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 A novel power spectrum calculation method using phase-compensation and weighted averaging for the estimation of ultrasound attenuation.
Author Heo SW, Kim H.
Journal Ultrasonics
Volume
Year 2009
Abstract An estimation of ultrasound attenuation in soft tissues is critical in the quantitative ultrasound analysis since it is not only related to the estimations of other ultrasound parameters, such as speed of sound, integrated scatterers, or scatterer size, but also provides pathological information of the scanned tissue. However, estimation performances of ultrasound attenuation are intimately tied to the accurate extraction of spectral information from the backscattered radiofrequency (RF) signals. In this paper, we propose two novel techniques for calculating a block power spectrum from the backscattered ultrasound signals. These are based on the phase-compensation of each RF segment using the normalized cross-correlation to minimize estimation errors due to phase variations, and the weighted averaging technique to maximize the signal-to-noise ratio (SNR). The simulation results with uniform numerical phantoms demonstrate that the proposed method estimates local attenuation coefficients within 1.57% of the actual values while the conventional methods estimate those within 2.96%. The proposed method is especially effective when we deal with the signal reflected from the deeper depth where the SNR level is lower or when the gated window contains a small number of signal samples. Experimental results, performed at 5MHz, were obtained with a one-dimensional 128 elements array, using the tissue-mimicking phantoms also show that the proposed method provides better estimation results (within 3.04% of the actual value) with smaller estimation variances compared to the conventional methods (within 5.93%) for all cases considered.


Title A novel ultrasonic technique for differentiating cysts from solid lesions: Preliminary results in the breast.
Author Nightingale KR, Kornguth PJ, Walker WF, McDermott BA, Trahey GE.
Journal Ultrasound Med Biol
Volume
Year 1995
Abstract The feasibility of a new ultrasonic technique to distinguish cysts from solid lesions is explored. High intensity pulses are used to induce acoustic streaming in cyst fluid, and this motion is detected using Doppler techniques. Acoustic streaming cannot be generated in solid lesions, therefore, its detection would indicate a cyst. In six of seven breast cysts motion was clearly generated and detected in vivo. Ultrasonic pulses with intensities up to 4.4 W cm(^-2) (I(spta) in water) were focused on the cysts for 10 s. Lesion diameters ranged from 0.6 to 2.5 cm; induced flow velocities were less than 4.0 cm s(^-1).


Title A novel ultrasound technique to study the biomechanics of the human esophagus in vivo.
Author Takeda T, Kassab G, Liu J, Puckett JL, Mittal RR, Mittal RK.
Journal Am J Physiol Gastrointest Liver Physiol
Volume
Year 2002
Abstract The objectives of this study were to validate a novel ultrasound technique and to use it to study the circumferential stress-strain properties of the human esophagus in vivo. A manometric catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasonography probe was used to record esophageal pressure and images. Validation studies were performed in vitro followed by in vivo studies in healthy human subjects. Esophageal distensions were performed with either an isovolumic (5-20 ml of water) or with an isobaric (10-60 mmHg) technique. Sustained distension was also performed for 3 min in each subject. The circumferential wall stress and strain were calculated. In vitro studies indicate that the ultrasound technique can make measurements of the esophageal wall with an accuracy of 0.01 mm. The in vivo studies provide the necessary data to compute the Kirchhoff's stress, Green's strain, and Young's elastic modulus during esophageal distensions. The stress-strain relationship revealed a linear shape, the slope of which corresponds to the Young's modulus. During sustained distensions, we found dynamic changes of stress and strain during the period of distension. We describe and validate a novel ultrasound technique that allows measurement of biomechanical properties of the esophagus in vivo in humans.


