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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 250 out of 330
| Title |
The biological effects of ultrasound. |
| Author |
O'Brien WD Jr, Dunn F. |
| Journal |
Rep U S Dept HEW |
| Volume |
|
| Year |
1972 |
| Abstract |
Sound can produce biological effects a fact that was observed as early as 1917 (Langevin, 1917) during the development of instrumentation for the detection of submarines. Fish and other marine organisms were reported to be torn apart in the vicinity of the sonar experiments. It is now common knowledge that ultrasound is one of the most efficient available means for complete tissue and cell disruption. Ultrasonicators are commonly used commercial tools in biological laboratories. Thus, the question is not whether or not ultrasound is a hazard but rather at what levels do risks of exposure become significant. But first, the purpose of this report is to summarize the known biological effects of ultrasound. |
| Title |
The biological effects of ultrasound. |
| Author |
O'Brien WD Jr, Fred RK. |
| Journal |
Rep U S Dept HEW |
| Volume |
|
| Year |
1972 |
| Abstract |
No abstract available. |
| Title |
The biophysical mode of action of biologic and therapeutic ultrasonic reactions. |
| Author |
Lehmann JF. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1953 |
| Abstract |
A review is presented of numerous biophysical studies concerning the action of ultrasound on living matter, with particular reference to therapeutic applications. On the basis of the experiments described, involving various physical, physiochemical, and chemical effects, it is concluded that selective heating caused by the radiation plays the major role quantitatively under therapeutic conditions. However, ultrasound also produces a mechanical effect. The diffusion layer at an interface is decreased by stirring, and thus exchange of metabolites is augmented. |
| Title |
The botanical effects of ultrasound: A review. |
| Author |
Miller DL. |
| Journal |
Environ Exp Bot |
| Volume |
|
| Year |
1983 |
| Abstract |
Botanical subjects have proven convenient and fruitful for investigations of effects of ultrasound. In plant tissues, such as stems, leaves and roots, which contain intercellular gas-filled channels, the channels play a major role in promoting effects. Certain gas channels apparently undergo resonant pulsation under typical ultrasonic exposure conditions and the processes involving the channels are similar to the activity of ultrasonic cavitation. The pulsation of the channels generates microscopic-scale perturbations, such as acoustic microstreaming, within the plant cells, which can disrupt normal cellular organization and function. Irreversible effects appear to be limited to cell death. Other well documented changes, such as chromosome abnormalities, mitotic index reductions and growth-rate reductions in roots, all appear to be reversible in that normal behavior is regained in surviving plants within hours or days. Genetic changes and growth enhancement have been reported but remain controvertible. Most changes are observable for spatial and temporal peak intensities in the range 0.3-30 W/cm2 for on-times in the range of 0.1-1000 sec, and in the commonly-used frequency range of 0.5-10 MHz. |
| Title |
The cavitation threshold of human tissue exposed to 0.2-MHz pulsed ultrasound: Preliminary measurements based on a study of clinical lithotripsy. |
| Author |
Coleman AJ, Kodama T, Choi MJ, Adams T, Saunders JE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1995 |
| Abstract |
Evidence of acoustic cavitation was identified in the form of transient echoes in ultrasound B-scan images of patients receiving extracorporeal shock-wave lithotripsy treatment on a Storz Modulith SL20. This lithotripter generates 10- mu s duration pulses with a centre frequency of 0.2 MHz at a pulse repetition frequency of 1 Hz. The visual appearance of B-scan images was examined in a total of 30 patients and a quantitative analysis of echogenicity changes was carried out in six cases involving lithotripsy treatment of stones in the renal pelvis. In these patients new echoes were identified in images unaffected by movement artefacts and were found to occur in perinephric fat and adjacent muscle and kidney tissue at positions close to the axis of the shock-wave field between 1 and 2 cm in advance of the indicated beam focus of the lithotripter. The echogenicity within each region increased significantly above the background level when the output of the lithotripter was increased above a threshold value. The acoustic pressures corresponding to this threshold were measured in water using a calibrated PVDF membrane hydrophone. After correction for attenuation in tissue the cavitation thresholds, in terms of the temporal peak negative pressure, are found to lie between 1.5 MPa and 3.5 MPa in all six cases. Interpretation of the measured values in terms of the likely threshold at the higher frequencies used in diagnostic ultrasound is considered using a theoretical model. |
