Bioacoustics Research Lab
University of Illinois at Urbana-Champaign | Department of Electrical and Computer Engineering | Department of Bioengineering
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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 A therapeutic ultrasound system incorporating real-time ultrasonic scanning.
Author Lizzi FL, Coleman DJ, Driller J, Silverman R, Lucas B, Rosado A.
Journal Proc Ultrason Symp IEEE
Volume
Year 1986
Abstract A system has been developed combining a real-time B-scan unit with a high-intensity, focused, therapeutic ultrasound system. This system permits precise aiming of focused therapy beams; it also provides viewing and data collection of diagnostic information concurrently with therapeutic applications. The device consists of a standard rapid-scan diagnostic probe mounted on our plastic scaled overlay of the therapeutic beam profile is placed over the diagnostic B-scan system's monitor. Simple targets have been developed to assure proper alignment of the components. The system has been used to apply intense ultrasound to tissue and to monitor the insonified tissue during and immediately after insonification. Dynamic responses within tissues and test targets have been documented. The system is being applied clinically for hyperthermia induction in ocular tumors. It is also being used in animal experiments involving ultrasonic tumor ablation, vitreous-membrane disruption and vitreous-hemorrhage dispersion.


Title A three dimensional model for generating the texture in B-scan ultrasound images.
Author Goodsitt MM, MAdsen EL, Zagzebski JA.
Journal Ultrason Imaging
Volume
Year 1983
Abstract A three-dimensional model for production of gray scale texture in ultrasound B-mode images is described. The model computes time-dependent echo signals resulting from scattering of acoustic pulses by particles randomly distributed in an attenuating medium and transforms these signals into a gray scale image. Specific transducer and pulser-receiver characteristics are accounted for, as well as the three-dimensional nature of the problem, without loss of computational efficiency. The model generates texture that closely corresponds to that found experimentally in ultrasound images of tissue-mimicking phantoms. The dependence of the texture upon the depth of the region that was scanned and on the characteristics of the transducer-receiver system were clearly demonstrated. Good agreement between theory and experiment was found for the texture in phantoms containing simulated spherical low-scatter tumors.


Title A three dimensional model for generating the texture in B-scan ultrasound images.
Author Goodsitt MM.
Journal Thesis(PhD): Univ of Wisconsin-Madison
Volume
Year 1982
Abstract The texture that an organ exhibits in an ultrasound B-scan image can often be an important component in the evaluation of the disease state of the organ. This texture is dependent upon properties of the organ as well as properties of the ultrasound imaging system. T o gain insight into the relationships between these properties and the texture in the images, mathematical models for generating ultrasound B-scan texture have been proposed. For reasons of simplicity and computational efficiency, these models have been limited to characterizing the 3-D imaging situation by 2-D simulations. In this thesis, a realistic and computationally efficient 3-D model for generating the texture in B-scan images is proposed and tested. Aside from its 3-D nature, this model also differs from the other models in that it utilizes a highly realistic ultrasound beam theory, and it incorporates instrumental factors such as the frequency content of the pressure pulse emitted by the transducer, the physical characteristics of the transducer, and the frequency response of the transducer ? receiver system. The inclusion of such factors permits a direct comparison between theory and experiment. Such a comparison is carried out, and several new texture measures are employed in the process. The model is found to perform most adequately in predicting the texture in images of a phantom containing a large concentration of Rayleigh scatterers. The influences of pulser-receiver characteristics and the depth of the imaged region on the imaged texture pattern are observed both experimentally and theoretically. Furthermore, a study is performed in which the model is applied to the situation of imaging a low scatter spherical inhomogeneity that is embedded in a relatively high scatter medium. The model is found to accurately predict the appearance of the inhomogeneity in images which are created when the scanning plane of the transducer passes through the center of the object, and when the scanning plane is displaced from the center of the object. The work describe din this thesis represents a foundation upon which future investigations and models can be built.


Title A transient heating technique for the measurement of thermal.properties of perfused biological tissue.
Author Newman WH, Lele PP.
Journal J Biomech Eng
Volume
Year 1985
Abstract Knowledge of tissue thermal transport properties is imperative for any therapeutic medical tool which employs the localized.application of heat to perfused biological tissue. In this study, several techniques are proposed to measure local tissue thermal.diffusion by heating with a focused ultrasound field. Transient as well as near steady-state heat inputs are discussed and.examined for their suitability as a measurement technique for either tissue thermal diffusivity or perfusion rate. It is shown.that steady-state methods are better suited for the measurement of perfusion; however the uncertainty in the perfusion.measurement is directly related to knowledge of the tissue's intrinsic thermal diffusivity. Results are presented for a transient.thermal pulse technique for the measurement of the thermal diffusivity of perfused and nonperfused tissues, in vitro and in.vivo. Measurements conducted in plexiglas, animal muscle, kidney and brain concur with tabulated values and show a scatter.from 5-15 percent from the mean; measurements made in perfused muscle and brain compare well with the nonperfused.values. An estimate of the error introduced by the effect of perfusion shows that except for highly perfused kidney tissue the.effect of perfusion is less than the experimental scatter. This validation of the tissue heat transfer model will allow its eventual.extension to the simultaneous measurement of local tissue thermal diffusivity and perfusion.


