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Wyświetlanie 1-15 z 19
Tytuł:
Temperature Measurement by Statistical Parameters of Ultrasound Signal Backscattered from Tissue Samples
Autorzy:
Gambin, B.
Kruglenko, E.
Powiązania:
https://bibliotekanauki.pl/articles/1402186.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.50.wp
43.35.+d
87.57.-s
Opis:
A novel estimation of temperature changes inside soft tissues has been proposed in sub-ablation range, i.e. ≈ 20°C-48°C. This estimation has been obtained by studying statistical properties of backscattered ultrasonic signals. Two different procedures of heating/cooling have been performed in which the RF echoes have been registered from soft tissue phantom in the first procedure, and from soft tissue in vitro in the second one. Calculated envelopes of signals registered in time points during heating/cooling experiments have been treated as a statistical sample drawn from a random variable with three different distributions, namely the Rayleigh distribution, the Nakagami distribution, and the K-distribution. The histograms obtained in subsequent time moments have been fitted to the three distributions. Dependencies of their shape and scale parameters on temperature have been calculated. It is concluded that the shape parameter of the K-distribution can be chosen as the best marker of temperature changes in both experiments. The choice of the marker has been made by analysis of temperature dependencies of all calculated parameters and by comparing the quality of fitting all histograms to the considered distributions. Besides, the chosen marker as a function of temperature exhibits the closest shape to temperature/time function experimentally measured.
Źródło:
Acta Physica Polonica A; 2015, 128, 1A; A-72-A-78
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Some aspects of numerical modeling of temperature increase due to ultrasound beam irradiation of rat liver
Autorzy:
Kruglenko, E.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/331800.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Some aspects of FEM modeling of hyperthermia, the procedure of tissue temperature rise above 37 oC inside the living organism, as a treatment modality, are studied. Low intensity focused ultrasound (LIFU) beam has been used as a source of temperature rise in the liver tissue during performed experiments in vitro. The comparison of the FEM model of the corresponding heating process and the experimental results has been presented in [1]. In the paper, the FEM model of heating scheme of the rat liver tissue in vivo irradiated by the same ultrasound transducer is formulated. At first, the existence of blood perfusion is taken into account in the model equation. Secondly, the thermal and acoustical properties, which are the input parameters of the numerical model, are taken from the published data in literature. Here, the size and the intensity of heat sources are modeled in two ways on the basis of acoustic nonlinear equation solutions in 3 layers attenuating medium. We demonstrate how the results of FEM model in the case of in vitro and in vivo heating, depend on the assumed power density of heat sources, as well as on the size of the heated area. The results are compared and discussed. The influence of different models on temperature rise profiles are demonstrated.
Źródło:
Hydroacoustics; 2011, 14; 99-110
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature detection based on nonparametric statistics of ultrasound echoes
Autorzy:
Byra, M.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/332315.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
noninvasive temperature monitoring
nonparametric statistics
ultrasound backscattering
Opis:
Different ultrasound echoes properties have been used for the noninvasive temperature monitoring. Temperature variations that occur during heating/cooling process induce changes in a random process of ultrasound backscattering. It was already proved that the probability distribution of the backscattered RF (radio frequency) signals is sensitive to the temperature variations. Contrary to previously used methods which explored models of scattering and involved techniques of fitting histograms to a special probability distribution two more direct measures of changes in statistics are proposed in this paper as temperature markers. They measure the ''distance'' between the probability distributions. The markers are the Kolmogorov Smirnov distance and Kulback-Leiber divergence. The feasibility of using such nonparametric statistics for non- invasive ultrasound temperature estimation is demonstrated on the ultrasounds data collected during series of heating experiments in which the temperature was independently registered by the classical thermometer or thermocouples.
Źródło:
Hydroacoustics; 2015, 18; 17-23
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Incompressible limit for a magnetostrictive energy functional
Autorzy:
Gambin, B.
Bielski, W.
