Bioacoustics Research Lab
University of Illinois at Urbana-Champaign | Department of Electrical and Computer Engineering | Department of Bioengineering
Department of Statistics | Coordinated Science Laboratory | Beckman Institute | Food Science and Human Nutrition | Division of Nutritional Sciences | College of Engineering
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William D. O'Brien, Jr. publications:

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Your search for ultrasound produced 3296 results.

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Title Experimental and simulated ultrasonic characterization of complex damage in fused silica.
Author Martin LP, Chambers DH, Thomas GH.
Journal IEEE Trans UFFC
Volume
Year 2002
Abstract The growth of a laser-induced, surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 12-ns pulses of 1.053-microm wavelength light at a fluence of approximately 27 J/cm2. The ultrasonic data were acquired after each pulse of the laser beam for 19 pulses. In addition, optical images of the surface and subsurface damage shape were recorded after each pulse of the laser. The ultrasonic signal amplitude exhibited variations with the damage size, which were attributed to the subsurface morphology of the damage site. A mechanism for the observed ultrasonic data based on the interaction of the ultrasound with cracks radiating from the damage site was tested using two-dimensional numerical simulations. The simulated results exhibit qualitatively similar characteristics to the experimental data and demonstrate the usefulness of numerical simulation as an aid for ultrasonic signal interpretation. The observed sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in large aperture laser optics used in fusion energy research.


Title Experimental and simulated ultrasonic characterization of complex damage in fused silica.
Author Martin LP, Chambers DH, Thomas GH.
Journal IEEE Trans UFFC
Volume
Year 2002
Abstract The growth of a laser-induced. surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 12-ns pulses of 1.053-?m wavelength light at a fluence of ~27 J/cm2. The ultrasonic data were acquired after each pulse of the laser beam for 19 pulses. In addition, optical images of the surface and subsurface damage shape were recorded after each pulse of the laser. The ultrasonic signal amplitude exhibited variations with the damage size, which were attributed to the subsurface morphology of the damage site. A mechanism for the observed ultrasonic data based on the interaction of the ultrasound with cracks radiating from the damage site was tested using two-dimensional numerical simulations. The simulated results exhibit qualitatively similar characteristics to the experimental data and demonstrate the usefulness of numerical simulation as an aid for ultrasonic signal interpretation. The observed sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in large aperture laser optics used in fusion energy research.


Title Experimental and theoretical evaluation of microbubble behavior: Effect of transmitted phase and bubble size.
Author Morgan KE, Allen JS, Dayton PA, Chomas JE, Klibanov AL, Ferrara KW.
Journal IEEE Trans UFFC
Volume
Year 2000
Abstract Ultrasound contrast agents provide new opportunities to image vascular volume and flow rate directly. To accomplish this goal, new pulse sequences can be developed to detect specifically the presence of a microbubble or group of microbubbles. We consider a new scheme to detect the presence of contrast agents in the body by examining the effect of transmitted phase on the received echoes from single bubbles. In this study, three tools are uniquely combined to aid in the understanding of the effects of transmission parameters and bubble radius on the received echo. These tools allow for optical measurement of radial oscillations of single bubbles during insonation, acoustical study of echoes from single contrast agent bubbles, and the comparison of these experimental observations with theoretical predictions. A modified Herring equation with shell terms is solved for the time-dependent bubble radius and wall velocity, and these outputs are used to formulate the predicted echo from a single encapsulated bubble. The model is validated by direct comparison of the predicted radial oscillations with those measured optically. The transient bubble response is evaluated with a transducer excitation consisting of one-cycle pulses with a center frequency of 2.4-MHz. The experimental and theoretical results are in good agreement and predict that the transmission of two pulses with opposite polarity will yield similar time domain echoes with the first significant portion of the echo generated when the rarefactional half-cycle reaches the bubble. remainder of abstract not available.


Title Experimental and theoretical study of the scattering of focused ultrasound from microparticles in fluids.
Author Edwards PL, Jarzynski J.
Journal Proc Fiftieth Anniv Meet Acoust Soc Am
Volume
Year 1979
Abstract No Abstract Available.


Title Experimental application of ultrafast imaging to spectral tissue characterization
Author Garcia-Duitama, J, Han A, Chayer B, Garcia D, Oelze ML, Cloutier G
Journal Ultrasound Med Biol
Volume
Year 2015
Abstract Ultrasound ultrafast imaging (UI) allows acquisition of thousands of frames per second with a sustained image quality at any depth in the field of view. Therefore, it would be ideally suited to obtain good statistical sampling of fast-moving tissues using spectral-based techniques to derive the backscatter coefficient (BSC) and associated quantitative parameters. In UI, an image is formed by insonifying the medium with plane waves steered at different angles, beamforming them and compounding the resulting radiofrequency images. We aimed at validating, experimentally, the effect of these beamforming protocols on the BSC, under both isotropic and anisotropic conditions. Using UI techniques with a linear array transducer (5–14 MHz), we estimated the BSCs of tissuemimicking phantoms and flowing porcine blood at depths up to 35 mm with a frame rate reaching 514 Hz. UI-based data were compared with those obtained using single-element transducers and conventional focusing imaging. Results revealed that UI compounded images can produce valid estimates of BSCs and effective scatterer size (errors less than 2.2 ± 0.8 and 0.26 ± 0.2 dB for blood and phantom experiments, respectively). This work also describes the use of pre-compounded UI images (i.e., steered images) to assess the angular dependency of circulating red blood cells. We have concluded that UI data sets can be used for BSC spectral tissue analysis and anisotropy characterization. (E-mail:guy.cloutier@umontreal.ca)


