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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 49 out of 330
| Title |
B-scan ultrasonography during orbital surgery. |
| Author |
Purnell EW, Cappaert WE, Sokollu A. |
| Journal |
J Clin Ultrasound |
| Volume |
|
| Year |
1973 |
| Abstract |
B-scan ultrasonography is being performed with a newly developed hand-held scanner during retrobulbar tumor surgery. We believe that it is a valuable aid in the localization and the removal of these tumors. The instrument may be directly inserted into the surgical wound, permitting otherwise unobtainable views of the lesion and of the adjacent structures. |
| Title |
Backscatter coefficient estimation using tapers with gaps |
| Author |
Luchies AC, Oelze ML |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2014 |
| Abstract |
When using the backscatter coefficient (BSC) to estimate quantitative ultrasound parameters such as the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC), it is necessary to assume that the interrogated medium contains diffuse scatterers. Structures that invalidate this assumption can affect the estimated BSC parameters in terms of increased bias and variance and decrease performance when classifying disease. In this work, a method was developed to mitigate the effects of echoes from structures that invalidate the assumption of diffuse scattering, while preserving as much signal as possible for obtaining diffuse scatterer property estimates. Backscattered signal sections that contained nondiffuse signals were identified and a windowing technique was used to provide BSC estimates for diffuse echoes only. Experiments from physical phantoms were used to evaluate the effectiveness of the proposed BSC estimation methods. Tradeoffs associated with effective mitigation of specular scatterers
and bias and variance introduced into the estimates were quantified. Analysis of the results suggested that discrete prolate spheroidal (PR) tapers with gaps provided the best performance for minimizing BSC error. Specifically, the mean square error for BSC between measured and theoretical had an average value of approximately 1.0 and 0.2 when using a Hanning taper and PR taper respectively, with six gaps. The BSC error due to amplitude bias was smallest for PR (Nω = 1) tapers. The BSC error due to shape bias was smallest for PR (Nω = 4) tapers. These
results suggest using different taper types for estimating ESD versus EAC. |
| Title |
Backscatter coefficient estimation using tapers with gaps |
| Author |
Luchies AC, Oelze ML |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2014 |
| Abstract |
When using the backscatter coefficient (BSC) to estimate quantitative ultrasound parameters such as the effective scatterer diameter (ESD) and the effective acoustic concentration (EAC), it is necessary to assume that the interrogated medium contains diffuse scatterers. Structures that invalidate this assumption can affect the estimated BSC parameters in terms of increased bias and variance and decrease performance when classifying disease. In this work, a method was developed to mitigate the effects of echoes from structures that invalidate the assumption of diffuse scattering, while preserving as much signal as possible for obtaining diffuse scatterer property estimates. Backscattered signal sections that contained nondiffuse signals were identified and a windowing technique was used to provide BSC estimates for diffuse echoes only. Experiments from physical phantoms were used to evaluate the effectiveness of the proposed BSC estimation methods. Tradeoffs associated with effective mitigation of specular scatterers
and bias and variance introduced into the estimates were quantified. Analysis of the results suggested that discrete prolate spheroidal (PR) tapers with gaps provided the best performance for minimizing BSC error. Specifically, the mean square error for BSC between measured and theoretical had an average value of approximately 1.0 and 0.2 when using a Hanning taper and PR taper respectively, with six gaps. The BSC error due to amplitude bias was smallest for PR (Nω = 1) tapers. The BSC error due to shape bias was smallest for PR (Nω = 4) tapers. These
results suggest using different taper types for estimating ESD versus EAC. |
| Title |
Bactericidal effects of ultrasound. |
| Author |
Russell LA, Buswell AM, Fry FJ, Whitney R McL. |
| Journal |
Ind Eng Chem |
| Volume |
|
| Year |
1954 |
| Abstract |
Qualitative studies of the effects of ultrasound on bacteria have been reported with the suggestion of its use for the sterilization of water supplies and dairy products. Quantitative ultrasonic data are necessary for the evaluation of this technique..Adequate control and measurement of the ultrasonic variables were obtained by employing a travelingwave field at known crystal voltages and frequencies, a probe for measurement of sound-pressure amplitude that is mounted on a coordinate system for reproducible location in the field, and a radiation chamber allowing close to 100% transmission of energy that is suitably mounted for reproducibility of position. The effect of various sizes, shapes, and mountings of quartz crystals on the degree of uniformity and the relative sound-pressure amplitude of the field is demonstrated by plots..This information makes possible the observation of ultrasonic effects in terms of the magnitude of the sound variables, not only on bacteria but on any system that can be placed in the chamber or uniform portion of the field. These observations are free of radio-frequency or thermal effects. |
