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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 71 out of 330
| Title |
Comparison of ultrasound irradiation of pregnant mice with other bioeffects data. |
| Author |
Fry FJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1995 |
| Abstract |
No abstract available. Letter to the editor-in-chief. |
| Title |
Comparison of ultrasound tomography methods in circular geometry. |
| Author |
Leach RR,Jr. Azevedo SG, Berryman JG, Bertete HR, Chambers DH, Mast JE, Littrup P, Duric N, Johnson SA, Wuebbeling F. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2002 |
| Abstract |
Extremely high quality data was acquired using an experimental ultrasound scanner developed at Lawrence Livermore National Laboratory using a 2D ring geometry with up to 720 transmitter/receiver transducer positions. This unique geometry allows reflection and transmission modes and transmission imaging and quantification of a 3D volume using 2D slice data. Standard image reconstruction methods were applied to the data including straight-ray filtered back projection, reflection tomography, and diffraction tomography. Newer approaches were also tested such as full wave, full wave adjoint method, bent-ray filtered backprojection, and full-aperture tomography. A variety of data sets were collected including a formalin-fixed human breast tissue sample, a commercial ultrasound complex breast phantom, and cylindrical objects with and without inclusions. The resulting reconstruction quality of the images ranges from poor to excellent. The method and results of this study are described including like-data reconstructions produced by different algorithms with side-by-side image comparisons. Comparisons to medical B-scan and x-ray CT scan images are also shown. Reconstruction methods with respect to image quality using resolution, noise, and quantitative accuracy, and computational efficiency metrics will also be discussed. |
| Title |
Compilation of reported biological effects data and ultrasound exposure levels. |
| Author |
Stewart HD, Stewart HF, Moore RM Jr, Garry J. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1985 |
| Abstract |
A compilation of reports of biological effects and related ultrasound exposure levels can be useful in the identification of trends in effects data that may be developing in the literature. The exposures in the experiments reviewed were at frequencies used in medicine. For short (10 minutes or less) continuous wave exposure, with the exception of behavioral effects where variable results have been observed, this tabulation did not identify any in vivo or in vitro effects at spatial peak, temporal average (SPTA) intensities less than 100 mW/cm2. However, a number of effects using pulsed sources with SPTA intensities under this level have been reported. There are several frequently recurring topics in recent reports which include developmental effects and microstructure changes at the cellular level. In addition to animal investigations, there are some limited human epidemiological studies reporting an association between medical ultrasound exposure in utero and developmental effects. Although sufficient research has not been completed to draw conclusions, the findings deserve further investigation. A systematic pattern of directed research on a large scale is not apparent. The available data consist of many scattered studies conducted by individual investigators and groups throughout the world. |
| Title |
Compressibility of colloids. 1. Compressibility studies of aqueous solutions of amphiphilic polymers and their adsorbed state on polystyrene latex dispersions by ultrasonic velocity measurements. |
| Author |
Barrett-Gultepe MA, Gultepe ME, Yeager EB. |
| Journal |
J Phys Chem |
| Volume |
|
| Year |
1983 |
| Abstract |
Sound velocity measurements were made to obtain compressibility values at 2 MHz and to investigate the influence of the interface in dispersions of electrostatically stabilized colloidal particles. The measurements were made on two different aqueous dispersions of polystyrene latices as a function of volume concentration up to 49% and temperature up to 80 degrees C (approaching the glass transition temperature of polystyrene) and in solutions of 72.5% and 78% hydrolyzed poly(vinyl alcohol)-poly(vinyl acetate) block copolymers (PVA) as a function of temperature above and below their cloud points. The measurements were extended to latices covered with PVA samples. These dispersions give a resultant compressibility lower than expected from a simple additive effect of the separate components at 25 degrees C and higher. The decrease in compressibility may be due to either or both of two effects: (i) the hydrophobic interaction between the acetate groups and the polymer backbone of polystyrene latex results in a more rigid structure, and (ii) the suppression by the PVA coating of the association-dissociation type surface chemical reaction responsible for the remarkably high adsorption of ultrasound will result in a lower compressibility. |
| Title |
Computation of local directivity, speed of sound attenuation from ultrasonic reflection tomography data. |
| Author |
Bartlet H. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1988 |
| Abstract |
Ultrasound reflection tomography based on the compound scan principle, allows one to produce reflectivity images with high quality and reproducibility. In this paper, methods are discussed on how to extract additional physical parameters from the same set of reflection data for medical applications. Experimental results from a phantom object and in-vivo measurements illustrate the capabilities of such tomographic reflection systems. |
| Title |
