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  • 1
    Online Resource
    Online Resource
    Broadband measurements of phase velocity in Albunex® suspensions
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 4 ( 1998-04-01), p. 2145-2153
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 4 ( 1998-04-01), p. 2145-2153
    Abstract: The phase velocities in suspensions of Albunex®, an ultrasound contrast agent, are determined using the technique of broadband phase spectroscopy. In these suspensions, phase velocities were measured as a function of Albunex concentration in Isoton II (buffered saline). The dispersion over the measurement bandwidth (1–15 MHz) grew with increasing Albunex concentration, exhibiting a 221-m/s change (17% increase) in phase velocity between 1.0 and 3.8 MHz at the highest concentration reported (32 μL Albunex/8 mL Isoton). The dispersion behavior of the Albunex suspensions is described using a model of encapsulated gas bubbles. The influence of the dispersion in Albunex on broadband pulses is discussed, as well as the potential impact this dispersion may have on the formation of ultrasonic images of the heart.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.421360
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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  • 2
    Online Resource
    Online Resource
    Discovery of sound in the sea: Webinars as a means of communicating current underwater acoustics research to decision makers
    Acoustical Society of America (ASA) ; 2018
    In:  The Journal of the Acoustical Society of America Vol. 144, No. 3_Supplement ( 2018-09-01), p. 1664-1664
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 144, No. 3_Supplement ( 2018-09-01), p. 1664-1664
    Abstract: Underwater sound used for anthropogenic activities is reviewed and restricted under a variety of environmental regulations. Decision makers must often synthesize rapidly new scientific research results to inform their assessments of potential impacts of proposed projects. To assist this need, the University of Rhode Island Graduate School of Oceanography has teamed with Marine Acoustics, Inc., in the Discovery of Sound in the Sea (DOSITS) project to provide accurate scientific information on underwater sound through a diversity of resources and digital platforms, including webinars. Building on the foundation of the successful 2015-2016 DOSITS webinar series and informed by the results of three international regulatory community needs assessments, the DOSITS project is hosting throughout 2018 a four-part webinar series on the fundamentals of underwater hearing and potential impacts of underwater sound on marine animals, particularly marine mammals (April–May) and fishes (November). Evaluation results from the first two webinars on marine mammals showed that 90% of survey respondents were very satisfied or satisfied with the content coverage, and 97% were extremely or very likely to attend future DOSITS webinars. The webinar approach has provided much needed on-the-job training for decision makers to effectively incorporate new scientific research into their evaluation processes.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5067419
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2018
    detail.hit.zdb_id: 1461063-2
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  • 3
    Online Resource
    Online Resource
    Frequency and concentration dependence of the backscatter coefficient of the ultrasound contrast agent Albunex®
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 104, No. 3 ( 1998-09-01), p. 1654-1666
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 104, No. 3 ( 1998-09-01), p. 1654-1666
    Abstract: A broadband ultrasonic measurement system has been utilized to characterize the concentration and frequency dependence of in vitro suspensions of Albunex® microspheres at concentrations ranging from 1.7×105 to 2.1×107 microspheres/mL and over a bandwidth of 1–16 MHz. The apparent backscattered power (not compensated for effects due to attenuation) was shown to increase with dose for lower concentrations of microspheres, but then to decrease rapidly with increasing concentration where attenuation effects become significant. Measurements of signal loss demonstrated that the attenuation grew exponentially with increasing concentration, so that a doubling of the number of microspheres led to a doubling of the value of the attenuation coefficient measured in dB/cm. This relationship was demonstrated over the entire system bandwidth. Compensation of the apparent backscattered power for the attenuation yielded the backscatter transfer function. This quantity was shown to be linearly proportional to concentration, so that a doubling of the number of microspheres led to a 3-dB increase in the backscatter transfer function. A broadband data reduction technique was used to further reduce the data to backscatter coefficient, an absolute parameter describing the intrinsic scattering efficiency of the Albunex® microsphere suspensions. The backscatter coefficient was shown to be linearly proportional to microsphere concentration at all concentrations investigated and over all the usable bandwidth. This suggests that, with appropriate compensation for attenuation and equipment parameters, perfusion or flow quantification techniques which assume a linear dependence of backscatter with contrast agent concentration should be applicable. The backscatter coefficient exhibits a rapid rise with frequency below 3 MHz, and appears to approach a frequency independent limit above 3 MHz. The relationships of the attenuation coefficient and backscatter transfer function to concentration were generally consistent with predictions from a simple scattering model. These relationships appear to be valid within the usable bandwidth of our measurement system for all concentrations investigated.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.424378
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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  • 4
    Online Resource
    Online Resource
    Erratum: “Kramers-Kronig relations applied to finite bandwidth data from suspensions of encapsulated microbubbles” [J. Acoust. Soc. Am. 108 , 2091–2106 (2000)]
    Acoustical Society of America (ASA) ; 2002
    In:  The Journal of the Acoustical Society of America Vol. 112, No. 2 ( 2002-08-01), p. 760-761
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 112, No. 2 ( 2002-08-01), p. 760-761
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.1494808
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2002
    detail.hit.zdb_id: 1461063-2
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  • 5
    Online Resource
    Online Resource
    Kramers–Kronig relations applied to finite bandwidth data from suspensions of encapsulated microbubbles
    Acoustical Society of America (ASA) ; 2000
    In:  The Journal of the Acoustical Society of America Vol. 108, No. 5 ( 2000-11-01), p. 2091-2106
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 108, No. 5 ( 2000-11-01), p. 2091-2106
