Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "A. J." wg kryterium: Autor

  Lista filtrów
Wyrównaj
Wyświetlanie 1-15 z 41
Tytuł:
Example of Structure Modeling and Analysis of Ultrasound Scattering for Trabecular Bone
Autorzy:
Wójcik, J.
Litniewski, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/177853.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
multi-scattering
random complex structures
trabecular bone model
Opis:
A trabecular bone consists of trabeculae whose mechanical properties differ significantly from the surrounding marrow, therefore an ultrasonic wave propagating within the bone structure is strongly scattered. The aim of this paper was to evaluate the contribution of the first, second and higher order scattering (multiple scattering) into the total scattering of ultrasound in a trabecular bone. The scattering due to the interconnections between thick trabeculae, usually neglected in trabecular bone models, has been also studied. The basic element in our model of the trabecular bone was an elastic cylinder with a various finite-length and diameter as well as orientation. The applied model was taking into account variation of both, elements size and their spatial configuration. The field scattered on the bone model was evaluated by solving numerically the integral form of the generalized Sturm-Liouville equation describing a scalar wave in inhomogeneous and lossy media. For the scattered fields calculated numerically the effective cross-sections were determined. The influence of absorption on the scattering coefficients was demonstrated. The results allowed to conclude that within the frequency range from 0.5 to 1.5 MHz contribution of the second order scattering to the effective backscattering cross-section is at least 500 times lower than that due to the first order scattering. It was noticed that for a frequency higher than 1.5 MHz fast growth of the backscattering (reflection) coefficients, calculated for the second order scattering, occurs.
Źródło:
Archives of Acoustics; 2010, 35, 4; 701-713
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multiple scattering contribution to trabecular bone backscatter
Autorzy:
Wójcik, J.
Litniewski, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/332838.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
bone backscatter
integral equations
spectral distribution
Opis:
Integral equations that describe scattering on the structure with step rise parameters, have been numerically solved on example of the trabecular bone model. The model consists of several hundred elements with randomly selected parameters. The spectral distribution of scatter coefficients in subsequent orders of scattering has been presented.
Źródło:
Hydroacoustics; 2009, 12; 227-236
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preliminary studies of the influence of starch irradiation on physicochemical properties of films prepared using starch and starch-surfactant systems
Autorzy:
Cieśla, K. A.
Nowicki, A.
Buczkowski, M. J.
Powiązania:
https://bibliotekanauki.pl/articles/148406.pdf
Data publikacji:
2010
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
starch films
starch-surfactants films
gamma irradiation
mechanical properties
barrier properties
hydrophobic
Opis:
The influence was studied of potato and wheat starch irradiation on physicochemical properties of films, prepared using either starch alone or a composition of potato starch with three surfactants: sodium laurate, sodium palmitate and cetyl-trimethyl-ammonium bromide (CTAB). The surfactants were introduced at a level of 0.038 division sign 0.075 g per 1 g of starch. This corresponds to 0.136–0.222 mmol/g, depending on the surfactant type and its amount used. Irradiations were carried out using 60Co radiation with doses of 5, 10, 20 and 30 kGy. Films were prepared with addition of glycerol (0, 20 or 30% in terms of starch mass) by means of casting from the gelatinized starch or starch-surfactant solutions. With the purpose to characterize the films, mechanical tests (using an Instron instrument) and the wetting angle measurements were performed. The effect was determined of the storage and conditioning in an atmosphere characterized by the various moisture content on the properties of films with various compositions. The results show the radiation-induced improvement of hydrophobic properties of the films prepared using potato and wheat starch, and the selected potato starch-surfactant compositions. Improvement of strength and flexibility was obtained in the case of potato starch films, while in the case of wheat starch films the increase of strength was accompanied by a decrease in flexibility. Improvement of the functional properties of potato starch films corresponds to the improvement of their structural properties, found by scanning electron microscopy (SEM). The possibilities of modification of the films properties by modification of composition and radiation treatment were discussed.
Źródło:
Nukleonika; 2010, 55, 2; 233-242
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tissue Attenuation Estimation from Backscattered Ultrasound Using Spatial Compounding Technique - Preliminary Results
Autorzy:
Klimonda, Z.
