Piotr Karwat, M.Sc., Eng.

Department of Ultrasound (ZU)
Division of Acoustic Microscopy (PMAk)
position: senior programmer
telephone: (+48) 22 826 12 81 ext.: 314
room: 522
e-mail: pkarwat

Recent publications
1.Karwat P., Kujawska T., Lewin P.A., Secomski W., Gambin B., Litniewski J., Determining temperature distribution in tissue in the focal plane of the high (>100 W/cm2) intensity focused ultrasound beam using phase shift of ultrasound echoes, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2015.10.002, Vol.65, pp.211-219, 2016
Abstract:

In therapeutic applications of High Intensity Focused Ultrasound (HIFU) the guidance of the HIFU beam and especially its focal plane is of crucial importance. This guidance is needed to appropriately target the focal plane and hence the whole focal volume inside the tumor tissue prior to thermo-ablative treatment and beginning of tissue necrosis. This is currently done using Magnetic Resonance Imaging that is relatively expensive. In this study an ultrasound method, which calculates the variations of speed of sound in the locally heated tissue volume by analyzing the phase shifts of echo-signals received by an ultrasound scanner from this very volume is presented. To improve spatial resolution of B-mode imaging and minimize the uncertainty of temperature estimation the acoustic signals were transmitted and received by 8 MHz linear phased array employing Synthetic Transmit Aperture (STA) technique. Initially, the validity of the algorithm developed was verified experimentally in a tissue-mimicking phantom heated from 20.6 to 48.6°C. Subsequently, the method was tested using a pork loin sample heated locally by a 2 MHz pulsed HIFU beam with focal intensity ISATA of 129 W/cm2. The temperature calibration of 2D maps of changes in the sound velocity induced by heating was performed by comparison of the algorithm-determined changes in the sound velocity with the temperatures measured by thermocouples located in the heated tissue volume. The method developed enabled ultrasound temperature imaging of the heated tissue volume from the very inception of heating with the contrast-to-noise ratio of 3.5–12 dB in the temperature range 21–56°C. Concurrently performed, conventional B-mode imaging revealed CNR close to zero dB until the temperature reached 50°C causing necrosis. The data presented suggest that the proposed method could offer an alternative to MRI-guided temperature imaging for prediction of the location and extent of the thermal lesion prior to applying the final HIFU treatment.

Keywords:

Ultrasonic temperature imaging, HIFU, Echo phase shift, Velocity image contrast

Affiliations:
Karwat P.-IPPT PAN
Kujawska T.-IPPT PAN
Lewin P.A.-Drexel University (US)
Secomski W.-IPPT PAN
Gambin B.-IPPT PAN
Litniewski J.-IPPT PAN
2.Lewandowski M., Walczak M., Karwat P., Witek B., Karłowicz P., Research and Medical Transcranial Doppler System, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.1515/aoa-2016-0074, Vol.41, No.4, pp.773-781, 2016
Abstract:

A new ultrasound digital transcranial Doppler system (digiTDS) is introduced. The digiTDS enables diagnosis of intracranial vessels which are rather difficult to penetrate for standard systems. The device can display a color map of flow velocities (in time-depth domain) and a spectrogram of a Doppler signal obtained at particular depth. The system offers a multigate processing which allows to display a number of spectrograms simultaneously and to reconstruct a flow velocity profile.
The digital signal processing in digiTDS is partitioned between hardware and software parts. The hardware part (based on FPGA) executes a signal demodulation and reduces data stream. The software part (PC) performs the Doppler processing and display tasks. The hardware-software partitioning allowed to build a flexible Doppler platform at a relatively low cost.
The digiTDS design fulfills all necessary medical standards being a new useful tool in the transcranial field as well as in heart velocimetry research.

Keywords:

Doppler system, digital signal processing, hardware-software partitioning, field programmable gate arrays

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Karwat P.-IPPT PAN
Witek B.-IPPT PAN
Karłowicz P.-other affiliation
3.Karwat P., Kujawska T., Secomski W., Gambin B., Litniewski J., Application of ultrasound to noninvasive imaging of temperature distribution induced in tissue, HYDROACOUSTICS, ISSN: 1642-1817, Vol.19, pp.219-228, 2016
Abstract:

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.

