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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Title Effects of myocardial ischemia on quantitative ultrasonic backscater and identification of responsible determinants.
Author Mimbs JW, Bauwens D, Cohen RD, O'Donnell M, Miller JG, Sobel BE.
Journal Circ Res
Volume
Year 1981
Abstract Quantitative characterization of myocardial properties represent a rapidly emerging area of echocardiographic investigation. Because measurement of the ultrasonic integrated backscatter is theoretically applicable to analysis in vivo with reflected ultrasound, this study was performed to develop and evaluate a suitable method for measurement of quantitative backscatter in vivo. In view of the desirability of characterizing ischemic myocardium noninvasively, the study was performed with animal preparations simulating myocardial ischemia in humans. In one series of open-chest dogs, integrated backscatter among 22 ischemic regions was increased by 200% (P less than 0.01) compared to values in control regions within 1 hour after coronary occlusion and by 400% (-45.1 +/- 0.7 dB compared to -50.9 +/- 0.4 dB) (P less than 0.001) within 6 hours. In a second series of open-chest dogs, ischemia was quantified with 141Ce microspheres, and mean integrated backscatter was found to increase (280% of control) (P less than 0.01) in regions with flow less than 20% of control 2 hours following coronary occlusion. Additional studies with perfused hearts revealed two determinants of the increased ultrasonic backscatter observed: (1) an increase in cardiac fluid content reflected by the wet-to-dry weight ratio, and (2) the contributions of formed elements in whole blood. The results indicate that ultrasonic integrated backscatter distinguishes severely ischemic from nonischemic myocardium in vivo in open-chest animals. Because it was possible to obtain these results in the reflection mode, potential extension of the approach to clinical applications is promising.


Title Effects of ocular structures on propagation of ultrasound in the eye.
Author Lizzi FL, Burt WJ, Coleman DJ.
Journal Arch Ophthalmol
Volume
Year 1970
Abstract Examinations of ultrasonic radiation with a Schlieren optical system have demonstrated that the characteristics of ultrasonic beams can be significantly altered by acoustic phenomena which occur in lens and sclera. The magnitude of these alterations is critically dependent upon the position and orientation of the incident ultrasonic beam. Both diagnostic and therapeutic piezoelectric transducers, operating at frequencies between 1 and 10 megahertz, were employed in this study. Transmission of ultrasound though bovine lenses is accompanied by shifts in the central axis, alterations in the width, and lower intensities in the transmitted beam. Transmission through samples of bovine sclera results in significant alterations in beam characteristics only when the central axis of the incident beam is nearly tangent to the sclera surface.


Title Effects of physical parameters on high temperature ultrasound hyperthermia.
Author Billard BE, Hynynen K, Roemer RB.
Journal Ultrasound Med Biol
Volume
Year 1990
Abstract The purpose of this research was to investigate the feasibility of inducing perfusion independent, predictable therapeutic thermal dose using high power ultrasonic pulses. Computer simulations were used to study the effects of blood perfusion, tissue properties, transducer characteristics, and treatment geometry on the temperature elevation and thermal dose delivered by short ultrasonic pulses. Experiments were conducted in vitro and in vivo to investigate the effects of blood perfusion changes. Results show that short pulse lengths (less than or equal to 2 s) and small focal diameters (approximately 3 mm) give temperature elevations and thermal doses which are nearly perfusion independent. Normal fluctuations in tissue properties should not have a significant effect on the treatment provided that proper choice of transducer is made for each individual application.


Title Effects of prenatal exposure to ultrasound.
Author Sikov MR, Hildebrand BP.
Journal Adv SBD
Volume
Year 1979
Abstract No abstract available.


Title Effects of prenatal ultrasound exposure on adult offspring behavior in the Wistar rat.
Author Jensh RP, Lewin PA, Poczobutt MT, Goldberg BB, Oler J, Goldman M, Brent RL.
Journal Proc Soc Exp Biol Med
Volume
Year 1995
Abstract An ultrasound exposure tank was specifically designed for experimental.bioeffects studies. Thirty-six pregnant rats were anesthetized, immersed to the.axilla in a water tank, and exposed on Day 15, 17, and 19 of gestation. Twelve.rats were exposed to 5.0 MHz pulsed ultrasound of effective pulse duration equal.to approximately 0.170 microseconds, pulse repetition rate (PRF) 1 kHz, and a.spatial peak, temporal peak intensity (lsptp) of 500 W/cm2, representing a.clinically appropriate exposure level. The spatial peak pulse average (lsppa),.spatial peak temporal average (lspta), and instantaneous maximum (lm).intensities were determined to be 100 W/cm2, 24 mW/cm2, and 230 W/cm2,.respectively. The maximum rarefraction pressure, pr, was measured as 12.5 x.10(5) Pa, and the total power was 2.5 mW. Twelve other rats were exposed to.1500 W/cm2, lsptp, and 12 were sham insonified. Since the focal area was about.0.05 cm2, computer controlled stepper motors moved the rats through the.ultrasound field to ensure uniform exposure of the abdominal/pelvic region. Total.exposure time was 35 min. A miniature thermocouple was implanted in a few.rats to verify that no significant temperature increase took place due to exposure..A total of 278 offspring were maintained until postnatal Day 60 when they were.subjected to two of four behavioral tests in random order within sexes. The.results indicate no consistently observed dose-related alterations in adult behavior.due to prenatal fetal exposure to 5.0 MHz ultrasound below an intensity (lsptp).of 1500 W/cm2. .


