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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 123 out of 330
| Title |
Exposure-time dependence of the threshold for ultrasonically induced murine lung hemorrhage. |
| Author |
Raeman CH, Child SZ, Dalecki D, Cox C, Carstensen EL. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1996 |
| Abstract |
Although the extent of suprathreshold damage to murine lung that results from.exposure to pulsed ultrasound increases with time, the threshold level for lung.hemorrhage is relatively insensitive to total exposure time. Adult mice were.exposed for 20 s and 3 min to 2.3-MHz ultrasound (10-?s pulses,.100-Hz pulse repetition frequency) at peak positive pressures ranging up to 3.MPa. Threshold pressures for the two exposure times, 1.6 MPa and 1.4 MPa,.respectively, are the same within the statistical significance of the measurements. |
| Title |
Extended three-dimensional impedance map methods for identifying ultrasonic scattering sites. |
| Author |
Mamou J, Oelze ML, O'Brien WD Jr. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2008 |
| Abstract |
The frequency-dependent ultrasound backscatter from tissues contains information about the microstructure that can be quantified. In many cases, the anatomic microstructure details responsible for ultrasonic scattering remain unidentified. However, their identification would lead to potentially improved methodologies for characterizing tissue and diagnosing disease from ultrasonic backscatter measurements. Recently, three-dimensional (3D) acoustic models of tissue microstructure, termed 3D impedance maps (3DZMs), were introduced to help to identify scattering sources [J. Mamou, M. L. Oelze, W. D. O'Brien, Jr., and J. F. Zachary, “Identifying ultrasonic scattering sites from 3D impedance maps,” J. Acoust. Soc. Am. 117, 413–423 (2005)]. In the current study, new 3DZM methodologies are used to model and identify scattering structures. New processing procedures (e.g., registration, interpolations) are presented that allow more accurate 3DZMs to be constructed from histology. New strategies are proposed to construct scattering models [i.e., form factor (FF)] from 3DZMs. These new methods are tested on simulated 3DZMs, and then used to evaluate 3DZMs from three different rodent tumor models. Simulation results demonstrate the ability of the extended strategies to accurately predict FFs and estimate scatterer properties. Using the 3DZM methods, distinct FFs and scatterer properties were obtained for each tumor examined. |
| Title |
Extracorporeal shock waves act by shock wave-gas bubble interaction. |
| Author |
Delius M, Ueberle F, Eisenmenger W. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1998 |
| Abstract |
The effect of extracorporeal shock waves on hemoglobin release from red blood cells was recently found to be minimized under minute static excess pressure. It was proposed that this can be explained by shock wave-gas bubble interaction. We substantiated this further by two experiments by applying shock waves to suspended human RBC in a lithotripter at a lower frequency (1 pulse every 5 s) and by administering just a single or 2 strong shock waves at 30 kV. Compared to the usual application rate of 1 discharge per s, the lower frequency reduced the hemoglobin release under minimal static excess pressure in the range from 0-100m kPa. A single strong shock wave released a small amount of hemoglobin at ambient pressure and a similar amount at 200 kPa excess pressure. Two strong shock waves increased the hemoglobin release considerably at ambient pressure when there was a 1- or a 10-s pause between them. Under 200 kPa excess pressure, the hemoglobin release was minimal. A similar low hemoglobin release was also found with 1 shock at ambient and the other at excess pressure. The results are interpreted as clear evidence of shock wave-gas bubble interaction as a dominant mechanism of shock wave action. |
| Title |
Fabrication and characterization of transducer elements intwo-dimensional arrays for medical ultrasound imaging. |
| Author |
turnbull DH, Foster FS. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1992 |
| Abstract |
