Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663308
R. McKeighen
The shape and symmetry of the pulser drive waveform and its interaction with the transducer and its tuning circuitry have a profound effect upon the pulse echo performance achievable from a medical transducer probe. Conventional wisdom has it that the shortest pulse obtainable, and subsequently the widest bandwidth achievable will come from the impulse response of the system. This study helps elucidate why an impulse generator may not always result in the shortest pulse and widest bandwidth. The pulse response is critically dependent upon the pulser drive symmetry, and its interaction with the reactance of the components making up the tuning topology. Unipolar pulses such as the spike impulse, or half wave square unipolar pulse drive, can create notches in the drive spectrum at the gold electrode that are deleterious, and significantly reduce available bandwidth. The transducer model used in this study is a 3.5 MHz 96 element sector phased array. In conjunction with a new innovative transducer acoustic design and optimized tuning, experimental results producing bandwidths of over 90% with clean, short pulse ringdown, have been achieved.
{"title":"Influence of pulse drive shape and tuning on the broadband response of a transducer","authors":"R. McKeighen","doi":"10.1109/ULTSYM.1997.663308","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663308","url":null,"abstract":"The shape and symmetry of the pulser drive waveform and its interaction with the transducer and its tuning circuitry have a profound effect upon the pulse echo performance achievable from a medical transducer probe. Conventional wisdom has it that the shortest pulse obtainable, and subsequently the widest bandwidth achievable will come from the impulse response of the system. This study helps elucidate why an impulse generator may not always result in the shortest pulse and widest bandwidth. The pulse response is critically dependent upon the pulser drive symmetry, and its interaction with the reactance of the components making up the tuning topology. Unipolar pulses such as the spike impulse, or half wave square unipolar pulse drive, can create notches in the drive spectrum at the gold electrode that are deleterious, and significantly reduce available bandwidth. The transducer model used in this study is a 3.5 MHz 96 element sector phased array. In conjunction with a new innovative transducer acoustic design and optimized tuning, experimental results producing bandwidths of over 90% with clean, short pulse ringdown, have been achieved.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"30 1","pages":"1637-1642 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83371018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663076
K. Suslick
The chemical effects of ultrasound originate from acoustic cavitation, which produces extremely energetic local transient conditions. In cavitating clouds of bubbles, both sonochemistry and sonoluminescence occur. Spectroscopic analysis of sonoluminescence from hydrocarbons and from metal carbonyls reveal temperatures of /spl sim/5000 K, /spl sim/1000 atm, with heating and cooling rates that exceed 10/sup 10/ K/s. Single bubble sonoluminescence produces much more symmetric bubble collapse with subsequently much higher effective temperatures during collapse. In cold liquids, bubble cloud cavitation is able to drive reactions that normally occur only under extreme conditions. Examples include activation of liquid-solid reactions and synthesis of amorphous and nanophase metals, and the synthesis of novel biomaterials, especially protein microspheres. Another remarkable phenomena occurs during ultrasonic irradiation of liquid-solid slurries: extremely high speed inter-particle collisions occur from cavitational shock waves at roughly half the speed of sound with effective temperatures of /spl sim/3000 K at the point of impact.
