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Wyszukujesz frazę "Kujawska, J." wg kryterium: Autor

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    Tytuł:
    Harmonic ultrasound beams forming by means of radiating source parameters
    Autorzy:
    Kujawska, T.
    Wójcik, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/332171.pdf
    Data publikacji:
    2004
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    In the paper the investigation results of the influence of such parameters as shape and size of the radiating source, as well as waveform, frequency and amplitude of the propagating pulse on the non-linear ultrasonic beam forming are presented. The analysis was carried out on the basis of numerical simulations of the amplitude and harmonic field distributions, in space and time, of two-dimensional beams propagating in water. The applied software (numerical solver), describing the nonlinear propagation of the ultrasonographic pulse wave radiated by the axially symmetrical source in the layered lossy medium for given boundary conditions, was used as the tool to predict the behavior of the ultrasound beam. The algorithm of the above numerical solver, proposed by the second author, is based on the frequency-domain numerical solution of the non-linear wave equation for finite amplitude sound beams. It takes into account the influence of the effects of diffraction, non-linearity and thermoviscous absorption on the propagation of the finite amplitude acoustic beam in attenuating media.
    Źródło:
    Hydroacoustics; 2004, 7; 135-142
    1642-1817
    Pojawia się w:
    Hydroacoustics
    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:
    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:
    Nonlinear and linear pressure determination in a two-layer structure: solid crystal - water at GHz frequencies
    Autorzy:
    Filipczyński, L.
    Wójcik, J.
    Kujawska, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/332574.pdf
    Data publikacji:
    2003
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    pressure determination
    solid crystal
    water
    GHz frequencies
    Opis:
    Determination of acoustic pressures at the frequency of 1 GHz by means of PVDF hydrophones is not possible due to their limited frequency response. Moreover, the size of their active electrodes is by about 3 orders of magnitude greater than the resolution in the acoustic microscopes at such a high frequency. Therefore the authors solved this problem at first in a microscope with the working frequency of 34 MHz using both the numerical and experimental methods. A numerical procedure of nonlinear propagation and transducer power measurements were applied giving in effect the same quantitative results. Therefore the identical numerical procedure was used for the l GHz microscope working in the reflection mode. Many pressure field quantities of the microscope were shown, e.g. the pressure values, distributions of the first, second, third and fourth pressure harmonics in and outside of the focus, pulse distortions and their spectra, the resolutions achieved etc. The obtained information on nonlinear propagation effects in microscopy was previously lacking.
    Źródło:
    Hydroacoustics; 2003, 6; 143-150
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nonlinear ultrasound propagation in water from square focused transducer
    Autorzy:
    Kujawska, T.
    Wójcik, J.
    Nowicki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332715.pdf
    Data publikacji:
    2005
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The nonlinear pulsed acoustic pressure field from a focused square aperture is considered. Experimental measurements in water of a 4D sound field radiated from a 2.8 MHz focused square transducer of a 20 mm side and a 80 mm focal distance for excitation level producing an average acoustic pressure P0 = 0.14 MPa at its surface are presented. The obtained results are compared with the numerical calculation results for the same boundary conditions. The novel, free from paraxial approximation and computationally efficient numerical algorithm was used to simulate the 4D nonlinear pulsed pressure field from the nonaxisymmetric acoustic source. Our theoretical model was based on the Time-Averaged Pressure Envelope (TAPE) method recently developed that enable to represent the propagated pulsed disturbance as a superposition of sinusoidal wavelets with carrier frequencies being the harmonics of the initial tone burst and with envelopes determined by the TAPE method. The novel approach to the solution of the nonlinear wave equation enabled to simulate full 4D nonlinear field for given boundary conditions in a dozen or so minutes utilizing the computational power of the standard PC.
    Źródło:
    Hydroacoustics; 2005, 8; 89-98
    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:
    Wójcik, J.
    Filipczyński, L.
    Kujawska, T.
    Nowicki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332125.pdf
    Data publikacji:
    2004
    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; 2004, 7; 227-234
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Possible temperature increases in soft tissues in the case of nonlinear and linear wave propagation
    Autorzy:
    Filipczyński, L.
