustic matching plates are suitable for color image acoustic transmission, to achieve wideband low-ripple characteristics as well as high-efficiency high-power transmitting capability. The design method for the transducers was investigated on the basis of multiple-mode filter synthesis theory. For transducers with single, double, and triple matching plates, optimum specific acoustic impedances and lengths were calculated. Moreover, based on this design method, a 24 kHz array comprising nine identical transducers with single matching plates was built and evaluated. As a result, this array showed high-efficiency, low-ripple, and wideband characteristics. Excellent agreement between theoretical values and experimental results was obtained. A field test was carried out on color image transmission from a 3500 m sea depth, using the fabricated array, during which good color images were received.

  7. Acoustic tomographic imaging of temperature and flow fields in air

    NASA Astrophysics Data System (ADS)

    Barth, Manuela; Raabe, Armin

    2011-03-01

    Acoustic travel-time tomography is a remote sensing technique that uses the dependence of sound speed in air on temperature and wind speed along the sound propagation path. Travel-time measurements of acoustic signals between several sound sources and receivers travelling along different paths through a measuring area give information on the spatial distribution of temperature and flow fields within the area. After a separation of the two influences, distributions of temperature and flow can be reconstructed using inverse algorithms. As a remote sensing method, one advantage of acoustic travel-time tomography is its ability to measure temperature and flow field quantities without disturbing the area under investigation due to insertion of sensors. Furthermore, the two quantities—temperature and flow velocity—can be recorded simultaneously with this measurement method. In this paper, an acoustic tomographic measurement system is introduced which is capable of resolving three-dimensional distributions of temperature and flow fields in air within a certain volume (1.3 m × 1.0 m × 1.2 m) using 16 acoustic transmitter-receiver pairs. First, algorithms for the 3D reconstruction of distributions from line-integrated measurements are presented. Moreover, a measuring apparatus is introduced which is suited for educational purposes, for demonstration of the method as well as for indoor investigations. Example measurements within a low-speed wind tunnel with different incident flow situations (e.g. behind bluff bodies) using this system are shown. Visualizations of the flow illustrate the plausibility of the tomographically reconstructed flow structures. Furthermore, alternative individual measurement methods for temperature and flow speed provide comparable results.

  8. NOTE: Acoustical properties of selected tissue phantom materials for ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Zell, K.; Sperl, J. I.; Vogel, M. W.; Niessner, R.; Haisch, C.

    2007-10-01

    This note summarizes the characterization of the acoustic properties of four materials intended for the development of tissue, and especially breast tissue, phantoms for the use in photoacoustic and ultrasound imaging. The materials are agar, silicone, polyvinyl alcohol gel (PVA) and polyacrylamide gel (PAA). The acoustical properties, i.e., the speed of sound, impedance and acoustic attenuation, are determined by transmission measurements of sound waves at room temperature under controlled conditions. Although the materials are tested for application such as photoacoustic phantoms, we focus here on the acoustic properties, while the optical properties will be discussed elsewhere. To obtain the acoustic attenuation in a frequency range from 4 MHz to 14 MHz, two ultrasound sources of 5 MHz and 10 MHz core frequencies are used. For preparation, each sample is cast into blocks of three different thicknesses. Agar, PVA and PAA show similar acoustic properties as water. Within silicone polymer, a significantly lower speed of sound and higher acoustical attenuation than in water and human tissue were found. All materials can be cast into arbitrary shapes and are suitable for tissue-mimicking phantoms. Due to its lower speed of sound, silicone is generally less suitable than the other presented materials.

  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. Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition.

    PubMed

    de Bever, Joshua T; Odéen, Henrik; Hofstetter, Lorne W; Parker, Dennis L

    2017-08-10

    A novel and practical method for simultaneously performing MR acoustic radiation force imaging (ARFI) and proton resonance frequency (PRF)-shift thermometry has been developed and tested. This could be an important tool for evaluating the success of MR-guided focused ultrasound procedures for which MR-thermometry measures temperature and thermal dose and MR-ARFI detects changes in tissue mechanical properties. MR imaging was performed using a gradient recalled echo segmented echo-planar imaging pulse sequence with bipolar motion encoding gradients (MEG). Images with ultrasound pulses (ON) and without ultrasound pulses (OFF) during the MEG were interleaved at the repetition time (TR) level. ARFI displacements were calculated by complex subtraction of ON-OFF images, and PRF temperature maps were calculated by baseline subtraction. Evaluations in tissue-mimicking phantoms and ex vivo porcine brain tissue were performed. Constrained reconstruction improved the temporal resolution of dynamic measurements. Simultaneous maps of displacement and temperature were acquired in 2D and 3D while keeping tissue heating < 1°C. Accuracy of the temperature maps was comparable to the standard PRF sequence. Using constrained reconstruction and subsampled k-space (R = 4.33), 3D simultaneous temperature and displacement maps can be acquired every 4.7 s. This new sequence acquires simultaneous temperature and displacement maps with minimal tissue heating, and can be applied dynamically for monitoring tissue mechanical properties during ablation procedures. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  11. Acoustic imaging of vapor bubbles through optically non-transparent media

    NASA Astrophysics Data System (ADS)

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

    1983-10-01

    A preliminary investigation of the feasibility of acoustic imaging of vapor bubbles through optically nontransparent media is described. Measurements are reported showing the echo signals produced by air filled glass spheres of various sizes positioned in an aqueous medium as well as signals produced by actual vapor bubbles within a water filled steel pipe. In addition, the influence of the metallic wall thickness and material on the amplitude of the echo signals is investigated. Finally several examples are given of the imaging of spherical bubbles within metallic pipes using a simulated array of acoustic transducers mounted circumferentially around the pipe. The measurement procedures and a description of the measuring system are also given.

  12. 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.

  13. Ultrasound artifacts: classification, applied physics with illustrations, and imaging appearances.

    PubMed

    Prabhu, Somnath J; Kanal, Kalpana; Bhargava, Puneet; Vaidya, Sandeep; Dighe, Manjiri K

    2014-06-01

    Ultrasound has become a widely used diagnostic imaging modality in medicine because of its safety and portability. Because of rapid advances in technology, in recent years, sonographic imaging quality has significantly increased. Despite these advances, the potential to encounter artifacts while imaging remains.This article classifies both common and uncommon gray-scale and Doppler ultrasound artifacts into those resulting from physiology and those caused by hardware. A brief applied-physics explanation for each artifact is listed along with an illustrated diagram. The imaging appearance of artifacts is presented in case examples, along with strategies to minimize the artifacts in real time or use them for clinical advantage where applicable.

  14. Predictive Acoustic Modelling Applied to the Control of Intake/exhaust Noise of Internal Combustion Engines

    NASA Astrophysics Data System (ADS)

    Davies, P. O. A. L.; Harrison, M. F.

    1997-05-01

    The application of validated acoustic models to intake/exhaust system acoustic design is described with reference to a sequence of specific practical examples. These include large turbocharged diesel generating sets, truck engines and high performance petrol engines. The discussion includes a comparison of frequency domain, time domain and hybrid modelling approaches to design methodology. The calculation of sound emission from open terminations is summarized in an appendix.

  15. 3D Underwater Imaging Using Vector Acoustic Sensors

    DTIC Science & Technology

    2007-12-01

    infidelity. Direc- tionality also can be lost when two waves from different directions arrive simultaneously. Figure 3 shows a hodograph of the direct...red) deviated substantially from the axis. The *-direction -0.2 -0.1 0 0.1 0.2 X-axis response Figure 3. Hodograph of the x...the sensor motions caused by the scattered waves from the targets. This hodograph illustrates the directional informa- tion in vector acoustic data

  16. Quadratic Time-Frequency Analysis of Hydroacoustic Signals as Applied to Acoustic Emissions of Large Whales

    NASA Astrophysics Data System (ADS)

    Le Bras, Ronan; Victor, Sucic; Damir, Malnar; Götz, Bokelmann

    2014-05-01

    In order to enrich the set of attributes in setting up a large database of whale signals, as envisioned in the Baleakanta project, we investigate methods of time-frequency analysis. The purpose of establishing the database is to increase and refine knowledge of the emitted signal and of its propagation characteristics, leading to a better understanding of the animal migrations in a non-invasive manner and to characterize acoustic propagation in oceanic media. The higher resolution for signal extraction and a better separation from other signals and noise will be used for various purposes, including improved signal detection and individual animal identification. The quadratic class of time-frequency distributions (TFDs) is the most popular set of time-frequency tools for analysis and processing of non-stationary signals. Two best known and most studied members of this class are the spectrogram and the Wigner-Ville distribution. However, to be used efficiently, i.e. to have highly concentrated signal components while significantly suppressing interference and noise simultaneously, TFDs need to be optimized first. The optimization method used in this paper is based on the Cross-Wigner-Ville distribution, and unlike similar approaches it does not require prior information on the analysed signal. The method is applied to whale signals, which, just like the majority of other real-life signals, can generally be classified as multicomponent non-stationary signals, and hence time-frequency techniques are a natural choice for their representation, analysis, and processing. We present processed data from a set containing hundreds of individual calls. The TFD optimization method results into a high resolution time-frequency representation of the signals. It allows for a simple extraction of signal components from the TFD's dominant ridges. The local peaks of those ridges can then be used for the signal components instantaneous frequency estimation, which in turn can be used as

  17. Fractional Fourier Transform Applied to Digital Images Encryption

    NASA Astrophysics Data System (ADS)

    Vilardy, Juan M.; Torres, Cesar O.; Mattos, Lorenzo

    2008-04-01

    In the present paper a digital algorithm was developed to make phase encryption of digital indexed images to color using the fractional Fourier transform (the images in RGB are converted to indexed before to encrypt). The indexed images are represented by a matrix of M×N pixels (where M defines the height and N is the Width of the image) and a color map (it's a matrix of C×3 elements, where C indicates the colors number of the image and the number 3 indicates the three columns associated with the color components: Red, Green and Blue of each pixel of the matrix of M×N) associated to the matrix of pixels to suitably represent the color information of the image. The indexed image (matrix of M×N pixels) to encrypt is placed as the phase of a complex exponential, then is transformed three times and multiplied in intermediate steps by two random phase masks statistically independent thus to obtain the encrypted image, for decrypt the coding image the encryption procedure is applied in the inverse sense to the conjugated complex of the encrypted image, then is taken the negative of the phase of the resulting function of the decryption process and the original image is obtained this way that had been encrypted; For the color map equal procedure is applied in the encryption/decryption process described previously for the matrix of M×N pixels. In the implemented cryptographic algorithm five keys are used, constituted by three fractional orders and two random phase masks, all these keys are necessary for a correct decryption providing a dependability to the transference of images by means of the communications nets.

  18. Experimental study on acoustic subwavelength imaging based on zero-mass metamaterials

    NASA Astrophysics Data System (ADS)

    Xu, Xianchen; Li, Pei; Zhou, Xiaoming; Hu, Gengkai

    2015-01-01

    Anisotropic zero-mass acoustic metamaterials are able to transmit evanescent waves without decaying to a far distance, and have been used for near-field acoustic subwavelength imaging. In this work, we design and fabricate such metamaterial lens based on clamped paper membrane units. The zero-mass frequency is determined by normal-incidence acoustic transmission measurement. At this frequency, we verify in experiment that the fabricated metamaterial lens is able to distinguish clearly two sound sources separated with a distance 0.16λ0 (λ0 is the wavelength in air) below the diffraction limit. We also demonstrate that the imaging frequency is invariant to the change of the lens thickness.

  19. Image Enhancement and Display Techniques Applied to SAR580 Images of Ships

    DTIC Science & Technology

    1987-04-01

    applied to the images. This report discusses tht properties of SAR ship returns, reviews the various types of image enhancement techniques applied to...Figures , , a . . . . , , , . . . , . . . . , . . iii I. INTRODUCTION . . . . . . . . . . . . I 2. PROPERTIES OF SAR SHIP IMAGES ... ... ...... I 3...Page 1 Original Ship Photos 5 2 Ship Profile and Plan Views 9 3 SAR Ship Images 14 4 SAR Contour Plots 16 5 SAR Three-Dimensional Plots 19 6 Container

  20. Applied imaging at the NASA Lewis Research Center

    NASA Astrophysics Data System (ADS)

    Slater, Howard A.; Owens, Jay C.

    1993-01-01

    NASA Lewis Research Center in Cleveland, Ohio has just completed the celebration of its 50th anniversary. `During the past 50 years, Lewis helped win World War II, made jet aircraft safer and more efficient, helped Americans land on the Moon ... and engaged in the type of fundamental research that benefits all of us in our daily lives.' As part of the center's long history, the Photographic and Printing Branch has continued to develop and meet the center's research imaging requirements. As imaging systems continue to advance and researchers more clearly understand the power of imaging, investigators are relying more and more on imaging systems to meet program objectives. Today, the Photographic and Printing Branch supports a research community of over 5,000 including advocacy for NASA Headquarters and other government agencies. Complete classified and unclassified imaging services include high- speed image acquisition, technical film and video documentaries, still imaging, and conventional and unconventional photofinishing operations. These are the foundation of the branch's modern support function. This paper provides an overview of the varied applied imaging programs managed by the Photographic and Printing Branch. Emphasis is placed on recent imaging projects including icing research, space experiments, and an on-line image archive.

  1. Time-domain fluorescence lifetime imaging applied to biological tissue.

    PubMed

    Elson, Dan; Requejo-Isidro, Jose; Munro, Ian; Reavell, Fred; Siegel, Jan; Suhling, Klaus; Tadrous, Paul; Benninger, Richard; Lanigan, Peter; McGinty, James; Talbot, Clifford; Treanor, Bebhinn; Webb, Stephen; Sandison, Ann; Wallace, Andrew; Davis, Dan; Lever, John; Neil, Mark; Phillips, David; Stamp, Gordon; French, Paul

    2004-08-01

    Fluorescence lifetime imaging (FLIM) is a functional imaging methodology that can provide information, not only concerning the localisation of specific fluorophores, but also about the local fluorophore environment. It may be implemented in scanning confocal or multi-photon microscopes, or in wide-field microscopes and endoscopes. When applied to tissue autofluorescence, it reveals intrinsic excellent contrast between different types and states of tissue. This article aims to review our recent progress in developing time-domain FLIM technology for microscopy and endoscopy and applying it to biological tissue.

  2. Anomalous diffusion process applied to magnetic resonance image enhancement.

    PubMed

    Senra Filho, A C da S; Salmon, C E Garrido; Murta Junior, L O

    2015-03-21

    Diffusion process is widely applied to digital image enhancement both directly introducing diffusion equation as in anisotropic diffusion (AD) filter, and indirectly by convolution as in Gaussian filter. Anomalous diffusion process (ADP), given by a nonlinear relationship in diffusion equation and characterized by an anomalous parameters q, is supposed to be consistent with inhomogeneous media. Although classic diffusion process is widely studied and effective in various image settings, the effectiveness of ADP as an image enhancement is still unknown. In this paper we proposed the anomalous diffusion filters in both isotropic (IAD) and anisotropic (AAD) forms for magnetic resonance imaging (MRI) enhancement. Filters based on discrete implementation of anomalous diffusion were applied to noisy MRI T2w images (brain, chest and abdominal) in order to quantify SNR gains estimating the performance for the proposed anomalous filter when realistic noise is added to those images. Results show that for images containing complex structures, e.g. brain structures, anomalous diffusion presents the highest enhancements when compared to classical diffusion approach. Furthermore, ADP presented a more effective enhancement for images containing Rayleigh and Gaussian noise. Anomalous filters showed an ability to preserve anatomic edges and a SNR improvement of 26% for brain images, compared to classical filter. In addition, AAD and IAD filters showed optimum results for noise distributions that appear on extreme situations on MRI, i.e. in low SNR images with approximate Rayleigh noise distribution, and for high SNR images with Gaussian or non central χ noise distributions. AAD and IAD filter showed the best results for the parametric range 1.2 < q < 1.6, suggesting that the anomalous diffusion regime is more suitable for MRI. This study indicates the proposed anomalous filters as promising approaches in qualitative and quantitative MRI enhancement.

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

    PubMed Central

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

    2016-01-01

    Abstract. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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.

  6. Noninvasive estimation of temperature elevations in biological tissues using acoustic nonlinearity parameter imaging.

    PubMed

    Liu, Xiaozhou; Gong, Xiufen; Yin, Chang; Li, Junlun; Zhang, Dong

    2008-03-01

    A method for noninvasively imaging temperature would assist the development of hyperthermia. In this study, the relationships between the acoustic nonlinearity parameters and the temperatures in porcine fat and liver were obtained. The temperature elevations induced by ultrasound irradiation of porcine fat and liver were then derived inversely from acoustic nonlinearity parameter imaging. These temperature elevations were compared with theoretical predictions and with those measured by a thermocouple. The temperature elevations at the focus in the fat and liver samples measured via a thermocouple were 21.1 +/- 0.8 degrees C and 15.7 +/- 0.6 degrees C, respectively, which coincided with those obtained by acoustic nonlinearity parameter imaging (22.0 +/- 1.4 degrees C in fat and 16.9 +/- 1.1 degrees C in liver). These may be compared with the theoretical predictions of elevations of 24.0 degrees C in fat and 19.7 degrees C in liver. The results of this study show that acoustic nonlinearity imaging may be a novel method for temperature evaluation in hyperthermia. (E-mail: xzliu@nju.edu.cn).

  7. Selective magnetic resonance imaging of magnetic nanoparticles by Acoustically Induced Rotary Saturation (AIRS)

    PubMed Central

    Zhu, Bo; Witzel, Thomas; Jiang, Shan; Huang, Susie Y.; Rosen, Bruce R.; Wald, Lawrence L.

    2016-01-01

    Purpose We introduce a new method to selectively detect iron oxide contrast agents using an acoustic wave to perturb the spin-locked water signal in the vicinity of the magnetic particles. The acoustic drive can be externally modulated to turn the effect on and off, allowing sensitive and quantitative statistical comparison and removal of confounding image background variations. Methods We demonstrate the effect in spin-locking experiments using piezoelectric actuators to generate vibrational displacements of iron oxide samples. We observe a resonant behavior of the signal changes with respect to the acoustic frequency where iron oxide is present. We characterize the effect as a function of actuator displacement and contrast agent concentration. Results The resonant effect allows us to generate block-design “modulation response maps” indicating the contrast agent’s location, as well as positive contrast images with suppressed background signal. We show the AIRS effect stays approximately constant across acoustic frequency, and behaves monotonically over actuator displacement and contrast agent concentration. Conclusion AIRS is a promising method capable of using acoustic vibrations to modulate the contrast from iron oxide nanoparticles and thus perform selective detection of the contrast agents, potentially enabling more accurate visualization of contrast agents in clinical and research settings. PMID:25537578

  8. MR acoustic radiation force imaging: in vivo comparison to ultrasound motion tracking.

    PubMed

    Huang, Yuexi; Curiel, Laura; Kukic, Aleksandra; Plewes, Donald B; Chopra, Rajiv; Hynynen, Kullervo

    2009-06-01

    MR acoustic radiation force (ARF) imaging was developed for measuring tiSsue elastic properties using focused ultrasound to deliver a localized tissue motion. In this study, an imaging ultrasound transducer was mounted on the focused ultrasound transducer and ultrasound motion tracking was performed simultaneously to MR ARF imaging to validate the measurement results. In vivo studies on rabbit thigh muscle were performed and results showed a general agreement between the two modalities (slope=0.96 and R2=0.67). The temporal information by the ultrasound measurement indicates that the parameters in MR ARF imaging should be optimized according to the tissue type, acoustic power, and envelope and frequency of the ARF modulation.

  9. Acoustic imaging of underground storage tank wastes: A feasibility study. Final report

    SciTech Connect

    Turpening, R.; Zhu, Z.; Caravana, C.; Matarese, J.; Turpening, W.

    1995-12-31

    The objectives for this underground storage tank (UST) imaging investigation are: (1) to assess the feasibility of using acoustic methods in UST wastes, if shown to be feasible, develop and assess imaging strategies; (2) to assess the validity of using chemical simulants for the development of acoustic methods and equipment. This investigation examined the velocity of surrogates, both salt cake and sludge surrogates. In addition collected seismic cross well data in a real tank (114-TX) on the Hanford Reservation. Lastly, drawing on the knowledge of the simulants and the estimates of the velocities of the waste in tank 114-TX the authors generated a hypothetical model of waste in a tank and showed that non-linear travel time tomographic imaging would faithfully image that stratigraphy.

  10. An Efficient Acoustic Density Estimation Method with Human Detectors Applied to Gibbons in Cambodia

    PubMed Central

    Kidney, Darren; Rawson, Benjamin M.; Borchers, David L.; Stevenson, Ben C.; Marques, Tiago A.; Thomas, Len

    2016-01-01

    Some animal species are hard to see but easy to hear. Standard visual methods for estimating population density for such species are often ineffective or inefficient, but methods based on passive acoustics show more promise. We develop spatially explicit capture-recapture (SECR) methods for territorial vocalising species, in which humans act as an acoustic detector array. We use SECR and estimated bearing data from a single-occasion acoustic survey of a gibbon population in northeastern Cambodia to estimate the density of calling groups. The properties of the estimator are assessed using a simulation study, in which a variety of survey designs are also investigated. We then present a new form of the SECR likelihood for multi-occasion data which accounts for the stochastic availability of animals. In the context of gibbon surveys this allows model-based estimation of the proportion of groups that produce territorial vocalisations on a given day, thereby enabling the density of groups, instead of the density of calling groups, to be estimated. We illustrate the performance of this new estimator by simulation. We show that it is possible to estimate density reliably from human acoustic detections of visually cryptic species using SECR methods. For gibbon surveys we also show that incorporating observers’ estimates of bearings to detected groups substantially improves estimator performance. Using the new form of the SECR likelihood we demonstrate that estimates of availability, in addition to population density and detection function parameters, can be obtained from multi-occasion data, and that the detection function parameters are not confounded with the availability parameter. This acoustic SECR method provides a means of obtaining reliable density estimates for territorial vocalising species. It is also efficient in terms of data requirements since since it only requires routine survey data. We anticipate that the low-tech field requirements will make this method

  11. An Efficient Acoustic Density Estimation Method with Human Detectors Applied to Gibbons in Cambodia.

    PubMed

    Kidney, Darren; Rawson, Benjamin M; Borchers, David L; Stevenson, Ben C; Marques, Tiago A; Thomas, Len

    2016-01-01

    Some animal species are hard to see but easy to hear. Standard visual methods for estimating population density for such species are often ineffective or inefficient, but methods based on passive acoustics show more promise. We develop spatially explicit capture-recapture (SECR) methods for territorial vocalising species, in which humans act as an acoustic detector array. We use SECR and estimated bearing data from a single-occasion acoustic survey of a gibbon population in northeastern Cambodia to estimate the density of calling groups. The properties of the estimator are assessed using a simulation study, in which a variety of survey designs are also investigated. We then present a new form of the SECR likelihood for multi-occasion data which accounts for the stochastic availability of animals. In the context of gibbon surveys this allows model-based estimation of the proportion of groups that produce territorial vocalisations on a given day, thereby enabling the density of groups, instead of the density of calling groups, to be estimated. We illustrate the performance of this new estimator by simulation. We show that it is possible to estimate density reliably from human acoustic detections of visually cryptic species using SECR methods. For gibbon surveys we also show that incorporating observers' estimates of bearings to detected groups substantially improves estimator performance. Using the new form of the SECR likelihood we demonstrate that estimates of availability, in addition to population density and detection function parameters, can be obtained from multi-occasion data, and that the detection function parameters are not confounded with the availability parameter. This acoustic SECR method provides a means of obtaining reliable density estimates for territorial vocalising species. It is also efficient in terms of data requirements since since it only requires routine survey data. We anticipate that the low-tech field requirements will make this method

  12. Discrete-cosine-transform-based image compression applied to dermatology

    NASA Astrophysics Data System (ADS)

    Cookson, John P.; Sneiderman, Charles; Rivera, Christopher

    1991-05-01

    The research reported in this paper concerns an evaluation of the impact of compression on the quality of digitized color dermatologic images. 35 mm slides of four morphologic types of skin lesions were captured at 1000 pixels per inch (ppi) in 24 bit RGB color, to give an approximate 1K X 1K image. The discrete cosine transform (DCT) algorithm, was applied to the resulting image files to achieve compression ratios of about 7:1, 28:1, and 70:1. The original scans and the decompressed files were written to a 35 mm film recorder. Together with the original photo slides, the slides resulting from digital images were evaluated in a study of morphology recognition and image quality assessment. A panel of dermatologists was asked to identify the morphology depicted and to rate the image quality of each slide. The images were shown in a progression from highest level of compression to original photo slides. We conclude that the use of DCT file compression yields acceptable performance for skin lesion images since differences in morphology recognition performance do not correlate significantly with the use of original photos versus compressed versions. Additionally, image quality evaluation does not correlate significantly with level of compression.

  13. 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.