{"title":"Sonoluminescence and sonochemistry","authors":"K. Suslick","doi":"10.1109/ULTSYM.1997.663076","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663076","url":null,"abstract":"The chemical effects of ultrasound originate from acoustic cavitation, which produces extremely energetic local transient conditions. In cavitating clouds of bubbles, both sonochemistry and sonoluminescence occur. Spectroscopic analysis of sonoluminescence from hydrocarbons and from metal carbonyls reveal temperatures of /spl sim/5000 K, /spl sim/1000 atm, with heating and cooling rates that exceed 10/sup 10/ K/s. Single bubble sonoluminescence produces much more symmetric bubble collapse with subsequently much higher effective temperatures during collapse. In cold liquids, bubble cloud cavitation is able to drive reactions that normally occur only under extreme conditions. Examples include activation of liquid-solid reactions and synthesis of amorphous and nanophase metals, and the synthesis of novel biomaterials, especially protein microspheres. Another remarkable phenomena occurs during ultrasonic irradiation of liquid-solid slurries: extremely high speed inter-particle collisions occur from cavitational shock waves at roughly half the speed of sound with effective temperatures of /spl sim/3000 K at the point of impact.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"15 1","pages":"523-532 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87346622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663149
L. Lynnworth, L. Steingard, O.K. Khrakovsky, E. Machado, C. D. Smart, T.H. Nguyen
A solid waveguide of simple construction, and resembling a thin hockey stick, has been developed as a high-temperature clamp-on buffer to convey shear waves to hot pipes without dispersion, multipath or mode conversion problems. Buffer length of /spl sim/250 mm is generally adequate to isolate the piezoelectric shear wave element, whose frequency is typically 0.5, 1 or 2 MHz, from the high temperature. The buffer, passively cooled by ambient air convection, keeps the crystal cool, below 100/spl deg/C. This shear waveguide is typically clamped (but sometimes can be welded) to hot pipes (200 to 400/spl deg/C) to measure the flow of superheated water or hydrocarbon liquids. The present report covers (a) improved waveguide, yoke, and clamping means; (b) test results for prototype waveguides on 3" pipe; (c) measuring the decay rate of swirl in a plane /spl perp/ axis; (d) evaluating by means of clamp-on transducers, the transmission characteristics of narrow internal and external cavities in off-diameter planes that might be used for midradius or Gauss-Chebyshev quadrature integration of now profiles; (e) measuring liquid level in pipes whose axis is vertical, horizontal or tilted.
{"title":"Improved shear wave hockey stick transducer measures liquid flow and liquid level","authors":"L. Lynnworth, L. Steingard, O.K. Khrakovsky, E. Machado, C. D. Smart, T.H. Nguyen","doi":"10.1109/ULTSYM.1997.663149","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663149","url":null,"abstract":"A solid waveguide of simple construction, and resembling a thin hockey stick, has been developed as a high-temperature clamp-on buffer to convey shear waves to hot pipes without dispersion, multipath or mode conversion problems. Buffer length of /spl sim/250 mm is generally adequate to isolate the piezoelectric shear wave element, whose frequency is typically 0.5, 1 or 2 MHz, from the high temperature. The buffer, passively cooled by ambient air convection, keeps the crystal cool, below 100/spl deg/C. This shear waveguide is typically clamped (but sometimes can be welded) to hot pipes (200 to 400/spl deg/C) to measure the flow of superheated water or hydrocarbon liquids. The present report covers (a) improved waveguide, yoke, and clamping means; (b) test results for prototype waveguides on 3\" pipe; (c) measuring the decay rate of swirl in a plane /spl perp/ axis; (d) evaluating by means of clamp-on transducers, the transmission characteristics of narrow internal and external cavities in off-diameter planes that might be used for midradius or Gauss-Chebyshev quadrature integration of now profiles; (e) measuring liquid level in pipes whose axis is vertical, horizontal or tilted.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"26 1","pages":"865-870 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84689589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663070
A. Engebretson, B. Golding
The acoustic properties of evaporated polycrystalline niobium films have been studied to temperatures below 100 mK using surface acoustic waves. The experiments probe the process which occurs when hydrogen atoms tunnel between two nearly degenerate interstitial sites. The interaction of sound with tunneling defects leads to temperature dependent changes in acoustic absorption and velocity below 10 K. By analyzing the acoustic properties, we extract the tunneling system relaxation rates and their coupling strengths to electrons and phonons. The presence of the superconducting gap below T/sub c/ inhibits relaxation through the electronic channel allowing us to separate electronic and phononic decay paths.
