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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 72 out of 330
| Title |
Computer processing of line mode echogram data. |
| Author |
Robinson DE, Kossoff G. |
| Journal |
Proc Second Meet World Fed Ultrasound Med Biol - Miyazaki |
| Volume |
|
| Year |
1979 |
| Abstract |
No abstract available. |
| Title |
Computer simulation of measurement of ultrasound attenuation coefficient by broad band continuous-echo technique (gamma variate method). |
| Author |
Hayakawa Y, Tada JI, Inada T. |
| Journal |
Jpn J Appl Phys |
| Volume |
|
| Year |
1989 |
| Abstract |
Computer simulation experiments were made using the gamma variate method. The method is one proposed by the authors and uses a broad band interrogating wave. The interrogating wave was assumed to be delta function in time scale. Five random scatterers at distances of 90 and 100 mm from the transducer were assumed. An atteunation coefficient proportional to the frequency (0.01 Np/mm/MHz) was also assumed. Frequencies between 0.2 and 3.2 MHz were used for the analysis. The averaged spectrum of 300 simulation experiments gave 0.00996 Np/mm/MHz which was approximately equal to the assumed value. |
| Title |
Computer simulation to evaluate strategies for enhancing accuracy in attenuation tomography. |
| Author |
Brandenburger GH, Cox JR, Klepper JR, Miller JG. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1982 |
| Abstract |
Computer simulation offers the potential for segregating, characterizing, and evaluating strategies for overcoming sources of error in tomographic reconstructions. A computer model was used to simulate the generation, propagation, and detection of ultrasound. The transmitted beam was modeled as a superposition of 100 rays, each having a frequency dependent amplitude, phase, and trajectory in order to achieve a Bessel function-like beam. A soft tissue-like medium was modeled as a collection of regions, each exhibiting a velocity, mass density, and frequency dependent ultrasonic attenuation. Simulations illustrate the use of a phase insensitive receiver of relatively large aperture, positioned relatively close to the specimen to capture a substantial fraction of the refracted beam. Reconstruction of the slope of the attenuation to reduce refraction and reflection effects, with compensation for the frequency dependence of the width of the insonifying ultrasonic beam prior to calculating the slope, is illustrated. |
| Title |
Computer-based margin analysis of breast sonography for differentiating malignant and benign masses. |
| Author |
Sehgal CM, Cary TW, Kangas SA, Weinstein SP, Schultz SM, Arger PH, Conant EF. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
2004 |
| Abstract |
Objective. To evaluate the role of quantitative margin features in the computer-aided diagnosis of malignant and benign solid breast masses using sonographic imaging. Methods. Sonographic images from 56 patients with 58 biopsy-proven masses were analyzed quantitatively for the following features: margin sharpness, margin echogenicity, and angular variation in margin. OF the 58 masses, 38 were benign and 20 were malignant. Each feature was evaluated individually and incombination with the others to determine its association with malignancy. The combination of features yielding the highest association with malignancy was analyzed by logistic regression to determine the probability of malignancy. The performance of the probability measurements was evaluated by receiver operating characteristic analysis using a round-robin technique. Results. Margin sharpness, margin echogenicity, and angular variation in margin were significantly different for the malignant and benign masses (P < .03, 2-tailed Student t test). According to quantitative measures, tumor-tissue margins of the malignant masses were less distinct than for the benign masses. Although he mean size of the lesions for the two groups was the same, the mean age of the patients was statistically different (P- .000625). After logistic regression analysis, the individual features age, margin sharpness, margin echogenicity, and the angular variation in margin were found to be associated with the probability of malignancy (P < .03). The area under the receiver operating characteristic curve +/- SD for the 3-feature logistic regression model combining age, margin echogenicity, and angular variation of margin was 0.87 +/- 0.05. Conclusions. The proposed quantitative margin features are robust and can reliably measure margin distinctiveness. These features combines with logistic regression analysis can be useful for computer-aided diagnosis of solid breast lesions. |
| Title |
Computerized tomography using ultrasound: System design. |
| Author |
Fish, RM, O'Brien WD Jr. |
| Journal |
Carle Selected Papers |
| Volume |
|
| Year |
1979 |
| Abstract |
Virtually all the computerized tomography scanners in clinical use at the present time utilize x-rays. The system described in this paper uses ultrasound instead, thus eliminating x-ray exposure. The images obtained depend on the tissue properties such as the absorption of ultrasound, rather than x-ray density.
Living tissues can be characterized by their interaction with ultrasound. OUr research involves measuring the frequency-dependent amplitude and time-of-flight of ultrasound after it passes through biological materials. These measurements are processed to produce tomographic images of the material being studied. The tomographic images yield resolutions of 0.5 cm in the low MHz ultrasonic frequency range.
