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BRL Abstracts Database |
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Your search for ultrasound produced 3296 results. Page 212 out of 330
| Title |
Quantitative ultrasound estimates from populations of scatterers with continuous size distributions. |
| Author |
Lavarello R, Oelze M. |
| Journal |
IEEE Trans Ultrason Ferroelectr Freq Control |
| Volume |
|
| Year |
2011 |
| Abstract |
Although quantitative ultrasound imaging based on backscattering coefficients has proven potential for tissue characterization, the scattering models used in most studies assume distributions of identical scatterers. However, actual tissues may exhibit multiple levels of spatial scales. Therefore, the objective of the present study is to analyze the effects of scatterer size distributions when using a fluid-sphere model for estimating values of effective scatterer diameter (ESD) through both simulations and experiments. For simulations, ESD estimates were obtained at several analysis frequencies between 1 and 40 MHz from populations of scatterers with diameters ranging between 25 and 100 μm, 25 and 50 μm, 50 and 100 μm, and 50 and 75 μm. For sufficiently high analysis frequencies, the ESD estimates obtained through simulations were approximately inversely proportional to frequency and mostly independent of the underlying scatterer size distribution. Asymptotic expressions for the expected ESD estimates at low- and high-frequency limits were derived. Experiments were conducted using two gelatin phantoms with contrast agent spheres ranging in diameter from 30 to 140 μm and 70 to 140 μm, and 5-, 7.5-, 10-, and 13-MHz focused transducers. Not only was the asymptotic behavior of ESD versus frequency estimates observed experimentally, but also the experimental ESD estimates using the 10- and 13-MHz transducers were lower than the smallest scatterers present in the second phantom. These results may have a direct impact on how scatterer size estimates corresponding to specimens with different subresolution spatial scales should be interpreted. |
| Title |
Quantitative ultrasound estimates from populations of scatterers with continuous size distributions: Effects of the size estimator algorithm. |
| Author |
Lavarello R, Oelze M. |
| Journal |
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control |
| Volume |
|
| Year |
2012 |
| Abstract |
Quantitative ultrasonic techniques using backscatter coefficients (BSCs) may fail to produce physically meaningful estimates of effective scatterer diameter (ESD) when the analysis media contains scatterers of different sizes. In this work, three different estimator algorithms were used to produce estimates of ESD. The performance of the three estimators was compared over different frequency bands using simulations and experiments with physical phantoms. All estimators produced ESD estimates by comparing the estimated BSCs with a scattering model based on the backscattering cross section of a single spherical fluid scatterer. The first estimator consisted of minimizing the average square deviation of the logarithmically compressed ratio between the estimated BSCs and the scattering model. The second and third estimators consisted of minimizing the mean square error between the estimated BSCs and a linear transformation of the scattering model with and without considering an intercept, respectively. Simulations were conducted over several analysis bandwidths between 1 and 40 MHz from populations of scatterers with either a uniform size distribution or a distribution based on the inverse cubic of the size. Diameters of the distributions ranged between [25, 100], [25, 50], [50, 100], and [50, 75] μm. Experimental results were obtained from two gelatin phantoms containing cross-linked dextran gel spheres ranging in diameter from 28 to 130 μm and 70 to 130 μm, respectively, and 5-, 7.5-, 10-, and 13-MHz focused transducers. Significant differences in the performances of the ESD estimator algorithms as a function of the analysis frequency were observed. Specifically, the third estimator exhibited potential to produce physically meaningful ESD estimates even for large ka values when using a single-size scattering model if sufficient analysis bandwidth was available. |
| Title |
Quantitative ultrasound for monitoring high-intensity focused ultrasound treatment in vivo |
| Author |
Ghoshal G, Kemmerer JP, Karunakaran C, Miller RJ, Oelze ML. |
| Journal |
IEEE TUFFC |
| Volume |
|
| Year |
2016 |
| Abstract |
The success of any minimally invasive treatment procedure can be enhanced significantly if combined with a robust noninvasive imaging modality that can monitor therapy in real time. Quantitative ultrasound (QUS) imaging has been widely investigated for monitoring various treatment responses such as
chemotherapy, radiation, and thermal therapy. Previously, we demonstrated the feasibility of using spectral-based QUS parameters to monitor high-intensity focused ultrasound (HIFU) treatment of in situ tumors in euthanized rats [Ultrasonic Imaging 36(4), 239–255, 2014]. In the present study, we examined the use of spectral-based QUS parameters to monitor HIFU treatment of in vivo rat mammary adenocarcinoma tumors (MAT) where significant tissue motion was present. HIFU was applied to tumors in rats using a single-element transducer. During the off part of the HIFU duty cycle, ultrasound backscatter was recorded from the tumors using a linear array co-aligned with the HIFU focus. A total of 10 rats were treated with HIFU in this study with an additional sham-treated rat. Spectral parameters from the backscatter coefficient, i.e., effective scatterer diameter (ESD) and effective acoustic concentration (EAC), were estimated. The
changes of each parameter during treatment were compared with a temperature profile recorded by a fine-needle thermocouple inserted into the tumor a few millimeters behind the focus of the HIFU transducer. The mean ESD changed from 121 ± 6 to 81 ± 8 μm(p-value = 0.0002), and the EAC changed from 33 ± 2 to 46 ± 3 dB/cm3 (p-value = 0.0002) during HIFU exposure as the temperature increased on average from 38.7 ± 1.0 ◦ C to 64.2 ± 2.7 ◦ C. The changes in ESD and EAC were linearly correlated with the changes in tissue temperature during the treatment.
When HIFU was turned off, the ESD increased from 81 ± 8 to 121 ± 7 μm and the EAC dropped from 46 ± 3to 36 ± 2 dB/cm3 as the temperature decreased from 64.2 ± 2.7 ◦
C to 45 ± 2.7 ◦ C. QUS was demonstrated in vivo to track temperature elevations caused by HIFU exposure. |
| Title |
Quantitative ultrasound from single cells to biophantoms to tumors |
| Author |
O'Brien WD Jr, Han A, Auger T |
| Journal |
34th Annual International Conference of the IEEE EMBS |
| Volume |
|
| Year |
2012 |
| Abstract |
There is no underestimating the importance of
modern imaging to the improved detection and
management of diseases such as cancer. Ultrasound
offers a cost-effective and safe modern imaging modality.
A quantitative approach, termed quantitative ultrasound
(QUS), offers the capability to examine the anatomic
microstructure of tissue, hence opening up opportunities
to quantify/diagnose such microstructure. One approach
to improve specificity with QUS techniques, a modelbased
approach, is to develop ultrasonic scattering
models that match the anatomic geometry of the tissue
type under investigation. To do so, an approach from
simple (individual cells) to moderate complexity
(groupings of cells imbedded in a supportive structure)
to significant complexity (actual tissue/tumors) has merit,
especially if the degrees of complexity are with the same
cell type. Therefore, an approach for improved imaging
capabilities with quantitative ultrasound is that from
single cells to biophantoms to tumors, and is discussed
herein. |
| Title |
Quantitative ultrasound imaging for monitoring in situ high-intensity focused ultrasound exposure |
| Author |
Ghoshal G, Kemmerer JP, Karunakaran C, Abuhabsah R, Miller RJ, Sarwate S, Oelze ML |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2014 |
| Abstract |
Quantitative ultrasound (QUS) imaging is hypothesized to map temperature elevations induced in tissue with high spatial and temporal resolution. To test this hypothesis, QUS techniques were examined to monitor high-intensity focused ultrasound (HIFU) exposure of tissue. In situ experiments were conducted on mammary adenocarcinoma tumors grown in rats and lesions were formed using a HIFU system. A thermocouple was inserted into the tumor to provide estimates of temperature at one location. Backscattered time-domain waveforms from the tissue during exposure were recorded using a clinical ultrasonic imaging system.
Backscatter coefficients were estimated using a reference phantom technique. Two parameters were estimated from the backscatter coefficient (effective scatterer diameter (ESD) and effective acoustic concentration (EAC). The changes in the average parameters in the regions corresponding to the HIFU focus over time were correlated to the temperature readings from the thermocouple. The changes in the EAC parameter were consistently correlated to temperature during both heating and cooling of the tumors. The changes in the ESD did not have a consistent trend with temperature. The mean ESD and EAC before exposure were 120 ± 16 mm and 32 ± 3 db/cm3, respectively, and changed to 144 ± 9 mm and 51 ± 7 db/cm3, respectively, just before the last HIFU pulse was delivered to the tissue. After the tissue cooled down to 37°C, the mean ESD and EAC were 126 ± 8 mm and 35 ± 4 db/cm3, respectively. Peak temperature in the range of 50-60°C was recorded by a thermocouple placed just behind the tumor. These results suggest that QUS techniques have the potential to be used for noninvasive monitoring of HIFU exposure. |
| Title |
Quantitative ultrasound imaging for monitoring in situ high-intensity focused ultrasound exposure |
| Author |
Ghoshal G, Kemmerer JP, Karunakaran C, Abuhabsah R, Miller RJ, Sarwate S, Oelze ML |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
2014 |
| Abstract |
Quantitative ultrasound (QUS) imaging is hypothesized to map temperature elevations induced in tissue with high spatial and temporal resolution. To test this hypothesis, QUS techniques were examined to monitor high-intensity focused ultrasound (HIFU) exposure of tissue. In situ experiments were conducted on mammary adenocarcinoma tumors grown in rats and lesions were formed using a HIFU system. A thermocouple was inserted into the tumor to provide estimates of temperature at one location. Backscattered time-domain waveforms from the tissue during exposure were recorded using a clinical ultrasonic imaging system.
Backscatter coefficients were estimated using a reference phantom technique. Two parameters were estimated from the backscatter coefficient (effective scatterer diameter (ESD) and effective acoustic concentration (EAC). The changes in the average parameters in the regions corresponding to the HIFU focus over time were correlated to the temperature readings from the thermocouple. The changes in the EAC parameter were consistently correlated to
temperature during both heating and cooling of the tumors. The changes in the ESD did not have a consistent trend with temperature. The mean ESD and EAC before exposure were 120 ± 16 mm and 32 ± 3 db/cm3, respectively, and changed to 144 ± 9 mm and 51 ± 7 db/cm3, respectively, just before the last HIFU pulse was delivered to the tissue. After the tissue cooled down to 37°C, the mean ESD and EAC were 126 ± 8 mm and 35 ± 4 db/cm3, respectively. Peak temperature in the range of 50-60°C was recorded by a thermocouple placed just behind the tumor. These results suggest that QUS techniques have the potential to be used for noninvasive
monitoring of HIFU exposure.
Keywords
quantitative ultrasound imaging, HIFU, effective scatterer diameter, effective scatterer concentration, parametric imaging |
| Title |
Quantitative ultrasound imaging using acoustic backscatter coefficients. |
| Author |
Boote EJ. |
| Journal |
Thesis(PhD): Univ of Wisconsin-Madison |
| Volume |
|
| Year |
1988 |
| Abstract |
Current clinical ultrasound scanners render images which have brightness levels related to the degree of backscattered energy from the tissue being imaged. These images offer the interpreter a qualitative impression of the scattering characteristics of the tissue being examined, but due to the complex factors which affect the amplitude and character of the echoed acoustic energy, it is difficult to make quantitative assessments of scattering nature of the tissue, and thus, difficult to make precise diagnosis when subtle disease effects are present.
In this dissertation, a method of data reduction for determining acoustic backscatter coefficients is adapted for use in forming quantitative ultrasound images of this parameter. In these images, the brightness level of an individual pixel corresponds to the backscatter coefficient determined for the spatial position represented by that pixel. The data reduction method utilized rigorously accounts for extraneous factors which affect the scattered echo waveform and has been demonstrated to accurately determine backscatter coefficients under a wide range of conditions.