Title A parametric study of the concentric-ring transducer design for MRI guided ultrasound surgery.
Author Fjield T, Fan X, Hynynen K.
Journal J Acoust Soc Am
Volume
Year 1996
Abstract Noninvasive surgery using high-powered, focused ultrasound transducers in conjunction with magnetic resonance imaging has been shown to be feasible in previous studies. For clinical treatments, the geometry of standard MRI equipment limits the space available for ultrasound surgical equipment. This space requirement can be reduced in one dimension by using phased arrays to control the focal depth, thus eliminating the space required for the motion of a fixed focus transducer. Because of its symmetry, an annular array is ideal for changing the focal depth. Previous works have simulated, built, and characterized various concentric-ring transducers; however, no study has thoroughly examined the potential and limitations of the concentric-ring design for MRI guided ultrasound surgery. The present work is a systematic examination of the capabilities of the concentric-ring array, using numerical simulations to predict the power field, temperature distribution, and accumulated thermal dose. The results presented here illustrate the effects of ring size, center-to-center spacing configurations, number of rings, and radius of curvature on transducer performance. A 10-cm radius of curvature transducer with 14 evenly spaced rings has been built and characterized in order to verify the accuracy of the numerical simulations. The pressure-squared fields produced by this transducer are in excellent agreement with the simulated fields. ?1996 Acoustical Society of America.


Title A particulate contrast agent with potential for ultrasound imaging of liver.
Author Parker KJ, Tuthill TA, Lerner RM, Violante MR.
Journal Ultrasound Med Biol
Volume
Year 1987
Abstract Ultrasonic backscatter and attenuation coefficients of a medium can be increased by the addition of solid, micron sized inhomogeneities. A potentially useful agent for ultrasonic contrast of liver images has been identified. Iodipamide ethyl ester (IDE) particles can be produced in the form of dense, relatively incompressible solids with high impedance mismatch to water. The chemical, biomechanical, and pharmacological properties of the small, uniform diameter IDE particles permit safe intravenous injection followed by rapid accumulation by reticuloendothelial (RE) cells of the liver and spleen, and later elimination from these organs. Since the particles are phagocytized by RE cells, present in normal liver but not in tumors and many lesions, the selective enhancement of ultrasonic backscatter should improve detectability of lesions which are hypo- or iso-echoic compared to surrounding tissue. The mechanisms of particle-ultrasound interaction may be described by relative motion attenuation, and scattering from a cloud of dense, incompressible spheres for the case of IDE particles in agar. Thus, values of attenuation and.backscatter can be controlled by choice of ultrasound frequency and particle concentration and size. When the particles are accumulated in rat livers, additional mechanisms induce attenuation and backscatter in excess of that predicted by IDE in agar. This preliminary work demonstrates that solid, biocompatible particles may be useful as an ultrasonic contrast agent.


Title A perfused tissue phantom for ultrasound hyperthermia.
Author Benkeser PJ, Frizzell LA, Holmes KR, Goss SA.
Journal IEEE Trans Biomed Eng
Volume
Year 1990
Abstract A perfused tissue phantom, developed as a tool for analyzing the performance of ultrasound hyperthermia applicators, was investigated. The phantom, consisting of a fixed porcine kidney with thermocouples placed throughout the tissue, was perfused with degassed water by a variable flow rate pump. The phantom was insonated by an unfocused multielement ultrasound applicator and the temperatures in the phantom were recorded. The results indicate that for testing protocols where tissue phantoms are needed, the fixed kidney preparation offers an opportunity to use a more realistic phantom than has previously been available to assess the heating performance of ultrasound hyperthermia applicators.


Title A phase aberration correction method for ultrasound imaging.
Author Karaman M, Atalar A, Koymen H, O'donnell M.
Journal IEEE Trans UFFC
Volume
Year 1993
Abstract A computationally efficient method for phase aberration correction in ultrasound imaging is presented. The method is based on time delay estimation via minimization of the sum of absolute differences between radio frequency samples of adjacent array elements. Effects of averaging estimated aberration patterns over scan angle and truncation to a single bit wordlength are examined. Phase distortions due to near-field inhomogeneities are simulated using silicone rubber aberrators. Performance of the method is tested using experimental data. Simulation studies addressing different factors affecting efficiency of the method, such as the number of iterations, window length, and the number of scan angles used for averaging, are presented. Images of a standard resolution phantom are reconstructed and used for qualitative testing.


Title A phase compensation technique for B-mode echoencephalography.
Author Phillips DJ, Smith SW, von Ramm OT, Thurstone FL.
Journal Proc First Ultrasound Med Conf - Seattle
Volume
Year 1974
Abstract The present study uses an electronically steered and focused multi-element transducer array and a phase compensation technique in an attempt to minimize acoustic aberrations caused by skull thickness variations. Implementation of a multi-element array is an intriguing possibility in that the transducer aperture size is maintained while decreasing skull thickness variations over an individual element.


