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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 198 out of 330
| Title |
Photochemical detection of platelet damage induced by low intensity ultrasound. |
| Author |
Miller DL, Williams AR, Nyborg WL. |
| Journal |
Proc Twenty-fourth Annu Meet AIUM - Montreal |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Physical action of intense high frequency sound on vertebrate tissue. |
| Author |
Fry WJ, Dreyer LL, Dunn F, Fry FJ, Kelly EK. |
| Journal |
Rep WADC |
| Volume |
|
| Year |
1958 |
| Abstract |
The work described and the results presented in Part A of this report relate to the initiation of an elaborate series of experiments designed to yield information regarding the fundamental physical mechanisms involved in the irradiation of biological materials with ultrasound. The work was undertaken to demonstrate that it is possible to realize accurately reproducible results on a suitably prepared and precisely irradiated biological specimen. In part B some aspects of the muscle contraction problem are discussed and an elaborate precision muscle irradiation laboratory, including a new type of myograph are discussed. Results with this instrument are not included. |
| Title |
Physical and biochemical stability of Optison, an injectable ultrasound contrast agent. |
| Author |
Podell S, Burascano C, Gaal M, Golec B, Maniquis J, Mehlhaff P. |
| Journal |
Biotechnol Appl Biochem |
| Volume |
|
| Year |
1999 |
| Abstract |
Optison? is an ultrasound contrast agent, consisting of gas-filled microspheres surrounded by a solid shell of heat-denatured human albumin. Size-distribution measurements of these microspheres are a critical stability indicating factor, because loss of encapsulated gas eliminates ultrasound contrast activity. Composition of the encapsulated gas is also critical, because air-filled microspheres do not persist nearly as long in vivo as microspheres filled with less soluble gases. Optison? stability has been tested during exposure to chemical substances expected to dissolve microsphere shells. In addition, size-distribution and gas-composition measurements were used to evaluate the effects of external gas composition, elevated temperature, mixing, needle shear and pressure on product stability. Optison? microsphere shells dissolve only when exposed to relatively extreme chemical conditions, such as low pH (< 4.0), detergents or chaotropic salts. The shells are highly gas-permeable, and microspheres lose encapsulated gas rapidly and irreversibly when exposed to gas-deficient liquids. Pressure, impact stress, and the application of ultrasound energy all cause liquids to become gas-deficient, and also cause irreversible gas loss. Pressure sensitivity differs dramatically between mixed and unmixed microspheres, further supporting the conclusion that gas diffusion is the major cause of Optison? instability. To preserve the efficacy of Optison? as an ultrasound contrast agent, it is necessary to devote special attention to minimizing opportunities for gas exchange, mixing and exposure to gas-deficient liquids, so that the size distribution and gas composition of the original product are maintained during handling. |
| Title |
Physical factors involved in ultrasonically induced changes in living systems: I. Identification of non-temperature effects. |
| Author |
Fry WJ, Wulff VJ, Tucker D, Fry FJ. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1950 |
| Abstract |
The results of the first step in a systematic investigation of the mechanism of the action of ultrasound on tissue are reported. The temperature changes resulting from absorption of acoustic energy were determined while irradiation was in progress. Experimental evidence is presented which demonstrates the existence of non-temperature effects in various nerve tissue preparations. |
| Title |
Physical factors involved in ultrasonically induced changes in living systems: II. Amplitude duration relations and the effect of hydrostatic pressure for nerve tissue. |
| Author |
Fry WJ, Tucker D, Fry FJ, Wulff VJ. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1951 |
| Abstract |
The results of experiments with frogs under a hydrostatic pressure demonstrate that cavitation is not an important factor in the mechanism of production of paralysis of the hind legs of frog by ultrasonic (frequency one megacycle) irradiation over the lumbar enlargement region of the spinal cord. Experimental results indicate that a linear relation exists between the reciprocal of the minimum exposure time for paralysis and the acoustic amplitude. This result is readily described in terms of a one factor rate process. On the basis of this experimentally determined relation, it is shown that time rate of change of temperature cannot be correlated with the observations. It is concluded on the basis of a theoretical calculation that absorption of ultrasound at interfaces in the spinal cord does not result in minute hot regions. Further work on summation of subparalytic doses, spaced apart at various time intervals, indicates that the recovery process following exposure to a subparalytic dose of ultrasonic radiation may not be a monotonic function of time. |
| Title |
Physical instumentation for the application of ultrasound in vestibular distributions. |
| Author |
Kossoff G. |
| Journal |
Rep Commonw Aust |
| Volume |
|
| Year |
1962 |
| Abstract |
No abstract available. |
| Title |
Physical mechanism of the lession of biological tissues by focused ultrasound. |
| Author |
Gavrilov LR. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1974 |
| Abstract |
The physical mechanism of the lesion of biological tissues by focused ultrasound is investigated. The results of measurements of the cavitation thresholds in the brain tissues of experimental animals are given. A method is proposed for determining the ultrasonic dosages corresponding to the cavitation and thermal regimes of biological tissue destruction. |
| Title |
Physical mechanisms for biological effects of ultrasound at low-intensity levels. |
| Author |
Nyborg WL, Miller DL. |
| Journal |
Ultrasound Interact Biol Med |
| Volume |
|
| Year |
1983 |
| Abstract |
No abstract available. |
| Title |
Physical mechanisms for biological effects of ultrasound. |
| Author |
Nyborg WL. |
| Journal |
Rep U S Dept HEW |
| Volume |
|
| Year |
1977 |
| Abstract |
In this report, available information is reviewed on the principles or mechanisms, as they are often called, by which ultrasound procedures changes in living systems. In the science of biological ultrasound, as in any other science, a knowledge of principles is valuable in that it enhances our ability to make predictions. It is natural to stress physical mechanisms because ultrasound is a physical agent. The mechanism best understood is that of sonically generated heat. Temperature elevations can lead to significance alterations in rates of biochemical reactions, to structural breakdown of macromolecules and membranes, and to abnormalities in developing organisms. Many experiments have been done in which ultrasound is applied to aqueous suspensions of macromolecules or cells; in these, enzymes may be inactivated or cells modified in structure and/or function. Here (when temperature elevation is avoided) the mechanism is usually sonic cavitation, an activity of small bodies comprised of gas or vapor. When ultrasound produces bioeffects under conditions where temperature elevation is ruled out the mechanism can sometimes be identified as one associated with time-averaged sonically generated stresses. Among mechanisms in this class are the phenomena of radiation force (time-averaged torque on a small body, which may cause it to twist or spin) and acoustic microstreaming (time-averaged circulations set up in fluid-filled spaces). Viscous stresses associated with acoustic microstreaming are especially important near microscopic gaseous bodies; it is important to know whether these exist in mammalian systems. The report also contains a brief summary of available data for effects of ultrasound on mammalian tissues. In particular the lowest intensity levels at which significant effects have been reported are compared with lev |
| Title |
Physical mechanisms of the action of intense ultrasound on tissue. |
| Author |
Dunn F. |
| Journal |
Am J Phys Med |
| Volume |
|
| Year |
1958 |
| Abstract |
No abstract available. |
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