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 Ultrasound attenuation in biological tissues using a bone transducer.
Author Ray S, Behari J.
Journal Med Biol Eng Comput
Volume
Year 1987
Abstract No abstract available.


Title Ultrasound attenuation measurement in the presence of scatterer variation for reduction of shadowing and enhancement.
Author Treece G, Prager R, Gee A.
Journal IEEE Trans UFFC
Volume
Year 2005
Abstract Pulse-echo ultrasound display relies on many assumptions that are known to be incorrect. Departure from these makes interpretation of conventional ultrasound images difficult, and three-dimensional (S-D) visualizations harder still. For instance, shadowing and enhancement are the result of an incorrect assumption that sound attenuation is a function only of depth. Attempts to reduce such artefacts by estimating attenuation locally have been frustrated by large statistical variations and the influence of scatterer type. We address the latter by examining the influence of scatterer type on two existing attenuation estimation algorithms. This analysis is novel for one of the algorithms, arid contains a correction to previously published work for the other. We then propose a novel algorithm that is less sensitive to scatterer variation. We also present a novel technique for handling large statistical variations based on combined assumptions of monotonicity and smoothness. We then assess the performance of each algorithm for correcting shadowing and enhancement in in vitro data, using a real time 3-D radio frequency (RF) ultrasound acquisition system developed for this purpose. The results show visible differences in attenuation estimates from each technique, which are supported by the theoretical analysis. The novel attenuation estimation algorithm does show less sensitivity to scatterer variation, though it results in a more noisy estimate. Nevertheless, the novel technique for reducing statistical variations is sufficient to allow some degree of correction of shadowing and enhancement in each case.


Title Ultrasound attenuation measurements of the liver in vivo using a commercial.sector scanner.
Author Garra BS, Shawker TH, Nassi M, Russell MA.
Journal Ultrason Imaging
Volume
Year 1984
Abstract Attenuation measurements of various tissue mimicking phantoms and three different groups of patients were obtained using a modified commercial sector scanner. Estimates of attenuation were made using the spectral shift method with mean frequencies at different depths of a region of interest being obtained by both zero crossing and fast Fourier transform techniques. The accuracy and precision of both techniques was compared in phantoms and it was found that the FFT technique yielded less day-to-day variation (SD=3 percent) than the zero crossing technique (5 percent). For larger regions of interest, the range of variation in both techniques was more similar. Day-to-day variation in livers of normal patients was much larger than that seen in phantoms (10 to 15 percent) suggesting that in vivo measurements may be less precise due to actual daily changes in patients' livers. Attenuation estimates of phantoms were high by approximately 0.16 dB/MHz/cm compared to values obtained by transmission techniques. The attenuation values of livers in a group of 31 normal patients ranged from 0.214 dB/cm/MHz to 0.849 dB/cm/MHz with a mean of 0.627+or-0.126 dB/cm/MHz for the zero crossing technique while the mean value using the FFT technique was 0.86+or-0.168 dB/cm/MHz. A group of 26 Gauchers disease patients also showed wide variation with a mean attenuation value of 0.768+or-0.21 dB/cm/MHz using the FFT technique. This was significantly different than that of the normal group (p<.05). Also, a group of 22 chronic B hepatitis patients was examined, having a mean attenuation value of 0.823+or-0.21 dB/cm/MHz, not significantly different from those of the normal patients. Highly significant differences were found between the three groups when the power spectrum bandwidths of signals received were compared. These differences may be due to differences in the dependence of the attenuation as a function of frequency between the groups and may represent a useful tissue characterization parameter.


Title Ultrasound attenuation measurements using a reference phantom with sound speed mismatch.
Author Nam K,Rosado-Mendez IM, Rubert NC, Madsen EL, Zagzebski JA, Hall TJ.
Journal Ultrason Imaging
Volume
Year 2011
Abstract Ni abstract available.


Title Ultrasound axicon: A device for focusing over a large depth.
Author Burckhardt CB, Hoffmann H, Grandchamp PA.
Journal J Acoust Soc Am
Volume
Year 1973
Abstract The B-scan technique, which is used in ultrasonic medical diagnosis and in materials testing, suffers from a low lateral resolution because of the large diameter of the ultrasound beam. The present paper describes a beamforming device which focuses the beam over a large depth, i.e., the well-known depth of focus problem is circumvented. An experimental device is described which gives a lateral resolution of 2 to 3 mm at a frequency of 2 MHz (wavelength = 0.75 mm in water).