Title A two-dimensional amplitude-steered array for real-time volumetric acoustic imaging.
Author Frazier CAH.
Journal Thesis(PhD): Univ of Illinois
Volume
Year 2000
Abstract Real-time volumetric ultrasound imaging is difficult due to problems with array construction and due to the slow speed of data collection. In 1976, a linear amplitude-steered array can be extended to a two-dimensional array operating over a broad range of frequencies to be used for a real-time volumetric imaging system. First, the properties of the linear amplitude-steered array are studied, showing that there is a tradeoff between axial and lateral resolution, unique to this array that depends on the length of the array. Second, various time-frequency distributions are surveyed for use in creating an image from a single received signal. Next, the concepts of imaging with a linear array are extended to imaging a volume with a two-dimensional amplitude-steered array. The array design is presented, and it is shown that the targets can be localized by using the frequency separation of the amplitude-steered array in the vertical direction and conventional phased array beamsteering in the horizontal direction. Several methods for displaying the data are presented, with projection images offering computational savings. Nonlinear propagation is also discussed, demonstrating that although frequency of the received signal is equated with position, nonlinear generation of harmonics does not cause the appearance of false targets in the images. Experimental data are compared with simulations to validate the simulations of the array operation.


Title A unified model for the speed of sound in cranial bone based on genetic algorithm optimization.
Author Connor CW, Clement GT, Hynynen K.
Journal Phys Med Biol
Volume
Year 2002
Abstract The density and structure of bone is highly heterogeneous, causing wide variations in the reported speed of sound for ultrasound propagation. Current research on the propagation of high intensity focused ultrasound through an intact human skull for non-invasive therapeutic action on brain tissue requires a detailed model for the acoustic velocity in cranial bone. Such models have been difficult to derive empirically due to the aforementioned heterogeneity of bone itself. We propose a single unified model for the speed of sound in cranial bone based upon the apparent density of bone by CT scan. This model is based upon the coupling of empirical measurement, theoretical acoustic simulation and genetic algorithm optimization. The phase distortion caused by the presence of skull in an acoustic path is empirically measured. The ability of a theoretical acoustic simulation coupled with a particular speed-of-sound model to predict this phase distortion is compared against the empirical data, thus providing the fitness function needed to perform genetic algorithm optimization. By performing genetic algorithm optimization over an initial population of candidate speed-of-sound models, an ultimate single unified model for the speed of sound in both the cortical and trabecular regions of cranial bone is produced. The final model produced by genetic algorithm optimization has a nonlinear dependency of speed of sound upon local bone density. This model is shown by statistical significance to be a suitable model of the speed of sound in bone. Furthermore, using a skull that was not part of the optimization process, this model is also tested against a published homogeneous speed-of-sound model and shown to return an improved prediction of transcranial ultrasound propagation.


Title A wavelet thresholding method to reduce ultrasound artifacts.
Author Tay PC, Acton ST, Hossack JA.
Journal Comput Med Imaging Graph
Volume
Year 2011
Abstract Artifacts due to enhancement, reverberation, and multi-path reflection are commonly encountered in medical ultrasound imaging. These artifacts can adversely affect an automated image quantification algorithm or interfere with a physician's assessment of a radiological image. This paper proposes a soft wavelet thresholding method to replace regions adversely affected by these artifacts with the texture due to the underlying tissue(s), which were originally obscured. Our proposed method soft thresholds the wavelet coefficients of affected regions to estimate the reflectivity values caused by these artifacts. By subtracting the estimated reflectivity values of the artifacts from the original reflectivity values, estimates of artifact reduced reflectivity values are attained. The improvements of our proposed method are substantiated by an evaluation of Field II simulated, in vivo mouse and human heart B mode images.


Title A Wold decompositionā€based autonomous system for detecting breast lesions in ultrasound images of the breast.
Author Georgiou G, Cohen FS.
Journal J. Acoust. Soc. Am
Volume
Year 1998
Abstract No Abstract Available.


Title Abdominal and obstetric applications of a dynamically focused phased array real time ultrasound system.
Author Morgan C, Trought WS, Von Ramm OT, Thurstone FL.
Journal Clin Radiol
Volume
Year 1980
Abstract Abdominal and obstetric applications of a dynamically focused phased array real time ultrasonic system are described. This work was performed utilising both the Thaumascan (two-dimensional, high resolution, actual time, ultrasound, multi-element array scanner) and the first commercial unit based on this system, the Grumman RT-400. Examples of normal and pathological anatomy are presented from over 300 examinations performed to date, including a series of 28 abdominal aortic aneurysms studies with the RT-400. Following electronic alterations in the Thaumascan with resultant improvement in the grey scale, prospective analyses in 86 obstetric and 23 abdominal examinations were undertaken. These studies indicate that fetal, intra-uterine, obstetric and abdominal examinations is illustrated. The principles of dynamically focused phased arrays are described, and the merits and limitations of these systems are discussed.


Title Abdominal ultrasound. (Article is in Japanese.)
Author Fukuda M, Urushizaki I.
Journal Diagn Ther
Volume
Year 1978
Abstract No abstract available.


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