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 Two-dimensional noise-robust blind deconvolution of ultrasound images.
Author Taxt T, Strand J.
Journal IEEE Trans UFFC
Volume
Year 2001
Abstract This paper presents a new method for 2-D blind homomorphic deconvolution of medical B-scan ultrasound images. The method is based on noise-robust 2-D phase unwrapping and a noise-robust procedure to estimate the pulse in the complex cepstrum domain. Ordinary Wiener filtering is used in the subsequent deconvolution. The resulting images became much sharper with better defined tissue structures compared with the ordinary images. The deconvolved images had a resolution gain along the order of 3 to 7, and the signal-to-noise ratio (SNR) doubled for many of the images used in our experiments. The method gave stable results with respect to noise and grey levels through several image sequences.


Title Two-dimensional temperature estimation using diagnostic ultrasound.
Author Simon C, VanBaren P, Ebbini ES.
Journal IEEE Trans UFFC
Volume
Year 1998
Abstract A two-dimensional temperature estimation method was developed based on the detection of shifts in echo location of backscattered ultrasound from a region of tissue undergoing thermal therapy. The echo shifts are due to the combination of the local temperature dependence of speed of sound and thermal expansion in the heated region. A linear relationship between these shifts and the underlying tissue temperature rise is derived from first principles and experimentally validated. The echo shifts are estimated from the correlation of successive backscattered ultrasound frames, and the axial derivative of the accumulated echo shifts is shown to be proportional to the temperature rise. Sharp lateral gradients in the temperature distribution introduce ripple on the estimates of the echo shifts due to a thermo-acoustic lens effect. This ripple can be effectively reduced by filtering the echo shifts along the axial and lateral directions upon differentiation. However, this is achieved at the expense of spatial resolution. Experimental evaluation of the accuracy (0.5°C) and spatial resolution (2 mm) of the algorithm in tissue mimicking phantoms was conducted using a diagnostic ultrasound imaging scanner and a therapeutic ultrasound unit. The estimated temperature maps were overlaid on the gray-scale ultrasound images to illustrate the applicability of this technique for image guidance of focused ultrasound thermal therapy.


Title Two-dimensional temperature imaging using pulse-echo ultrasound.
Author Ebbini ES.
Journal Therapeutic Ultrasound
Volume
Year 2006
Abstract A review of the basic principles of 2D temperature estimation using pulse-echo ultrasound is given. Some of the limitations of this technique are addressed and new solutions are described. In particular, temperature imaging artifacts due to the thermoacoustic lens effects are described. A reconstructive imaging method employing a physics-based 2D filter and a projection method is presented. Results from phantom and tissue heating experiments employing different energy sources are shown.


Title Two-step hybrid virtual array-ray (VAR) technique for focusing through the rib cage.
Author Botros YY, Ebbini ES, Volakis JL.
Journal IEEE Trans UFFC
Volume
Year 1998
Abstract A new methodology for focusing ultrasonic beams noninvasively in the presence of the rib cage is investigated. This investigation is motivated by the need to employ high intensity focused ultrasound (HIFU) using phased array applicators for the treatment of liver tumors partially shadowed by the rib obstacles. This approach enables us to efficiently perform the ultrasound computational analysis and pattern synthesis in the interior region of the rib cage. The proposed technique consists of two main steps. First, a virtual array is introduced along the intercostal spacings between the solid ribs to generate the prespecified intensity levels at a set of controls points within the target region. The second step involves the design of the actual feed array that induces the virtual sources between the intercostal spacings. This design optimization is carried out via the pseudo-inverse technique (minimum norm least squares solution) and by enforcing a constrained preconditioned psuedo-inverse method. The proposed procedure calculates the required primary sources (feed array) while maintaining minimal power deposition over the solid obstacles.


Title Ultraschall-Neurochirurgie am Menschen. (Ultrasound-neurosurgeries in people)
Author Fry WJ.
Journal Rehabilitation
Volume
Year 1964
Abstract No abstract available.


Title Ultrasonic absorption and attenuation in mammalian tissues.
Author Goss SA, Frizzell LA, Dunn F.
Journal Ultrasound Med Biol
Volume
Year 1979
Abstract The ultrasonic absorption was determined, by the transient thermoelectric method, for brain, heart, kidney, liver, tendon, and testis from cat, mouse, pig and beef. Comparison of these absorption (x) values with published values of attenuation (A) shows: (1) that the x and A coefficients, have nearly the same frequency dependencies in the range 0.5-7 MHz, (2) that the magnitudes of x and A differ appreciably and that difference depends upon the method of measurement and tissue type, and (3) that there appears to be little species difference, at least as revealed by measurements of liver and tendon.


