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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 172 out of 330
| Title |
Measurement of velocity and absorption of ultrasound in epoxy resins. |
| Author |
Mikhailov IG, Savina LI. |
| Journal |
Ukr Phys J |
| Volume |
|
| Year |
1967 |
| Abstract |
No abstract available. |
| Title |
Measurement of velocity of propagation from ultrasonic pulse-echo data. |
| Author |
Robinson DE, Chen F, Wilson LS. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
A method is proposed for determining velocity of propagation of ultrasound in tissue by processing the pulse-echo data obtained from a compound scan. Individual sectors from different transducer positions are reconstructed and a suitable area common to the two sectors is selected. Cross-correlation of the region of interest is used to detect an apparent shift in the image due to refractive effects. The refractive effects are analysed by a ray-tracing procedure to determine an effective velocity within the tissue. The system has been tested using the U.I. Octoson as input device and both model targets with known velocity of propagation and in vivo liver tissue. The accuracy in the model experiment was +/- 5 ms-1 while the repeatability of measurements in tissue was +/- 15 ms-1. techniques for extending the method to multiple region systems are suggested. |
| Title |
Measurement of volumetric blood flow using ultrasound time-domain correlation. |
| Author |
Hein IA. |
| Journal |
Thesis(PhD): Univ of Illinois |
| Volume |
|
| Year |
1991 |
| Abstract |
No Abstract Available. |
| Title |
Measurements and analysis of speckle in ultrasound B-scans. |
| Author |
Smith SW, Sandrik JM, Wagner RF, van Ramm OT. |
| Journal |
Acoust Imaging |
| Volume |
|
| Year |
1981 |
| Abstract |
No abstract available. |
| Title |
Measurements of articular tissues with ultrasound. |
| Author |
Dussik KT, Frith DJ, Kyriazidou M, Sear RS. |
| Journal |
J Phys Med |
| Volume |
|
| Year |
1958 |
| Abstract |
No abstract available. |
| Title |
Measurements of articular tisues with ultrasound. |
| Author |
Dussik KT, Fritch DJ, Kyriazidou M, Sear RS. |
| Journal |
Proc Int Conf Ultrason Med - Los Angeles |
| Volume |
|
| Year |
1957. |
| Abstract |
No abstract available. |
| Title |
Measurements of attenuation coefficient for evaluating the hardness of a cataract lens by a high-frequency ultrasonic needle transducer. |
| Author |
Huang CC, Chen R, Tsui PH, Zhou Q, Humayun MS, Shung KK. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
2009 |
| Abstract |
A cataract is a clouding of the lens in the eye that affects vision. Phacoemulsification is the mostly common surgical method for treating cataracts, and determining that the optimal phacoemulsification energy is dependent on measuring the hardness of the lens. This study explored the use of an ultrasound needle transducer for invasive measurements of ultrasound attenuation coefficient to evaluate the hardness of the cataract lens. A 47 MHz high-frequency needle transducer with a diameter of 0.9 mm was fabricated by a polarized PMN-33%PT single crystal in the present study. The attenuation coefficients at different stages of an artificial porcine cataract lens were measured using the spectral shift approach. The hardness of the cataract lens was also evaluated by mechanical measurement of its elastic properties. The results demonstrated that the ultrasonic attenuation coefficient was increased from 0.048 ± 0.02 to 0.520 ± 0.06 dB mm−1 MHz−1 corresponding to an increase in Young's modulus from 6 ± 0.4 to 96 ± 6.2 kPa as the cataract further developed. In order to evaluate the feasibility of combining needle transducer and phacoemulsification probe for real-time measurement during cataract surgery, the needle transducer was mounted on the phacoemulsification probe for a vibration test. The results indicated that there was no apparent damage to the tip of the needle transducer and the pulse–echo test showed that a good performance in sensitivity was maintained after the vibration test. |
| Title |
Measurements of bubble-enhanced heating from focused, MHz-frequency ultrasound in a tissue-mimicking material. |
| Author |
Holt RG, Roy RA. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2001 |
| Abstract |
Time-resolved measurements of the temperature field in an agar-based tissue-mimicking phantom insonated with a large aperture 1-MHz focused acoustic transducer are reported. The acoustic pressure amplitude and insonation duration were varied. Above a critical threshold acoustic pressure, a large increase in the temperature rise during insonation was observed. Evidence for the hypothesis that cavitation bubble activity in the focal zone is the cause of enhanced heating is presented and discussed. Mechanisms for bubble-assisted heating are presented and modeled, and quantitative estimates for the thermal power generated by viscous dissipation and bubble acoustic radiation are given. |
| Title |
Measurements of frequency spectra of transmission.coefficients to ultrasound through trapped.microbubbles. |
| Author |
Wu J, Nyborg WL. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1990 |
| Abstract |
Techniques which use hydrophobic polycarbonate thin sheets containing randomly spaced, fairly.uniform small pores immersed in water to trap air bubbles have been found to be useful in.biophysical experiments. The utilization of broadband polyvinylidene fluoride transducers in this.work made it possible to measure a continuous frequency spectrum of the transmission.coefficient of the trapped bubbles. The results of the measurements show: (1) the frequency.response curve of the bubble ensemble is much broader than that of a single bubble predicted by.theory; and (2) as the incident sound pressure at a micropore membrane increases from 110 to.660 Pa the resonance frequency of bubbles shifts to lower values by as much as 7%. |
| Title |
Measurements of the velocity and absorption of ultrasound in liquid gallium. |
| Author |
Proffit RL, Carome EF. |
| Journal |
Rep Dept Navy Off Nav Res |
| Volume |
|
| Year |
1962 |
| Abstract |
Ultrasonic velocity measurements have been made in liquid gallium over the temperature range from 20 to 40?C. The value of the velocity measured at the freezing point, 29.8?C, is 2871.1 ? 0.3 m/sec and the temperature coefficient of velocity is -0.3 m/sec/?C. Preliminary absorption measurements also have been made, and the measured value of l/v(2) is 2.5 ? 0.3 x 10(-17) cm(-1) sec(2) at 30?C. |
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