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BRL Abstracts Database |
Your search for ultrasound produced 3296 results. Page 205 out of 330
Title |
Propagation of ultrasonic waves through demineralized cancellous bone. |
Author |
Mohamed MM, Shaat LT, Mahmoud AN. |
Journal |
IEEE Trans UFFC |
Volume |
|
Year |
2003 |
Abstract |
Ultrasonic velocity is determined in a number of bovine cancellous (spongy) bone samples by using a double-probe-through-transmission ultrasonic pulse technique. The ultrasonic velocity, total mineral content, bone density, and solid volume fraction of the specimen were determined. The relation between fast velocity and each of the other parameters was examined to explore the best correlation using linear, logarithmic, power, and exponential relationships. There is a strong positive relationship between ultrasonic velocity and each of the other parameters. The exponential model fits the data better than the linear model, logarithmic model, and power model. Biot's theory also is used to predict the velocity of ultrasound in the demineralized bone. It is shown that the transmission of ultrasonic pulses in the cancellous bone samples can be adequately described using Biot's theory. The different parameters occurring in the Biot theory have been measured independently, and the calculation has been compared with measured velocity of water-saturated bone samples. The correlation coefficients for regression analysis between the experimental velocities and those predicted by Biot's theory are greater than 0.86. |
Title |
Propagation of ultrasound in tissue. |
Author |
Carstensen EL. |
Journal |
J Acoust Soc Am |
Volume |
|
Year |
1974 |
Abstract |
In spite of extensive applications of ultrasound in diagnosis, therapy, and even surgery, there are still many problems to be solved in the basic physics of sound propagation in tissues. Sound absorption occurs primarily at the macromolecular level. There is evidence to indicate that this absorption can be profoundly modified by macromolecular interaction. The specific physical or chemical relaxation mechanisms responsible for the absorption are unknown. The macroscopic inhomogeneities in tissue affect sound propagation and can lead to artifacts in certain methods of measurement of tissue absorption. The problem of localized heating at interfaces and the question of linearity require investigation. |
Title |
Propagation properties of ultrasound in acoustic microscopy through a double-layered specimen consisting of thin biological tissue and its holder. |
Author |
Tanaka M, Ohkawai H, Chubachi N, Kushibiki J, Sannomiya T. |
Journal |
Jpn J Appl Phys |
Volume |
|
Year |
1984 |
Abstract |
In transmission mode SAM, a biological tissue section to be examined is usually mounted on a polyester film holder to compose a double-layered specimen. In this paper, a one dimensional acoustic model for double layers composed of the mounting holder and a tissue section is investigated to discuss the propagation properties through the specimen quantitatively. It has been basically clarified that variations of brightness in the amplitude image correspond to those in acoustic absorption and that variations of brightness in the phase image correspond to those in sound speed in the tissue section. |
Title |
Propagation speed of sound assessment in the layers of the guinea-pig esophagus in vitro by means of acoustic microscopy. |
Author |
Assentoft JE, Gregersen H, O'Brien WD Jr. |
Journal |
Ultrasonics |
Volume |
|
Year |
2001 |
Abstract |
The study’s purpose was to evaluate the propagation speed of sound in the tissue layers of the esophagus at various mechanical loadings. Scanning laser acoustics microscopy was applied for the estimation of the propagation speed in the mucosa–submucosa and muscle layers of guinea-pig esophagus in vitro (n=26). The propagation speed in the esophagus was determined in the no-load state with all external forces removed, and in the distended and zero-stress states. The zero-stress state was obtained by cutting the esophageal rings radially. The propagation speed in the no-load state differed significantly (p<0.001) between the muscle layer (median 1740, quartiles 1735–1746 m/s) and the mucosa (1607, 1605–1609 m/s). In the distended state the propagation speed in the muscle layer decreased significantly (p<0.001) to 1673 (1666–1681) m/s while it did not change significantly in mucosa (1602, 1600–1607 m/s). When compared to the no-load state, the propagation speed in the zero-stress state in the muscle layers decreased to 1624 (1615–1636) m/s (p<0.001) and in mucosa to 1584 (1566–1603) m/s (p<0.001). In conclusion, the esophagus is a composite structure with heterogeneous propagation speed characteristics. Furthermore, the mechanical loading state must be considered in esophageal ultrasound studies. |
Title |
Properties observed in cataracts produced experimentally with ultrasound. |
Author |
Coleman DJ, Lizzi FL, Burt WJ, Wen H. |
Journal |
Am J Ophthalmol |
Volume |
|
Year |
1971 |
Abstract |