Powiązania:
https://bibliotekanauki.pl/articles/201841.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
gamma-convergence
incompressibility
magnetostrictive material
second gradient of deformation
existence of minimizers
Opis:
The modern materials undergoing large elastic deformations and exhibiting strong magnetostrictive effect are modelled here by free energy functionals for nonlinear and non-local magnetoelastic behaviour. The aim of this work is to prove a new theorem which claims that a sequence of free energy functionals of slightly compressible magnetostrictive materials with a non-local elastic behaviour, converges to an energy functional of a nearly incompressible magnetostrictive material. This convergence is referred to as a Γ -convergence. The non-locality is limited to non-local elastic behaviour which is modelled by a term containing the second gradient of deformation in the energy functional.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2013, 61, 4; 1025-1030
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasonic Synthetic Apertures: Review
Autorzy:
Nowicki, A.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/176456.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
synthetic aperture
effective aperture
ultrasonography
Opis:
In the paper the concept of synthetic aperture used for high resolution/high frame rate ultrasonic imaging is reviewed. The synthetic aperture technique allows building extended “virtual” apertures, synthesized from smaller real aperture resulting in improved lateral resolution along full penetration depth without sacrificing the frame rate. Especially, four methods, synthetic aperture focusing (SAF), multi-element synthetic aperture focusing (M-SAF), synthetic receive aperture (SRA) and synthetic transmit aperture (STA) are addressed. The effective aperture function, describing two-way, far field radiation is a useful tool in beam pattern analysis. Some basic notations, which are used to calculate the effective aperture are introduced in Appendix.
Źródło:
Archives of Acoustics; 2014, 39, 4; 427-438
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical properties of wavelet transform coefficients of backscattering signal from soft tissues and their phantoms
Autorzy:
Gambin, B.
Doubrovina, O.
Powiązania:
https://bibliotekanauki.pl/articles/331908.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The paper contains the wavelet approach to registered backscattered RF signals from two different cases. First, the wavelet analysis has been performed for RF signals registered from soft tissue phantoms. The second case is the wavelet analyses of RF scattered signals from regions of healthy and BCC changed human skin. The three phantoms made from tissuemimicking material with different structures have been measured. We claim that there are visible differences in the statistical parameters of wavelets coefficients of signals between healthy and BCC changed skin regions as well as between phantoms without scatterers and with different number of strong small scatterers.
Źródło:
Hydroacoustics; 2013, 16; 59-66
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
RF signal amplitude statistics during temperature changes in tissue phantoms
Autorzy:
Kruglenko, E.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/332743.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Two heating protocols for soft tissue phantoms have been performed. An Agar-Gel-Oil (AGO) mixture has been heated locally by applying ultrasonic beams and a Poly Vinyl Alcohol-cryogel (PVA-c) has been heated “globally” by a water bath with a controlled temperature rise. The RF signals were collected during heating by an ultrasound transducer to ensure no interference from waves from the heating transducer. Independently, the thermocouples' measurement has been used to obtain temperature as a function of time in the AGO case. At first, a compensation of attenuation was performed and normalized envelopes of signals were used as data for statistical analysis. It is shown that random the values of the backscattered amplitude are close to Rayleigh and K-distributed random variables for AGO and PVA-c, respectively. Temperature is linked to the scale parameter of Rayleigh distribution for the AGO, and the shape parameter of K-distribution for PVA-c were calculated and discussed in the context of their suitability for the acoustic measurement of temperature.
Źródło:
Hydroacoustics; 2014, 17; 115-122
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
BEM and Shear lag method for interface problem of bi-material structure under static loading
Metoda Elementów Brzegowych i metoda "shear lag" w zagadnieniu delaminacji dwuwarstwowej struktury pod wpływem statycznego obciążenia
Autorzy:
Valeva, V.
Ivanova, J.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/280619.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
BEM
Shear lag analysis
bi-material structure
debond length
Opis:
The behaviour of the interface of a pre-cracked bi-material ceramic-metal structure under static axial loading is an object of interest in the present paper. To solve the problem for interface delamination of the structure and to determine the debond length along the interface, a 2D BEM code was created and applied. The interface plate is assumed as a very thin plate comparing with the others two. The parametric (geometric and elastic) analysis of the debond length and interface shear stress is done. First, the obtained numerical results are compared with analytical ones from 1D. Shear lag analysis of the considered structure. The respective comparison is illustrated in figures and shows a good agreement. The comparison between the calculated using 2D BEM code elastic-brittle debond lengths with Song's experimental data for the bi-material structure Zinc/Steel as well as with respective results from FEM simulation shows good coincidence.
