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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 58 out of 330
| Title |
Calcium and the effects of ultrasound on frog skin. |
| Author |
Al-Karmi AM, Dinno MA, Stoltz DA, Crum LA, Matthews JC. |
| Journal |
Ultrasound Med BIol |
| Volume |
|
| Year |
1994 |
| Abstract |
Therapeutic ultrasound is used to enhance the repair of soft tissue, muscle, etc., and because many of the cellular reactions involved in these processes are dependent on the intracellular availability of free calcium ions, it becomes important to study the effects of ultrasound in the presence and the absence of calcium ions. Using frog skin as a biological model, the effect of therapeutic ultrasound (300 mW/cm2 1 MHz CW) was investigated. Sonication for two minutes caused a significantly larger increase in total ionic conductance (Gt) in the presence of calcium ions (140% vs. 27%). However, the time constant for Gt to return to steady state was significantly longer in calcium-free solutions (122 vs. 18 min.). This study demonstrates that the biological effects of ultrasound are influenced by calcium ions. Furthermore, the recovery time constants confirm recent findings regarding the function of calcium ions in the formation of tight junctions. The role of free radicals produced by cavitation and calcium potentiated lipid and protein peroxidation is discussed. |
| Title |
Calculation by the method of finite differences of the temperature distribution in layered tissues. |
| Author |
Chan AK, Sigelmann RA, Guy AW, Lehmann JF. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
1973 |
| Abstract |
A numerical approach to obtain the temperature distribution in layered tissues with thermal source and cooling inside the tissues is presented in this paper. This approach can be applied to problems with distributed internal thermal source produced by external radiation such as microwave, ultrasound, and shortwave, or by internal increase of metabolic rate in live subjects. The exact mechanism of cooling is not discussed here, but it is assumed to be due to blood flow in vivo. The calculation of the temperature distribution in layered tissues is based on a linear model of the tissues that consists of several layers different kinds of tissues separated by parallel boundaries. Some simple mathematical forms of the cooling functions are also assumed in this paper. The results obtained agree well with six available experiments. |
| Title |
Calculations of therapeutic heat generated by ultrasound in fat-muscle-bone layers. |
| Author |
Chan AK, Sigelmann RA, Guy AW. |
| Journal |
IEEE Trans Biomed Eng |
| Volume |
|
| Year |
1974 |
| Abstract |
An analytical approach to obtain the relative heating pattern due to the propagation of ultrasonic waves in a fat-muscle-bone layered tissue system is presented. The effects on the relative heating pattern due to the change of incident angle and the change of frequency are discussed in this paper. The contribution to heating due to mode conversion at the bone surface is also discussed. |
| Title |
Can pulsed ultrasound increase tissue damage during ischemia?a study of the effects of ultrasound on infarcated and non-infarcated myocardium in anaesthetized pigs. |
| Author |
Olivecrona GK,Härdig BM,Roijer A,Block M,Grins E,Persson HW,Johansson L,Olsson B. |
| Journal |
BMC Cardiovasc Disord |
| Volume |
|
| Year |
2005 |
| Abstract |
Background
The same mechanisms by which ultrasound enhances thrombolysis are described in connection with non-beneficial effects of ultrasound. The present safety study was therefore designed to explore effects of beneficial ultrasound characteristics on the infarcted and non-infarcted myocardium.
Methods
In an open chest porcine model (n = 17), myocardial infarction was induced by ligating a coronary diagonal branch. Pulsed ultrasound of frequency 1 MHz and intensity 0.1 W/cm2 (ISATA) was applied during one hour to both infarcted and non-infarcted myocardial tissue. These ultrasound characteristics are similar to those used in studies of ultrasound enhanced thrombolysis. Using blinded assessment technique, myocardial damage was rated according to histopathological criteria.
Results
Infarcted myocardium exhibited a significant increase in damage score compared to non-infarcted myocardium: 6.2 ± 2.0 vs. 4.3 ± 1.5 (mean ± standard deviation), (p = 0.004). In the infarcted myocardium, ultrasound exposure yielded a further significant increase of damage scores: 8.1 ± 1.7 vs. 6.2 ± 2.0 (p = 0.027).
Conclusion
Our results suggest an instantaneous additive effect on the ischemic damage in myocardial tissue when exposed to ultrasound of stated characteristics. The ultimate damage degree remains to be clarified.