  14. Applying Image Norms across Super's Career Development Stages

    ERIC Educational Resources Information Center

    Giannantonio, Cristina M.; Hurley-Hanson, Amy E.

    2006-01-01

    D. E. Super's (1957) theory of career development has long been of interest to careers researchers (M. Savickas, 1994; S. C. Whiston & B. K. Brecheisen, 2002). Its insightful illustration of career stages has made it widely applied by careers practitioners, Image norms may influence the career decisions and developmental tasks inherent in each…

  15. Applying Image Norms across Super's Career Development Stages

    ERIC Educational Resources Information Center

    Giannantonio, Cristina M.; Hurley-Hanson, Amy E.

    2006-01-01

    D. E. Super's (1957) theory of career development has long been of interest to careers researchers (M. Savickas, 1994; S. C. Whiston & B. K. Brecheisen, 2002). Its insightful illustration of career stages has made it widely applied by careers practitioners, Image norms may influence the career decisions and developmental tasks inherent in each…

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

    PubMed

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

    2014-10-01

    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).

  17. 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

  18. Hyperspectral imaging applied to medical diagnoses and food safety

    NASA Astrophysics Data System (ADS)

    Carrasco, Oscar; Gomez, Richard B.; Chainani, Arun; Roper, William E.

    2003-08-01

    This paper analyzes the feasibility and performance of HSI systems for medical diagnosis as well as for food safety. Illness prevention and early disease detection are key elements for maintaining good health. Health care practitioners worldwide rely on innovative electronic devices to accurately identify disease. Hyperspectral imaging (HSI) is an emerging technique that may provide a less invasive procedure than conventional diagnostic imaging. By analyzing reflected and fluorescent light applied to the human body, a HSI system serves as a diagnostic tool as well as a method for evaluating the effectiveness of applied therapies. The safe supply and production of food is also of paramount importance to public health illness prevention. Although this paper will focus on imaging and spectroscopy in food inspection procedures -- the detection of contaminated food sources -- to ensure food quality, HSI also shows promise in detecting pesticide levels in food production (agriculture.)

  19. Trends in optical coherence tomography applied to medical imaging

    NASA Astrophysics Data System (ADS)

    Podoleanu, Adrian G.

    2014-01-01

    The number of publications on optical coherence tomography (OCT) continues to double every three years. Traditionally applied to imaging the eye, OCT is now being extended to fields outside ophthalmology and optometry. Widening its applicability, progress in the core engine of the technology, and impact on development of novel optical sources, make OCT a very active and rapidly evolving field. Trends in the developments of different specific devices, such as optical sources, optical configurations and signal processing will be presented. Encompassing studies on both the configurations as well as on signal processing themes, current research in Kent looks at combining spectral domain with time domain imaging for long axial range and simultaneous imaging at several depths. Results of the collaborative work of the Applied Optics Group in Kent with organisers of this conference will be presented, with reference to 3D monitoring of abfraction.

  20. Design and Evaluation of a Scalable and Reconfigurable Multi-Platform System for Acoustic Imaging

    PubMed Central

    Izquierdo, Alberto; Villacorta, Juan José; del Val Puente, Lara; Suárez, Luis

    2016-01-01

    This paper proposes a scalable and multi-platform framework for signal acquisition and processing, which allows for the generation of acoustic images using planar arrays of MEMS (Micro-Electro-Mechanical Systems) microphones with low development and deployment costs. Acoustic characterization of MEMS sensors was performed, and the beam pattern of a module, based on an 8 × 8 planar array and of several clusters of modules, was obtained. A flexible framework, formed by an FPGA, an embedded processor, a computer desktop, and a graphic processing unit, was defined. The processing times of the algorithms used to obtain the acoustic images, including signal processing and wideband beamforming via FFT, were evaluated in each subsystem of the framework. Based on this analysis, three frameworks are proposed, defined by the specific subsystems used and the algorithms shared. Finally, a set of acoustic images obtained from sound reflected from a person are presented as a case study in the field of biometric identification. These results reveal the feasibility of the proposed system. PMID:27727174

  1. Multifunctional single beam acoustic tweezer for non-invasive cell/organism manipulation and tissue imaging

    PubMed Central

    Lam, Kwok Ho; Li, Ying; Li, Yang; Lim, Hae Gyun; Zhou, Qifa; Shung, Koping Kirk

    2016-01-01

    Non-contact precise manipulation of single microparticles, cells, and organisms has attracted considerable interest in biophysics and biomedical engineering. Similar to optical tweezers, acoustic tweezers have been proposed to be capable of manipulating microparticles and even cells. Although there have been concerted efforts to develop tools for non-contact manipulation, no alternative to complex, unifunctional tweezer has yet been found. Here we report a simple, low-cost, multifunctional single beam acoustic tweezer (SBAT) that is capable of manipulating an individual micrometer scale non-spherical cell at Rayleigh regime and even a single millimeter scale organism at Mie regime, and imaging tissue as well. We experimentally demonstrate that the SBAT with an ultralow f-number (f# = focal length/aperture size) could manipulate an individual red blood cell and a single 1.6 mm-diameter fertilized Zebrafish egg, respectively. Besides, in vitro rat aorta images were collected successfully at dynamic foci in which the lumen and the outer surface of the aorta could be clearly seen. With the ultralow f-number, the SBAT offers the combination of large acoustic radiation force and narrow beam width, leading to strong trapping and high-resolution imaging capabilities. These attributes enable the feasibility of using a single acoustic device to perform non-invasive multi-functions simultaneously for biomedical and biophysical applications. PMID:27874052

  2. 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.

  3. Design and Evaluation of a Scalable and Reconfigurable Multi-Platform System for Acoustic Imaging.

    PubMed

    Izquierdo, Alberto; Villacorta, Juan José; Del Val Puente, Lara; Suárez, Luis

    2016-10-11

    This paper proposes a scalable and multi-platform framework for signal acquisition and processing, which allows for the generation of acoustic images using planar arrays of MEMS (Micro-Electro-Mechanical Systems) microphones with low development and deployment costs. Acoustic characterization of MEMS sensors was performed, and the beam pattern of a module, based on an 8 × 8 planar array and of several clusters of modules, was obtained. A flexible framework, formed by an FPGA, an embedded processor, a computer desktop, and a graphic processing unit, was defined. The processing times of the algorithms used to obtain the acoustic images, including signal processing and wideband beamforming via FFT, were evaluated in each subsystem of the framework. Based on this analysis, three frameworks are proposed, defined by the specific subsystems used and the algorithms shared. Finally, a set of acoustic images obtained from sound reflected from a person are presented as a case study in the field of biometric identification. These results reveal the feasibility of the proposed system.

  4. Multifunctional single beam acoustic tweezer for non-invasive cell/organism manipulation and tissue imaging

    NASA Astrophysics Data System (ADS)

    Lam, Kwok Ho; Li, Ying; Li, Yang; Lim, Hae Gyun; Zhou, Qifa; Shung, Koping Kirk

    2016-11-01

    Non-contact precise manipulation of single microparticles, cells, and organisms has attracted considerable interest in biophysics and biomedical engineering. Similar to optical tweezers, acoustic tweezers have been proposed to be capable of manipulating microparticles and even cells. Although there have been concerted efforts to develop tools for non-contact manipulation, no alternative to complex, unifunctional tweezer has yet been found. Here we report a simple, low-cost, multifunctional single beam acoustic tweezer (SBAT) that is capable of manipulating an individual micrometer scale non-spherical cell at Rayleigh regime and even a single millimeter scale organism at Mie regime, and imaging tissue as well. We experimentally demonstrate that the SBAT with an ultralow f-number (f# = focal length/aperture size) could manipulate an individual red blood cell and a single 1.6 mm-diameter fertilized Zebrafish egg, respectively. Besides, in vitro rat aorta images were collected successfully at dynamic foci in which the lumen and the outer surface of the aorta could be clearly seen. With the ultralow f-number, the SBAT offers the combination of large acoustic radiation force and narrow beam width, leading to strong trapping and high-resolution imaging capabilities. These attributes enable the feasibility of using a single acoustic device to perform non-invasive multi-functions simultaneously for biomedical and biophysical applications.

  5. 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.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1993-09-01

    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.

  9. 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; hide

    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.

  10. 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.

  11. Acoustic field enhancement and subwavelength imaging by coupling to slab waveguide modes

    NASA Astrophysics Data System (ADS)

    Christensen, J.; García de Abajo, F. J.

    2010-10-01

    We present a theoretical study on the amplification of evanescent sound waves produced by coupling to trapped modes hosted by a fluidic planar waveguide. Total internal reflection at interfaces of different refractive indexes can be frustrated by the introduction of a slow slab waveguide which is leading to a gigantic field enhancement, useful for sensitive transducers and acoustic shock lithotripsy. The mechanism behind the evanescent field coupling that is also known as tunnelling barrier penetration in quantum mechanics is here adopted for its use in an acoustic superlens. The higher spatial harmonics produced by a subwavelength object can couple to trapped modes of the slow waveguide and be reproduced as an image at a distant plane. We suggest a practical implementation of these ideas by means of a silicone rubber slab containing positive acoustic wave propagation parameters.

  12. Heavy-Ion <span class="hlt">Imaging</span> <span class="hlt">Applied</span> To Medicine

    SciTech Connect

    Fabrikant, J. I.; Tobias, C. A.; Capp, M. P.; Benton, E. V.; Holley, W. R.; Gray, Joel E.; Hendee, William R.; Haus, Andrew G.; Properzio, William S.

    1980-08-18

    Heavy particle radiography is a newly developed noninvasive low dose imaging procedure with increased resolution of minute density differences in soft tissues of the body. The method utilizes accelerated high energy ions, primarily carbon and neon, at the BEVALAC accelerator at the Lawrence Berkeley Laboratory. The research program applied to medicine utilizes heavy-ion radiography for low dose mammography, for treatment planning for cancer patients, and for imaging and accurate densitometry of skeletal structures and brain and spinal neoplasms. The presentation will be illustrated with clinical cases under study. Discussion will include the potential of heavy-ion imaging, and particularly reconstruction tomography, as an adjunct to existing diagnostic imaging procedures in medicine, both for the applications to the diagnosis, management and treatment of clinical cancer in man, but also for the early detection of small soft tissue tumors at low radiation dose.

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

    PubMed

    He, Zhengyao

    2014-01-01

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

  14. Partial-aperture array imaging in acoustic waveguides

    NASA Astrophysics Data System (ADS)

    Tsogka, Chrysoula; Mitsoudis, Dimitrios A.; Papadimitropoulos, Symeon

    2016-12-01

    We consider the problem of imaging extended reflectors in waveguides using partial-aperture array, i.e. an array that does not span the whole depth of the waveguide. For this imaging, we employ a method that back-propagates a weighted modal projection of the usual array response matrix. The challenge in this setup is to correctly define this projection matrix in order to maintain good energy concentration properties for the imaging method, which were obtained previously by Tsogka et al (2013 SIAM J. Imaging Sci. 6 2714-39) for the full-aperture case. In this paper we propose a way of achieving this and study the properties of the resulting imaging method.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. 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.

  18. Imaging and analyzing the elasticity of vascular smooth muscle cells by atomic force acoustic microscope.

    PubMed

    Zhang, Bo; Cheng, Qian; Chen, Ming; Yao, Wengang; Qian, Menglu; Hu, Bing

    2012-08-01

    Vascular smooth muscle cells (VSMCs) play an important role in the good performance of the vasculature. To study the surface, intracellular structure and elasticity of VSMCs, atomic force acoustic microscope (AFAM) was used for imaging VSMCs from A7r5 rat aorta arteries. The topography images of VSMCs were obtained in contact mode and the acoustic images were obtained by AFAM in sample vibration mode. Then, the force curve measurement derived using Young's modulus of the interested areas was used for evaluating elasticity properties. The acoustic images were found in higher resolution with more information than the topography images. The force curves showed the difference in Young's modulus of the different parts of VSMC. These findings demonstrate that AFAM is useful for displaying the surface, structure and elasticity property of VSMCs clearly, with short scanning time, negligible harm or damage to cell and nanometer-level resolution. Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  19. 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.

  20. Practical approach to apply range image sensors in machine automation

    NASA Astrophysics Data System (ADS)

    Moring, Ilkka; Paakkari, Jussi

    1993-10-01

    In this paper we propose a practical approach to apply range imaging technology in machine automation. The applications we are especially interested in are industrial heavy-duty machines like paper roll manipulators in harbor terminals, harvesters in forests and drilling machines in mines. Characteristic of these applications is that the sensing system has to be fast, mid-ranging, compact, robust, and relatively cheap. On the other hand the sensing system is not required to be generic with respect to the complexity of scenes and objects or number of object classes. The key in our approach is that just a limited range data set or as we call it, a sparse range image is acquired and analyzed. This makes both the range image sensor and the range image analysis process more feasible and attractive. We believe that this is the way in which range imaging technology will enter the large industrial machine automation market. In the paper we analyze as a case example one of the applications mentioned and, based on that, we try to roughly specify the requirements for a range imaging based sensing system. The possibilities to implement the specified system are analyzed based on our own work on range image acquisition and interpretation.

  1. 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.

  2. 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.

  3. Fast photoacoustic imaging with a line scanning optical-acoustical resolution photoacoustic microscope (LS-OAR-PAM)

    NASA Astrophysics Data System (ADS)

    Nuster, Robert; Paltauf, Guenther

    2015-07-01

    We present the concept, the setup and a preliminary experiment using optical ultrasound detection with a CCD camera combined with focused line excitation for photoacoustic microscopy. The line scanning optical-acoustical resolution photoacoustic microscope (LS-OAR-PAM) with optical ultrasound detection is capable of real-time B-scan imaging providing acoustical resolution within the individual B-scans and optical out of plane resolution up to a depth limited by optical diffusion. A 3D image is composed of reconstructed B-scan images recorded while scanning the excitation line along the sample surface. Proof of concept is shown by imaging a phantom containing black human hairs and carbon fibers. The obtained C-scan image clearly shows the different resolution in the two perpendicular directions, namely diffraction limited by optical focusing in scan direction and acoustically limited in direction parallel to line orientation by the properties of acoustic wave propagation.

  4. Digital image correlation techniques applied to LANDSAT multispectral imagery

    NASA Technical Reports Server (NTRS)

    Bonrud, L. O. (Principal Investigator); Miller, W. J.

    1976-01-01

    The author has identified the following significant results. Automatic image registration and resampling techniques applied to LANDSAT data achieved accuracies, resulting in mean radial displacement errors of less than 0.2 pixel. The process method utilized recursive computational techniques and line-by-line updating on the basis of feedback error signals. Goodness of local feature matching was evaluated through the implementation of a correlation algorithm. An automatic restart allowed the system to derive control point coordinates over a portion of the image and to restart the process, utilizing this new control point information as initial estimates.

  5. 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.

  6. 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

  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. A Robust Mine Detection Algorithm for Acoustic and Radar Images

    DTIC Science & Technology

    2000-10-01

    Hough transforms as demonstrated on an NVL mine hunting SBIR and on SAR ground target detection. The fundamental detection technique will be...Williams, “IA-CHAMELEON: A SAR Wide Area Image Analysis Aid,” Proc. ATRWG Workshop, Baltimore, MD, July 1996 The adaptive detection algorithm will...University, Mississippi 38677, September 15, 1998 Systems Incorporated (PSI) Ground Penetrating Radar (GPR)9, and on synthetic aperture radar ( SAR ) images

  9. Coastal Acoustic Tomography Data Constraints Applied to a Coastal Ocean Circulation Model

    DTIC Science & Technology

    1994-04-01

    proceed separately from observations, mainly due to the lack of synoptic observations to properly constrain the model physics. Two -ew technologies in...interior ocean structure. This underwater acoustic inverse techniq . - uses travel time changes of sound pulses to map sound speed/temperature perturbation...data were density measured along vari- ous hydrographic sections. The main result of the study is that a local section can be quite effective in

  10. Demonstration of acoustic resonances in a cylindrical cavity applying the photoacoustic technique

    NASA Astrophysics Data System (ADS)

    Barreiro, N. L.; Vallespi, A. S.; Zajarevich, N. M.; Peuriot, A. L.; Slezak, V. B.

    2017-09-01

    In this work we present some experiments which can be performed in college or on the first courses of university to acquire knowledge about resonant acoustical phenomena in closed cavities in a tangible way, through experiments based on the photoacoustic effect in gases. This phenomenon consists in the generation of acoustic waves after optical excitation of an absorbing gas and further local heating of the non-absorbing surrounding gas by energy exchange through collisions between molecules of both species. Simple experiments, performed with daily live elements, can be very useful for teachers and students to get in touch with the phenomenon of acoustic resonances with the addition of concepts about light-matter interaction. The setups consist of the resonant cavity, the illumination source and the signal detection-acquisition scheme. In this paper a closed glass test tube is used as the resonant cavity and is filled with a mixture of nitrogen dioxide and air. The illumination is performed by a pulsed power LED modulated at different resonant frequencies of the cavity. A microphone inside the tube is connected to an oscilloscope which displays the photoacoustic signal. The LED is moved along the tube showing how different resonant modes can be excited.

  11. Design for Aplanatic Fresnel Acoustic Lens for Underwater Imaging

    NASA Astrophysics Data System (ADS)

    Sato, Yuji; Mizutani, Koichi; Wakatsuki, Naoto; Nakamura, Toshiaki

    2009-07-01

    We designed several shapes of aplanatic Fresnel acoustic lenses to correct spherical and coma aberrations. These lenses were made of room temperature vulcanizable (RTV) silicone rubber, and were designed by combining several aplanatic lenses. The converged sound pressure fields of these lenses were calculated numerically with the two-dimensional finite difference time domain (2D FDTD) method. The focal sound pressures of these lenses were 8-9 dB larger than those of aplanatic biconvex lenses. Comparing several aplanatic Fresnel lenses, the best convergence was achieved by the lens having the smoothest first surface. We assumed the reason for this advantage was the smooth first surface itself. Thus to smooth the first surface and to enlarge the focal sound pressure, small steps on the first surface were removed by two methods. The first method approximates the first surface to a polynomial equation. The second method changes the curvature of the aplanatic lenses to minimize the small steps; this method is called bending. The evaluation of the lenses made by the two methods showed that the resolutions of these lenses were higher than 1°. The lens made by bending showed higher sound pressure than the lens made by the approximated surface.

  12. 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.

  13. Imaging textural variation in the acoustoelastic coefficient of aluminum using surface acoustic waves.

    PubMed

    Ellwood, R; Stratoudaki, T; Sharples, S D; Clark, M; Somekh, M G

    2015-11-01

    Much interest has arisen in nonlinear acoustic techniques because of their reported sensitivity to variations in residual stress, fatigue life, and creep damage when compared to traditional linear ultrasonic techniques. However, there is also evidence that the nonlinear acoustic properties are also sensitive to material microstructure. As many industrially relevant materials have a polycrystalline structure, this could potentially complicate the monitoring of material processes when using nonlinear acoustics. Variations in the nonlinear acoustoelastic coefficient on the same length scale as the microstructure of a polycrystalline sample of aluminum are investigated in this paper. This is achieved by the development of a measurement protocol that allows imaging of the acoustoelastic response of a material across a samples surface at the same time as imaging the microstructure. The development, validation, and limitations of this technique are discussed. The nonlinear acoustic response is found to vary spatially by a large factor (>20) between different grains. A relationship is observed when the spatial variation of the acoustoelastic coefficient is compared to the variation in material microstructure.

  14. List-Mode Likelihood Imaging Applied to COMPTEL Data

    NASA Astrophysics Data System (ADS)

    Zoglauer, Andreas C.; Boggs, S. E.; Collmar, W.; Kippen, M.; Novikova, E.; Weidenspointner, G.; Wunderer, C. B.

    2008-03-01

    Eight years after de-orbiting CGRO, COMPTEL's 1-30 MeV all-sky imaging performance, as well as its sensitivity for continuum sources, remain unsurpassed. Moreover, currently no official successor mission exists that might challenge COMPTEL's performance --- only GLAST is expected to improve upon COMPTEL above 20 MeV. Since the time when the original COMPTEL data analysis techniques were developed in the 1990's, the performance of state-of-the-art computers has increased by more than a factor of 100, allowing for new analysis techniques that were unthinkable at that time. These encompass detailed orbital background simulations including detector activation, Bayesian event selection techniques, and list-mode imaging. In this work we concentrate on the list-mode maximum likelihood expectation maximization (ML-EM) imaging method. It allows all measured information to be included into the imaging response of the instrument. As a consequence, this approach has the capability to produce improved images compared to those from the original techniques applied to COMPTEL data. We are currently in the process of adapting the list-mode approach to COMPTEL, determining the imaging response via simulations, and reanalyzing data with the ML-EM method. We will show first results of the Galactic anti-center region, and compare them to previous COMPTEL results.

  15. A multi-band spectral subtraction-based algorithm for real-time noise cancellation applied to gunshot acoustics

    NASA Astrophysics Data System (ADS)

    Ramos, António L. L.; Holm, Sverre; Gudvangen, Sigmund; Otterlei, Ragnvald

    2013-06-01

    Acoustical sniper positioning is based on the detection and direction-of-arrival estimation of the shockwave and the muzzle blast acoustical signals. In real-life situations, the detection and direction-of-arrival estimation processes is usually performed under the influence of background noise sources, e.g., vehicles noise, and might result in non-negligible inaccuracies than can affect the system performance and reliability negatively, specially when detecting the muzzle sound under long range distance and absorbing terrains. This paper introduces a multi-band spectral subtraction based algorithm for real-time noise reduction, applied to gunshot acoustical signals. The ballistic shockwave and the muzzle blast signals exhibit distinct frequency contents that are affected differently by additive noise. In most real situations, the noise component is colored and a multi-band spectral subtraction approach for noise reduction contributes to reducing the presence of artifacts in denoised signals. The proposed algorithm is tested using a dataset generated by combining signals from real gunshots and real vehicle noise. The noise component was generated using a steel tracked military tank running on asphalt and includes, therefore, the sound from the vehicle engine, which varies slightly in frequency over time according to the engine's rpm, and the sound from the steel tracks as the vehicle moves.

  16. 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

  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.

  18. Automated Detection Framework of the Calcified Plaque with Acoustic Shadowing in IVUS Images

    PubMed Central

    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

  19. High-speed imaging of an ultrasound-driven bubble in contact with a wall: ``Narcissus'' effect and resolved acoustic streaming

    NASA Astrophysics Data System (ADS)

    Marmottant, Philippe; Versluis, Michel; de Jong, Nico; Hilgenfeldt, Sascha; Lohse, Detlef

    2006-08-01

    We report microscopic observations of the primary flow oscillation of an acoustically driven bubble in contact with a wall, captured with the ultra high-speed camera Brandaris 128 (Chin et al. 2003). The driving frequency is up to 200 kHz, and the imaging frequency is up to 25 MHz. The details of the bubble motion during an ultrasound cycle are thus resolved, showing a combination of two modes of oscillations: a radius oscillation and a translation oscillation, perpendicular to the wall. This motion is interpreted using the theory of acoustic images to account for the presence of the wall. We conclude that the bubble is subjected to a periodic succession of attractive and repulsive forces, exerted by its own image. Fast-framing recordings of a tracer particle embedded in the liquid around the particle are performed. They fully resolve the acoustic streaming flow induced by the bubble oscillations. This non-linear secondary flow appears as a tiny drift of the particle position cycle after cycle, on top of the primary back and forth oscillation. The high oscillation frequency accounts for a fast average particle velocity, with characteristic timescales in the millisecond range at the lengthscale of the bubble. The features of the bubble motion being resolved, we can apply the acoustic streaming theory near a wall, which provides predictions in agreement with the observed streaming velocity.

  20. Applying an Automatic Image-Processing Method to Synoptic Observations

    NASA Astrophysics Data System (ADS)

    Tlatov, Andrey G.; Vasil'eva, Valeria V.; Makarova, Valentina V.; Otkidychev, Pavel A.

    2014-04-01

    We used an automatic image-processing method to detect solar-activity features observed in white light at the Kislovodsk Solar Station. This technique was applied to automatically or semi-automatically detect sunspots and active regions. The results of this automated recognition were verified with statistical data available from other observatories and revealed a high detection accuracy. We also provide parameters of sunspot areas, of the umbra, and of faculae as observed in Solar Cycle 23 as well as the magnetic flux of these active elements, calculated at the Kislovodsk Solar Station, together with white-light images and magnetograms from the Michaelson Doppler Imager onboard the Solar and Heliospheric Observatory (SOHO/MDI). The ratio of umbral and total sunspot areas during Solar Cycle 23 is ≈ 0.19. The area of sunspots of the leading polarity was approximately 2.5 times the area of sunspots of the trailing polarity.

  1. IR-Spectroscopic imaging applied to human colon biopsy

    NASA Astrophysics Data System (ADS)

    Gersonde, Ingo H.; Meinke, Martina; Becker, Y.; Bindig, Uwe; Eppich, Bernd; Mueller, G.

