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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 47 out of 330
| Title |
Attenuation of ultrasound in skeletal muscle. |
| Author |
Nassiri DK, Nicholas D, Hill CR. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1979 |
| Abstract |
Ultrasonic attenuation in fresh and 5% formalin fixed beef skeletal muscle has been measured, as a continuous function of frequency, in the range 1-8 MHz, for muscle fibre orientations both parallel and normal to the direction of propagation. Good agreement was found in all cases between two independent sets of measurements employing transmission and reflection techniques respectively. The data are.consistent with a power law dependence of attenuation coefficient on frequency, with an exponent that is not significantly different from unity. For propagation normal to the fibres attenuation values are found as 1.1 +/- 0.15 and 1.6 +/- 0.15 dB cm-1 MHz-1 for fresh and fixed tissue respectively, the corresponding values for parallel propagation being 2.9 +/- 0.23 and 4.1 +/- 0.25 dB cm-1 MHz-1. |
| Title |
Attenuation of ultrasound in solutions of serum albumin and its hydrolyzates. |
| Author |
Zorina OM, Fursov KP, El'piner IE. |
| Journal |
Sov Phys Acoust |
| Volume |
|
| Year |
1971 |
| Abstract |
No abstract available. |
| Title |
Attenuation of ultrasound in suspensions of bovine muscle myofibrils and myosin. |
| Author |
Shore D, Miles CA. |
| Journal |
Ultrasonics |
| Volume |
|
| Year |
1988 |
| Abstract |
The attenuation of 1.5-7 MHz ultrasound was measured over the pH range 3-7 in 100 mM KCl suspensions of bovine M. semitendinosus myofibrils, precipitated myosin and the residue of myofibrils after partial extraction of myosin. In all fractions attenuation showed a similar dependence on pH over the range 3-7, with a broad, substantial maximum in the region of pH 4.5-pH 5.5 and similar mass attenuation coefficients (per g protein). At pH 7 and 7 MHz these were 3.49 +/- 0.20 cm2 g-1 in the myofibrils, 3.26 +/- 0.31 cm2 g-1 in the myofibrilar residue and 2.83 +/- 0.68 cm2 g-1 in the precipitated myosin. Measurements at 5.3 MHz of precipitated myosin over a wider pH range revealed an attenuation titration curve similar to that previously observed in homogenates of muscle and muscle myofibrils, with substantial peaks at about pH 5 and 11.5, and a shoulder perhaps indicating a small underlying peak at about pH 8-9. Myosin dissolved in 800 mM KCl gave attenuation levels that were typically 50% lower than precipitated myosin e.g. at pH 7 and 7 MHz: 2.83 +/- 0.68 cm2 g-1 in the precipitated form, 1.29 +/- 0.10 cm2 g-1 in solution. These results indicated that: (a) attenuation by myosin filaments contributed substantially to the total attenuation in suspensions of myofibrils and (b) the peak in the myofibrilar attenuation is caused, or substantially contributed to, by a process taking place in the myosin component. |
| Title |
Attenuation of ultrasound: magnitude and frequency dependence for.tissue characterization. |
| Author |
Parker KJ, Lerner RM, Waag RC. |
| Journal |
Radiology |
| Volume |
|
| Year |
1984 |
| Abstract |
Backscattered ultrasonic waveforms from selected regions of the liver were collected from B-scans of 11 male patients ranging from 13 to 41 years of age and analyzed to determine local values of both the magnitude and frequency dependence of attenuation. Processing was based on frequency domain analysis and also incorporated precise corrections for time-varying gain, nonlinear amplifier compression, and beam diffraction, which would otherwise degrade accuracy. The.results demonstrate that (a) consistent and reproducible measurements of attenuation from one scan to the next are possible within a given patient, and (b) frequency dependence can deviate significantly from the linear relationship between frequency and attenuation commonly assumed for soft tissue. Based on the accuracy of the overall analysis and the reproducibility of the results, the authors suggest that a multivariate approach to clinical tissue characterization using both the magnitude and frequency dependence of ultrasonic attenuation may be possible. |
| Title |
Audible in-utero sound from ultrasound scanner. |
| Author |
Arulkumaran S, Talbert DG, Nyman M, Westgren M, Hsu TS, Ratnam SS. |
| Journal |
Lancet |
| Volume |
|
| Year |
1991 |
| Abstract |
No abstract available. |
| Title |
Author-subject index. |
| Author |
Halliwell M. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
| Title |
Automated breast sonography using a 7.5-MHz PVDF transducer: Preliminary clinical evaluation. Work in progress. |
| Author |
Jackson VP, Kelly-Fry E, Rothschild PA, Holden RW, Clark SA. |
| Journal |
Radiology |
| Volume |
|
| Year |
1986 |
| Abstract |
Breast ultrasound imaging performed with an automated machine was carried out in 89 patients, and images obtained with a conventional ceramic single-focus 4-MHz transducer and a 7.5-MHz polyvinylidene fluoride (PVDF) transducer were compared. The 7.5-MHz PVDF transducer improved overall image quality in 77% of patients and had equal penetration in 83%. It yielded greatly increased diagnostic information in 43% of 81 masses and improved visualization of calcification in 57% of 14 lesions in which calcium was visible on mammograms.