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| Title |
Can ultrasound diagnosis be harmful? |
| Author |
Kratochwil A. |
| Journal |
Gynaek Rdsch |
| Volume |
|
| Year |
1970 |
| Abstract |
No abstract available. |
| Title |
Cancer therapy with ultrasound: A historical review. |
| Author |
Kremkau FW. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1979 |
| Abstract |
The 45-year history of research in cancer therapy involving ultrasound may be divided into the four periods of initiation, enthusiasm, pessimism and revival. There have been three approaches to the subject: studies have sought to measure the effects on tumors of a) ultrasound alone; b) ultrasound in combination with radiotherapy, and c) ultrasound in combination with chemotherapy. With the first approach the results have varied. In some cases, decreased growth rates or regressions of tumors have been reported; in other cases, either no effect has been observed or growth has been increased. With the second approach, for some tumors, combined treatment has produced greater effects on tumors than has x-ray alone, whereas in other tumors the addition of ultrasound has produced no change. With the third approach, enhancement of the effects of drugs has been observed in melanoma and mouse tumor cells treated with ultrasound and several anticancer drugs. The mechanism of action in most (but not all) cases has appeared to be absorption heating. The potential of ultrasound to provide local tumor control and to enhance other therapy modes has motivated the current efforts by several groups to further study and understand it actions on malignancies. |
| Title |
Cardiac cycle-dependent variation of integrated backscatter is not distorted by abnormal myocardial wall motion in human subjects with paradoxical septal motion. |
| Author |
Milunski MR, Canter CE, Wickline SA, Sobel BE, Miller JG, Pérez JE. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1989 |
| Abstract |
To define the dependence of cardiac cycle-dependent variation of integrated backscatter on regional myocardial wall motion, 8 children mean age 10.6 +/- 1.3 y with congenital cardiac lesions associated with paradoxical septal motion were studied (study group). Six healthy children mean age 9.0 +/- 0.3 y with no history of cardiac disease served as controls (control group). Subjects in the study group had paradoxical septal motion but normal septal wall thickening detected by conventional two-dimensional and M-mode echocardiography. The control group had normal septal motion evident by conventional echocardiographic criteria. The percentage of systolic septal thickening was 46 +/- 4.5% and 42 +/- 5.9% in the study and control groups (p = NS). Cyclic variation was measured in parasternal long-axis views from several septal sites in each subject. Mean values of the magnitude of cyclic variation from independent septal sites were averaged to yield a regional average value for each subject. The average regional magnitude of cyclic variation was 8.3 +/- 1.0 dB and 5.7 +/- 0.4 dB in the study and control groups (p = NS). The results indicate that the measurement of cyclic variation of integrated backscatter is not distorted by altered regional wall motion, and that it reflects intrinsic contractile function. |
| Title |
Cardiac imaging using a phased array ultrasound system. I. System design. |
| Author |
von Ramm OT, Thurstone FL. |
| Journal |
Circulation |
| Volume |
|
| Year |
1976 |
| Abstract |
A new two-dimensional, real-time, high resolution ultrasound imaging system is described. This system uses a linear array of ultrasound transducers to generate tomographic images of the heart in a circular sector format. Phase array techniques allow rapid steering of the ultrasound beam so that images are produced at the rate of 20 per second, or more, while maintaining a resolution of 2-4 mm throughout the field of view. |
| Title |
Cardiac imaging using a phased array ultrasound system. II. Clinical technique and application. |
| Author |
Kisslo J, von Ramm OT, Thurstone FL. |
| Journal |
Circulation |
| Volume |
|
| Year |
1976 |
| Abstract |
A new two-dimensional ultrasound imaging system capable of producing high resolution tomographic images of the heart in real time has been developed. This system relies on phased array principles to rapidly steer the ultrasound beam through the structures under investigation. A hand-held linear array of 16 ultrasound transducers with overall dimensions of 14 mm by 24 mm at the site of contact may be readily manipulated to image various cardiac structures. The resulting images are displayed in a circular sector format, 60? in azimuth and typically 15 cm in range. At this maximum range, image frames consisting of 256 lines are generated at the rate of 20 frames/second. High azimuthal resolution throughout the field of view is assured by a focused transmit beam and by sweeping the focus of the receiver in synchrony with the range of returning echoes. Azimuthal resolution varies from 2 to 4 mm throughout the field of view while range resolution is 1.5 mm. This imaging system has proven particularly useful for the delineation of left ventricular spatial geometry by the identification of endocardium, myocardium, papillary muscles and interventricular septum. High quality images of anterior and posterior mitral leaflets, aortic root and aortic leaflets as well as atrium and other cardiac structures have been obtained. |
| Title |
Cardiac reconstruction imaging in relation to.other ultrasound systems and computed.tomography. |
| Author |
Gramiak R, Waag RC. |
| Journal |
Am J Roentgenol |
| Volume |
|
| Year |
1976 |
| Abstract |
A computer-controlled system is described for the generation of two-dimensional.motion images of the heart. A standard B scanner is used to scan the area of interest.during 40-50 cardiac cycles, and the computer controls recording of the ultrasound.signals, beam position indicators, and physiologic data. The ultrasonic echoes are.reformatted by the computer into sequential frames by reference to the ECG. Images.are displayed in motion on a large monitor, and hard copy is obtained on 35 mm cine.film. Off-line computer-controlled signal processing is utilized for image.enhancement of clinical studies. Real-time systems for the production of.two-dimensional motion images of the heart are discussed and compared to computer.reconstruction of ultrasound cardiac imaging. The advantages of ultrasound imaging.of the heart and other body areas are presented, and prospectives are offered by.which the present and future roles of ultrasound can be evaluated in respect and future.roles of ultrasound can be evaluated in respect to computed tomography. It is.concluded that ultrasound will remain the primary noninvasive modality for cardiac.motion study and that ultrasound will continue to provide important clinical.information in all parts of the body where it is currently employed. |
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