    2000-03-01

    Tissue samples from colon biopsy have been analyzed using FT-IR microscopy. For differentiation of cancerous versus normal tissue and for imaging of tissue structure linear and quadratic discriminant analysis was applied. A large number of samples has been used for statistical parametrization. After IR mapping, the samples have been analyzed with common pathological techniques. Comparing the pathological classification with the results of the discriminant analysis the resolving power of the later is estimated. The influence of filtering (using derivative spectra, baseline correction, and normalization) has been investigated. In vivo application of IR-spectroscopy using IR laser diodes or grating spectrometers for fast measurements will lead to a reduction of data concerning spectral range and resolution. The accompanying loss in differentiation of tissue is discussed. Images constructed with the discriminant analysis are compared to corresponding images from visible microscopy.

  2. Single-molecule localization software applied to photon counting imaging.

    PubMed

    Hirvonen, Liisa M; Kilfeather, Tiffany; Suhling, Klaus

    2015-06-01

    Centroiding in photon counting imaging has traditionally been accomplished by a single-step, noniterative algorithm, often implemented in hardware. Single-molecule localization techniques in superresolution fluorescence microscopy are conceptually similar, but use more sophisticated iterative software-based fitting algorithms to localize the fluorophore. Here, we discuss common features and differences between single-molecule localization and photon counting imaging and investigate the suitability of single-molecule localization software for photon event localization. We find that single-molecule localization software packages designed for superresolution microscopy-QuickPALM, rapidSTORM, and ThunderSTORM-can work well when applied to photon counting imaging with a microchannel-plate-based intensified camera system: photon event recognition can be excellent, fixed pattern noise can be low, and the microchannel plate pores can easily be resolved.

  3. Adapting MRI acoustic radiation force imaging for in vivo human brain focused ultrasound applications.

    PubMed

    Kaye, Elena A; Pauly, Kim Butts

    2013-03-01

    A variety of magnetic resonance imaging acoustic radiation force imaging (MR-ARFI) pulse sequences as the means for image guidance of focused ultrasound therapy have been recently developed and tested ex vivo and in animal models. To successfully translate MR-ARFI guidance into human applications, ensuring that MR-ARFI provides satisfactory image quality in the presence of patient motion and deposits safe amount of ultrasound energy during image acquisition is necessary. The first aim of this work was to study the effect of motion on in vivo displacement images of the brain obtained with 2D Fourier transform spin echo MR-ARFI. Repeated bipolar displacement encoding configuration was shown less sensitive to organ motion. The optimal signal-to-noise ratio of displacement images was found for the duration of encoding gradients of 12 ms. The second aim was to further optimize the displacement signal-to-noise ratio for a particular tissue type by setting the time offset between the ultrasound emission and encoding based on the tissue response to acoustic radiation force. A method for measuring tissue response noninvasively was demonstrated. Finally, a new method for simultaneous monitoring of tissue heating during MR-ARFI acquisition was presented to enable timely adjustment of the ultrasound energy aimed at ensuring the safety of the MR-ARFI acquisition. Copyright © 2012 Wiley Periodicals, Inc.

  4. Multimodal tissue perfusion imaging using multi-spectral and thermographic imaging systems applied on clinical data

    NASA Astrophysics Data System (ADS)

    Klaessens, John H. G. M.; Nelisse, Martin; Verdaasdonk, Rudolf M.; Noordmans, Herke Jan

    2013-03-01

    Clinical interventions can cause changes in tissue perfusion, oxygenation or temperature. Real-time imaging of these phenomena could be useful for surgical strategy or understanding of physiological regulation mechanisms. Two noncontact imaging techniques were applied for imaging of large tissue areas: LED based multispectral imaging (MSI, 17 different wavelengths 370 nm-880 nm) and thermal imaging (7.5 to 13.5 μm). Oxygenation concentration changes were calculated using different analyzing methods. The advantages of these methods are presented for stationary and dynamic applications. Concentration calculations of chromophores in tissue require right choices of wavelengths The effects of different wavelength choices for hemoglobin concentration calculations were studied in laboratory conditions and consequently applied in clinical studies. Corrections for interferences during the clinical registrations (ambient light fluctuations, tissue movements) were performed. The wavelength dependency of the algorithms were studied and wavelength sets with the best results will be presented. The multispectral and thermal imaging systems were applied during clinical intervention studies: reperfusion of tissue flap transplantation (ENT), effectiveness of local anesthetic block and during open brain surgery in patients with epileptic seizures. The LED multispectral imaging system successfully imaged the perfusion and oxygenation changes during clinical interventions. The thermal images show local heat distributions over tissue areas as a result of changes in tissue perfusion. Multispectral imaging and thermal imaging provide complementary information and are promising techniques for real-time diagnostics of physiological processes in medicine.

  5. Study of acoustic shadow moire for imaging technique

    NASA Astrophysics Data System (ADS)

    Yaqoub, Mahmoud

    This research is to utilize ultrasound waves and moire phenomena to establish a new imaging technology for industrial and medical applications. The theory and mathematical description is presented in this work. Numerical simulation is performed to prove the concept; COMSOL simulation, which uses finite difference technique, is used. The results are compared with experimental results done by a researcher from NIU at Santec Systems Inc., Wheeling, IL. The diffraction of the ultrasound waves is dependent on the wavelength. Because the sound wave length is large, a diffraction grating of wider pitch is used. Therefore, using ultrasound in shadow moire imaging will be limited by the size of pitch of the diffraction grating. Talbot image of the grating was studied using numerical simulation. The simulation results were found to be in agreement with experimental results. This is an evidence that ultrasound shadow moire has the same characteristics as light shadow moire. This work simulates the imaging of an inclined specimen with two different angles, 20 and 25 degrees. The distance between the first 2-moire fringes is found to be close to 5.5 mm. This means that the second fringe is a locus of constant out-of-plane elevation of 4.2mm with respect to the first fringe. This simulation provides an error compared with the experimental and theoretical results of 17.7%. This difference can be attributed to the fact that the experiments conditions are not ideal, and the use of paraxial and Fresnel approximation used in the analytical equations.

  6. 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…

  7. 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…

  8. Microscopic imaging of residual stress using a scanning phase-measuring acoustic microscope

    NASA Astrophysics Data System (ADS)

    Meeks, Steven W.; Peter, D.; Horne, D.; Young, K.; Novotny, V.

    1989-10-01

    A high-resolution scanning phase-measuring acoustic microscope (SPAM) has been developed and used to image the near-surface residual stress field around features etched in sputtered alumina via the acoustoelastic effect. This microscope operates at 670 MHz and has a resolution of 5-10 microns, depending upon the amount of defocus. Relative velocity changes of sample surface waves as small as 50 ppm are resolved. Images of the stress field at the tip of a 400-micron-wide slot etched in alumina are presented and compared with a finite element simulation. The SPAM uses an unconventional acoustic lens with an anisotropic illumination pattern which can measure anisotropic effects and map residual stress fields with several-micron resolution and a stress sensitivity of 1/3 MPa in an alumina film.

  9. Pattern recognition techniques applied to acoustic detection of liquid-metal fast breeder reactor cooling defects

    SciTech Connect

    Brunet, M.; Dubuisson, B.

    1983-08-01

    In the event of a partial or total blockage of a liquid-metal fast breeder reactor core subassembly, a boiling zone may be created. Acoustic signals from such a zone could provide a means of early detection of accident conditions. A three-step method, based on pattern recognition techniques, is described and used to analyze data from three experiments that simulate core cooling fault conditions. This method is shown to be capable of detecting the abnormal situation in each of the experiments analyzed.

  10. 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

  11. High Resolution X-Ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2006-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray source for mammography: Feasibility study...W81XWH-04-1-0481 TITLE: High Resolution X - ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement PRINCIPAL...REPORT TYPE Annual 3. DATES COVERED (From - To) 1 Jun 2005 – 31 May 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER High Resolution X - ray

  12. High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2005-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray ...high spatial coherence, such as synchrotrons 46, microfocus x - ray tubes 7, or laser plasma x - ray sources 8,9are employed is the phase contrast component...imaging apparatus to determine the deflection of the bead as a function of acoustic pressure. The x - rays , generated by a microfocus x - ray tube

  13. Acoustic radiation force impulse imaging for evaluation of renal parenchyma elasticity in diabetic nephropathy.

    PubMed

    Goya, Cemil; Kilinc, Faruk; Hamidi, Cihad; Yavuz, Alpaslan; Yildirim, Yasar; Cetincakmak, Mehmet Guli; Hattapoglu, Salih

    2015-02-01

    OBJECTIVE. The goal of this study is to evaluate the changes in the elasticity of the renal parenchyma in diabetic nephropathy using acoustic radiation force impulse imaging. SUBJECTS AND METHODS. The study included 281 healthy volunteers and 114 patients with diabetic nephropathy. In healthy volunteers, the kidney elasticity was assessed quantitatively by measuring the shear-wave velocity using acoustic radiation force impulse imaging based on age, body mass index, and sex. The changes in the renal elasticity were compared between the different stages of diabetic nephropathy and the healthy control group. RESULTS. In healthy volunteers, there was a statistically significant correlation between the shear-wave velocity values and age and sex. The shear-wave velocity values for the kidneys were 2.87, 3.14, 2.95, 2.68, and 2.55 m/s in patients with stage 1, 2, 3, 4, and 5 diabetic nephropathy, respectively, compared with 2.35 m/s for healthy control subjects. Acoustic radiation force impulse imaging was able to distinguish between the different diabetic nephropathy stages (except for stage 5) in the kidneys. The threshold value for predicting diabetic nephropathy was 2.43 m/s (sensitivity, 84.1%; specificity, 67.3%; positive predictive value, 93.1%; negative predictive value 50.8%; accuracy, 72.1%; positive likelihood ratio, 2.5; and negative likelihood ratio, 0.23). CONCLUSION. Acoustic radiation force impulse imaging could be used for the evaluation of the renal elasticity changes that are due to secondary structural and functional changes in diabetic nephropathy.

  14. High-resolution acoustic imaging at low frequencies using 3D-printed metamaterials

    NASA Astrophysics Data System (ADS)

    Laureti, S.; Hutchins, D. A.; Davis, L. A. J.; Leigh, S. J.; Ricci, M.

    2016-12-01

    An acoustic metamaterial has been constructed using 3D printing. It contained an array of air-filled channels, whose size and shape could be varied within the design and manufacture process. In this paper we analyze both numerically and experimentally the properties of this polymer metamaterial structure, and demonstrate its use for the imaging of a sample with sub-wavelength dimensions in the audible frequency range.

  15. Improvement of the imaging of moving acoustic sources by the knowledge of their motion

    NASA Astrophysics Data System (ADS)

    Hay, J.

    1981-03-01

    An analytical and experimental study is presented showing that, due to a more precise definition of nonstationary noises of a certain class, and to the preprocessing of microphone signals (termed 'coherent dedopplerization'), one can obtain acoustic imaging for sources whose velocity is greater than may be processed by conventional methods without the generation of blurrs of the same order as the antenna field. A useful application of these techniques would be to two-dimensional antennas.

  16. Contrast Enhancement for Thermal Acoustic Breast Cancer Imaging via Resonant Stimulation

    DTIC Science & Technology

    2008-03-01

    Wang, “Time-domain reconstruction for thermoa- coustic tomography in a speherical geometry,” IEEE Trans. Med. Imag., vol. 21, no. 7, pp. 814–822, Jul...comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS...excited into resonance via EM stimulation, the effective acoustic scattering cross-section may increase by a factor in excess of 100 based on

  17. Acoustic output of multi-line transmit beamforming for fast cardiac imaging: a simulation study.

    PubMed

    Santos, Pedro; Tong, Ling; Ortega, Alejandra; Løvstakken, Lasse; Samset, Eigil; D'hooge, Jan

    2015-07-01

    Achieving higher frame rates in cardiac ultrasound could unveil short-lived myocardial events and lead to new insights on cardiac function. Multi-line transmit (MLT) beamforming (i.e., simultaneously transmitting multiple focused beams) is a potential approach to achieve this. However, two challenges come with it: first, it leads to cross-talk between the MLT beams, appearing as imaging artifacts, and second, it presents acoustic summation in the near field, where multiple MLT beams overlap. Although several studies have focused on the former, no studies have looked into the implications of the latter on acoustic safety. In this paper, the acoustic field of 4-MLT was simulated and compared with single-line transmit (SLT). The findings suggest that standard MLT does present potential concerns. Compared with SLT, it shows a 2-fold increase in mechanical index (MI) (from 1.0 to 2.3), a 6-fold increase in spatial-peak pulse-average intensity (I(sppa)) (from 99 to 576 W∙cm(-2)) and a 12-fold increase in spatial-peak temporalaverage intensity (I(spta)) (from 119 to 1407 mW∙cm(-2)). Subsequently, modifications of the transmit pulse and delay line of MLT were studied. These modifications allowed for a change in the spatio-temporal distribution of the acoustic output, thereby significantly decreasing the safety indices (MI = 1.2, I(sppa) = 92 W∙cm(-2) and I(spta) = 366 mW∙cm(-2)). Accordingly, they help mitigate the concerns around MLT, reducing potential tradeoffs between acoustic safety and image quality.

  18. 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

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

    PubMed

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

    2015-10-07

    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.

  20. 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

  1. 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.

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

    PubMed

    Zourmand, Alireza; Mirhassani, Seyed Mostafa; Ting, Hua-Nong; Bux, Shaik Ismail; Ng, Kwan Hoong; Bilgen, Mehmet; Jalaludin, Mohd Amin

    2014-07-25

    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.

  3. Iterative electromagnetic Born inversion applied to earth conductivity imaging

    SciTech Connect

    Alumbaugh, David Lee

    1993-08-01

    This thesis investigates the use of a fast imaging technique to deduce the spatial conductivity distribution in the earth from low frequency (< 1 MHz), cross well electromagnetic (EM) measurements. The theory embodied in this work is the extension of previous strategies and is based on the Born series approximation to solve both the forward and inverse problem. Nonlinear integral equations are employed to derive the series expansion which accounts for the scattered magnetic fields that are generated by inhomogeneities embedded in either a homogenous or a layered earth. A sinusoidally oscillating, vertically oriented magnetic dipole is employed as a source, and it is assumed that the scattering bodies are azimuthally symmetric about the source dipole axis. The use of this model geometry reduces the 3-D vector problem to a more manageable 2-D scalar form. The validity of the cross well EM method is tested by applying the imaging scheme to two sets of field data. Images of the data collected at the Devine, Texas test site show excellent correlation with the well logs. Unfortunately there is a drift error present in the data that limits the accuracy of the results. A more complete set of data collected at the Richmond field station in Richmond, California demonstrates that cross well EM can be successfully employed to monitor the position of an injected mass of salt water. Both the data and the resulting images clearly indicate the plume migrates toward the north-northwest. The plausibility of these conclusions is verified by applying the imaging code to synthetic data generated by a 3-D sheet model.

  4. Perceptual thresholds for detecting modifications applied to the acoustical properties of a violin.

    PubMed

    Fritz, Claudia; Cross, Ian; Moore, Brian C J; Woodhouse, Jim

    2007-12-01

    This study is the first step in the psychoacoustic exploration of perceptual differences between the sounds of different violins. A method was used which enabled the same performance to be replayed on different "virtual violins," so that the relationships between acoustical characteristics of violins and perceived qualities could be explored. Recordings of real performances were made using a bridge-mounted force transducer, giving an accurate representation of the signal from the violin string. These were then played through filters corresponding to the admittance curves of different violins. Initially, limits of listener performance in detecting changes in acoustical characteristics were characterized. These consisted of shifts in frequency or increases in amplitude of single modes or frequency bands that have been proposed previously to be significant in the perception of violin sound quality. Thresholds were significantly lower for musically trained than for nontrained subjects but were not significantly affected by the violin used as a baseline. Thresholds for the musicians typically ranged from 3 to 6 dB for amplitude changes and 1.5%-20% for frequency changes. Interpretation of the results using excitation patterns showed that thresholds for the best subjects were quite well predicted by a multichannel model based on optimal processing.

  5. 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.

  6. Bragg Coherent Diffractive Imaging of Zinc Oxide Acoustic Phonons at Picosecond Timescales

    DOE PAGES

    Ulvestad, A.; Cherukara, M. J.; Harder, R.; ...

    2017-08-29

    Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4Dmore » evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. Lastly, we find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.« less

  7. Bragg Coherent Diffractive Imaging of Zinc Oxide Acoustic Phonons at Picosecond Timescales.

    PubMed

    Ulvestad, A; Cherukara, M J; Harder, R; Cha, W; Robinson, I K; Soog, S; Nelson, S; Zhu, D; Stephenson, G B; Heinonen, O; Jokisaari, A

    2017-08-29

    Mesoscale thermal transport is of fundamental interest and practical importance in materials such as thermoelectrics. Coherent lattice vibrations (acoustic phonons) govern thermal transport in crystalline solids and are affected by the shape, size, and defect density in nanoscale materials. The advent of hard x-ray free electron lasers (XFELs) capable of producing ultrafast x-ray pulses has significantly impacted the understanding of acoustic phonons by enabling their direct study with x-rays. However, previous studies have reported ensemble-averaged results that cannot distinguish the impact of mesoscale heterogeneity on the phonon dynamics. Here we use Bragg coherent diffractive imaging (BCDI) to resolve the 4D evolution of the acoustic phonons in a single zinc oxide rod with a spatial resolution of 50 nm and a temporal resolution of 25 picoseconds. We observe homogeneous (lattice breathing/rotation) and inhomogeneous (shear) acoustic phonon modes, which are compared to finite element simulations. We investigate the possibility of changing phonon dynamics by altering the crystal through acid etching. We find that the acid heterogeneously dissolves the crystal volume, which will significantly impact the phonon dynamics. In general, our results represent the first step towards understanding the effect of structural properties at the individual crystal level on phonon dynamics.

  8. 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.

  9. Dragon Ears airborne acoustic array: CSP analysis applied to cross array to compute real-time 2D acoustic sound field

    NASA Astrophysics Data System (ADS)

    Cerwin, Steve; Barnes, Julie; Kell, Scott; Walters, Mark

    2003-09-01

    This paper describes development and application of a novel method to accomplish real-time solid angle acoustic direction finding using two 8-element orthogonal microphone arrays. The developed prototype system was intended for localization and signature recognition of ground-based sounds from a small UAV. Recent advances in computer speeds have enabled the implementation of microphone arrays in many audio applications. Still, the real-time presentation of a two-dimensional sound field for the purpose of audio target localization is computationally challenging. In order to overcome this challenge, a crosspower spectrum phase1 (CSP) technique was applied to each 8-element arm of a 16-element cross array to provide audio target localization. In this paper, we describe the technique and compare it with two other commonly used techniques; Cross-Spectral Matrix2 and MUSIC3. The results show that the CSP technique applied to two 8-element orthogonal arrays provides a computationally efficient solution with reasonable accuracy and tolerable artifacts, sufficient for real-time applications. Additional topics include development of a synchronized 16-channel transmitter and receiver to relay the airborne data to the ground-based processor and presentation of test data demonstrating both ground-mounted operation and airborne localization of ground-based gunshots and loud engine sounds.

  10. Hyperspectral-imaging-based techniques applied to wheat kernels characterization

    NASA Astrophysics Data System (ADS)

    Serranti, Silvia; Cesare, Daniela; Bonifazi, Giuseppe

    2012-05-01

    Single kernels of durum wheat have been analyzed by hyperspectral imaging (HSI). Such an approach is based on the utilization of an integrated hardware and software architecture able to digitally capture and handle spectra as an image sequence, as they results along a pre-defined alignment on a surface sample properly energized. The study was addressed to investigate the possibility to apply HSI techniques for classification of different types of wheat kernels: vitreous, yellow berry and fusarium-damaged. Reflectance spectra of selected wheat kernels of the three typologies have been acquired by a laboratory device equipped with an HSI system working in near infrared field (1000-1700 nm). The hypercubes were analyzed applying principal component analysis (PCA) to reduce the high dimensionality of data and for selecting some effective wavelengths. Partial least squares discriminant analysis (PLS-DA) was applied for classification of the three wheat typologies. The study demonstrated that good classification results were obtained not only considering the entire investigated wavelength range, but also selecting only four optimal wavelengths (1104, 1384, 1454 and 1650 nm) out of 121. The developed procedures based on HSI can be utilized for quality control purposes or for the definition of innovative sorting logics of wheat.

  11. Tunable far-field acoustic imaging by two-dimensional sonic crystal with concave incident surface

    NASA Astrophysics Data System (ADS)

    Shen, Feng-Fu; Lu, Dan-Feng; Zhu, Hong-Wei; Ji, Chang-Ying; Shi, Qing-Fan

    2017-01-01

    An additional concave incident surface comprised of two-dimensional (2D) sonic crystals (SCs) is employed to tune the acoustic image in the far-field region. The tunability is realized through changing the curvature of the concave surface. To explain the tuning mechanism, a simple ray-trace analysis is demonstrated based on the wave-beam negative refractive law. Then, a numerical confirmation is carried out. Results show that both the position and the intensity of the image can be tuned by the introduced concave surface.

  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. Digital Image Processing Applied To Problems In Art And Archaeology

    NASA Astrophysics Data System (ADS)

    Asmus, John F.; Katz, Norman P.

    1988-12-01

    Many of the images encountered during scholarly studies in the fields of art and archaeology have deteriorated through the effects of time. The Ice-Age rock art of the now-closed caves near Lascaux are prime examples of this fate. However, faint and subtle details of these can be exceedingly important as some theories suggest that the designs are computers or calendars pertaining to astronomical cycles as well as seasons for hunting, gathering, and planting. Consequently, we have applied a range of standard image processing algorithms (viz., edge detection, spatial filtering, spectral differencing, and contrast enhancement) as well as specialized techniques (e.g., matched filters) to the clarification of these drawings. Also, we report the results of computer enhancement studies pertaining to authenticity, faint details, sitter identity, and age of portraits by da Vinci, Rembrandt, Rotari, and Titian.

  14. Autoionization widths by Stieltjes imaging applied to Lanczos pseudospectra

    SciTech Connect

    Kopelke, S.; Gokhberg, K.; Cederbaum, L. S.; Tarantelli, F.; Averbukh, V.

    2011-01-14

    Excited states of atoms and molecules lying above the ionization threshold can decay by electron emission in a process commonly known as autoionization. The autoionization widths can be calculated conveniently using Fano formalism and discretized atomic and molecular spectra by a standard procedure referred to as Stieltjes imaging. The Stieltjes imaging procedure requires the use of the full discretized spectrum of the final states of the autoionization, making its use for poly-atomic systems described by high-quality basis sets impractical. Following our previous work on photoionization cross-sections, here we show that also in the case of autoionization widths, the full diagonalization bottleneck can be overcome by the use of Lanczos pseudospectra. We test the proposed method by calculating the well-documented autoionization widths of inner-valence-excited neon and apply the new technique to autoionizing states of hydrofluoric acid and benzene.

  15. Improved PCA + LDA Applies to Gastric Cancer Image Classification Process

    NASA Astrophysics Data System (ADS)

    Gan, Lan; Lv, Wenya; Zhang, Xu; Meng, Xiuming

    Principal component analysis (PCA) and linear discriminant analysis (LDA) are two most widely used pattern recognition methods in the field of feature extraction,while PCA + LDA is often used in image recognition.Here,we apply PCA + LDA to gastric cancer image feature classification, but the traditional PCA + LDA dimension reduction method has good effect on the training sample dimensionality and clustering, the effect on test samples dimension reduction and clustering is very poor, that is, the traditional PCA + LDA exists Generalization problem on the test samples. To solve this problem, this paper proposes an improved PCA + LDA method, which mainly considers from the LDA transform; improves the traditional PCA + LDA;increase the generalization performance of LDA on test samples and increases the classification accuracy on test samples. The experiment proves that the method can achieve good clustering.

  16. Comparison of Modal Analysis Methods Applied to a Vibro-Acoustic Test Article

    NASA Technical Reports Server (NTRS)

    Pritchard, Jocelyn; Pappa, Richard; Buehrle, Ralph; Grosveld, Ferdinand

    2001-01-01

    Modal testing of a vibro-acoustic test article referred to as the Aluminum Testbed Cylinder (ATC) has provided frequency response data for the development of validated numerical models of complex structures for interior noise prediction and control. The ATC is an all aluminum, ring and stringer stiffened cylinder, 12 feet in length and 4 feet in diameter. The cylinder was designed to represent typical aircraft construction. Modal tests were conducted for several different configurations of the cylinder assembly under ambient and pressurized conditions. The purpose of this paper is to present results from dynamic testing of different ATC configurations using two modal analysis software methods: Eigensystem Realization Algorithm (ERA) and MTS IDEAS Polyreference method. The paper compares results from the two analysis methods as well as the results from various test configurations. The effects of pressurization on the modal characteristics are discussed.

  17. Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography.

