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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 17 out of 330
| Title |
A simple device to couple linear array transducers to neonate heads for ultrasonic scanning of the brain. |
| Author |
Smith WL, Franklin TD, Katakura K, Fry FJ, Eggleton RC. |
| Journal |
Radiology |
| Volume |
|
| Year |
1980 |
| Abstract |
A plastisol coupler has been designed that improves acoustical coupling for linear array ultrasound transducers. This device improves both ease in scanning and image quality in real-time scanning of the infant brain. |
| Title |
A simple method for production of trackless focal lesions with focused ultrasound: statistical evaluation of the effects of irradiation on the central nervous system of the cat. |
| Author |
Basauri L, Lele PP. |
| Journal |
J Physiol (Lond) |
| Volume |
|
| Year |
1962 |
| Abstract |
In a previous paper (Lele, 1962b) it has been shown that by irradiation with a single beam of focused ultrasound it is possible to produce trackless focal alterations of predetermined size at any desired location within a relatively homogeneous and stable medium. This paper will present the results obtained by application of ultrasound, under comparable experimental conditions, to the brain of the cat in a statistical manner and will discuss its potentialities and limitations as an experimental tool. More specifically, it will deal with (1) the relation between ultrasonic dosage and lesion size in different target areas and under controlled experimental conditions, with special reference to the range of deviation that was encountered; and (2) the statistical probability of accurately hitting a pre-determined discrete target in a blind experiment by the stereotaxic method. The neurophysiological effects of ultrasonic irradiation with subthreshold dosages in reference to its potential use for locating targets without inflicting any damage will be dealt with in a subsequent paper. |
| Title |
A simple method for production of trackless focal lesions with focused ultrasound: physical factors. |
| Author |
Lele PP. |
| Journal |
J Physiol (Lond) |
| Volume |
|
| Year |
1962 |
| Abstract |
No abstract available. |
| Title |
A simple optical method for observing medical ultrasound pulse characteristics in vitro. |
| Author |
Riley WA, Barnes RW, McKinney WM. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1979 |
| Abstract |
An optical method is described for studying the spatial and temporal characteristics of broad-band ultrasonic pulses propagating in transparent media. The simplicity of the approach suggests its consideration as a method for calibration and comparison of the transmitted pulse characteristics of medical ultrasound systems. |
| Title |
A simplified approach for real-time detection of arterial wallvelocity and distension. |
| Author |
Tortoli P, Bettarini R, Guidi F, Andreuccetti F, Righi D. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2001 |
| Abstract |
Arterial stiffness is known to increase with age and with many vascular diseases, but its noninvasive assessment in patients still represents a difficult task. The measurement of diameter change during the cardiac cycle (distension) has been proposed as a means to estimate arterial compliance and stiffness. Therefore, we have developed a simple PC-based device and algorithm for noninvasive quantification of vessel wall motion and diameter change in humans. This goal is achieved in real-time by processing the base-band signals from a commercial ultrasound Doppler system. Real-time operation is of crucial importance, because it allows a rapid achievement of optimal measurement conditions. The system was evaluated in a laboratory using a string phantom and was tested on the carotid arteries of 10 volunteers. Wall velocities from 0.05 to 600 mm/s and displacements lower than 2 μm were detected with phantoms. The measured carotid diameter change in the volunteers ranged from 7.5 to 11.8% (mean=9.8%) and agrees closely with values reported in the literature. The difference between values taken one hour apart ranged from 0.2 to 0.5%. We conclude that the new system provides rapid, accurate, and repeatable measurements of vessel distension in humans |
| Title |
A simulation algorithm for ultrasound liver backscattered signals. |
| Author |
Zatari D, Botros N, Dunn F. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1995 |
| Abstract |
In this study, we present a simulation algorithm for the backscattered ultrasound signal from liver tissue. The algorithm simulates backscattered signals from normal liver and three different liver abnormalities. The performance of the algorithm has been tested by statistically comparing the simulated signals with corresponding signals obtained from a previous in vivo study. To verify that the simulated signals can be classified correctly we have applied a classification technique based on an artificial neural network. The acoustic features extracted from the spectrum over a 2.5 MHz bandwidth are the attenuation coefficient and the change of speed of sound with frequency (dispersion). Our results show that the algorithm performs satisfactorily. Further testing of the algorithm is conducted by the use of a data acquisition and analysis system designed by the authors, where several simulated signals are stored in memory chips and classified according to their abnormalities. |
