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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 307 out of 330
| Title |
Ultrasound does not affect human lymphocyte transformation in vitro.. |
| Author |
Katoh AK, Charoensiri S. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1983 |
| Abstract |
The lymphocyte transformation test has been used in testing the effect of ultrasound on human lymphocytes. The test utilizes the mitogenic lectins, phytohemagglutinin, concanavalin A, and pokeweed mitogen to stimulate the incorporation of 3H-thymidine into resting lymphocytes after several days in culture. Ultrasound, which is increasingly used in diagnostic radiology, has been reported as an immunosuppressive agent in mice. Lymphocyte transformation has been used.clinically as a test measuring the effectiveness of immunoenhancing and immunosuppressive therapies. The experiments reported here do not demonstrate an immunosuppressive role for ultrasound on human lymphocytes. |
| Title |
Ultrasound dosage for experimental use on human beings. |
| Author |
Ulrich WD. |
| Journal |
Rep Nav Med Res Inst |
| Volume |
|
| Year |
1971 |
| Abstract |
A schedule of safe ultrasound dosage for experimental use on normal human beings was formulated from available literature. The zone of safety for continuous wave ultrasound lay below a log/log line connecting 1 ?sec of 1 kw/cm(2) ultrasound with 200 seconds of 100 mw/cm(2) ultrasound. An ultrasonic intensity of 100 mw/cm(2) or less was also safe for at least 10,000 seconds. Pulsed wave ultrasound was safe for doses in which the average intensity multiplied by the total exposure time lay within this zone of safety. The zone of safety was valid for 0.5 to 15 MHz and for all anatomic sites except the eyes. Re-exposures were limited to 10 per month and 30 per year. |
| Title |
Ultrasound dosage for non-therapeutic use on human beings - extrapolations from a literature survey. |
| Author |
Ulrich WD. |
| Journal |
Rep Nav Med Res Inst |
| Volume |
|
| Year |
1972 |
| Abstract |
A practical method for analyzing the biological effects of non-therapeutic ultrasound was applied to the data of 21 different principal investigators. The data were compiled so that individual investigators could develop tentative guidelines of their own regarding the hazards of diagnostic ultrasound in human beings. One set of guidelines developed by the author suggested that exposures of minimal hazard lie below a log/log line connecting 100 ?sec of 100 W/cm(^2) ultrasound with 200 seconds of 100 mW/cm(^2) ultrasound. An ultrasonic intensity of 100 mW/cm(^2) or less was of little or no hazard for at least 10,000 seconds. These guidelines applied to both continuous and pulsed wave ultrasound doses that were described by average intensity multiplied by total exposure time. The proposed schedule was valid for 0.5-15 MHz and for all anatomic sites except the eyes. |
| Title |
Ultrasound echo envelope analysis using a homodyned Κ distribution signal model. |
| Author |
Dutt V,Greenleaf JF. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1994 |
| Abstract |
The statistics of ultrasound echo envelope signals can be used to characterize scattering media. The Rayleigh distribution and its generalized forms, the Κ and Rice distributions, have been previously used to model the echo signal. A more generalized statistical model, the homodyned Κ distribution, combines the Κ and Rice distribution features to better account for the statistics of the echo signal. We show that this model can give two parameters that are useful for media characterization: κ, the ratio of coherent to diffuse signals, and,β, which characterizes the clustering of scatters in the medium.©1994 Academic Press Inc.
Key words: Echo envelope statistics modeling; homodyned Κ distribution. |
| Title |
Ultrasound echo patterns from normal human and animal liver relation to detection of pathological states of liver. |
| Author |
Fry EK, Eggleton RC, Fry FJ. |
| Journal |
Proc 16th Intern Meeting Am Inst of Ultrasound Med |
| Volume |
|
| Year |
1970 |
| Abstract |
No abstract available. |
| Title |
Ultrasound effects on fetal auditory brain stem responses. |
| Author |
Siddiqi TA, Meyer RA, Woods JR Jr, Plessinger MA. |
| Journal |
Obstet Gynecol |
| Volume |
|
| Year |
1988 |
| Abstract |
The use of diagnostic ultrasound raises questions regarding its bioeffects upon fetal auditory function. This study was designed to determine whether ultrasound produces changes in the auditory brain stem response in fetal lambs. Near-term fetal lambs were chronically instrumented with electroencephalogram electrodes at the vertex and the right mastoid region. An earphone was secured in the fetal right external ear canal for auditory stimulation. An ATL mechanical sector scanner was used for all ultrasound studies at a spatial peak, temporal average intensity of 15.5 mW/cm2. Auditory brain stem responses were recorded at five and 15 minutes during pulsed-wave ultrasound exposure of the cranium and then 30 minutes after cessation of insonation. Sham experiments (without insonation) were then performed in a similar time sequence to rule out the effects of habituation. There was a consistent decrease in the mean amplitude and a consistent increase in the mean latency of all five wave deflections of the auditory brain stem response during insonation. These changes persisted for 30 minutes following cessation of insonation, after which auditory brain stem response amplitude and latency values returned toward control values. No changes in auditory brain stem response amplitude or latency were observed during sham experiments. We conclude that direct ultrasound exposure of the fetal cranium through the maternal abdominal wall may temporarily influence nerve conduction along central nervous system axonal pathways. This transient influence is reversible, with all values approaching baseline within 30 minutes. |