Title Experimental assessment of spectrum analysis of ultrasonic echoes as a method for estimating scatterer properties.
Author Hosokawa T, Sigel B, Machi J, Kitamura H, Kolecki RV, Justin JR, Feleppa EJ, Tuszynski G, Kakegawa T.
Journal Ultrasound Med Biol
Volume
Year 1994
Abstract In vitro experiments using weak scatterers ranging in size from mean longest diameter of 26.9 to 83.0 microns were performed to test the validity of theoretical predictions for scatterer size and concentration derived from normalized power spectrum parameters of ultrasonic backscatterer echoes. Scatterers consisting of cell clusters were suspended in collagen gel and scanned by a 10 MHz transducer system. Optical measurements validated theoretical predictions that (1) slope value is a function solely of scatterer size; (2) intercept value is a function of scatterer size and concentration; and (3) midband fit value increases as scatterer concentration increases, and, to a lesser extent, as size increases. These results were obtained under relatively ideal conditions of minimal attenuation and scatterer spacing (not closer than two scatterer diameters) and were consistent with the assumptions underlying the scattering theory.


Title Experimental cataract production by high frequency ultrasound.
Author Lizzi FL, Packer AJ, Coleman DJ.
Journal Ann Ophthalmol
Volume
Year 1978
Abstract In vivo animal experiments were performed to study the cataractogenic effects of high-frequency, high-intensity ultrasound. A series of anesthetized rabbits was insonified with quantified exposures of ultrasound using a 9.8 MHz focused ultrasonic beam. Ophthalmoscopic and slit lamp examinations revealed small haze cataracts as the first stage of lenticular damage. Larger exposures produced totally opaque cataracts. These first appeared as fine white threads surrounded by haze cataracts. The intensity-exposure time conjugates required to produce haze.cataracts were determined over times ranging from 35 msec to 5 sec. At short times (under 100 msec) a relatively constant amount of energy was needed for cataract production. At longer times, the requried energy progressively increased. This observation, together with the physical appearance of these cataracts, suggests that those lesions are the result of thermal phenomena.


Title Experimental demonstration of the frequency dependence of the effective scatterer number density.
Author Chen JF, Zagzebski JA, Madsen EL.
Journal J Acoust Soc Am
Volume
Year 1996
Abstract In previous papers, a data reduction method for determining a frequency-dependent "effective scatterer number density" in ultrasound was reported [Chen et al., J. Acoust. Soc. Am. 95, 77-95 (1994); 96, 2556-2563 (1994)]. The effective scatterer number density is the actual number density of scatterers multiplied by a frequency-dependent factor that depends on the differential scattering cross sections of the scatterers. Evaluation of this technique based on measurements applied to a phantom with a distribution of scatterer diameters is reported here. This condition yields an effective frequency. Measured scatterer number densities at 3.5, 5, and 8 MHz were in agreement with theoretical computations of this parameter for the phantom.


Title Experimental estimation of the viscous component of ultrasound attenuation in suspensions of bovine skeletal muscle myofibrils.
Author Shore, Miles CA.
Journal Proc Ultrason Symp IEEE
Volume
Year 1988
Abstract It has been suggested that viscous losses, caused by the motion of myofibrils relative to their environmental fluid, could be the major cause of ultrasound attenuation in muscle. This Paper presents theoretical and experimental estimates of the viscous component of attenuation in suspensions of myofibrils. Experimental estimates were made by monitoring the effects of varying the viscosity and density of the suspending fluid and ranged from 0.55 to 0.72 cm2 gāˆ’1 protein at 7 MHz, when expressed as mass attenuation coefficients. This represented 16ā€“22% of the total attenuation measured in suspensions. Corresponding theoretical calculations were lower: 0.44 and 0.21 cm2 gāˆ’1 protein, respectively, for suspensions with the myofibrils aligned along and across the direction of sound propagation. It was concluded that most of the attenuation was caused by other absorption processes.


Title Experimental evaluation of a prototype cylindrical section ultrasound hyperthermia phased-array applicator.
Author Ebbini ES, Cain CA.
Journal IEEE Trans UFFC
Volume
Year 1991
Abstract A prototype 64-element, 75? cylindrical-section ultrasonic phased-array hyperthermia applicator has been designed and constructed. The ability of this applicator to focus ultrasonic energy at its geometric focus was verified in a water medium. The array was then driven by excitation vectors obtained using the pseudoinverse pattern synthesis method to generate shifted-focus and multiple-focus field patterns. Experimental results of single and multiple-focus patterns at 500 kHz are given and are in good agreement with theory.


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