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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 326 out of 330
| Title |
Use of therapeutic ultrasound to restore failed trabeculectomies. |
| Author |
Yablonski M, Masonson HN, El-Sayyad F, Dennis PH, Hargrave S, Coleman DJ. |
| Journal |
Am J Ophthalmol |
| Volume |
|
| Year |
1987 |
| Abstract |
We treated 20 recently postoperative eyes with nonfunctioning trabeculectomies at the site of the failed bleb with two to four ultrasound applications, each of five seconds duration, at an intensity level of 10 kW/cm2. Fifteen of the eyes demonstrated a long-term decrease in intraocular pressure to 21 mm Hg or below. The mean intraocular pressure of all patients fell from a preultrasound mean (+/- S.D.) of 32 +/- 8 mm Hg to 20 +/- 10 mm Hg at a mean time of 236 +/- 204 days postultrasound. Complications included an immediate postultrasound rise in pressure over 10 mm Hg in 13 eyes, and the immediate development of a cataract in one patient. |
| Title |
Uses and abuses of ultrasound in diagnostic medicine. |
| Author |
Ziskin. |
| Journal |
Rep U S Dept HEW |
| Volume |
|
| Year |
1972 |
| Abstract |
No abstract available. |
| Title |
Uses and abuses of ultrasound in diagnostic medicine. |
| Author |
Ziskin M. |
| Journal |
Rep U S Dept HEW |
| Volume |
|
| Year |
1973 |
| Abstract |
No abstract available. |
| Title |
Using phase information in ultrasound RF-signals for tissue characterization. |
| Author |
Despotovi I,Goossens B,Vansteenkiste E,Pizurica A,Philips W. |
| Journal |
Proc 17th Annu Circuits Syst Signal |
| Volume |
|
| Year |
2008 |
| Abstract |
Due to many processing steps, the B-mode ultrasound images commonly used for medical diagnosis, contain less information than the original Radio-Frequency (RF) signals received by the ultrasound probe. Moreover, the raw RF-signals contain potentially more information on the investigated tissue.In this work we explore whether phase information of the ultrasound RF-signals can contribute to a better characterization of insonified preterm brain tissue. We use time series of raw RF-signals obtained with a linear probe. Amplitude and phase information are extracted from complex valued demodulated RF signals and subsequently an envelope image is reconstructed.Then, we analyze the distribution of the phase differences both within the signal and between neighboring signal scan lines and compute the entropy of those phase differences in local neighborhoods.Our initial qualitative results indicate that statistical properties of the phase differences, such as the proposed entropy,bring useful information about the insonified tissue. |
| Title |
Using resolution enhancement compression to reduce variance of scatterer size estimates from ultrasonic backscattered signals. |
| Author |
Sanchez JR, Pocci D, Oelze ML. |
| Journal |
IEEE Int Ultrasonics Symp Proc |
| Volume |
|
| Year |
2008 |
| Abstract |
Quantitative ultrasound (QUS) imaging techniques based on ultrasonic backscatter have been used successfully to diagnose and monitor disease. A method for improving the contrast and axial resolution of QUS parametric images by using the resolution enhancement compression (REC) technique is proposed. REC is a coded excitation and pulse compression technique that improves the axial resolution and enhances the -6-dB bandwidth of an ultrasonic imaging system. In this study, the improvements in variance of average scatterer diameter (ASD) estimates by using REC-QUS were quantified. Furthermore, RECQUS was used to extend the tradeoff between estimate variance and the spatial resolution of QUS parametric imaging using ASD estimates. Simulations and experimental measurements were conducted with a single-element transducer (f/4) having a center frequency of 10 MHz and a -6-dB bandwidth of 80%. Using REC, the -6-dB bandwidth was enhanced to 155%. In simulations, to monitor the improvements in contrast a software phantom with a cylindrical lesion was evaluated. In experimental measurements, a tissue mimicking phantom that contained glass spheres with different scatterer diameters was evaluated. Estimates of ASD in the simulations and experiments were obtained by comparing the normalized backscattered power spectra to theory. Improvements in REC-QUS over conventional QUS were quantified through estimate bias and variance, contrast-to-noise ratio and histogram analysis of QUS parametric images. Overall, a 51% increase in contrast and an 80% decrease in the variance of ASD estimates were obtained during simulations, while a reduction 93% was obtained in the variance of ASD for the experimental results. |
| Title |
Validation of transrectal ultrasonographic volumetry for orthotopic prostate tumours in mice. |
| Author |
Kraaij R, van Weerden WM, de Ridder CM, Gussenhoven EJ, Honkoop J, Nasu Y, Bangma CH. |
| Journal |
Lab Anim |
| Volume |
|
| Year |
2001 |
| Abstract |
