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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 160 out of 330
| Title |
Investigation of the effect of diagnostic ultrasound on brain growth and neurone proliferation of foetal and immature rats a preliminary report. |
| Author |
Ogden JR. |
| Journal |
Proc Br Inst Radiol |
| Volume |
|
| Year |
1971 |
| Abstract |
No abstract available. |
| Title |
Investigation of the possibilities of cardiac defibrillation by ultrasound. |
| Author |
Smailys A, Dulevicius Z, Muckus K, Dauksa K. |
| Journal |
Resuscitation |
| Volume |
|
| Year |
1981 |
| Abstract |
In 15 experiments on dogs ultrasound with a frequency of 500 kHz and an intensity of 10 W/cm2, exerted a defibrillatory and antiarrhythmic effect and stopped ventricular fibrillation in 28% of the animals. Electrophysiological studies on isolated right ventricles of rabbits in oxygenated chambers demonstrated that the antiarrhythmic action of the ultrasound acted by prolonging the refractory period of the myocardial cells. Ultrasound with an intensity of 4 W/cm2 and 30 s duration increased the refractory period up to 37%. Any further increase of intensity and duration of the ultrasound action resulted in a shortening of the refractory period and inhibition of the electrical activity of the myocardial cells. Investigations of the harmful effects of ultrasound with a frequency of 500 kHz and an intensity of 10 W/cm2 showed that ultrasound for up to 2 min did not cause evident histological changes. |
| Title |
Investigation of the relationship of nonlinear backscatteresd ultrasound intensity with microbubble concentration at low MI. |
| Author |
Lampaskis M,Averkiou M. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2010 |
| Abstract |
he aim of this study was to measure the relationship of image intensity with contrast agent concentration. In vitro experiments were performed with a flow phantom and a sulphur hexafluoride filled microbubble contrast agent (SonoVue) at different concentrations (0.004‰ to 4‰) covering the range commonly encountered in clinical practice. The concentration of microbubbles in the contrast agent solutions was confirmed optically. Images were collected with a diagnostic ultrasound system (iU22, Phillips Medical Systems, Bothell, WA, USA) and with a nonlinear imaging technique (power modulation) at low mechanical index (MI=0.05) to avoid bubble destruction. The mean intensity within a region of interest was measured to produce time-intensity curves from linearized (absolute scale) data. The relationship of linearized image intensity to contrast agent concentration was found to be linear up to 1‰ and reached a plateau at approximately 2‰. To operate in the linear range of the intensity-concentration relationship the contrast agent dose should be adjusted to avoid those high values in vivo and the highest dynamic range of the ultrasound system should be used to avoid unnecessary signal saturation. (E-mail: maverk@ucy.ac.cy). |
| Title |
Investigation of the velocity and absorption coefficient of ultrasound in ethyl acetate with a constant density. |
| Author |
Kal'yanov BI, Nozdrev VP. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1960 |
| Abstract |
No abstract available. |
| Title |
Investigation of ultrasonic absorption in concentrated polymer solutions over a wide frequency range. |
| Author |
Mikhailov IG, Safina EB. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1972 |
| Abstract |
The absorption of ultrasound in concentrated solutions of polymethyl methacrylate (PMMA) and polystyrene (PS) in toluene in the frequency range from 3 to 900 MHz and in solutions of the same polymers in methyl ethyl ketone in the range from 24 to 900 MHz has been investigated at concentrations of 3 to 8 g/100 ml and at a temperature of 20 ?C. The measurements were performed by the pulse method. It is established that the region of dispersion of the additional absorption *a /?(^2) occupies a narrow frequency interval, and the character of the frequency dependence predicted by the theory of ultrasonic absorption in concentrated polymer solutions is not confirmed experimentally. |
| Title |
Investigation of ultrasound image processing to improve perceptibility of microcalcifications. |
| Author |
Kamiyama N, Okamura Y, Kakee A, Hashimoto H. |
| Journal |
J Med Ultrasonics |
| Volume |
|
| Year |
2008 |
| Abstract |
Purpose
This article describes an investigation of the detectability of breast microcalcifications by ultrasound imaging.
Methods
Two kinds of experiments were performed to evaluate the spatial and contrast resolution of microstructures in an agar graphite phantom and to analyze human perception of tiny spots.
Results
The results showed that most of the difficulties in finding microstructures were not only due to lower echo levels but also to obstructions in the surrounding texture of the image. Based on these results, a new image processing method was proposed to emphasize microcalcifications in mammary glands. This method utilized statistical analysis of the echo signals and also considered the structural pattern of the mammary gland. Processed images from some clinical cases showed adequate extraction of the microcalcifications with efficient cancellation of the mammary gland structure.