Computationally efficient algorithms for control of ultrasound phased-array hyperthermia applicators based on a pseudoinverse method. |
| Author |
Wang H, Ebbini E, Cain CA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1990 |
| Abstract |
Computationally efficient incremental algorithms for application of the pseudoinverse method for ultrasound phased array field pattern synthesis are discussed and shown to significantly reduce computing effort when more control points should be added to existing subsets of points previously manipulated. Also these algorithms avoid calculation of inverse matrices, a time consuming job for microcomputers when the dimensions of the matrices are large. This technique can be used to recursively modify the heating patterns of a phased-array hyperthermia applicator in the clinic. |
| Title |
Computed estimates of maximum temperature elevations in fetal tissues during transabdominal pulsed doppler examinations. |
| Author |
Bly SH, Vlahovich S, Mabee PR, Hussey RG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1992 |
| Abstract |
Measured characteristics of ultrasonic fields were obtained in submissions from manufacturers of diagnostic ultrasound equipment for devices operating in pulsed Doppler mode. Simple formulae were used with these data to generate upper limits to fetal temperature elevations, delta Tlim, during a transabdominal pulsed Doppler examination. A total of 236 items were analyzed, each item being a console/transducer/operating-mode/intended-use combination, for which the spatial-peak temporal-average intensity, ISPTA, was greater than 500 mW cm-2. The largest calculated delta Tlim values were approximately 1.5, 7.1 and 8.7 degrees C for first-, second- and third-trimester examinations, respectively. The vast majority of items yielded delta Tlim values which were less than 1 degree C in the first trimester. For second- and third-trimester examinations, where heating of fetal bone determines delta Tlim, most delta Tlim values were less than 4 degrees C. The clinical significance of the results is discussed. |
| Title |
Computed sonography. |
| Author |
Maslak SH. |
| Journal |
Ultrasound Annual |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
| Title |
Computer aided diagnosis of parotid gland lesions using ultrasonic muti-feature tissue characterization. |
| Author |
Siebers S, Zenk J,Bozzato A, Klintworth N, Iro H, Ermert H. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2010 |
| Abstract |
In this article, an ultrasound based system for computer aided characterization of biologic tissue and its application to differential diagnosis of parotid gland lesions is proposed. Aiming at an automated differentiation between malignant and benign cases, the system is based on a supervised classification using tissue-describing features derived from ultrasound radio-frequency (RF) echo signals and image data. Standard diagnostic ultrasound equipment was employed to acquire ultrasound RF echo data from parotid glands of 138 patients. Lesions were manually demarcated as regions-of-interest (ROIs) in the B-mode images. Spectral ultrasound backscatter and attenuation parameters are estimated from diffraction corrected RF data, yielding spatially resolved parameter images. Histogram based statistical measures derived from the parameters distributions inside the ROI are used as tissue describing features. In addition, texture features and shape descriptors are extracted from demodulated ultrasound image data. The features are processed by a maximum likelihood classifier. An optimal set of 10 features was chosen by a sequential forward selection algorithm. The classifier’s performance is evaluated using total cross validation and receiver operating characteristic (ROC) analysis. As a reference method, postoperative pathohistologic analysis was conducted and proved malignancy or prospective malignancy in 51 patients. The classification using the proposed system yielded an area under the ROC curve of 0.91, proving significant potential for differentiating between malignant and benign parotid gland lesions. |
| Title |
Computer model of ultrasonic hyperthermia and ablation for ocular tumors using B-mode data. |
| Author |
Lizzi FL, Driller J, Lunzer B, Kalisz A, Coleman DJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1992 |
| Abstract |
Computer simulations have been conducted to examine hyperthermia and ablation for treating ocular tumors. An interactive software package has been implemented that permits relevant tissue dimensions to be determined from B-mode data. This package also permits interactive beam positioning, and it provides image displays depicting computed absorbed doses and temperature rises. Results are presented showing how hyperthermia temperature patterns are influenced by beam position, beam geometry and frequency. Images showing ablative temperature rises at various time intervals are also presented. For hyperthermia, geometric models of beam profiles showed that a non-uniform beam pattern (with a central low-intensity region) can produce more uniform heating of small ocular tumors than a beam with a uniform intensity profile. For a given tumor, the uniformity of hyperthermia temperatures was found to be a function of frequency, with 4.75 MHz providing reasonably uniform results for typical tumor heights (near 7 mm). For ablation, diffraction computations were employed to calculate beam intensity profiles; results show an initially rapid rise in temperature levels with subsequent, slower heating beyond the -3-dB limits of the focal volume. The model is now being refined, and additional phenomena, including nonlinear propagation, will be incorporated. |
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