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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 265 out of 330
| Title |
The risk of exposure to diagnostic ultrasound in postnatal subjects: Thermal effects. |
| Author |
O'Brien WD Jr, Deng CX, Harris GR, Herman BA, Merritt CR, Sanghvi N, Zachary JF. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2008 |
| Abstract |
This review evaluates the thermal mechanism for ultrasound-induced biological effects in postnatal subjects. The focus is the evaluation of damage versus temperature increase. A view of ultrasound-induced temperature increase is presented, based on thermodynamic Arrhenius analyses. The hyperthermia and other literature revealed data that allowed for an estimate of a temperature increase threshold of tissue damage for very short exposure times. This evaluation yielded an exposure time extension of the 1997 American Institute of Ultrasound in Medicine Conclusions Regarding Heat statement (American Institute of Ultrasound in Medicine, Laurel, MD) to 0.1 second for nonfetal tissue, where, at this exposure time, the temperature increase threshold of tissue damage was estimated to be about 18 degrees C. The output display standard was also evaluated for soft tissue and bone cases, and it was concluded that the current thermal indices could be improved to reduce the deviations and scatter of computed maximum temperature rises. |
| Title |
The risk of exposure to diagnostic ultrasound in postnatal subjects: thermal effects. |
| Author |
O'Brien WD Jr, Deng CX, Harris GR, Herman BA, Merritt CR, Sanghvi N, Zachary JF. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2008 |
| Abstract |
This review evaluates the thermal mechanism for ultrasound-induced biological effects in postnatal subjects. The focus is the evaluation of damage versus temperature increase. A view of ultrasound-induced temperature increase is presented, based on thermodynamic Arrhenius analyses. The hyperthermia and other literature revealed data that allowed for an estimate of a temperature increase threshold of tissue damage for very short exposure times. This evaluation yielded an exposure time extension of the 1997 American Institute of Ultrasound in Medicine Conclusions Regarding Heat statement (American Institute of Ultrasound in Medicine, Laurel, MD) to 0.1 second for nonfetal tissue, where, at this exposure time, the temperature increase threshold of tissue damage was estimated to be about 18 degrees C. The output display standard was also evaluated for soft tissue and bone cases, and it was concluded that the current thermal indices could be improved to reduce the deviations and scatter of computed maximum temperature rises. |
| Title |
The role of cavitation in the in vitro stimulation of protein synthesis in human fibroblasts by ultrasound. |
| Author |
Webster DF, Pond JB, Dyson M, Harvey W. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1978 |
| Abstract |
The synthesis of protein by human embryonic fibroblasts in vitro was stimulated by irradiation with ultrasound at a frequency of 3 MHz, a spatial and temporal peak intensity of 0.5 W.cm−2, pulsed at a mark: space ratio of 2:8 ms for 5 min at ambient pressure. This stimulation was suppressed by the application of a positive pressure of two atmospheres during irradiation, although increasing the pressure in the absence of ultrasound had no significant effect on the rate of protein synthesis in control cells. Dilatation of the rough endoplasmic reticulum and plasma membrane changes, found in the majority of cells after treatment with ultrasound at ambient pressure, were also suppressed in cells irradiated at elevated pressure. Since it is unlikely that increasing the pressure could modify any ultrasonic effect other than cavitation, these results suggest that cavitation is involved in the mechanism of stimulation. |
| Title |
The role of cavitation in the interaction of ultrasound with V79 Chinese hamster cells in vitro. |
| Author |
Morton KI, ter Haar GR, Stratford IJ, Hill CR. |
| Journal |
Br J Cancer Suppl |
| Volume |
|
| Year |
1982 |
| Abstract |
Suspensions of V79 cells have been irradiated with 1 MHz ultrasound at spatial average intensities up to 0.25 W cm-2. The effects seen are described in this paper. Acoustic emissions at the first subharmonic of the drive frequency (0.5 MHz) were monitored during irradiation. Subharmonic emission is characteristic of cavitation activity within the sample. A strong correlation was found between cell damage and a measure of the total emitted subharmonic energy. Damage was assayed in terms of cell lysis, the ability of the cells to take up the vital dye trypan blue and loss of reproductive integrity. It is concluded from these data that cavitation can play an important part in the interaction of ultrasound with biological systems in vitro, and that subharmonic emission may provide a non-invasive and somewhat quantitative means of predicting the magnitude of such interactions. |
| Title |
The role of computers in ultrasound cancer diagnosis - velocity measurements techniques. |
| Author |
Kossoff G. |
| Journal |
Proc First Int Symp Ultrasound Cancer - Brussels |
| Volume |
|
| Year |
1982 |
| Abstract |
No abstract available. |
| Title |
The role of inertial cavitation of ultrasound constrast agents in producing sonoporation. |
| Author |
Forbes MM. O’Brien WD Jr. |
| Journal |
Proc IEEE Ultrasonic Symposium |
| Volume |
|
| Year |
2007 |
| Abstract |
The objective of this project is to elucidate the relationship between ultrasound contrast agents (UCA) and sonoporation by varying the peak rarefactional pressure (Pr) in a threshold type study. The results of sonoporation in the presence