Keywords:

HIFU, echo phase shift, parametric imaging, velocity/brightness CNR

Affiliations:
Karwat P.-IPPT PAN
Kujawska T.-IPPT PAN
Secomski W.-IPPT PAN
Gambin B.-IPPT PAN
Litniewski J.-IPPT PAN
4.Karwat P., Litniewski J., Kujawska T., Secomski W., Krawczyk K., Noninvasive Imaging of Thermal Fields Induced in Soft Tissues In Vitro by Pulsed Focused Ultrasound Using Analysis of Echoes Displacement, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.2478/aoa-2014-0014, Vol.39, No.1, pp.139-144, 2014
Abstract:

Therapeutic and surgical applications of focused ultrasound require monitoring of local temperature rises induced inside tissues. From an economic and practical point of view ultrasonic imaging techniques seem to be the most suitable for the temperature control. This paper presents an implementation of the ultrasonic echoes displacement estimation technique for monitoring of local temperature rise in tissue during its heating by focused ultrasound The results of the estimation were compared to the temperature measured with thermocouple. The obtained results enable to evaluate the temperature fields induced in tissues by pulsed focused ultrasonic beams using non-invasive imaging ultrasound technique

Keywords:

HIFU, therapeutic ultrasound, ultrasonic imaging, echo strain estimation

Affiliations:
Karwat P.-IPPT PAN
Litniewski J.-IPPT PAN
Kujawska T.-IPPT PAN
Secomski W.-IPPT PAN
Krawczyk K.-IPPT PAN
5.Klimonda Z., Litniewski J., Karwat P., Nowicki A., Spatial and Frequency Compounding in Application to Attenuation Estimation in Tissue, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.2478/aoa-2014-0056, Vol.39, No.4, pp.519-527, 2014
Abstract:

The soft tissue attenuation is an interesting parameter from medical point of view, because the value of attenuation coefficient is often related to the state of the tissue. Thus, the imaging of the attenuation coefficient distribution within the tissue could be a useful tool for ultrasonic medical diagnosis. The method of attenuation estimation based on tracking of the mean frequency changes in a backscattered signal is presented in this paper. The attenuation estimates are characterized by high variance due to stochastic character of the backscattered ultrasonic signal and some special methods must be added to data processing to improve the resulting images. The following paper presents the application of Spatial Compounding (SC), Frequency Compounding (FC) and the combination of both. The resulting parametric images are compared by means of root-mean-square errors. The results show that combined SC and FC techniques significantly improve the quality and accuracy of parametric images of attenuation distribution.

Keywords:

tissue attenuation estimation, parametric imaging, synthetic aperture, spatial compounding, frequency compounding

Affiliations:
Klimonda Z.-IPPT PAN
Litniewski J.-IPPT PAN
Karwat P.-IPPT PAN
Nowicki A.-IPPT PAN
6.Gawlikowski M., Lewandowski M., Nowicki A., Kustosz R., Walczak M., Karwat P., Karłowicz P., The Application of Ultrasonic Methods to Flow Measurement and Detection of Microembolus in Heart Prostheses, ACTA PHYSICA POLONICA A, ISSN: 0587-4246, DOI: 10.12693/APhysPolA.124.417, Vol.124, No.3, pp.417-420, 2013
Abstract:

For the last 20 years the world cardiosurgery has presented a considerable change of attitude to mechanical circulatory support. In spite of technological progress the main problems in ventricular assist devices are: thrombosis and low accuracy of flow measurements. In this paper the prototype of multi-gate Doppler flowmeter intended for cardiac assist system ReligaHeart EXT has been presented as well as the possibility of ultrasonic micro embolus detection.

Keywords:

artificial heart, microemboli, ultrasound Doppler

Affiliations:
Gawlikowski M.-other affiliation
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
Kustosz R.-other affiliation
Walczak M.-IPPT PAN
Karwat P.-IPPT PAN
Karłowicz P.-other affiliation
7.Karwat P., Klimonda Z., Seklewski M., Lewandowski M., Nowicki A., Data reduction method for synthetic transmit aperture algorithm, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.35, No.4, pp.635-642, 2010
Abstract:

Ultrasonic methods of human body internal structures imaging are being continuously enhanced. New algorithms are created to improve certain output parameters. A synthetic aperture method (SA) is an example which allows to display images at higher frame-rate than in case of conventional beam-forming method. Higher computational complexity is a limitation of SA method and it can prevent from obtaining a desired reconstruction time. This problem can be solved by neglecting a part of data. Obviously it implies a decrease of imaging quality, however a proper data reduction technique would minimize the image degradation. A proposed way of data reduction can be used with synthetic transmit aperture method (STA) and it bases on an assumption that a signal obtained from any pair of transducers is the same, no matter which transducer transmits and which receives. According to this postulate, nearly a half of the data can be ignored without image quality decrease. The presented results of simulations and measurements with use of wire and tissue phantom prove that the proposed data reduction technique reduces the amount of data to be processed by half, while maintaining resolution and allowing only a small decrease of SNR and contrast of resulting images.

