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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 51 out of 330
| Title |
Bioeffects considerations for the safety of diagnostic ultrasound. |
| Author |
Mortimer A, Carstensen E, Kremkau F, Miller D, Miller M, Nyborg W, O'Brien WD Jr, Ziskin M. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1988 |
| Abstract |
No abstract available. |
| Title |
Bioeffects in echocardiography. |
| Author |
Carstensen EL, Duck FA, Meltzer RS, Schwartz KQ, Keller B. |
| Journal |
Echocardiography |
| Volume |
|
| Year |
1992 |
| Abstract |
Two mechanisms have been identified through which ultrasound as it is used clinically could produce biologically significant effects. One is heating that results from the absorption of ultrasonic energy by tissues. The other is cavitation, the ultrasonic activation of gas bodies including the potentially violent collapse of small gas bodies in or near tissue that is sometimes called transient or inertial cavitation. The heart, itself, is well perfused and the likelihood of significant heating of the heart tissues in the most extreme conditions known today is negligible. Lung also appears to be relatively immune to heating under diagnostic exposure conditions. In normal echocardiographic procedures, the only tissues that need serious consideration are the ribs. Under extreme conditions, ultrasonic heating of the bone might be as great as 6 C. Nonthermal action of ultrasound has been demonstrated to cause lung hemorrhage at pressure levels on the order of 1 MPa. Although many diagnostic devices produce focal pressures greater than this amount, it appears unlikely that hemorrhage will occur in normal echocardiographic applications. Under certain conditions, pulsed ultrasound can either stimulate or modify the contraction of the heart but the exposures required are not used in normal echocardiographic applications. Since specific devices have been identified whose outputs approach levels required to produce thermal and nonthermal effects, the user should be aware of potential biological effects, particularly in pediatric or obstetric applications, as output levels increase. |
| Title |
Bioeffects literature review. |
| Author |
Various. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1995 |
| Abstract |
Bioeffects of ultrasound on liver cells of rat embryos. Cardinale A, Lagalla R, de Maria M, Valentino B, Cabibi D, Laconi A. Act Radiol, 28:221-224, 1987...Potentiation of chemotherapy by low-level ultrasound. Harrison GH, Baker-Kubiczek EK, Eddy HA. Radiat Biol, 59:1453-1466, 1991...Imaging microbubbles and tissues using a linear focused scanner operating at 20 MHz: Possible implications for the detection of cavitation thresholds. Watmough DJ, Davies HM, Quan KM. Wytch R, Williams AR. |
| Title |
Bioeffects of diagnostic ultrasound in vitro. |
| Author |
Suhr D, Brummer F, Irmer U, Wurster C, Eisenmenger W, Hulser DF. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1996 |
| Abstract |
Biological effects induced by ultrasound were frequently reported for continuous wave (cw) mode. Thresholds for the onset of bioeffects of pulsed ultrasound, starting from diagnostic conditions, have not yet been defined by standardized in vitro models. We therefore investigated the effects of pulsed ultrasound on cultured cells using diagnostic ultrasound devices, a selfmade transducer and a sonochemical laboratory reactor tunable from pulsed diagnostic conditions to cw ultrasound. Additionally, we determined physical parameters of the ultrasonic field by.different types of hydrophones. Sonochemical reactions and the effects induced by the ultrasonic fields in cultured cells indicated a threshold for bioeffects. |
| Title |
Bioeffects of diagnostic ultrasound on auditory function in the neonatal lamb. |
| Author |
Siddiqi TA, Plessinger MA, Meyer RA, Woods JR Jr. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1990 |
| Abstract |
Abstract not available. Letter to the editor. |
| Title |
Bioeffects of positive and negative acoustic pressures in mice infused with microbubbles. |
| Author |
Dalecki D, Child SZ, Raeman CH, Xing C, Gracewski S, Carstensen EL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2000 |
| Abstract |
