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:

Michael L. Oelze publications:

Aiguo Han publications:

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Title Oscillations of polymeric microbubbles: effect of the encapsulating shell.
Author Hoff L, Sontum PC, Hovem JM.
Journal J Acoust Soc Am
Volume
Year 2000
Abstract A model for the oscillation of gas bubbles encapsulated in a thin shell has been developed. The model depends on viscous and elastic properties of the shell, described by thickness, shear modulus, and shear viscosity. This theory was used to describe an experimental ultrasound contrast agent from Nycomed, composed of air bubbles encapsulated in a polymer shell. Theoretical calculations were compared with measurements of acoustic attenuation at amplitudes where bubble oscillations are linear. A good fit between measured and calculated results was obtained. The results were used to estimate the viscoelastic properties of the shell material. The shell shear modulus was estimated to between 10.6 and 12.9 MPa, the shell viscosity was estimated to between 0.39 and 0.49 Pas. The shell thickness was 5% of the particle radius. These results imply that the particles are around 20 times more rigid than free air bubbles, and that the oscillations are heavily damped, corresponding to Q-values around 1. We conclude that the shell strongly alters the acoustic behavior of the bubbles: The stiffness and viscosity of the particles are mainly determined by the encapsulating shell, not by the air inside.


Title Output levels and bioeffects indices from diagnostic ultrasound exposure data reported to the FDA.
Author Patton CA, Harris GR, Phillips RA.
Journal IEEE Trans UFFC
Volume
Year 1994
Abstract As part of the Section 510(k) requirements of the 1976 Medical Device Amendments to the Federal Food, Drug, and Cosmetic Act, manufacturers of diagnostic ultrasound devices submit acoustic output data to the U.S. Food and Drug Administration. Because this information is pertinent to the assessment of any potential bioeffects due to ultrasound exposure, we have summarized the measurement data processed during 1990 and 1991. Exposure data were summarized for real-time B-mode and M-mode, general pulsed Doppler, peripheral vascular (PV) pulsed Doppler, and color flow Doppler. Exposure quantities included peak rarefactional and compressional pressures, spatial-peak pulse-average and spatial-peak temporal-average intensities (both water and derated values), and power. Also, where data permitted, mechanical and thermal indices were calculated. Ranges, means, medians, and standard deviations were categorized for the exposure quantities and indices. In general the temporal-average values (including indices) were higher in Doppler modes than in B/M imaging modes. Differences among the temporal-peak exposure quantities and indices were less distinct, although values tended to be higher in the PV and color flow Doppler categories. These data, along with comparable results collected by others, provide a means to relate the output of current devices to levels of exposure relevant to ultrasound-induced biological effects.


Title Overdetermined least-squares aberration estimates using common-midpoint signals.
Author Haun MA, Jones DL, O'Brien WD Jr.
Journal IEEE Trans Med Imaging
Volume
Year 2004
Abstract As medical ultrasound imaging moves to larger apertures and higher frequencies, tissue sound-speed variations continue to limit resolution. In geophysical imaging, a standard approach for estimating near-surface aberrating delays is to analyze the time shifts between common-midpoint signals. This requires complete data-echoes from every source/receiver pair in the array. Unfocused common-midpoint signals remain highly correlated in the presence of delay aberrations; there is also tremendous redundancy in the data. In medical ultrasound, this technique has been impaired by the wide-angle, random-scattering nature of tissue. This has made it difficult to estimate azimuth-dependent aberration profiles or to harness the full redundancy in the complete data. Prefiltering the data with two-dimensional fan filters mitigates these problems, permitting highly overdetermined, least-squares solutions for the aberration profiles at many steering angles. In experiments with a tissue-mimicking phantom target and silicone rubber aberrators at nonzero stand-off distances from a one-dimensional phased array, this overdetermined, fan-filtering algorithm significantly outperformed other phase-screen algorithms based on nearest-neighbor cross-correlation, speckle brightness maximization, and common-midpoint signal analysis. Our results imply that there is still progress to be made in imaging with single-valued focusing operators. It also appears that the signal-to-noise penalty for using complete data sets is partially compensated by the overdetermined nature of the problem.


Title Overview of tissue characterization.
Author Aller JC.
Journal Proc Ultrason Symp IEEE
Volume
Year 1978
Abstract The overall objective of ultrasound tissue characteristic research is to study systematically the interaction of ultrasound energy with tissue so that rational consideration can be given to substitution of non-invasive tests for a part or all of invasive tests. The objective extends to offering an alternative modality to use of X-rays which are presently the most widely used non-invasive test but known to have a potential cumulative risk.


Title Pain threshold measurements after therapeutic application of ultrasound, microwaves and infrared.
Author Lehmann JF, Brunner GD, Stow RW.
Journal Arch Phys Med Rehabil
Volume
Year 1958
Abstract Pain threshold measurements have been made with the Wolff and Hardy method after application of ultrasound, microwaves and infrared to volunteers. It was found that the pain threshold was increased when these modalities were applied to the peripheral nerve trunk and the pain threshold measured in the area of the nerve distribution. The pain threshold was also elevated when these modalities were applied directly to the same area where the pain threshold was determined afterwards. These results could be obtained only if comparatively high doses were applied.