This paper describes the data-acquisition circuitry of a computerized tomography system, as part of a joint effort with Mayo Clinic (J.F. Greenleaf) and Purdue University (Z.C. Kak). A block diagram of the system is given in Fig 1. |
| Title |
Computerized tomography with X-ray, emission, and ultrasound sources. |
| Author |
Kak AC. |
| Journal |
Proc IEEE |
| Volume |
|
| Year |
1979 |
| Abstract |
This paper reviews the major developments that have taken place during the last three years in imaging with computed tomography (CT) using X-ray, emission, and ultrasound sources. Space limitations have resulted in some selection of topics by the author. There are four major sections dealing with algorithms,X-ray CT, emission CT, and ultrasound CT. Since most of the currently used algorithms are of filtered-backprojection type, we have concentrated on these in the section on algorithms (with emphasis on their implementation aspects). In X-ray CT an important question raised during the last few years has concerned the parameter measured by a CT scanner, given the fact that the X-rays used in CT scanners are polychromatic and the fact that tissue attenuation coefficients are energy dependent. Answers to this question are reviewed in the section on X-ray CT where we have also discussed the artifacts caused by the polychromaticity of the X-ray photons. Methods for the removal of these artifacts have also been reviewed. In emission CT the biggest development of the last three years is the great interest in positron tomography, although space constraints have dictated an essentially introductory treatment and not all aspects of the single photon and positron tomography have been surveyed. Finally, we have reviewed recent developments in ultrasound CT. We have pointed out that because of the sensitivity of this technique to refraction, it is currently limited to soft tissue structures, with ultrasonic detection of tumors in the female breast a significant application. |
| Title |
Computerized ultrasound tomography of the human head: Experimental results. |
| Author |
Dines KA, Fry FJ, Patrick JT, Gilmor RL. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1981 |
| Abstract |
Computerized ultrasound tomograms of infant and adult human cadaver heads are presented and compared to x-ray CT scans obtained in the same horizontal planes. The images were reconstructed from broadband pulsed transmission data obtained using the rotate-translate scan mode. A formalin-fixed infant cadaver head was scanned using a 5 MHz center frequency yielding a transkull attenuation reconstruction which displays enough anatomical detail to warrant continued work on the method with the hope of eventual clinical application.
Further insight has been gained into the possibility of using ultrasound transmission tomography for imaging the adult head. A transkull attenuation reconstruction was performed on an adult cadaver head which was known to contain intracranial gas as revealed by x-ray CT scanning. Despite the obvious problems posed by this gas, the reconstructured image obtained using a 750 kHz center frequency reveals significant features in some specific brain and skull regions.
|
| Title |
Concentric-ring and sector-vortex phased-array applicators for ultrasound hyperthermia. |
| Author |
Cain CA Umemura S. |
| Journal |
IEEE Trans Microw Theory Tech |
| Volume |
|
| Year |
1986 |
| Abstract |
Concentric-ring phased arrays subdivided into sectors (radial slices) can, with appropriate phasing, produce power absorption patterns useful for hyperthermia cancer therapy. The ability of a concentric-ring array to move a focal region along the central axis of the transducer is well known. Less well known is the ability of such an array to produce variable diameter annular (or ring) focal regions. Such focal rings can be effective in heating some tumors if directed around the tumor periphery. These focal rings have been produced in the past by fixed annular focus lenses, or effectively by mechanical scanning of "point" focus ultrasonic transducers. Production of these focal rings by a concentric-ring phased array has the advantage of allowing the focal ring diameter and focal length to be easily changed and scanned by phasing providing much greater heating flexibility. However, under some conditions such arrays produce very large secondary focus effects along the central axis of the amay. Concentric-ring arrays can also provide only patterns of circular symmetry. These problems can be partially solved by dividing the disk of the array into sectors. By appropriate phasing of the sectors, the intensity along the central axis can be greatly reduced. Moreover, appropriate phasing of the rings and sectors can produce patterns that are circularly asymmetric. By controlling these asymmetries, nonspherical tumors can be heated more optimally. Power absorption patterns in Iossy media for this class of applicators are analyzed numerically allowing a quantitative evaluation of both advantages and limitations of this approach. A thermal model based on the bioheat equation is also used to predict temperature distributions in volumes where important thermal parameters, particularly blood flow, are varied. |
| Title |
Conclusions regarding biological effects of ultrasound for diagnostically relevant exposures. |
| Author |
Frizzell LA. |
| Journal |
J Ultrasound Med |
| Volume |
|
| Year |
1994 |
| Abstract |
No abstract available. A meeting report. |
| Title |
Concurrent detection of the production of ultrasonic lesions. |
| Author |
Lele PP. |
| Journal |
Med Biol Eng |
| Volume |
|
| Year |
1966 |
| Abstract |
Irradiation with a single beam of focused ultrasound is currently the method of choice for the production of trackless, focal, pan-necrotic lesions of predetermined size at any desired site within the central nervous system of experimental animals and man. Development of a simple technique using the same transducer for concurrent detection of the production of such lesions is described and the results obtained in a phantom brain are presented. |
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