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.

Page 78 out of 330

Title Current status of toxicity investigations.
Author Taylor KJ.
Journal J Clin Ultrasound
Volume
Year 1974
Abstract Because diagnostic ultrasound is becoming widely recognized as a valuable diagnostic aid, its potential for producing toxicity must be considered. The current modes of usage are considered with regard to their dosage parameters and to the physical and biological effects of such dosages. The reported bioeffects involved in future applications are briefly presented and the necessity for a proper epidemiological survey is stressed.


Title Current time-domain methods for assessing tissue motion by analysis from reflected ultrasound echoes-a review.
Author Hein IA, O'Brien WD Jr.
Journal IEEE Trans UFFC
Volume
Year 1993
Abstract The Doppler technique has traditionally been the method used to extract motion information from ultrasonic echoes reflected by moving tissues. The Doppler technique has been around for a long time, and has been extensively reviewed and analyzed in the literature. Recently, time-domain methodologies for estimating tissue motion have gained in popularity. Time-domain methods have advantages over Doppler methods in many applications, and as of yet have not been comprehensively reviewed. An overview of time-domain techniques that have appeared in the literature over the past few years is presented. Their potential advantages over Doppler are examined, and the individual techniques are compared.


Title Cylindrical ultrasonic transducers for cardiac catheter ablation.
Author Hynynen K, Dennie J, Zimmer JE, Simmons WN, He DS, Marcus FI, Aguirre M.
Journal IEEE Trans Biomed Eng
Volume
Year 1997
Abstract This study was designed to evaluate the feasibility of using cylindrical ultrasound transducers mounted on a catheter for the ablation of cardiac tissues. In addition, the effects of ultrasound frequency and power was evaluated both using computer simulations and in vitro experiments. Frequencies of 4.5, 6, and 10 MHz were selected based on the simulation studies and manufacturing feasibility. These transducers were mounted on the tip of 7-French catheters and applied in vitro to fresh ventricular canine endocardium, submerged in flowing degassed saline at 37°C. When the power was regulated to maintain transducer interface temperature at 90-100°C, the 10-, 6-, and 4.5-MHz transducers generated a lesion depth of 5.9±0.2 mm, 4.6±1.0 mm, and 5.3±0.9 mm, respectively. The 10-MHz transducer was chosen for the in vivo tests since the maximum lesion depth was achieved with the lowest power. Two dogs were anesthetized and sonications were performed in both the left and right ventricles. The 10-MHz cylindrical transducers caused an average lesion depth of 6.4±2.5 mm. In conclusion, the results show that cylindrical ultrasound transducers can be used for cardiac tissue ablation and that they may be able to produce deeper tissue necrosis than other methods currently in use.


Title Cytotoxic effects of ultrasound in vitro dependence on gas content, frequency, radical scavengers, and attachment.
Author Armour EP, Corry PM.
Journal Radiat Res
Volume
Year 1982
Abstract CHO cells were exposed to therapeutic-intensity ultrasound under various conditions. Cell killing was dependent upon the amount of gas dissolved in the treatment medium. No decrease in survival was observed at 2.40 and 3.40 MHz under conditions which had produced killing at 1.70, 1.07, and 0.82 MHz. Cell death occurred primarily within 15 min of exposure and probably involved membrane damage. One radical scavenger, cysteamine, completely protected the cells from ultrasound-induced damage whereas another, cystamine, did not. Attachment of the cells to a Mylar membrane also protected them from damage. Under conditions most closely resembling in vivo ultrasound exposures no decrease in survival was observed for intensities as great as 14 W/cm(2) and 30-min duration. The cell killing observed was apparently due to cavitation and may have involved formation of intracellular radicals. Although the role of radicals is not unequivocally demonstrated, a better understanding of the mechanisms of ultrasound-induced damage is needed before this modality can be considered to be without deleterious effects under all conditions.


Title Damage to murine kidney and intestine from exposure to the fields of a piezoelectric lithotripter.
Author Raeman CH, Child SZ, Dalecki D, Mayer R, Parker KJ, Carstensen EL.
Journal Ultrasound Med Biol
Volume
Year 1994
Abstract Earlier studies, in which murine kidneys were exposed to spherically diverging, spark-generated shock waves, demonstrated extensive hemorrhage in the interior of the organ at peak positive pressures somewhat less than 10 MPa. With comparable pulse numbers, this investigation, using the focal fields of a piezoelectric lithotripter, found no damage to murine kidneys at peak positive pressures as high as 40 MPa. Comparison of these cases and earlier bioeffects studies using pulsed, focused ultrasound leads to the conclusion that damage to murine kidneys is not simply correlated with peak positive pressure or peak negative pressure, nor is spectral content of the wave able to explain the striking differences in damage from these sources. With 200 individual shock waves from the piezoelectric lithotripter applied ventrally, 20-30% of the animals suffered superficial kidney damage (bleeding into the capsule), but the same exposure conditions produced severe intestinal hemorrhage in more than 80% of the animals.


