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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 285 out of 330
| Title |
Ultrasonic absorption by solvent-solute interactions and proton transfer in aqueous solutions of peptides and small proteins. |
| Author |
Strom-Jensen PR, Dunn F. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1984 |
| Abstract |
Ultrasonic absorption values in aqueous solutions of myoglobin, apomyoglobin, alpha-lactalbumin, bacitracin, and the C- and N-terminal CNBr cleavage fragments of myoglobin were determined by the cylindrical resonator technique at temperatures of 4 ?C and 20 ?C in the frequency range 0.5-7 MHz. A proposed mechanism of absorption in solutions of proteins and peptides is perturbation by the ultrasound of the equilibrium between protein bound and free water, producing a distribution of relaxation processes occurring within the frequency range of the investigation. The hypothesis is supported by the dependence of the ultrasonic absorption on solute surface area and molecular weight. Another mechanism of absorption is that due to proton transfer which occurs noticeably in the presence of phosphate ions. Those proteins (myoglobin and alpha-lactalbumin) with significant globular structure appear to undergo additional relaxation processes at frequencies above 7 MHz. |
| Title |
Ultrasonic absorption frequency dependence of two widely used anti-cancer drugs: Doxorubicin and daunorubicin. |
| Author |
Tata DB, Hahn G, Dunn F. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1993 |
| Abstract |
Low intensity ultrasound (approximately 10(-6) W cm-2) in the frequency range 0.5-6.0 MHz was employed to investigate the ultrasound absorption properties of doxorubicin (DOX) at several temperatures. At physiological temperatures, we found enhanced ultrasound absorption from DOX, and its closely related analogue daunorubicin (DNR), in the upper kilohertz frequency range. The findings do not conform to classical theory of ultrasound absorption, thus suggesting an ultrasound coupling with the drug molecules via structural and/or chemical relaxation processes. The absorption spectra are analysed from the point of view of the non-classical theory of sound absorption due to physical and/or chemical relaxations. Only one spectral difference between the two anti-cancer agents is observed, around 2 MHz, and may be attributed to the sole difference in the chemical make-up of the side chain of the two antibiotics. |
| Title |
Ultrasonic absorption in aqueous suspensions of small elastic particles. |
| Author |
Hawley SA. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1967 |
| Abstract |
The absorption of ultrasound has been measured in aqueous solutions of dextran, a quasi-linear anhydroglucose polymer, and in aqueous suspensions of small polystyrene particles over the frequency range 3 ? 165 MHz. The absorption in dextran solutions has been found to be independent of molecular weight (10 to the 4 < Mw<3.7 x10 to the 5) and substantially greater than would be anticipated from the dynamic shear viscosity contributions predicted on the basis of the Rouse theory. The absorption in aqueous polystyrene lattices has been measured in five suspensions with particle sizes ranging from 0.044 micron to 3.5 microns. Comparison of the absorption behavior to the Lamb-Urick-Epstein theory and to results obtained in bulk polystyrene reveal that neither relative motion nor internal viscosity of the particle contribute substantially to the observed acoustic attenuation. An Arrhenius dependence of absorption coefficient on temperature is observed in the lattices that indicates that dissipation of ultrasound is intimately associated with the liquid phase of the suspension. Comparison of the absorption properties of the lattices to that observed to that found in solutions of bovine serum albumin and hemoglobin suggests that the absorption mechanisms may be similar. |
| Title |
Ultrasonic absorption in soft and hard fetal tissues. |
| Author |
Drewniak JL. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1991 |
| Abstract |
Although the use of ultrasound as a diagnostic modality in obstetrics has become ubiquitous, concern that harmful effects may occur under special circumstances continues. A physical mechanism by which biological effects could occur is the deposition of heat in the tissue as a result of the energy absorbed from the acoustic wave. Because the teratogenicity of hyperthermia has been well-established and concerns of more subtle effects of elevated fetal temperature exist, there is currently a concerted effort to provide manufacturers of medical diagnostic ultrasound instrumentation and clinicians with guidelines for the use of ultrasound during pregnancy. The temperature elevation in fetal soft tissue is estimated analytically from simple heat transfer models and simple assumptions concerning the ultrasound propagation and beam. Experimental animal studies exist to support the calculations. There is a need, however, to continue developing heat transfer models that that better reflect the actual problem, such that more accurate estimates of the temperature elevation upon exposure to ultrasound can be made. Included in such models would be the absorption properties of fetal soft tissue and fetal bone as a function of gestational age. The absorption of ultrasound in fetal tissues and the resulting temperature elevation are studied in this thesis. The temperature elevation in fetal mice exposed to 1 MHz ultrasound is measured, and the results are compared with analytical values of the temperature increase that are calculated using a simple heat transfer model. The transient thermoelectric method for measuring the absorption coefficient of liquids and soft tissues is also analyzed. The results provide an experimental guide for more accurate measurements of the absorption coefficient in fetal soft tissue. Finally, the absorption in fetal bone as a function of gestational age is considered. The acoustic propagation properties in bone are as yet unknown. The velocity and absorption are expected to b a function of the mode and direction of propagation because of the anisotropy of the bone. In the absence of specific knowledge regarding the acoustic properties of fetal bone, from which the temperature increase might be caluclated, the temperature rise resulting from exposure to ultrasound can be measured. The temperature elevation in fetal bone exposed to 1MHz ultrasound is measured for a range of gestational ages. An equivalent heat source obtained from the measurements, which might be used in numerical and analytical calculations, is given. |