Litniewski, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/177842.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ultrasound attenuation estimation
spatial compounding
parametric imaging
Opis:
The pathological states of biological tissue are often resulted in attenuation changes. Thus, information about attenuating properties of tissue is valuable for the physician and could be useful in ultrasonic diagnosis. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The attenuation estimation method based on the echoes mean frequency changes due to tissue attenuation dispersion, is presented. The Doppler IQ technique was adopted to estimate the mean frequency directly from the raw RF data. The Singular Spectrum Analysis technique was used for the extraction of mean frequency trends. These trends were converted into attenuation distribution and finally the parametric images were computed. In order to reduce variation of attenuation estimates the spatial compounding method was applied. Operation and accuracy of attenuation extracting procedure was verified by calculating the attenuation coefficient distribution using the data from the tissue phantom (DFS, Denmark) with uniform echogenicity while attenuation coefficient underwent variation.
Źródło:
Archives of Acoustics; 2010, 35, 4; 643-651
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using Empirical Mode Decomposition of Backscattered Ultrasound Signal Power Spectrum for Assessment of Tissue Compression
Autorzy:
Byra, M.
Wójcik, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/177950.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
tissue characterization
tissue compression
quantitative ultrasound
empirical mode decomposition
signal analysis
Opis:
Quantitative ultrasound has been widely used for tissue characterization. In this paper we propose a new approach for tissue compression assessment. The proposed method employs the relation between the tissue scatterers’ local spatial distribution and the resulting frequency power spectrum of the backscattered ultrasonic signal. We show that due to spatial distribution of the scatterers, the power spectrum exhibits characteristic variations. These variations can be extracted using the empirical mode decomposition and analyzed. Validation of our approach is performed by simulations and in-vitro experiments using a tissue sample under compression. The scatterers in the compressed tissue sample approach each other and consequently, the power spectrum of the backscattered signal is modified. We present how to assess this phenomenon with our method. The proposed in this paper approach is general and may provide useful information on tissue scattering properties.
Źródło:
Archives of Acoustics; 2018, 43, 3; 447-453
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical modeling of ultrasound-induced temperature fields in multilayer nonlinear attenuating media
Autorzy:
Kujawska, T.
Wójcik, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/332786.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
numerical modeling
ultrasound
attenuating media
Opis:
Ultrasound is a safe, convenient and inexpensive modality which may be useful for soft tissues treatment. A range of beneficial biological effects induced by ultrasound depends on the exposure levels used during treatment. At high intensities instantaneous tissue necrosis is desired, whereas at lower intensities remedial reversible cellular effects may be produced. For example, increasing of cells immunity against stress can be obtained through the heat shock proteins (Hsp) expression enhancement. The possibility of the Hsp expression enhancement in soft tissues in vivo by means of controlled exposure to ultrasound would allow to evaluate the treatment efficiency. Ultrasonic regimes can be controlled by adjusting the ultrasound intensity, frequency, pulse duration, duty cycle and exposure time. The goal of this work was to develop the numerical model capable of predicting in space and time the temperature fields induced by circular focused transducer generating tone bursts in multilayer nonlinear attenuating media, which is intended for the Hsp expression enhancement therapeutic application. The acoustic pulsed pressure field generated from the transducer was calculated using our original 3D numerical solver [1]. For prediction of the temperature distributions in multilayer biological media the Pennes bio-heat transfer equation was numerically solved. The 3D temperature fields induced in a rat liver in vitro by a 2 MHz transducer with 15 mm diameter and 25 mm focal length during ultrasonic Hsp expression enhancement treatment using various acoustic beam intensities and exposure time was predicted.
Źródło:
Hydroacoustics; 2009, 12; 91-97
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Applying crystallography in analysis of trabecular bone backscatter
Autorzy:
Wojcik, J.
Litniewski, J.
Nowicki, A.
Gambin, B.
Powiązania:
https://bibliotekanauki.pl/articles/332506.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Some important details of the Backscatter Effective Cross-Sections obtained for random scattering structures (like trabecular bone) are explain by comparison with the results obtained by means of the simplified theoretical model. The simplified model was (establish) and justified on the basis of the structural analysis of the results obtained for exact model of the field scattering on complex structures. The simplified model is commonly used in description of the scattering on the regular structures like crystal. Comparison with experimental results for the trabecular bone is also presented. The results allowed to conclude that crystallographic methods could be potentially useful for extracting characteristic features of trabecular bone.