Title Effects of pulse-wave ultrasonic irradiation on mouse embryos.
Author Takabayashi T,Abe Y,Sato S,Sato A,Suzuki M.
Journal Jpn J Med Ultrason
Volume
Year 1981
Abstract C3H/He mouse embryos in-utero were exposed to experimental intense pulsed ultrasound in day 8 of pregnancy. Fetal anomaly was observed in the mice exposed to 58.6 W/cm peak intensity pulsed ultrasound for 5 min, but not in the group exposed to reduced peak intensity with the same pulse width and repetition rate. In spite of similar mean acoustic intensity, the group exposed to higher peak intensity that was 59.4 W/cm2 produced fetal anomaly, but not by lower peak intensity level. No anomaly of fetal mouse was noted after the exposure to ultrasound with smaller pulse width that was 3 μs, and even with the peak intensity of 60 W/cm2. It is suggested that the teratogenicity depends on peak intensity, as well as pulse width of the ultrasound. Critical acoustic intensity in day 8 of mouse pregnancy is estimated to be 60 W/cm2 in SATP and 1.2 W/cm2 in SPTA values.


Title Effects of pulsed ultrasound on ocular tissue.
Author Lizzi FL, Coleman DJ, Driller J, Franzen LA, Leopold M.
Journal Ultrasound Med Biol
Volume
Year 1981
Abstract Focused ultrasound at a center frequency of 9.8 MHz was used to create lesions of the retuna and choroid in the proptosed eye of the anesthetized albino rabbit. Pulsed ultrasound was employed and results were compared to those obtained under continuous-wave (CW) exposures. Short pulses (e.g. 100 microseconds) delivered at high repetition frequencies (e.g. 3 KHz) produced the same average intensity threshold values as those found for CW conditions. Longer pulses (e.g. 0.1 sec) delivered at low repetition frequencies (e.g. 2 Hz) produced lesions at lower temporally averaged intensities. The lowered thresholds are related to cyclical blanching occurring in insonified choroidal blood vessels. All lesion-producing intensities (approximately 100 W/cm2) were orders of magnitude larger than diagnostic levels.


Title Effects of pulsed ultrasound on the frog heart: I. Thresholds for changes in cardiac rhythm and aortic pressure.
Author Dalecki D, Keller BB, Raeman CH, Carstensen EL.
Journal Ultrasound Med Biol
Volume
Year 1993
Abstract High intensity pulsed ultrasound at 1.2 MHz is shown to change the cardiac.rhythm and aortic pressure of frog hearts in vivo. Threshold levels for these.effects occur at acoustic pressure amplitudes of the order of 10 MPa for 5 ms.pulse lengths. Depending upon the phase of the heart cycle, a pulse of ultrasound.either may cause a premature ventricular contraction, a reduction in the strength of.contraction as measured by the aortic pressure, or an enhanced relaxation of the.heart muscle. There is an increase in the effectiveness of the ultrasound with.increase in pulse length in the range from 1 to 5 ms.


Title Effects of pulsed ultrasound on the frog heart: III. The radiation force mechanism.
Author Dalecki D, Raeman CH, Child SZ, Carstensen EL.
Journal Ultrasound Med Biol
Volume
Year 1997
Abstract Earlier studies have shown that a single, millisecond duration pulse of ultrasound delivered to the frog heart in vivo during systole can produce a reduction in the developed aortic pressure, while a pulse delivered during diastole can produce a premature ventricular contraction. The threshold for these effects is 5-10 MPa with a 5-ms pulse. Since cardiac tissues respond to mechanical stimulation, the objective of this study was to investigate acoustic radiation force as a possible mechanism for the observed effects of ultrasound on the frog heart. In two experiments, the.radiation force exerted on the heart was varied by varying the ultrasonic frequency and the acoustic beam width. Results of these studies indicated that the rate of occurrence of the reduced aortic pressure effect was directly correlated with the magnitude of the radiation force exerted on the heart. A third experiment tested the radiation force mechanism directly by placing an acoustic reflector on the frog heart. The acoustic reflector maximized the radiation force delivered to the heart, but eliminated direct interaction of the ultrasound with the heart and experimentally.eliminated heating and cavitation as mechanisms of action. The reduced aortic pressure effect was observed with the reflector on the heart, indicating that radiation force is capable of producing this effect. No premature ventricular contractions were observed with the acoustic reflector over the heart, suggesting that another property of the exposure may be responsible for this bioeffect. .


Title Effects of pulsed ultrasound on the mouse neonate: Hind limb paralysis and lung hemorrhage.
Author Frizzell LA, Chen E, lee C.
Journal Ultrasound Med Biol
Volume
Year 1994
Abstract Exposure conditions were determined for hind limb paralysis and lung hemorrhage of neonatal mice due to pulsed exposure (10μs pulse duration) to 1 MHz focused ultrasound. Spatial peak pulse average intensity and peak rarefactional pressure levels for paralysis in 50% of specimens sonicated were determined for pulse repetition frequencies of 1, 5 and 50 kHz at 10°C and 2.4 s exposure duration. The results suggest that cavitation was involved in the paralysis at a pulse repetition frequency (PRF) of 50 kHz, but that cavitation took place in the coupling medium and probably not within the specimen during exposures at a PRF of 5 kHz. The results show an inverse relation between spatial peak pulse average intensity, or peak rarefactional pressure and sound on-time. Exposure conditions for lung hemorrhage were determined for a pulse duration of 10 μs at 10°C and exposure durations of 2.4 and 180 s. The results show that the threshold exposure conditions for lung hemorrhage are much less than the conditions for cavitational or other effects reported for tissues that do not contain well defined gas bodies. In addition, the results show an inverse relation between exposure level and either exposure duration or sound on-time, suggesting that time is an important parameter associated with bubble effects.


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