Keywords:

ultrasonic imaging, synthetic transmit aperture, data reduction, effective aperture, reciprocity

Affiliations:
Karwat P.-IPPT PAN
Klimonda Z.-IPPT PAN
Seklewski M.-other affiliation
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
8.Sęklewski M., Karwat P., Klimonda Z., Lewandowski M., Nowicki A., Preliminary results: comparison of different schemes of synthetic aperture technique in ultrasonic imaging, HYDROACOUSTICS, ISSN: 1642-1817, Vol.13, pp.243-252, 2010
Abstract:

The Synthetic Aperture (SA) methods are widespread and successfully used in radar technology, as well as in the sonar systems. The advantages of high framerate and its relatively good resolution in the whole area of scanning, make this technique an object of interest in medical imaging methods such as ultrasonography (US). This paper describes the possible usage of the SA method in ultrasound imaging. The introduction to the principles of the SA technique in ultrasonography is presented. The measurements of different SA schemes were conducted using the set-up consisting of the research ultrasonograph module, the PC and the special wire phantom. The results for different schemes of image reconstruction are presented. Particularly the Synthetic Transmit Aperture (STA) technique was concerned. Results of the STA method are discussed in this paper.

Keywords:

synthetic aperture focusing technique, ultrasonic imaging

Affiliations:
Sęklewski M.-IPPT PAN
Karwat P.-IPPT PAN
Klimonda Z.-IPPT PAN
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
9.Karwat P., Nowicki A., Lewandowski M., Blood scattering model for pulsed doppler, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.34, No.4, pp.677-685, 2009
Abstract:

The subject of this paper is a new software simulating ultrasound signal scattered on moving blood cells during Doppler examination of blood flow velocity using pulsed technique. Generated data are used for optimization and validation of Doppler signals processing algorithms.
The algorithm is based on the finite elements method FEM. A rigorous set of postulates which simplifies physics of modeled phenomenon enables to quicken the program significantly while preserving important properties (from application point of view) of generated signal.
The paper includes description of Doppler RF signal generation algorithm. The simplifying postulates are listed together with resulting signal fidelity degradation. Finally generated raw data is presented together with its Doppler Audio and Color processed version.
The signal processing results enable to reconstruct correctly the velocity profile and its time dependence. The results clearly confirm that the data generated by the algorithm are suitable for Doppler signals processing.

Keywords:

RF signal simulation, scattering on blood cells, pulsed Doppler

Affiliations:
Karwat P.-IPPT PAN
Nowicki A.-IPPT PAN
Lewandowski M.-IPPT PAN

List of chapters in recent monographs
1.
495
Litniewski J., Klimonda Z., Karwat P., Piotrzkowska-Wróblewska H., Dobruch-Sobczak K., Tymkiewicz R., Gambin B., Postępy Akustyki 2016, rozdział: Cancer malignancy sonic markers, Polskie Towarzystwo Akustyczne, Oddział Warszawski, Warszawa, Poland, pp.49-60, 2016
2.
497
Karwat P., Postępy Akustyki 2016, rozdział: Wydajna obliczeniowo metoda rekonstrukcji pola prędkości dźwięku w tkankach miękkich, Polskie Towarzystwo Akustyczne, Oddział Warszawski, Warszawa, Poland, Instytut Podstawowych Problemów Techniki PAN, pp.27-38, 2016
3.
328
Lewandowski M., Walczak M., Karwat P., Nowicki A., Karłowicz P., Polskie protezy serca, opracowanie konstrukcji, badania kwalifikacyjne, przedkliniczne i kliniczne., rozdział: Wykonanie modelu i implementacja oprogramowania do ultradźwiękowego pomiaru przepływu krwi, FRK, Zabrze. Praca zbiorowa pod redakcją: Kustosz R., Gonsior M., Jarosz A., pp.3-21, 2013

Conference papers
1.Steifer T., Lewandowski M., Karwat P., Gawlikowski M., Automatic emboli detection system for the artificial heart, Physics Procedia, ISSN: 1875-3892, DOI: 10.1016/j.phpro.2015.08.254, Vol.70, pp.1181-1184, 2015
Abstract:

