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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 216 out of 330
| Title |
Recent progress on standards and bioeffects in Japan. |
| Author |
Maeda K. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1989 |
| Abstract |
Abstract not available. |
| Title |
Recommendations for widespread application of ultrasound visualization techniques for examination of the female breast. |
| Author |
Fry EK, Fry FJ, Gardner GW. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1977 |
| Abstract |
No abstract available. |
| Title |
Recommendations on the subject of ultrasound. |
| Author |
Committee of the health council of the Netherlands. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1986 |
| Abstract |
No abstract available.
|
| Title |
Reconstruction in diffraction ultrasound tomography using nonuniform FFT. |
| Author |
Bronstein MM, Bronstein AM, Zibulevsky M, Azhari H. |
| Journal |
IEEE Trans Med Imaging |
| Volume |
|
| Year |
2002 |
| Abstract |
We show an iterative reconstruction framework for diffraction ultrasound tomography. The use of broad-band illumination allows significant reduction of the number of projections compared to straight ray tomography. The proposed algorithm makes use of forward nonuniform fast Fourier transform (NUFFT) for iterative Fourier inversion. Incorporation of total variation regularization allows the reduction of noise and Gibbs phenomena while preserving the edges. The complexity of the NUFFT-based reconstruction is comparable to the frequency-domain interpolation (gridding) algorithm, whereas the reconstruction accuracy (in sense of the L2 and the L(infinity) norm) is better. |
| Title |
Reconstructive tomography based on ultrasonic attenuation. |
| Author |
Miller JG, Klepper JR, Brandenburger GH, Busse LJ, O'Donnell M, Mimbs JW. |
| Journal |
Ultrasound Med |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Reconstructive ultrasound elasticity imaging for renal pathology detection. |
| Author |
Emelianov SY, Lubinski MA, Skovoroda AR, Erkamp RQ, Leavey SF, Wiggins RC, O'Donnell M. |
| Journal |
Proc IEEE Ultrason Symp |
| Volume |
|
| Year |
1997 |
| Abstract |
The real-time capability of ultrasound is it's major advantage for reconstructive elasticity imaging. In addition to providing important immediate feedback during patient examination, real-time data capture provides an excellent means for retrospective data processing. With retrospective processing, normal axial strain images can be optimized for highest SNR, the accuracy of lateral displacement estimates can be improved, and finally, non-linear elastic properties of tissue can be evaluated resulting in contrast enhancement of elasticity imaging. Retrospective processing requires no new data capture and adds new important features to reconstructive ultrasound elasticity imaging. |
| Title |
Reduced peak-hopping artifacts in ultrasonic strain estimation using the viterbi algorithm. |
| Author |
Petrank Y,Huang L,O'Donnell M. |
| Journal |
IEEE Trans Ultrason Ferroelectr Freq Control |
| Volume |
|
| Year |
2009 |
| Abstract |
Internal strain resulting from tissue deformation can be estimated by correlation processing of speckle patterns within complex (i.e., radio frequency) ultrasound images acquired during deformation. At large deformations, the magnitude of the correlation coefficient peak can be significantly lower than unity, so that random speckle correlations will exceed the true peak. This effect is called "peak hopping" and causes significant errors in displacement and deformation estimates. Here we investigate the Viterbi algorithm, a dynamic programming procedure, to overcome peak-hopping artifacts by finding the most likely sequence of hidden states in a sequence of observed events. It is well suited to motion estimation in elasticity- imaging studies because adjacent tissue elements remain adjacent following deformation. Particularly, tissue elements along an ultrasonic beam in one image lie along a 3-D continuous curve in the next image instant. The observed event in this case is the correlation coefficient of a pixel at a certain displacement. Radio-frequency data were generated before and after deformation with an average strain of 6%. Simulations were performed for a homogenous medium and for a medium with a stiffer inclusion. Results show that Viterbi processing of speckle-tracking outputs can significantly reduce peak-hopping artifacts. |
| Title |
Reduced-order autoregressive modeling for center-frequency estimation. |
| Author |
Kuc R, Li H. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1985 |
| Abstract |
