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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 62 out of 330
| Title |
Changes in left ventricular wall movement after acute myocardial infarction measured by reflected ultrasound. |
| Author |
Wharton CFP, Smithen CS, Sowton E. |
| Journal |
Br Med J |
| Volume |
|
| Year |
1971 |
| Abstract |
Serial measurements of left ventricular posterior wall movement were made in eight patients with acute myocardial infarction by an ultrasound technique. Maximum posterior wall velocity and excursion were decreased during the first 36-hour period after infarction. In two patients a reduction in posterior wall velocity was associated with an increased pulmonary artery pressure and as the pressure returned towards normal the posterior wall motion also improved. It is suggested that this method provides a convenient, noninvasive bedside assessment of left ventricular function after acute myocardial infarction. |
| Title |
Changes in production, yield, and chemical composition of corn (Zea mays) after ultrasound treatments of the seeds. |
| Author |
Weinberger P, Anderson P, Donovan LS. |
| Journal |
Radiat Environ Biophys |
| Volume |
|
| Year |
1979 |
| Abstract |
In the spring of each year (1972-1974) air-dry grains of two inbred lines of Z. mays (7275-13-1 and 106) were exposed for 17 h to a low level (25 kHz) of ultrasound and subsequently planted in the field together with untreated controls and grown to.maturity. In the fall of each year the ears of each group were harvested and the number of broken stalks, the yield and weight of grains and grain parts and the alcohol-soluble amino acid complement of the grain parts were determined. Broken stalks and yields were unaffected, however the embryos from the treated groups retained more moisture than their respective controls, dry weights were also significantly increased. The alcohol-soluble amino acid composition of the embryos was markedly changed, levels of proline were severely depressed in the embryos of both lines and generally increased in the endosperms. Sonication resulted in an overall decrease of up to 40% in totalled alcohol-soluble amino acids in the grains of 7275-13-1. |
| Title |
Changes in quantitative ultrasound parameters during HIFU application |
| Author |
Ghoshal G, Kemmerer JP, Oelze ML. |
| Journal |
11th Int Symp on Therapeutic Ultrasound |
| Volume |
|
| Year |
2012 |
| Abstract |
Quantitative ultrasound (QUS) is a novel imaging technique that is hypothesized to be capable of monitoring of High Intensity Focused Ultrasound (HIFU) treatment by quantifying tissue changes during exposure. Experiments were conducted on fresh liver samples from rats and lesions were formed using a HIFU system (1-MHz, f/1.2). A wire thermocouple was inserted into the sample to monitor temperature elevation. Backscattered time domain waveforms were recorded using a clinical imaging system (Ultrasonix, L14-5 linear array) during the HIFU application and backscatter coefficients were estimated using a reference phantom technique. Two parameters were estimated from the backscatter coefficient (effective
scatterer diameter (ESD) and effective acoustic concentration (EAC)) and two parameters were estimated from the envelope statistics (k parameter and μ parameter) of the backscattered echoes. At the end of the exposure the ESD, EAC and k parameters changed in the treated region by 20%, 50% and 15% respectively, compared to the untreated region. Furthermore, changes in QUS parameters followed the shape of the temperature profile recorded by the thermocouple. These results suggest that QUS techniques could be used for noninvasive thermometry of HIFU. |
| Title |
Changes in quantitative ultrasound parameters during HIFU application. |
| Author |
Ghoshal G, Kemmerer JP, Oelze ML. |
| Journal |
AIP Conf Proc |
| Volume |
|
| Year |
2012 |
| Abstract |
Quantitative ultrasound (QUS) is a novel imaging technique that is hypothesized to be capable of monitoring of High Intensity Focused Ultrasound (HIFU) treatment by quantifying tissue changes during exposure. Experiments were conducted on fresh liver samples from rats and lesions were formed using a HIFU system (1-MHz, f/1.2). A wire thermocouple was inserted into the sample to monitor temperature elevation. Backscattered time domain waveforms were recorded using a clinical imaging system (Ultrasonix, L14-5 linear array) during the HIFU application and backscatter coefficients were estimated using a reference phantom technique. Two parameters were estimated from the backscatter coefficient (effective
scatterer diameter (ESD) and effective acoustic concentration (EAC)) and two parameters were estimated from the envelope statistics (k parameter and μ parameter) of the backscattered echoes. At the end of the exposure the ESD, EAC and k parameters changed in the treated region by 20%, 50% and 15% respectively, compared to the untreated region. Furthermore, changes in QUS parameters followed the shape of the temperature profile recorded by the thermocouple. These results suggest that QUS techniques could be used for noninvasive thermometry of HIFU. |
| Title |
Changes in surface tension of human serum albumin induced by ultrasonic cavitation and by pH-lowering. |
| Author |
Mornstein V, Hrazdira I. |
| Journal |
Studia Biophys |
| Volume |
|
| Year |
1988 |
| Abstract |
Cavitation is considered a very important acting component of the mechanism of both chemical and biological action of ultrasound. Using measurement of surface tension, which reflects the ratio between hydrophilic and hydrophobic groups in the surface region of the human serum albumin macromolecule, it has been demonstrated that the surface tension is a function of the actual value of pH without respect to the way in which the pH change was reached (by means of ultrasonic cavitation or by means of formic acid addition at three different protein concentrations). The results obtained by means of regression curve analysis have demonstrated that the pH lowering of unbuffered water-solvents caused by ultrasound can lead to alterations in the tertiary structure of the protein macromolecule and in this way to its conformational changes. This finding presents an example of a non-specific action of cavitational ultrasound on biologically important compounds. |
