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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 145 out of 330
| Title |
Improved diagnostics through quantitative ultrasound imaging. |
| Author |
Hruska DP,Sanchez J,Oelze ML. |
| Journal |
Proc IEEE Annu Conf of EMBS |
| Volume |
|
| Year |
2009 |
| Abstract |
Conventional B-mode imaging in ultrasound consists of displaying the log-compressed envelope of the backscattered signal. While clinical ultrasonic B-mode images have good spatial resolution, i.e., better than a millimeter, the contrast resolution of ultrasonic B-mode images is typically low. However, additional information is contained in the ultrasonic backscattered signal, which can be used to create images related to tissue microstructure. Because diagnosis of disease is typically based on histological examination of tissue microstructure, the ability to quantify and describe tissue microstructure through ultrasound may result in improved diagnostic capabilities of ultrasound. Tissue-mimicking phantoms and animal models of breast cancer were used to assess the ability of novel ultrasonic imaging techniques to quantify microstructure. Four parameters were extracted from the ultrasonic backscattered signal and related to the microstructure. The effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) parameters were based on modeling the frequency dependence of the backscatter. The k parameter (which quantifies the periodicity of scatterer locations) and the μ parameter (which estimates the number of scatterers per resolution cell) were based on modeling the statistics of the backscattered envelope. Images constructed with these parameters resulted in an increase in contrast between diseased tissue and normal tissues but at the expense of spatial resolution. Specifically, in simulation, quantitative ultrasound (QUS) increased the contrast-to-noise ratio (CNR) between targets and background by more than 10 times in some cases. Statistically significant differences were observed between three kinds of tumors using the ESD, EAC, and k parameters. QUS imaging was also improved with the addition of coded excitation. A novel coded excitation technique was used that improved the variance of estimates over conventional pulsing methods, e.g, the variance of ESD estimates were reduced by a factor of up to 10. |
| Title |
Improved parameter estimates based on the homodyned K distribution. |
| Author |
Hruska DP, Oelze ML. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2009 |
| Abstract |
Abstract—Quantitative techniques based on ultrasound backscatter are promising tools for ultrasonic tissue characterization. There is a need for fast and accurate processing strategies to obtain consistent estimates. An improved parameter estimation algorithm for the homodyned K distribution was developed based on SNR, skewness, and kurtosis of fractional- order moments. From the homodyned K distribution, estimates of the number of scatterers per resolution cell (μ parameter) and estimates of the ratio of coherent to incoherent
backscatter signal energy (k parameter) were obtained. Furthermore, angular compounding was used to reduce estimate variance while maintaining spatial resolution of subsequent parameter images. Estimate bias and variance from Monte Carlo simulations were used to quantify the improvement using the new estimation algorithm compared with existing techniques. Improvements due to angular compounding were quantified by the decrease in estimate variance in both simulations and measurements from tissue-mimicking phantoms and by the
increase in target contrast. Finally, the new algorithm was used to derive estimates from 2 kinds of mouse mammary tumors for tissue characterization. The new estimation algorithm yielded estimates with lower bias and variance than existing techniques. For a typical pair of parameters (μ = 5 and k = 1), the bias and variance were reduced 67% and 16%, respectively, for the μ parameter estimates and 79% and 37%, respectively, for the k parameter estimates. The use of angular compounding further reduced the estimate variance, e.g., the variance of estimates for the μ parameter from measurements was reduced by a factor of approximately 90 when using 120 angles of view. Finally, statistically significant differences were observed in parameter estimates from 2 kinds of mouse mammary tumors using the new algorithm. These improvements suggest estimating parameters from the backscattered envelope can enhance the diagnostic capabilities of ultrasonic imaging. |
| Title |
Improved parametric imaging of scatterer size estimates using angular compounding. |
| Author |
Gerig AL,Varghese T,Zagzebski JA. |
| Journal |
IEEE Trans UFFC |
| Volume |
|
| Year |
2004 |
| Abstract |
The feasibility of estimating and imaging scatterer size using backscattered ultrasound signals and spectral analysis techniques was demonstrated previously. In many cases, size estimation, although computationally intensive, has proven to be useful for monitoring, diagnosing, and studying disease. However, a difficulty that is encountered in imaging scatterer size is the large estimator variance
caused by statistical fluctuations in echo signals from random media. This paper presents an approach for reducing these statistical uncertainties. Multiple scatterer size estimates are generated for each image pixel using data acquired
from several different directions. These estimates are subsequently compounded to yield a single estimate that has a reduced variance. In this feasibility study, compounding was achieved by translating a sectored-array transducer in a direction parallel to the acquired image plane. Angular compounding improved the signal-to-noise ratio (SNR) in scatterer size images. The improvement is proportional to the square root of the effective number of statistically
