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Wyszukujesz frazę "Lewandowski, I." wg kryterium: Autor

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    Wyświetlanie 1-6 z 6
    Tytuł:
    Optimization of the Multi-element Synthetic Transmit Aperture Method for Medical Ultrasound Imaging Applications
    Autorzy:
    Tasinkevych, Y.
    Trots, I.
    Nowicki, A.
    Lewandowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177208.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ultrasound imaging
    synthetic aperture
    beamforming
    Opis:
    The paper presents the optimization problem for the multi-element synthetic transmit aperture method (MSTA) in ultrasound imaging applications. The optimal choice of the transmit aperture size is made as a trade-off between the lateral resolution, penetration depth and the frame rate. Results of the analysis obtained by a developed optimization algorithm are presented. The maximum penetration depth and lateral resolution at given depths are chosen as optimization criteria. The results of numerical experiments carried out in MATLAB Ž using synthetic aperture data of point reflectors obtained by the FIELD II simulation program are presented. The visualization of experimental synthetic aperture data of a tissue mimicking phantom and in vitro measurements of the beef liver performed using the SonixTOUCH Research system are also shown.
    Źródło:
    Archives of Acoustics; 2012, 37, 1; 47-55
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cumulative method of the image reconstruction in synthetic aperture. Experimental results
    Autorzy:
    Wójcik, J.
    Trots, I.
    Lewandowski, M.
    Nowicki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/331922.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    An analytical model of imaging using synthetic aperture (SA) methods is presented. This model takes into account: fundamental features of an environment, of an electric transmission/reception path and a description of SA structure – possible schemes of transmission, reception and image formation. Then two schemes are analyzed: a proposed cumulative synthetic transmit aperture (CSTA) and for comparison of the standard STA schemes. For both methods identical basic parameters – equal sequences of transmit and receive transducers were applied. The distinctive feature of CSTA is gathering (summing up) echoes of subsequent transmissions in one acquisition matrix sufficient for image reconstruction. In traditionally applied STA methods a separate acquisition matrix for each transmission is created. Therefore there are a dozen to several dozen more matrices and the time of image reconstruction is at least several times longer than in CSTA. The presented experimental results obtained using wire and tissue mimicking phantoms have shown the comparable imaging quality in both methods.
    Źródło:
    Hydroacoustics; 2012, 15; 195-206
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Golay Coded Sequences in Synthetic Aperture Imaging Systems
    Autorzy:
    Trots, I.
    Tasinkevych, Y.
    Nowicki, A.
    Lewandowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/176941.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ultrasound imaging
    synthetic aperture
    beamforming
    radiation pattern
    coded sequences
    Golay codes
    Opis:
    The paper presents the theoretical and experimental study of synthetic transmit aperture (STA) method combined with Golay coded transmission for medical ultrasound imaging applications. The transmission of long waveforms characterized by a particular autocorrelation function allows to increase the total energy of the transmitted signal without increasing the peak pressure. It can also improve signal- to-noise ratio and increase the visualization depth maintaining the ultrasound image resolution. In the work the 128-element linear transducer array with 0.3 mm pitch excited by the 8 and 16-bits Golay coded sequences as well as a one cycle at nominal frequencies 4 MHz were used. The comparison of 2D ultrasound images of the tissue mimicking phantoms is presented to demonstrate the benefits of coded transmission. The image reconstruction was performed using synthetic STA algorithm with transmit and receive signals correction based on a single element directivity function.
    Źródło:
    Archives of Acoustics; 2011, 36, 4; 913-926
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Multi-Element Synthetic Transmit Aperture in Medical Ultrasound Imaging
    Autorzy:
    Trots, I.
    Nowicki, A.
    Lewandowski, M.