    PubMed

    Jin, Xing; Li, Changhui; Wang, Lihong V

    2008-07-01

    The effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacoustic waves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and brain tissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brain images when the thickness of the skull cannot be ignored. © 2008 American Association of Physicists in Medicine.

  18. Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography

    PubMed Central

    Jin, Xing; Li, Changhui; Wang, Lihong V.

    2008-01-01

    The effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacoustic waves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and brain tissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brain images when the thickness of the skull cannot be ignored. PMID:18697545

  19. Effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography.

    PubMed

    Jin, Xing; Li, Changhui; Wang, Lihong V

    2008-07-01

    The effects of acoustic heterogeneities on transcranial brain imaging with microwave-induced thermoacoustic tomography were studied. A numerical model for calculating the propagation of thermoacoustic waves through the skull was developed and experimentally examined. The model takes into account wave reflection and refraction at the skull surfaces and therefore provides improved accuracy for the reconstruction. To evaluate when the skull-induced effects could be ignored in reconstruction, the reconstructed images obtained by the proposed method were further compared with those obtained with the method based on homogeneous acoustic properties. From simulation and experimental results, it was found that when the target region is close to the center of the brain, the effects caused by the skull layer are minimal and both reconstruction methods work well. As the target region becomes closer to the interface between the skull and brain tissue, however, the skull-induced distortion becomes increasingly severe, and the reconstructed image would be strongly distorted without correcting those effects. In this case, the proposed numerical method can improve image quality by taking into consideration the wave refraction and mode conversion at the skull surfaces. This work is important for obtaining good brain images when the thickness of the skull cannot be ignored.

  20. Acoustic radiation force impulse imaging (ARFI) on an IVUS circular array.

    PubMed

    Patel, Vivek; Dahl, Jeremy J; Bradway, David P; Doherty, Joshua R; Lee, Seung Yun; Smith, Stephen W

    2014-04-01

    Our long-term goal is the detection and characterization of vulnerable plaque in the coronary arteries of the heart using intravascular ultrasound (IVUS) catheters. Vulnerable plaque, characterized by a thin fibrous cap and a soft, lipid-rich necrotic core is a precursor to heart attack and stroke. Early detection of such plaques may potentially alter the course of treatment of the patient to prevent ischemic events. We have previously described the characterization of carotid plaques using external linear arrays operating at 9 MHz. In addition, we previously modified circular array IVUS catheters by short-circuiting several neighboring elements to produce fixed beamwidths for intravascular hyperthermia applications. In this paper, we modified Volcano Visions 8.2 French, 9 MHz catheters and Volcano Platinum 3.5 French, 20 MHz catheters by short-circuiting portions of the array for acoustic radiation force impulse imaging (ARFI) applications. The catheters had an effective transmit aperture size of 2 mm and 1.5 mm, respectively. The catheters were connected to a Verasonics scanner and driven with pushing pulses of 180 V p-p to acquire ARFI data from a soft gel phantom with a Young's modulus of 2.9 kPa. The dynamic response of the tissue-mimicking material demonstrates a typical ARFI motion of 1 to 2 microns as the gel phantom displaces away and recovers back to its normal position. The hardware modifications applied to our IVUS catheters mimic potential beamforming modifications that could be implemented on IVUS scanners. Our results demonstrate that the generation of radiation force from IVUS catheters and the development of intravascular ARFI may be feasible.

  1. Modulation of Radio Frequency Signals by Nonlinearly Generated Acoustic Fields

    DTIC Science & Technology

    2014-01-01

    techniques have been applied in the fields of acoustic holography and imaging. Williams and Maynard [165–168] introduced the concept of near-field 72...acoustic holography (NAH) as a means of reconstructing the acoustic pressure on the surface of a radiating structure from near-field data. Typically...the field of acoustic holography and could provide useful results for application in object detection and biomedical research. An analytical solution

  2. 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.

  3. Acoustic Radiation Force Impulse Imaging of Mechanical Stiffness Propagation in Myocardial Tissue

    PubMed Central

    Hsu, Stephen J.; Byram, Brett C.; Bouchard, Richard R.; Dumont, Douglas M.; Wolf, Patrick D.; Trahey, Gregg E.

    2012-01-01

    Acoustic radiation force impulse (ARFI) imaging has been shown to be capable of imaging local myocardial stiffness changes throughout the cardiac cycle. Expanding on these results, the authors present experiments using cardiac ARFI imaging to visualize and quantify the propagation of mechanical stiffness during ventricular systole. In vivo ARFI images of the left ventricular free wall of two exposed canine hearts were acquired. Images were formed while the heart was externally paced by one of two electrodes positioned on the epicardial surface and either side of the imaging plane. Two-line M-mode ARFI images were acquired at a sampling frequency of 120 Hz while the heart was paced from an external stimulating electrode. Two-dimensional ARFI images were also acquired, and an average propagation velocity across the lateral field of view was calculated. Directions and speeds of myocardial stiffness propagation were measured and compared with the propagations derived from the local electrocardiogram (ECG), strain, and tissue velocity measurements estimated during systole. In all ARFI images, the direction of myocardial stiffness propagation was seen to be away from the stimulating electrode and occurred with similar velocity magnitudes in either direction. When compared with the local epicardial ECG, the mechanical stiffness waves were observed to travel in the same direction as the propagating electrical wave and with similar propagation velocities. In a comparison between ARFI, strain, and tissue velocity imaging, the three methods also yielded similar propagation velocities. PMID:22972912

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Full-wave iterative image reconstruction in photoacoustic tomography with acoustically inhomogeneous media.

    PubMed

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

    2013-06-01

    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.

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

    PubMed

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

    2016-03-01

    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.

  10. Hyperspectral imaging applied to complex particulate solids systems

    NASA Astrophysics Data System (ADS)

    Bonifazi, Giuseppe; Serranti, Silvia

    2008-04-01

    HyperSpectral Imaging (HSI) is based on the utilization of an integrated hardware and software (HW&SW) platform embedding conventional imaging and spectroscopy to attain both spatial and spectral information from an object. Although HSI was originally developed for remote sensing, it has recently emerged as a powerful process analytical tool, for non-destructive analysis, in many research and industrial sectors. The possibility to apply on-line HSI based techniques in order to identify and quantify specific particulate solid systems characteristics is presented and critically evaluated. The originally developed HSI based logics can be profitably applied in order to develop fast, reliable and lowcost strategies for: i) quality control of particulate products that must comply with specific chemical, physical and biological constraints, ii) performance evaluation of manufacturing strategies related to processing chains and/or realtime tuning of operative variables and iii) classification-sorting actions addressed to recognize and separate different particulate solid products. Case studies, related to recent advances in the application of HSI to different industrial sectors, as agriculture, food, pharmaceuticals, solid waste handling and recycling, etc. and addressed to specific goals as contaminant detection, defect identification, constituent analysis and quality evaluation are described, according to authors' originally developed application.

  11. 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.

  12. Investigation of acoustic changes resulting from contrast enhancement in through-transmission ultrasonic imaging.

    PubMed

    Rothstein, Tamara; Gaitini, Diana; Gallimidi, Zahava; Azhari, Haim

    2010-09-01

    Through-transmitted ultrasonic waves can be used for computed projection imaging of the breast. The goal of this research was to analyze the acoustic properties changes associated with the propagation of ultrasonic waves through media before and after ultrasound contrast agent (UCA) injection and to study the feasibility of a new imaging method combining projection imaging and UCA. Two transmission techniques were examined: Gaussian pulses and pulse inversion. In the latter, three different double inverted pulses were studied: double Gaussian, double square and double sine. A computerized automatic ultrasonic scanning system was used for imaging. To simulate blood vessels, a phantom, consisting of a latex tube through which saline was circulated, was assembled. The phantom was placed within the scanner and sets of acoustic projection images were acquired. Then, a suspension of the UCA Definitely was added to the saline and a new set of images was obtained. The pre and postcontrast images were quantitatively compared in terms of amplitude and time-of-flight (TOF). In addition, nonlinearity was evaluated by comparing the relative alteration of the positive and negative parts of the signal. Statistically significant (p < 0.001) changes in the projection images resulting from the UCA injection were observed in wave amplitude (22% +/- 13%), TOF (7.9 ns +/- 6.3 ns) and nonlinear properties (35% +/- 32% and 56% +/- 17% for Gausian pulses and pulse inversion, respectively). One in vivo study of a female breast is also presented and its preliminary outcomes discussed. Together, these results indicate the technical feasibility of the suggested method and its potential to detect breast tumors.

  13. 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.

  14. Acoustic characterization and contrast imaging of microbubbles encapsulated by polymeric shells coated or filled with magnetic nanoparticles.

    PubMed

    Sciallero, Claudia; Grishenkov, Dmitry; Kothapalli, Satya V V N; Oddo, Letizia; Trucco, Andrea

    2013-11-01

    The combination of superparamagnetic iron oxide nanoparticles with polymeric air-filled microbubbles is used to produce two types of multimodal contrast agents to enhance medical ultrasound and magnetic resonance imaging. The nanoparticles are either covalently linked to the shell or physically entrapped into the shell. In this paper, the characterization of the acoustic properties (backscattered power, fracturing pressure, attenuation and dispersion of the ultrasonic wave) and ultrasound imaging of the two types of magnetic microbubbles are presented. In vitro B-mode images are generated using a medical ultrasound scanner by applying a nonconventional signal processing technique that is suitable to detect polymeric bubbles and based on the combination of multipulse excitation and chirp coding. Even if both types of microbubbles can be considered to be effective ultrasound contrast agents, the different structure of the shell loaded with nanoparticles has a pronounced effect on the echogenicity and the detection sensitivity of the imaging technique. The best results are obtained using microbubbles that are externally coated with nanoparticles. A backscattered power of 20 dB was achieved at lower concentration, and an increment of 8 dB in the contrast-to-tissue ratio was observed with respect to the more rigid microbubbles with particles entrapped into the shell.

  15. Investigation of Volcanic Seismo-Acoustic Signals: Applying Subspace Detection to Lava Fountain Activity at Etna Volcano

    NASA Astrophysics Data System (ADS)

    Sciotto, M.; Rowe, C. A.; Cannata, A.; Arrowsmith, S.; Privitera, E.; Gresta, S.

    2011-12-01

    The current eruption of Mount Etna, which began in January, 2011, has produced numerous energetic episodes of lava fountaining, which have bee recorded by the INGV seismic and acoustic sensors located on and around the volcano. The source of these events was the pit crater on the east flank of the Southeast crater of Etna. Simultaneously, small levels of activity were noted in the Bocca Nuova as well, prior to its lava fountaining activity. We will present an analysis of seismic and acoustic signals related to the 2011 activity wherein we apply the method of subspace detection to determine whether the source exhibits a temporal evolution within or between fountaining events, or otherwise produces repeating, classifiable events occurring through the continuous explosive degassing. We will examine not only the raw waveforms, but also spectral variations in time as well as time-varying statistical functions such as signal skewness and kurtosis. These results will be compared to straightforward cross-correlation analysis. In addition to classification performance, the subspace method has promise to outperform standard STA/LTA methods for real-time event detection in cases where similar events can be expected.

  16. Acoustic Emission and Echo Signal Compensation Techniques Applied to an Ultrasonic Logging-While-Drilling Caliper

    PubMed Central

    Yao, Yongchao; Ju, Xiaodong; Lu, Junqiang; Men, Baiyong

    2017-01-01

    A logging-while-drilling (LWD) caliper is a tool used for the real-time measurement of a borehole diameter in oil drilling engineering. This study introduces the mechanical structure and working principle of a new LWD caliper based on ultrasonic distance measurement (UDM). The detection range is a major performance index of a UDM system. This index is determined by the blind zone length and remote reflecting interface detection capability of the system. To reduce the blind zone length and detect near the reflecting interface, a full bridge acoustic emission technique based on bootstrap gate driver (BGD) and metal-oxide-semiconductor field effect transistor (MOSFET) is designed by analyzing the working principle and impedance characteristics of a given piezoelectric transducer. To detect the remote reflecting interface and reduce the dynamic range of the received echo signals, the relationships between the echo amplitude and propagation distance of ultrasonic waves are determined. A signal compensation technique based on time-varying amplification theory, which can automatically change the gain according to the echo arrival time is designed. Lastly, the aforementioned techniques and corresponding circuits are experimentally verified. Results show that the blind zone length in the UDM system of the LWD caliper is significantly reduced and the capability to detect the remote reflecting interface is considerably improved. PMID:28604603

  17. Neural network method applied to particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Grant, Ian; Pan, X.

    1993-12-01

    realised. An important class of neural network is the multi-layer perceptron. The neurons are distributed on surfaces and linked by weighted interconnections. In the present paper we demonstrate how this type of net can developed into a competitive, adaptive filter which will identify PIV image pairs in a number of commonly occurring flow types. Previous work by the authors in particle tracking analysis (1, 2) has shown the efficiency of statistical windowing techniques in flows without systematic (in time or space) variations. The effectiveness of the present neural net is illustrated by applying it to digital simulations ofturbulent and rotating flows. Work reported by Cenedese et al (3) has taken a different approach in examining the potential for neural net methods applied to PIV.

  18. Acoustic radiation force impulse imaging of human prostates: initial in vivo demonstration.

    PubMed

    Zhai, Liang; Polascik, Thomas J; Foo, Wen-Chi; Rosenzweig, Stephen; Palmeri, Mark L; Madden, John; Nightingale, Kathryn R

    2012-01-01

    Reliably detecting prostate cancer (PCa) has been a challenge for current imaging modalities. Acoustic radiation force impulse (ARFI) imaging is an elasticity imaging method that uses remotely generated, focused acoustic beams to probe tissue stiffness. A previous study on excised human prostates demonstrated ARFI images portray various prostatic structures and has the potential to guide prostate needle biopsy with improved sampling accuracy. The goal of this study is to demonstrate the feasibility of ARFI imaging to portray internal structures and PCa in the human prostate in vivo. Custom ARFI imaging sequences were designed and implemented using a modified Siemens Antares™ scanner with a three-dimensional (3-D) wobbler, end-firing, trans-cavity transducer, EV9F4. Nineteen patients were consented and imaged immediately preceding surgical prostatectomy. Pathologies and anatomic structures were identified in histologic slides by a pathologist blinded to ARFI data and were then registered with structures found in ARFI images. The results demonstrated that when PCa is visible, it generally appears as bilaterally asymmetric stiff structures; benign prostatic hyperplasia (BPH) appears heterogeneous with a nodular texture; the verumontanum and ejaculatory ducts appears softer compared with surrounding tissue, which form a unique 'V' shape; and the boundary of the transitional zone (TZ) forms a stiff rim separating the TZ from the peripheral zone (PZ). These characteristic appearances of prostatic structures are consistent with those found in our previous study of prostate ARFI imaging on excised human prostates. Compared with the matched B-mode images, ARFI images, in general, portray prostate structures with higher contrast. With the end-firing transducer used for this study, ARFI depth penetration was limited to 22 mm. Image contrast and resolution were decreased as compared with the previous ex vivo study due to the small transducer aperture. Even with these

  19. Image processing applied to measurement of particle size

    NASA Astrophysics Data System (ADS)

    Vega, Fabio; Lasso, Willian; Torres, Cesar

    2015-01-01

    Five different types of aggregates have been analyzed, and the size of particles on samples immersed in distilled water as silicon dioxide, titanium dioxide, styrenes and crushed silica particles is made; an attempt at applying the digital image processing (DIP) technique to analyze the particle size, we developed a system of measures microparticles using a microscope, a CCD camera and acquisition software and video processing developed in MATLAB. These studies are combined with laser light using measurements by diffractometry and obtain calibration in the system implemented, in this work we achievement measurement particle size on the order of 4 to 6 micrometers. The study demonstrates that DIP is a fast, convenient, versatile, and accurate technique for particle size analysis; the limitations of implemented setup too will be discussed.

  20. Air-coupled acoustic thermography for in-situ evaluation

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N. (Inventor); Winfree, William P. (Inventor); Yost, William T. (Inventor)

    2010-01-01

    Acoustic thermography uses a housing configured for thermal, acoustic and infrared radiation shielding. For in-situ applications, the housing has an open side adapted to be sealingly coupled to a surface region of a structure such that an enclosed chamber filled with air is defined. One or more acoustic sources are positioned to direct acoustic waves through the air in the enclosed chamber and towards the surface region. To activate and control each acoustic source, a pulsed signal is applied thereto. An infrared imager focused on the surface region detects a thermal image of the surface region. A data capture device records the thermal image in synchronicity with each pulse of the pulsed signal such that a time series of thermal images is generated. For enhanced sensitivity and/or repeatability, sound and/or vibrations at the surface region can be used in feedback control of the pulsed signal applied to the acoustic sources.

  1. 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

  2. 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.

  3. Time domain localization technique with sparsity constraint for imaging acoustic sources

    NASA Astrophysics Data System (ADS)

    Padois, Thomas; Doutres, Olivier; Sgard, Franck; Berry, Alain

    2017-09-01

    This paper addresses source localization technique in time domain for broadband acoustic sources. The objective is to accurately and quickly detect the position and amplitude of noise sources in workplaces in order to propose adequate noise control options and prevent workers hearing loss or safety risk. First, the generalized cross correlation associated with a spherical microphone array is used to generate an initial noise source map. Then a linear inverse problem is defined to improve this initial map. Commonly, the linear inverse problem is solved with an l2 -regularization. In this study, two sparsity constraints are used to solve the inverse problem, the orthogonal matching pursuit and the truncated Newton interior-point method. Synthetic data are used to highlight the performances of the technique. High resolution imaging is achieved for various acoustic sources configurations. Moreover, the amplitudes of the acoustic sources are correctly estimated. A comparison of computation times shows that the technique is compatible with quasi real-time generation of noise source maps. Finally, the technique is tested with real data.

  4. 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.

  5. Sparsity-based acoustic inversion in cross-sectional multiscale optoacoustic imaging

    SciTech Connect

    Han, Yiyong; Tzoumas, Stratis; Nunes, Antonio; Ntziachristos, Vasilis; Rosenthal, Amir

    2015-09-15

    Purpose: With recent advancement in hardware of optoacoustic imaging systems, highly detailed cross-sectional images may be acquired at a single laser shot, thus eliminating motion artifacts. Nonetheless, other sources of artifacts remain due to signal distortion or out-of-plane signals. The purpose of image reconstruction algorithms is to obtain the most accurate images from noisy, distorted projection data. Methods: In this paper, the authors use the model-based approach for acoustic inversion, combined with a sparsity-based inversion procedure. Specifically, a cost function is used that includes the L1 norm of the image in sparse representation and a total variation (TV) term. The optimization problem is solved by a numerically efficient implementation of a nonlinear gradient descent algorithm. TV–L1 model-based inversion is tested in the cross section geometry for numerically generated data as well as for in vivo experimental data from an adult mouse. Results: In all cases, model-based TV–L1 inversion showed a better performance over the conventional Tikhonov regularization, TV inversion, and L1 inversion. In the numerical examples, the images reconstructed with TV–L1 inversion were quantitatively more similar to the originating images. In the experimental examples, TV–L1 inversion yielded sharper images and weaker streak artifact. Conclusions: The results herein show that TV–L1 inversion is capable of improving the quality of highly detailed, multiscale optoacoustic images obtained in vivo using cross-sectional imaging systems. As a result of its high fidelity, model-based TV–L1 inversion may be considered as the new standard for image reconstruction in cross-sectional imaging.

  6. Reconstruction of an acoustic pressure field in a resonance tube by particle image velocimetry.

    PubMed

    Kuzuu, K; Hasegawa, S

    2015-11-01

    A technique for estimating an acoustic field in a resonance tube is suggested. The estimation of an acoustic field in a resonance tube is important for the development of the thermoacoustic engine, and can be conducted employing two sensors to measure pressure. While this measurement technique is known as the two-sensor method, care needs to be taken with the location of pressure sensors when conducting pressure measurements. In the present study, particle image velocimetry (PIV) is employed instead of a pressure measurement by a sensor, and two-dimensional velocity vector images are extracted as sequential data from only a one- time recording made by a video camera of PIV. The spatial velocity amplitude is obtained from those images, and a pressure distribution is calculated from velocity amplitudes at two points by extending the equations derived for the two-sensor method. By means of this method, problems relating to the locations and calibrations of multiple pressure sensors are avoided. Furthermore, to verify the accuracy of the present method, the experiments are conducted employing the conventional two-sensor method and laser Doppler velocimetry (LDV). Then, results by the proposed method are compared with those obtained with the two-sensor method and LDV.

  7. Acoustic radiation contrast in MR images for breast cancer diagnostics--initial phantom study.

    PubMed

    Radicke, M; Mende, J; Kofahl, A-L; Wild, J; Ulucay, D; Habenstein, B; Deimling, M; Trautner, P; Weber, B; Maier, K

    2011-02-01

    Acoustic radiation contrast in magnetic resonance images is an approach to visualize the changes in ultrasonic loss and viscoelastic changes of the sample with the resolution of a magnetic resonance imaging (MRI) system. By irradiating ultrasound (US) into a tissue-mimicking sample, a displacement along the US beam path caused by the acoustic radiation force is obtained. This displacement varies with the US intensity, the duration of irradiation, the US attenuation and the viscoelastic properties of the sample. US pulses of 2.5 MHz with a duration of 20 ms and an intensity of <17 W/cm(2) are used. An MRI sequence was programmed to produce images in which the magnitude of the displacement is visualized by gray value changes. In addition, a finite element simulation of the measurements was performed to demonstrate the feasibility of the method. Through examination of the measurements and the simulations, information about viscoelastic changes was achieved. In this work, measurements on different breast phantoms are presented. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Near-field transport imaging applied to photovoltaic materials

    DOE PAGES

    Xiao, Chuanxiao; Jiang, Chun -Sheng; Moseley, John; ...

    2017-05-26

    We developed and applied a new analytical technique - near-field transport imaging (NF-TI or simply TI) - to photovoltaic materials. Charge-carrier transport is an important factor in solar cell performance, and TI is an innovative approach that integrates a scanning electron microscope with a near-field scanning optical microscope, providing the possibility to study luminescence associated with recombination and transport with high spatial resolution. In this paper, we describe in detail the technical barriers we had to overcome to develop the technique for routine application and the data-fitting procedure used to calculate minority-carrier diffusion length values. The diffusion length measured bymore » TI agrees well with the results calculated by time-resolved photoluminescence on well-controlled gallium arsenide (GaAs) thin-film samples. We report for the first time on measurements on thin-film cadmium telluride using this technique, including the determination of effective carrier diffusion length, as well as the first near-field imaging of the effect of a single localized defect on carrier transport and recombination in a GaAs heterostructure. Furthermore, by changing the scanning setup, we were able to demonstrate near-field cathodoluminescence (CL), and correlated the results with standard CL measurements. In conclusion, the TI technique shows great potential for mapping transport properties in solar cell materials with high spatial resolution.« less

  9. APPLYING A SPATIOTEMPORAL MODEL FOR LONGITUDINAL CARDIAC IMAGING DATA

    PubMed Central

    George, Brandon; Denney, Thomas; Gupta, Himanshu; Dell’Italia, Louis; Aban, Inmaculada

    2016-01-01

    Longitudinal imaging studies have both spatial and temporal correlation among the multiple outcome measurements from a subject. Statistical methods of analysis must properly account for this autocorrelation. In this work we discuss how a linear model with a separable parametric correlation structure could be used to analyze data from such a study. The goal of this paper is to provide an easily understood description of how such a model works and discuss how it can be applied to real data. Model assumptions are discussed and the process of selecting a working correlation structure is thoroughly discussed. The steps necessitating collaboration between statistical and scientific investigators have been highlighted, as have considerations for missing data or uneven follow-up. The results from a completed longitudinal cardiac imaging study were considered for illustration purposes. The data comes from a clinical trial for medical therapy for patients with mitral regurgitation, with repeated measurements taken at sixteen locations from the left ventricle to measure disease progression. The spatiotemporal correlation model was compared to previously used summary measures to demonstrate improved power as well as increased flexibility in the use of time- and space-varying predictors. PMID:27087884

  10. 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.

  11. Liver fibrosis in viral hepatitis: noninvasive assessment with acoustic radiation force impulse imaging versus transient elastography.

