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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 153 out of 330
| Title |
Influence of microbubble size distribution on postexcitation thresholds for single ultrasound contrast agent using double passive cavitation detection. |
| Author |
Gauthier M, King DA, O'Brien WD Jr. |
| Journal |
IEEE Int Ultrason Symp Proc |
| Volume |
|
| Year |
2012 |
| Abstract |
A recent study has shown that double passive cavitation detection (DPCD) is a valid method for determining cavitation characteristics including collapse thresholds of isolated microbubbles based on the detection of postexcitation signal (PES) occurring 1 to 5 μs after the principle excitation of the bubble. The hypothesis is that PES is associated with the collapse of a free gas bubble released from the ultrasound contrast agent (UCA) after the rupture of its shell. It has been shown that responses of UCAs depend on several parameters such as the
shell and gas core as well as the size of the microbubble. However, a detailed study of the influence of size distribution only on single microbubble collapse thresholds is still not available. The aim of this study was to determine whether there was a significant correlation between microbubble size distribution and collapse thresholds. Experiments were performed using serum albumin and dextrose microbubbles. Four size distributions were obtained and we determined
microbubble collapse thresholds for each distribution using the DPCD method (3 cycle tone bursts at the central frequency of 4.6 MHz). Statistical analysis was based on comparing the means of collapse threshold for the four size distributions using an analysis of variance. The microbubble collapse threshold was found to be significantly (p<0.05) correlated to the microbubble size
distribution: the DPCD experiments demonstrated that, in the configuration of the experiments, PES thresholds were higher for microbubbles exhibiting smaller size distribution. |
| Title |
Influence of microbubble size on postexcitation collapse thresholds for single ultrasound contrast agents using double passive cavitation detection. |
| Author |
Gauthier M, King DA, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2013 |
| Abstract |
For the first time, and using an acoustical method, it has been shown experimentally that the inertial cavitation threshold pressure of an albumin-shelled microbubble is significantly correlated with its initial size. |
| Title |
Influence of pathological state on the acoustic attenuation coefficient slope of liver. |
| Author |
Afschrift M, Cuvelier C, Ringoir S, Barbier F. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
The acoustic attenuation coefficient slope (beta) of liver was estimated in vivo from the spectral difference of returned echoes. beta of normal young subjects was lower than that of older subjects (mean: 0.340 vs 0.418 dB/cm.MHz). Limited fluid withdrawal from the body by haemodialysis did not affect beta. In alcoholic liver disease beta was related to the amount of fat and of fibrous tissue in liver biopsy specimens. High values of beta were observed as soon as the degree of steatosis exceeded 5 vol%. There was a similar increase of beta in the presence of fibrous interlobular septa. In normal liver beta was related to the amount of triglycerides in the liver specimen. |
| Title |
Influence of temperature and pressure on the lethality of ultrasound. |
| Author |
Raso J,Pagàn R,Condon S,Sala FJ. |
| Journal |
Appl Environ Microbiol |
| Volume |
|
| Year |
1998 |
| Abstract |
A specially designed resistometer was constructed, and the lethal effect on Yersinia enterocolitica of ultrasonic waves (UW) at different static pressures (manosonication [MS]) and of combined heat-UW under pressure treatments (manothermosonication [MTS]) was investigated. During MS treatments at 30°C and 200 kPa, the increase in the amplitude of UW of 20 kHz from 21 to 150 µm exponentially decreased decimal reduction time values (DMS) from 4 to 0.37 min. When pressure was increased from 0 to 600 kPa at a constant amplitude (150 µm) and temperature (30°C), DMS values decreased from 1.52 to 0.20 min. The magnitude of this decrease in DMS declined progressively as pressure was increased. The influence of pressure on DMS values was greater with increased amplitude of UW. Pressure alone of as much as 600 kPa did not influence the heat resistance of Y. enterocolitica (D60 = 0.094; z = 5.65). At temperatures of as much as 58°C, the lethality of UW under pressure was greater than that of heat treatment alone at the same temperature. At higher temperatures, this difference disappeared. Heat and UW under pressure seemed to act independently. The lethality of MTS treatments appeared to result from the added effects of UW under pressure and the lethal effect of heat. The individual contributions of heat and of UW under pressure to the total lethal effect of MTS depended on temperature. The inactivating effect of UW was not due to titanium particles eroded from the sonication horn. The addition to the MS media of cysteamine did not increase the resistance of Y. enterocolitica to MS treatment. MS treatment caused cell disruption. |
| Title |
Influence of the ultrasound transducer bandwidth on selection of the complementary Golay bit code length. |
| Author |
Nowicki A, Trots I, Lewin PA, Secomski W, Tymkiewicz R. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
2007 |
| Abstract |
In contrast to previously published papers [A. Nowicki, Z. Klimonda, M. Lewandowski, J. Litniewski, P.A. Lewin, I. Trots, Comparison of sound fields generated by different coded excitations - Experimental results, Ultrasonics 44 (1) (2006) 121-129; J. Litniewski, A. Nowicki, Z. Klimonda, M. Lewandowski, Sound fields for coded excitations in water and tissue: experimental approach, Ultrasound Med. Biol. 33 (4) (2007) 601-607], which examined the factors influencing the spatial resolution of coded complementary Golay sequences (CGS), this paper investigates the effect of ultrasound imaging transducer's fractional bandwidth on the gain of the compressed echo signal for different spectral widths of the CGS. Two different bit lengths were considered, specifically one and two cycles. Three transducers having fractional bandwidth of 25%, 58% and 80% and operating at frequencies 6, 4.4 and 6 MHz, respectively were examined (one of the 6 MHz sources was focused and made of composite material). The experimental results have shown that by increasing the code length, i.e. decreasing the bandwidth, the compressed echo amplitude could be enhanced. The smaller the bandwidth was the larger was the gain; the pulse-echo sensitivity of the echo amplitude increased by 1.88, 1.62 and 1.47, for 25%, 58% and 80% bandwidths, respectively. These results indicate that two cycles bit length excitation is more suitable for use with bandwidth limited commercially available imaging transducers. Further, the time resolution is retained for transducers with two cycles excitation providing the fractional bandwidth is lower than approximately 90%. The results of this work also show that adjusting the code length allows signal-to-noise-ratio (SNR) to be enhanced while using limited (less that 80%) bandwidth imaging transducers. Also, for such bandwidth limited transducers two cycles excitation would not decrease the time resolution, obtained with "conventional" spike excitation. Hence, CGS excitation could be successfully implemented with the existing, relatively narrow band imaging transducers without the need to use usually more expensive wideband, composite ones. |
| Title |
Influence of ultrasonic radiation in the medical therapeutic range on the fine structure of the liver parenchymal cell. An electron microscope study on mice. |
| Author |
Valtonen EJ. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
1967 |
| Abstract |
Ultrasonic energy of an intensity from 0.5 to 3 watts/cm2 was applied on the upper abdomen of unanaesthetized mice and specimens of the liver were examined with the electron microscope. The appearance of the fine structure of the liver cells ranged from nearly normal (intensity of 1 watt/cm2 for 1 minute) to complete loss (coagulation) of the fine structure of the cell organelles (intensity of 3 watts/cm2 for 3 minutes). In addition, cavitation and disruption of the cytoplasm occurred in the hepatic cells. The changes are probably due to both the thermal and mechanical effects of the ultrasound, but also the relative anoxia may play some role in causing the formation of intracellular vacuoles.Ultraschallenergie in einer Intensität von 0.5 bis 3 Watt/cm2 wurde auf den Oberbauch nicht-anaesthesierter Mäuse aufgebracht. Danach wurden Leberstückchen elektronenmikroskopisch untersucht. Das Aussehen der Leberzellen schwankte von fast normal (1 Watt/cm2 für 1 min) bis zu völligem Verlust (Coagulation) der Feinstruktur der Zellorganellen (3 Watt/cm2 für 3 min). Außerdem kam es zur Kavitation und Zerreißungen im Cytoplasma der Leberzellen. Die Veränderungen sind wahrscheinlich bedingt durch die sowohl thermalen wie mechanischen Wirkungen des Ultraschalls; allerdings mag auch die relative Anoxie eine Rolle bei der Entstehung der intracellulären Vacuolen spielen. |
| Title |
Influence of ultrasound on the percutaneous absorption of nicotinate esters. |
| Author |
Benson HAE, McElnay JC, Harland R, Hadgraft J. |
| Journal |
Pharm Res |
| Volume |
|
| Year |
1991 |
| Abstract |
The influence of ultrasound on the percutaneous absorption of three nicotinate esters was investigated in 10 healthy volunteers in a double-blind placebo controlled crossover clinical trial. Using a specially designed experimental protocol, the effect of continuous output ultrasound (at frequency 3.0 MHz and intensity 1.0 W/cm2 for 5 min) on the percutaneous absorption of methyl, ethyl, and hexyl nicotinates, from gel bases, was investigated. A placebo control, involving massage with each of the gels, without ultrasound for 5 min, was also incorporated. The pharmacodynamic parameter of vasodilation caused by the nicotinates was used to monitor the percutaneous absorption of the drugs. Laser Doppler velocimetry, a noninvasive optical technique, was used to measure vasodilation of the cutaneous vessels within the treatment site. Ultrasound treatment led to enhanced vasodilator response to the nicotinates, therefore indicating an enhancement of their percutaneous absorption. These agents may prove to be useful compounds in examination of the mechanism of action of phonophoresis.
