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 Theoretical considerations in relation to the treatment.of brain tumours by means of local hyperthermia.generated by ultrasound fields.
Author Quan KM, Watmough DJ, Mallard JR.
Journal Eur J Surg Oncol
Volume
Year 1991
Abstract Brain tumours comprise a significant fraction of all tumours in the human body. Despite the development of technology in clinical oncology, these tumours still present a difficult challenge. The margin between destruction of tumour and damage to normal tissue is narrow in the brain. The price paid for producing tissue damage outside the tumour is high in terms of quality of survival. Results of many experiments with ultrasound hyperthermia show that this new technique is successful for treating certain types of malignant tumours. In the case of brain tumours, applying focused fields should have the advantage of selectively destroying the tumour and leaving surrounding tissues intact. Previous attempts at applying ultrasound to the field of neurosurgery are reviewed. Those factors which have effects on the generation of thermal fields in brain tissues are considered in relation to the possible treatment of human brain tumours. Calculated thermal fields in a 2-D brain model generated by an applicator built in our laboratory are also presented.


Title Theoretical considerations of ultrasound back-scatter. [in German]
Author Fay B.
Journal Acustica
Volume
Year 1973
Abstract Non-destructive structure testing with ultrasound using the impulse-echo method on materials with localised structure only yields the attenuation constant averaged over the sound path. Using theoretical considerations it will be shown that by the method of ultrasonic backscatter one can calculate the change of backscatter and absorption coefficient in materials.


Title Theoretical framework for spectrum analysis in ultrasonic tissue characterization.
Author Lizzi FL, Greenebaum M, Feleppa EJ, Elbaum M, Coleman DJ.
Journal J Acoust Soc Am
Volume
Year 1983
Abstract An analytic model is described for application in ultrasonic tissue characterization. The model is applicable to clinical broadband pulse echo systems. It treats spectra derived from received echo signals and relates them to physical tissue properties. The model can be applied to deterministic tissue structures (e.g., retinal detachments, larger blood vessels, and surface layers of the kidney) and to stochastic tissue structures (e.g., various tumors). The beam patterns included in the model are those generated by focused transducers typically used in high-resolution clinical ultrasound. Appropriate calibration procedures are also treated; these are needed for interpretation of absolute spectral parameters. The results obtained with the analytic model have been used to design a digital processing system and the associated techniques which are now being applied during examinations of the eye and abdominal organs. The results have proven useful in interpreting data from various types of tissues. To illustrate the application of these results, representative clinical data, obtained from the digital system, are presented for two types of tissue architectures. The first case is a detached retina representing a deterministic structure characterized by well-defined thickness and reflection coefficients. The second case is asteroid hyalosis and represents a stochastic entity in which the positions of small scattering particles are best described in statistical terms, and characterization is accompanied by means of normalized power spectra.


Title Theoretical investigation of the response of gas-filled micropores and cavitation nuclei to ultrasound.
Author Miller DL, Nyborg WL.
Journal J Acoust Soc Am
Volume
Year 1983
Abstract Theory is discussed for the transverse oscillation of a small circular interface set into a rigid baffle between gas and liquid. The angular resonance frequency is given by (15πT/4ρa3)1/2, in which a is the radius of the interface, T is the interfacial surface tension, and ρ is the density of the liquid. Damping parameters are obtained for the radiation, viscous, and boundary‐layer mechanisms of dissipation. This model system is extended for discussion of the pulsation of gas trapped in a pit or cavity in a solid, which may simulate one type of cavitation nucleus, and straight‐through cylindrical holes or pores in a solid sheet, which is applicable to the hydrophobic membranes with gas‐trapping micropores used in studies of biological effects produced by ultrasound. Fixed and free conditions at the three‐phase line at the periphery of an interface are considered. Finally, the partially gas‐filled cavity is treated, and also the partially gas‐filled pore with two interfaces which have different mass, stiffness, and damping parameters. The results of these theoretical considerations are expected to be of value for quantitatively evaluating that specific form of stable cavitation which involves the direct activation of pre‐existing, stable bodies of gas into ultrasonic pulsation, as experimentally observed, for example, by D. Miller, J. Acoust. Soc. Am. 71, 471–476 (1982).


Title Theoretical modeling of the acoustic scattering structure of human liver.
Author Bamber JC.
Journal Acoust Lett
Volume
Year 1979
Abstract Published experimental data on the scattering of ultrasound by human liver are examined in the light of a simple inhomogeneous continuum model and are found to yield no consensus with regard to a characteristic size of scattering structure. By comparing experimental data on the frequency dependence of backscattering with predictions from currently used theoretical models, it is demonstrated that random fluctuations in compressibility governed by simple Guassian and exponential autocorrelation functions do not appear to be realistic descriptions of the acoustic scattering structure of human liver. A three-level model is therefore proposed in which the scattering is assumed to arise from superimposed structures with characteristic dimensions corresponding to cells, the liver parenchyma, and larger structures such as blood vessels. With this model, which appears to give improved correlation with the observed data, the choice of particular experimental parameters for a scattering experiment is considered to result in selection of a spatial frequency "window" in the observation of different levels of structure.


