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 Malignant and benign breast tissue classification performance using a scatterer structure preclassifier.
Author Donohue KD Huang L Georgiou G Cohen FS Piccoli CW Forsberg F.
Journal IEEE Trans UFFC
Volume
Year 2003
Abstract Benign and malignant breast tissue classification is examined for generalized-spectrum parameters computed from RF ultrasound data when a preclassification of subregions based on general scattering properties is performed. Results using a clinical database of 84 patients show statistically significant improvements (over 10% in receiver operation characteristic (ROC) areas) when only coherent scatterer subregions are used as compared to using all subregions within the region of interest.


Title Mammography instrumentation for combined x-ray and ultrasound imaging
Author Kelly-Fry E, Dines KA.
Journal Proc Ninth Int Cong Ultrason Ex Breast
Volume
Year 1995
Abstract No abstract available.


Title Mapping of regional cancerous tissue mechanical property changes using harmonic motion imaging.
Author Maleke C, Pelegri AA, Luo J, Konofagou EE.
Journal Proc ASME
Volume
Year 2007
Abstract Mechanical changes in breast tissues as a result of cancer are usually detected through palpation by the physician and/or self examination. However, physicians are unable to palpate most masses under 1 cm in diameter and microscopic diseases. The goal of our study is to introduce the application of the Harmonic Motion Imaging (HMI), an acoustic radiation force technique, for reliable sensitive tumor detection and real-time monitoring of tumor ablation. Here, we applied the HMI technique using a single-element Focused Ultrasound (FUS) transducer. Due to the highly localized and harmonic nature of the response, the motion characteristics can be directly linked to the regional tissue modulus. In this experiment, a confocal transducer, combining a 4.68 MHz therapy (FUS) and a 7.5 MHz diagnostic (pulse-echo) probe, was used. The FUS beam was further modulated by a low AM continuous wave at 25 Hz. A pulser/receiver was used to drive the pulse-echo transducer at a Pulse Repetition Frequency (PRF) of 5.4 kHz. The radio-frequency (RF) signals were acquired using a standard pulse echo technique. The intensity amplitudes of the FUS beam at the focus (Ispta) were 231 W/cm2 for tumor detection and 1086 W/cm2 for FUS ablation. An analog bandpass filter was used to remove the spectrum of the FUS beam prior to displacement estimation. The resulting axial tissue displacement (i.e., HMI displacement) was estimated using an RF-based speckle tracking technique based on 1D cross-correlation. For tumor mapping, a harmonic radiation force was applied using a 2D raster-scan technique. The 3D HMI image was obtained by combining multiple 2D planes at different depths. The 2D and 3D HMI images in ex vivo breast tissues could detect a benign tumor (2x5x5mm3) surrounded by normal tissue, and a malignant tumor (8x7x5mm3) embedded in glandular and fat tissues. For FUS therapy, temperature measurements and RF signals were acquired during thermal ablation. HMI images during FUS ablation showed lower displacements, indicating thus tissue hardening due to lesion formation at temperatures higher than 50°C. A finite-element model (FEM) simulation was also used to analyze the findings of the experimental results. In conclusion, this technique demonstrates feasibility of the HMI technique for tumor detection and characterization, as well as real-time monitoring of tissue ablation based on the associated tissue elasticity changes.


Title Mathematical modeling of the dilution curves for ultrasonographic contrast agents.
Author Sehgal CM.
Journal J Ultrasound Med
Volume
Year 1997
Abstract Most techniques using sonographic contrast agents are based on introducing the agent intravenously. The sonographic changes occur over time and follow a characteristic "skewed gaussian curve," often referred to as the indicator dilution curve. This study uses principles of linear acoustics and tracer kinetics to develop a quantitative model for the indicator dilution curve. A rapid increase in image brightness occurs after bolus injection; brightness peaks after a time related to the blood flow and stability of the contrast agent, which is followed by an asymptotic decrease in image brightness. The net image enhancement, represented by the area under the dilution curve, increases nonlinearly with the injected dose. In stable contrast agents the peak-time and mean transit time are related directly to the flow rate. This relationship changes when the microbubbles of a contrast agent collapse. In an unstable contrast agent the indicator dilution curve is attenuated and peaks earlier than expected on the basis of flow rate. The extent of shift in the mean transit time varies with the half-life of the contrast agent and follows a sigmoid relationship. In conclusion, the properties of the time-videointensity (indicator dilution) curves are significantly affected by the attenuation and stability of the contrast agents. These factors must be taken into consideration in deriving flow related information.


Title Maximum-likelihood approach to strain imaging using ultrasound.
Author Insana MF, Look LT, Bilgen M, Chaturvedi P, Zhu Y.
Journal J Acoust Soc Am
Volume
Year 2000
Abstract A maximum-likelihood (ML) strategy for strain estimation is presented as a framework for designing and evaluating bioelasticity imaging systems. Concepts from continuum mechanics, signal analysis, and acoustic scattering are combined to develop a mathematical model of the ultrasonic waveforms used to form strain images. The model includes three-dimensional (3-D) object motion described by affine transformations, Rayleigh scattering from random media, and 3-D system response functions. The likelihood function for these waveforms is derived to express the Fisher information matrix and variance bounds for displacement and strain estimation. The ML estimator is a generalized cross correlator for pre- and post-compression echo waveforms that is realized by waveform warping and filtering prior to cross correlation and peak detection. Experiments involving soft tissuelike media show the ML estimator approaches the Cramer-Rao error bound for small scaling deformations: at 5 MHz and 1.2% compression, the predicted lower bound for displacement errors is 4.4 microns and the measured standard deviation is 5.7 microns.