The center frequency of a narrowband, discrete-time random process, such as a reflected ultrasound signal, is estimated from the parameter values of a reduced, second-order autoregressive (AR) model. This approach is proposed as a fast estimator that performs better than the zero-crossing count estimate for determining the center-frequency location. The parameter values are obtained through a linear prediction analysis on the correlated random process, which in this case is identical to the maximum entropy method for spectral estimation. The frequency of the maximum of the second-order model spectrum is determined from these parameters and is used as the center-frequency estimate. This estimate can be computed very efficiently, requiring only the estimates of the first three terms of the process autocorrelation function. The bias and variance properties of this estimator are determined for a random process having a Gaussian-shaped spectrum and compared to those of the ideal FM frequency discriminator, zero-crossing count estimator and a correlation estimator. It is found that the variance values for the reduced-order AR model center-frequency estimator lie between those for the ideal FM frequency discriminator and the zero-crossing count estimator. |
| Title |
Reducing the effects of specular scatterers on QUS imaging using the generalized spectrum. |
| Author |
Luchies A, Ghoshal G, O'Brien WD, Oezle ML. |
| Journal |
IEEE Int Ultrasonics Symp Proc |
| Volume |
|
| Year |
2010 |
| Abstract |
The effective scatterer diameter (ESD) and effective acoustic concentration (EAC) are quantitative ultrasound (QUS) imaging parameters that employ scattering models and spectral fit methods to characterize tissue microstructure. These methods work best when the region of interest (ROI) from which the parameters are derived contains uniform diffuse scatterers. In some tissues, specular scatterers (e.g., calcifications, blood vessels, etc.) can exist and cause decreases in the accuracy and precision of QUS parameter estimates based on diffuse scattering. In this study the generalized spectrum (GS) intercept parameter was used to detect echoes from specular scatterers.The signals corresponding to the specular scatterers were then removed in order to reduce the effect of specular scatterers on QUS estimates. Backscatter data from a simulated phantom, rat mammary tumors, and fresh beef liver samples that underwent elevations in temperature were analyzed to evaluate the effectiveness of using the GS intercept parameter. The ESD and EAC were estimated assuming a spherical Gaussian scattering model for each data block outlined in an ROI in the sample. The GS intercept parameter was estimated for each data block and used to sort data blocks and their corresponding QUS estimates were sorted into diffuse and specular scattering groups. Modified parametric images were then formed by using only the data blocks in the diffuse scattering group. For the simulated phantom, the exclusion of specular scatterers from the QUS estimates resulted in a reduction in ESD standard deviation of 66.4%. For the rat mammary tumors, the average reduction in ESD and EAC standard deviation was 17.1% and 24.8%, respectively. When monitoring the changes in ESD and EAC in beef liver samples versus temperature over the temperature range of 37 to 50 °C, the mean ESD and EAC values changed monotonically with temperature. By excluding the specular scatterers, ESD and EAC were observed to change by 25.4% and -40.3% respectively as opposed to 14.8% and -30.7% respectively when including specular scatterers. When excluding specular scatterers from QUS analysis, the precision of QUS estimates was improved and the sensitivity of QUS estimates to
temperature changes was increased. These results suggest that the GS intercept parameter has the potential to reduce the effects of specular scatterers on diffuse scattering estimates and to improve QUS imaging. |
| Title |
Reduction in mitotic index in Pisum sativum root meristems by pulsed ultrasound irradiation. |
| Author |
Arcuri KB, Pizzutiello RJ, Miller MW, Kaufman GE, Carstensen EL. |
| Journal |
Radiat Res |
| Volume |
|
| Year |
1976 |
| Abstract |
The effect of continuous-wave and pulsed 2 MHz ultrasound at an intensity of 10 W/cm(2) on the mitotic index of Pisum sativum root meristems was investigated. The duty factor of the pulses was 1 on to 9 off, and the on times ranged from 1 min to 3 (moon)sec. In all cases the total irradiation (?on?) time was 1 min. The ultrasound produced a reduction in the mitotic index at all pulse lengths. The shorter pulse lengths (3 and 10 (moon)sec) were less effective in reducing mitotic index than were the longer pulse lengths. Acoustic cavitation is suggested as a mechanism partially causing this nonthermal effect. |
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