    Kujawska, T.
    Tymkiewicz, R.
    Wójcik, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/332225.pdf
    Data publikacji:
    1997
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    It is well known that the nonlinear propagation increases the absorption of acoustic waves in the medium thus increasing the temperature effects. According to the recently developed new theoretical approach it is possible to determine in a simple way the effective absorption in the case of nonlinear propagation basing on the pulse spectrum analysis [Wójcik, 1996]. In this way it was possible to find the corresponding absorption values occuring in ultrasonography. In this case a classical PVDF membrane hydrophone was used to demonstrate and to measure nonlinear effects. Analysing the obtained wave spectra it was possible to determine the increase of the effective tissue absorption and hence to find the rate of heat generation per unit volume which is crucial for temperature elevations In this way possible temperature increases for the case of nonlinear and linear propagation can be determined.
    Źródło:
    Hydroacoustics; 1997, 1; 329-332
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ilościowa ocena nieliniowej propagacji w wodzie i w tkance
    Autorzy:
    Filipczyński, L.
    Kujawska, T.
    Tymkiewicz, R.
    Wójcik, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/331916.pdf
    Data publikacji:
    2000
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    Nonlinear propagation effects were investigated numerically and experimentally u wate r and In blood from the point of view of ultrasonic diagnostic applications in cardlology. Pressure distributions of short and long pulses with the frequency of 3 and 3.5 MHz, radiated by a typical cardiological probe, were found along the ultrasonic beam axis. The numerial results were obtained by means of the numerical code Wf developed previously. The experimental pressure distributions were measured by memu of a membrane PYDF hydrophone. The obtained numerical and experimental results show ing the distributions of the 2-nd and I -st harmonics have shown good agreement allowing us to determine some diagnostic conclusions.
    Źródło:
    Hydroacoustics; 2000, 3; 53-56
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of ultrasound to noninvasive imaging of temperature distribution induced in tissue
    Autorzy:
    Karwat, P.
    Kujawska, T.
    Secomski, W.
    Gambin, B.
    Litniewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/332286.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    HIFU
    echo phase shift
    parametric imaging
    velocity/brightness CNR
    Opis:
    Therapeutic and surgical applications of High Intensity Focused Ultrasound (HIFU) require monitoring of local temperature rises induced inside tissues. It is needed to appropriately target the focal plane, and hence the whole focal volume inside the tumor tissue, prior to thermo-ablative treatment, and the beginning of tissue necrosis. In this study we present an ultrasound method, which calculates the variations of the speed of sound in the locally heated tissue. Changes in velocity correspond to temperature change. The method calculates a 2D distribution of changes in the sound velocity, by estimation of the local phase shifts of RF echo-signals backscattered from the heated tissue volume (the focal volume of the HIFU beam), and received by an ultrasound scanner (23). The technique enabled temperature imaging of the heated tissue volume from the very inception of heating. The results indicated that the contrast sensitivity for imaging of relative changes in the sound speed was on the order of 0.06%; corresponding to an increase in the tissue temperature by about 2 °C.
    Źródło:
    Hydroacoustics; 2016, 19; 219-228
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nonlinear equations of acoustics - numerical solutions and their visualization
    Autorzy:
    Wójcik, J.
    Lewin, P. A.
    Nowicki, A.
    Filipczyński, L.
    Kujawska, T.
    Radulescu, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/331971.pdf
    Data publikacji:
    2003
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    acoustics
    nonlinear equations
    wave equation
    Opis:
    The novel effective numeric solver of the nonlinear scalar wave equation describing the acoustic wave propagation in the attenuating media was derived. The solver was developed for the PC environment. The standard computation data include al! stationary and dynamic characteristics of the radiated ultrasonic pressure field, especially its 4D (space/time) visualization. The results obtained with the solver can be used as the supporting tools (tool) in designing and developments of the multielement linear and phase array transducers applied in ultrasonography.
    Źródło:
    Hydroacoustics; 2003, 6; 137-142
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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