This study provided one test of the hypothesis that hemorrhage in tissues containing ultrasound (US) contrast agents results from inertial cavitation. The test relied on the prediction of classical cavitation theory that the response of microbubbles to negative pressures is much greater than it is for positive pressures. An endoscopic electrohydraulic lithotripter was used to generate a spherically diverging positive pressure pulse. A negative pressure pulse was produced by reflection of the positive pulse from a pressure release interface. Mice were injected with approximately 0. 1 mL of Albunex(R) and exposed to 100 pulses at either + 3.6 MPa or -3.6 MPa pressure amplitude. For comparison, mice were also exposed to the same acoustic fields without injection of contrast agents. Sham animals experienced the same protocols, with or without Albunex(R) injections, but were not exposed to the lithotripter fields. Following exposure, mice were scored for hemorrhage to various organs and tissues. When Albunex(R) was present in the vasculature, negative pressure pulses produced significantly more hemorrhage than positive pressures in tissues such as the kidney, intestine, skin, muscle, fat, mesentery and stomach. |
| Title |
Bioeffects of positive and negative acoustic pressures in vivo. |
| Author |
Bailey MR, Dalecki D, Child SZ, Raeman CH, Penney DP,.Blackstock DT, Carstensen EL. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1996 |
| Abstract |
In water, the inertial collapse of a bubble is more violent after expansion by a.negative acoustic pressure pulse than when directly compressed by a positive.pulse of equal amplitude and duration. In tissues, gas bodies may be limited in.their ability to expand and, therefore, the relatively strong effectiveness of.negative pressure excursions may be tempered. To determine the relative.effectiveness of positive and negative pressure pulses in vivo, the mortality rate.of Drosophila larvae was determined as a function of exposure to microsecond.length, nearly unipolar, positive and negative pressure pulses. Air-filled tracheae.in the larvae serve as biological models of small, constrained bubbles. Death.from exposure to ultrasound has previously been correlated with the presence of.air in the respiratory system. The degree of hemorrhage in murine lung was also.compared using positive and negative pulses. The high sensitivity of lung to.exposure to ultrasound also depends on its gas content. The mammalian lung is.much more complex than the respiratory system of insect larvae and, at the.present time, it is not clear that acoustic cavitation is the physical mechanism for.hemorrhage. A spark from an electrohydraulic lithotripter was used to produce a.spherically diverging positive pulse. An isolated negative pulse was generated by.reflection of the lithotripter pulse from a pressure release interface. Pulse.amplitudes ranging from 1 to 5 MPa were obtained by changing the proximity of.the source to the biological target. For both biological effects, the positive pulse.was found to be at least as damaging as the negative pulse at comparable.temporal peak pressure levels. These observations may be relevant to an.evaluation of the mechanical index (MI) as an exposure parameter for tissues.including lung since MI currently is defined in terms of the magnitude of the.negative pressure in the ultrasound field. . |
| Title |
Bioeffects of pulsed ultrasound. |
| Author |
Barnett SB. |
| Journal |
Australas Phys Eng Sci Med |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Bioeffects of ultrasound. |
| Author |
Dunn F, Frizzell LA. |
| Journal |
Book Chapter |
| Volume |
|
| Year |
1982 |
| Abstract |
Introduction: In the beginning of Chapter 7, the inherent nonlinear equations of acoustics were linearized to obtain a tractable approach to sound wave propagation in fluid media. This led to a benign interaction between the wave process and the propagating medium, where neither was affected by the other. The attenuation (absorption) factor was then introduced to the wave equation to describe the decrease in amplitude of the acoustic parameters as the wave process propagates through the medium. At the extreme in nonlinear phenomena are the strong shock waves characterized by discontinuities at the wave front. The interest here, however, is in the intermediate range of the nonlinear acoustic fields, where a number of distinct phenomena which are not observed in low-amplitude acoustic fields become apparent. These may account for both the reversible and irreversible biological effects produced by ultrasound. |
| Title |
Bioeffects of ultrasound: an experimental study on.human embryos. |
| Author |
Cardinale A, Lagalla R, Giambanco V, Aragona F..Department of Radiology, University of Palermo, Policlinico Filiciuzza, Italy. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1991 |
| Abstract |
The foetuses of 10 women at 9-12 weeks gestation were irradiated with ultrasound under typical diagnostic exposure conditions immediately prior to abortion. Electron microscopy of liver fragments revealed neither morphological nor structural changes. |
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