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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 258 out of 330
| Title |
The effects of ultrasound on the fetus. |
| Author |
Carstensen EL, Gates AH. |
| Journal |
Rep Univ Rochester Dept Elect Eng |
| Volume |
|
| Year |
1983 |
| Abstract |
Recent developments suggest that transient cavitation must be considered in assessing the safety of diagnostic uses of ultrasound. An analysis of the literature on exposure of the fetus to ultrasound reveals no direct evidence that diagnostic ultrasound produces any effect on the fetus. To be very conservative, temporal peak intensities below the threshold could be used for most routine procedures. This requires knowledge of the acoustic output of the devices which are used in obstetrics. |
| Title |
The effects of ultrasound on the uptake of 8-azaguanine-2-c14 in the Krebs-2 solid tumor. |
| Author |
Ferencz N Jr. |
| Journal |
Thesis(MS): Catholic Univ of America |
| Volume |
|
| Year |
1962 |
| Abstract |
No abstract available. |
| Title |
The envelope that tissue imposes on achievable ultrasonic imaging. |
| Author |
Wells PNT, Harris RA, Halliwell M. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1992 |
| Abstract |
Ultrasonic images are imperfect because practical imaging systems have limited spatial, contrast, and temporal resolutions. The envelope within which an ultrasonic imaging system operates is imposed by the physical and biological properties of the imaged tissue. The relevant properties are speed, attenuation, inhomogeneity, nonlinearity, scattering, motion, and the induction of biological damage. The system designer begins by choosing the overall dimensions of the tissue structures to be imaged and the imaging rate. Then, optimization of system design allows the imaging performance to coincide with the envelope imposed by the characteristics of the tissue. |
| Title |
The evolution of medical ultrasound imaging systems. |
| Author |
Reid JM. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1998 |
| Abstract |
No Abstract Available. |
| Title |
The exposure vessel as a factor in ultrasonically-induced mammalian cell lysis--II. An explanation of the need to rotate exposure tubes. |
| Author |
Church CC, Flynn HG, Miller MW, Sacks PG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
This paper is an attempt to explain the need to rotate a polystyrene tube containing a cell suspension in order to obtain cell lysis. Calculations, based on known physical laws, were performed in order to determine the important forces on cells and bubbles and the movements and interactions which these forces are likely to cause. These calculations support the following conclusions: (1) in the absence of rotation, cells and bubbles larger than resonance size are trapped at pressure minima while bubbles smaller than resonance size are trapped at pressure.maxima, (2) at 1 W/cm2 with rotation, lysis is caused by cells sweeping through arrays of trapped small bubbles, (3) at higher intensities lysis is caused by both trapped and non-trapped small bubbles. |
| Title |
The exposure vessel as a factor in.ultrasonically-induced mammalian cell lysis--I. A comparison of tube and chamber systems. |
| Author |
Sacks PG, Miller MW, Church CC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
No abstract available. |
| Title |
The extracellular matrix is an important source of utlrasound backscatter from myocardium. |
| Author |
Hall CS, Scott MJ, Lanza GM, Miller JG, Wickline SA. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2000 |
| Abstract |
Ultrasound tissue characterization with measurement of backscatter has been employed in numerous experimental and clinical studies of cardiac pathology, yet the cellular components responsible for scattering from cardiac tissues have not been unequivocally identified. This laboratory has proposed a mathematical model for myocardial backscatter that postulates the fibrous extracellular matrix (ECM) as a significant determinant of backscatter. To demonstrate the importance of ECM, this group sought to determine whether measurements of backscatter from the isolated ECM could reproduce the known directional dependence, or anisotropy of backscatter, from intact cardiac tissues in vitro. Segments of left ventricular free wall from ten formalin fixed porcine hearts were insonified at 50 MHz, traversing the heart wall from endo- to epicardium to measure the anisotropy of myocardial backscatter, defined as the difference between peak (perpendicular to fibers) and trough (parallel to