| Title |
The central nervous system with ultrasound. |
| Author |
Fry WJ, Mosberg WH Jr, barnard JW, Fry FJ. |
| Journal |
Unknown |
| Volume |
|
| Year |
1954 |
| Abstract |
No abstract available. |
| Title |
The changes in acoustic attenuation due to in vitro heating. |
| Author |
Clarke RL, Bush NL, Ter Haar GR. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2003 |
| Abstract |
The effects of heat-generated changes on the attenuation of ultrasound (US) by porcine liver tissue have been studied over a frequency range of 2.0 to 5.0 MHz. Samples of fresh tissue, 4- to 5-mm thick, were pressurized and cooled before measurement. The insertion loss was measured at room temperature, using a broadband 3.5-MHz transducer of focal length 10 cm, employing a pulse-reflection technique. Fourier analysis of the results gave the frequency-dependence of the insertion loss. Samples were then heated in a water bath to a temperature in the range of 40 to 80?C, for between 30 and 500 s. The insertion loss was then re-measured at room temperature. The frequency-dependence of the change in insertion loss, expressed as a coefficient, in dB/cm, was fitted by linear regression, from which the attenuation change at 3.5 MHz was determined. This change was attributed to protein coagulation. Increases of up to 2.4 dB/cm, (80?C, 300 s) were found. The averaged data were fitted to a single step exponential model, resulting in a time constant on the order of 118 ? 5 s, and an asymptotic limit to the increase of attenuation coefficient of 2.67 ? 0.5 dB/cm.
|
| Title |
The chemistry of ultrasound. |
| Author |
Suslick KS. |
| Journal |
YearBook Sci Future |
| Volume |
|
| Year |
1994 |
| Abstract |
No abstract available. |
| Title |
The combination treatment of ultrasound and antitumor drugs on Yoshida sarcoma. |
| Author |
Yumita N, Okumura A, Nishigaki R, Umemura K, Umemura S |
| Journal |
Jpn J Hyperthermic Oncol |
| Volume |
|
| Year |
1987 |
| Abstract |
The antitumor effect ultrasound (ULS) and/or antitumor drugs such as daunomycin (daunorubicin, DNR) and adriamycin (ADM) were determined in the rats bearing Yoshida sarcoma. The ULS transducer that was placed on the tumor was cooled to keep the temperature of the tissue within the nonthermal range. For the choice of the timing of the ULS irradiation after the administration of the drug, the drug concentrations in the tumor and blood were determined and were analyzed pharmacokinetically. The drugs or ULS showed antitumor effect judged by the growth of the tumor size or the survival time of the rat. The combination treatment of ULS and the drug marked an additional or synergistic effects on Yoshida sarcoma. |
| Title |
The combined concentric-ring and sector-vortex phased array for MRI guided ultrasound surgery. |
| Author |
Fjield T, Hynynen K. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1997 |
| Abstract |
MRI guided ultrasound surgery requires small surgical equipment volumes to facilitate the treatment of larger patients in the limited space of a conventional MRI magnet. In addition, large focal volumes are required to reduce the treatment time of large tumors. The concentric-ring array is capable of moving the focus in one dimension, and previous studies have shown that a circular array composed of radial sectors is capable of producing enlarged focal volumes. These two array designs may be combined to create an array that is capable of both enlarging the focus and moving the focus along the axis of the array. Simulations were performed to predict the performance and capabilities of various combined array designs by using numerical routines to calculate the acoustic power field, temperature distribution, and accumulated thermal dose. The results shown predict that the combined array can create necrosed tissue volumes over 30 times larger than the concentric-ring array while maintaining focal range. The simulation results were verified with an experimental array consisting of 13 rings and 4 sectors. In addition, simulations were performed where multiple focal patterns were cycled in the time domain to create an optimized heating pattern characterized by uniform thermal dose over the volume of the lesion. Such heating patterns resulted in a 40?C lower maximum temperature compared to single mode sonications while producing the same necrosed tissue volume, and yielded a rate of necrosis of 26.4 cm(3)/h. |
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