{"title":"Surface acoustic wave propagation in Nb:H at low temperatures","authors":"A. Engebretson, B. Golding","doi":"10.1109/ULTSYM.1997.663070","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663070","url":null,"abstract":"The acoustic properties of evaporated polycrystalline niobium films have been studied to temperatures below 100 mK using surface acoustic waves. The experiments probe the process which occurs when hydrogen atoms tunnel between two nearly degenerate interstitial sites. The interaction of sound with tunneling defects leads to temperature dependent changes in acoustic absorption and velocity below 10 K. By analyzing the acoustic properties, we extract the tunneling system relaxation rates and their coupling strengths to electrons and phonons. The presence of the superconducting gap below T/sub c/ inhibits relaxation through the electronic channel allowing us to separate electronic and phononic decay paths.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"38 1","pages":"499-502 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90601325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663351
J. A. Jensen
Using linear acoustics the emitted and scattered ultrasound field can be found by using spatial impulse responses as developed by Tupholme (1969) and Stepanishen (1971). The impulse response is calculated by the Rayleigh integral by summing the spherical waves emitted from all of the aperture surface. The evaluation of the integral is cumbersome and quite involved for different aperture geometries. This paper re-investigates the problem and shows that the field can be found from the crossings between the boundary of the aperture and a spherical wave emitted from the field point onto the plane of the emitting aperture. Summing the angles of the arcs within the aperture readily yields the spatial impulse response for a point in space. The approach makes is possible to make very general calculation routines for arbitrary, flat apertures in which the outline of the aperture is either analytically or numerically defined. The exact field can then be found without evaluating any integrals by merely finding the zeros of the either the analytic or numerically defined functions. This makes it possible to describe the transducer surface using an arbitrary number of lines for the boundary. The approach can also be used for finding analytic solutions to the spatial impulse response for new geometries of, for example, ellipsoidal shape. The approach also makes it easy to incorporate any apodization function and the effect from different transducers baffle mountings. Examples of spatial impulse responses for a shape made from lines bounding the aperture is shown along with solutions for Gaussian apodized round transducer.
{"title":"A new approach to calculating spatial impulse responses","authors":"J. A. Jensen","doi":"10.1109/ULTSYM.1997.663351","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663351","url":null,"abstract":"Using linear acoustics the emitted and scattered ultrasound field can be found by using spatial impulse responses as developed by Tupholme (1969) and Stepanishen (1971). The impulse response is calculated by the Rayleigh integral by summing the spherical waves emitted from all of the aperture surface. The evaluation of the integral is cumbersome and quite involved for different aperture geometries. This paper re-investigates the problem and shows that the field can be found from the crossings between the boundary of the aperture and a spherical wave emitted from the field point onto the plane of the emitting aperture. Summing the angles of the arcs within the aperture readily yields the spatial impulse response for a point in space. The approach makes is possible to make very general calculation routines for arbitrary, flat apertures in which the outline of the aperture is either analytically or numerically defined. The exact field can then be found without evaluating any integrals by merely finding the zeros of the either the analytic or numerically defined functions. This makes it possible to describe the transducer surface using an arbitrary number of lines for the boundary. The approach can also be used for finding analytic solutions to the spatial impulse response for new geometries of, for example, ellipsoidal shape. The approach also makes it easy to incorporate any apodization function and the effect from different transducers baffle mountings. Examples of spatial impulse responses for a shape made from lines bounding the aperture is shown along with solutions for Gaussian apodized round transducer.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"59 1","pages":"1755-1759 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90636229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663001
J. Knuuttila, P. Tikka, V. Plessky, T. Thorvaldsson, M. Salomaa
Several improvements for our Michelson laser interferometer have been implemented. High frequency RF leakage has been suppressed to allow measurements at 1 GHz frequencies. Fast automatic computer-controlled focusing and high-precision XY-translation system provide two-dimensional scans with resolution better than one micrometer and with measuring speeds up to 7000 points/hour. At each probe point the interferometer can detect vibrations normal to the surface down to amplitudes on the order of an Angstrom. These advances, combined with the long working distance of the optical system, enable an efficient scanning of commercial SAW devices with speed and precision.