| Title |
A simulation model for ultrasonic temperature imaging using change in backscattered energy. |
| Author |
Trobaugh JW, Arthur RM, Straube WL, Moros EG. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2008 |
| Abstract |
Ultrasound backscattered from tissue has previously been shown theoretically and experimentally to change predictably with temperature in the hyperthermia range, i.e., 37°C to 45°C, motivating use of the change in backscattered ultrasonic energy (CBE) for ultrasonic thermometry. Our earlier theoretical model predicts that CBE from an individual scatterer will be monotonic with temperature, with, e.g., positive change for lipid-based scatterers and negative for aqueous-based scatterers. Experimental results have previously confirmed the presence of these positive and negative changes in one-dimensional ultrasonic signals and in two-dimensional images acquired from in vitro bovine, porcine and turkey tissues. In order to investigate CBE for populations of scatterers, we have developed an ultrasonic image simulation model, including temperature dependence for individual scatterers based on predictions from our theoretical model. CBE computed from images simulated for populations of randomly distributed scatterers behaves similarly to experimental results, with monotonic variation for individual pixel measurements and for image regions. Effects on CBE of scatterer type and distribution, size of the image region and signal-to-noise ratio have been examined. This model also provides the basis for future work regarding significant issues relevant to temperature imaging based on ultrasonic CBE such as effects of motion on CBE, limitations of motion-compensation techniques and accuracy of temperature estimation, including tradeoffs between temperature accuracy and available spatial resolution. |
| Title |
A single-pole model for the propagation of ultrasound in soft tissue. |
| Author |
Arthur RM, Gurumurthy KV. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1985 |
| Abstract |
A minimum-phase function, which characterizes the velocity dispersion in tissue was calculated from measured attenuation. This function was incorporated into a causal tissue model. Predictions of attenuation using the minimum-phase function with just a single pole matched measured attenuation in the 1- to 10-MHz range within a few percent. Dispersion of phase velocity predicted by the single-pole model was comparable to measured dispersion. The frequency associated with the single pole, which is a relaxation frequency, decreased with hemoglobin concentration and collagen content but increased with temperature. The electrical equivalent circuit for this model is a delay coupled with a low-pass filter which can be configured as a resistance in series with a parallel combination of resistance and capacitance. |
| Title |
A speckle target adaptive imaging technique in the presence of distributed aberrations. |
| Author |
Ng GC, Freiburger PD, Walker WF, Trahey GE. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
1997 |
| Abstract |
Acoustic velocity inhomogeneities in tissue result in aberration of ultrasound images. These aberrations can be modeled as a near field thin phase screen or as a distributed aberrator. The effect of a near field thin phase screen is to time shift the received echo at each element, while distributed aberrators result in both pulse distortions and time shifts from element to element. Most current techniques for the correction of distributed aberrators are limited to application on point targets. A new technique is proposed which uses multiple transmits from spatially shifted transmit apertures ( the translating transmit aperture algorithm), in conjunction with phase conjugate filters, to correct for distributed aberrations in the presence of speckle targets. The performance of the translating transmit aperture algorithm in improving the correlation between signals received by elements of different spatial separations is measured, and factors affecting the performance of this technique are investigated in simulation and experiment. |
| Title |
A spectral approach to ultrasonic scattering from human tissue: methods, objectives and backscattering measurements. |
| Author |
Chivers RC, Hill CR. |
| Journal |
Phys Med Biol |
| Volume |
|
| Year |
1975 |
| Abstract |
The dearth of information on the physical processes involved in the propagation of ultrasound in tissue and the growing need for such information are discussed. The physical nature of the ultrasonic diagnostic process in considered in terms of a wave phenomenon and the limitations and advantages of frequency spectral analysis as a means of obtaining information are briefly analysed. A description is given of an experimental measuring system using a time-gate to select echoes scattered from a particular volume at a depth in soft tissues. The influence of attenuation by overlying tissue and the choice of the duration of the acceptance gate on the frequency spectra obtained are considered. The paper reports some backscattering measurements on formalin-fixed samples of human fat, liver and spleen in the frequency range 0-5-5-0 MHz. The results suggest that the approach may have diagnostic value in a clinical situation, in the characterization of.structure in specific volumes of soft human tissue. |
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