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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 148 out of 330
| Title |
In vitro estimation of acoustic parameters of the liver and correlations with histology. |
| Author |
Cloostermans MJ, Mol H, Verhoef WA, Thijssen JM, Kubat K. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1986 |
| Abstract |
Freshly excised human liver specimens (77) were investigated echographically and histologically. The echography was concerned with the acoustic parameters: speed of sound, impedance, several attenuation parameters, and the texture parameters: reflectivity and the signal to noise ratio. It was found that the speed and impedance, the attenuation parameters, and the texture parameters did not correlate with each other. The major correlation between histologic parameters was found for the focal collagen content to the parenchymal content (r = -0.72). The most important correlations of the acoustic parameters to the histologic ones were: attenuation slope to the focal collagen content (r = +0.63) and the reflectivity to the water content (r = -0.55). The most significantly separating acoustic parameters in the comparison of normal livers from focal tumours were found to be the speed, the attenuation slope, the reflectivity, and the signal to noise ratio. A Fisher discriminant analysis revealed a specificity of 91% and a sensitivity of 83% of the separation of tumours from normals when the speed of sound and two parameters of the frequency dependence of the attenuation were considered. |
| Title |
In vitro gray scale echography of protein-lipid fluid collections in liver tissue. |
| Author |
Cunningham JJ. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1976 |
| Abstract |
Three types of protein-lipid fluid collections--homogenized milk, buttermilk, and yogurt--were studied in liver tissue by in vitro gray scale echography. These fluid collections are capable of producing internal echoes, dampened sound transmission, partial acoustic "shadows", and ill-defined interfaces with hepatic parenchyma. Such effects may preclude universal detection of purulent hepatic abscesses when they contain similar types of substances. |
| Title |
In vitro high resolution intravascular imaging in muscular and elastic arteries. |
| Author |
Lockwood GR, Ryan LK, Gotlieb AI, Lonn E, Hunt JW, Liu P, Foster FS. |
| Journal |
J Am Coll Cardiol |
| Volume |
|
| Year |
1992 |
| Abstract |
High resolution (125-microns lateral, 55-microns axial) images of 16 muscular (femoral) and 15 elastic (common carotid) human arteries were made in vitro with use of a prototype 45-MHz intravascular imaging system. Four distinct regions of scattering, excluding plaque, were identified in the ultrasound images corresponding histologically to the adventitia, media, thickened intima and elastic laminae, both internal and external. Arterial samples imaged under pressure and in a collapsed state underwent dimensional changes but exhibited similar levels of backscatter amplitude. All the elastic arteries displayed a prominent echogenic media, whereas all the muscular arteries displayed an echolucent media. Scattering from the internal elastic lamina in muscular arteries provided an excellent landmark for defining the location and extent of intimal thickening or plaque. In elastic arteries the internal elastic lamina could not be distinguished from the echogenic media; consequently, the boundary between the media and intimal layer was indistinct. Differences in the relative concentration and organization of collagen and elastin were found to provide a consistent explanation for the differences in scattering that were observed between individual layers within an artery as well as between muscular and elastic arteries. .. |
| Title |
in vitro investigation of the effect of ultrasound on gallstones in low lithogenic ursdeoxycholate enriched synthetic bile. |
| Author |
Sheets PW,Chua RC,Griffith SL,Fry FJ,Franklin TD Jr. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1990 |
| Abstract |
It has been previously demonstrated that therapeutic ultrasound can potentiate gallstone dissolution by solvents. This study's objective was to establish the effect of 220 kHz ultrasound on gallstone or stone fragment dissolution in low lithogenic bile. Two families of cholesterol gallstones were divided into 4 distinct groups: 1) single intact stones weighing 554.4+/- 34.6 mg(n=5); 2) multiple intact stones with cumulative weight of 534.6 +/- 51.9 mg(n=5); 3)multiple stone fragments weighing 559.6 +/- 28.6mg (n=5); and 4) single fragments weighing 63.8 +/- 18.2 mg (n=5). Each experimental group was placed in a latex finger cot filled with synthetic bile, which mimics human bile from a patient taking oral ursodeoxycholate therapy, and insonated with 18 W/cm2 (SPTP) delivered in a burst mode for 65 minutes. Weighings were performed every 13 minutes (equivalent to 2 minutes of ultrasound).
A measurable weight loss was achieved in all groups when ultrasound was applied; control groups receiving an ultrasound showed no significant weight loss. Graphic representation of the mass of stone(s) or fragments over time demonstrated that multiple intact stones and multiple stone fragments have a faster reduction than a single large stone or single fragment. Multiple intact stones and fragment groups showed similar rates (p<0.05) showing 91% reduction in 65 minutes. These results suggest that therapeutic ultrasound has the potential for reducing the mass of gallstones in urso-bile and that this effect is accelerated by increasing the number of stones or by fragmentation. |
| Title |
In vitro measurements of sound velocity in human fetal brain tissue. |
| Author |
Wladimiroff JW, Craft IL, Talbert DG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1975 |
| Abstract |
Sound velocity measurements were performed on 23 fresh fetal brain samples obtained at gestations between 17 and 41 weeks duration. Determinations were made at 0, 8, 16, 24, 30, and 37 degrees C. In 14 samples the water content was also calculated. An increase in sound velocity through fetal brain tissue with advancing gestational age, together with an increase in sound velocity associated with increasing temperature of the sample from 0 to 37 degrees C, was found. Sound velocity was higher through fetal brain tissue from pregnancies terminated using intra-amniotic urea when compared with spontaneous abortions of the same gestational age. A significant positive correlation was found between sound velocity and the percentage content of solids in the brain. |
| Title |
In vitro mechanisms of chemopotentiation by tone-burst ultrasound. |
| Author |
Harrison GH, Balcer-Kubiczek EK, Gutierrez PL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1996 |
| Abstract |
We investigated in vitro enhancement of cytotoxicity of chemotherapeutic agents by tone-burst ultrasound. Survival of CHO cells exposed to chemotherapeutic agents in culture medium was determined with and without insonation (1.62 and 0.29 MHz, 10% duty cycle). Insonations up to 0.4 MPa peak pressure (5 kW/m2 spatial and temporal average) occurred in the middle of 1 h drug exposures. Cytotoxicity in ultrasound control groups was never observed. Ultrasound increased the clonogenic cytotoxicity of adriamycin (p = 0.00027 by paired t test) and diaziquone but not of cisplatin or mitomycin C. Potentiation of adriamycin depended on exposure time and tone-burst frequency. −OH production in water occurred at intensities as low as 0.4 kW/m2, but did not increase with added adriamycin. Ultrasound did not affect membrane fluidity, but moderately increased cellular adriamycin accumulation, possibly explaining the observed drug potentiation. |
| Title |
In vitro production of free oxygen radicals induced by pulsed ultrasound in whole blood exposed to diagnostical frequencies and intensities. |
| Author |
Chicca M, Muzzoli M, Pinamonti S. |
| Journal |
Boll Soc Ital Biol Sper |
| Volume |
|
| Year |
1991 |
| Abstract |
No abstract available. |
| Title |
In Vitro sonoluminescence and sonochemistry studies with an electrohydraulic shock-wave lithotripter. |
| Author |
Matula TL Hilmo PR Bailey MR Crum LA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2002 |
| Abstract |
Sonoluminescence and sonochemistry from a cavitation field generated by an electrohydraulic shock-wave lithotripter were investigated as functions of spark discharge voltage (13 to 21 kV) and pulse-repetition frequency (PRF) (0.5 to 2.0 Hz). Sonochemical activity, measured with an iodide dosimeter, increased with both voltage and PRF. Sonoluminescence was measured in an acoustically matched light-tight box. The envelope of the light intensity was measured in a temporally gated region extending from the initial arrival of the shock wave (resulting in bubble compression) to the final inertial collapse of the bubble cloud, which follows hundreds of micros after passage of the shock wave. The initial compression resulted in greater sonoluminescence emissions, suggesting that the initial bubble compression due to the leading positive pressure spike from the lithotripter generated higher temperatures than the inertial collapse of the bubble. These unexpected results are consistent with some recent calculations in which the vapor pressure of the liquid limits compressional heating. |
| Title |
In vitro study of the mechanical effects of shock-wave lithotripsy. |
| Author |
Howard D, Sturtevant B. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1997 |
| Abstract |
Impulsive stress in repeated shock waves administered during extracorporeal shock-wave lithotripsy (ESWL) causes injury to kidney tissue. In a study of the mechanical input of ESWL, the effects of focused shock waves on thin planar polymeric membranes immersed in a variety of tissue-mimicking fluids have been examined. A direct mechanism of failure by shock compression and an indirect mechanism by bubble collapse have been observed. Thin membranes are easily damaged by bubble collapse. After propagating through cavitation-free acoustically heterogeneous media (liquids mixed with hollow glass spheres, and tissue) shock waves cause membranes to fail in fatigue by a shearing mechanism. As is characteristic of dynamic fatigue, the failure stress increases with strain rate, determined by the amplitude and rise time of the attenuated shock wave. Shocks with large amplitude and short rise time. |
| Title |
In vitro thrombolysis enhanced by standing and travelling ultrasound wave fields. |
| Author |
Devcic-Kuhar B,Pfaffenerger S,Groschl M,Kollmann C,Benes E,Gottsauner-Wolf M. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2002 |
| Abstract |
Success of thrombolytic therapy depends on penetration of recombinant tissue plasminogen activator (rt-PA) into clots. Ultrasound (US) of therapeutic quality accelerates thrombolysis in vitro. As yet, only the effects of travelling acoustic waves on thrombolysis have been investigated, and the impact of standing acoustic waves has been neglected. In the present study, we examined the effects of standing and travelling US wave fields applied continuously for 1 h (frequency 2 MHz, acoustic intensity 1.2 W/cm(2)) on thrombolysis enhancement by measuring clot weight reduction and concentration of fibrin degradation product D-dimer (FDP-DD) produced from clots subjected to rt-PA. The level of FDP-DD was 1.8 times greater in travelling than in standing acoustic waves. Thrombolysis enhancement was 46.0 +/- 20.8% in standing and 116.8 +/- 23.1% in travelling acoustic waves. Travelling waves enhanced thrombolysis significantly more (p < 0.0001) than did standing waves. Copyright 2002 World Federation for Ultrasound in Medicine & Biology. |
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