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    Tytuł:
    Thick Film Transducers for High Frequency Coded Ultrasonography
    Autorzy:
    Nowicki, A.
    Lewandowski, M.
    Wójcik, J.
    Tymkiewicz, R.
    Lou-Moller, R.
    Wolny, W.
    Zawada, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/176939.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    transducers
    thick film
    high frequency ultrasound
    pulse compression
    Golay codes
    Opis:
    Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and nonlinear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature – 11 mm, 12 mm, 15 mm, 16 mm. All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The trans- ducers were excited with Golay coded sequences at 35–40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4–1.5 and finally resulting in a SNR gain of the same order.
    Źródło:
    Archives of Acoustics; 2011, 36, 4; 945-954
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    PC-based high frequency imaging system with coded excitation
    Autorzy:
    Lewandowski, M.
    Nowicki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/331588.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    coded transmission
    SNR
    FPGA
    Opis:
    Coded transmission is a technique that gives significant improvement in SNR and enables higher contrast imaging without sacrificing the resolution. A novel HF (20-35 MHz) ultrasound real-time imaging system for research and evaluation of the coded transmission was developed. The digital programmable coder-digitizer module based on the field programmable gate array (FPGA) chip supports arbitrary waveform coded transmission and RF echoes sampling up to 200 MSPS. A novel balanced software architecture supports real-time RF processing and display at rates up to 30 frames/sec. The system was used to gather data for sine burst and 16-bit Golay code excitation using a single element scanning head with thick film focused spherical transducer 25 MHz center frequency and 56% system bandwidth. SNR gain for the Golay codes (referenced to single burst) of 15 dB for 20 MHz and 16 dB for 35 MHz were obtained. In water the axial resolution for both single burst and the Golay codes was the same FWMH=20 ns at 20 MHz and FWMH=15 ns at 35 MHz. The presented system is a practical and low cost implementation of coded excitation technique in HF ultrasound imaging.
    Źródło:
    Hydroacoustics; 2008, 11; 239-247
    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
    Tytuł:
    Statistics of envelope of high frequency ultrasound signal backscattered in human dermis
    Autorzy:
    Piotrzkowska, H.
    Litniewski, J.
    Szymańska, E.
    Lewandowski, M.
    Nowicki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/331987.pdf
    Data publikacji:
    2010
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The scattering of ultrasonic waves depends on the size, shape, acoustical properties and concentration of scatterers in tissue. In these study K distribution of the ultrasound backscatter envelope was used to assess the structural properties of the skin tissue. The custom-designed high frequency ultrasonic scanner was applied to obtain RF B-scans of the skin in vivo at the frequency of 20 ÷ 30MHz. The results are encouraging. The K distribution models the envelope statistics very well. The parameters of the K-distribution, namely, the effective number of scatterers may be useful for the skin characterization.
    Źródło:
    Hydroacoustics; 2010, 13; 205-214
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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