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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 41 out of 330
| Title |
Apoptosis induction of human myeloid leukemic cells by ultrasound exposure. |
| Author |
Ashush H, Rozenszajn LA, Blass M, Barda-Saad M, Azimov D, Radnay J, Zipori D, Rosenschein U. |
| Journal |
Cancer Res |
| Volume |
|
| Year |
2000 |
| Abstract |
Therapeutic ultrasound (ULS) and the resulting cavitation process has been shown to induce irreversible cell damage. In this study, we wanted to further investigate the mechanism of ULS-induced cell death and to determine whether apoptosis is involved. High intensity focused pulsed ULS sonication at a frequency of 750 KHz was delivered to HL-60, K562, U937, and M1/2 leukemia cell line cultures. ULS exposure used with induction of transient cavitation in the focal area was delivered with an intensity level of 103.7 W/cm2 and 54.6 W/cm2 spatial-peak temporal-average intensity. As a control, ULS of lower intensity was delivered at 22.4 W/cm2 spatial-peak temporal-average intensity, presumably without generation of cavitation. Our results indicated that DNA damage induced by ULS cavitation did not involve generation of free radicals in the culture media. Morphological alterations observed in cells after exposure to ULS included: cell shrinkage, membrane blebbing, chromatin condensation, nuclear fragmentation, and apoptotic body formation. Apoptotic cells were evaluated by fluorescence microscopy and detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, which identifies DNA breaks, and by the leakage of phosphatidylserine from the inner to the outer side of the membrane layer of treated cells. Some bioeffects induced on sonicated HL-60 cells, such as inhibition of cell proliferation, DNA repair, and cell-dependent apoptosis, were found to be similar to those produced by gamma-irradiation. Thus, much of the cell damage induced by therapeutic ULS in leukemia cells surviving ULS exposure appears to occur through an apoptotic mechanism. |
| Title |
Apparatus for the generation of focused ultrasound of high intensity. |
| Author |
Rozenberg LD, Sirotyuk MG. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1959 |
| Abstract |
No abstract available. |
| Title |
Apparatus for ultrasound tissue characterization of excised specimens. |
| Author |
Arditi M, Edmonds PD, Jensen JF, Mortensen CL, Ross WC, Schattner P,.Stephens DN, Vinzant W. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1991 |
| Abstract |
Apparatus is described for measurement of sound speed and ultrasound attenuation coefficients by the substitution technique in the frequency range 3 to 8 MHz. Phase-cancellation artifacts leading to overestimation of attenuation coefficients are avoided by use of an acoustoelectric transducer. Specimens confined by polystyrene windows can be interrogated by focused ultrasound beams at selected locations spaced on a grid of 3 x 3 mm voxels. Pulse time of flight is measured with an accuracy of 30 ns, yielding sound speeds accurate to +/- 6.7 m/s, for samples 10 mm thick. Uncertainties in measured insertion losses range from 0.1 dB in low-loss (10 dB) specimens to 0.5 dB in high-loss (25 dB) specimens. |
| Title |
Apparent and real thresholds for biological effects of ultrasound. |
| Author |
Sarvazyan AP. |
| Journal |
Proc Tenth Int Congr Acoust - Sidney |
| Volume |
|
| Year |
1980 |
| Abstract |
No abstract available. |
| Title |
Applicability of ultrasonic tissue characterization for longitudinal assessment and differentiation of calcification and fibrosis in cardiomyopathy. |
| Author |
Perez JE, Barzilai B, Madaras EI, Glueck RM, Saffitz JE, Johnston P, Miller JG, Sobel BE. |
| Journal |
J Am Coll Cardiol |
| Volume |
|
| Year |
1984 |
| Abstract |
Progress in tissue characterization of myocardium with ultrasound suggests that quantitative recognition of ischemic or scarred tissue will be achieved. Despite the increasing recognition and importance of cardiomyopathy, its diagnosis generally.requires invasive procedures such as cardiac catheterization and biopsy. To investigate methods that permit the characterization of longitudinal cardiomyopathic changes that might ultimately be extended for noninvasive studies in patients, quantitative ultrasonic methods were utilized for in vitro tissue characterization of hearts from Syrian hamsters of selected age of either 2 to 3 or 5 to 7 months. Normal hamsters were used as controls. Myocardial sites (n = 600) from the.young Syrian hamsters exhibited values (+/- standard error) of integrated ultrasonic backscatter averaging -53.87 +/- 0.26 dB, which were significantly different from values (n = 500) in age-matched control hamsters (-58.07 +/- 0.08 dB; p less.than 0.001). Cardiomyopathic hearts from older animals exhibited backscatter values (n = 500 sites) averaging -50.87 +/- 0.22 dB, again significantly different from values (n = 300 sites) in age-matched control hamsters (-55.91 +/- 0.11 dB; p less.than 0.001). In addition, ultrasonic attenuation was significantly different for hearts from the control and cardiomyopathic hamsters of both age ranges. The results correlated with sequential calcification and fibrosis characteristics assessed.histopathologically. This study indicates that quantitative characterization of myocardium with ultrasound may permit longitudinal assessment of cardiomyopathic changes in diverse disease entities and their response to therapy. |