Źródło:
Hydroacoustics; 2011, 14; 255-266
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasound imaging of stiffness with two frequency pulses
Autorzy:
Nowicki, A.
Byra, M.
Litniewski, J.
Wójcik, J.
Powiązania:
https://bibliotekanauki.pl/articles/332602.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Nowadays there are new modalities in ultrasound imaging allowing better characterization of tissue regions with different stiffness. We are proposing a novel approach based on compression and rarefaction of tissue simultaneously with imaging. The propagating wave is a combination of two pulses. A low frequency pulse is expected to change the local scattering properties of the tissue due to compression/rarefaction while a high frequency pulse is used for imaging. Two transmissions are performed for each scanning line. First, with the imaging pulse that propagates on maximum compression caused by a low frequency wave. Next, the low frequency wave is inverted and the imaging pulse propagates over the maximum rarefaction. After the processing of the subtracted echoes from subsequent transmissions including wavelet transform and band-pass filtering, differential images were reconstructed. The low frequency wave has a visible impact on the scattering properties of the tissue which can be observed on a differential image.
Źródło:
Hydroacoustics; 2014, 17; 151-160
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical analysis of ultrasound echo for skin lesions classification
Autorzy:
Piotrzkowska, H.
Litniewski, J.
Szymańska, A.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331930.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Propagation of ultrasonic waves in the tissue is sensitive to the alternation of tissue composition and structure.. This paper presents the classification of healthy skin and skin lesions (basal cell carcinoma (BCC)) based on statistic parameters of the envelope of echosignal. The statistics of envelope of the ultrasonic signal was modeled using Rayleigh and non-Rayleigh (the K-distribution) statistics. Furthermore the characteristic parameter of K-distribution, the effective number of scaterrers (M) was investigated. Comparison of the results obtained for region of the skin where the BCC was diagnosed and the regions of healthy skin has shown differences in the values of M parameter. These results indicate that this parameter has the potential for extracting information useful for characterizing skin lesions.
Źródło:
Hydroacoustics; 2012, 15; 171-178
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multitone nonlinear coding
Autorzy:
Nowicki, A.
Wójcik, J.
Secomski, W.
Powiązania:
https://bibliotekanauki.pl/articles/331604.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
MNC method
virtual fields
acoustic source
Opis:
A new method that utilizes nonlinear properties of tissue (or another media) to improve ultrasound image resolution is presented. In our novel method the acoustic source is activated with two tones burst (2.2 and 4.4 MHz) with specially designed polarization of the individual tone burst. This new approach is called multi tone nonlinear coding MNC because the choice of polarization of the both tones (and their amplitudes) allowing optimization of the receiving properties depends on the nonlinear properties of tissue. The calculations were done for two tones bursts propagating in the tissue-like lossy medium with absorption of 7 Np/mźMHz. The concept of the Virtual Fields was introduced to explain abilities and properties of pulse inversion and MNC method and to compare both. Comparison of the spatial field distribution obtained using MNC and conventional harmonic imaging approach, in which the first harmonic is used to reconstruct the image are presented.
Źródło:
Hydroacoustics; 2008, 11; 289-298
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A spectral-based method for tissue characterization
Autorzy:
Wójcik, J.
Byra, M.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331796.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
quantitative ultrasound
signal analysis
wave scattering
Opis:
Quantitative ultrasound methods are widely investigated as a promising tool for tissue characterization. In this paper, a novel quantitative method is developed which can be used to assess scattering properties of tissues. The proposed method is based on analysis of oscillations of the backscattered echo power spectrum. It is shown that these oscillations of the power spectrum are connected with the distances between scatterers within the medium. Two techniques are proposed to assess the scatterer’s distribution. First, we show that the inverse Fourier transform of the backscattered echo power spectrum corresponds to a histogram of the distances between scatterers. Second, the Hilbert-Huang transform is used to directly extract the power spectrum oscillations. Both methods are examined by means of a numerical experiment. A cellular gas model of a biological medium is considered. Results are presented and discussed. Both methods can be used to evaluate the scatterer’s distribution by means of the power spectrum oscillations.
Źródło:
Hydroacoustics; 2016, 19; 369-375
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parametric sonographic imaging - application of synthetic aperture technique to imaging attenuation of ultrasound in tissue structures
Autorzy:
Litniewski, J.