    Abstract: In this work, the Kramers–Kronig (K–K) relations are applied to experimental data of resonant nature by limiting the interval of integration to the measurement spectrum. The data are from suspensions of encapsulated microbubbles (Albunex®) and have the characteristics of an ultrasonic notch filter. The goal is to test the consistency of this dispersion and attenuation data with the Kramers–Kronig relations in a strict manner, without any parameters from outside the experimental bandwidth entering in to the calculations. In the course of reaching the goal, the artifacts associated with the truncation of the integrals are identified and it is shown how their impacts on the results can be minimized. The problem is first approached analytically by performing the Kramers–Kronig calculations over a restricted spectral band on a specific Hilbert transform pair (Lorentzian curves). The resulting closed-form solutions illustrate the type of artifacts that can occur due to truncation and also show that accurate results can be achieved. Next, both twice-subtracted and lower-order Kramers–Kronig relations are applied directly to the attenuation and dispersion data from the encapsulated microbubbles. Only parameters from within the experimental attenuation coefficient and phase velocity data sets are used. The twice-subtracted K–K relations produced accurate estimates for both the attenuation coefficient and dispersion across all 12 data sets. Lower-order Kramers–Kronig relations also produced good results over the finite spectrum for most of the data. In 2 of the 12 cases, the twice-subtracted relations tracked the data markedly better than the lower-order predictions. These calculations demonstrate that truncation artifacts do not overwhelm the causal link between the phase velocity and the attenuation coefficient for finite bandwidth calculations. This work provides experimental evidence supporting the validity of the subtracted forms of the acoustic K–K relations between the phase velocity and attenuation coefficient.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.1312364
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2000
    detail.hit.zdb_id: 1461063-2
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  • 6
    Online Resource
    Online Resource
    Broadband measurements of the attenuation coefficient and backscatter coefficient for suspensions: A potential calibration tool
    Acoustical Society of America (ASA) ; 1997
    In:  The Journal of the Acoustical Society of America Vol. 101, No. 2 ( 1997-02-01), p. 1162-1171
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 101, No. 2 ( 1997-02-01), p. 1162-1171
    Abstract: Tissue characterization would be facilitated by improved methods of calibration with which to make absolute measurements of the backscatter and attenuation of tissue or contrast agents. In this paper, the use of polystyrene microspheres is examined as a potential broadband in vitro calibration tool by employing an experimental system designed to characterize ultrasonic contrast agents. The frequency-dependent attenuation coefficient and backscatter coefficient were measured for a series of microsphere size distributions with a broadband ultrasound system using a custom-built specimen chamber and a novel suspension mixing technique. The measurements were used in a broadband reduction method to yield the backscatter coefficient. The range of ka spanned in this study is from ka=0.5 to ka=12. The broadband nature of the pulses permitted simultaneous measurement of different regimes of scattering of the microspheres (specifically, the transition region from Rayleigh to short-wavelength asymptotic scattering). Experimental results were compared with corresponding theoretical predictions for the attenuation and backscatter of solid elastic spheres in liquid and yielded good quantitative agreement. Discussion of some possible applications of this technique to the fields of tissue characterization and contrast is presented.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.418020
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1997
    detail.hit.zdb_id: 1461063-2
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  • 7
    Online Resource
    Online Resource
    Broadband through-transmission signal loss measurements of Albunex® suspensions at concentrations approaching in vivo doses
    Acoustical Society of America (ASA) ; 1997
    In:  The Journal of the Acoustical Society of America Vol. 101, No. 2 ( 1997-02-01), p. 1155-1161
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 101, No. 2 ( 1997-02-01), p. 1155-1161
    Abstract: Broadband normalized signal loss of commercially available Albunex®, an ultrasonic contrast agent, was measured in vitro at concentrations approaching those which may be found in vivo for clinical doses. The measurements were made using a novel specimen chamber, careful material handling procedures, and a broadband square wave pulser system. Results were obtained over the full bandwidth of the experimental system (1 to 20 MHz) at concentrations up to 1.9×106 microspheres/mL. Further results were obtained over a partial bandwidth of the experimental system at concentrations up to 1.5×107 microspheres/mL. The frequency-dependent signal loss exhibited a peak for all concentrations investigated. In the meaningful bandwidth of the system, the signal loss (expressed in dB) was directly proportional to microsphere concentration. The experimental results for normalized signal loss were compared with predictions from a linear single-scattering model for encapsulated bubbles. The experimental data was used to estimate values for the two adjustable parameters in the model: microsphere shell elasticity (4200±1000 dyn/cm) and friction (0.0054±0.0015 dyn s/cm).
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.418270
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1997
    detail.hit.zdb_id: 1461063-2
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  • 8
    Online Resource
    Online Resource
    Measurements and predictions of the phase velocity and attenuation coefficient in suspensions of elastic microspheres
    Acoustical Society of America (ASA) ; 1999
    In:  The Journal of the Acoustical Society of America Vol. 106, No. 2 ( 1999-08-01), p. 652-659
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 106, No. 2 ( 1999-08-01), p. 652-659
    Abstract: The phase velocities and attenuation coefficients for suspensions of narrowly sized polymer microspheres are reported over a broadband spectrum from 3 to 30 MHz. The six suspensions used in this work contain microspheres with respective average diameters near 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, and 100 μm. The results of these measurements are compared with theoretical expressions for the phase velocity and attenuation coefficient derived from the scattering properties of an elastic sphere in water using the weak scattering limit of the Waterman and Truell dispersion relation [J. Math. Phys. 2, 512–537 (1961)]. This single-scattering limit of the theory is found to be sufficient for predicting the ultrasonic transport properties of these suspensions to a considerable degree of accuracy.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.427139
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1999
    detail.hit.zdb_id: 1461063-2
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