    PubMed

    Friedrich-Rust, Mireen; Wunder, Katrin; Kriener, Susanne; Sotoudeh, Fariba; Richter, Swantje; Bojunga, Joerg; Herrmann, Eva; Poynard, Thierry; Dietrich, Christoph F; Vermehren, Johannes; Zeuzem, Stefan; Sarrazin, Christoph

    2009-08-01

    To compare, in a pilot study, acoustic radiation force impulse (ARFI) imaging technology integrated into a conventional ultrasonography (US) system with both transient elastography (TE) and serologic fibrosis marker testing for the noninvasive assessment of liver fibrosis. Informed consent was obtained from all subjects, and the local ethics committee approved the study. ARFI imaging involved the mechanical excitation of tissue with use of short-duration acoustic pulses to generate localized displacements in tissue. The displacements resulted in shear-wave propagation, which was tracked by using US correlation-based methods and recorded in meters per second. Eighty-six patients with chronic viral hepatitis underwent TE, ARFI imaging, and serum fibrosis marker testing. Results were compared with liver biopsy findings, which served as the reference standard. ARFI imaging (rho = 0.71), TE (rho = 0.73), and serum fibrosis marker test (rho = 0.66) results correlated significantly with histologic fibrosis stage (P < .001). Median ARFI velocities ranged from 0.84 to 3.83 m/sec. Areas under the receiver operating characteristic curve for the accuracy of ARFI imaging, TE, and serum fibrosis marker testing were 0.82, 0.84, and 0.82, respectively, for the diagnosis of moderate fibrosis (histologic fibrosis stage, > or = 2) and 0.91, 0.91, and 0.82, respectively, for the diagnosis of cirrhosis. ARFI imaging is a promising US-based method for assessing liver fibrosis in chronic viral hepatitis, with diagnostic accuracy comparable to that of TE in this preliminary study. http://radiology.rsnajnls.org/cgi/content/full/252/2/595/DC1.

  12. 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.

  13. Reduced acoustic noise in diffusion tensor imaging on a compact MRI system.

    PubMed

    Tan, Ek T; Hardy, Christopher J; Shu, Yunhong; In, Myung-Ho; Guidon, Arnaud; Huston, John; Bernstein, Matt A; K F Foo, Thomas

    2017-10-02

    To investigate the feasibility of substantially reducing acoustic noise while performing diffusion tensor imaging (DTI) on a compact 3T (C3T) MRI scanner equipped with a 42-cm inner-diameter asymmetric gradient. A-weighted acoustic measurements were made using 10 mT/m-amplitude sinusoidal waveforms, corresponding to echo-planar imaging (EPI) echo spacing of 0.25 to 5.0 ms, on a conventional, whole-body 3T MRI and on the C3T. Acoustic measurements of DTI with trapezoidal EPI waveforms were then made at peak gradient performance on the C3T (80 mT/m amplitude, 700 T/m/s slew rate) and at derated performance (33 mT/m, 10 to 50 T/m/s) for acoustic noise reduction. DTI was acquired in two different phantoms and in seven human subjects, with and without gradient-derating corresponding to multi- and single-shot acquisitions, respectively. Sinusoidal waveforms on the C3T were quieter by 8.5 to 15.6 A-weighted decibels (dBA) on average as compared to the whole-body MRI. The derated multishot DTI acquisition noise level was only 8.7 dBA (at 13 T/m/s slew rate) above ambient, and was quieter than non-derated, single-shot DTI by 22.3 dBA; however, the scan time was almost quadrupled. Although derating resulted in negligible diffusivity differences in the phantoms, small biases in diffusivity measurements were observed in human subjects (apparent diffusion coefficient = +9.3 ± 8.8%, fractional anisotropy = +3.2 ± 11.2%, radial diffusivity = +9.4 ± 16.8%, parallel diffusivity = +10.3 ± 8.4%). The feasibility of achieving reduced acoustic noise levels with whole-brain DTI on the C3T MRI was demonstrated. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  14. 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.

  15. 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.

  16. Laser-Induced Thermal Acoustics Theory and Expected Experimental Errors when Applied to a Scramjet Isolator Model

    NASA Technical Reports Server (NTRS)

    Middleton, Troy F.; Balla, Robert Jeffrey; Baurle, Robert A.; Wilson, Lloyd G.

    2011-01-01

    A scramjet isolator model test apparatus is being assembled in the Isolator Dynamics Research Lab (IDRL) at the NASA Langley Research Center in Hampton, Virginia. The test apparatus is designed to support multiple measurement techniques for investigating the flow field in a scramjet isolator model. The test section is 1-inch high by 2-inch wide by 24-inch long and simulates a scramjet isolator with an aspect ratio of two. Unheated, dry air at a constant stagnation pressure and temperature is delivered to the isolator test section through a Mach 2.5 planar nozzle. The isolator test section is mechanically back-pressured to contain the resulting shock train within the 24-inch isolator length and supports temperature, static pressure, and high frequency pressure measurements at the wall. Additionally, nonintrusive methods including laser-induced thermal acoustics (LITA), spontaneous Raman scattering, particle image velocimetry, and schlieren imaging are being incorporated to measure off-wall fluid dynamic, thermodynamic, and transport properties of the flow field. Interchangeable glass and metallic sidewalls and optical access appendages permit making multiple measurements simultaneously. The measurements will be used to calibrate computational fluid dynamics turbulence models and characterize the back-pressured flow of a scramjet isolator. This paper describes the test apparatus, including the optical access appendages; the physics of the LITA method; and estimates of LITA measurement uncertainty for measurements of the speed of sound and temperature.

  17. Ultrasound-Mediated Biophotonic Imaging: A Review of Acousto-Optical Tomography and Photo-Acoustic Tomography

    PubMed Central

    Wang, Lihong V.

    2004-01-01

    This article reviews two types of ultrasound-mediated biophotonic imaging–acousto-optical tomography (AOT, also called ultrasound-modulated optical tomography) and photo-acoustic tomography (PAT, also called opto-acoustic or thermo-acoustic tomography)–both of which are based on non-ionizing optical and ultrasonic waves. The goal of these technologies is to combine the contrast advantage of the optical properties and the resolution advantage of ultrasound. In these two technologies, the imaging contrast is based primarily on the optical properties of biological tissues, and the imaging resolution is based primarily on the ultrasonic waves that either are provided externally or produced internally, within the biological tissues. In fact, ultrasonic mediation overcomes both the resolution disadvantage of pure optical imaging in thick tissues and the contrast and speckle disadvantages of pure ultrasonic imaging. In our discussion of AOT, the relationship between modulation depth and acoustic amplitude is clarified. Potential clinical applications of ultrasound-mediated biophotonic imaging include early cancer detection, functional imaging, and molecular imaging. PMID:15096709

  18. 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.

  19. An In Vitro Assessment of Acoustic Radiation Force Impulse Imaging for Visualizing Cardiac Radiofrequency Ablation Lesions

    PubMed Central

    Eyerly, Stephanie A.; Hsu, Stephen J.; Agashe, Shruti H.; Trahey, Gregg E.; Li, Yang; Wolf, Patrick D.

    2009-01-01

    Introduction Lesion placement and transmurality are critical factors in the success of cardiac transcatheter radiofrequency ablation (RFA) treatments for supraventricular arrhythmias. This study investigated the capabilities of catheter transducer based acoustic radiation force impulse (ARFI) ultrasound imaging for quantifying ablation lesion dimensions. Methods and Results RFA lesions were created in vitro in porcine ventricular myocardium and imaged with an intracardiac ultrasound catheter transducer capable of acquiring spatially registered B-mode and ARFI images. The myocardium was sliced along the imaging plane and photographed. The maximum ARFI-induced displacement images of the lesion were normalized and spatially registered with the photograph by matching the surfaces of the tissue in the B-mode and photographic images. The lesion dimensions determined by a manual segmentation of the photographed lesion based on the visible discoloration of the tissue were compared to automatic segmentations of the ARFI image using two different calculated thresholds. ARFI imaging accurately localized and sized the lesions within the myocardium. Differences in the maximum lateral and axial dimensions were statistically below 2 mm and 1 mm respectively for the two thresholding methods, with mean percent overlap of 68.7±5.21% and 66.3±8.4% for the two thresholds used. Conclusion ARFI imaging is capable of visualizing myocardial RFA lesion dimensions to within 2 mm in vitro. Visualizing lesions during transcatheter cardiac ablation procedures could improve the success of the treatment by imaging lesion line discontinuity and potentially reducing the required number of ablation lesions and procedure time. PMID:20021518

  20. 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.

  1. 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

  2. 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

    2016-09-08

    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.

  3. 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.

  4. Direct imaging of delayed magneto-dynamic modes induced by surface acoustic waves.

    PubMed

    Foerster, Michael; Macià, Ferran; Statuto, Nahuel; Finizio, Simone; Hernández-Mínguez, Alberto; Lendínez, Sergi; Santos, Paulo V; Fontcuberta, Josep; Hernàndez, Joan Manel; Kläui, Mathias; Aballe, Lucia

    2017-09-01

    The magnetoelastic effect-the change of magnetic properties caused by the elastic deformation of a magnetic material-has been proposed as an alternative approach to magnetic fields for the low-power control of magnetization states of nanoelements since it avoids charge currents, which entail ohmic losses. Here, we have studied the effect of dynamic strain accompanying a surface acoustic wave on magnetic nanostructures in thermal equilibrium. We have developed an experimental technique based on stroboscopic X-ray microscopy that provides a pathway to the quantitative study of strain waves and magnetization at the nanoscale. We have simultaneously imaged the evolution of both strain and magnetization dynamics of nanostructures at the picosecond time scale and found that magnetization modes have a delayed response to the strain modes, adjustable by the magnetic domain configuration. Our results provide fundamental insight into magnetoelastic coupling in nanostructures and have implications for the design of strain-controlled magnetostrictive nano-devices.Understanding the effects of local dynamic strain on magnetization may help the development of magnetic devices. Foerster et al. demonstrate stroboscopic imaging that allows the observation of both strain and magnetization dynamics in nickel when surface acoustic waves are driven in the substrate.

  5. Renal elasticity quantification by acoustic radiation force impulse applied to the evaluation of kidney diseases: a review.

    PubMed

    Zaffanello, Marco; Piacentini, Giorgio; Bruno, Costanza; Brugnara, Milena; Fanos, Vassilios

    2015-04-01

    For centuries, clinicians have used palpation to evaluate abdominal organs. After exploring almost all the different methods of interaction between x-rays, ultrasound, and magnetic fields on tissues, recent interest has focused on the evaluation of their mechanical properties.Acoustic radiation force impulse (ARFI) is a recent, established ultrasound-based diagnostic technique that allows physicians to obtain a measure of the elastic properties of an organ. Shear wave velocity, obtained by the ARFI technique, depends on the elasticity of tissues.To date, there are studies on the ARFI technique applied to normal kidneys, chronic kidney diseases, and kidney transplants. Mechanical properties of the kidney, such as stiffness and deformity, depend on various conditions that alter its histology, in particular the amount of fibrosis in the renal parenchyma; urinary pressure and renal blood perfusion may be other important contributing factors. Unfortunately, the ARFI technique applied to native renal pathologies is still limited, and not all studies are comparable because they used different methods. Therefore, the results reported in recent literature encourage further improvement of this method and the drawing up of standardized guidelines of investigation.

  6. 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.

  7. Improving the resolution of three-dimensional acoustic imaging with planar phased arrays

    NASA Astrophysics Data System (ADS)

    Xenaki, Angeliki; Jacobsen, Finn; Fernandez-Grande, Efren

    2012-04-01

    This paper examines and compares two methods of improving the quality of three-dimensional beamforming with phased microphone arrays. The intended application is the detection of aerodynamic noise sources on wind turbines. Both methods employ Fourier based deconvolution. The first method involves a transformation of coordinates that tends to make the response to a point source, the point spread function, more shift invariant. The result is a significant improvement in sound source imaging in the transformed coordinate system. However, the inverse transformation to Cartesian coordinates introduces range dependent resolution limitations because of the irregular distribution of the focal points. The second method combines the transformation of coordinates with an alternative scanning technique. This method can be used in near field three-dimensional acoustic imaging to produce maps free of sidelobes and with constant resolution. The robustness of the proposed methods is validated both with computer simulations and experimentally.

  8. Acoustic wavefield and Mach wave radiation of flashing arcs in strombolian explosion measured by image luminance

    NASA Astrophysics Data System (ADS)

    Genco, Riccardo; Ripepe, Maurizio; Marchetti, Emanuele; Bonadonna, Costanza; Biass, Sebastien

    2014-10-01

    Explosive activity often generates visible flashing arcs in the volcanic plume considered as the evidence of the shock-front propagation induced by supersonic dynamics. High-speed image processing is used to visualize the pressure wavefield associated with flashing arcs observed in strombolian explosions. Image luminance is converted in virtual acoustic signal compatible with the signal recorded by pressure transducer. Luminance variations are moving with a spherical front at a 344.7 m/s velocity. Flashing arcs travel at the sound speed already 14 m above the vent and are not necessarily the evidence of a supersonic explosive dynamics. However, seconds later, the velocity of small fragments increases, and the spherical acousto-luminance wavefront becomes planar recalling the Mach wave radiation generated by large scale turbulence in high-speed jet. This planar wavefront forms a Mach angle of 55° with the explosive jet axis, suggesting an explosive dynamics moving at Mo = 1.22 Mach number.

  9. Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector.

    PubMed

    Wang, Yi; Li, Chunhui; Wang, Ruikang K

    2011-10-15

    We report on a noncontact photoacoustic imaging (PAI) technique in which a low-coherence interferometer [(LCI), optical coherence tomography (OCT) hardware] is utilized as the acoustic detector. A synchronization approach is used to lock the LCI system at its highly sensitive region for photoacoustic detection. The technique is experimentally verified by the imaging of a scattering phantom embedded with hairs and the blood vessels within a mouse ear in vitro. The system's axial and lateral resolutions are evaluated at 60 and 30 μm, respectively. The experimental results indicate that PAI in a noncontact detection mode is possible with high resolution and high bandwidth. The proposed approach lends itself to a natural integration of PAI with OCT, rather than a combination of two separate and independent systems.

  10. Hyperspectral imaging applied to end-of-life concrete recycling

    NASA Astrophysics Data System (ADS)

    Serranti, Silvia; Bonifazi, Giuseppe

    2014-03-01

    In this paper a new technology, based on HyperSpectral Imaging (HSI) sensors, and related detection architectures, is investigated in order to develop suitable and low cost strategies addressed to: i) preliminary detection and characterization of the composition of the structure to dismantle and ii) definition and implementation of innovative smart detection engines for sorting and/or demolition waste flow stream quality control. The proposed sensing architecture is fast, accurate, affordable and it can strongly contribute to bring down the economic threshold above which recycling is cost efficient. Investigations have been carried out utilizing an HSI device working in the range 1000-1700 nm: NIR Spectral Camera™, embedding an ImSpector™ N17E (SPECIM Ltd, Finland). Spectral data analysis was carried out utilizing the PLS_Toolbox (Version 6.5.1, Eigenvector Research, Inc.) running inside Matlab® (Version 7.11.1, The Mathworks, Inc.), applying different chemometric techniques, selected depending on the materials under investigation. The developed procedure allows assessing the characteristics, in terms of materials identification, such as recycled aggregates and related contaminants, as resulting from end-of-life concrete processing. A good classification of the different classes of material was obtained, being the model able to distinguish aggregates from other materials (i.e. glass, plastic, tiles, paper, cardboard, wood, brick, gypsum, etc.).

  11. Advanced imaging systems for diagnostic investigations applied to Cultural Heritage

    NASA Astrophysics Data System (ADS)

    Peccenini, E.; Albertin, F.; Bettuzzi, M.; Brancaccio, R.; Casali, F.; Morigi, M. P.; Petrucci, F.

    2014-12-01

    The diagnostic investigations are an important resource in the studies on Cultural Heritage to enhance the knowledge on execution techniques, materials and conservation status of a work of art. In this field, due to the great historical and artistic value of the objects, preservation is the main concern; for this reason, new technological equipment has been designed and developed in the Physics Departments of the Universities of Ferrara and Bologna to enhance the non-invasive approach to the study of pictorial artworks and other objects of cultural interest. Infrared (IR) reflectography, X-ray radiography and computed tomography (CT), applied to works of art, are joined by the same goal: to get hidden information on execution techniques and inner structure pursuing the non-invasiveness of the methods, although using different setup and physical principles. In this work transportable imaging systems to investigate large objects in museums and galleries are presented. In particular, 2D scanning devices for IR reflectography and X-ray radiography, CT systems and some applications to the Cultural Heritage are described.

  12. Case-based statistical learning applied to SPECT image classification

    NASA Astrophysics Data System (ADS)

    Górriz, Juan M.; Ramírez, Javier; Illán, I. A.; Martínez-Murcia, Francisco J.; Segovia, Fermín.; Salas-Gonzalez, Diego; Ortiz, A.

    2017-03-01

    Statistical learning and decision theory play a key role in many areas of science and engineering. Some examples include time series regression and prediction, optical character recognition, signal detection in communications or biomedical applications for diagnosis and prognosis. This paper deals with the topic of learning from biomedical image data in the classification problem. In a typical scenario we have a training set that is employed to fit a prediction model or learner and a testing set on which the learner is applied to in order to predict the outcome for new unseen patterns. Both processes are usually completely separated to avoid over-fitting and due to the fact that, in practice, the unseen new objects (testing set) have unknown outcomes. However, the outcome yields one of a discrete set of values, i.e. the binary diagnosis problem. Thus, assumptions on these outcome values could be established to obtain the most likely prediction model at the training stage, that could improve the overall classification accuracy on the testing set, or keep its performance at least at the level of the selected statistical classifier. In this sense, a novel case-based learning (c-learning) procedure is proposed which combines hypothesis testing from a discrete set of expected outcomes and a cross-validated classification stage.

  13. 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.

  14. 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.

  15. 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

  16. Applying a visual language for image processing as a graphical teaching tool in medical imaging

    NASA Astrophysics Data System (ADS)

    Birchman, James J.; Tanimoto, Steven L.; Rowberg, Alan H.; Choi, Hyung-Sik; Kim, Yongmin

    1992-05-01

    Typical user interaction in image processing is with command line entries, pull-down menus, or text menu selections from a list, and as such is not generally graphical in nature. Although applying these interactive methods to construct more sophisticated algorithms from a series of simple image processing steps may be clear to engineers and programmers, it may not be clear to clinicians. A solution to this problem is to implement a visual programming language using visual representations to express image processing algorithms. Visual representations promote a more natural and rapid understanding of image processing algorithms by providing more visual insight into what the algorithms do than the interactive methods mentioned above can provide. Individuals accustomed to dealing with images will be more likely to understand an algorithm that is represented visually. This is especially true of referring physicians, such as surgeons in an intensive care unit. With the increasing acceptance of picture archiving and communications system (PACS) workstations and the trend toward increasing clinical use of image processing, referring physicians will need to learn more sophisticated concepts than simply image access and display. If the procedures that they perform commonly, such as window width and window level adjustment and image enhancement using unsharp masking, are depicted visually in an interactive environment, it will be easier for them to learn and apply these concepts. The software described in this paper is a visual programming language for imaging processing which has been implemented on the NeXT computer using NeXTstep user interface development tools and other tools in an object-oriented environment. The concept is based upon the description of a visual language titled `Visualization of Vision Algorithms' (VIVA). Iconic representations of simple image processing steps are placed into a workbench screen and connected together into a dataflow path by the user. As

  17. Restricted Acoustic Modal Analysis Applied to Internal Combustor Spectra and Cross-Spectra Measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    2006-01-01

    A treatment of the modal decomposition of the pressure field in a combustor as determined by two Kulite pressure measurements is developed herein. It is applied to a Pratt & Whitney PW4098 engine combustor over a range of operating conditions. For modes other than the plane wave the new part of the treatment is the assumption that there are distinct frequency bands in which the individual modes, including the plane wave mode, overlap such that if circumferential mode m and circumferential mode m-1 are present than circumferential mode m 2 is not. Consequently, in the analysis used herein at frequencies above the first cut-off mode frequency, only pairs of circumferential modes are individually present at each frequency. Consequently, this is a restricted modal analysis. A new result is that the successful use of the same modal span frequencies over a range of operating conditions for this particular engine suggests that the temperature, T, and the velocity, v, of the flow at each operating condition are related by c(sup 2)-v(sup 2) = a constant where c is the speed of sound.

  18. Comparison of super-resolution algorithms applied to retinal images

    NASA Astrophysics Data System (ADS)

    Thapa, Damber; Raahemifar, Kaamran; Bobier, William R.; Lakshminarayanan, Vasudevan

    2014-05-01

    A critical challenge in biomedical imaging is to optimally balance the trade-off among image resolution, signal-to-noise ratio, and acquisition time. Acquiring a high-resolution image is possible; however, it is either expensive or time consuming or both. Resolution is also limited by the physical properties of the imaging device, such as the nature and size of the input source radiation and the optics of the device. Super-resolution (SR), which is an off-line approach for improving the resolution of an image, is free of these trade-offs. Several methodologies, such as interpolation, frequency domain, regularization, and learning-based approaches, have been developed over the past several years for SR of natural images. We review some of these methods and demonstrate the positive impact expected from SR of retinal images and investigate the performance of various SR techniques. We use a fundus image as an example for simulations.

  19. 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

  20. NOAA-AVHRR image mosaics applied to vegetation identification

    NASA Astrophysics Data System (ADS)

    de Almeida, Maria d. G.; Ruddorff, Bernardo F.; Shimabukuro, Yosio E.

    2001-06-01

    In this paper, the maximum-value composite of images procedure from Normalized Difference Vegetation Index is used to get a cloud free image mosaic. The image mosaic is used to identify vegetation targets such as tropical forest, savanna and caatinga as well to make the vegetation cover mapping of Minas Gerais state, Brazil.

  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. 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

  3. Passive element enriched photoacoustic computed tomography (PER PACT) for simultaneous imaging of acoustic propagation properties and light absorption.

    PubMed

    Jose, Jithin; Willemink, Rene G H; Resink, Steffen; Piras, Daniele; van Hespen, J C G; Slump, Cornelis H; Steenbergen, Wiendelt; van Leeuwen, Ton G; Manohar, Srirang

    2011-01-31

    We present a 'hybrid' imaging approach which can image both light absorption properties and acoustic transmission properties of an object in a two-dimensional slice using a computed tomography (CT) photoacoustic imager. The ultrasound transmission measurement method uses a strong optical absorber of small cross-section placed in the path of the light illuminating the sample. This absorber, which we call a passive element acts as a source of ultrasound. The interaction of ultrasound with the sample can be measured in transmission, using the same ultrasound detector used for photoacoustics. Such measurements are made at various angles around the sample in a CT approach. Images of the ultrasound propagation parameters, attenuation and speed of sound, can be reconstructed by inversion of a measurement model. We validate the method on specially designed phantoms and biological specimens. The obtained images are quantitative in terms of the shape, size, location, and acoustic properties of the examined heterogeneities.

  4. Manifold learning based registration algorithms applied to multimodal images.

    PubMed

    Azampour, Mohammad Farid; Ghaffari, Aboozar; Hamidinekoo, Azam; Fatemizadeh, Emad

    2014-01-01

    Manifold learning algorithms are proposed to be used in image processing based on their ability in preserving data structures while reducing the dimension and the exposure of data structure in lower dimension. Multi-modal images have the same structure and can be registered together as monomodal images if only structural information is shown. As a result, manifold learning is able to transform multi-modal images to mono-modal ones and subsequently do the registration using mono-modal methods. Based on this application, in this paper novel similarity measures are proposed for multi-modal images in which Laplacian eigenmaps are employed as manifold learning algorithm and are tested against rigid registration of PET/MR images. Results show the feasibility of using manifold learning as a way of calculating the similarity between multimodal images.

  5. 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

  6. 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

  7. Imaging of human tooth using ultrasound based chirp-coded nonlinear time reversal acoustics.

    PubMed

    Dos Santos, Serge; Prevorovsky, Zdenek

    2011-08-01

    Human tooth imaging sonography is investigated experimentally with an acousto-optic noncoupling set-up based on the chirp-coded nonlinear time reversal acoustic concept. The complexity of the tooth internal structure (enamel-dentine interface, cracks between internal tubules) is analyzed by adapting the nonlinear elastic wave spectroscopy (NEWS) with the objective of the tomography of damage. Optimization of excitations using intrinsic symmetries, such as time reversal (TR) invariance, reciprocity, correlation properties are then proposed and implemented experimentally. The proposed medical application of this TR-NEWS approach is implemented on a third molar human tooth and constitutes an alternative of noncoupling echodentography techniques. A 10 MHz bandwidth ultrasonic instrumentation has been developed including a laser vibrometer and a 20 MHz contact piezoelectric transducer. The calibrated chirp-coded TR-NEWS imaging of the tooth is obtained using symmetrized excitations, pre- and post-signal processing, and the highly sensitive 14 bit resolution TR-NEWS instrumentation previously calibrated. Nonlinear signature coming from the symmetry properties is observed experimentally in the tooth using this bi-modal TR-NEWS imaging after and before the focusing induced by the time-compression process. The TR-NEWS polar B-scan of the tooth is described and suggested as a potential application for modern echodentography. It constitutes the basis of the self-consistent harmonic imaging sonography for monitoring cracks propagation in the dentine, responsible of human tooth structural health. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Acoustic radiation force impulse imaging of vulnerable plaques: a finite element method parametric analysis

    PubMed Central

    Doherty, Joshua R.; Dumont, Douglas M.; Trahey, Gregg E.; Palmeri, Mark L.