Title Mbps experimental acoustic through-tissue communications:MEAT-COMMS
Author Singer A, Oelze ML, Podkowa A.
Journal IEEE SPAWC
Volume
Year 2016
Abstract Methods for digital, phase-coherent acoustic communication date to at least the work of Stojanjovic, et al [20], and the added robustness afforded by improved phase tracking and compensation of Johnson, et al [21]. This work explores the use of such methods for communications through tissue for potential biomedical applications, using the tremendous bandwidth available in commercial medical ultrasound transducers. While long-range ocean acoustic experiments have been at rates of under 100kbps, typically on the order of 1-10kbps, data rates in excess of 120Mb/s have been achieved over cm-scale distances in ultrasonic testbeds [19]. This paper describes experimental transmission of digital communication signals through samples of real pork tissue and beef liver, achieving data rates of 20-30Mbps, demonstrating the possibility of real-time video-rate data transmission through tissue for inbody ultrasonic communications with implanted medical devices.


Title Mean-scatterer spacing estimates with spectral correlation.
Author Varghese T, Donohue KD.
Journal J Acoust Soc Am
Volume
Year 1994
Abstract An ultrasonic backscattered signal from material comprised of quasiperiodic scatterers exhibit redundancy over both its phase and magnitude spectra. This paper addresses the problem of estimating mean-scatterer spacing from the backscattered ultrasound signal using spectral redundancy characterized by the spectral autocorrelation (SAC) function. Mean-scatterer spacing estimates are compared for techniques that use the cepstrum and the SAC function. A-scan models consist of a collection of regular scatterers with Gamma distributed spacings embedded in diffuse scatterers with uniform distributed spacings. The model accounts for attenuation by convolving the frequency dependent scattering centers with a time-varying system response. Simulation results indicate that SAC-based estimates converge more reliably over smaller amounts of data than cepstrum-based estimates. A major reason for the performance advantage is the use of phase information by the SAC function, while the cepstrum uses a phaseless power spectral density that is directly affected by the system response and the presence of diffuse scattering (speckle). An example of estimating the mean-scatterer spacing in liver tissue also is presented.


Title Measurement and reconstruction of ultrasonic parameters for diagnostic imaging.
Author Dines KA, Kak AC.
Journal Rep Purdue Univ Sch Elect Eng
Volume
Year 1976
Abstract Techniques in linear system analysis, digital signal processing, and picture reconstruction are investigated and applied to diagnostic ultrasound imaging. These investigations include system modeling and attenuation measurement for tissue characterization, digital reconstruction of spatial distributions of ultrasound attenuation and velocity in tissue, and reconstruction using a fan-beam scanning geometry. Using a linear system model we develop and compare eight methods for characterizing the attenuation properties of tissue. The approach used here leads to some new results concerning practical attenuation measurements. It is shown how the attenuation can be measured from the impulse response, transfer function, and directly from the incident and received signals. The feasibility of using the time domain impulse response for attenuation estimation is demonstrated by computer simulation studies comparing results obtained using inverse filtering, Wiener filtering, and constrained deconvolution. Attenuation measures based on the transfer function are developed with a view toward their applicability to the reconstruction problem. Many of these techniques do not require a priori knowledge of transmission coefficients. It is shown how the commonly used methods for estimating the attenuation coefficient directly from the incident and received signal energies and/or peak values can be modified to permit the use of broadband inputs. Computerized tomographic imaging using ultrasound is shown to be feasible when either attenuation or time-of-flight data is used. Contrary to some previous reports, our experimental results indicate that one can obtain reasonable attenuation tomograms in the presence of the refractive effects that exist in typical soft tissues. We present a comparison of reconstructed tomograms obtained using six different attenuation measures and the time-of-flight method. These comparisons are based on a common set of recorded ultrasonic signals obtained by scanning an excised, formalin in-fixed dog heart. As a step toward practical tomographic imaging system using ultrasound, we propose a rapid scanning technique that would eliminate mechanical motion of the source and receiver. This scanning method yields fanbeam projection data requiring special reconstruction techniques. A fanbeam reconstruction algorithm is developed, implemented and tested on computer simulated data.


Title Measurement and sensitivity characteristics of transient, focused ultrasound for tissue perfusion measurements.
Author Newman WH, Lele PP.
Journal Proc Annu Winter Meet ASME
Volume
Year 1986
Abstract A measurement technique based on the use of transient, focused ultrasonic heating offers the potential for minimally invasive measurements of tissue thermal properties, including specifically tissue perfusion. Two experimental procedures are considered: the temperature decay in a perfused medium following a thermal pulse generated by a burst of focused ultrasound, and the temperature field generated by a series of repeated thermal pulses. A sensitivity analysis of the theoretical thermal model 1) demonstrates the superior measurement sensitivity of the ultrasonic technique as compared to other probe techniques, and 2) specifies the instrumentation requirements necessary to achieve the desired measurement accuracy. Simulated data are generated to examine experimental sources of departure from the simple thermal model which will result in measurement errors: multi-dimensional tissue conduction, thermocouple conduction, and signal noise; as well as factors unique to this ultrasonic method: shape of the heating region and nonlinear ultrasonic effects. These simulations are compared with experimental results to illustrate the constraints placed on the experimental procedure and experimentally controllable parameters for the effect of perfusion to be both perceptible and measurable.


Title Measurement and simulation of the scattering of ultrasound by penetrable cylinders.
Author Robinson BS, Greenleaf JF.
Journal Acoust Imaging
Volume
Year 1984
Abstract No abstract available.


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