of OptisonTM or Definity® are directly compared to the collapse thresholds of the respective contrast agent to uncover the role inertial cavitation plays in sonoporation. Chinese Hamster Ovarian (CHO) cells were grown as a monolayer in a 96-microwell plate. Each well was filled with an exposure medium consisting of 0.05 mL Fluorescein isothiocyanate-dextran (FITCdextran),8.8 μL OptisonTM or 0.57 μL Definity®, and Phosphate Buffered Saline. CHO cells were exposed for 30 s to pulsed ultrasound at 3 MHz center frequency, 5-cycle pulse duration,and 10-Hz pulse repetition frequency. Pr was varied over a range from 10 kPa to 3.5 MPa. Flow cytometery was used to determine the percentage of positively labeled cells. Over the Pr range applied, the sonoporated cells in the presence of OptisonTM
increased from 0.63% to 10.21%, with a maximum occurring at 2.4 MPa. Above 2.4 MPa, a significant drop in sonoporation activity was observed. Sonoporation in the presence of Definity® presented the same trend, with sonoporated cells increasing from 5.26% to 26.39%, with a maximum occurring 172 kPa. Above
172 kPa, a drop in sonoporation activity was observed. These results illustrate that sonoporation is not due inertial cavitation of the UCA. Instead the evidence directly suggests that the sonoporation effect was caused by linear and/or nonlinear oscillation of the UCA, as these responses occur at lower Pr where
sonoporation activity was present. Moreover, at higher pressures, the UCAs are rapidly collapsing and as such, are likely not present for enough time to significantly oscillate, thus minimal sonoporation activity was observed. |
| Title |
The role of inertial cavitation of ultrasound contrast agents in producing sonoporation. |
| Author |
Forbes MM, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
2008 |
| Abstract |
The objective of this project is to elucidate the
relationship between ultrasound contrast agents (UCA) and
sonoporation by varying the peak rarefactional pressure (Pr) in a
threshold type study. The results of sonoporation in the presence
of OptisonTM or Definity® are directly compared to the collapse
thresholds of the respective contrast agent to uncover the role
inertial cavitation plays in sonoporation. Chinese Hamster
Ovarian (CHO) cells were grown as a monolayer in a 96-
microwell plate. Each well was filled with an exposure medium
consisting of 0.05 mL Fluorescein isothiocyanate-dextran (FITCdextran),
8.8 µL OptisonTM or 0.57 µL Definity®, and Phosphate
Buffered Saline. CHO cells were exposed for 30 s to pulsed
ultrasound at 3 MHz center frequency, 5-cycle pulse duration,
and 10-Hz pulse repetition frequency. Pr was varied over a range
from 10 kPa to 3.5 MPa. Flow cytometery was used to determine
the percentage of positively labeled cells. Over the Pr range
applied, the sonoporated cells in the presence of OptisonTM
increased from 0.63% to 10.21%, with a maximum occurring at
2.4 MPa. Above 2.4 MPa, a significant drop in sonoporation
activity was observed. Sonoporation in the presence of Definity®
presented the same trend, with sonoporated cells increasing from
5.26% to 26.39%, with a maximum occurring 172 kPa. Above
172 kPa, a drop in sonoporation activity was observed. These
results illustrate that sonoporation is not due inertial cavitation of
the UCA. Instead the evidence directly suggests that the
sonoporation effect was caused by linear and/or nonlinear
oscillation of the UCA, as these responses occur at lower Pr where
sonoporation activity was present. Moreover, at higher
pressures, the UCAs are rapidly collapsing and as such, are likely
not present for enough time to significantly oscillate, thus
minimal sonoporation activity was observed. |
| Title |
The role of microstreaming in ultrasound-enhanced thrombolysis. |
| Author |
Hafez Z. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
2008 |
| Abstract |
The purpose of this thesis is to examine how the mechanism of microstreaming
affects ultrasound-enhanced thrombolysis. These small gas bodies, when oscillating,displace small amounts of the media surrounding them, creating rapidly moving streams around the surfaces. These small, rapidly moving streams are termed microstreams. It has been proposed that the main contributor to the thrombolytic effect of ultrasound lies in the shear stresses that oscillations of gas bubbles create. |
| Title |
The role of molecular weight and structure in the absorption of ultrasound by proteins. |
| Author |
Kremkau FW, Cowgill RW. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1984 |
| Abstract |
We have measured absorption coefficients in the 10-100 MHz range for 10 sugars, 3 polysaccharides, 5 amino acids, 2 amino acid mixtures, 15 proteins, 7 denatured proteins, and 2 depolymerized proteins. Analyses of the resulting data indicate that absorption increases in these molecules with increasing molecular weight only in a threshold sense, with absorption increasing significantly only in a restricted molecular weight range. Secondly, the data indicate that absorption in globular proteins is insensitive to structural characteristics while in linear proteins it is dependent upon the amount of alpha-helix content. |
| Title |
The role of non-thermal mechanisms in the interaction of ultrasound with biological systems. |
| Author |
Morton KI. |
| Journal |
Thesis(PhD): Univ of London |
| Volume |
|
| Year |
1982 |
| Abstract |
No abstract available. |
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