| Title |
Application of an art algorithm in an experimental study of ultrasonic diffraction tomography. |
| Author |
Ladas KT, Devaney AJ. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
|
| Abstract |
This paper describes results obtained using a recently developed Algebraic Reconstruction Technique (ART) for diffraction tomography on experimental data obtained from an ultrasound scanner built by Norwave Development A.S. of Oslo, Norway. The test objects (phantoms) employed in the study are low contrast cylindrical rods made out of agar with dimensions comparable to the wavelength of the incident wavefield. The reconstructions obtained from the ART algorithm are compared to the ones obtained from the filtered backpropagation algorithm. It is determined that the ART algorithm out performs the filtered backpropagation algorithm for cases where data from only a small number of tomographic experiments are available. |
| Title |
Application of an art algorithm in an experimental study of ultrasonic diffraction tomography. |
| Author |
Ladas KT, Devaney AJ. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
|
| Abstract |
This paper describes results obtained using a recently developed Algebraic Reconstruction Technique (ART) for diffraction tomography on experimental data obtained from an ultrasound scanner built by Norwave Development A.S. of Oslo, Norway. The test objects (phantoms) employed in the study are low contrast cylindrical rods made out of agar with dimensions comparable to the wavelength of the incident wavefield. The reconstructions obtained from the ART algorithm are compared to the ones obtained from the filtered backpropagation algorithm. It is determined that the ART algorithm out performs the filtered backpropagation algorithm for cases where data from only a small number of tomographic experiments are available. |
| Title |
Application of autoregressive spectral analysis to cepstral estimation of mean scatterer spacing. |
| Author |
Wear KA, Wagner RF, Insana MF, Hall TJ. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1993 |
| Abstract |
The problem of estimation of mean scatterer spacing in an object containing regularly spaced structures is addressed. An autoregressive (AR) spectral estimation method (based on Burg's algorithm) is compared with a conventional fast Fourier transform (FFT) based approach for this task. Regularly spaced structures produce a periodicity in the power spectrum of ultrasonic backscatter. This periodicity is manifested as a peak in the cepstrum. A phantom was constructed for comparison of the two methods. This phantom contained regularly spaced nylon filaments. In addition, it contained randomly positioned glass spheres that produced incoherent backscatter. In an experiment in which this target was interrogated using broadband ultrasound. The AR spectral estimate offered considerable improvement over the FFT when the analysis gate length was on the order of the structural dimension. Advantages included improved resolution, reduction in bias and variance of scatterer spacing estimates, and greater resistance to ringing artifacts. Data was also acquired from human liver in vivo. AR spectral estimates on human data exhibited a decreased dependence on gate length. These results offer promise for enhanced spatial resolution and accuracy in ultrasonic tissue characterization and nondestructive evaluation of materials. |
| Title |
Application of Golay codes to improve the dynamic range in ultrasonic lamb waves air-coupled systems. |
| Author |
Garcia-Rodriguez M, Yanez Y, Garcia-Hernandez MJ, Salazar J, Chavez JA. |
| Journal |
NDT & E International |
| Volume |
|
| Year |
2010 |
| Abstract |
Air-coupled ultrasonic systems are usually limited by poor signal-to-noise ratios. The use of pulse compression techniques based on Golay codes can help to improve the ultrasound signal-to-noise ratio. This type of codes allows virtually side lobe free operation and causes the cancellation of self-induced noise. This paper proposes the use of Golay sequences to code Lamb waves excited in thin materials with a NDT system based on air-coupled piezoelectric arrays. Furthermore, a system for the generation of Lamb waves modulated by 16-bits Golay codes is also proposed. Successful results are presented in copper plates. An improvement in signal-to-noise ratio up to 21 dB is achieved when compared with conventional pulse transmission. |
| Title |
Application of high-intensity focused ultrasound for the local treatment of biological tissue. |
| Author |
Gavrilov LR. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1972 |
| Abstract |
No abstract available. |
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