| Title |
Ultrasound elasticity measurements of beef muscle. |
| Author |
Chen EJ, Novakofski J, Jenkins K, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1994 |
| Abstract |
The goal of this work is to provide a quantitative comparison between ultrasound and mechanical techniques for measuring tissue elasticity. The biomechanical response of beef muscle and tissue mimicking gel to uniaxial compression are characterized with ultrasound derived stress-strain curves. Ultrasound estimates of the Young's modulus of elasticity for samples are computed from the slope of the initial linear region of sample stress-strain curves. Elasticity of tissue samples was independently determined from force-deformation measurements made with an Instron universal testing load cell device. Results from in vitro ultrasound elasticity measurements of beef muscle are presented. Ultrasonic elasticity measurements showed an overall 0.72 correlation with load cell measurements for tissue strains less than 2%. To our knowledge, these are the first reported comparisons between ultrasound tissue elasticity measurements and independent mechanical elasticity measurements. |
| Title |
Ultrasound elastography based on multiscale estimations of regularized displacement fields. |
| Author |
Pellot-Barakat C, Frouin F, Insana MF, Herment A. |
| Journal |
IEEE Trans Med Imaging |
| Volume |
|
| Year |
2004 |
| Abstract |
Elasticity imaging is based on the measurements of local tissue deformation. The approach to ultrasound elasticity imaging presented in this paper relies on the estimation of dense displacement fields by a coarse-to-fine minimization of an energy function that combines constraints of conservation of echo amplitude and displacement field continuity. The multiscale optimization scheme presents several characteristics aimed at improving and accelerating the convergence of the minimization process. This includes the nonregularized initialization at the coarsest resolution and the use of adaptive configuration spaces. Parameters of the energy model and optimization were adjusted using data obtained from a tissue-like phantom material. Elasticity images from normal in vivo breast tissue were subsequently obtained with these parameters. Introducing a smoothness constraint into motion field estimation helped solve ambiguities due to incoherent motion, leading to elastograms less degraded by decorrelation noise than the ones obtained from correlation-based techniques. |
| Title |
Ultrasound enhanced drug toxicity on Chinese hamster ovary cells in vitro. |
| Author |
Saad AH, Hahn GM. |
| Journal |
Cancer Res |
| Volume |
|
| Year |
1989 |
| Abstract |
Chinese hamster ovary cells (HA1) were exposed to therapeutic ultrasound (F=2.025 MHz) in the presence of various drugs at temperatures of 37-43?C. The space averaged intensities used were 0.5-2 W/cm(2). The survival of these cells was subsequently tested using the clonogenic assay. Marked enhancement by ultrasound of the cytotoxicity of Adriamycin and amphotericin B was observed. For Adriamycin, the potentiation was dependent upon the intensity of sonication (exposure duration being 30 min.). At 0.5 W/cm(2), there was enhancement of cytotoxicity above 41?C. At 1 W/cm(2), there was a 3-order increase in cytotoxicity at 37?C. Thus an increase in intensity resulted in a decrease in ?threshold? temperature. The effect with Adriamycin could be explained in part by an increase in net uptake of drug into the cells. Further, ultrasound was observed to increase the sensitivity of cells to Adriamycin. For amphotericin B, the enhancement was observed only at exposure durations >30 min and at 43?C. There was no enhancement observed for cisplatin and etoposide. From these results, it appears that ultrasound potentiates the cytotoxicity of drugs the mode of action of which (at least in part) involves the plasma membrane. |
| Title |
Ultrasound enhancement of liposome-mediated cell transfection is caused by cavitation effects. |
| Author |
Koch S,Pohl P,Cobet U,Rainov NG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2000 |
| Abstract |
Cationic liposomes (CL) are widely used vectors for gene transfer. Recently, ultrasound (US) was reported to enhance liposome-mediated gene transfer to eucaryotic cells in culture. The present study was aimed at studying the effects of 2-MHz pulsed Doppler US on malignant brain tumor cells transfection by cationic liposome/plasmid-DNA complexes (lipoplexes). Cationic liposomes consisting of DOSPA/DOPE were complexed with a plasmid carrying the cDNA encoding green autofluorescent protein (EGFP). Rodent (9L) and canine (J3T) glioma cells were exposed to pulsed US in the presence of EGFP-lipoplexes. A diagnostic transcranial Doppler device (MultiDop L) was used for insonation for 30, 60, and 90 s at 2 MHz/0.5 W/cm2. To eliminate US reflection and cavitation, a custom-made absorption chamber was designed, where US is applied through a water tank before interacting with the cells and is fully absorbed after passing through the cell layer. Expression of the marker gene EGFP was quantified by FACS analysis and intravital fluorescent microscopy. Cell viability was accessed by Trypan Blue staining. US treatment of tumor cells on microplates for 60 s yielded a significant increase in transfection rates without damaging the cells, but 90-s treatment killed most of the cells. In the absorption chamber, no significant effects of US on transfection were noted. Additional experiments employed US contrast agent (Levovist®, Schering) which was able to significantly increase tumor cell transfection rate by enhancing cavitation effects, and also severely damaged most cells when applied at a concentration of 200 mg/mL. In conclusion, our results support the assumption that US effects on lipoplex transfection rates in brain tumor cells in culture are mediated by cavitation effects. |
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