{"title":"Recent advances in laser-interferometric investigations of SAW devices","authors":"J. Knuuttila, P. Tikka, V. Plessky, T. Thorvaldsson, M. Salomaa","doi":"10.1109/ULTSYM.1997.663001","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663001","url":null,"abstract":"Several improvements for our Michelson laser interferometer have been implemented. High frequency RF leakage has been suppressed to allow measurements at 1 GHz frequencies. Fast automatic computer-controlled focusing and high-precision XY-translation system provide two-dimensional scans with resolution better than one micrometer and with measuring speeds up to 7000 points/hour. At each probe point the interferometer can detect vibrations normal to the surface down to amplitudes on the order of an Angstrom. These advances, combined with the long working distance of the optical system, enable an efficient scanning of commercial SAW devices with speed and precision.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"109 1","pages":"161-164 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91288649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.661861
Greg Wojcik, B. Fomberg, Robert C. Waag, L. Carcione, John Mould, L. Nikodym, T. Driscoll
Large-scale simulations of ultrasonic waves in heterogeneous tissue models are useful in biomedical R&D for imaging and therapeutics. The scale of bioacoustic models is hundreds of wavelengths. Typical 2D wave solvers are not practical at this scale, and 3D is out of the question, because of numerical errors and/or computer limits. To achieve much higher performance we use the periodic pseudospectral (PS) method, where spatial derivatives are calculated from FFTs over Cartesian grids. With a 4th order explicit time integrator, the PS method yields the necessary accuracy and efficiency. However, the domain must be periodic. We show how to circumvent this intrinsic limitation with Berenger's perfectly matched layer (PML) on the boundaries. High accuracy, computational efficiency, and parallelism are demonstrated and a large-scale bioacoustic model is calculated. Generalizations of the method are described, including attenuation and nonlinearity.
{"title":"Pseudospectral methods for large-scale bioacoustic models","authors":"Greg Wojcik, B. Fomberg, Robert C. Waag, L. Carcione, John Mould, L. Nikodym, T. Driscoll","doi":"10.1109/ULTSYM.1997.661861","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.661861","url":null,"abstract":"Large-scale simulations of ultrasonic waves in heterogeneous tissue models are useful in biomedical R&D for imaging and therapeutics. The scale of bioacoustic models is hundreds of wavelengths. Typical 2D wave solvers are not practical at this scale, and 3D is out of the question, because of numerical errors and/or computer limits. To achieve much higher performance we use the periodic pseudospectral (PS) method, where spatial derivatives are calculated from FFTs over Cartesian grids. With a 4th order explicit time integrator, the PS method yields the necessary accuracy and efficiency. However, the domain must be periodic. We show how to circumvent this intrinsic limitation with Berenger's perfectly matched layer (PML) on the boundaries. High accuracy, computational efficiency, and parallelism are demonstrated and a large-scale bioacoustic model is calculated. Generalizations of the method are described, including attenuation and nonlinearity.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"56 1","pages":"1501-1506 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89972081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663130
K. Yamamoto, E. Ohnok, A. Kokubo, K. Sakai, K. Takagi
The phase conjugate waves of ultrasound were generated with PZT ceramics through the nonlinear piezoelectric interaction between elastic field of incident ultrasound at /spl omega/ and electric field applied at 2/spl omega/. The amplitude reflectivity of the phase conjugation was shown to be as high as 30% for incidence at 10 MHz. The stroboscopic schlieren technique was used to visualize their behavior in water: the slow-motion video visually confirmed their time-reversal property. The phase conjugator of PZT was installed in a system of scanning acoustic imaging. A metal plate with letter-shaped holes as a target was put in an artificial disturber of sound waves and imaged. Normal images were also taken without the phase conjugator for comparison, which were seriously distorted and superimposed on a ghost due to the disturber. The image reconstructed of the phase conjugate reflection yielded clear figure of the targets in spite of the disturber. The usefulness of the phase conjugation phenomenon applied to the ultrasonic imaging was shown.