Conclusion
The results suggested that the perception of microcalcifications could be improved by the proposed method.
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| Title |
Investigations of the advantages of a multiple frequency ultrasound breast examination instrument. |
| Author |
Kelly-Fry E, Jackson VP. |
| Journal |
Proc World Fed Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
| Title |
Investigations of the effects of heat and of ultrasound on terminally-differentiated cells: using the erythrocyte as a model system. |
| Author |
Kozma TG. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1992 |
| Abstract |
No abstract available. |
| Title |
Investigations of ultrasound biological effects using laboratory animals. |
| Author |
O'Brien WD Jr. |
| Journal |
Lab Anim |
| Volume |
|
| Year |
Unknown |
| Abstract |
The use of ultrasound as a therapeutic tool became rather widespread more than a quarter of a century ago and has maintained this global usage. The use of ultrasound as a diagnostic tool in clinical medicine has possibly increased exponentially during the past decade. A huge literature describes the multiplicity of purposes for which ultrasound is either superior to, or a valuable adjunct to, conventional radiographic techniques. There is a belief, common among both referring physicians, radiologists, and therapy employers of this modality that exposure to ultrasound is without any harmful effects in humans, at least as compared to x-ray. The latter is certainly true since ultrasound is a non-ionizing form of radiation, and it may be more generally true as the biological effects of ultrasound in general occur at levels normally considered to be far beyond those of clinical diagnostic exposures. However, within the last few years, reports (Anderson and Barrett, 1979, 1981; Liebeskind et al., 1979a, 1979b, 1981; Siegel et al., 1979; Miller et al., 1979) have appeared in the literature which describe ultrasonically induced biological alterations from clinical systems, a statement that has not been made relative to ionizing radiation imaging systems. A statement adopted by the American Institute of Ultrasound in Medicine (AIUM) suggests that for in vivo mammalian exposure that have been confirmed by multiple testing, that the main, diagnostic instruments operate below the levels at which biological effects occur. But an ultrasonic safety standard for diagnostic equipment, recently approved by AIUM and by a manufacturers trade organization, the National Electrical Manufacturers Association (NEMA), as a voluntary standard has recognized the fact that ultrasonic energy, even at diagnostic levels, may represent a risk to the patient (AIUM/NEMA, 1981).
Even though ultrasound as it is employed in the clinical practice of medicine is generally recognized as not representing a hazard, the studies necessary to support a reliable assessment of the risks associated with human exposure to ultrasound have not been done. With our current understanding of ultrasonically induced biological effects, it is not possible to argue against the statements such as ?diagnostic ultrasound is not harmful.? Experimental studies can not prove diagnostic ultrasound safe. Rather, what these laboratory animal studies will provide, if properly planned and executed, are data which will aid in the overall assessment of risks associated with exposure of ultrasound. Safe implies absence of an effect, not involving risk, or the like. It is simply not possible to prove that ultrasound, or for that matter an agent, does not produce any effects at the levels employed diagnostically. Also, the actual use of the word safe is vague since in medicine it almost never refers to the absence of any effect. A more useful and workable approach is to examine the ?risk? associated with ultrasonic exposure and what will be pursued in this article is risk assessment in terms of what information is provided from investigations using experimental laboratory animals.
|
| Title |
Investigations of ultrasound biological effects using laboratory animals. |
| Author |
O'Brien WD Jr. |
| Journal |
Book Chapter |
| Volume |
|
| Year |
1984 |
| Abstract |
In animal studies,attention has been given to a number of ultrasonically induced biologica effect end-points. One can think of these as being classified into one of two general categories: structured or functional alterations. A change in biological material that is determine through histologic means in considered a morphologic or structural alteration. Most ultrasonically induced structural alterations have been assessed by light microscopy. A biological effect which is assessed by a change in some biochemical level pH, or activity is considered a functional alteration. In general, relatively high ultrasonic intensity levels are required to produce a structural alteration; at lower levels, where structural alterations are not detectable, functional alterations have been observed.
In the context of a structural or functional alteration, there are various degrees to which the experimental data are conflicting. One category of boservations deals mainly with structural alterations (usually termed lesions here) of biological tissues produced by quite high levels of ultrasonic energy. Here there is no conflict in terms of whether or not a specific effect occured but there are conflicting viewpoints in terms of the fundamental mechanism or mechanisms responsible. At lower ultrasonic energy levels, usually within the therapeutic range, there are conflicting viewpoints as to whether, or to what degree, a structural alteration occured.And, for a third general category, at ultrasonic energy levels lower than the therapeutic range,sometimes at diagnostic levels, there are no indications of structural changes and there are vert conflicting data as to whether a functional alteration occured. |
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