Improved parameter estimates based on the homodyned K distribution

David, Hruška,; Oelze, Michael L.

doi:10.1109/tuffc.2009.1334

Cited by 82 publications

(89 citation statements)

References 31 publications

(45 reference statements)

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“…Additionally, I = E[A 2 ] is the mean intensity of backscattered echo. We used the level set algorithm to estimate u and k parameters from envelope samples [23].…”

Section: Backscattered Echo Assessmentmentioning

confidence: 99%

Temperature Monitoring during Focused Ultrasound Treatment by Means of the Homodyned K Distribution

et al. 2017

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Temperature monitoring is essential for various medical treatments. In this work, we investigate the impact of temperature on backscattered ultrasound echo statistics during a high intensity focused ultrasound treatment. A tissue mimicking phantom was heated with a spherical ultrasonic transducer up to 56 • C in order to imitate tissue necrosis. During the heating, an imaging scanner was used to acquire backscattered echoes from the heated region. These data was then modeled with the homodyned K distribution. We found that the best temperature indicator can be obtained by combining two parameters of the model, namely the backscattered echo mean intensity and the effective number of scatterers per resolution cell. Next, ultrasonic thermometer was designed and used to create a map of the temperature induced within the tissue phantom during the treatment.

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“…Additionally, I = E[A 2 ] is the mean intensity of backscattered echo. We used the level set algorithm to estimate u and k parameters from envelope samples [23].…”

Section: Backscattered Echo Assessmentmentioning

confidence: 99%

Temperature Monitoring during Focused Ultrasound Treatment by Means of the Homodyned K Distribution

et al. 2017

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“…Specifically, the homodyned k-distribution was used to model the signal amplitude of the envelope at tissue depths between 200 and 600 μm. A previously published algorithm was used to provide parameters from the backscattered envelope data [7]. The estimation routine provided k and μ parameters from each data sample.…”

Section: ) Texture Parametersmentioning

confidence: 99%

High-frequency backscatter analysis of human articular cartilage

Männicke

Schöne

Gottwald

et al. 2013

2013 IEEE International Ultrasonics Symposium (IUS)

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Abstract-46 punch biopsies of human cartilage were collected and scanned in time-resolved C-scan mode using a scanning acoustic microscope with a single-element 40-MHz transducer. From these data, spectra were estimated from short time gates at regions with low inclination and averaged with respect to their time delay to the tissue surface to account for the curved shape of articular cartilage. The depth-dependent spectral slope and amplitude profiles were used to estimate the maximum values and the depth-dependent slope. The surface reflection was excluded from analysis. In addition, the homodyned k distribution was used to model the signal amplitude of the envelope at tissue depths between 200 and 600 µm. The k and μ parameters were estimated from the envelope data. KruskalWallis analyses of variance were carried out for the acoustic parameters with respect to subscores of the Mankin grading system that are related to cellular and structural abnormalities of the cartilage matrix. The grading was performed on 2D histological cross sections. Additionally the cell number density was assessed.Moderate positive correlations between cell number and backscatter amplitude (R 2 =0.43) were observed. The backscatter amplitude parameters as well as k were not statistically significantly different with respect to degenerative changes, whereas µ was significantly lower for advanced stages of degeneration. The spectral slope and the extrapolation to the surface of the spectral slope were significantly higher for samples without signs of degeneration. The highest significance levels and chi² values were obtained for the maximum spectral slope value within the superficial zone of cartilage.The results suggest that amplitude based parameters alone are insufficient to discriminate different stages of spontaneous degeneration and that in contrast, spectral slope as well as envelope statistics are sensitive to osteoarthritic changes. Due to the correlation of backscatter amplitude and cell number, differences of the spectral slopes are likely due to cellular degenerations.

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“…The k parameter is computed as k = s/ . An efficient method for computing the best-fit parameters for a measured signal envelope was used [31].…”

Section: 3c Envelope Statisticsmentioning

confidence: 99%

Quantitative ultrasound assessment of thermal therapy in liver.

Kemmerer¹

2011

The Journal of the Acoustical Society of America

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Quantitative ultrasound (QUS) is a promising technique for non-invasive tissue characterization.In this work, the potential of QUS to assess thermal therapy in liver tissue was examined. Specifically, the QUS parameters of attenuation slope, effective scatterer size (ESD), effective acoustic concentration (EAC), and envelope statistics parameters µ and k were evaluated with respect to their ability to discriminate between heated and unheated liver tissue. Two sets of experiments were conducted for this purpose. In the first, a series of freshly excised and bisected rat livers was exposed by placing half of a lobe in a saline bath at 60 °C for 10 minutes and the other half in 37 °C saline. Each sample was then scanned using single-element ultrasonic transducers with a nominal center frequency of 20 MHz. In the second experiment, a series of fresh rat livers was exposed to high-intensity focused ultrasound (HIFU) to produce a discolored region of permanent damage. These samples were scanned in the area of damage before and after HIFU exposure with a 20 MHz single element transducer. Samples in both experiments were preserved, and histology slides were generated.In the saline bath experiments, statistically significant differences in attenuation slope, ESD, and EAC were observed between heated and unheated samples, while the changes in k and µ were not statistically significant. Attenuation slope increased on average from 0.65 dB/cm/MHz in untreated liver to 1.1 dB/cm/MHz in treated liver. Statistically significant differences (p<0.05) in ESD and EAC were observed using spherical Gaussian and fluid-filled sphere models between unheated and heated sides of every sample examined, with ESD decreasing by 34% and EAC increasing by 18 dB with thermal insult.A linear model was also considered, and statistically significant increases in slope were observed for all samples, as well as statistically significant decreases in intercept for 5 of 7 samples. The mean k parameter was found to decrease for 5 of 6 samples, although these changes were not statistically significant. Histology slides revealed a decrease of approximately 2.5% in cell diameter with heating.The HIFU experiments resulted in an increase in ESD and decrease in EAC in the region of the lesion as determined by visual inspection of the sample. The increases in ESD were significant in 3 of 5 samples for both spherical Gaussian and fluid-filled sphere form-factor models, while the decreases in EAC were statistically significant for 4 of 5 samples for these same models. Statistically significant differences were observed in spectral slope in 3 of 5 samples and in spectral intercept in 2 of 5 samples.Envelope statistics parameters were found to be insensitive to changes with HIFU exposure. Histology slides revealed no appreciable change in cell size.iii The results of this work suggest that QUS is capable of assessing HIFU and thermal therapy. ESD and attenuation slope were found to have the most potential to discriminate between unheated and heated liver s...

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Improved parameter estimates based on the homodyned K distribution

Cited by 82 publications

References 31 publications

Temperature Monitoring during Focused Ultrasound Treatment by Means of the Homodyned K Distribution

Temperature Monitoring during Focused Ultrasound Treatment by Means of the Homodyned K Distribution

High-frequency backscatter analysis of human articular cartilage

Quantitative ultrasound assessment of thermal therapy in liver.

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