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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 319 out of 330
Title |
Ultrasound velocity tomography and dynamic cardiac geometry. |
Author |
Mol CR. |
Journal |
Thesis(PhD): Utrecht Univ |
Volume |
|
Year |
1954 |
Abstract |
No Abstract Available. |
Title |
Ultrasound visualization of the breast in symptomatic patients. |
Author |
Harper P, Kelly-Fry E. |
Journal |
Radiology |
Volume |
|
Year |
1980 |
Abstract |
More than 400 breast patients (primarily symptomatic) have been examined with ultrasound alone and in combination with low-dose mammography. Symptomatic pregnant women and young patients with palpable masses were examined with ultrasound alone. In young, dense breasts, ultrasound was found to surpass mammography in the differential diagnosis of both cystic and solid masses. In older patients, the tumor characteristics displayed on ultrasound augmented those of mammography, resulting in increased diagnositc accuracy. |
Title |
Ultrasound's distinctive role in breast cancer diagnosis. |
Author |
Dempsey PJ. |
Journal |
Diagn Imaging |
Volume |
|
Year |
1985 |
Abstract |
No abstract available. |
Title |
Ultrasound, cavitation bubbles and their interaction with cells. |
Author |
Wu J, Nyborg WL. |
Journal |
Adv Drug Deliv Rev |
Volume |
|
Year |
2008 |
Abstract |
This article reviews the basic physics of ultrasound generation, acoustic field, and both inertial and non-inertial acoustic cavitation in the context of localized gene and drug delivery as well as non-linear oscillation of an encapsulated microbubble and its associated microstreaming and radiation force generated by ultrasound. The ultrasound thermal and mechanical bioeffects and relevant safety issues for in vivo applications are also discussed. |
Title |
Ultrasound, contrast agents and biological cells; A simplified model for their interaction during in vitro experiments. |
Author |
Nyborg WL. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
2006 |
Abstract |
A model based on simplifying assumptions is described for the time course of an in vitro experiment in which a beam of ultrasound passes through a suspension of biological cells and gaseous contrast agents (UCAs). It is assumed that cavitation-related activation events (AEs) occur, during each of which a UCA is destroyed or becomes nonfunctional and, at the same time, nearby cells are lysed or otherwise altered. If the UCAs are highly concentrated, the ultrasound attenuation is high and may significantly affect the action. The number of cells affected by each AE depends on the concentrations of cells and UCAs as well as the concentration ratio. |
Title |
Ultrasound-an indispensable diagnostic tool for the obstetrician. |
Author |
Marsal K. |
Journal |
Ultrasound Obstet Gynecol |
Volume |
|
Year |
1992 |
Abstract |
No abstract available. |
Title |
Ultrasound-Biophysics Mechanisms |
Author |
William D. O'Brien Jr. |
Journal |
Prog in Biophys & Molec Biol |
Volume |
|
Year |
2007 |
Abstract |
Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and non-thermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials.
Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns. |
Title |
Ultrasound-biophysics mechanisms. |
Author |
O'Brien WD Jr. |
Journal |
Prog Biophys Mol Biol |
Volume |
|
Year |
2007 |
Abstract |
Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and non-thermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials. Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns. |
Title |
Ultrasound-biophysics mechanisms. |
Author |
O'Brien WD Jr. |
Journal |
Prog Biophys Molec Biol |
Volume |
|
Year |
2006 |
Abstract |
Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk studies focus on issues related to the effects of ultrasound on biological materials. On the other hand, when biological materials affect the ultrasonic wave, this can be viewed as the basis for diagnostic ultrasound. Thus, an understanding of the interaction of ultrasound with tissue provides the scientific basis for image production and risk assessment. Relative to the bioeffect or risk studies, that is, the biophysical mechanisms by which ultrasound affects biological materials, ultrasound-induced bioeffects are generally separated into thermal and non-thermal mechanisms. Ultrasonic dosimetry is concerned with the quantitative determination of ultrasonic energy interaction with biological materials.
Whenever ultrasonic energy is propagated into an attenuating material such as tissue, the amplitude of the wave decreases with distance. This attenuation is due to either absorption or scattering. Absorption is a mechanism that represents that portion of ultrasonic wave that is converted into heat, and scattering can be thought of as that portion of the wave, which changes direction. Because the medium can absorb energy to produce heat, a temperature rise may occur as long as the rate of heat production is greater than the rate of heat removal. Current interest with thermally mediated ultrasound-induced bioeffects has focused on the thermal isoeffect concept. The non-thermal mechanism that has received the most attention is acoustically generated cavitation wherein ultrasonic energy by cavitation bubbles is concentrated. Acoustic cavitation, in a broad sense, refers to ultrasonically induced bubble activity occurring in a biological material that contains pre-existing gaseous inclusions. Cavitation-related mechanisms include radiation force, microstreaming, shock waves, free radicals, microjets and strain. It is more challenging to deduce the causes of mechanical effects in tissues that do not contain gas bodies. These ultrasonic biophysics mechanisms will be discussed in the context of diagnostic ultrasound exposure risk concerns. |
Title |
Ultrasound-enhanced hydroxyl radical production from two clinically employed anti-cancer drugs, adriamycin and mitomycin C. |
Author |
Tata DB, Biglow J, Wu J, Tritton TR, Dunn F. |
Journal |
Ultrason Sonochem |
Volume |
|
Year |
1996 |
Abstract |
Continuous-wave 1 MHz ultrasound at the therapeutic intensity of 1 W cm (-2) was found to enhance significantly the hydroxyl radical production from two clinically employed redox cycling drugs, viz. adriamycin (doxorubicin) and mitomycin C, with respect to the control drug-free insonicated phosphate buffer suspension. Benzoic acid (Bz) was employed as a sensitive chemical probe to detect hydroxyl radicals (HO). Bz is initially non-fluorescent and upon aromatic hydroxylation becomes permanently fluorescent. A series of time course studies up to 30 min were performed on drug suspensions to characterize the HO generation in the presence and absence of ultrasound at 37?C. Identical ultrasound treatments on non-redox cycling clinical drugs, 5-fluorouracil and methotrexate, did not yield any significant enhancement in the production of HO in comparison to the drug-free insonicated phosphate buffer suspension. Ultrasound exposures of 30 min did not yield measurable changes in the chemical constitution of the four drugs as assessed through high-performance liquid chromatography. Identical ultrasound treatments at 3 MHz did not produce any HO in the presence or absence of these four anti-cancer drugs. Free radical scavengers such as mannitol, superoxide dismutase, catalase and a transition metal chelating agent were employed independently to elucidate the chemical species and pathways involved in the production of the HO. The findings strongly implicate an active role of acoustically induced cavitation in potentiating redox cycling drugs via chemical reduction and, thereafter, production of the OH via Fenton's pathway. |
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