The algorithms and procedures used to form backscatter coefficient images are described. These were tested using tissue-mimicking phantoms which have regions of varying scattering levels. Another phantom has a fat-mimicking layer for testing these techniques under more clinically relevant conditions. Backscatter coefficient images were also formed of in vitro human liver tissue.
A clinical ultrasound scanner has been adapted for use as a backscatter coefficient imaging platform. The digital interface between the scanner and the computer used for data reduction are described. Initial tests, using phantoms are presented. A study of backscatter coefficient imaging of in vivo liver was performed using several normal, healthy human subjects.
|
| Title |
Quantitative ultrasound imaging: In vivo results in normal liver. |
| Author |
Zagzebski JA, Lu ZF, Yao LX. |
| Journal |
Ultrason Imaging |
| Volume |
|
| Year |
1993 |
| Abstract |
A method for quantitative imaging of ultrasonic backscatter levels has been implemented on a clinical imager. The method is based on comparing echo signal data from a sample or patient to echo data processed in the same way but acquired. from a reference phantom. The attenuation coefficient and the backscatter coefficient of the reference phantom are known, permitting these quantities to be estimated for the sample. In the present paper, the spatial location of echo data. acquisition is retained in the backscatter data analysis; quantitative "backscatter estimator" images are constructed, from which the backscatter coefficient over a region of interest may be obtained. When applied to human liver images, backscatter coefficients determined in 10 normal subjects were in approximate agreement with in vitro liver backscatter coefficients reported by previous workers. |
| Title |
Quantitative ultrasound scatter imaging. |
| Author |
Jones JP, Leeman S, Blackledge J. |
| Journal |
Proc First IEEE Comput Soc Int Symp Med Imaging Image Interpr |
| Volume |
|
| Year |
1982 |
| Abstract |
Ultrasound/tissue interactions provide a fertile base for imaging techniques, and a number of novel and apparently diverse methods for human imaging are currently being developed. An original, unified theory of these quantitative scatter-imaging techniques is developed. It is demonstrated that the success of the methods is inextricably bound together with the development of physical models for the ultrasound/tissue interaction. The concept of image "fuzziness" is introduced and contrasted against attained image resolution. |
| Title |
Quantitative ultrasound techniques and improvements to diagnostic ultrasonic imaging. |
| Author |
Oelze ML |
| Journal |
IEEE Int Ultrason Symp Proc |
| Volume |
|
| Year |
2012 |
| Abstract |
Conventional ultrasound B-mode imaging is mainly qualitative in nature. While conventional imaging techniques, including ultrasound, may be sensitive to the detection of anomalous tissue features, the ability to classify these tissues often lacks specificity. As a result, a large number of biopsies of tissues
with suspicious image findings are performed each year with a vast majority of these biopsies resulting in a negative finding. Quantitative ultrasound (QUS) imaging techniques can provide specific numbers related to tissue features that can increase the specificity of image findings leading to improvements in
diagnostic ultrasound. QUS imaging techniques can encompass a wide variety of techniques including spectral-based parameterization, elastography, flow estimation and envelope statistics. Furthermore, a goal of QUS imaging techniques is to provide system- and operator-independent parameters related to tissue properties. Different applications of QUS imaging techniques in diagnostic ultrasound will be discussed in this paper. Specifically, spectral-based techniques and envelope statistics at clinical frequencies and at high ultrasonic frequencies (> 15 MHz) will be examined for their abilities to improve diagnostic ultrasound. Spectral-based techniques include the estimation of the backscatter coefficient, estimation of attenuation, and estimation of scatterer properties such as the correlation length associated with an effective scatterer size and the concentration of scatterers. Envelope statistics include the estimation of the number density of scatterers and quantification of coherent to incoherent signals produced from the tissue. Challenges related to the implementation of QUS imaging techniques and recent successes of QUS implementation for medical diagnostics will be discussed. Challenges for clinical application include correctly accounting for attenuation effects and implementation of QUS on clinical devices. Successful applications demonstrating the ability of QUS to improve medical diagnostics will include cancer detection and classification of solid tumors and lymph nodes, detection and quantification of fatty liver disease, and monitoring and assessment of thermal therapy on solid tumors. |
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