    2012-01-01

    Plaque rupture is the most common cause of complications such as stroke and coronary heart failure. Recent histopathological evidence suggests that several plaque features, including a large lipid core and a thin fibrous cap, are associated with plaques most at risk for rupture. Acoustic Radiation Force Impulse (ARFI) imaging, a recently developed ultrasound-based elasticity imaging technique, shows promise for imaging these features noninvasively. Clinically, this could be used to distinguish vulnerable plaques, for which surgical intervention may be required, from those less prone to rupture. In this study, a parametric analysis using Finite-Element Method (FEM) models was performed to simulate ARFI imaging of five different carotid artery plaques across a wide range of material properties. It was demonstrated that ARFI could resolve the softer lipid pool from the surrounding, stiffer media and fibrous cap and was most dependent upon the stiffness of the lipid pool component. Stress concentrations due to an ARFI excitation were located in the media and fibrous cap components. In all cases, the maximum Von Mises stress was < 1.2 kPa. In comparing these results with others investigating plaque rupture, it is concluded that while the mechanisms may be different, the Von Mises stresses imposed by ARFI are orders of magnitude lower than the stresses associated with blood pressure. PMID:23122224

  9. Evaluation of graft stiffness using acoustic radiation force impulse imaging after living donor liver transplantation.

    PubMed

    Ijichi, Hideki; Shirabe, Ken; Matsumoto, Yoshihiro; Yoshizumi, Tomoharu; Ikegami, Toru; Kayashima, Hiroto; Morita, Kazutoyo; Toshima, Takeo; Mano, Yohei; Maehara, Yoshihiko

    2014-11-01

    Acoustic radiation force impulse (ARFI) imaging is an ultrasound-based modality to evaluate tissue stiffness using short-duration acoustic pulses in the region of interest. Virtual touch tissue quantification (VTTQ), which is an implementation of ARFI, allows quantitative assessment of tissue stiffness. Twenty recipients who underwent living donor liver transplantation (LDLT) for chronic liver diseases were enrolled. Graft types included left lobes with the middle hepatic vein and caudate lobes (n = 11), right lobes (n = 7), and right posterior segments (n = 2). They underwent measurement of graft VTTQ during the early post-LDLT period. The VTTQ value level rose after LDLT, reaching a maximum level on postoperative day 4. There were no significant differences in the VTTQ values between the left and right lobe graft types. Significant correlations were observed between the postoperative maximum value of VTTQ and graft volume-to-recipient standard liver volume ratio, portal venous flow to graft volume ratio, and post-LDLT portal venous pressure. The postoperative maximum serum alanine aminotransferase level and ascites fluid production were also significantly correlated with VTTQ. ARFI may be a useful diagnostic tool for the noninvasive and quantitative evaluation of the severity of graft dysfunction after LDLT.

  10. 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.

  11. 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

  12. Digital imaging technology applied to crewstation display measurements

    NASA Astrophysics Data System (ADS)

    Nelson, Leonard Y.; Green, John R.

    1993-12-01

    A `slow scan' CCD camera has been adapted for luminance and radiance measurement of displays used in night vision goggle (NVG) compatible aircraft. A video lightmeter offers several advantages compared to conventional test methods including high speed image capture and color coding of the digital image data. The color coding feature facilitates evaluation of the test display uniformity. Numerical values for luminance and infrared radiance are also extracted from the image data.

  13. Simultaneous bilateral real-time 3-d transcranial ultrasound imaging at 1 MHz through poor acoustic windows.

    PubMed

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

    2013-04-01

    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.

  14. Sentential influences on acoustic-phonetic processing: A Granger causality analysis of multimodal imaging data

    PubMed Central

    Gow, David W.; Olson, Bruna B.

    2015-01-01

    Sentential context influences the way that listeners identify phonetically ambiguous or perceptual degraded speech sounds. Unfortunately, inherent inferential limitations on the interpretation of behavioral or BOLD imaging results make it unclear whether context influences perceptual processing directly, or acts at a post-perceptual decision stage. In this paper, we use Kalman-filter enabled Granger causation analysis of MR-constrained MEG/EEG data to distinguish between these possibilities. Using a retrospective probe verification task, we found that sentential context strongly affected the interpretation of words with ambiguous initial voicing (e.g. DUSK-TUSK). This behavioral context effect coincided with increased influence by brain regions associated with lexical representation on regions associated with acoustic-phonetic processing. These results support an interactive view of sentence context effects on speech perception. PMID:27595118

  15. 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.

  16. Near-Field Acoustical Imaging using Lateral Bending Mode of Atomic Force Microscope Cantilevers

    NASA Astrophysics Data System (ADS)

    Caron, A.; Rabe, U.; Rödel, J.; Arnold, W.

    Scanning probe microscopy techniques enable one to investigate surface properties such as contact stiffness and friction between the probe tip and a sample with nm resolution. So far the bending and the torsional eigenmodes of an atomic force microscope cantilever have been used to image variations of elasticity and shear elasticity, respectively. Such images are near-field images with the resolution given by the contact radius typically between 10 nm and 50 nm. We show that the flexural modes of a cantilever oscillating in the width direction and parallel to the sample surface can also be used for imaging. Additional to the dominant in-plane component of the oscillation, the lateral modes exhibit a vertical component as well, provided there is an asymmetry in the cross-section of the cantilever or in its suspension. The out-of-plane deflection renders the lateral modes detectable by the optical position sensors used in atomic force microscopes. We studied cracks which were generated by Vickers indents, in submicro- and nanocrystalline ZrO2. Images of the lateral contact stiffness were obtained by vibrating the cantilever close to a contact-resonance frequency. A change in contact stiffness causes a shift of the resonant frequency and hence a change of the cantilever vibration amplitude. The lateral contact-stiffness images close to the crack faces display a contrast that we attribute to altered elastic properties indicating a process zone. This could be caused by a stress-induced phase transformation during crack propagation. Using the contact mode of an atomic force microscope, we measured the crack-opening displacement as a function of distance from the crack tip, and we determined the crack-tip toughness Ktip. Furthermore, K1c was inferred from the length of radial cracks of Vickers indents that were measured using classical scanning acoustic microscopy

  17. Adaptive image segmentation applied to plant reproduction by tissue culture

    NASA Astrophysics Data System (ADS)

    Vazquez Rueda, Martin G.; Hahn, Federico; Zapata, Jose L.

    1997-04-01

    This paper presents that experimental results obtained on indoor tissue culture using the adaptive image segmentation system. The performance of the adaptive technique is contrasted with different non-adaptive techniques commonly used in the computer vision field to demonstrate the improvement provided by the adaptive image segmentation system.

  18. Applying public access programming techniques to astronomical image display

    NASA Astrophysics Data System (ADS)

    Mandel, Eric

    1996-03-01

    The X Public Access (XPA) mechanism allows an Xt program to define named public access points through which data and commands can be exchanged with other programs. We will discuss our design goals for XPA, the technical challenges we faced--including extensions to the Xt selection implementation--and the user interface and application programming interface that we developed to meet these challenges. We also will describe our application of XPA to a new version of the popular SAOimage astronomical image display program. XPA makes possible external control of the program's main function, including image display, image zoom and pan, colormap manipulation, cursor/region definition, and frame selection. It also supports `public access' to internal algorithms such as image file access and scaling. Finally, we will describe how XPA is used to support user-configurable analysis of image data and bi- directional communication with other processes.

  19. Improved bat algorithm applied to multilevel image thresholding.

    PubMed

    Alihodzic, Adis; Tuba, Milan

    2014-01-01

    Multilevel image thresholding is a very important image processing technique that is used as a basis for image segmentation and further higher level processing. However, the required computational time for exhaustive search grows exponentially with the number of desired thresholds. Swarm intelligence metaheuristics are well known as successful and efficient optimization methods for intractable problems. In this paper, we adjusted one of the latest swarm intelligence algorithms, the bat algorithm, for the multilevel image thresholding problem. The results of testing on standard benchmark images show that the bat algorithm is comparable with other state-of-the-art algorithms. We improved standard bat algorithm, where our modifications add some elements from the differential evolution and from the artificial bee colony algorithm. Our new proposed improved bat algorithm proved to be better than five other state-of-the-art algorithms, improving quality of results in all cases and significantly improving convergence speed.

  20. Improved Bat Algorithm Applied to Multilevel Image Thresholding

    PubMed Central

    2014-01-01

    Multilevel image thresholding is a very important image processing technique that is used as a basis for image segmentation and further higher level processing. However, the required computational time for exhaustive search grows exponentially with the number of desired thresholds. Swarm intelligence metaheuristics are well known as successful and efficient optimization methods for intractable problems. In this paper, we adjusted one of the latest swarm intelligence algorithms, the bat algorithm, for the multilevel image thresholding problem. The results of testing on standard benchmark images show that the bat algorithm is comparable with other state-of-the-art algorithms. We improved standard bat algorithm, where our modifications add some elements from the differential evolution and from the artificial bee colony algorithm. Our new proposed improved bat algorithm proved to be better than five other state-of-the-art algorithms, improving quality of results in all cases and significantly improving convergence speed. PMID:25165733

  1. 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.

  2. 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

  3. Applying image quality in cell phone cameras: lens distortion

    NASA Astrophysics Data System (ADS)

    Baxter, Donald; Goma, Sergio R.; Aleksic, Milivoje

    2009-01-01

    This paper describes the framework used in one of the pilot studies run under the I3A CPIQ initiative to quantify overall image quality in cell-phone cameras. The framework is based on a multivariate formalism which tries to predict overall image quality from individual image quality attributes and was validated in a CPIQ pilot program. The pilot study focuses on image quality distortions introduced in the optical path of a cell-phone camera, which may or may not be corrected in the image processing path. The assumption is that the captured image used is JPEG compressed and the cellphone camera is set to 'auto' mode. As the used framework requires that the individual attributes to be relatively perceptually orthogonal, in the pilot study, the attributes used are lens geometric distortion (LGD) and lateral chromatic aberrations (LCA). The goal of this paper is to present the framework of this pilot project starting with the definition of the individual attributes, up to their quantification in JNDs of quality, a requirement of the multivariate formalism, therefore both objective and subjective evaluations were used. A major distinction in the objective part from the 'DSC imaging world' is that the LCA/LGD distortions found in cell-phone cameras, rarely exhibit radial behavior, therefore a radial mapping/modeling cannot be used in this case.

  4. Experimental study on acoustic subwavelength imaging of holey-structured metamaterials by resonant tunneling.

    PubMed

    Su, Haijing; Zhou, Xiaoming; Xu, Xianchen; Hu, Gengkai

    2014-04-01

    A holey-structured metamaterial is proposed for near-field acoustic imaging beyond the diffraction limit. The structured lens consists of a rigid slab perforated with an array of cylindrical holes with periodically modulated diameters. Based on the effective medium approach, the structured lens is characterized by multilayered metamaterials with anisotropic dynamic mass, and an analytic model is proposed to evaluate the transmission properties of incident evanescent waves. The condition is derived for the resonant tunneling, by which evanescent waves can completely transmit through the structured lens without decaying. As an advantage of the proposed lens, the imaging frequency can be modified by the diameter modulation of internal holes without the change of the lens thickness in contrast to the lens due to the Fabry-Pérot resonant mechanism. In this experiment, the lens is assembled by aluminum plates drilled with cylindrical holes. The imaging experiment demonstrates that the designed lens can clearly distinguish two sources separated in the distance below the diffraction limit at the tunneling frequency.

  5. 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

  6. Imaging techniques applied to characterize bitumen and bituminous emulsions.

    PubMed

    Rodríguez-Valverde, M A; Ramón-Torregrosa, P; Páez-Dueñas, A; Cabrerizo-Vílchez, M A; Hidalgo-Alvarez, R

    2008-01-15

    The purpose of this article is to present some important advances in the imaging techniques currently used in the characterization of bitumen and bituminous emulsions. Bitumen exhibits some properties, such as a black colour and a reflecting surface at rest, which permit the use of optical techniques to study the macroscopic behaviour of asphalt mixes in the cold mix technology based on emulsion use. Imaging techniques allow monitoring in situ the bitumen thermal sensitivity as well as the complex phenomenon of emulsion breaking. Evaporation-driven breaking was evaluated from the shape of evaporating emulsion drops deposited onto non-porous and hydrophobic substrates. To describe the breaking kinetics, top-view images of a drying emulsion drop placed on an aggregate sheet were acquired and processed properly. We can conclude that computer-aided image analysis in road pavement engineering can elucidate the mechanism of breaking and curing of bituminous emulsion.

  7. Intracardiac Acoustic Radiation Force Impulse (ARFI) and Shear Wave Imaging in Pigs with Focal Infarctions

    PubMed Central

    Hollender, Peter; Bradway, David; Wolf, Patrick; Goswami, Robi; Trahey, Gregg

    2013-01-01

    Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-Modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, ARFI and SWEI estimates indicated diastolic relaxation and systolic contraction in non-infarcted tissues. The M-Mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared to the control. Where available, views of infarcted tissue were compared to similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared to the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, while in another view, a heterogeneous infarction was seen presenting itself as non-contractile in systole. PMID:25004538

  8. Analysis of soil images applying Laplacian Pyramidal techniques

    NASA Astrophysics Data System (ADS)

    Ballesteros, F.; de Castro, J.; Tarquis, A. M.; Méndez, A.

    2012-04-01

    The Laplacian pyramid is a technique for image encoding in which local operators of many scales but identical shape are the basis functions. Our work describes some properties of the filters of the Laplacian pyramid. Specially, we pay attention to Gaussian and fractal behaviour of these filters, and we determine the normal and fractal ranges in the case of single parameter filters, while studying the influence of these filters in soil image processing. One usual property of any image is that neighboring pixels are highly correlated. This property makes inefficient to represent the image directly in terms of the pixel values, because most of the encoded information would be redundant. Burt and Adelson designed a technique, named Laplacian pyramid, for removing image correlation which combines features of predictive and transform methods. This technique is non causal, and its computations are simple and local. The predicted value for each pixel is computed as a local weighted average, using a unimodal weighting function centred on the pixel itself. Pyramid construction is equivalent to convolving the original image with a set of weighting functions determined by a parameter that defines the filter. According to the parameter values, these filters have a behaviour that goes from the Gaussian shape to the fractal. Previous works only analyze Gaussian filters, but we determine the Gaussian and fractal intervals and study the energy of the Laplacian pyramid images according to the filter types. The different behaviour, qualitatively, involves a significant change in statistical characteristics at different levels of iteration, especially the fractal case, which can highlight specific information from the images. Funding provided by Spanish Ministerio de Ciencia e Innovación (MICINN) through project no. AGL2010-21501/AGR is greatly appreciated.

  9. The problem of applying information theory to efficient image transmission.

    NASA Technical Reports Server (NTRS)

    Sakrison, D. J.

    1973-01-01

    The main ideas of Shannon's (1948, 1960) theory of source encoding with a fidelity constraint, more commonly known as rate distortion theory, are summarized. The theory was specifically intended to provide a theoretical basis for efficient transmission of information such as images. What the theory has to contribute to the problem is demonstrated. Difficulties that impeded application of the theory to image transmission, and current efforts to solve these difficulties are discussed.

  10. An in vivo validation of the application of acoustic radiation force to enhance the diagnostic utility of molecular imaging using 3-d ultrasound.

    PubMed

    Gessner, Ryan C; Streeter, Jason E; Kothadia, Roshni; Feingold, Steven; Dayton, Paul A

    2012-04-01

    For more than a decade, the application of acoustic radiation force (ARF) has been proposed as a mechanism to increase ultrasonic molecular imaging (MI) sensitivity in vivo. Presented herein is the first noninvasive in vivo validation of ARF-enhanced MI with an unmodified clinical system. First, an in vitro optical-acoustical setup was used to optimize system parameters and ensure sufficient microbubble translation when exposed to ARF. 3-D ARF-enhanced MI was then performed on 7 rat fibrosarcoma tumors using microbubbles targeted to α(v)β₃ and nontargeted microbubbles. Low-amplitude (<25 kPa) 3-D ARF pulse sequences were tested and compared with passive targeting studies in the same animal. Our results demonstrate that a 78% increase in image intensity from targeted microbubbles can be achieved when using ARF relative to the passive targeting studies. Furthermore, ARF did not significantly increase image contrast when applied to nontargeted agents, suggesting that ARF did not increase nonspecific adhesion.

  11. Image remapping strategies applied as protheses for the visually impaired

    NASA Technical Reports Server (NTRS)

    Johnson, Curtis D.

    1993-01-01

    Maculopathy and retinitis pigmentosa (rp) are two vision defects which render the afflicted person with impaired ability to read and recognize visual patterns. For some time there has been interest and work on the use of image remapping techniques to provide a visual aid for individuals with these impairments. The basic concept is to remap an image according to some mathematical transformation such that the image is warped around a maculopathic defect (scotoma) or within the rp foveal region of retinal sensitivity. NASA/JSC has been pursuing this research using angle invariant transformations with testing of the resulting remapping using subjects and facilities of the University of Houston, College of Optometry. Testing is facilitated by use of a hardware device, the Programmable Remapper, to provide the remapping of video images. This report presents the results of studies of alternative remapping transformations with the objective of improving subject reading rates and pattern recognition. In particular a form of conformal transformation was developed which provides for a smooth warping of an image around a scotoma. In such a case it is shown that distortion of characters and lines of characters is minimized which should lead to enhanced character recognition. In addition studies were made of alternative transformations which, although not conformal, provide for similar low character distortion remapping. A second, non-conformal transformation was studied for remapping of images to aid rp impairments. In this case a transformation was investigated which allows remapping of a vision field into a circular area representing the foveal retina region. The size and spatial representation of the image are selectable. It is shown that parametric adjustments allow for a wide variation of how a visual field is presented to the sensitive retina. This study also presents some preliminary considerations of how a prosthetic device could be implemented in a practical sense, vis

  12. 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

  13. Quality assessment of butter cookies applying multispectral imaging

    PubMed Central

    Andresen, Mette S; Dissing, Bjørn S; Løje, Hanne

    2013-01-01

    A method for characterization of butter cookie quality by assessing the surface browning and water content using multispectral images is presented. Based on evaluations of the browning of butter cookies, cookies were manually divided into groups. From this categorization, reference values were calculated for a statistical prediction model correlating multispectral images with a browning score. The browning score is calculated as a function of oven temperature and baking time. It is presented as a quadratic response surface. The investigated process window was the intervals 4–16 min and 160–200°C in a forced convection electrically heated oven. In addition to the browning score, a model for predicting the average water content based on the same images is presented. This shows how multispectral images of butter cookies may be used for the assessment of different quality parameters. Statistical analysis showed that the most significant wavelengths for browning predictions were in the interval 400–700 nm and the wavelengths significant for water prediction were primarily located in the near-infrared spectrum. The water prediction model was found to correctly estimate the average water content with an absolute error of 0.22%. From the images it was also possible to follow the browning and drying propagation from the cookie edge toward the center. PMID:24804036

  14. Quality assessment of butter cookies applying multispectral imaging.

    PubMed

    Andresen, Mette S; Dissing, Bjørn S; Løje, Hanne

    2013-07-01

    A method for characterization of butter cookie quality by assessing the surface browning and water content using multispectral images is presented. Based on evaluations of the browning of butter cookies, cookies were manually divided into groups. From this categorization, reference values were calculated for a statistical prediction model correlating multispectral images with a browning score. The browning score is calculated as a function of oven temperature and baking time. It is presented as a quadratic response surface. The investigated process window was the intervals 4-16 min and 160-200°C in a forced convection electrically heated oven. In addition to the browning score, a model for predicting the average water content based on the same images is presented. This shows how multispectral images of butter cookies may be used for the assessment of different quality parameters. Statistical analysis showed that the most significant wavelengths for browning predictions were in the interval 400-700 nm and the wavelengths significant for water prediction were primarily located in the near-infrared spectrum. The water prediction model was found to correctly estimate the average water content with an absolute error of 0.22%. From the images it was also possible to follow the browning and drying propagation from the cookie edge toward the center.

  15. A view of the world through the bat's ear: the formation of acoustic images in echolocation.

    PubMed

    Simmons, J A

    1989-11-01

    Echolocating bats perceive objects as acoustic images derived from echoes of the ultrasonic sounds they emit. They can detect, track, identify, and intercept flying insects using sonar. Many species, such as the big brown bat, Eptesicus fuscus, emit frequency-modulated sonar sounds and perceive the distance to targets, or target range, from the delay of echoes. For Eptesicus, a point-target's image has a sharpness along the range axis that is determined by the acuity of echo-delay perception, which is about 10 ns under favorable conditions. The image as a whole has a fine range structure that corresponds to the cross-correlation function between emissions and echoes. A complex target- which has reflecting points, called "glints", located at slightly different distances and reflects echoes containing overlapping components with slightly different delays--is perceived in terms of its range profile. The separation of the glints along the range dimension is encoded by the shape of the echo spectrum created by interference between overlapping echo components. However, Eptesicus transforms the echo spectrum back into an estimate of the original delay separation of echo components. The bat thus converts spectral cues into elements of an image expressed in terms of range. The absolute range of the nearest glint is encoded by the arrival time of the earliest echo component, and the spectrally encoded range separation of additional glints is referred to this time-encoded reference range for the image as a whole. Each individual glint is represented by a cross-correlation function for its own echo component, the nearest of which is computed directly from arrival-time measurements while further ones are computed by transformation of the echo spectrum. The bat then sums the cross-correlation functions for multiple glints to form the entire image of the complex target. Range and shape are two distinct features of targets that are separately encoded by the bat's auditory system

  16. Personal Computer (PC) based image processing applied to fluid mechanics

    NASA Technical Reports Server (NTRS)

    Cho, Y.-C.; Mclachlan, B. G.

    1987-01-01

    A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.

  17. Personal Computer (PC) based image processing applied to fluid mechanics

    NASA Astrophysics Data System (ADS)

    Cho, Y.-C.; McLachlan, B. G.

    1987-10-01

    A PC based image processing system was employed to determine the instantaneous velocity field of a two-dimensional unsteady flow. The flow was visualized using a suspension of seeding particles in water, and a laser sheet for illumination. With a finite time exposure, the particle motion was captured on a photograph as a pattern of streaks. The streak pattern was digitized and processed using various imaging operations, including contrast manipulation, noise cleaning, filtering, statistical differencing, and thresholding. Information concerning the velocity was extracted from the enhanced image by measuring the length and orientation of the individual streaks. The fluid velocities deduced from the randomly distributed particle streaks were interpolated to obtain velocities at uniform grid points. For the interpolation a simple convolution technique with an adaptive Gaussian window was used. The results are compared with a numerical prediction by a Navier-Stokes computation.

  18. Contrast Enhanced Superharmonic Imaging for Acoustic Angiography Using Reduced Form-Factor Lateral Mode Transmitters for Intravascular and Intracavity Applications.

    PubMed

    Wang, Zhuochen; Heath Martin, K; Huang, Wenbin; Dayton, Paul A; Jiang, Xiaoning

    2017-02-01

    Techniques to image the microvasculature may play an important role in imaging tumor-related angiogenesis and vasa vasorum associated with vulnerable atherosclerotic plaques. However, the microvasculature associated with these pathologies is difficult to detect using traditional B-mode ultrasound or even harmonic imaging due to small vessel size and poor differentiation from surrounding tissue. Acoustic angiography, a microvascular imaging technique that utilizes superharmonic imaging (detection of higher order harmonics of microbubble response), can yield a much higher contrast-to-tissue ratio than second harmonic imaging methods. In this paper, two dual-frequency transducers using lateral mode transmitters were developed for superharmonic detection and acoustic angiography imaging in intracavity applications. A single element dual-frequency intravascular ultrasound transducer was developed for concept validation, which achieved larger signal amplitude, better contrast-to-noise ratio (CNR), and pulselength compared to the previous work. A dual-frequency [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] array transducer was then developed for superharmonic imaging with dynamic focusing. The axial and lateral sizes of the microbubbles in a 200- [Formula: see text] tube were measured to be 269 and [Formula: see text], respectively. The maximum CNR was calculated to be 22 dB. These results show that superharmonic imaging with a low frequency lateral mode transmitter is a feasible alternative to thickness mode transmitters when the final transducer size requirements dictate design choices.

  19. Magneto acoustic tomography with short pulsed magnetic field for in-vivo imaging of magnetic iron oxide nanoparticles.