|
| Title |
Automated breast sonography using a 7.5-MHz PVDF transducer: preliminary clinical evalutation. |
| Author |
Jackson VP, Kelly-Fry E, Rothschild PA, Holden RW, Clark SA. |
| Journal |
Radiology |
| Volume |
|
| Year |
1986 |
| Abstract |
Breast ultrasound imaging performed with an automated machine was carried out in 89 patients, and images obtained with a conventional ceramic single-focus 4-MHz transducer and a 7.5-MHz polyvinylidene fluoride (PVDF) transducer were compared. The 7.5-MHz PVDF transducer improved overall image quality in 77% of patients and had equal penetration in 83%. It yielded greatly increased diagnostic information in 43% of 81 masses and improved visualization of calcification in 57% of 14 lesions in which calcium was visible on mammograms. |
| Title |
Automated method for characterization of diastolic transmitral Doppler velocity contours: Early rapid filling. |
| Author |
Hall AF, Kovacs SJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
Doppler echocardiographic studies of transmitral flow have become a routine clinical tool for the assessment and characterization of ventricular diastolic (filling) function. We have previously.derived a parametrized diastolic filling (PDF) formalism for the purpose of diastolic function.assessment using Doppler echocardiography. The model accommodates the mechanical "suction" feature of early diastolic filling of the heart by using a simple harmonic oscillator (SHO) as a paradigm for the kinematics of filling. PDF model predictions of transmitral flow velocity have shown excellent agreement with human echocardiographic Doppler contours (temporal profiles) when a visual, transparency overlay method of model fit to clinical Doppler contour comparison was used. The determination of PDF model parameters from the clinical Doppler contour is equivalent to the solution of the "inverse problem" of diastole. Previously, this determination consisted of a manual, iterative method of graphical overlay, in which model predicted contours were visually compared with the echocardiography machine generated Doppler contour using transparencies. To automate the process of model parameter estimation (i.e., solution of the "inverse problem") for the early or "rapid filling" phase of diastole (known in cardiology as the E-wave of the clinical Doppler velocity profile [DVP]) we recorded the acoustic pulsed Doppler signal using the forward channel of a commercial echocardiography machine. The Doppler spectrogram for a particular E-wave was recreated using short-time Fourier transform processing. The maximum velocity envelope (MVE) was extracted from the spectrogram. The PDF model was fit to the E-wave MVE using a Levenberg-Marquardt (iterative) algorithm by the requirement that the mean-square error between the clinical data (MVE) and the model be minimized. Because the model is linear, all of the PDF parameters for the Doppler E-wave can be uniquely determined. We show that: (1) solution of the "inverse problem of diastole" is possible; (2) clinical Doppler E-wave contours can be accurately reproduced and quantified using the PDF formalism and its parameters; and (3) our proposed, automated method of PDF parameter determination for the E-wave is robust. |
| Title |
Automated method for characterization of diastolic transmitral Doppler velocity contours: Late atrial filling. |
| Author |
Hall AF, Aronovitz JA, Nudelman SP, Kovacs SJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1994 |
| Abstract |
We develop an automated method of characterizing the late atrial filling phase of diastole by fitting a kinematic model for diastolic filling to the clinical Doppler A-wave contour. The result is a set of model parameters which completely characterizes the contour. We have previously derived a parameterized diastolic filling (PDF) model, which predicts the time-dependent transmitral blood flow velocity obtained by Doppler echocardiography. An automated method to determine the PDF model parameters for early rapid filling from the clinical Doppler E-wave has also been developed and validated. The method consists of digitizing the acoustic Doppler waveform, recreating the Doppler velocity profile, extracting the maximum velocity envelope, and fitting the PDF model for early filling to the envelope. In the current work, we apply the same general approach for PDF parameter determination for the late atrial filling phase of diastole. To assess the presence and significance of near-degeneracies in the model parameter set, numerical experiments (consisting of fitting the model to a model-generated contour to which Gaussian noise was added) were performed. These revealed a two-dimensional degeneracy in four-dimensional parameter space which could be removed by using two kinematic simplifications: critical damping and resonant forcing. We show that these degeneracy-eliminating approximations do not limit the ability of the model to predict clinical A-wave contours. |
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