| Title |
Bandwidth and resolution enhancement through pulse compression. |
| Author |
Oelze ML. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2007 |
| Abstract |
A novel pulse compression technique is developed that improves the axial resolution of an ultrasonic imaging system and provides a boost in the echo signal-to-noise ratio (eSNR). The new technique, called the resolution enhancement compression (REC) technique, was validated with simulations and experimental measurements. Image quality was examined in terms of three metrics: the eSNR, the bandwidth, and the axial resolution through the modulation transfer function (MTF). Simulations were conducted with a weakly-focused, single-element ultrasound source with a center frequency of 2.25 MHz. Experimental measurements were carried out with a single-element transducer (f/3) with a center frequency of 2.25 MHz from a planar reflector and wire targets. In simulations, axial resolution of the ultrasonic imaging system was almost doubled using the REC technique (0.29 mm) versus conventional pulsing techniques (0.60 mm). The -3 dB pulse/echo bandwidth was more than doubled from 48% to 97%, and maximum range sidelobes were -40 dB. Experimental measurements revealed an improvement in axial resolution using the REC technique (0.31 mm) versus conventional pulsing (0.44 mm). The -3 dB pulse/echo bandwidth was doubled from 56% to 113%, and maximum range sidelobes were observed at -45 dB. In addition, a significant gain in eSNR (9 to 16.2 dB) was achieved |
| Title |
Barker code in TCD ultrasound systems to improve the sensitivity of emboli detection. |
| Author |
Lei X, Heng Z, Shangkai G. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
2009 |
| Abstract |
In present research, Barker-coded excitation is applied to improve the sensitivity of emboli detection in transcranial Doppler (TCD) ultrasound systems. A 13-chip Barker code with a base pulse sequence that comprises two cycles at 2 MHz is used to compare with a 20-cycle pulse in both simulation studies and in vitro experiments. The results show that the system using coded excitation gains a 2.78-dB improvement in measured embolus-to-blood ratio (MEBR) while keeping a similar signal-to-noise ratio (SNR). The simulation results also indicate that the MEBR of the emboli are related to their velocities—a fast embolus has lower MEBR compared with a slow one with the same backscatter amplitudes, which makes fast emboli more difficult to detect. TCD system using coded excitation is more sensitive for faster and smaller emboli, which is significant for early diagnosis of stroke. |
| Title |
Basic acoustic properties of microbubbles. |
| Author |
Jong N, Bouakaz A, Frinking P. |
| Journal |
Echocardiography |
| Volume |
|
| Year |
2002 |
| Abstract |
Small (encapsulated) gas bubbles in a contrast medium react to an external oscillating pressure field with volume pulsations. Depending on the magnitude of the ultrasound wave, the vibrations will be related either linearly or nonlinearly to the applied acoustic pressure. For low acoustic pressures, the instantaneous radius oscillates linearly in relation to the amplitude of the applied external pressure field. The oscillation of the bubble is governed by parameters such as resonance frequency, damping coefficients, and shell properties. For higher amplitudes of the external field, the pulsation of the bubbles becomes nonlinear. The spectrum of the scattered ultrasound wave also contains higher harmonics of the emitted frequency in addition to the fundamental frequency. The emitted frequency, bubble size, and nonlinear propagation effects have significant influence on the harmonic generation. For encapsulated bubbles exposed to even higher acoustic amplitudes, their scattering effectiveness increases dramatically and becomes transient. The scattered frequency spectrum broadens, containing higher harmonics. This consequence is due to rupture, disappearance, change of gas content, etc. Using these specific characteristics of the contrast bubbles will open new perspectives in imaging and analysis for medical diagnosis. |
| Title |
Basic concept of ultrasonic interferometry in liquids. |
| Author |
Carome EF, Gutowski FA, Schuele DE. |
| Journal |
Am J Phys |
| Volume |
|
| Year |
1957 |
| Abstract |
The use of the acoustic interferometer to investigate the absorption of ultrasound in liquids is discussed. Following elementary treatments of the propagation of acoustic waves in liquids and the properties of the piezoelectric sound source, a simple method is developed for measuring the sound absorption coefficient. Emphasis throughout the paper is placed on the concepts of the acoustic impedance of the liquid and the effective electrical impedance of the sound source. |
| Title |
Basic physics of therapeutic ultrasound. |
| Author |
ter Haar G. |
| Journal |
Physiotherapy |
| Volume |
|
| Year |
1978 |
| Abstract |
No abstract available |
| Title |
Basic principles of ultrasound tissue characterization. |
| Author |
Shung KK. |
| Journal |
Nonivasive Tech in Bio Med |
| Volume |
|
| Year |
1990 |
| Abstract |
No abstract available. |
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