Title A piezocomposite shock wave generator with electronic focusing capability: application for producing cavitation-induced lesions in rabbit liver.
Author Tavakkoli J Birer A Arefiev A Prat F Chapelon J Inserm DC.
Journal Ultrasound Med Biol
Volume
Year 1997
Abstract In this work, a piezocomposite shock wave generator with electronic focusing capability is presented. The system is composed of a bidimensional array and its electronic hardware. The array is composed of 274 independent piezocomposite transducers arranged in a spherical shell of 280 mm in diameter and focused at 190 mm from its surface. The electronic hardware includes 274 x 6.6 kV distinct impulse generators. For the purpose of performing the electronic steering of shock waves, the delay time of each channel can be adjusted from 100 ns to 100 microseconds in steps of 100 ns. In order to enhance the effect of cavitation at the focus for the purpose of tissue destruction, the pressure-time waveform starts with a half cycle of negative pressure with a peak amplitude of about -150 x 10(5) Pa, followed by a very steep shock front with a positive peak pressure > 1000 x 10(5) Pa and a rise time of about 10 ns. Using this generator, the cavitation-induced lesions in rabbit liver were studied. To obtain a predefined lesion volume, two methods of scanning were used: mechanical and electronic. Comparison of the lesions obtained by these two methods shows that they have identical macroscopic and histological characteristics, which justify the feasibility of electronic beam steering of shock waves in tissue destruction applications.


Title A pilot comparative study of quantitative ultrasound, conventional ultrasound, and MRI for predicting histology-determined steatosis grade in adult nonalcoholic fatty liver disease
Author Paige JS, Bernstein GS, Heba E, Costa EAC, Fereirra M, Wolfson T, Gamst AC, Valasek MA, Lin GY, Han A, Erdman J W Jr, O'Brien W D Jr, Andre MP, Loomba R, Sirlin CB
Journal Am J Roentgenol
Volume
Year 2017
Abstract OBJECTIVE. The purpose of this study is to explore the diagnostic performance of two investigational quantitative ultrasound (QUS) parameters, attenuation coefficient and backscatter coefficient, in comparison with conventional ultrasound (CUS) and MRI-estimated proton density fat fraction (PDFF) for predicting histology-confirmed steatosis grade in adults with nonalcoholic fatty liver disease (NAFLD). SUBJECTS AND METHODS. In this prospectively designed pilot study, 61 adults with histology-confirmed NAFLD were enrolled from September 2012 to February 2014. Subjects underwent QUS, CUS, and MRI examinations within 100 days of clinical-care liver biopsy. QUS parameters (attenuation coefficient and backscatter coefficient) were estimated using a reference phantom technique by two analysts independently. Three-point ordinal CUS scores intended to predict steatosis grade (1, 2, or 3) were generated independently by two radiologists on the basis of QUS features. PDFF was estimated using an advanced chemical shift–based MRI technique. Using histologic examination as the reference standard, ROC analysis was performed. Optimal attenuation coefficient, backscatter coefficient, and PDFF cutoff thresholds were identified, and the accuracy of attenuation coefficient, backscatter co-efficient, PDFF, and CUS to predict steatosis grade was determined. Interobserver agreement for attenuation coefficient, backscatter coefficient, and CUS was analyzed. RESULTS. CUS had 51.7% grading accuracy. The raw and cross-validated steatosis grad- ing accuracies were 61.7% and 55.0%, respectively, for attenuation coefficient, 68.3% and 68.3% for backscatter coefficient, and 76.7% and 71.3% for MRI-estimated PDFF. Interobserver agreements were 53.3% for CUS (κ = 0.61), 90.0% for attenuation coefficient (κ = 0.87), and 71.7% for backscatter coefficient (κ = 0.82) (p < 0.0001 for all). CONCLUSION. Preliminary observations suggest that QUS parameters may be more accurate and provide higher interobserver agreement than CUS for predicting hepatic steatosis grade in patients with NAFLD.


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