Orthotopic human prostate tumour models in athymic nude mice are regarded as being most suitable for fundamental and pre-clinical research on prostate cancer. The anatomic localization of the tumour in the pelvis, however, provides little possibility for monitoring tumour growth or regression. To assess time-related changes in orthotopic tumour volume, we applied transrectal ultrasonography (TRUS) to the murine prostate. This technique has the advantages of allowing accurate monitoring of tumours during therapeutic manipulations and a reduction of animal use due to a reduction of sacrificing endpoints. To validate the TRUS method, the mouse prostate reconstitution model, RM-9, and the prostate-specific antigen (PSA) producing human prostate cancer xenograft PC-346 were used. Volumetric calliper measurements were performed with a 30 MHz ultrasound probe designed for intra-arterial use in humans. Tumour weight, determined at various time-points, was found to be closely related to actual tumour weight (R = 0.99) and, in the PC-346 model, to the level of PSA in the plasma. Furthermore, the interobserver variation for TRUS was low for tumours above 50 mg. Thus, TRUS for murine prostate tumours proves to be an accurate, reproducible and sensitive method. |
| Title |
Value of the spectral broadening index in continuous wave Doppler measurements. |
| Author |
Wijn PFF, van der Sar P, Gootzen THJM, Tilmans MHJ, Skotnicki SH. |
| Journal |
Med Biol Eng Comput |
| Volume |
|
| Year |
1987 |
| Abstract |
In an experimental study the value of the spectral broadening index (SBI) in continuous-wave (CW) Doppler measurements has been evaluated. The minimum SBI-value per heart beat (i.e. during systole) was calculated from intraoperatively obtained near-field and far-field Doppler spectra of the infrarenal aorta of 10 dogs. Near-field Doppler spectra show the same shape as far-field Doppler spectra but have a significantly different SBI. The minimum SBI of CW Doppler only contains useful information if the Doppler measurements are performed in the far field using a wide ultrasound beam (low emitting frequency). In that case the velocity profile in the blood vessel can be deduced from the SBI. The SBI depends strongly on the distance between the main axis of the ultrasound beam and the centre of the insonated blood vessel. A proper centring of the ultrasound beam corresponds with SBI-curves during the heart cycle which show minimal spectral broadening. A real-time display of the SBI-curve on the spectrum analyser provides the means of securing optimal CW Doppler spectra by minimising the SBI-curve during acquisition. |
| Title |
Variable resonant frequency crystal systems. |
| Author |
Fry WJ, Fry RB, Hall W. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
1951 |
| Abstract |
A general analysis of variable resonant frequency crystal systems which utilize liquid media as backing is presented. Formulas are obtained for evaluating the effect of different geometries of backing on the resonant frequencies of the system. The various loss factors associated with such a system are related to the measurable quantity, the quality factor. The observed operating characteristics of a variable resonant system which covers a two-to-one frequency band (40 kc to 80 kc) are presented. The results of an experimental comparison of such a system with fixed resonant frequency systems for generation of ultrasound in liquid media are given. The theory is used to correlate the experimental observations. |
| Title |
Variation of acoustic attenuation coefficient slope estimates.for in vivo liver. |
| Author |
Kuc R, Taylor KJ. |
| Journal |
Ultrasound Med Biol |
| Volume |
|
| Year |
1982 |
| Abstract |
Characterization of diffuse alcoholic disease is being attempted by estimating the slope of the acoustic attenuation coefficient with frequency, a parameter denoted by beta, from reflected ultrasound signals. The ultrasound signals reflected from within the body are distorted by the non-ideal properties of tissues. Two distorting mechanisms are considered: the propagation through nonhomogeneous media and the reflection from irregularly shaped interfaces. The mechanisms are modeled as random filters and their effect on estimating the value of beta are considered. The variances of three beta estimators are derived from the model. Clinical results on normals and patients with alcoholic liver disease are presented to verify the model. |
| Title |
Variation of acoustic speed with temperature in various excised human tissues studied by ultrasound computerized tomography. |
| Author |
Rajagopalan B, Greenleaf JF, Thomas PJ, Johnson SA, Bahn RC. |
| Journal |
Proc Second Int Symp Ultrason tissue Character |
| Volume |
|
| Year |
1977 |
| Abstract |
Variation of acoustic speed as a function of temperature was measured in fresh excised human liver, psoas muscle, spleen, spinal cord, kidney and fat, parenchyma and muscles associated with female breasts. Tissues were encased in rubber finger cots and suspended in a temperature controlled water bath. A prototype clinical ultrasound breast scanner was used to obtain data required to reconstruct distributions of acoustic speed within two-dimensional planes through the tissue specimens over a temperature range of 20 to 40 ? C. Quantitative images (printer listings of acoustic speed) of 64 x 64 pixels were used to obtain averages of up to 16 speed measurements within the image of each tissue. The acoustic speed in most tissues increased monotonically with temperature following the behavior of water. Acoustic speed of fat showed an anomalous decrease in acoustic speed around 34 ? C suggesting possible phase transition. |
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