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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 3 out of 330
| Title |
45,X karyotype: May the diagnosis be suspected on ultrasonic examination in the second trimester of pregnancy? |
| Author |
Tabor A Band J Philip J. |
| Journal |
Prenat Diagn |
| Volume |
|
| Year |
1981 |
| Abstract |
We report three cases of Turner's syndrome with cystic hygromata, which were diagnosed by routine ultrasound scanning before amniocentesis in the second trimester of pregnancy. Maternal and amniotic level of alpha-fetoprotein were normal. Karyotyping carried out afterwards showed a 45,X karyotype. Our data indicate, that cystic hygromata in Turner's syndrome may coexist with a normal amniotic fluid AFP, thus questioning the theory of leakage from the hygroma. It remains to be investigated if all cases of Turner's syndrome present a cystic hygroma in utero. |
| Title |
500-element ultrasound phased array system for noninvasive focal surgery of the brain: A preliminary rabbit study with ex vivo human skulls. |
| Author |
Hynynen K, Clement GT, McDannold N, Vykhodtseva N, King R, White PJ, Vitek S, Jolesz FA. |
| Journal |
Magn Reson Med |
| Volume |
|
| Year |
2004 |
| Abstract |
The aim of this study was to test a prototype MRI-compatible focused ultrasound phased array system for trans-skull brain tissue ablation. Rabbit thigh muscle and brain were sonicated with a prototype, hemispherical 500-element ultrasound phased array operating at frequencies of 700-800 kHz. An ex vivo human skull sample was placed between the array and the animal tissue. The temperature elevation during 20-30-sec sonications was monitored using MRI thermometry. The induced focal lesions were observed in T2 and contrast-enhanced T1-weighted fast spin echo images. Whole brain histology evaluation was performed after the sonications. The results showed that sharp temperature elevations can be produced both in the thigh muscle and in the brain. High-power sonications (600-1080 W) produced peak temperatures up to 55 degrees C and focal lesions that were consistent with thermal tissue damage. The lesion size was found to increase with increasing peak temperature. The device was then modified to operate in the orientation that will be used in the clinic and successfully tested in phantom experiments. As a conclusion, this study demonstrates that it is possible to create ultrasound-induced lesions in vivo through a human skull under MRI guidance with this large-scale phased array. |
| Title |
510(k) guide for measuring and reporting acoustic output of diagnostic ultrasound medical devices. |
| Author |
Barron J, Christman C, Harris G, Shombert D, Smith S, Parrish M, Pollard C. |
| Journal |
Rep Cent Devices Radiol Health |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
| Title |
A 100-MHz ultrasound imaging system for dermatologic and ophthalmologic diagnostics. |
| Author |
Passmann C, Ermert H. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1996 |
| Abstract |
A major design problem concerning high-frequency broad-band ultrasound imaging systems is caused by the strong dispersive attenuation of the tissue, which gives rise to images with inhomogeneous resolution and poor signal to noise ratio (SNR). To address the noise problem, strongly focused transducers with high energy density in a narrow focal region are utilized, which also provide more isotropic images due to improved lateral resolution. To account for the short depth of the focal area two suitable imaging conceptions are used: 1) synthetic aperture concept and 2) B/D-scan concept. To avoid the inhomogeneity of the images, different transmitter signals for each depth are applied, which are pseudoinversely prefiltered according to the transfer function of the tissue. To gain signal energy required of inverse filtering, a pulse compression technique with nonlinearity frequency modulated chirp signals is utilized. These procedures have been implemented in an ultrasound imaging system, which has been developed in our laboratory for eye and skin examinations. It can be used with transducers in a frequency range from 20 to 250 MHz. |
| Title |
A 25 MHz digital acquisition system and applications to diagnostic ultrasound. |
| Author |
Banjavic RA, Thieme GA, Carson PL, Meyer CR, Krasovec JJ. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1981 |
| Abstract |
A 25 megasample per second digital date acquisition system with sampling controls designed for ultrasound applications is described. New test methods demonstrating system analog-to-digital conversion accuracy are presented. Interfacing of the system to a compound B-mode scanner is described, and B-mode images with corresponding digitized RF waveforms are presented for a tissue-equivalent phantom. |
| Title |
A 256-element ultrasonic phased array system for the treatment of large volumes of deep seated tissue. |
| Author |
Daum DR, Hynynen K. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1999 |
| Abstract |
A 256-element phased array has been designed, constructed, and tested for ablative treatment of large focal volumes of deep seated tissue. The array was constructed from a 1.1-MHz, 1-3 composite piezoelectric spherical shell with a 10-cm radius of curvature and a 12-cm diameter. The array was tested to determine its electroacoustic efficiency and inter-element coupling under high acoustic power conditions. A series of in vivo porcine experiments demonstrated the ability to produce deep seated tissue lesions in thigh muscle using the large scale phased array. The array was used to heat and coagulate tissue volumes >5 cm3 in a single ultrasound exposure using multiple foci and temporally scanned power deposition patterns. The spatial and temporal experimental results for large, heated focal volumes correlated very well with the simulated temperature response model for homogeneous tissue. A 25-cm3 tissue volume was coagulated in a 90-min period using overlapping large ultrasound exposures |