{"title":"Scanning imaging system with ultrasonic phase conjugator","authors":"K. Yamamoto, E. Ohnok, A. Kokubo, K. Sakai, K. Takagi","doi":"10.1109/ULTSYM.1997.663130","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663130","url":null,"abstract":"The phase conjugate waves of ultrasound were generated with PZT ceramics through the nonlinear piezoelectric interaction between elastic field of incident ultrasound at /spl omega/ and electric field applied at 2/spl omega/. The amplitude reflectivity of the phase conjugation was shown to be as high as 30% for incidence at 10 MHz. The stroboscopic schlieren technique was used to visualize their behavior in water: the slow-motion video visually confirmed their time-reversal property. The phase conjugator of PZT was installed in a system of scanning acoustic imaging. A metal plate with letter-shaped holes as a target was put in an artificial disturber of sound waves and imaged. Normal images were also taken without the phase conjugator for comparison, which were seriously distorted and superimposed on a ghost due to the disturber. The image reconstructed of the phase conjugate reflection yielded clear figure of the targets in spite of the disturber. The usefulness of the phase conjugation phenomenon applied to the ultrasonic imaging was shown.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"1 1","pages":"773-776 vol.1"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89614524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663315
M. Zipparo, K. Shung, T. Shrout
The design and fabrication of ultrasound transducers which operate above 20 MHz is discussed in relation to piezoelectric materials and their operation at high frequencies. Measurements are made of fine scale composites with operating frequencies up to 50 MHz. Simulations are presented for plate-mode and composite-mode 2 mm diameter single element transducers and the difference in performance between various materials is discussed. Composite-mode transducers are shown to result in wider bandwidth and shorter pulse length.
{"title":"Piezoceramics for high frequency (20-100 MHz) transducers and arrays","authors":"M. Zipparo, K. Shung, T. Shrout","doi":"10.1109/ULTSYM.1997.663315","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663315","url":null,"abstract":"The design and fabrication of ultrasound transducers which operate above 20 MHz is discussed in relation to piezoelectric materials and their operation at high frequencies. Measurements are made of fine scale composites with operating frequencies up to 50 MHz. Simulations are presented for plate-mode and composite-mode 2 mm diameter single element transducers and the difference in performance between various materials is discussed. Composite-mode transducers are shown to result in wider bandwidth and shorter pulse length.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"1 1","pages":"1663-1667 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76658017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-10-05DOI: 10.1109/ULTSYM.1997.663291
F. Forster
The acoustic field generated by an ultrasonic transducer radiating into a homogeneous medium is well understood, but generally accepted scattering models for biological tissue do not exist. To investigate the effects of scatterer model on diffraction filtering, two cases were considered. In both cases particles were randomly distributed in space; in one case random scattering amplitudes were allowed and in the other case particles behaved identically. In both cases the diffraction filter was a low-pass effect. However, at low frequencies the diffraction filter for identical scatterers was found to be steeper by a factor of three in slope (dB/MHz) for reasonable values of scatterer number density. The results of this study demonstrate that the characteristics of the scattering medium can significantly affect acoustic measurements.
{"title":"The effect of scatterer statistics on diffraction corrections","authors":"F. Forster","doi":"10.1109/ULTSYM.1997.663291","DOIUrl":"https://doi.org/10.1109/ULTSYM.1997.663291","url":null,"abstract":"The acoustic field generated by an ultrasonic transducer radiating into a homogeneous medium is well understood, but generally accepted scattering models for biological tissue do not exist. To investigate the effects of scatterer model on diffraction filtering, two cases were considered. In both cases particles were randomly distributed in space; in one case random scattering amplitudes were allowed and in the other case particles behaved identically. In both cases the diffraction filter was a low-pass effect. However, at low frequencies the diffraction filter for identical scatterers was found to be steeper by a factor of three in slope (dB/MHz) for reasonable values of scatterer number density. The results of this study demonstrate that the characteristics of the scattering medium can significantly affect acoustic measurements.","PeriodicalId":6369,"journal":{"name":"1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118)","volume":"282 1","pages":"1553-1556 vol.2"},"PeriodicalIF":0.0,"publicationDate":"1997-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77848330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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