Title Theoretical results for new cylindrical ultrasound phased array for prostate treatment.
Author Frizzell LA, Tan JS, Warren GM.
Journal Proc Second Int Symp Ther Ultrasound
Volume
Year 2002
Abstract Several groups have examined the design of ultrasound phased arrays for transrectal treatment of the prostate. An effective design must utilize the entire aperture of the array and maintain relatively low grating lobe intensities, ideally while minimizing the number of elements and associated phasing circuitry. In this continuation of our studies to design an array that meets these requirements we examined theoretically a new approach to the design of a cylindrical array. Previous designs have subdivided the cylindrical aperture into several columns of elements oriented along the array length, each with the same center-to-center spacing between adjacent elements. Columns of elements are paired, with the same phasing applied to each of the two corresponding elements within a pair, due to symmetry that applies when focus formation and scanning are limited to a plane bisecting the array in the lengthwise direction. Here we report the results obtained for a novel array where the center-to-center spacing is different for different column pairs. This results in a different location for the grating lobes associated with each column pair, which then no longer reinforce each other. When performance was examined by determining the ratio of the peak focal intensity relative to the maximum intensity of unwanted lobes, G, this array design performed much better than previous designs that we have examined. It was possible to achieve values for G that stayed above 7 when steering the focus 15 mm in either depth of lengthwise directions from its unsteered location.


Title Theory of ultrasonic absorption in concentrated polymeric solutions.
Author Gotlib YY, Salikhov KM.
Journal Sov Phys Acoust
Volume
Year 1964 [1963]
Abstract A theory is proposed to interpret the absorption of ultrasound in concentrated polymer solutions on the basis of a model representing a regular three-dimensional macromolecular network diffusing in a viscous medium. Discrete and continuous models of macromolecules are considered. The relaxation time spectrum in the system studied is broken down into two groups of times, corresponding to motions within submolecules and motions coordinated between molecular configurations. It is shown that the values obtained empirically for absorption ( lambda a/v(2)) are determined not by the macroscopic (bulk) viscosity, but by the local viscosity of the network-solvent system. An estimate was made of the local viscosity values. The model adopted here allows an interpretation of the increment in (lambda a/v(2)) accompanying structural changes in the network in response to increased temperature and prolonged exposure to large-amplitude ultrasonic irradiation.


Title Theory of ultrasonic attenuation in cylindrical and rectangular waveguides.
Author Carome EF, Witting JM.
Journal J Acoust Soc Am
Volume
Year 1961
Abstract A theoretical study is made of attenuation of ultrasound in cylindrical and rectangular waveguides. The systems treated consist of a piston source radiating into a bounded, inviscid fluid and a receiver of the same size as the source. Expressions for receiver output are derived, and acoustic loss as a function of path length is computed for various source and waveguide configurations. Boundary conditions corresponding to both perfectly rigid and perfectly free walls are considered. The waveguide approach is extended to the limiting case of radiation into an unbounded medium, and results are given for both square and circular systems. In the latter case the curve of loss versus path length agrees well with that previously obtained using more conventional diffraction theory.


Title Therapeutic abortion and ultrasound.
Author Hodge KE.
Journal Can Med Assoc J
Volume
Year 1971
Abstract Letter to the editor.


Title Therapeutic arteriogenesis by ultrasound-mediated VEGF165 plasmid gene delivery to chronically ischemic skeletal muscle.
Author Leong-Poi H, Kuliszewski MA, Lekas M, Sibbald M, Teichert-Kuliszewska K, Klibanov AL, Stewart DJ, Lindner JR.
Journal Circ Res
Volume
Year 2007
Abstract Current methods of gene delivery for therapeutic angiogenesis are invasive, requiring either intraarterial or intramuscular administration. A noninvasive method of gene delivery has been developed using ultrasound-mediated destruction of intravenously administered DNA-bearing carrier microbubbles during their microcirculatory transit. Here we show that chronic ischemia could be markedly improved by ultrasound-mediated destruction of microbubbles bearing vascular endothelial growth factor-165 (VEGF(165)) plasmid DNA. Using a model of severe chronic hindlimb ischemia in rats, we demonstrated that ultrasound mediated VEGF(165)/green fluorescent protein (GFP) plasmid delivery resulted in a significant improvement in microvascular blood flow by contrast-enhanced ultrasound, and an increased vessel density by fluorescent microangiography, with minimal changes in control groups. The improvement in tissue perfusion was attributed predominantly to increases in noncapillary blood volume or arteriogenesis, with perfusion peaking at 14 days after delivery, followed by a partial regression of neovascularization at 6 weeks. Transfection was localized predominantly to the vascular endothelium of arterioles in treated ischemic muscle. RT-PCR confirmed the presence of VEGF(165)/GFP mRNA within treated ischemic muscle, being highest at day 3 postdelivery, and subsequently decreasing, becoming almost undetectable by 6 weeks. We found a modulation of endogenous growth factor expression in VEGF-treated ischemic muscle, consistent with a biologic effect of ultrasound mediated gene delivery. The results of our study demonstrate the utility of ultrasonic destruction of plasmid-bearing microbubbles to induce therapeutic arteriogenesis in the setting of severe chronic ischemia.


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