Title Parameter mapping for the detection of disturbed blood flow.
Author Ferrara KW, Ostromogilsky M, Rosenberg, Sokil-Melgar J.
Journal Ultrasound Med Biol
Volume
Year 1995
Abstract Particularly in color flow mapping, the detection of minor stenoses is a significant outstanding challenge. With the goal of spatially mapping changes in velocity and shear rate to locate the source of the flow disturbance, two indicators of the magnitude of the signal correlation are presented and evaluated for known experimental flow conditions. A normalized parameter is presented, which is proportional to the magnitude of the signal correlation evaluated over a set of received pulses. Its performance is compared to that of a single-lag correlation measure for the development of spatial maps that indicate shear rate and velocity.


Title Parametric (integrated backscatter and attenuation) images constructed using backscattered radio frequency signals (25-56 MHz) from human aortae in vitro.
Author Bridal SL, Fornes P, Bruneval P, Berger G.
Journal Ultrasound Med Biol
Volume
Year 1997
Abstract Quantitative ultrasonic tissue characterization using backscattered high-frequency intravascular ultrasound could provide a basis for the objective identification of lesions in vivo. Representation of local measurements of quantitative ultrasonic parameters in a conventional image format should facilitate their interpretation and thus increase their clinical utility. Toward this goal, the apparent integrated backscatter, the slope of attenuation (25-56 MHz) and the.value of the attenuation on the linear fit at 37.5 MHz were measured using the backscattered radio frequency signals from in vitro human aortae. Local estimations of these ultrasonic parameters from both normal and atherosclerotic aortic segments were displayed in a B-scan format. The morphological features of these parametric images corresponded well to features of histological images of the same regions. The attenuation from 25-56 MHz of seven segments of the medial layer (both with and without overlying atheroma) were measured using the multinarrow-band.backscatter method. The average attenuation in the media at 24 ?C +/- 3 ?C was 45 +/- 16 dB/cm at 25 MHz and 102 +/- 13 dB/cm at 50 MHz. This work represents progress toward the development of quantitative imaging methods for intravascular applications.


Title Parametric analysis of ultrasound backscatter signals for monitoring cancer cell structural changes during cancer treatment.
Author Nallapareddy H, Krishnan S, Kolios MC.
Journal Can Acoust
Volume
Year 2007
Abstract High frequency ultrasound backscattered signals (20 - 60 MHz) from normal and apoptotic cell pellets differ in their backscatter intensity, and analyzing these signals could assist in the non-invasive monitoring of cancer therapy. In this work, the reflection coefficients of the lattice prediction error filter are used as feature set for parametric analysis and signal classification. The ultrasound (US) backscattered signal databases consisted of combinations of treated (apoptotic) and untreated (normal) cells mixed in different proportions. A 40 MHz commercial ultrasound imaging system was used. A classification accuracy of 97-100% for normal and apoptotic signals were obtained with a model order 15. The positive results ascertain that the reflection coefficient is a potential tool for analyzing biomedical signals such as US backscattered signals.


Title Parametric imaging of rat mammary tumors in vivo for the purposes of tissue characterization.
Author Oelze ML, Zachary JF, O'Brien WD Jr.
Journal J Ultrasound Med
Volume
Year 2002
Abstract Objective. To estimate the average scatterer properties from ultrasonic backscatter in tissues for evaluating differences between neoplastic and healthy tissues. Methods. Parametric images of 8 retired breeder rats in which spontaneous mammary tumors had developed were created by superimposing color-coded pixels related to the estimated average scatterer properties on conventional gray scale B-mode images. Results. The images showed a distinct difference between the tumors and surrounding healthy tissues. Analysis of the average scatterer diameters and acoustic concentrations showed a statistically significant difference (P < .05) between estimates inside and outside the tumors for most of the cases. Scatterer sizes inside the tumors were on average 30% larger than scatterer sizes in surrounding normal tissues. A feature analysis plot showed that there was a distinct difference between results obtained inside and outside the tumors. Conclusions. Parametric imaging that uses estimates of scatterer properties in tissues may lead to detection and characterization (diagnosis) of diseased tissues on conventional sonographic scanning systems.


Title Parametric imaging of solid tumors using average scatterer size and acoustic concentration.
Author Oelze ML, Zachary J, O'Brien WD Jr.
Journal Proc World Congr Ultrason
Volume
Year 2003
Abstract Two kinds of solid tumors were acquired and scanned in vivo ultrasonically. The fibroadenoma was acquired from rats that had spontaneously developed mammary tumors. The carcinoma was acquired by culturing a 4T1-MMT carcinoma cell line in culture media and injecting the cancer cells into BALB/c mice. The scatterer properties of average scatterer diameter and acoustic concentration were estimated using a Gaussian form factor from the backscattered ultrasound. The parametric images showed a clear distinction between the two kinds of tumors. A statistically significant difference was observed between the estimated scatterer properties in the fibroadenoma and the carcinoma. The average scatterer diameter and acoustic concentration for the fibroadenomas were estimated at 105+/-14 mm and –15.6+/-5 dB (mm-3), respectively. The average scatterer diameter and acoustic concentration for the carcinomas was estimated to be 28+/-4.6 mm and 10.6+/-6.9 dB (mm-3), respectively.


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