Klimonda, Z.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331882.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Ultrasonic imaging is a well-established technique in medicine. However, in most conventional applications of clinical ultrasonic scanners only the peak amplitude echogenicity is used to create the image. Moreover, signal envelope detection destroys potentially useful information about frequency dependence of acoustic properties of tissue comprised in RF backscattered echoes. We have explored the possibility of developing the method of imaging the distribution of the acoustic attenuation in tissue. We expect that the method will help in localization of the pathological states of tissue including tumors and diffuse liver diseases. The spatial resolution and precision of the method are crucial for medical diagnosis, hence the synthetic aperture technique was applied for ultrasonic data collection. The final goal of the presented project is to develop reliable diagnostic tool, which could be implemented in standard USG systems, as the new visualization mode.
Źródło:
Hydroacoustics; 2012, 15; 99-110
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature fields induced in rat liver in vitro by pulsed low intensity focused ultrasound
Autorzy:
Kujawska, T.
Wójcik, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331934.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Beneficial biological effects in soft tissues can be induced by focused ultrasound of low intensity (LIFU). For example, increasing of cells immunity to stress can be accomplished through the enhanced heat shock proteins (Hsp) expression induced by the low intensity focused ultrasound. The possibility to control the Hsp expression enhancement in soft tissues in vivo can be the potential new therapeutic approach to neurodegenerative diseases that utilizes the known feature of cells to increase their immunity to stresses through the Hsp expression enhancement. The controlling of the Hsp expression enhancement by adjusting the level of exposure to ultrasound energy would allow evaluating of ultrasound-mediated treatment efficiency. Our objective was to develop the numerical model capable of predicting in space and time temperature fields induced in multilayer nonlinear attenuating media by a circular focused transducer generating pulsed acoustic waves and to compare the results calculated for two-layer configuration of media: water - fresh rat liver with the experimental data. The measurements of temperature variations versus time at 5 points on the acoustic beam axis within the tissue sample were performed using 0.2-mm diameter thermocouples. Temperature fields were induced by the transducer with 15-mm diameter, 25-mm focal length and 2-MHz centre frequency generating tone bursts with the intensity ISPTA varied between 0.45 W/cm2 and 1.7 W/cm2 and duration varied between 20 and 500 cycles at the same 20-% duty cycle and 20-min exposure time. Quantitative analysis of the obtained results allowed to show that, for example, for the acoustic beam with intensity ISPTA = 1.13 W/cm2 exposure time to ultrasound should not be longer than 10 min to avoid cells necrosis following the 43-oC temperature threshold exceeding.
Źródło:
Hydroacoustics; 2010, 13; 153-162
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Preliminary results of attenuation estimation from tissue backscatter using commercial ultrasonic scanner
Autorzy:
Klimonda, Z.
Litniewski, J.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/331943.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
Ultrasonography (USG) is a widespread and powerful tool used successfully in modern diagnostics. The standard USG scanner reflects impedance variations within the tissue that is penetrated by the ultrasound pulse. Although such image provides a lot of information to the physician, there are another parameters which could be imaged. The attenuation coefficient is one of them. Imaging of attenuation seems to be a promising tool for ultrasonic medical diagnostics. The attenuation estimation method based on the echoes mean frequency changes due to tissue attenuation dispersion is presented. The Doppler IQ technique is adopted to estimate the mean frequency changes directly from the raw RF data. The Singular Spectrum Analysis (SSA) technique is used for the mean frequency trend extraction. The changes of the mean frequency trend are related directly to the local attenuation coefficient. Preliminary results of the tissue phantom attenuation coefficient estimation and imaging using the commercial scanner are presented.
Źródło:
Hydroacoustics; 2010, 13; 127-134
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Foundation of the new method of numerical calculations of the nonlinear acoustics fields
Autorzy:
Wojcik, J.
Filipczyński, L.
Nowicki, A.
Powiązania:
https://bibliotekanauki.pl/articles/332217.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Akustyczne
Opis:
We explain, motivation behind this work and briefly describe foundation of new method which we have developed for efficient solution in PC environment of the nonlinear propagation equation with the boundary conditions applied for both circular and not circular transducers (like array). Comparison between new and old method will be presented for strongly nonlinear disturbance. At the end we will demonstrate the results of the numerical calculations of the nonlinear field propagating from the array.
Źródło:
Hydroacoustics; 2013, 16; 253-262
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 41

Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies