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 Deep local hyperthermia by focused ultrasound.
Author Lele PP, Parker KJ, Castro EP.
Journal Int J Radiat Oncol Biol Phys
Volume
Year 1978
Abstract No abstract available.


Title Deep localized hyperthermia with ultrasound phased arrays using the pseudoinverse pattern synthesis method.
Author Ebbini ESA.
Journal Thesis(PhD): Univ of Illinois
Volume
Year 1990
Abstract One of the major limitations of hyperthermia as a cancer treatment modality is the lack of heating equipment and techniques capable of consistent therapeutic heating of deepseated tumors. This thesis introduces a new pattern synthesis method capable of precisely controlling the power deposition level at a set of control points in the treatment volume using ultrasound phased arrays. This method, called the pseudoinverse pattern synthesis method, reduces the pattern synthesis problem to one of estimating the minimum-normleast-square solution to a matrix equation of the form, Hu=p, where u is the array excitation vector, p is the desired complex pressure at the control points, and H is a matrix propagation operator from the surface of the array to the control points. A useful solution to this problem is obtained when the number of control points is less than the number of elements of the array and the matrix H is full rank. This solution, called the minimum-norm solution, allows the array to be focused at several points simultaneously. This multiple-focus approach is important when ultrasound is used as a heating agent as it reduces the spatial-peak temporal-peak intensity required to generate a specified heating pattern. Furthermore, the minimum-norm solution allows the optimization of the array excitation efficiency and the intensity gain at the control points. These quantities are very significant for achieving deep localized heating with phased arrays. In fact, optimization of the intensity gain at control points generally results in removal of high intensity interference patterns from the synthesized field. The removal of high intensity interference patterns eliminates one of the major disadvantages of multiple focusing. The pseudoinverse pattern synthesis method is introduced and discussed in detail. Simulation results are used to demonstrate its powerful capabilities as a pattern synthesis method. Its generality is demonstrated by the use of several different array structures to synthesize different multiple-focus patterns. Simulations results indicate that direct synthesis of multiple-focus patterns can provide an alternative to single-focus scanning. Finally, measured intensity profiles using a prototype cylindrical-section array agree well with theoretically predicted profiles.


Title Defects of bilayers generated by ultrasound.
Author Malghani MS, Yang J, Wu J.
Journal J Acoust Soc Am
Volume
Year 1998
Abstract No Abstract Available.


Title Defining optimal axial and lateral resolution for estimating scatterer properties from volumes using ultrasound backscatter.
Author Oelze ML, O'Brien WD Jr.
Journal J Acoust Soc Am
Volume
Year 2004
Abstract The rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. Typically, the backscattered power spectrum is calculated from a region of interest (ROI) within some larger volume. The dimensions of the ROI are defined axially by the spatial length corresponding to the time gate and laterally by the number of scan lines included in the ROI. Averaging the backscattered power spectra from several independent scan lines can reduce the presence of noise caused by electronics and by the random scatterer spacings, but also decreases the lateral resolution of the interrogation region. Furthermore, larger axial gate lengths can be used to reduce the effects of noise and improve the precision and accuracy of scatterer property estimates but also decreases the axial resolution. A trade-off exists between the size of the ROI (the number of scan lines used, the separation distance between each scan line, the axial gate length) and the accuracy and precision of scatterer property estimates. A series of simulations and measurements from physical phantoms were employed to examine these trade-offs. The simulations and phantom measurements indicated the optimal lateral and axial sizes of the ROI, where estimate accuracy and precision were better than 10% and 5%, respectively, occurred at 4 to 5 beamwidths laterally and 15 to 20 spatial pulse lengths axially.


Title Deformation and motion produced in isolated.living cells by localized ultrasonic vibration.
Author Wilson WL, Wiercinski FJ, Nyborg WL, Schnitzler RM, Sichel FJ.
Journal J Acoust Soc Am
Volume
Year 1966
Abstract Naturally-isolated living cells were subjected to ultrasonic vibration by means of the tip of a steel needle applied directly to the cell surface or inserted into a drop of a suspension of cells in sea water. The needle was machined into the tip of a stainless-steel cone, and the base of the cone was glued to one end of an electroded and polarized barium titanate hollow cylinder. This composite transducer was driven at its resonant frequency of approximately 85,000 cps. Ultrasound applied to the surfaces of egg cells of marine invertebrates produces rotation, translation, deformation, and fragmentation of the nucleoli; rotation and deformation of the nuclei; acoustic streaming of nucleoplasm and cytoplasm; and deformation of the cellular surface and fragmentation of hte cell. Cells and intracellular bodies are often attracted to the sound source as a result of acoustic-radiation pressure, and, especially for whole cells in suspension, this attractive tendency is typically superposed on a tendency of the body to take part in acoustic streaming of the surrounding medium. Some aspects of the motion can be accounted for in terms of presently available theory of nonlinear acoustics. Information on the physical properties of nucleolus, nucleoplasm, and cytoplasm is gained from use of this sonic technique.


Title Deformation models and correlation analysis in elastography.
Author Bilgen M, Insana MF.
Journal J Acoust Soc Am
Volume
Year 1996
Abstract Cross-correlation functions are derived with the purpose of determining how strain inhomogeneities affect the displacement estimates used in ultrasound-based elastography. Variations in the strain profile occur in most imaging situations and are caused by fluctuations in the stress field or elastic modulus of the sample. An analytical framework for developing signal processing strategies in elastography is described, and the limitations of correlation-based methods for measuring displacements in tissuelike media caused by static compression are emphasized. This paper includes (1) an accurate approximation for an inverse coordinate transformation that release pre- and postcompression reflectivity profiles of the media, (2) a derivation of the echo-signal cross-correlation function in media with deterministic or stochastic strain profiles; (3) mathematical and graphical descriptions of the consequences that nonuniformities in the strain profile impose upon the uncertainty of displacement estimation; and (4) a demonstration of the advantages of echo signal conditioning and ultrasonic-pulse shaping to reduce the nonstationary effects that attenuate the cross-correlation peak and reduce the signal-to-noise ration for displacement estimation.


Title Degradation of DNA by intense, noncavitating ultrasound.
Author Hawley SA, Macleod RM, Dunn F.
Journal J Acoust Soc Am
Volume
Year 1963.
Abstract Previous research leads to the conclusion that intense, noncavitating ultrasound affects tissue at the level of macromolecular structures. As an initial study of the interaction of intense sound waves and macromolecules, solutions of DNA were irradiated with noncavitating, 1-Mc/sec ultrasound at intensities in the neighborhood of 30 W/cm2. Sedimentation-velocity analysis shows that the molecular weight of the DNA is reduced. Cavitation and thermal processes can be eliminated as possible degradation mechanisms. It is suggested that relative motion between the macromolecules and the suspending medium may be the mechanism by which degradation occurs.


Title Degradation of DNA by intense, noncavitating ultrasound.
Author Hawley SA.
Journal Thesis(MS): Univ of Illinois
Volume
Year 1963
Abstract This paper describes an initial study of the interaction of high intensity, noncavitating ultrasound and macromolecules. Several species of DNA, a high molecular weight linear biological polymer which has been studied widely in recent years and has been characterized with respect to a large number of physical parameters, were prepared in solution and exposed to 1 mc ultrasound of intensities in the neighborhood of 30 w/cm squared for periods ranging from several seconds to several minutes. It was found that molecular degradation resulted. Colorimetric and molecular weight analysis of irradiated materials revealed that bond cleavage transverse to the axis of the molecule had probably resulted. The temporal dependence of the sedimentation constant exhibited two distinct phases: (1) an initial rapid decrease resulting from appreciable decrease in the molecular weight of the DNA molecules and (2) a subsequent leveling-off, implying that further reduction does not occur. The asymptotic value of the sedimentation constant, as well as the initial time rate of change, are functions of the acoustic intensity of exposure. Cavitation and associated mechanisms, as well at thermal denaturation, have been eliminated as the degradative agent. Relative motion between the macromolecules and the suspending medium is considered as the mode of interaction by which degradation occurs and is discussed briefly.


Title Delay quantization error in phased array images.
Author Magnin PA, Von Ramm OT, Thurstone FL.
Journal IEEE Trans Sonics Ultrason
Volume
Year 1981
Abstract Time quantization errors in phased systems can cause increased sidelobe amplitude, thereby limiting the dynamic range of the ultrasound system. A simulation program predicting the position and amplitude of these anomalous quantization error grating lobes has been developed to study the effects of transmitted pulse length on the amplitude of these anomalous lobes. These parallel processing techniques for decreasing these sidelobe amplitudes while smoothing the speckle pattern are investigated.


Title Deletion of the K1L gene results in a vacinnia virus that is less pathogenic due to muted innate immune responses, yet still elicits protective immunity.
Author Bravo Cruz AG, Han A, Roy EJ, Guzman AB, Miller RJ, Driskell EA, O'Brien WD Jr, Shisler JL.
Journal J Virol
Volume
Year 2017
Abstract All viruses strategically alter the antiviral immune response to their benefit. The vaccinia virus (VACV) K1 protein has multiple immunomodulatory effects in tissue culture models of infection, including NF-κB antagonism. However, the effect of K1 during animal infection is poorly understood. We determined that a K1L-less vaccinia virus (vΔK1L) was less pathogenic than wild-type VACV in intranasal and intradermal models of infection. Decreased pathogenicity was correlated with diminished virus replication in intranasally infected mice. However, in intradermally inoculated ears, vΔK1L replicated to levels nearly identical to those of VACV, implying that the decreased immune response to vΔK1L infection, not virus replication, dictated lesion size. Several lines of evidence support this theory. First, vΔK1L induced slightly less edema than vK1L, as revealed by histopathology and noninvasive quantitative ultrasound technology (QUS). Second, infiltrating immune cell populations were decreased in vΔK1L-infected ears. Third, cytokine and chemokine gene expression was decreased in vΔK1L-infected ears. While these results identified the biological basis for smaller lesions, they remained puzzling; because K1 antagonizes NF-κB in vitro, antiviral gene expression was expected to be higher during vΔK1L infection. Despite these diminished innate immune responses, vΔK1L vaccination induced a protective VACV-specific CD8+ T cell response and protected against a lethal VACV challenge. Thus, vΔK1L is the first vaccinia virus construct reported that caused a muted innate immune gene expression profile and decreased immune cell infiltration in an intradermal model of infection yet still elicited protective immunity. IMPORTANCE The vaccinia virus (VACV) K1 protein inhibits NF-κB activation among its other antagonistic functions. A virus lacking K1 (vΔK1L) was predicted to be less pathogenic because it would trigger a more robust antiviral immune response than VACV. Indeed, vΔK1L was less pathogenic in intradermally infected mouse ear pinnae. However, vΔK1L infection unexpectedly elicited dramatically reduced infiltration of innate immune cells into ears. This was likely due to decreased expression of cytokine and chemokine genes in vΔK1L-infected ears. As such, our finding contradicted observations from cell culture systems. Interestingly, vΔK1L conferred protective immunity against lethal VACV challenge. This suggests that the muted immune response triggered during vΔK1L infection remained sufficient to mount an effective protective response. Our results highlight the complexity and unpredictable nature of virus-host interactions, a relationship that must be understood to better comprehend virus pathogenesis or to manipulate viruses for use as vaccines.


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