| Title |
Ultrasonic absorption in the human breast cyst liquids. |
| Author |
Lang J, Zana R, Gairard B, Dale G, Gros CM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1978 |
| Abstract |
The ultrasonic absorption of samples of cyst liquids (CL) of the human breast has been measured as a function of frequency (1.67 - 115 MHz), pH (1-13), dilution and temperature (25 and 37 C). The absorption behavior of these liquids is very similar to that of protein solutions. It is shown that the absorption of CL at physiological pH arises essentially from the protein contained in these liquids and, in fact, can be evaluated to within a factor 1.5, from that of serum albumin in similar condition. The origin of this absorption is discussed. |
| Title |
Ultrasonic analysis of edible fats and oils. |
| Author |
McClements DJ, Povey MJ. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1992 |
| Abstract |
Low intensity ultrasound is a powerful analytical technique for investigating the physico-chemical properties of many biological and.non-biological materials. In this article its application for the characterization of edible fats and oils is assessed. Ultrasound can be.used to determine the dynamic rheology and composition of oils, the oil content and droplet size of emulsions and the solid fat content.of partially crystalline emulsions. It is capable of rapid and precise measurements, is non-destructive and non-invasive, can be used.on-line or off-line and is relatively inexpensive. Ultrasonic techniques will therefore prove a useful addition to the existing analytical.techniques used to characterize fats and oils. |
| Title |
Ultrasonic and histopathological correlations of deep focal hepatic lesions induced by stereotaxic Nd-YAG laser applications. |
| Author |
Godlewski G, Bourgeois JM, Sambuc P, Gouze C, Ould-Said H, Eledjam JJ, Rouy S, Pignodel C. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
Thirty six deep focal hepatic lesions were induced in eleven piglets by means of an Nd-YAG laser. Laser shots of 80 W power and 10 s duration were used, the beam being transmitted through an echoguided stereotaxic handpiece. From day 0 to day 120, the animals underwent ultrasonographic and morphological controls. At lasering time an hyperechoic image--12-18 mm in diameter--appeared due to boiling of tissue water. During the twenty postoperative days the lesion core was an echo-free area due to tissue vaporization, surrounded by an hyperechoic ring of increasing fibrosis, containing neovascularization and biliary ductules, while the hypoechoic outer area represented the peripheral halo of edema. In the long term, hyperechoic structures--swollen fibrotic septa of homogeneous fibrotic network--invaded the lesion site confirming good healing. .. |
| Title |
Ultrasonic assessment of skin and wounds with the scanning laser acoustic microscope. |
| Author |
Olerud JE, O'Brien WD Jr, Riederer-Henderson MA, Steiger D, Forster FK, Daly C, Ketterer DJ, Odland GF. |
| Journal |
J Invest Dermatol |
| Volume |
|
| Year |
1987 |
| Abstract |
The aim of the present study was to test the hypothesis that ultrasonic propagation properties in skin and wound tissue would correlate with material properties such as collagen content, water content, and tensile strength of those tissues. Both ultrasonic speed and ultrasonic attenuation coefficient were directly correlated with tissue collagen content, [r = 0.80 and r = 0.56, respectively (p<0.001]. In addition, ultrasonic speed and attenuation coefficient were inversely correlated with tissue water content, [r = -.057 and r = -0.73, respectively (p<0.001)]. Tensile strength also correlated very significantly with ultrasonic speed (r = 0.09, p<0.001), and significantly with attenuation coefficient (r = 0.58, p<0.001). The results demonstrate the feasibility of using ultrasound for noninvasively determining the material properties of biologic tissues including healing cutaneous wounds. |
| Title |
Ultrasonic assessment of thermal therapy in rat liver. |
| Author |
Kemmerer JP, Oelze ML. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2012 |
| Abstract |
One way to assess the efficacy of thermal therapy is to quantify changes in tissue properties through ultrasonic interrogation, which requires knowledge of the acoustic properties of thermally treated tissues. In this study, estimates of ultrasonic attenuation, speed of sound, backscatter coefficient (BSC), and scattering property estimates were generated from rat liver samples submersed for 10 minutes in a saline bath that was heated to one of seven temperature values over a range of 37–70C. The attenuation coefficient increased monotonically with
exposure temperature, with a maximum increase of 90%. Speed of sound changed by ,1% for the different treatment conditions. The BSC had close agreement for all thermal doses over the frequency range of 8–15 MHz. Above this frequency range, samples heated $55C demonstrated an increased BSC slope, and the effective scatterer diameter and effective acoustic concentration were able to distinguish treated from nontreated cases. The findings suggest that attenuation and either BSCs or scatterer property estimates above 15 MHz were sensitive to tissue
changes in excised liver caused by thermal therapy. (E-mail: kemmere1@illinois.edu) Published by Elsevier Inc. on behalf of World Federation for Ultrasound in Medicine & Biology. |
| Title |
Ultrasonic attentuation and backscattering by mammalian organs as a function of time after excision. |
| Author |
Bamber JC, Fry MJ, Hill CR, Dunn F. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1977 |
| Abstract |
Ultrasonic attenuation and backscattering were measured for bovine brain, spleen and liver and for porcine liver as a function of time after excision for times up to 120 hr. The attentuation coefficient exhibits insignificant changes while the mean backscattering amplitude decreases substantially during the period such specimens are likely to be used. The changes in the two parameters are believed to reflect, in large measure, their origins, viz., the molecular level for attentuation and macrostructural level for backscattering. |
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