W pracy badano zachowanie się na granicy pomiędzy warstwami metalu i ceramiki pod wpływem statycznego obciążenia przyłożonego w kierunku równoległym do połączenia pasm, w przypadku istnienia początkowego nacięcia w jednej z warstw prostopadłego do powierzchni połączenia. W celu rozwiązania zagadnienia delaminacji wzdłuż powierzchni łączącej oba materiały i wyznaczenia długości odspojenia został stworzony i zastosowany kod Metody Elementów Brzegowych – zagadnienie 2-wymiarowe. Warstwa łącząca dwa materiały została potraktowana jako bardzo cienka płyta, w porównaniu do grubości obu warstw materiałowych. Przeprowadzono parametryczną (geometrycznaą i sprężystą) analizę długości odspojenia (delaminacji) i naprężenia stycznego. Otrzymane rezultaty numeryczne porównano z analitycznymi rozwiązaniami 1-wymiarowej analizy tzw. metodą "shear lag". Otrzymane wyniki, zilustrowane na rysunkach, wykazują wzajemną zgodność. Pokazano również, że wyniki uzyskane przy użyciu Metody Elementów Brzegowych są zgodne z wynikami eksperymentu Song'a przeprowadzonego dla dwuwarstwowego elementu kompozytowego pomiędzy warstwą cynku i stali, a także z wynikami uzyskanymi w Metodzie Elementów Skończonych.
Źródło:
Journal of Theoretical and Applied Mechanics; 2011, 49, 1; 17-29
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Differentiation of random structure properties using wavelet analysis of backscattered ultrasound
Autorzy:
Gambin, B.
Wojcik, J.
Doubrovina, O.
Powiązania:
https://bibliotekanauki.pl/articles/331612.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
spectrogram
scalogram
wavelets
random scattering structure
Opis:
The aim of this work was to find the differences between random media by analyzing the properties of the ultrasound signals backscattered from the inhomogeneities. A numerical model is used to generate two types of random media. The first has the randomness in scatterers’ positions and the second has the randomness in the size and acoustical properties of scatterers. The numerical model of wave scattering has been used to simulate the RF (radio frequency) signals caused by the incident pulse traveling as a plane wave. The markers of randomness type differences between the scattering media were obtained with the help of the spectral and wavelet analysis. The effect of differences in randomness type is more spectacular when the wavelet analysis is performed.
Źródło:
Hydroacoustics; 2016, 19; 121-128
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relationships between acoustical properties and stiffness of soft tissue phantoms
Autorzy:
Gambin, B.
Kruglenko, E.
Byra, M.
Powiązania:
https://bibliotekanauki.pl/articles/332049.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
soft tissue phantoms
elastography
ultrasound attenuation
speed of sound
Nakagami maps
stiffness
Opis:
Polyvinyl-alcohol cryogel is commonly used for soft tissue phantom manufacture. The gel formation from an aqueous solution of polyvinyl-alcohol takes place during the freezing and thawing cycle. The aim of this work was to assess the degree of gel solidification, hence the material stiffness, by means of quantitative ultrasound. We manufactured three phantoms which differed in the number of freezing/thawing cycles. First, tissue phantoms were examined with an elastography technique. Next, we measured the speed of sound and the attenuation coefficient. What is more, the inter structure variations in phantoms were assessed with the Nakagami imaging which quantifies the scattering properties of the backscattered ultrasound echo. Obtained results confirmed the connection between the number of freezing/thawing cycles and the solidification p rocess. We d efined th e bo undary layer as a region which has a different structure than the sample interior. Next, for each phantom this layer was extracted based on a Nakagami parameter map. We calculated that the thickness of the boundary layer was lower in samples which were subjected to a larger number of freezing/thawing cycles.
Źródło:
Hydroacoustics; 2016, 19; 111-120
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relationship between thermal and ultrasound fields in breast tissue in vivo
Autorzy:
Gambin, B.
