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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 261 out of 330
| Title |
The intensity of ultrasound in the uterus during examination for diagnostic purposes. |
| Author |
Bang J. |
| Journal |
Acta Pathol Microbiol Scand [A] |
| Volume |
|
| Year |
1972 |
| Abstract |
The report here submitted renders an account of the results obtained by measurements of the damping of ultrasound during passage from the abdominal surface to the uterine cavity in women in the reproductive age. Ultrasound was emitted from a transmission transducer on the abdominal surface and received by a specially designed miniature transducer introduced into the uterine cavity. The damping was found to average 2.5 dB. |
| Title |
The interaction of ultrasonic heating and cavitation in vascular bioeffects on mouse intestine. |
| Author |
Miller DL, Gies RA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1998 |
| Abstract |
Anesthetized hairless mice were exposed at the midsection to 400-kHz focused ultrasound that was continuous or pulsed with 100 microseconds pulses, in a temperature-controlled water bath. After exposure, the intestines were evaluated.for petechiae, presumably induced by heating, and hemorrhages, presumably induced by cavitation. Petechiae (up to about 100) occurred above 0.28 MPa (2.6.W cm-2) for 1000 s continuous exposure at 37 degrees C, and the threshold increased to 6.5 MPa (1.4 W cm-2 temporal average) for 1000 s pulsed exposure.(0.001 duty factor). Hemorrhages (up to about 10) were seen above 0.65 MPa.for continuous exposure (10 s, 100 s or 1000 s), and the threshold increased only to 1.6 MPa for 1000 s pulsed exposure (0.001 duty factor). Fractionating a brief continuous exposure into a low duty-factor pulsed exposure greatly decreased the.petechiae, but actually increased the hemorrhages. For example, 1 s continuous exposure at 3.2 MPa (340 W cm-2) averaged 0.33 hemorrhages per mouse, and.1 s on-time pulsed exposure (1000 s duration, 0.001 duty factor) at 3.2 MPa.(0.34 W cm-2 temporal average) averaged 4.3 hemorrhages per mouse. More petechiae were induced at 42 degrees C bath temperature relative to 32 degrees C.or 37 degrees C, and the hemorrhage effect was somewhat enhanced by elevated temperature. Generally, heating and cavitation appeared to have largely independent roles in vascular bioeffects on mouse intestine. |
| Title |
The kinetics and mechanics of ultrasonically-induced cell lysis produced by non-trapped bubbles in a rotating culture tube. |
| Author |
Church CC, Miller MW. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1983 |
| Abstract |
The kinetics of ultrasonically-induced cell lysis are examined in terms of classical radiation biology target theory. A theoretical expression relating the concentration of intact cells remaining after a given period of sonication in a rotating culture tube to the number of non-trapped bubbles, l, which a cell must encounter in order to be lysed is obtained. The expression is compared to experimental results in order to determine the actual value of l. It is found that l equals one (1). The concentration of non-trapped bubbles which is responsible for the observed cell lysis is calculated to be 250-500 cm-3. Finally, it is proposed that non-trapped bubbles tunnel into cells.while undergoing stable cavitation and that cell lysis is produced by one or more transient events inside the cell. |
| Title |
The limitation of the ultrasound intensity for diagnostic devices in the Japanese Industrial Standards. |
| Author |
Maeda K, Ide M. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1986 |
| Abstract |
The limitation of continuous-wave (CW) pulsed ultrasound intensities was discussed in the presentation of the Japanese Industrial Standards (JIS) issued for ultrasound devices. The CW ultrasound intensity is limited to 10 mW/cm2 in the JIS for ultrasonic Doppler fetal diagnostic devices and for manual scanning B-mode diagnostic equipment. However, the JIS intensity limit for A-mode diagnostic equipment is 100 mW/cm2, because the use of the equipment is restricted to diagnosis of intracranial changes of the adult head and is not used for a pregnant woman nor a fetus. The JIS limits the intensity for M-mode equipment to 40 mW/cm2 or less, and this equipment is used primarily for diagnosis of heart disease. The intensity limit is lowered to the level of B-mode equipment (10 mW/cm2) in the combined use of M- and B-modes. In all cases the intensity specified is the temporal average value, averaged spatially over the transducer face. The limitation of ultrasound intensity in the JIS draft of linear electronic scanning real-time B-mode devices, is similar to that for B-mode equipment. The intensity is measured at a single aperture of every transducer after stopping the electronic scanning. An electronic microbalance method is used in the determination of the ultrasound power and intensity in these standards. |
| Title |
The locations of peak pressures and peak intensities in finite amplitude beams from a pulsed focused transducer. |
| Author |
Duck FA, Starritt HC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1986 |
| Abstract |
The effect of finite-amplitude distortion on the positions of peak pressures and peak intensities in beams generated in water by pulsed focused transducers has been investigated experimentally. The pulses generated by three single-element, circular, focused transducers with nominal frequencies of 2.25, 3.5, and 5.0 MHz have been investigated with pressures at the transducer P0 being varied over the range 10 kPa to 1.4 MPa. Measurements were made using a 9 pm thick polyvinylidene difluoride membrane hydrophone. In all cases the locations of peak pressures were not stationary as the field strength was altered. As P0 increased, the distance from the transducer to the positive peak initially increased, and then decreased. The distance to the negative, or decompression peak decreased monotonically with increasing P0. The location of peak pulse intensity integral was found to alter slightly with power, taking a position between the peak positive and negative pressures. |
| Title |
The magnitude of radiation force on ultrasound contrast agents. |