    PubMed

    Mariappan, Leo; Shao, Qi; Jiang, Chunlan; Yu, Kai; Ashkenazi, Shai; Bischof, John C; He, Bin

    2016-04-01

    Nanoparticles are widely used as contrast and therapeutic agents. As such, imaging modalities that can accurately estimate their distribution in-vivo are actively sought. We present here our method Magneto Acoustic Tomography (MAT), which uses magnetomotive force due to a short pulsed magnetic field to induce ultrasound in the magnetic nanoparticle labeled tissue and estimates an image of the distribution of the nanoparticles in-vivo with ultrasound imaging resolution. In this study, we image the distribution of superparamagnetic iron oxide nanoparticles (IONP) using MAT method. In-vivo imaging was performed on live, nude mice with IONP injected into LNCaP tumors grown subcutaneously within the hind limb of the mice. Our experimental results indicate that the MAT method is capable of imaging the distribution of IONPs in-vivo. Therefore, MAT could become an imaging modality for high resolution reconstruction of MNP distribution in the body. Many magnetic nanoparticles (MNPs) have been used as contrast agents in magnetic resonance imaging. In this study, the authors investigated the use of ultrasound to detect the presence of MNPs by magneto acoustic tomography. In-vivo experiments confirmed the imaging quality of this new approach, which hopefully would provide an alternative method for accurate tumor detection. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Optical imaging applied to microelectronic chip-to-chip interconnections.

    PubMed

    Kostuk, R K; Goodman, J W; Hesselink, L

    1985-09-01

    An imaging system is proposed as an alternative to metallized connections between integrated circuits. Power requirements for metallized interconnects and electrooptic links are compared. A holographic optical element is considered as the imaging device. Several experimental systems have been constructed which have visible LEDs as the transmitters and PIN photodiodes as the receivers. Signals are evaluated at different source-detector separations. Multiple exposure holograms are used as a means of optical fan out allowing one source to simultaneously address several receiver locations. Limitations of this technique are also discussed.

  1. In vivo MR acoustic radiation force imaging in the porcine liver

    PubMed Central

    Holbrook, Andrew B.; Ghanouni, Pejman; Santos, Juan M.; Medan, Yoav; Butts Pauly, Kim

    2011-01-01

    Purpose: High intensity focused ultrasound (HIFU) in the abdomen can be sensitive to acoustic aberrations that can exist in the beam path of a single sonication. Having an accurate method to quickly visualize the transducer focus without damaging tissue could assist with executing the treatment plan accurately and predicting these changes and obstacles. By identifying these obstacles, MR acoustic radiation force imaging (MR-ARFI) provides a reliable method for visualizing the transducer focus quickly without damaging tissue and allows accurate execution of the treatment plan. Methods: MR-ARFI was used to view the HIFU focus, using a gated spin echo flyback readout-segmented echo-planar imaging sequence. HIFU spots in a phantom and in the livers of five live pigs under general anesthesia were created with a 550 kHz extracorporeal phased array transducer initially localized with a phase-dithered MR-tracking sequence to locate microcoils embedded in the transducer. MR-ARFI spots were visualized, observing the change of focal displacement and ease of steering. Finally, MR-ARFI was implemented as the principle liver HIFU calibration system, and MR-ARFI measurements of the focal location relative to the thermal ablation location in breath-hold and breathing experiments were performed. Results: Measuring focal displacement with MR-ARFI was achieved in the phantom and in vivo liver. In one in vivo experiment, where MR-ARFI images were acquired repeatedly at the same location with different powers, the displacement had a linear relationship with power [y = 0.04x + 0.83 μm (R2 = 0.96)]. In another experiment, the displacement images depicted the electronic steering of the focus inside the liver. With the new calibration system, the target focal location before thermal ablation was successfully verified. The entire calibration protocol delivered 20.2 J of energy to the animal (compared to greater than 800 J for a test thermal ablation). ARFI displacement maps

  2. In vivo MR acoustic radiation force imaging in the porcine liver.

    PubMed

    Holbrook, Andrew B; Ghanouni, Pejman; Santos, Juan M; Medan, Yoav; Butts Pauly, Kim

    2011-09-01

    High intensity focused ultrasound (HIFU) in the abdomen can be sensitive to acoustic aberrations that can exist in the beam path of a single sonication. Having an accurate method to quickly visualize the transducer focus without damaging tissue could assist with executing the treatment plan accurately and predicting these changes and obstacles. By identifying these obstacles, MR acoustic radiation force imaging (MR-ARFI) provides a reliable method for visualizing the transducer focus quickly without damaging tissue and allows accurate execution of the treatment plan. MR-ARFI was used to view the HIFU focus, using a gated spin echo flyback readout-segmented echo-planar imaging sequence. HIFU spots in a phantom and in the livers of five live pigs under general anesthesia were created with a 550 kHz extracorporeal phased array transducer initially localized with a phase-dithered MR-tracking sequence to locate microcoils embedded in the transducer. MR-ARFI spots were visualized, observing the change of focal displacement and ease of steering. Finally, MR-ARFI was implemented as the principle liver HIFU calibration system, and MR-ARFI measurements of the focal location relative to the thermal ablation location in breath-hold and breathing experiments were performed. Measuring focal displacement with MR-ARFI was achieved in the phantom and in vivo liver. In one in vivo experiment, where MR-ARFI images were acquired repeatedly at the same location with different powers, the displacement had a linear relationship with power [y = 0.04x + 0.83 μm (R(2) = 0.96)]. In another experiment, the displacement images depicted the electronic steering of the focus inside the liver. With the new calibration system, the target focal location before thermal ablation was successfully verified. The entire calibration protocol delivered 20.2 J of energy to the animal (compared to greater than 800 J for a test thermal ablation). ARFI displacement maps were compared with thermal

  3. Temperature-dependent differences in the nonlinear acoustic behavior of ultrasound contrast agents revealed by high-speed imaging and bulk acoustics.

    PubMed

    Mulvana, Helen; Stride, Eleanor; Tang, Mengxing; Hajnal, Jo V; Eckersley, Robert

    2011-09-01

    Previous work by the authors has established that increasing the temperature of the suspending liquid from 20°C to body temperature has a significant impact on the bulk acoustic properties and stability of an ultrasound contrast agent suspension (SonoVue, Bracco Suisse SA, Manno, Lugano, Switzerland). In this paper the influence of temperature on the nonlinear behavior of microbubbles is investigated, because this is one of the most important parameters in the context of diagnostic imaging. High-speed imaging showed that raising the temperature significantly influences the dynamic behavior of individual microbubbles. At body temperature, microbubbles exhibit greater radial excursion and oscillate less spherically, with a greater incidence of jetting and gas expulsion, and therefore collapse, than they do at room temperature. Bulk acoustics revealed an associated increase in the harmonic content of the scattered signals. These findings emphasize the importance of conducting laboratory studies at body temperature if the results are to be interpreted for in vivo applications. Copyright © 2011 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  4. A Review of Digital Image Correlation Applied to Structura Dynamics

    NASA Astrophysics Data System (ADS)

    Niezrecki, Christopher; Avitabile, Peter; Warren, Christopher; Pingle, Pawan; Helfrick, Mark

    2010-05-01

    A significant amount of interest exists in performing non-contacting, full-field surface velocity measurement. For many years traditional non-contacting surface velocity measurements have been made by using scanning Doppler laser vibrometry, shearography, pulsed laser interferometry, pulsed holography, or an electronic speckle pattern interferometer (ESPI). Three dimensional (3D) digital image correlation (DIC) methods utilize the alignment of a stereo pair of images to obtain full-field geometry data, in three dimensions. Information about the change in geometry of an object over time can be found by comparing a sequence of images and virtual strain gages (or position sensors) can be created over the entire visible surface of the object of interest. Digital imaging techniques were first developed in the 1980s but the technology has only recently been exploited in industry and research due to the advances of digital cameras and personal computers. The use of DIC for structural dynamic measurement has only very recently been investigated. Within this paper, the advantages and limits of using DIC for dynamic measurement are reviewed. Several examples of using DIC for dynamic measurement are presented on several vibrating and rotating structures.

  5. Students' Images of Problem Contexts when Solving Applied Problems

    ERIC Educational Resources Information Center

    Moore, Kevin C.; Carlson, Marilyn P.

    2012-01-01

    This article reports findings from an investigation of precalculus students' approaches to solving novel problems. We characterize the images that students constructed during their solution attempts and describe the degree to which they were successful in imagining how the quantities in a problem's context change together. Our analyses revealed…

  6. High-quality image magnification applying Gerchberg-Papoulis iterative algorithm with discrete cosine transform

    NASA Astrophysics Data System (ADS)

    Shinbori, Eiji; Takagi, Mikio

    1992-11-01

    A new image magnification method, called 'IM-GPDCT' (image magnification applying the Gerchberg-Papoulis (GP) iterative algorithm with discrete cosine transform (DCT)), is described and its performance evaluated. This method markedly improves image quality of a magnified image using a concept which restores the spatial high frequencies which are conventionally lost due to use of a low pass filter. These frequencies are restored using two known constraints applied during iterative DCT: (1) correct information in a passband is known and (2) the spatial extent of an image is finite. Simulation results show that the IM- GPDCT outperforms three conventional interpolation methods from both a restoration error and image quality standpoint.

  7. Imaging surface acoustic wave dynamics in semiconducting polymers by scanning ultrafast electron microscopy.

    PubMed

    Najafi, Ebrahim; Liao, Bolin; Scarborough, Timothy; Zewail, Ahmed

    2017-08-24

    Understanding the mechanical properties of organic semiconductors is essential to their electronic and photovoltaic applications. Despite a large volume of research directed toward elucidating the chemical, physical and electronic properties of these materials, little attention has been directed toward understanding their thermo-mechanical behavior. Here, we report the ultrafast imaging of surface acoustic waves (SAWs) on the surface of the Poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film at the picosecond and nanosecond timescales. We then use these images to measure the propagation velocity of SAWs, which we then employ to determine the Young's modulus of P3HT. We further validate our experimental observation by performing a semi-empirical transient thermoelastic finite element analysis. Our findings demonstrate the potential of ultrafast electron microscopy to not only probe charge carrier dynamics in materials as previously reported, but also to measure their mechanical properties with great accuracy. This is particularly important when in situ characterization of stiffness for thin devices and nanomaterials is required. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Distributed Acoustic Sensing for Imaging Near-Surface Geology and Monitoring Traffic at Garner Valley, California

    NASA Astrophysics Data System (ADS)

    Lancelle, Chelsea

    Distributed Acoustic Sensing (DAS) is a relatively new technology that uses a fiber-optic cable as a sensor. DAS got its start in the energy industry for borehole monitoring and more recently has started being used in horizontal arrays. The DAS technique senses strain rates every 1 m over distances of up to 100 km of cable length with sampling rates as fast as 100 kHz. This dissertation uses a horizontal DAS array in Southern California to evaluate the use of DAS for imaging near-surface geology and monitoring traffic. The first chapter uses Multichannel Analysis of Surface Waves to evaluate the response of DAS to surface waves. Dispersion curves from the DAS array match well with results from 1) other instruments at the site, 2) ambient noise correlation functions using the same DAS array, and 3) previous studies at the site. The second chapter uses the DAS array to create 2D tomographic images of the site for a number of pixel sizes and the directional sensitivity of DAS is discussed. The third chapter explores the possibility of using DAS for traffic monitoring. Vehicle counts, relative amplitudes, and velocities are identified and prove DAS could be used for traffic monitoring.

  9. Acoustic attenuation imaging of tissue bulk properties with a priori information

    PubMed Central

    Hooi, Fong Ming; Kripfgans, Oliver; Carson, Paul L.

    2016-01-01

    Attenuation of ultrasound waves traversing a medium is not only a result of absorption and scattering within a given tissue, but also of coherent scattering, including diffraction, refraction, and reflection of the acoustic wave at tissue boundaries. This leads to edge enhancement and other artifacts in most reconstruction algorithms, other than 3D wave migration with currently impractical, implementations. The presented approach accounts for energy loss at tissue boundaries by normalizing data based on variable sound speed, and potential density, of the medium using a k-space wave solver. Coupled with a priori knowledge of major sound speed distributions, physical attenuation values within broad ranges, and the assumption of homogeneity within segmented regions, an attenuation image representative of region bulk properties is constructed by solving a penalized weighted least squares optimization problem. This is in contradistinction to absorption or to conventional attenuation coefficient based on overall insertion loss with strong dependence on sound speed and impedance mismatches at tissue boundaries. This imaged property will be referred to as the bulk attenuation coefficient. The algorithm is demonstrated on an opposed array setup, with mean-squared-error improvements from 0.6269 to 0.0424 (dB/cm/MHz)2 for a cylindrical phantom, and 0.1622 to 0.0256 (dB/cm/MHz)2 for a windowed phantom. PMID:27914403

  10. A Surface Acoustic Wave Pumped Lensless Microfluidic Imaging System for Flowing Cell Detection and Counting.

    PubMed

    Huang, Xiwei; Farooq, Umar; Chen, Jin; Ge, Yakun; Gao, Haijun; Su, Jiangtao; Wang, Xiang; Dong, Shurong; Luo, Ji-Kui

    2017-08-29

    The future point-of-care diagnostics requires miniaturizing the existing bulky and expensive bioanalysis instruments, where lab-on-CMOS-chip-based technology can provide a promising solution. In this paper, we presented a surface acoustic wave (SAW) pumped lensless microfluidic imaging system for flowing cell detection and counting. Different from the previous lensless systems, which employ external bulky syringe pump for cell driven, the developed system directly integrates the SAW pump on the CMOS image sensor chip to drive the cell-containing microfluid. Moreover, an efficient temporal-differencing-based motion detection algorithm is proposed for continuous flowing cell detection and counting. Experimental results show that the SAW pump can drive the cells to flow at different driven powers, and also can keep the channel temperature below 40 °C so as not to harm the cells. The human bone marrow stromal cells flowing in the microfluidic channel can be automatically detected and counted with a low statistical error rate of -6.53%. The developed system thereby is competitive for point-of-care cell detection and counting application.

  11. Ultrasonic imaging of human tooth using chirp-coded nonlinear time reversal acoustics

    NASA Astrophysics Data System (ADS)

    Santos, Serge Dos; Domenjoud, Mathieu; Prevorovsky, Zdenek

    2010-01-01

    We report in this paper the first use of TR-NEWS, included chirp-coded excitation and applied for ultrasonic imaging of human tooth. Feasibility of the focusing of ultrasound at the surface of the human tooth is demonstrated and potentiality of a new echodentography of the dentine-enamel interface using TR-NEWS is discussed.

  12. TU-F-CAMPUS-I-04: Head-Only Asymmetric Gradient System Evaluation: ACR Image Quality and Acoustic Noise

    SciTech Connect

    Weavers, P; Shu, Y; Tao, S; Bernstein, M; Lee, S; Piel, J; Foo, T; Mathieu, J-B

    2015-06-15

    Purpose: A high-performance head-only magnetic resonance imaging gradient system with an acquisition volume of 26 cm employing an asymmetric design for the transverse coils has been developed. It is able to reach a magnitude of 85 mT/m at a slew rate of 700 T/m/s, but operated at 80 mT/m and 500 T/m/s for this test. A challenge resulting from this asymmetric design is that the gradient nonlinearly exhibits both odd- and even-ordered terms, and as the full imaging field of view is often used, the nonlinearity is pronounced. The purpose of this work is to show the system can produce clinically useful images after an on-site gradient nonlinearity calibration and correction, and show that acoustic noise levels fall within non-significant risk (NSR) limits for standard clinical pulse sequences. Methods: The head-only gradient system was inserted into a standard 3T wide-bore scanner without acoustic damping. The ACR phantom was scanned in an 8-channel receive-only head coil and the standard American College of Radiology (ACR) MRI quality control (QC) test was performed. Acoustic noise levels were measured for several standard pulse sequences. Results: Images acquired with the head-only gradient system passed all ACR MR image quality tests; Both even and odd-order gradient distortion correction terms were required for the asymmetric gradients to pass. Acoustic noise measurements were within FDA NSR guidelines of 99 dBA (with assumed 20 dBA hearing protection) A-weighted and 140 dB for peak for all but one sequence. Note the gradient system was installed without any shroud or acoustic batting. We expect final system integration to greatly reduce noise experienced by the patient. Conclusion: A high-performance head-only asymmetric gradient system operating at 80 mT/m and 500 T/m/s conforms to FDA acoustic noise limits in all but one case, and passes all the ACR MR image quality control tests. This work was supported in part by the NIH grant 5R01EB010065.

  13. 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

  14. Applying galactic archeology to massive galaxies using deep imaging surveys

    NASA Astrophysics Data System (ADS)

    Duc, Pierre-Alain

    2015-04-01

    Various programs aimed at exploring the still largely unknown low surface brightness Universe with deep imaging optical surveys have recently started. They open a new window for studies of galaxy evolution, pushing the technique of galactic archeology outside the Local Group (LG). The method, based on the detection and analysis of the diffuse light emitted by collisional debris or extended stellar halos (rather than on stellar counts as done for LG systems), faces however a number of technical difficulties, like the contamination of the images by reflection halos and Galactic cirrus. I review here the on-going efforts to address them and highlight the preliminary promising results obtained with a systematic survey with MegaCam on the CFHT of nearby massive early-type galaxies done as part of the ATLAS3D, NGVS and MATLAS collaborations.

  15. LANDSAT image studies as applied to petroleum exploration in Kenya

    NASA Technical Reports Server (NTRS)

    Miller, J. B.

    1975-01-01

    The Chevron-Kenya oil license, acquired in 1972, covers an area at the north end of the Lamu Embayment. Immediately after acquisition, a photogeologic study of the area was made followed by a short field inspection. An interpretation of LANDSAT-1 images as a separate attempt to improve geological knowledge was completed. The method used in the image study, the multispectral characteristics of rock units and terrain, and the observed anomalous features as seen in the LANDSAT imagery are described. It was found that the study helped to define the relationship of the Lamu Embayment and its internal structure with surrounding regional features, such as the East Africa rifting, the Rudolf Trough, the Bur Acaba structural ridge, and the Ogaden Basin.

  16. Acoustic Imaging of Microstructure and Evaluation of the Adhesive's Physical, Mechanical and Chemical Properties Changes at Different Cure States

    NASA Astrophysics Data System (ADS)

    Severina, I. A.; Fabre, A. J.; Maeva, E. Yu.

    Epoxy thermoset adhesives transform during cure from liquid state into the highly cross-linked solid. Cure state of the material depends on condition of the reaction (temperature, pressure, time etc.) and resin/hardener ratio. It is known that the cure degree of the adhesive correlates with adhesion strength, which is critical for structural adhesives used in automotive, aerospace and marine industries. In this work, characterization of cure process of the adhesive with acoustic methods is presented. Evolution of the acoustic and elastic properties (attenuation, sound velocity, density, elastic moduli) during cure reaction was monitored in relation to the substantial physical and chemical changes of the material. These macro parameters of the adhesive were compared with the material's microstructure obtained by high-resolution acoustic microscopy technique in frequencies range of 50-400 MHz. Development of the microstructure of the adhesive as it cures at different conditions has been investigated. Appearance and development of the granular structure on the adhesive interface during cure reaction has been demonstrated. Acoustic images were analyzed by mathematical method to quantitatively characterize distribution of the adhesive's components. Statistical analysis of such images provides an accurate quantitative measure of the degree of cure of such samples. Research results presented in this paper can be useful as a basis for non-destructive evaluation of the adhesive materials

  17. Efficient modeling of flat and homogeneous acoustic treatments for vibroacoustic finite element analysis. Finite size correction by image sources

    NASA Astrophysics Data System (ADS)

    Alimonti, L.; Atalla, N.

    2017-02-01

    This work is concerned with the hybrid finite element-transfer matrix methodology recently proposed by the authors. The main assumption behind this hybrid method consists in neglecting the actual finite lateral extent of the acoustic treatment. Although a substantial increase of the computational efficiency can be achieved, the effect of the reflected field (i.e. finite size effects) may be sometimes important, preventing the hybrid model from giving quantitative meaningful results. For this reason, a correction to account for wave reflections at the lateral boundaries of the acoustic treatment is sought. It is shown in the present paper that the image source method can be successfully employed to retrieve such finite size effects. Indeed, such methodology is known to be effective when the response of the system is a smooth function of the frequency, like in the case of highly dissipative acoustic treatments. The main concern of this paper is to assess accuracy and feasibility of the image source method in the context of acoustic treatments modeling. Numerical examples show that the performance of the standard hybrid model can be substantially improved by the proposed correction without deteriorating excessively the computational efficiency.

  18. Eigenanalysis Applied To Digital Images Of Human Chromosomes

    NASA Astrophysics Data System (ADS)

    Jericevic, Zeljko; Wiese, Brent A.; Smith, Louis C.; McGavran, Lorris; Carstens, B.; Castleman, Kenneth R.; Winkler, Donald G.

    1989-06-01

    Eigenanalysis is a powerful mathematical technique for analyzing matrices of data. With the data matrix constructed from a digitized image of a chromosome, this technique can be used to extract the features of the image, such as the chromosome banding pattern. The study of chromosome banding patterns represented by their pixel values in the images is based on eigenanalysis of the correlation or covariance matrix. Since the resulting eigenvectors are orthogonal, the information in each vector is excluded from all other vectors. Alternatively, the singular value decomposition method can be used to represent the data matrix as sum of its outer products, thereby avoiding the construction of a correlation/covariance matrix. Both procedures allow the sorting of information according to its significance, because the most significant information is associated with highest eigenvalues and corresponding eigenvectors. Consequently, the original data can be reconstituted using only the significant information. The advantage of this processing is that the preparatory artifacts and noise in the image are removed from the data before a recognition procedure is begun. An additional feature of this technique is that multiple data sets can be combined and processed simultaneously to establish, using objective statistical criteria, prototypes for each chromosome. Accumulative analysis improves the prototypes, and consequently the classification procedure. Features from prophase human chromosome number four have been to illustrate the eigenanalysis. Chromosomes from different spreads and individuals were used. Comparison of our statistically determined prototype with schematic idiotype from the literature shows significant improvement in recognition for all chromosomes, reconstituted at the level of only the most significant eigenvector. This type of analysis can be used for objective comparison of the various chromosomal banding patterns created by Giemsa, fluorescent dyes

  19. Content-based image retrieval applied to bone age assessment

    NASA Astrophysics Data System (ADS)

    Fischer, Benedikt; Brosig, André; Welter, Petra; Grouls, Christoph; Günther, Rolf W.; Deserno, Thomas M.

    2010-03-01

    Radiological bone age assessment is based on local image regions of interest (ROI), such as the epiphysis or the area of carpal bones. These are compared to a standardized reference and scores determining the skeletal maturity are calculated. For computer-aided diagnosis, automatic ROI extraction and analysis is done so far mainly by heuristic approaches. Due to high variations in the imaged biological material and differences in age, gender and ethnic origin, automatic analysis is difficult and frequently requires manual interactions. On the contrary, epiphyseal regions (eROIs) can be compared to previous cases with known age by content-based image retrieval (CBIR). This requires a sufficient number of cases with reliable positioning of the eROI centers. In this first approach to bone age assessment by CBIR, we conduct leaving-oneout experiments on 1,102 left hand radiographs and 15,428 metacarpal and phalangeal eROIs from the USC hand atlas. The similarity of the eROIs is assessed by cross-correlation of 16x16 scaled eROIs. The effects of the number of eROIs, two age computation methods as well as the number of considered CBIR references are analyzed. The best results yield an error rate of 1.16 years and a standard deviation of 0.85 years. As the appearance of the hand varies naturally by up to two years, these results clearly demonstrate the applicability of the CBIR approach for bone age estimation.

  20. Infrared image denoising applied in infrared sound field measurement

    NASA Astrophysics Data System (ADS)

    Su, Zhiqiang; Shen, Guofeng

    2017-03-01

    The research made use of the heat property and explored the distribution of focused ultrasound field. In our experiments, we measured the distribution of heat sources, and then, calculated the distribution of focused ultrasound field via a liner relation. In the experiments, we got a series of infrared images with noise. It's such an important thing to find out a solution to get rid of the noise in those images in order to get an accurate focused ultrasound field distribution. So the investigation following is focused in finding out a filter which can remove most noise in the infrared charts and the distribution of ultrasound filed is not impacted. Experiments compared the effects of different filters by the index of - 6dB width of the temperature rise images. By this index, we can find out a filter which is the most suitable filter for keeping the distribution of focused ultrasound field in steady. All experiments, including simulations, semi-simulations and actual verification experiments used six filters to deal with the raw data to get -6dB width and signal to noise ratio. From the results of experiments, we drew a conclusion that gauss filter is the best to keep the distribution of focused ultrasound field in steady.

  1. Image reconstruction in photoacoustic tomography with variable speed of sound using a higher-order geometrical acoustics approximation.

    PubMed

    Modgil, Dimple; Anastasio, Mark A; La Rivière, Patrick J

    2010-01-01

    Previous research correcting for variable speed of sound in photoacoustic tomography (PAT) based on a generalized radon transform (GRT) model assumes first-order geometrical acoustics (GA) approximation. In the GRT model, the pressure is related to the optical absorption, in an acoustically inhomogeneous medium, through integration over nonspherical isochronous surfaces. Previous research based on the GRT model assumes that the path taken by acoustic rays is linear and neglects amplitude perturbations to the measured pressure. We have derived a higher-order GA expression that takes into account the first-order effect in the amplitude of the measured signal and higher-order perturbation to the travel times. The higher-order perturbation to travel time incorporates the effect of ray bending. Incorrect travel times can lead to image distortion and blurring. These corrections are expected to impact image quality and quantitative PAT. We have previously shown that travel-time corrections in 2-D suggest that perceivable differences in the isochronous surfaces can be seen when the second-order travel-time perturbations are taken into account with a 10% speed-of-sound variation. In this work, we develop iterative image reconstruction algorithms that incorporate this higher-order GA approximation assuming that the speed of sound map is known. We evaluate the effect of higher-order GA approximation on image quality and accuracy.

