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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 279 out of 330
| Title |
Tissue mimicking materials for dental ultrasound. |
| Author |
Singh RS, Culjat MO, Grundfest WS, Brown ER, White SN. |
| Journal |
Med Phys |
| Volume |
|
| Year |
1978 |
| Abstract |
While acoustic tissue mimicking materials have been explored for a variety of soft and hard biological tissues, no dental hard tissue mimicking materials have been characterized. Tooth phantoms are necessary to better understand acoustic phenomenology within the tooth environment and to accelerate the advancement of dental ultrasound imaging systems. In this study, soda lime glass and dental composite were explored as surrogates for human enamel and dentin, respectively, in terms of compressional velocity, attenuation, and acoustic impedance. The results suggest that a tooth phantom consisting of glass and composite can effectively mimic the acoustic behavior of a natural human tooth. |
| Title |
Tissue mimicking materials for ultrasound phantoms. |
| Author |
Madsen EL, Zagzebski JA, Banjavie RA, Jutila RE. |
| Journal |
Med Phys |
| Volume |
|
| Year |
1978 |
| Abstract |
Up until now, no material has been found whose attenuation and speed of sound properties not only mimic those of human soft tissue, but are controllable in magnitude. We have discovered such a material in the form of water-based pharmaceutical gels containing uniform distributions of graphite powder and known concentrations of alcohol. The magnitude of the attenuation coefficient can be controlled easily between 0.2 and 1.5 dB/cm at 1 MHz, by varying the concentration of graphite. These attenuation coefficients are nearly proportional to the frequency. The speed of sound varies between 1520 and 1650 m/s at room temperature, depending primarily upon the concentration of alcohol. Bacterial invasion has been prevented by sterilization procedures and the introduction of appropriate preservatives. The ultrasonic properties exhibit temporal stability and change little over the range of room temperatures. |
| Title |
Tissue motion analysis of digitized B-scan images of breast tumors. |
| Author |
Chen E, Adler R, Carson P, Jenkins K, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1995 |
| Abstract |
Palpated tissue motion in patients with both benign and malignant breast disease was quantified from ultrasound B-mode video images using ultrasonic speckle tracking. The displacement response of tissues surrounding benign and malignant breast lesions was compared taking advantage of the altered mechanical properties and thus motion signatures of many tumors relative to their host tissue. Preliminary results indicate that malignant masses drag surrounding tissues when palpated, suggesting infiltration by the tumor into surrounding tissues. Benign breast masses however, exhibited no such dragging. Sample results taken from 8 patients with sonographically apparent breast masses are used to demonstrate the method. |
| Title |
Tissue response to mechanical vibrations for "sonoelasticity imaging". |
| Author |
Parker KJ, Huang SR, Musulin RA, Lerner RM. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1990 |
| Abstract |
The goal of "sonoelasticity imaging" is to differentiate between normal soft tissues and hard lesions. This is done by measuring and then displaying the ultrasound Doppler spectrum of regions within tissues which are mechanically forced with low frequency (20-1000 Hz) vibrations. The resolution and sensitivity of the.technique ultimately rest on the spatial resolution of ultrasound Doppler detection, the low frequency mechanical properties of tissues, and the vibration response of layered, inhomogeneous regions with hard tumor inclusions and complicated boundary conditions set by the presence of skin, bones and other regions..An initial investigation has measured some tissue stiffness parameters, and applied these in a NASTRAN finite element analysis to simulate a prostate tumor in the pelvic cavity. The measurements show a wide separation between the elastic modulus of tumors and soft tissues such as muscle and prostate. NASTRAN.analyses show the ability to delineate regions of different elasticity based on the pattern of vibration amplitudes. The ability to change vibration frequency within the 100-300 Hz band seems particularly helpful in simulations and experiments which visualize small stiff inclusions in tissues. Preliminary results support the postulate that sonoelasticity imaging can provide useful information concerning tissue properties that are not otherwise obtainable. |
| Title |
Tissue typing using ultrasound RF time series: Experiments with animal tissue samples. |
| Author |
Moradi M, Abolmaesumi P, Mousavi P. |
| Journal |
Med Phys |
| Volume |
|
| Year |
2010 |
| Abstract |
PURPOSE: This article provides experimental evidence to show that the time series of radiofrequency (RF) ultrasound data can be used for tissue typing. It also explores the tissue typing information in RF time series. Clinical and high-frequency ultrasound are studied.
METHODS: Bovine liver, pig liver, bovine muscle, and chicken breast were used in the experiments as the animal tissue types. In the proposed approach, the authors record RF echo signals backscattered from tissue, while the imaging probe and the tissue are stationary. This sequence of recorded RF data generates a time series of RF echoes for each spatial sample of the RF signal. The authors use spectral and fractal features of ultrasound RF time series averaged over a region of interest, along with feedforward neural networks for tissue typing. The experiments are repeated at ultrasound frequency of 6.6 and also 55 MHz. The effects of increasing power and frame rate are studied.
RESULTS: The methodology yielded an average two-class classification accuracy of 95.1% when ultrasound data were acquired at 6.6 MHz and 98.1% when data were collected with a high-frequency probe operating at 55 MHz. In four-class classification experiments, the recorded accuracies were 78.6% and 86.5% for low and high-frequency ultrasound data, respectively. A set of 12 texture features extracted from the B-mode image equivalents of the RF data yields an accuracy of only 77.5% in typing the analyzed tissues. An increase in acoustic power and the frame rate of ultrasound results in an improvement in classification results.