independent views available for each image pixel. |
| Title |
Improved phased array controller for ultrasound hyperthermia applicators. |
| Author |
Field AS. |
| Journal |
Thesis(MS): Univ of Illinois |
| Volume |
|
| Year |
1985 |
| Abstract |
No abstract available. |
| Title |
Improved scatterer property estimates from ultrasound backscatter for small gate lengths using a gate-edge correction factor. |
| Author |
Oelze ML, O'Brien WD Jr. |
| Journal |
J Acoust Soc Am |
| Volume |
|
| Year |
2004 |
| Abstract |
Backscattered rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. The backscattered power spectrum is found by taking the magnitude squared of the Fourier transform of a gated time segment corresponding to a region in the scattering volume. When a time segment is gated, the edges of the gated regions change the frequency content of the backscattered power spectrum due to truncating of the waveform. Tapered windows, like the Hanning window, and longer gate lengths reduce the relative contribution of the gate-edge effects. A new gate-edge correction factor was developed that partially accounted for the edge effects. The gate-edge correction factor gave more accurate estimates of scatterer properties at small gate lengths compared to conventional windowing functions. The gate-edge correction factor gave estimates of scatterer properties within 5% of actual values at very small gate lengths (less than 5 spatial pulse lengths) in both simulations and from measurements on glass-bead phantoms. While the gate-edge correction factor gave higher accuracy of estimates at smaller gate lengths, the precision of estimates was not improved at small gate lengths over conventional windowing functions. |
| Title |
Improved scatterer property estimates from ultrasound backscatter using gate-edge correction and a pseudo-Welch technique. |
| Author |
Ghoshal G, Oelze ML. |
| Journal |
IEEE Trans Ultrason Ferroelectr Freq Control |
| Volume |
|
| Year |
2010 |
| Abstract |
Quantitative ultrasound (QUS) techniques have been widely used to estimate the size, shape and mechanical properties of tissue microstructure for specified regions of interest (ROIs). For conventional methods, an ROI size of 4 to 5 beamwidths laterally and 15 to 20 spatial pulse lengths axially has been suggested to estimate accuracy and precision better than 10% and 5%, respectively. A new method is developed to decrease the standard deviation of the quantitative ultrasound parameter estimate in terms of effective scatterer diameter (ESD) for small ROIs. The new method yielded estimates of the ESD within 10% of actual values at an ROI size of five spatial pulse lengths axially by two beamwidths laterally, and the estimates from all the ROIs had a standard deviation of 15% of the mean value. Such accuracy and precision cannot be achieved using conventional techniques with similar ROI sizes. |
| Title |
Improved ultrasound image characterization of fibroadenomas by use of a tunable receiver in combination with high frequency scanning. |
| Author |
Kelly-Fry E, Jackson VP, Holden RW. |
| Journal |
Proc Fifth Meet World Fed Ultrasound Med Biol |
| Volume |
|
| Year |
1988 |
| Abstract |
The objective of these investigations is to make use of the varying ultrasound frequency dependence of scattering for different types of soft tissue as a means to improve contrast resolution and image characterizations of the internal structure of solid breast masses. In this presentation, the effectiveness of this approach, primarily in respect to image characterization of fibroadenomas, is discussed. In ongoing clinical research studies with an automated breast scanner, it was found that most fibroadenomas are essentially non-attenuating for examination frequencies as high as 11MHz. Also, use of these frequencies in conjunction with a sharply focused transducer provides improved visualization of both the wall structure and fine tissue componenets within fibroadenomas. As a further extension of these investigations, a tunable receiver which allows precise control of bandwidth was incorporated into the automated breast scanner. When this receiver was used as a narrow band filter, the system yielded images with excellent spatial and contrast resolution. More important, when compared to standard images obtained with wide bandwidth receiver systems, these fibroadenomas images are significantly improved in terms of image characterization of internal structure components. These high frequency, tunable receiver images of fibroadenomas are distinctly different from those of malignant masses obtained under the same circumstances. |
| Title |
Improvement of in vitro thrombolysis employing magnetically-guided microspheres. |
| Author |
Torno MD, Kaminski MD, Xie Y, Meyers RE, Mertz CJ, Liu X, O'Brien WD Jr, Rosengart AJ. |
| Journal |
Throm Res |
| Volume |
|
| Year |
2007 |
| Abstract |
Significant shortcomings in clinical thrombolysis efficiencies and arterial recanalization rates still exist to date necessitating the development of additional thrombolysis-enhancing technologies. For example, to improve tPA-induced systemic clot lysis several supplementary treatment methods have been proposed, among them ultrasound-enhanced tissue plasminogen activator (tPA) thrombolysis which has already found some clinical applicability. The rationale of this study was to investigate whether biodegradable, magnetic spheres can be a useful adjuvant to currently existing tPA-induced thrombolysis and further enhance clot lysis results. Based on an envisioned, novel thrombolysis technology – magnetically-guided, tPA-loaded nanocarriers with triggered release of the shielded drug at an intravascular target site – we evaluated the lysis efficiencies of magnetically-guided, non-medicated magnetic spheres in various combinations with tPA and ultrasound. When tPA was used in conjunction with magnetic spheres and a magnetic field, the lysis efficiency under static, no-flow conditions improved by 1.7 and 2.7 fold for red and white clots, respectively. In dynamic lysis studies, the addition of ultrasound and magnetically-guided spheres to lytic tPA dosages resulted in both maximum clot lysis efficiency and shortest reperfusion time corresponding to a 2-fold increase in lysis and 7-fold reduction in recanalization time, respectively. Serial microscopic evaluations on histochemical sections reconfirmed that tPA penetration into and fragmentation of the clot increased with escalating exposure time to tPA and magnetic spheres/field. These results delineate the effectiveness of magnetic spheres as an adjuvant to tPA therapy accelerating in vitro lysis efficiencies beyond values found for tPA with and without ultrasound. We demonstrated that the supplementary use of magnetically-guided, non-medicated magnetic spheres significantly enhances in vitro static and dynamic lysis of red and white blood clots. |
| Title |
Improvement of in vitro thrombolysis employing magnetically-guided microspheres. |
| Author |
Torno MD, Kaminski MD, Xie Y, Meyers RE, Mertz CJ, Liu X, O'Brien WD Jr, Rosengart AJ. |
| Journal |
Throm Res |
| Volume |
|
| Year |
2007 |
| Abstract |
Significant shortcomings in clinical thrombolysis efficiencies and arterial recanalization rates still exist to date necessitating the development of additional thrombolysis-enhancing technologies. For example, to improve tPA-induced systemic clot lysis several supplementary treatment methods have been proposed, among them ultrasound-enhanced tissue plasminogen activator (tPA) thrombolysis which has already found some clinical applicability. The rationale of this study was to investigate whether biodegradable, magnetic spheres can be a useful adjuvant to currently existing tPA-induced thrombolysis and further enhance clot lysis results. Based on an envisioned, novel thrombolysis technology--magnetically-guided, tPA-loaded nanocarriers with triggered release of the shielded drug at an intravascular target site--we evaluated the lysis efficiencies of magnetically-guided, non-medicated magnetic spheres in various combinations with tPA and ultrasound. When tPA was used in conjunction with magnetic spheres and a magnetic field, the lysis efficiency under static, no-flow conditions improved by 1.7 and 2.7 fold for red and white clots, respectively. In dynamic lysis studies, the addition of ultrasound and magnetically-guided spheres to lytic tPA dosages resulted in both maximum clot lysis efficiency and shortest reperfusion time corresponding to a 2-fold increase in lysis and 7-fold reduction in recanalization time, respectively. Serial microscopic evaluations on histochemical sections reconfirmed that tPA penetration into and fragmentation of the clot increased with escalating exposure time to tPA and magnetic spheres/field. These results delineate the effectiveness of magnetic spheres as an adjuvant to tPA therapy accelerating in vitro lysis efficiencies beyond values found for tPA with and without ultrasound. We demonstrated that the supplementary use of magnetically-guided, non-medicated magnetic spheres significantly enhances in vitro static and dynamic lysis of red and white blood clots. |
| Title |
Improvement of in vitro thrombolysis employing magnetically-guided microspheres. |
| Author |
Torno MD, Kaminski MD, Xie Y, Meyers RE, Mertz CJ, Liu X, O'Brien WD Jr, Rosengart AJ. |
| Journal |
Throm Res |
| Volume |
|
| Year |
2008 |
| Abstract |
Significant shortcomings in clinical thrombolysis efficiencies and arterial recanalization rates still exist to date necessitating the development of additional thrombolysis-enhancing technologies. For example, to improve tPA-induced systemic clot lysis several supplementary treatment methods have been proposed, among them ultrasound-enhanced tissue plasminogen activator (tPA) thrombolysis which has already found some clinical applicability. The rationale of this study was to investigate whether biodegradable, magnetic spheres can be a useful adjuvant to currently existing tPA-induced thrombolysis and further enhance clot lysis results. Based on an envisioned, novel thrombolysis technology--magnetically-guided, tPA-loaded nanocarriers with triggered release of the shielded drug at an intravascular target site--we evaluated the lysis efficiencies of magnetically-guided, non-medicated magnetic spheres in various combinations with tPA and ultrasound. When tPA was used in conjunction with magnetic spheres and a magnetic field, the lysis efficiency under static, no-flow conditions improved by 1.7 and 2.7 fold for red and white clots, respectively. In dynamic lysis studies, the addition of ultrasound and magnetically-guided spheres to lytic tPA dosages resulted in both maximum clot lysis efficiency and shortest reperfusion time corresponding to a 2-fold increase in lysis and 7-fold reduction in recanalization time, respectively. Serial microscopic evaluations on histochemical sections reconfirmed that tPA penetration into and fragmentation of the clot increased with escalating exposure time to tPA and magnetic spheres/field. These results delineate the effectiveness of magnetic spheres as an adjuvant to tPA therapy accelerating in vitro lysis efficiencies beyond values found for tPA with and without ultrasound. We demonstrated that the supplementary use of magnetically-guided, non-medicated magnetic spheres significantly enhances in vitro static and dynamic lysis of red and white blood clots. |
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