  2. Technical Note: Compact three-tesla magnetic resonance imager with high-performance gradients passes ACR image quality and acoustic noise tests.

    PubMed

    Weavers, Paul T; Shu, Yunhong; Tao, Shengzhen; Huston, John; Lee, Seung-Kyun; Graziani, Dominic; Mathieu, Jean-Baptiste; Trzasko, Joshua D; Foo, Thomas K-F; Bernstein, Matt A

    2016-03-01

    A compact, three-tesla magnetic resonance imaging (MRI) system has been developed. It features a 37 cm patient aperture, allowing the use of commercial receiver coils. Its design allows simultaneously for gradient amplitudes of 85 millitesla per meter (mT/m) sustained and 700 tesla per meter per second (T/m/s) slew rates. The size of the gradient system allows for these simultaneous performance targets to be achieved with little or no peripheral nerve stimulation, but also raises a concern about the geometric distortion as much of the imaging will be done near the system's maximum 26 cm field-of-view. Additionally, the fast switching capability raises acoustic noise concerns. This work evaluates the system for both the American College of Radiology's (ACR) MRI image quality protocol and the Food and Drug Administration's (FDA) nonsignificant risk (NSR) acoustic noise limits for MR. Passing these two tests is critical for clinical acceptance. In this work, the gradient system was operated at the maximum amplitude and slew rate of 80 mT/m and 500 T/m/s, respectively. The geometric distortion correction was accomplished by iteratively determining up to the tenth order spherical harmonic coefficients using a fiducial phantom and position-tracking software, with seventh order correction utilized in the ACR test. Acoustic noise was measured with several standard clinical pulse sequences. The system passes all the ACR image quality tests. The acoustic noise as measured when the gradient coil was inserted into a whole-body MRI system conforms to the FDA NSR limits. The compact system simultaneously allows for high gradient amplitude and high slew rate. Geometric distortion concerns have been mitigated by extending the spherical harmonic correction to higher orders. Acoustic noise is within the FDA limits.

  3. Technical Note: Compact three-tesla magnetic resonance imager with high-performance gradients passes ACR image quality and acoustic noise tests

    PubMed Central

    Weavers, Paul T.; Shu, Yunhong; Tao, Shengzhen; Huston, John; Lee, Seung-Kyun; Graziani, Dominic; Mathieu, Jean-Baptiste; Trzasko, Joshua D.; Foo, Thomas K.-F.; Bernstein, Matt A.

    2016-01-01

    Purpose: A compact, three-tesla magnetic resonance imaging (MRI) system has been developed. It features a 37 cm patient aperture, allowing the use of commercial receiver coils. Its design allows simultaneously for gradient amplitudes of 85 millitesla per meter (mT/m) sustained and 700 tesla per meter per second (T/m/s) slew rates. The size of the gradient system allows for these simultaneous performance targets to be achieved with little or no peripheral nerve stimulation, but also raises a concern about the geometric distortion as much of the imaging will be done near the system’s maximum 26 cm field-of-view. Additionally, the fast switching capability raises acoustic noise concerns. This work evaluates the system for both the American College of Radiology’s (ACR) MRI image quality protocol and the Food and Drug Administration’s (FDA) nonsignificant risk (NSR) acoustic noise limits for MR. Passing these two tests is critical for clinical acceptance. Methods: In this work, the gradient system was operated at the maximum amplitude and slew rate of 80 mT/m and 500 T/m/s, respectively. The geometric distortion correction was accomplished by iteratively determining up to the tenth order spherical harmonic coefficients using a fiducial phantom and position-tracking software, with seventh order correction utilized in the ACR test. Acoustic noise was measured with several standard clinical pulse sequences. Results: The system passes all the ACR image quality tests. The acoustic noise as measured when the gradient coil was inserted into a whole-body MRI system conforms to the FDA NSR limits. Conclusions: The compact system simultaneously allows for high gradient amplitude and high slew rate. Geometric distortion concerns have been mitigated by extending the spherical harmonic correction to higher orders. Acoustic noise is within the FDA limits. PMID:26936710

  4. Differential diagnosis of idiopathic granulomatous mastitis and breast cancer using acoustic radiation force impulse imaging.

    PubMed

    Teke, Memik; Teke, Fatma; Alan, Bircan; Türkoğlu, Ahmet; Hamidi, Cihad; Göya, Cemil; Hattapoğlu, Salih; Gumus, Metehan

    2017-01-01

    Differentiation of idiopathic granulomatous mastitis (IGM) from carcinoma with routine imaging methods, such as ultrasonography (US) and mammography, is difficult. Therefore, we evaluated the value of a newly developed noninvasive technique called acoustic radiation force impulse imaging in differentiating IGM versus malignant lesions in the breast. Four hundred and eighty-six patients, who were referred to us with a presumptive diagnosis of a mass, underwent Virtual Touch tissue imaging (VTI; Siemens) and Virtual Touch tissue quantification (VTQ; Siemens) after conventional gray-scale US. US-guided percutaneous needle biopsy was then performed on 276 lesions with clinically and radiologically suspicious features. Malignant lesions (n = 122) and IGM (n = 48) were included in the final study group. There was a statistically significant difference in shear wave velocity marginal and internal values between the IGM and malignant lesions. The median marginal velocity for IGM and malignant lesions was 3.19 m/s (minimum-maximum 2.49-5.82) and 5.05 m/s (minimum-maximum 2.09-8.46), respectively (p < 0.001). The median internal velocity for IGM and malignant lesions was 2.76 m/s (minimum-maximum 1.14-4.12) and 4.79 m/s (minimum-maximum 2.12-8.02), respectively (p < 0.001). The combination of VTI and VTQ as a complement to conventional US provides viscoelastic properties of tissues, and thus has the potential to increase the specificity of US.

  5. In Vivo Study of Transverse Carpal Ligament Stiffness Using Acoustic Radiation Force Impulse (ARFI) Imaging

    PubMed Central

    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 IQTM 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

  6. Advanced imaging microscope tools applied to microgravity research investigations

    NASA Astrophysics Data System (ADS)

    Peterson, L.; Samson, J.; Conrad, D.; Clark, K.

    1998-01-01

    The inability to observe and interact with experiments on orbit has been an impediment for both basic research and commercial ventures using the shuttle. In order to open the frontiers of space, the Center for Microgravity Automation Technology has developed a unique and innovative system for conducting experiments at a distance, the ``Remote Scientist.'' The Remote Scientist extends laboratory automation capability to the microgravity environment. While the Remote Scientist conceptually encompasses a broad spectrum of elements and functionalities, the development approach taken is to: • establish a baseline capability that is both flexible and versatile • incrementally augment the baseline with additional functions over time. Since last year, the application of the Remote Scientist has changed from protein crystal growth to tissue culture, specifically, the development of skeletal muscle under varying levels of tension. This system includes a series of bioreactor chambers that allow for three-dimensional growth of muscle tissue on a membrane suspended between the two ends of a programmable force transducer that can provide automated or investigator-initiated tension on the developing tissue. A microscope objective mounted on a translation carriage allows for high-resolution microscopy along a large area of the tissue. These images will be mosaiced on orbit to detect features and structures that span multiple images. The use of fluorescence and pseudo-confocal microscopy will maximize the observational capabilities of this system. A series of ground-based experiments have been performed to validate the bioreactor, the force transducer, the translation carriage and the image acquisition capabilities of the Remote Scientist. • The bioreactor is capable of sustaining three dimensional tissue culture growth over time. • The force transducer can be programmed to provide static tension on cells or to simulate either slow or fast growth of underlying tissues in

  7. Event-based image recognition applied in tennis training assistance

    NASA Astrophysics Data System (ADS)

    Wawrzyniak, Zbigniew M.; Kowalski, Adam

    2016-09-01

    This paper presents a concept of a real-time system for individual tennis training assistance. The system is supposed to provide user (player) with information on his strokes accuracy as well as other training quality parameters such as velocity and rotation of the ball during its flight. The method is based on image processing methods equipped with developed explorative analysis of the events and their description by parameters of the movement. There has been presented the concept for further deployment to create a complete system that could assist tennis player during individual training.

  8. High Resolution Ultrasound Superharmonic Perfusion Imaging: In Vivo Feasibility and Quantification of Dynamic Contrast-Enhanced Acoustic Angiography.

    PubMed

    Lindsey, Brooks D; Shelton, Sarah E; Martin, K Heath; Ozgun, Kathryn A; Rojas, Juan D; Foster, F Stuart; Dayton, Paul A

    2017-04-01

    Mapping blood perfusion quantitatively allows localization of abnormal physiology and can improve understanding of disease progression. Dynamic contrast-enhanced ultrasound is a low-cost, real-time technique for imaging perfusion dynamics with microbubble contrast agents. Previously, we have demonstrated another contrast agent-specific ultrasound imaging technique, acoustic angiography, which forms static anatomical images of the superharmonic signal produced by microbubbles. In this work, we seek to determine whether acoustic angiography can be utilized for high resolution perfusion imaging in vivo by examining the effect of acquisition rate on superharmonic imaging at low flow rates and demonstrating the feasibility of dynamic contrast-enhanced superharmonic perfusion imaging for the first time. Results in the chorioallantoic membrane model indicate that frame rate and frame averaging do not affect the measured diameter of individual vessels observed, but that frame rate does influence the detection of vessels near and below the resolution limit. The highest number of resolvable vessels was observed at an intermediate frame rate of 3 Hz using a mechanically-steered prototype transducer. We also demonstrate the feasibility of quantitatively mapping perfusion rate in 2D in a mouse model with spatial resolution of ~100 μm. This type of imaging could provide non-invasive, high resolution quantification of microvascular function at penetration depths of several centimeters.

  9. Method of images applied to driven solid-state emitters

    NASA Astrophysics Data System (ADS)

    Scerri, Dale; Santana, Ted S.; Gerardot, Brian D.; Gauger, Erik M.

    2017-04-01

    Increasing the collection efficiency from solid-state emitters is an important step towards achieving robust single-photon sources, as well as optically connecting different nodes of quantum hardware. A metallic substrate may be the most basic method of improving the collection of photons from quantum dots, with predicted collection efficiency increases of up to 50%. The established "method-of-images" approach models the effects of a reflective surface for atomic and molecular emitters by replacing the metal surface with a second fictitious emitter which ensures appropriate electromagnetic boundary conditions. Here, we extend the approach to the case of driven solid-state emitters, where exciton-phonon interactions play a key role in determining the optical properties of the system. We derive an intuitive polaron master equation and demonstrate its agreement with the complementary half-sided cavity formulation of the same problem. Our extended image approach offers a straightforward route towards studying the dynamics of multiple solid-state emitters near a metallic surface.

  10. Feature selection applied to ultrasound carotid images segmentation.

    PubMed

    Rosati, Samanta; Molinari, Filippo; Balestra, Gabriella

    2011-01-01

    The automated tracing of the carotid layers on ultrasound images is complicated by noise, different morphology and pathology of the carotid artery. In this study we benchmarked four methods for feature selection on a set of variables extracted from ultrasound carotid images. The main goal was to select those parameters containing the highest amount of information useful to classify the pixels in the carotid regions they belong to. Six different classes of pixels were identified: lumen, lumen-intima interface, intima-media complex, media-adventitia interface, adventitia and adventitia far boundary. The performances of QuickReduct Algorithm (QRA), Entropy-Based Algorithm (EBR), Improved QuickReduct Algorithm (IQRA) and Genetic Algorithm (GA) were compared using Artificial Neural Networks (ANNs). All methods returned subsets with a high dependency degree, even if the average classification accuracy was about 50%. Among all classes, the best results were obtained for the lumen. Overall, the four methods for feature selection assessed in this study return comparable results. Despite the need for accuracy improvement, this study could be useful to build a pre-classifier stage for the optimization of segmentation performance in ultrasound automated carotid segmentation.

  11. Pulmonary imaging after stereotactic radiotherapy—does RECIST still apply?

    PubMed Central

    Mattonen, Sarah A; Ward, Aaron D

    2016-01-01

    The use of stereotactic ablative radiotherapy (SABR) for the treatment of primary lung cancer and metastatic disease is rapidly increasing. However, the presence of benign fibrotic changes on CT imaging makes response assessment following SABR a challenge, as these changes develop with an appearance similar to tumour recurrence. Misclassification of benign fibrosis as local recurrence has resulted in unnecessary interventions, including biopsy and surgical resection. Response evaluation criteria in solid tumours (RECIST) are widely used as a universal set of guidelines to assess tumour response following treatment. However, in the context of non-spherical and irregular post-SABR fibrotic changes, the RECIST criteria can have several limitations. Positron emission tomography can also play a role in response assessment following SABR; however, false-positive results in regions of inflammatory lung post-SABR can be a major clinical issue and optimal standardized uptake values to distinguish fibrosis and recurrence have not been determined. Although validated CT high-risk features show a high sensitivity and specificity for predicting recurrence, most recurrences are not detected until more than 1-year post-treatment. Advanced quantitative radiomic analysis on CT imaging has demonstrated promise in distinguishing benign fibrotic changes from local recurrence at earlier time points, and more accurately, than physician assessment. Overall, the use of RECIST alone may prove inferior to novel metrics of assessing response. PMID:27245137

  12. 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.

  13. 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.

  14. 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.

  15. Study of consolidating materials applied on wood by hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Bonifazi, G.; Serranti, S.; Capobianco, G.; Agresti, G.; Calienno, L.; Picchio, R.; Lo Monaco, A.; Santamaria, U.; Pelosi, C.

    2016-05-01

    The focus of this study was addressed to investigate the potentiality of HyperSpectral Imaging (HSI) in the monitoring of commercial consolidant products applied on wood samples. Poplar (Populus Sp.) and walnut (Juglans Regia L.) were chosen for the consolidant application. Both traditional and innovative products were selected, based on acrylic, epoxy and aliphatic compounds. Wood samples were stresses by freeze/thaw cycles in order to cause material degradation. Then the consolidants were applied under vacuum. The samples were finally artificially aged for 168 hours in a solar box chamber. The samples were acquired in the SWIR (1000-2500 nm) range by SISUChema XL™ device (Specim, Finland) after 168 hours of irradiation. As comparison, color measurement was also used as economic, simple and noninvasive technique to evaluate the deterioration and consolidation effects on wood. All data were then processed adopting a chemometric approach finalized to define correlation models, HSI based, between consolidating materials, wood species and short time ageing effects.

  16. Motion of a solid sphere in a viscoelastic medium in response to applied acoustic radiation force: Theoretical analysis and experimental verification.

    PubMed

    Aglyamov, Salavat R; Karpiouk, Andrei B; Ilinskii, Yurii A; Zabolotskaya, Evgenia A; Emelianov, Stanislav Y

    2007-10-01

    The motion of a rigid sphere in a viscoelastic medium in response to an acoustic radiation force of short duration was investigated. Theoretical and numerical studies were carried out first. To verify the developed model, experiments were performed using rigid spheres of various diameters and densities embedded into tissue-like, gel-based phantoms of varying mechanical properties. A 1.5 MHz, single-element, focused transducer was used to apply the desired radiation force. Another single-element, focused transducer operating at 25 MHz was used to track the displacements of the sphere. The results of this study demonstrate good agreement between theoretical predictions and experimental measurements. The developed theoretical model accurately describes the displacement of the solid spheres in a viscoelastic medium in response to the acoustic radiation force.

  17. Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity.

    PubMed

    Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T; Wang, Ruikang K; O'Donnell, Matthew

    2016-12-23

    Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea.

  18. Pancreatic Elastography From Acoustic Radiation Force Impulse Imaging for Evaluation of Diabetic Microangiopathy.

    PubMed

    He, Yu; Wang, Hui; Li, Xiao Ping; Zheng, Juan-Juan; Jin, Chun-Xiang

    2017-10-01

    The purposes of this study were to compare pancreatic shear-wave velocity (SWV) in subjects with and those without diabetic microvascular complications and to investigate the feasibility of pancreatic SWV in evaluating diabetic microangiopathy. SWV measurements were prospectively performed in 115 patients with diabetes mellitus and 115 healthy persons by use of acoustic radiation force impulse imaging. Patients with diabetes were divided into subgroups with and without microangiopathy. Pancreatic SWV was compared in three groups. Factors associated with increased SWV were studied. Pancreatic SWV increased significantly in the subgroups with diabetes mellitus compared with the control group (p < 0.01). Especially, the SWV in the pancreatic body was significantly higher when microangiopathy was present (p < 0.01). In patients with diabetes, microangiopathy (standardized β = 0.208, p = 0.022), age (standardized β = 0.265, p = 0.004), and total cholesterol level (standardized β = 0.223, p = 0.011) were positively and markedly correlated with high SWV in the pancreatic body. The increased SWV in the pancreatic body was significantly related to the presence of microangiopathy. It is feasible to use SWV in the pancreatic body to evaluate diabetic microangiopathy.

  19. 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

  20. Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

    NASA Astrophysics Data System (ADS)

    Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2016-12-01

    Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea.

  1. Three-dimensional acoustic imaging with planar microphone arrays and compressive sensing

    NASA Astrophysics Data System (ADS)

    Ning, Fangli; Wei, Jingang; Qiu, Lianfang; Shi, Hongbing; Li, Xiaofan

    2016-10-01

    For obtaining super-resolution source maps, we extend compressive sensing (CS) to three-dimensional acoustic imaging. Source maps are simulated with a planar microphone array and a CS algorithm. Comparing the source maps of the CS algorithm with those of the conventional beamformer (CBF) and Tikhonov Regularization (TIKR), we find that the CS algorithm is computationally more effective and can obtain much higher resolution source maps than the CBF and TIKR. The effectiveness of the CS algorithm is analyzed. The CS algorithm can locate the sound sources exactly when the frequency is above 4000 Hz and the signal-to-noise ratio (SNR) is above 12 dB. The location error of the CS algorithm increases as the frequency drops below the threshold, and the errors in location and power increase as SNR decreases. The further from the array the source is, the larger the location error is. The lateral resolution of the CS algorithm is much better than the range resolution. Finally, experimental measurements are conducted in a semi-anechoic room. Two mobile phones are served as sound sources. The results show that the CS algorithm can reconstruct two sound sources near the bottom of the two mobile phones where the speakers are located. The feasibility of the CS algorithm is also validated with the experiment.

  2. 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.

  3. Acoustic micro-tapping for non-contact 4D imaging of tissue elasticity

    PubMed Central

    Ambroziński, Łukasz; Song, Shaozhen; Yoon, Soon Joon; Pelivanov, Ivan; Li, David; Gao, Liang; Shen, Tueng T.; Wang, Ruikang K.; O’Donnell, Matthew

    2016-01-01

    Elastography plays a key role in characterizing soft media such as biological tissue. Although this technology has found widespread use in both clinical diagnostics and basic science research, nearly all methods require direct physical contact with the object of interest and can even be invasive. For a number of applications, such as diagnostic measurements on the anterior segment of the eye, physical contact is not desired and may even be prohibited. Here we present a fundamentally new approach to dynamic elastography using non-contact mechanical stimulation of soft media with precise spatial and temporal shaping. We call it acoustic micro-tapping (AμT) because it employs focused, air-coupled ultrasound to induce significant mechanical displacement at the boundary of a soft material using reflection-based radiation force. Combining it with high-speed, four-dimensional (three space dimensions plus time) phase-sensitive optical coherence tomography creates a non-contact tool for high-resolution and quantitative dynamic elastography of soft tissue at near real-time imaging rates. The overall approach is demonstrated in ex-vivo porcine cornea. PMID:28008920

  4. 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.

  5. Optically and acoustically triggerable sub-micron phase-change contrast agents for enhanced photoacoustic and ultrasound imaging.

    PubMed

    Lin, Shengtao; Shah, Anant; Hernández-Gil, Javier; Stanziola, Antonio; Harriss, Bethany I; Matsunaga, Terry O; Long, Nicholas; Bamber, Jeffrey; Tang, Meng-Xing

    2017-06-01

    We demonstrate a versatile phase-change sub-micron contrast agent providing three modes of contrast enhancement: 1) photoacoustic imaging contrast, 2) ultrasound contrast with optical activation, and 3) ultrasound contrast with acoustic activation. This agent, which we name 'Cy-droplet', has the following novel features. It comprises a highly volatile perfluorocarbon for easy versatile activation, and a near-infrared optically absorbing dye chosen to absorb light at a wavelength with good tissue penetration. It is manufactured via a 'microbubble condensation' method. The phase-transition of Cy-droplets can be optically triggered by pulsed-laser illumination, inducing photoacoustic signal and forming stable gas bubbles that are visible with echo-ultrasound in situ. Alternatively, Cy-droplets can be converted to microbubble contrast agents upon acoustic activation with clinical ultrasound. Potentially all modes offer extravascular contrast enhancement because of the sub-micron initial size. Such versatility of acoustic and optical 'triggerability' can potentially improve multi-modality imaging, molecularly targeted imaging and controlled drug release.

  6. Imaging Reservoir Siltation and Quaternary Stratigraphy Beneath the Mactaquac Headpond by Acoustic and Ground Penetrating Radar Sub-bottom Imaging

    NASA Astrophysics Data System (ADS)

    Grace, M.; Butler, K. E.; Peter, S.; Yamazaki, G.; Haralampides, K.

    2016-12-01

    The Mactaquac Hydroelectric Generating Station, located on the Saint John River in New Brunswick, Canada, is approaching the end of its life due to deterioration of the concrete structures. As part of an aquatic ecosystem study, designed to support a decision on the future of the dam, sediment in the headpond, extending 80 km upriver, is being examined. The focus of this sub-study lies in (i) mapping the thickness of sediments that have accumulated since inundation in 1968, and (ii) imaging the deeper glacial and post-glacial stratigraphy. Acoustic sub-bottom profiling surveys were completed during 2014 and 2015. An initial 3.5 kHz chirp sonar survey proved ineffective, lacking in both resolution and depth of the penetration. A follow-up survey employing a boomer-based "Seistec" sediment profiler provided better results, resolving sediment layers as thin as 12 cm, and yielding coherent reflections from the deeper Quaternary sediments. Post-inundation sediments in the lowermost 25 km of the headpond, between the dam and Bear Island, are interpreted to average 26 cm in thickness with the thickest deposits (up to 65 cm) in deep water areas overlying the pre-inundation riverbed west of Snowshoe Island, and south and east of Bear Island. A recent coring program confirmed the presence of silty sediment and showed good correlation with the Seistec thickness estimates. In the 15 km stretch upriver of Bear Island to Nackawic, the presence of gas in the uppermost sediments severely limits sub-bottom penetration and our ability to interpret sediment thicknesses. Profiles acquired in the uppermost 40 km reach of the headpond, extending to Woodstock, show a strong, positive water bottom reflection and little to no sub-bottom penetration, indicating the absence of soft post-inundation sediment. Deeper reflections observed within 5 km of the dam reveal a buried channel cut into glacial till, extending up to 20 m below the water bottom. Channel fill includes a finely laminated

  7. 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.

  8. [Acoustic radiation force impulse imaging elastography is efficacious in detecting hepatic fibrosis in children].

    PubMed

    Picó Aliaga, S D; Muro Velilla, D; García-Martí, G; Sangüesa Nebot, C; Martí-Bonmatí, L

    2015-01-01

    To evaluate the diagnostic performance of acoustic radiation force impulse imaging (ARFI) in detecting significant hepatic fibrosis in children. Our hospital's ethics committee approved the study and all patients or their representatives provided informed written consent. We included 96 children (50 boys, 46 girls; mean age, 8 y). We also studied 16 volunteers without liver disease as controls and 80 patients with diseases that can lead to fibrosis and cirrhosis of the liver. The final sample included 31 patients with biopsies and the 16 controls. All patients underwent abdominal ultrasonography including Doppler imaging and elastography with ARFI. The ARFI value, expressed as velocity (m/s) of shear wave propagation through the tissue, was calculated by averaging 16 measurements in both liver lobes. We used one-way analysis of variance to compare means between groups; we set statistical significance at P<.05. We used Student's t-tests and chi-square tests for categorical data. The ARFI value in children with fibrosis ≥ F2 was higher (1.80±0.45m/s) than in controls and higher than in patients with F0-F1 (1.38±0.22m/s). The difference was significant (P<.001) for detecting F ≥ 2. Steatosis was not related with the ARFI value (Student's t-test, P>.84). Necroinflammatory activity was strongly associated with the ARFI value (Student's t-test, P<.01). Fibrosis and necroinflammatory activity w