CONCLUSIONS: The results of this study demonstrate that RF time series can be used for ultrasound-based tissue typing. Further investigation of the underlying physical mechanisms is necessary.
|
| Title |
Tissue-damaging effects of ultrasound. |
| Author |
Wittenzellner R. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1976 |
| Abstract |
No abstract available |
| Title |
Tissue-induced ultrasonic wavefront distortion. |
| Author |
Lwin T, O'Brien WD Jr. |
| Journal |
Proc Ultrason Symp IEEE |
| Volume |
|
| Year |
1996 |
| Abstract |
A quantitative description of wavefront distortion due to tissue inhomogeneities is desirable in order to assist in the development of aberration correction procedures for medical ultrasound imaging. A through-transmission in vitro measurement procedure was used to estimate the ultrasonic wavefront distortions of five different tissue types: bovine liver, porcine liver, bovine skin and bovine muscle for two different orientations (sound direction parallel and perpendicular to fiber orientation). Water and Dow Corning 710 were used for distortionless references. Known thickness tissue samples were vacuum packed in a thin plastic bag at the time of acquisition and were measured in a 20°C degassed water tank. Each sample was positioned perpendicular to the beam axis, immediately adjacent to a PVDF membrane hydrophone which was positioned in the 3 MHz circular transducer's focal region to receive the ultrasonic signals that propagated through the tissue sample. For each tissue sample, a total of 625 individual waveforms (25×25 rectangular grid in 1 mm steps) were collected. Three classes of calculations were performed to evaluate tissue inhomogeneities: correlation coefficient between two waveforms, arrival time shift between two waveforms, and the insertion loss for each waveform relative to water. Each was evaluated as a function of two waveform spatial location configurations. One was typical of phased array imaging (linear distance along each data row) and the other was based in eight waveform separation distances through the sample (1 to 5.66 mm). Results show that waveform distortion increased as a function of spatial location separation for the tissue samples and was significantly greater for the tissue samples compared to the reference materials. |
| Title |
Tissue-mimicking oil-in-gelatin dispersions for use in heterogeneous elastography phantoms. |
| Author |
Madsen EL, Frank GR, Krouskop TA, Varghese T, Kallel F, Ophir J. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2003 |
| Abstract |
A ten-month study is presented of materials for use in heterogeneous elastography phantoms. The materials consist of gelatin with or without a suspension of microscopic safflower oil droplets. The highest volume percent of oil in the materials is 50%. Thimerosal acts as a preservative. The greater the safflower oil concentration, the lower the Young?s modulus. Elastographic data for heterogeneous phantoms, in which the only variable is safflower oil concentration, demonstrate stability of inclusion geometry and elastic strain contrast. Young?s modulus ratios (elastic contrasts) producible in a heterogeneous phantom are as high as 2.7. The phantoms are particularly useful for ultrasound elastography. They can also be employed in MR elastography, although the highest achievable ratio of longitudinal to transverse relaxation times is considerably less than is the case for soft tissues. |
| Title |
Tomographic imaging of attenuation with simulation correction for refraction. |
| Author |
Farrell EJ. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1981 |
| Abstract |
Beam refraction in soft tissue and phase cancellation at the receiver can cause large errors and prevent tomographic reconstruction of attenuation. The method developed in this study incorporates simulation of ultrasound propagation into tomographic imaging to correct these effects. The method is based on input scan data of time-of-flight and received signal amplitude. The speed of propagation is estimated from the time-of-flight scan data. Based on this estimate, the simulation generates scan data of signal amplitude. This scan data represents the loss from refraction and phase cancellation with zero attenuation, and is used to correct the input amplitude scans. We evaluate the accuracy of the method, and investigate the trade-off between various scanning and filtering parameters. The evaluation is based on scan data generated by a comprehensive simulation including refraction and phase cancellation, finite beam width, several target shapes and sizes with sound parameters consistent with biologic values, and discrete translational and rotational transducer positions. In several cases with large refraction distortions, attenuation images are accurately reconstructed which are not feasible using standard tomographic methods. |
| Title |
Toxic effects of ultrasound in mice: damage to central and autonomic nervous systems. |
| Author |
Stolzenberg SJ, Edmonds PD, Torbit CA, Sasmore DP. |
| Journal |
Toxicol Appl Pharmacol |
| Volume |
|
| Year |
1980 |
| Abstract |
Whole-body exposure of pregnant Swiss-Webster mice to ultrasound at 37 C, 2 MHz, 1 W/cm2, continuous wave, for periods ranging from 80 to 200 sec resulted in hindleg dysfunction and a distended bladder syndrome; the latter was often associated with flaccid large intestine and compacted fecal material. Dose-response curves indicated damage thresholds at approximately 140 and 120 sec, respectively. Pathological examination confirmed the presence of damage to spinal cord and spinal ganglia as well as to adjacent bone, bone marrow, and dorsal skeletal muscle. The distribution of damage was consistent with a postulated thermal mechanism of preferential absorption and heating of bone, mediating subsequent damage to adjacent tissues. It is suggested that the distended bladder syndrome results from damage to autonomic nervous system, particularly to the pelvic nerve at the point of its emergence from the sacral region of the spinal column. The hindleg dysfunction presumably follows from the lesions in the spinal cord, due to extensive neural necrosis in the thoracosacral region. |
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