    Tasinkevych, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/177855.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ultrasound imaging
    synthetic aperture
    beamforming
    Opis:
    Synthetic aperture (SA) technique is a novel approach to present day commercial systems and has previously not been used in medical ultrasound imaging. The basic idea of SA is to combine information acquired simultaneously from all directions over a number of emissions and to reconstruct the full image from these data. The paper presents the multi-element STA (MSTA) method for medical ultrasound imaging. The main difference with the STA approach is the use of a few elements in the transmit mode in contrast to a single element aperture. This allows increasing the system frame rate, decreasing the number of emissions, and provides the best compromise between the penetration depth and lateral resolution. Besides, a modified MSTA is proposed with a corresponding RF signal correction in the receive mode, which accounts for the element directivity property. In the experiments a 32-element linear transducer array with 0.48 mm interelement spacing and a burst pulse of 100 ns duration were used. Two elements wide transmission aperture was used to generate an ultrasound wave covering the full image region. The comparison of 2D ultrasound images of a tissue mimicking phantom obtained using the STA and MSTA methods is presented to demonstrate the benefits of the second one.
    Źródło:
    Archives of Acoustics; 2010, 35, 4; 687-699
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of the transducer bandwidth and double pulse transmission on the encoded imaging ultrasound
    Autorzy:
    Trots, I.
    Nowicki, A.
    Lewandowski, M.
    Secomski, W.
    Litniewski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/331651.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    encoded imaging ultrasound
    ultrasound imaging transducer
    CGS
    Opis:
    An influence effect of fractional bandwidth of ultrasound imaging transducer on the gain of compressed echo signal being the complementary Golay sequences (CGS) with different spectral widths is studied in this paper. Also, a new composing transmission method of CGS is discussed together with compression technique applied in order to increase the signal-to-noise ratio (SNR) and penetration. The CGS with two different bit lengths, one-cycle and two-cycles are investigated. Two transducers with fractional bandwidth of 25% and 80% at centre frequency 6 MHz are used. The experimental results are presented, clearly proofing that increasing of the code length leads to compressed echo amplitude enhancement. The smaller the bandwidth is the larger is this effect; the pulse-echo sensitivity of the echo amplitude increases by 1.88 for 25% fractional bandwidth and 1.47 for 80% while preserving time resolution. The presented results of double transmission of short codes show the penetration and SNR improvement while maintaining dead zone.
    Źródło:
    Hydroacoustics; 2008, 11; 419-430
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimation of radial artery reactive response using high frequency ultrasound
    Autorzy:
    Nowicki, A.
    Secomski, W.
    Trawiński, Z.
    Lewandowski, M.
    Trots, I.
    Szubielski, M.
    Olszewski, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/332584.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    thick film transducers
    atherosclerosis
    flow mediated vasodilation
    Opis:
    Background: There is a growing interest in the application of non-invasive clinical tools allowing one to assess the endothelial function, preceding atherosclerosis. The precision in estimating of the artery Flow Mediated Vasodilation (FMD) using standard 10-12 MHz linear array probes does not exceed 0.2 mm, far beyond that required. Methods: We have introduced a wide-band, high frequency 25-30 MHz, Golay encoded wobbling type imaging to measure dilation of the radial artery instead of the brachial one. 18 young volunteers, and 4 volunteers with cardiac events history, were examined. In the second approach 20 MHz linear scanning combined with 20 MHz pulsed Doppler attached to the linear array was used. The radial artery FMD was normalized using shear rate at the radial artery wall. Results and Conclusions: For the “healthy” group, the FMD resulting from reactive hyperemia response was over 20%; while in the “atherosclerotic” group, the FMD was at least twice as small, not exceeding 10%. The shear rate (SR) normalized FMDSR was in the range from 7.8 to 9.9 in arbitrary units, while in patients with minor cardiac history FMDSR was clearly lower, 6.8 to 7.6. The normalized FMDSR of radial artery RARR can be an alternative to the brachial FMD where the precision of measurements is lower and the diameter dilation does not exceed 7-10%.
    Źródło:
    Hydroacoustics; 2016, 19; 297-306
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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