Some of the problems of developing a two-dimensional (2-D) transducer array for medical imaging are examined. The fabrication of a 2-D array material consisting of lead zirconate titanate (PZT) elements separated by epoxy is discussed. Ultrasound pulses and transmitted radiation patterns from individual elements in the arrays are measured. A diffraction theory for the continuous wave pressure field of a 2-D array element is generalized to include both electrical and acoustical cross-coupling between elements. This theory can be fit to model the measured radiation patterns of 2-D array elements, giving an indication of the level of cross-coupling in the array, and the velocity of the acoustic cross-coupling wave. Improvements in bandwidth and cross-coupling resulting from the inclusion of a front acoustic matching layer are demonstrated, and the effects of including a lossy backing material on the array are discussed. A broadband electrical matching network is described, and pulse-echo waveforms and insertion loss from a 2-D array element are measured
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| Title |
Fabrication of high frequency spherically shaped ceramic transducers. |
| Author |
Lockwood GR, Foster FS, Turnbull DH. |
| Journal |
IEEE Trans Ultrason Ferroelectr Freq Control |
| Volume |
|
| Year |
1994 |
| Abstract |
Difficulty in obtaining well focused efficient ultrasound transducers has limited the development of new high frequency applications of B-mode imaging. This paper describes a method for fabricating high frequency (53 MHz) spherically focused lead zirconate titanate (PZT) transducers. A transducer is fabricated by bonding a malleable backing layer onto a thin plate of PZT and then pressing the plate into a spherically shaped well. The backing layer evenly distributes stresses across the material when it is pressed into the well. Local concentrations of stress which lead to fracture are avoided and the material can be deformed without macroscopic cracking. The characteristics of a 2 mm diameter 53 MHz PZT transducer with a 4 mm focal length are described. A lateral beam width of 68 μm and a 12 dB depth of field of 1.5 mm were obtained. The minimum two-way insertion loss of the system was -25 dB and the 6 dB bandwidth of the pulse echo response was 30%. An image of a resolution phantom and an in vivo skin image illustrate the excellent imaging characteristics of the transducer. |
| Title |
Factors affecting the choice of preamplification for ultrasonic hydrophone probes. |
| Author |
Lewin PA, Schafer ME, Chivers RC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1987 |
| Abstract |
This paper gives a systematic analysis of the effects of including an integrated (built-in) preamplifier into the ultrasonic piezoelectric probes (hydrophones) that are finding increasing use in biomedical applications. The design parameters.considered include the end-of-cable sensitivity, gain, dynamic range, power supply requirements, construction intricacy, and cost. The rationale behind the inclusion of a preamplifier is given, and it is shown that the additional complexity introduced.with the preamplifier into the measurement chain may not be warranted in all applications. Both the drawbacks and advantages of hydrophone preamplification are demonstrated, especially for the case of high pressure amplitude ultrasonic.field measurements. Guidelines are developed for the potential user to identify the need for preamplification and the factors that influence the selection of the appropriate circuitry. |
| Title |
Factors critical to highly accurate diagnoses of malignant breast pathologies by ultrasound imaging. |
| Author |
Kelly-Fry E, Harper AP. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1983 |
| Abstract |
In an interdisciplinary program on diagnoses of breast pathologies by ultrasonic imaging, analyses of results have been completed for a symptomatic population totaling 1892 subjects. Application of a comparatively simple ultrasound instrument in conjunction with specific examination techniques has allowed the achievement of a diagnostic accuracy of 95% for the 73 malignant masses which have been encountered in the examined population. |
| Title |
Factors in selecting the dosage of ultrasound: With particular reference to the use of various coupling agents. |
| Author |
Reid DC, Cummings GE. |
| Journal |
N/A |
| Volume |
|
| Year |
Unknown |
| Abstract |
No abstract available. |
| Title |
Factors in selecting the dosage of ultrasound: with particular reference to the use of various coupling agents. |
| Author |
Reid DC, Cummings GE. |
| Journal |
APMR |
| Volume |
|
| Year |
1973 |
| Abstract |
No abstract available. |
| Title |
Factors influencing the use of ultrasound as a diagnostic aid. |
| Author |
Ludwig GD, Bolt RH, Heuter TF, Ballantine HT Jr. |
| Journal |
Trans Am Neurol Assoc |
| Volume |
|
| Year |
1950 |
| Abstract |
No abstract available. |
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