Kruglenko, E.
Wójcik, J.
Powiązania:
https://bibliotekanauki.pl/articles/332806.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
backscattered ultrasonic signal
non-uniform temperature field
Opis:
The study shows the direct relationship between the temperature field and the parallel changes that are taking place in backscattered ultrasonic signals from the breast tissue in vivo when heated to the temperature of approximately 42 deg. C. The non-uniform temperature field inside the heating tissue was determined by the numerical model using FEM. It is shown that the spatial distribution of intensities of the backscattered signals coincides with the temperature distribution field predicted by the numerical model in some areas. The result indicates the possibility of the indirect measurement of the temperature rise in the breast tissue in vivo by measuring the intensity variations of the ultrasound echo.
Źródło:
Hydroacoustics; 2015, 18; 53-58
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature level and properties of wavelet approximations of backscattered ultrasound
Autorzy:
Doubrovina, O.
Gambin, B.
Kruglenko, E.
Powiązania:
https://bibliotekanauki.pl/articles/331549.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
The aim of the paper is to find links between the dynamics of changes of statistical parameters and changes in spectral properties of the signal envelope of backscattered RF signals during the thermal process. We have shown previously that by using wavelet approximations these tendencies are better recognized in the case of the heating of a phantom sample than in the parallel analysis performed for a full signal envelope. Here we are currently expanding this statement to the case of heating a soft tissue sample in vitro. The shape parameter of the K- distributed random variable is considered as a statistical marker of temperature level changes. Additionally, the spectral properties of different levels of wavelet approximations are calculated and their sensitivity to temperature increase and decrease is demonstrated. Both approaches registering changes in temperature, are used in the case of the pork loin tissue sample in vitro, heated by an ultrasound beam with a different power.
Źródło:
Hydroacoustics; 2014, 17; 37-46
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Soft tissue-mimicking materials with various number of scatterers and their acoustical characteristics
Autorzy:
Kruglenko, E.
Gambin, B.
Cieślik, L.
Powiązania:
https://bibliotekanauki.pl/articles/331726.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
For the study of the temperature increase in the soft tissues irradiated by a low-power ultrasound [1], soft tissue-mimicking materials can be used. The phantoms have been produced based on an aqueous solution of agar, oil, and glass beads microparticles. The RF signals collected in the experiments enabled evaluation of the acoustic properties of phantoms with different number of strong scatterers (concentration varied from 0 to 30 pcs/mm3). Speed of sound (SOS) determined for the phantoms was similar to the value typical of soft tissue (about 1540 m/s). To determine attenuation coefficient the semi-transmission method has been used. Attenuation coefficient value varied from 0.5 to 1.1 dB/(MHz cm), depending on the number of scatterers. It was shown that the phantoms stored for 6 months preserved their acoustical properties and were usable for further experiments. It was found that within the total attenuation, the part corresponding to scattering can be distinguished.
Źródło:
Hydroacoustics; 2013, 16; 121-128
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical results and numerical study on the nonlinear reflection and transmission of plane sound waves
Autorzy:
Wojcik, J.
Gambin, B.
Litniewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/332766.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
theoretical and numerical model
continuity conditions
non-linear waves
lossy media
Opis:
The comparison between theoretical and numerical solutions of the reflection/transmission problem for the acoustic plane wave normally incident on the discontinuity surface between two nonlinear lossy media was presented. Numerical calculations made under the assumption that the two media have the same impedance, allow to single out the effect of nonlinearities in the description of the reflection and transmission phenomena, so they agreed with theoretical predictions. It was shown that theoretically obtained and numerically calculated results mutually confirmed themselves.
Źródło:
Hydroacoustics; 2015, 18; 181-192
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Monitoring during Focused Ultrasound Treatment by Means of the Homodyned K Distribution
Autorzy:
Byra, M.
Kruglenko, E.
Gambin, B.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/1032313.pdf
Data publikacji:
2017-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
temperature monitoring
homodyned K distribution
focused ultrasound
Opis:
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.
Źródło:
Acta Physica Polonica A; 2017, 131, 6; 1525-1528
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 19

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