fibers) backscatter amplitude. The tissue segments were then treated with 10% NaOH to dissolve all of the cellular components, leaving only the intact ECM. Scanning electron micrographs (SEM) were obtained of tissue sections to reveal complete digestion of the cellular elements. The dimensions of the residual voids resulting from cell digestion were approximately the diameter of the intact myocytes (10-30 ?m). These samples were reinsonified after seven days of treatment to compare the anisotropy of integrated backscatter. The magnitude of anisotropy of backscatter changed from 15.4 +/- 0.8 to 12.6 +/- 1.1dB for intact as compared with digested specimens. Because digestion of the myocardium leaves only extracellular sources of ultrasonic scattering, and because the isolated ECM exhibits similar ultrasonic anisotropy as does the intact myocardium, it is concluded that there is a direct association between the ECM and the anisotropy of backscatter within intact tissue. Thus, it is suggested that ultrasonic tissue characterization represents a potentially clinically applicable method for delineating the structure and function of the ECM. |
| Title |
The feasibility of elastographic visualization of hifu-induced thermal lesions in soft tissues. |
| Author |
Kallel F, Stafford RJ, Price RE, Righetti R, Ophir J, Hazle JD. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1999 |
| Abstract |
The potential for visualizing high-intensity focused ultrasound (HIFU)-induced thermal lesions in biological soft tissues in vitro using elastography was investigated. Thermal lesions were created in rabbit. paraspinal skeletal muscle in vivo. The rabbits were sacrificed 60 h following the treatment and lesioned tissues were excised. The tissues were cast in a block of clear gel and elastographic images of the lesions. were acquired. Gross pathology of the tissue samples confirmed the characteristics of the lesions. |
| Title |
The feasibility of interstitial ultrasound hyperthermia. |
| Author |
Hynynen K. |
| Journal |
Med Phys |
| Volume |
|
| Year |
1992 |
| Abstract |
One of the most promising ways to increase the efficacy of brachytherapy is to combine it with hyperthermia. In this paper, the feasibility of using ultrasound transducers as interstitial hyperthermia sources was investigated. The ultrasound output of eight cylindrical transducers (diameter 1 mm and length 25 mm) was studied. It was found that many of these transducers were able to generate between 2 and 3 W of acoustic energy at the frequency of 9.5 MHz. The ultrasound field emitted radially was well collimated and extended the full length of the transducer. In vitro perfused liver and kidney experiments showed that an array of four transducers placed in brachytherapy catheters up to a maximum spacing of 20 mm in a square pattern could induce therapeutic temperatures. Also, the effect of flow rate into the organs and catheter cooling were investigated. These results showed that interstitial ultrasound sources are potentially the most promising way of generating therapeutic temperatures through standard interstitial radiation therapy catheters. |
| Title |
The feasibility of using elastography for imaging the Poisson's ratio in porous media. |
| Author |
Righetti R, Ophir J, Srinivasan S, Krouskop TA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2004 |
| Abstract |
The feasibility of using elastography for experimentally estimating and imaging the Poisson's ratio of porous media under drained and undrained conditions was investigated. Using standard elastographic procedures, static and time-sequenced poroelastograms (strain ratio images) of homogeneous cylindrical gelatin and commercially available tofu samples were generated under sustained applied axial strain. The experimental data show similar trends to those that were observed in finite-elements simulations, and to those that were calculated from classical theoretical models proposed for biphasic materials with similar mechanical properties. To demonstrate the applicability of elastography to monitor time-dependent changes in nonhomogeneous porous structures as well, preliminary time-sequenced poroelastograms were obtained from two-layer porous phantoms and porcine muscle samples in vitro. The results suggest that elastography may have significant potential for quantitatively mapping the time-dependent mechanical behavior of poroelastic media, which is related to the dynamics of fluid flow and to the elasticity and permeability parameters of the media. |
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