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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 244 out of 330
| Title |
Techniques and evaluation from a cross-platform imaging comparison of quantitative ultrasound parameters in an in vivo rodent fibroadenoma model |
| Author |
Wirtzfeld LA, Nam K, Labyed Y, Ghoshal G, Haak A, Sen-Gupta E, He Z, Hirtz NR, Miller RJ, Sarwate S, Simpson DG, Zagzebski JA, Bigelow TA, Oelze ML, Hall TJ, O'Brien WD Jr. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2013 |
| Abstract |
This contribution demonstrates that quantitative ultrasound (QUS) capabilities are platform independent, using an in vivo model. Frequency-dependent attenuation estimates, backscatter coefficient, and effective scatterer diameter estimates are shown to be comparable across four different ultra
- sound imaging systems with varied processing techniques. The backscatter coefficient (BSC) is a fundamental material property from which several QUS parameters are estimated; therefore, consistent BSC estimates among different systems must be demonstrated. This study is an intercomparison of BSC
estimates acquired by three research groups (UIUC, UW, ISU) from four
in vivo spontaneous rat mammary fibroadenomas using three clinical array systems and a single-element laboratory scanner system. Because of their highly variable backscatter properties, fibroadenomas provided an extreme test case for
BSC analysis, and the comparison is across systems for each tumor, not across the highly heterogeneous tumors. RF echo data spanning the 1 to 12MHz frequency range were acquired in three dimensions from all animals using each system. Each
research group processed their RF data independently, and the resulting attenuation, BSC, and effective scatterer diameter (ESD) estimates were compared. The attenuation estimates across all systems showed the same trends and consistently fit the power-law dependence on frequency. BSCs varied among
the multiple slices of data acquired by each transducer, with variations between transducers being of a similar magnitude as those from slice to slice. Variation between BSC estimates was assessed via functional signal-to-noise ratios derived from backscatter data. These functional signal-to-noise ratios indicated that BSC versus frequency variations between systems ranged from negligible compared with the noise level to roughly twice the noise level. The corresponding functional analysis of variance (fANOVA) indicated statistically significant differences between BSC curves from different systems. However, root
mean squared difference errors of the BSC values (in decibels) between different transducers and imaging platforms were less than half of the BSC magnitudes in most cases. Statistical comparison of the effective scatterer diameter (ESD) estimates resulted in no significant differences in estimates from three of the four transducers used for those estimates, demonstrating
agreement among estimates based on the BSC. This technical advance demonstrates that these in vivo measurements can be made in a system-independent manner; the necessary step toward clinical implementation of the technology. |
| Title |
Techniques for perfusion imaging with microbubble contrast agents. |
| Author |
Simpson DH, Burns PN, Averkiou MA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2001 |
| Abstract |
The acoustic properties of ultrasound contrast agents vary widely with agent composition and insonation conditions. For contrast imaging, methods are required to match RF and Doppler processing to each combination of transmission parameters and agent and tissue properties. We propose a method that uses the measured or modeled echoes from agent and tissue to specify directly the characteristics of RF and Doppler filters for contrast imaging. The proposed method is sufficiently general to cover most common imaging techniques including harmonic greyscale, Doppler, and pulse inversion imaging. Using this method, sample filters were designed to detect myocardial perfusion with the contrast agent OptisonTM (Mallinckrodt Medical, St. Louis, MO) under selected imaging conditions. Simplified power Doppler filtering, using a weighted sum of the Doppler samples, matched the performance of more complicated matrix filters. By coordinating the selection of RF and Doppler filters rather than designing these filters sequentially, agent-to-tissue contrast was increased by up to 3.9 dB. Under some conditions, fundamental RF filtering outperformed harmonic filtering for intermittent Doppler imaging. |
| Title |
Techniques used in ultrasonic visualization of soft tissues. |
| Author |
Howry DH. |
| Journal |
Ultrasound Biol Med |
| Volume |
|
| Year |
unknown (mid-late 50's) |
| Abstract |
No abstract available. |
| Title |
Technische Voraussetzungen der praktischen Ultrashall-Diagnostik. (Technical requirements of field-tested diagnostic ultrasound.) Article is in German. |
| Author |
Pohlman R, Lierke G. |
| Journal |
Med-Markt Acta Medicotech |
| Volume |
|
| Year |
1962 |
| Abstract |
No abstract available. |
| Title |
Technological and research applications of very high power ultrasound. |
| Author |
Fry WJ, Dunn F, Fry FJ, Fry TA, Leichner G, Schad FM. |
| Journal |
Rep Intersci Res Inst |
| Volume |
|
| Year |
1962 |
| Abstract |
No abstract available. |
| Title |
Technology of real-time ultrasound. |
| Author |
Kossoff G. |
| Journal |
Contrib Gynecol Obstet |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Temperature and frequency dependance of ultrasonic attenuation in selected tissues. |
| Author |
Gammel PM, Croissette DH, Heyser RC. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1979 |
| Abstract |