Title Damage to red blood cells induced by acoustic cavitation.
Author Daniels S, Kodama T, Price DJ.
Journal Ultrasound Med Biol
Volume
Year 1995
Abstract This experimental study has revealed damage to red blood cells that is quantitatively related to the acoustic pressure during irradiation with 0.75-MHz continuous-wave ultrasound, using a range of intensities comparable to those employed by ultrasonic physiotherapy equipment (0.25 to 7 W cm-2 spatial average temporal average). Damage to the red blood cells was investigated by measuring the extent of haemolysis using a UV/VIS spectrophotometer. There was a clear correlation between the amount of haemoglobin released and the intensity of harmonic emissions recorded from the sample during irradiation. The observed degree of haemolysis could not be produced by temperature rises in the absence of the sound field. This suggests that the damage was a direct result of acoustic cavitation.


Title Détection et caractérisation de la destruction des microbulles de produit contraste ultrasonore (Detection and characterization of ultrasound contrast agent microbubble destruction).
Author Ammi AY
Journal Thesis(PhD): Univérsite Paris VI
Volume
Year 2006
Abstract Ultrasound contrast agents present a significant potential for imaging and therapy. This potential is linked to a better understanding of the destruction phenomena of the microbubbles present in these agents. The aim of this work was to detect, characterize and quantify destruction of isolated ultrasound contrast agent microbubbles. The tools applied toward this objective were a model for nonlinear shelled-bubble-wall emissions were detected using the first experimental events following microbubble shell rupture. This link is illustrated with microbubble dynamics model. Thereupon, an automatic algorithm is developed to detect the post-excitation signals. Destruction thresholds and percent occurence of destruction for Optison™ microbubbles are estimated using these post-excitation signals for three frequencies (0.9, 2.8 and 4.6 MHz) and three durations (3, 5 and 7) of the incident acoustic pulse across a range of incident peak rarefactional pressures from 0.07 to 5.39 MPa. The second system consisting of a double passive cavitation detector was used to compare the temporal and spectral response of oscillating and ruptured microbubbles across a large bandwidth, including the transmit bandwidth. The third system permitted verification by optical microscopy that post-excitation signals were present only when the microbubble was destroyed. The post excitation signals provide an acoustic signature of the microbubble destruction and enable the characterization and the quantification of destruction.


Title Decision-directed line detection with application to medical ultrasound.
Author Czerwinski RN, Jones DL, O'Brien WD Jr.
Journal Proc SPIE
Volume
Year 1996
Abstract This paper presents a method of enhancing linear and curvilinear image features, such as those corresponding to tissue discontinuities in medical ultrasound. The method is an extension of a template based technique for line enhancement which produces a test statistic at each point by projecting the pixels near that point onto a line segment, varying the orientation of the segment to maximize the projected value, and retaining the projected value as the test statistic. In the past, we have not made use of information about which angle produced the maximum value at each point. In this paper, we compute a histogram of the angles near each point to gain an indication of the direction of larger scale linear features lying nearby. Mathematically, we wish to estimate a set of prior probabilities for the orientation of line segments that pass through each point. The priors can then be used to improve the power of the Bayesian line detection procedure. In addition, they can also be used to improve the visual quality of the image produced by plotting the test statistics on an image raster. We have found that such an image is revealing because it shows more sharply the edges of the linear components, making them more clearly visible and their fringes more distinguishable from the background. With the incorporation of prior information, the processed image shows a further improvement in visual and machine detectability of linear components, due to increased difference in gray level between points lying on edges and those lying away. This technique has potential to significantly improve the machine detectability of tissue discontinuities in medical ultrasound, as well as linear features in other forms of computed imaging.


Title Decorrelation characteristics of transverse blood flow along an intravascular array catheter.
Author Lupotti FA, Cespedes EI, van der Steen AFW.
Journal IEEE Trans UFFC
Volume
Year 2000
Abstract In recent years, a new method to measure transverse blood flow based on the decorrelation or radio frequency (RF) signals has been introduced. In this paper, we investigated the decorrelation characteristics of transverse blood flow measurement using an intravascular ultrasound (IVUS) array catheter by means of computer modeling. Blood was simulated as a collection of randomly located point scatterers. Moving this scattering medium transversally across the acoustical beam represented flow. Firstorder statistics were evaluated, and the signal-to-noise ratio from the signals was measured. The correlation coefficient method was used to present the results. The decorrelation patterns for RF and for RF-envelope signals were studied. The decorrelation patterns from the RF signals were in good agreement with those obtained from theoretical beam profiles. This agreement suggests that the decorrelation properties of an IVUS array catheter for measuring quantitative transverse blood flow can be assessed by measuring the ultrasound beam. A line of point scatterers, moved transversally across the acoustical beam (line spread function), can determine this decorrelation behaviour.


Title Decreased aggregation of mouse platelets after in vivo exposure to ultrasound.
Author Lunan KD, Wen AC, Barfod ET, Edmonds PD, Pratt DE.
Journal Thromb Haemost
Volume
Year 1979
Abstract No abstract available - article is letter to the editor


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