|
| Title |
Influences of growth conditions and cell-cell contact on responses of tumor cells to ultrasound. |
| Author |
Sacks PG, Miller MW, Sutherland RM. |
| Journal |
Radiat Res |
| Volume |
|
| Year |
1981 |
| Abstract |
The response of EMT6/Ro multicell spheroids at early stages of growth (1-3 days) to 1-MHz ultrasonic irradiation was compared to EMT6/Ro cells which were grown under suspension or as attached monolayers. The surviving fraction of cells was evaluated by measuring both direct cell lysis and clonogenicity of cells not lysed during sonication. Irradiation was for 1 min at 0, 1, 3, or 5 W/cm(^2) (spatial peak, temporal peak) at 37 C. At 3 and 5 W/cm(^2), there was a 9- to 10-fold enhancement in the surviving fraction of spheroids as compared to that of monolayer cells. Individual spheroid cells do not appear to be physiologically altered with respect to their response to ultrasound since cells from dissociated spheroid exhibit survival parameters which are similar to those of cells grown in monolayers. The basis for the increased survival of whole spheroids appears to be due to a physical protection of the cells in spheroids. Studies examining effects of trypsin treatment indicate that a slight decrease in survival which occurred at 1 W/cm2 was associated with the trypsin treatment. Of the 9- to 10-fold increase in survival of whole spheroids, 2- to 3-fold increase was related to trypsin with a 6- to 7-fold increase related to the multicellular nature of spheroids (termed contact effect). Experiments with increased atmospheric pressure and temperature measurements indicate that cavitation is the main mechanism producing these bioeffects. |
| Title |
Influences of microbubble diameter and ultrasonic parameters on in vitro sonothrombolysis efficacy. |
| Author |
Borrelli MJ, O'Brien WD Jr, Hamilton E, Oelze ML, Wu J, Bernock LJ, Tung S, Rokadia H, Culp WC. |
| Journal |
J Vasc Interv Radiol |
| Volume |
|
| Year |
2012 |
| Abstract |
Purpose: To quantify the effects of microbubble (MB) size, elasticity, and pulsed ultrasonic parameters on in vitro sonothrombolysis (ultrasound [US]-mediated thrombolysis) efficacy.
Materials and Methods: Monodispersive MBs with diameters of 1 mm or 3 mm were exposed to pulsed US (1MHz or 3MHz) to lyse rabbit bloodclots. Sonothrombolysis efficacy (clot mass loss) was measured as functions of MB size and concentration, ultrasonic frequency and intensity, pulse duration (PD), pulse repeat frequency (PRF), and duty factor.
Results: Sonothrombolysis at 1 MHz was more effective using 3-mm MBs and at 3MHz using 1-mm MBs. Sonothrombolysis was more effective at 1MHz when Z 75% of MBs remained intact, especially for 3-mm MBs; improving sonothrombolysis by increasing PRF from 100Hz to 400Hz at 3MHz was associated with increasing 3-mm MB survival. However, 60% of 1-mm MBs were destroyed during maximal sonothrombolysis at 3MHz, indicating that considerable MB collapse may be required for sonothrombolysis under these conditions.
Conclusions: The ability to control MB size and elasticity permits using a wide range of US parameters (eg, frequency, intensity) to produce desired levels of sonothrombolysis. Comparable, maximal sonothrombolysis efficacy was achieved at 20-fold lower intensity with 3-mm MBs (0.1W/cm2) than with1-mm MBs (2.0W/cm2), a potential safety issue for in vivo sonothrombolysis. US parameters that maximizedMB survival yielded maximal sonothrombolysis efficacy except with 1-mm MBs at 3MHz where most MBs were destroyed.
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| Title |
Influences on the development of ultrasound pulse-echo breast instrumentation in the united states. |
| Author |
Fry-Kelly E. |
| Journal |
Radiology |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
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