The use of externally applied ultrasound to soften lens material in order to facilitate aspiration was suggested by high frequency mechanical aspirating methods. In vivo rabbit lenses were used to study the possible softening of lens material after application of continuous-wave ultrasonic irradiation. The lenses were followed for periods up to 60 days. The lens material became hard and even calcific during this time, apparently due to the mechanical and heating effects of ultrasonic irradiation. The use of externally applied ultrasonic irradiation at the frequency, powers, and durations specified, as a means of softening lens material prior to aspiration, does not appear clinically feasible at this time. |
Title |
Proposed standard thermal test object for medical ultrasound. |
Author |
Shaw A, Pay NM, Preston RC, Bond AD. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1999 |
Abstract |
A general design for a thermal test object (TTO) is proposed. A number of novel features make the design particularly suitable for.use as a standardised device for assessing the heating capability of diagnostic ultrasound beams. To assess performance,.soft-tissue TTOs have been made containing thin-film thermocouples sandwiched between discs of tissue-mimicking gel. Installed.in an appropriate measurement system, these TTOs exhibit excellent thermal and spatial resolution, allowing the ultrasound beam.to be located rapidly and reproducibly. The measured temperature rise after 3 minutes of heating has been compared with.theoretical predictions based on measured pressure distributions, and agreement is within 10%. Other studies have shown that.soft-tissue- and bone-mimicking TTOs can be used to evaluate a wide range of ultrasound fields and that different physical tissue.models can be simulated. It is concluded that this design would be suitable for providing reference assessments of the thermal.hazard posed by diagnostic ultrasound under standardised conditions. . |
Title |
Prospects and limitations of diagnostic ultrasound. |
Author |
Von Ramm OT, Smith SW. |
Journal |
Proc SPIE |
Volume |
|
Year |
1979 |
Abstract |
The current state of medical diagnostic ultrasound imaging is analyzed including discussions of present limitations and possible solutions of these problems. Ultrasound is unique in that tomographic images are formed from mechanical energy reflected from tissue interfaces of differing acoustic impedance. The low propagation velocities of ultrasound (1540 m/sec) coupled with the range of diagnostic frequencies (1-30 MHz) result in excellent image resolution (2mm multiplied by 2mm) and permit electronic signal processing to achieve portable real time dynamically focused scanning systems at relatively low cost. Diagnostic ultrasound is applied in obstetrics, cardiology, abdominal imaging and ophthalmologY but its versatility is limited by the physical characteristics of tissue. Research is ongoing to improve resolution by adaptive imaging techniques, and parallel processing will hopefully increase data acquisition. These improvements depend heavily on advances in electronics technology. |
Title |
Protein synthesis by neuroblastoma cells is enhanced by exposure to burst-mode ultrasound cavitation. |
Author |
Edmonds PD, Ross P. |
Journal |
Ultrasound Med Biol |
Volume |
|
Year |
1988 |
Abstract |
We observed enhancement of protein synthesis, compared to control cells, 24 h after exposing C1300 neuroblastoma cells (N2A) in rotating tubes at 37 degrees C to 1-MHz ultrasound tone bursts [1:1; durations from 6 to 600 ms; 3.4 W/cm2 spatial-peak burst-average intensity; 5 min total treatment duration (on + off periods)]. Protein synthesis was measured by uptake of 3H-leucine and normalized for cell proliferation by measured uptake of 14C thymidine. The similarity between results for enhanced cavitation-stimulated iodine-release reported by Ciaravino and our results for cellular protein synthesis suggests that cavitation causes this biological effect. |
Title |
Proton Beam Irradiation and Hyperthermia: Effects on experimental choroidal melanoma. |
Author |
Riedel KG, Svitra PP, Seddon JM, Albert DM, Gragoudas ES, Koehler AM, Coleman DJ, Torpey J, Lizzi FL, Driller J. |
Journal |
Arch Ophthalmol |
Volume |
|
Year |
1985 |
Abstract |
Ultrasonically induced hyperthermia (4.75 MHz) and proton irradiation (160 meV) were evaluated alone and combined to treat experimental choroidal melanoma in 58 rabbit eyes. Threshold tumoricidal doses were established for each modality. Therapy was performed combining subthreshold doses of heat and radiation. Focused ultrasonic energy via an external beam was found to deliver well-localized heat to an intraocular tumor. Ectopic temperature elevations due to soft-tissue-bone interfaces were alleviated by modifying beam alignment. The results indicate that hyperthermia (43 degrees C for one hour) potentiated the tumoricidal effects of radiation, while sparing normal ocular structures. Therefore, we believe that experimental hyperthermia is suitable as an adjuvant treatment modality. This shows that ultrasound hyperthermia has the potential to increase the efficacy of proton irradiation by lowering radiation doses and thus decreasing posttreatment ocular morbidity in human intraocular malignancies.
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Title |
Proton transfer at side chain groups: A mechanism for the absorption of ultrasound in protein solutions. |
Author |
Hussey M. |
Journal |
Thesis(PhD): Univ of Pennsylvania |
Volume |
|
Year |
1970 |
Abstract |
No Abstract Available. |
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