| Author |
Dayton PA, Allen JS, Ferrara KW. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2002 |
| Abstract |
High-speed photography of insonified bubbles with a time resolution of 10 ns allows observations of translation due to radiation force, in addition to the visualization of radial oscillations. A modified version of the Rayleigh?Plesset equation is used to estimate the radius?time behavior of insonified microbubbles, and the accuracy of this model is verified experimentally. The translation of insonified microbubbles is calculated using a differential equation relating the acceleration of the bubble to the forces due to acoustic radiation and the drag imposed by the fluid. Simulations and experiments indicate that microbubbles translate significant distances with clinically relevant parameters. A 1.5 micron radius contrast agent can translate over 5 microns during a single 20-cycle, 2.25 MHz, 380 kPa acoustic pulse, achieving velocities over 0.5 m/s. Therefore, radiation force should be considered during an ultrasonic examination because of the possibility of influencing the position and flow velocity of the contrast agents with the interrogating acoustic beam. |
| Title |
The measurement of attenuation in nonlinearly attenuating media by the zero crossing method. |
| Author |
Narayana PA, Ophir J. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1984 |
| Abstract |
A closed form expression relating the zero crossing density to the material parameters of media with nonlinear frequency dependent attenuation is derived for the case of Gaussian excitation. This expression indicates that for tissues which exhibit a small degree of such nonlinearity, significant errors in the determination of the material parameter result if the nonlinearity is ignored. This result is similar to that shown earlier. |
| Title |
The measurement of ultrasonic power using an acousto-optic method. |
| Author |
Reibold R. |
| Journal |
Acustica |
| Volume |
|
| Year |
1976/77 |
| Abstract |
During the last few years the application of ultrasound in medical diagnosis has gained an increasing importance. This development is of great interest for, compared with X-ray diagnosis, ultrasonic diagnosis gives additional information and reduces the hazard to the human organism. To characterize the properties of medical ultrasonic devices, among other things, the peak values of the sound pressure or of the pressure gradient and the radiated power must be known. This paper deals with the measurement of ultrasonic power by means of an acousto-optic method covering a frequency range from 1 MHz to 8.7 MHz. For comparison investigations, the radiation force method is used. The optical technique based on the light diffraction by ultrasonic waves is evaluated for two different approximate solutions of the Raman-Nath differential equation. Test results and the limits of the applied method are indicated. |
| Title |
The measurement of ultrasound backscattering from cell pellet biophantoms and tumors ex vivo |
| Author |
Han A, Abuhabsah R, Miller RJ, Sarwate S, O'Brien WD Jr. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2013 |
| Abstract |
Simple scattering media fit scattering model theories much better than more complex scattering media. Tissue is much more complex as an acoustic scattering media and to date there has not been an adequate scattering model that fits it well. Previous studies evaluated the scattering characteristics of simple media (grouping of cells at various number densities) and fit them to the concentric
spheres scattering model theory. This study is to increase the complexity of the media to provide insight into the acoustic scattering characteristics of tissue, and specifically two tumor types. Complementing the data from the tumors is 100% volume fraction cell pellets of the same cell lines. Cell pellets and ex vivo
tumors are scanned using high-frequency single-element transducers (9–105MHz), and the attenuation and backscatter coefficient (BSC) are estimated. BSC compari-
sons are made between cell pellets and tumors. The results show that the 4T1 (ATCC #CRL-2539) cell pellets and tumors have similar BSC characteristics, whereas the MAT (ATCC #CRL-1666) cell pellets and tumors have significantly different BSC characteristics. Factors that yield such differences are explored. Also, the fluid-filled sphere and the concentric spheres models are evaluated
against the BSC characteristics, demonstrating that further work is required |
| Title |
The measurement of ultrasound scattering from individual micron-sized objects and its application in single cell scattering. |
| Author |
Falou O, Rui M, El Kaffas A, Kumaradas JC, Kolios MC. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2010 |
| Abstract |
The measurement of the ultrasound backscatter from individual micron-sized objects such as cells is required for various applications such as tissue characterization. However, performing such a measurement remains a challenge. For example, the presence of air bubbles in a suspension of cells during the measurements may lead to the incorrect interpretation of the acoustic signals. This work introduces a technique for measuring the ultrasound backscatter from individual micron-sized objects by combining a microinjection system with a co-registered optical microscope and an ultrasound imaging device. This allowed the measurement of the ultrasound backscatter response from a single object under optical microscope guidance. The optical and ultrasonic data were used to determine the size of the object and to deduce its backscatter responses, respectively. In order to calibrate the system, the backscatter frequency responses from polystyrene microspheres were measured and compared to theoretical predictions. A very good agreement was found between the measured backscatter responses of individual microspheres and theoretical predictions of an elastic sphere. The backscatter responses from single OCI-AML-5 cells were also investigated. It was found that the backscatter responses from AML cells are best modeled using the fluid sphere model. The advantages, limitations, and future applications of the developed technique are discussed. |
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