Title Ultrasonic absorption and dispersion at phase transition in liquid crstalline systems: N-octylamine-water.
Author Dyro JF, Edmonds PD.
Journal Mol Crystals Liquid Crystals
Volume
Year 1969
Abstract A lyotropic liquid crystalline system, the amphiphile n-octylamine and water, has been studied to investigate the dependence of velocity and absorption of ultrasound on the mechanisms of isotropic-mesomorphic phase transition in the vicinity of the critical point, C(c)= 0.854 mole fraction of water and T(c) = 35.8?C. This work is the first ultrasonic study of a two-component lyotropic system in the region of an isotropic-mesomorphic transition. Measurements of ultrasonic absorption are reported over a frequency range from 10 MHz to 130 MHz and of velocity at 10 MHz. Relaxational processes controlled by a distribution of time constants greater than 10(-8) sec (frequencies less then 30 MHz) are probable. Diffusion controlled processes may be inferred. At 10 MHz the absorption in the critical region exhibits a maximum and the velocity undergoes a discontinuity. Such behavior is similar to that previously observed in thermotropic liquid crystals, binary liquids and gas liquid systems at the critical point. Measurements were also made over the full concentration range at three temperatures (31.1?, 36.85?, and 42.1?), corresponding to (T - T(c)) of -4.75?, +1.0?, +6.25?. At 36.85?C a peak in the absorption was found at the critical concentration; at higher frequencies the maximum occurred at slightly lower concentration of water. At 31.1?c the isotherm intersects several phase boundaries and increased absorption, associated with increased viscosity, was observed in the mesomorphic phase.


Title Ultrasonic absorption and dispersion in biological media: a postulated model.
Author Sehgal CM, Greenleaf JF.
Journal J Acoust Soc Am
Volume
Year 1982
Abstract An integrated approach for the absorption of ultrasound by liquids and tissues is proposed from the solution of a one-dimensional wave equation of propagation. The proposed model explains the square and linear power dependence of absorption on frequency for liquids and tissues, respectively. The study also provides a new index, specific heat ratio (gamma), in terms of which the physical and chemical state and thus possibly the pathological state of a tissue can be defined quantitatively.


Title Ultrasonic absorption and dispersion.
Author Dunn F, O'Brien WD Jr.
Journal Book Chapter
Volume
Year 1978
Abstract No abstract available.


Title Ultrasonic absorption and dispersion.
Author Dunn F,O'Brien WD Jr.
Journal Book Chapter
Volume
Year 1978
Abstract Introduction: Complete specification of wave propogation of a medium require knowledge of inertial ,restoring and loss parameters as functions of the state,wave and media variables.For an infinitesimal ultrsonic wave propogating in an isotropic unbounded liquid-like medium,these become,respectively,the density,an elastic parameter such as the adiabatic compressibility, and the attenuation. The inertial and restoring parameters embody the more easily measured impedance and velocity functions.The attenuation parameter includes absorption of the wave energy,in the body of the medium and degraded to heat,and all other mechanisms by which energy is extracted from the wave process or redirected at media inhomogeneities. Thus knowlege of the speed of sound and loss terms as functinos of acoustic and state variables, position, tissue and state of tissue, are important dor interpretations of, for example, clinical diagnostic ultrasonic date. Biological macromolecules in solution constitutes a simpler medium but one which interrogation by ultrasound,again involving observations of the wave velocity and loss functions,can yield detils of reactions ccuring in the time range 10-3 to 10-10 sec. This chapter includes reviews of both of these kinds of media.As scattering phenomena are treated in Chapter VII, no further meniton is made here. The relatively simpler media of solutions are considered first. As it has been established that proteins are largely responsible for absoprtion in tissues, studies to elucidate the underlying mechanisms have involved solutions of this chemical species. These are each treated seperately in a comparative fashion. Tissues are then treated and the dependance of the absorption and velocity on the principal parameters frequency, temperature and wave amplitude are exhibited. Remarks are made of tissues requiring special attention, viz., bone,lung,refractive media of the eye and those with high collagen content. The attempt here has been to be timely rather than complete and in this regard the reader may wish to consult Dunn et al and Reid and Sikov for additional details.


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