Title Ultrasound backscatter and attenuation in human liver with diffuse disease.
Author Lu ZF, Zagzebski JA, Lee FT.
Journal Ultrasound Med Biol
Volume
Year 1999
Abstract Ultrasound backscatter and attenuation in the liver were measured in patients with diffuse liver disease and in 35 volunteers who had no history of liver ailments. Measurements were done using radiofrequency (RF) echo signals derived from a clinical scanner; a reference phantom was scanned to account for effects of gain, transmit-receive frequency response and transducer beam patterns on echo data. The mean backscatter coefficient at 3 MHz in livers of 7 patients with fatty infiltration was 6.8 x 10-3 cm-1sr-11 compared to a mean of 0.5 x 10-3 cm-1sr-1 in healthy patients. Mean attenuation at 3 MHz was 2.54 dB/cm in fatty livers compared to 1.66 dB/cm in healthy patients. A total of 7 patients with end-stage liver disease (cirrhosis) had attenuation values similar to those in the healthy group, and their mean liver backscatter was somewhat greater than the mean backscatter for healthy livers. Quantitating both backscatter and attenuation should be considered for detecting fatty infiltration; additional processing methods are needed to differentiate cirrhotic changes on the basis of acoustic signals.


Title Ultrasound backscatter microscope for skin imaging.
Author Turnbull DH, Starkoski BG, Harasiewicz KA, Lockwood GR, Foster FS.
Journal Proc Ultrason Symp IEEE
Volume
Year 1993
Abstract There is a growing interest in high resolution, subsurface imaging of cutaneous tissues using higher frequency ultrasound. Some of the possible applications of higher frequency skin imaging include tumour staging, boundary definition, and studies of the response of tumours to therapy, investigations of inflammatory skin conditions such as psoriasis and eczema, and basic studies of skin aging, sun damage and the effects of irritants. Investigation of these areas is quite new, and the role of ultrasound skin imaging is continuing to evolve. In this paper, a realtime ultrasound backscatter microscope (UBM) for skin imaging is described which operates in the 40-100 MHz range, providing resolution down to 30mm. This imaging system should prove useful in determining the margins of small skin lesions, and in obtaining precise, in-vivo skin thickness measurements in order to characterize nonmalignant skin disease. Example images of normal skin and malignant melanoma illustrate the imaging potential of this system.


Title Ultrasound backscatter microscope for skin imaging.
Author Trunbull DH, Starkoski BG, Harasiewicz KA, Foster FS.
Journal Univ of Toronto
Volume
Year 1995
Abstract No abstract available.


Title Ultrasound bioeffects 1991: An update.
Author Thomenius KE, Lewin PA.
Journal Ultrasound Quarterly
Volume
Year 1991
Abstract Today, ultrasonic imaging is one of the most often utilized clinical imaging modalities. Because of this, the potential of clinically induced bioeffects is of critical concern. While no evidence has been found of the harmful effects of ultrasound in humans at clinically used exposure levels, the possibility of their existence has not been ruled out. The main goal of this paper is to summarize the available knowledge on the possibility of producing bioeffects using ultrasound energy levels currently employed by commercial diagnostic equipment as well as discuss the potential impact of the proposed regulatory scheme. To achieve this goal, the paper is organized as follows. First, a brief review of relevant ultrasound parameters and physical mechanisms of interaction between ultrasound and biological tissue is given. This is followed by a summary of the range of acoustic output levels produced by the currently used clinical diagnostic machines. Next, current developments in the regulatory area are discussed. With this background, a comprehensive literature review on ultrasonically induced bioeffects including most recent developments in the field is given.


Title Ultrasound bioeffects and clinical diagnostic relevance.
Author Dunn F.
Journal Jpn J Appl Phys
Volume
Year 1997
Abstract During the approximately one-third century that diagnostic ultrasound has been employed, there have been no verified reports of adverse effects. Ultrasound, at sufficient amplitudes, can produce irreversible biological effects by thermal and nonthermal mechanisms. Thermal effects result from the absorption of ultrasound by tissues. Laboratory studies have documented the response of biological systems to temperature elevation. This has led to the conclusion that expected temperature increases of less than 2?? C can be considered innocuous. However, for an expected temperature increase greater than 2?? C, the duration of exposure time should be considered. The nonthermal mechanism of cavitation is known to produce tissue disruption during gas body collapse. Laboratory studies and safety considerations have led to a mechanical index ( MI)=p/??f. For MI less than 1, the likelihood of cavitation occurring is very low, whereas for MI greater than 1, the examination should be considered to pose a risk (though none has ever been reported). Implementation of on-screen displays of estimates of temperature elevation and cavitation likelihood provides the physician the necessary information for conducting low risk examination.


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