| Title |
A 45 to 55 MHz needle-based ultrasound system for invasive imaging. |
| Author |
Lockwood GR, Ryan LK, Foster FS. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1993 |
| Abstract |
The design, construction and fabrication of a high frequency needle-based ultrasound imaging system is described. A miniature lead zirconate titanate transducer was mounted opposite a parabolic mirror in a stainless steel needle. By inserting the needle into a tissue, a cross section image of the tissue can be made. Two needle probes were built, a 45 MHz 2.8 mm diameter probe with 125 microns lateral, 55 microns axial resolution and a 55 MHz 1.6 mm diameter probe with 105 microns lateral, 40 microns axial resolution. Preliminary phantom and in vitro tissue images demonstrate the feasibility of high frequency needle-based imaging. |
| Title |
A 5-year research and development agendum for ultrasonic imaging diagnostic instrumentation. .An assessment of selected medical instrumentation. |
| Author |
Busser JH. |
| Journal |
Rep AEMB |
| Volume |
|
| Year |
1975 |
| Abstract |
A priority list of research and development objectives in medical ultrasound has been assembled to indicate needed development of new capabilities in diagnosis over the next 5 years. Detailed rationale and the complex relationships between issues are given. The four previously published, discipline-orientated reports, from which the list was developed, are included in full as appendices. Thus, a complete background of informtion is provided for decision making in this field. The useful life of the report is expected to extend over a 3-5 year period. |
| Title |
A basic study on sonoporation with microbubbles exposed to pulsed ultrasound. |
| Author |
Okada K, Kudo N, Niwa K, Yamamoto K. |
| Journal |
J Med Ultrasonics |
| Volume |
|
| Year |
2005 |
| Abstract |
Purpose Sonoporation is an ultrasound technique that enables large molecules that normally do not penetrate the cell membrane to pass through it. Recent studies show that pulsed ultrasound in the presence of microbubbles increases the permeability of the cell membrane. However, the mechanism and basic properties of this sonoporation remain unclear. We thus investigated the mechanism of generation and frequency of occurrence of sonoporation, as well as the repair of a cell membrane damaged by microbubbles.
Methods The spatial relationship between microbubbles and cells was observed microscopically when cells were sonicated with pulsed ultrasound. Effects of microbubbles on the cells were observed with a high-speed camera, and the ratio of cell membrane damage and repair was examined using fluorescent microscopy.
Results Damage to the cell membrane, caused mainly by mechanical effects of the expansion and contraction of microbubbles, significantly increased the permeability of the cell membrane. The frequency of cell membrane damage was closely associated with the presence of microbubbles and increased with increase in acoustic pressure. The ratio of repair of damaged cells was about 70% during 3thinspmin after a single shot of pulsed ultrasound, indicating that repair of damaged cell membranes requires little time.
Conclusion We examined the frequency of occurrence of cell membrane damage and repair in sonoporation using pulsed ultrasound and microbubbles. Our results should prove useful for improving pulsed-ultrasound sonoporation. |
| Title |
A Bayesian latent variable mixture model for longitudinal fetal growth. |
| Author |
Slaughter JC, Herring AH, Thorp JM. |
| Journal |
Biometrics |
| Volume |
|
| Year |
2009 |
| Abstract |
Fetal growth restriction is a leading cause of perinatal morbidity and mortality that could be reduced if high-risk infants are identified early in pregnancy. We propose a Bayesian model for aggregating 18 longitudinal ultrasound measurements of fetal size and blood flow into three underlying, continuous latent factors. Our procedure is more flexible than typical latent variable methods in that we relax the normality assumptions by allowing the latent factors to follow finite mixture distributions. Using mixture distributions also permits us to cluster individuals with similar observed characteristics and identify latent classes of subjects who are more likely to be growth or blood flow restricted during pregnancy. We also use our latent variable mixture distribution model to identify a clinically meaningful latent class of subjects with low birth weight and early gestational age. We then examine the association of latent classes of intrauterine growth restriction with latent classes of birth outcomes as well as observed maternal covariates including fetal gender and maternal race, parity, body mass index, and height. Our methods identified a latent class of subjects who have increased blood flow restriction and below average intrauterine size during pregnancy. These subjects were more likely to be growth restricted at birth than a class of individuals with typical size and blood flow. |
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