Ultrasonic attenuation over the frequency range of 1.5–10 MHz has been measured as a function of temperature for porcine liver, backfat, kidney and spleen as well as for a single specimen of human liver. The attenuation in these excised specimens increases nearly linearly with frequency. Over the temperature range of approximately 4°–37°C the attenuation decreases with increasing temperature for most soft tissue studied. |
| Title |
Temperature changes produced in tissue during ultrasonic irradiation. |
| Author |
Fry WJ, Fry RB. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1953 |
| Abstract |
This paper is concerned with the technique of temperature measurement in living tissue during irradiation by high intensity ultrasound. The interpretation of data obtained by the use of thermocouples is presented. The specific biological object used in this study is the spinal cord of rat exposed by laminectomy. This particular preparation serves to illustrate the relative importance of the heat conduction process in contributing to the temperature change as a function of the proximity of the imbedded thermocouple to bone and the time elapsed after initiation of the exposure. The ultrasonic frequency used in these studies was 980 kc. The sound intensities on the cord were between 60 and 80 watts/cm(^2). The experimental results presented in the paper are used to obtain values for the acoustic absorption coefficient of the tissue of the spinal cord. The range of values obtained for the intensity absorption coefficient per centimeter from measurements made on six adult rats at various positions in the spinal cord is 0.19 to 0.23 if the heat capacity of the tissue at constant pressure is 1.00 calorie/cm(^3). |
| Title |
Temperature dependency of ultrasonic propagation properties in biological materials. |
| Author |
Haney MJ, O'Brien WD Jr.(Greenleaf JF, ed.) |
| Journal |
Book Chapter |
| Volume |
|
| Year |
1986 |
| Abstract |
The interaction of low-intensity ultrasound (with assumed infinitesimal wave propagation) and biological material can be summarized with three primitive variables: density, adiabatic compressibility, and absorption. These variables determine physical properties that are more readily measurable: density and compressibility determine the refraction, diffraction, and scattering; scattering and absorption yield attenuation. Measuring these tissue properties is the first step in tissue characterization.
The most popularly measured ultrasound properties are velocity, attenuation (in general), and absorption (in specific). The thermal dependence of these properties can be appreciated in the most general sense from a simplified view of the physics involved. As temperature increases, density decreases (since most materials experience a volume expansino with increased temperature). Lowering density while keeping the (adiabatic) compressibility constant should cause an increase in velocity. For heterogeneous media, if the velocities of the various constituent materials increase at differing rates so as to approach one another, the media should become "less" hterogeneous, resulting in a decrease in refraction and scattering amplitude. If the velocities increase so as to diverge from each other, both refraction and scattering should increase. (In either event, scattering as a function of frequency should experience a shift toward higher frequencies resulting from teh increase in velocity.) Finally absorption, if modeled as a relaxation process, should also show a shift of the relaxation frequency toward higher frequencies, resulting in increases or decreases in absorption, depending on the frequency at which the measurement is being made. (The attenuation follows from the absorption and scattering.) Thus, from this superficial modeling, velocity and attenuation should be temperature sensitive. It is the purpose of this review to present and discuss the termperature-dependent behavior of these ultrasonic properties in biological materials. |
| Title |
Temperature dependent ultrasonic characterization of biological media. |
| Author |
Ghoshal G, Luchies AC, Blue JP, Oelze ML. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2011 |
| Abstract |
Quantitative ultrasound (QUS) is an imaging technique that can be used to quantify tissue microstructure giving rise to scattered ultrasound. Other ultrasonic properties, e.g., sound speed and attenuation, of tissues have been estimated versus temperature elevation and found to have a dependence with temperature. Therefore, it is hypothesized that QUS parameters may be sensitive to changes in tissue microstructure due to temperature elevation. Ultrasonic backscatter experiments were performed on tissue-mimicking phantoms and freshly excised rabbit and beef liver samples. The phantoms were made of agar and contained either mouse mammary carcinoma cells (4T1) or chinese hamster ovary cells (CHO) as scatterers. All scatterers were uniformly distributed spatially at random throughout the phantoms. All the samples were scanned using a 20-MHz single-element f/3 transducer. Quantitative ultrasound parameters were estimated from the samples versus increases in temperature from 37 °C to 50 °C in 1 °C increments. Two QUS parameters were estimated from the backscatter coefficient [effective scatterer diameter (ESD) and effective acoustic concentration (EAC)] using a spherical Gaussian scattering model. Significant increases in ESD and decreases in EAC of 20%-40% were observed in the samples over the range of temperatures examined. The results of this study indicate that QUS parameters are sensitive to changes in temperature. |
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