| Title |
Changes in the ultrastructure of bone marrow cells in rats following exposure to ultrasound. |
| Author |
Dvorak M, Hrazdira I. |
| Journal |
Z Mikrosk Anat Forsch |
| Volume |
|
| Year |
1966 |
| Abstract |
No abstract available. |
| Title |
Changes in ultrasonic attenuation and backscatter of muscle with state of contraction. |
| Author |
Glueck RM, Mottley JG, Sobel BE, Miller JG, Perez JE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
We have previously demonstrated that backscatter (uncompensated for attenuation) of canine myocardium varies systematically throughout the cardiac cycle and in relation to regional contractile performance. To elucidate these phenomena under conditions independent of blood flow and complex myofibrillar architecture, we measured attenuation with a phase-insensitive receiver and backscatter over a wide range of frequencies in an intermittently tetanized (10 stimulations), isolated frog gastrocnemius preparation (n = 12 muscles). Muscle contraction, as compared with relaxation, was associated with increased values of slope of attenuation (0.78 +/- 0.04 vs 0.58 +/- 0.03 dB/(cm MHz); p less than 0.001) and increased values of integrated backscatter (-29.5 +/- 0.9 vs -35.5 +/- 0.8 dB; p less than 0.005). Differences in attenuation and backscatter diminished with the number of muscle stimulations (as the muscle fatigued). Thus, quantitative ultrasonic indices of skeletal muscle vary systematically with the contractile performance of the tissue. Extrapolation of these results to cardiac muscle suggests that the sensitivity of these indices to contractile function of muscle may provide an approach for noninvasive assessment of intrinsic properties of myocardium that determines its performance. |
| Title |
Changes in ultrasonic attenuation indicative of early myocardial ischemic injury. |
| Author |
Mimbs JW, O'Donnell M, Miller JG, Sobel BE. |
| Journal |
Am J Physiol |
| Volume |
|
| Year |
1979 |
| Abstract |
This study was designed to determine whether quantitative alterations in ultrasonic attenuation are associated with myocardial changes occurring after acute ischemic injury. Five hundred seventeen regions of myocardium from 41 dogs were studied in vitro at five intervals after coronary occlusion: 15 min, 1 h, 6 h, 24 h, 3 days, and 6 wk. Quantitative indices of ultrasonic attenuation were determined from the measured frequency dependence of the ultrasonic attenuation coefficient characterizing each myocardial region over the range 2-10 MHz. Independent definition of regions of ischemic injury was provided by either creatine kinase depletion or colloidal carbon dye distribution. Results of this study indicate that ischemic myocardial regions investigated 15 min to 24 h after coronary occlusion demonstrated ultrasonic attenuation significantly decreased from nonischemic regions (P less than 0.05). In contrast, ultrasonic attenuation was significantly increased in zones of ischemia or infarction investigated at 3 days and 6 wk after coronary occlusion (P less than 0.05 and P less than 0.01, respectively). These results indicate that altered attenuation of transmitted ultrasound by myocardium in vitro is an early manifestation of ischemia. |
| Title |
Changes in ultrasonic attenuation indicative of regional myocardial infarction. |
| Author |
Yuhas DE,Mimbs JW,Miller JG,Weiss AN,Sobel BE. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1977 |
| Abstract |
Myocardium undergoing infarction exhibits altered structural and functional properties. It appeared likely that these changes should give rise to characteristic alterations in the ultrasonic properties of the myocardium as well. The present study comprises a series of experiments in vitro designed to measure the ultrasonic attenuation coefficient of myocardium and to assess the applicability of an ultrasonic index to characterize physical properties of myocardium associated with infarction. The quantitative index of attenuation developed is based on the frequency dependence of ultrasonic attenuation over the frequency range 2 to 10 Mhz. Ultrasonic estimates of physical properties of myocardium are compared with tissue content of creatine kinase(CK),an independent biochemical index of myocardial injury, in 38 regions of myocardium from 11 dogs sacrificed 4 to 11 weeks after coronary occlusion. |
| Title |
Changes in ultrasonic properties of liver tissue in vitro during heating-cooling cycle concomitant with thermal coagulation. |
| Author |
Choi MJ, Guntur SR, Lee JM, Paeng DG, Lee KI, Coleman A. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2011 |
| Abstract |
The present work considers the ultrasonic properties of porcine liver tissue in vitro measured during heating concomitant with thermal coagulation followed by natural cooling, so as to provide information about changes in the ultrasonic properties of the tissue after thermal coagulation. The excised liver samples were heated in a degassed water bath up to 75°C and naturally cooled down to 30°C. The tissue was observed to begin thermally coagulating at temperatures lower than 75°C. The ultrasonic parameters considered include the speed of sound, the attenuation coefficient, the backscatter coefficient and the nonlinear parameter of B/A. They were more sensitive to temperature when heating than during natural cooling. All of the parameters were shown to rise significantly on completion of the heating-cooling cycle. At 35°C after thermal coagulation, the B/A value was increased by 96%, the attenuation and backscatter coefficients were increased by 50%∼68% and 33%∼37%, respectively, in the typical frequency ranges of 3 MHz∼5 MHz used for ultrasonic imaging and the speed of sound was increased by 1.4%. The results of this study added to the evidence that tissue characterization, in particular, based on the B/A could be valuable for ultrasonically imaging the thermal lesions following high-intensity focused ultrasound (HIFU) surgery. |
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