In spite of the progress in material engineering and ventricular assist devices construction, thromboembolism remains the most crucial problem in mechanical heart supporting systems. Therefore, the ability to monitor the patient’s blood for clot formation should be considered an important factor in development of heart supporting systems. The well-known methods for automatic embolus detection are based on the monitoring of the ultrasound Doppler signal. A working system utilizing ultrasound Doppler is being developed for the purpose of flow estimation and emboli detection in the clinical artificial heart ReligaHeart EXT. The system will be based on the existing dual channel multi-gate Doppler device with RF digital processing. A specially developed clamp-on cannula probe, equipped with 2 − 4MHz piezoceramic transducers, enables easy system setup. We present the issues related to the development of automatic emboli detection via Doppler measurements. We consider several algorithms for the flow estimation and emboli detection. We discuss their efficiency and confront them with the requirements of our experimental setup. Theoretical considerations are then met with preliminary experimental findings from a) flow studies with blood mimicking fluid and b) in-vitro flow studies with animal blood. Finally, we discuss some more methodological issues - we consider several possible approaches to the problem of verification of the accuracy of the detection system.

Keywords:

microemboli, embolism, Doppler ultrasound, ventricular assist device

Affiliations:
Steifer T.-IPPT PAN
Lewandowski M.-IPPT PAN
Karwat P.-IPPT PAN
Gawlikowski M.-other affiliation
2.Klimonda Z., Litniewski J., Karwat P., Secomski W., Nowicki A., Tissue attenuation imaging - Synthetic Aperture Focusing versus Spatial Compounding, IUS 2012, IEEE International Ultrasonics Symposium, 2012-10-07/10-10, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0590, pp.2361-2363, 2012
Abstract:

The long term goal of this research is to develop the system enabling the imaging and quantitative measure of ultrasonic attenuation in tissue. It may support the diagnosis by accurate discrimination of the lesions from normal tissue at the early stage of the disease. The attenuation is estimated from the stochastic ultrasonic backscatter and time/spatial averaging is necessary to achieve reasonable accuracy. However the averaging worsens the spatial resolution. Two techniques of ultrasonic imaging, the Synthetic Aperture Focusing technique (SAFT) and Spatial Compounding (SC), were applied and compared with respect to the quality of attenuation estimation. The ultrasonic RF data were collected from a tissue mimicking phantom using ultrasonic scanner (Ultrasonix SonixTOUCH). Both acquired echoes-sets were processed in the same way in order to calculate the downshift in a mean frequency fm of the backscatter signal and resulting spatial distribution of attenuation coefficient. Compensation for the diffraction effects was included in the data processing. The RF data obtained with use of the SAFT proved to be more suitable for attenuation estimation.

Keywords:

tissue attenuation imaging, synthetic aperture, spatial compounding

Affiliations:
Klimonda Z.-IPPT PAN
Litniewski J.-IPPT PAN
Karwat P.-IPPT PAN
Secomski W.-IPPT PAN
Nowicki A.-IPPT PAN
3.Karwat P., Klimonda Z., Lewandowski M., Nowicki A., Imaging Quality of the Classical Beamforming, SAFT and Plane Wave Imaging – Experimental Results, IUS 2012, IEEE International Ultrasonics Symposium, 2012-10-07/10-10, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0320, pp.1283-1286, 2012
Abstract:

The synthetic aperture focusing techniques (SAFT) are well known and widely deployed in radar techniques. Increasing processing power of modern computers allows effective implementation of various SAFT schemes in medical ultrasound systems with multi-element probes. The advance of the SAFT over the classical beamforming (BFR) is dynamic focusing in receive and transmit as well, which brings high resolution on every imaging point. We intend to develop the ultrasound imaging platform with some of the SAFT schemes implemented. The choice of the scheme must be preceded by examination of the imaging quality parameters. The results of the comparison of different SAFT schemes with conventional beamforming are presented in the paper. The results indicate that SAFT schemes can work better than BFR scheme. For example, for some point located near the center of the image the full width at half maximum (FWHM) was equal approximately 0.5, 0.4 and 0.3 mm, while the contrast-to-noise ratio (CNR) was equal 18, 19, and 19 dB for BFR, STA and PWI respectively.

Keywords:

Ultrasonic imaging, SAFT, Plane Wave Imaging

Affiliations:
Karwat P.-IPPT PAN
Klimonda Z.-IPPT PAN
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
4.Lewandowski M., Karwat P., Kudelka J., Kleczek T., GPU Implementation of the STA Algorithm on I/Q Data, IUS 2012, IEEE International Ultrasonics Symposium, 2012-10-07/10-10, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0564, pp.2258-2261, 2012
Abstract:

GPU computing is a new paradigm in high performance signal and image processing. Massive parallel processing offered by the GPUs provides high acceleration of computations when they are properly implemented. Ultrasound image reconstruction is one of these highly parallel classes of algorithms. Massive amount of multichannel input data and deterministic order of execution makes US applications good candidates for high performance GPU implementation. Our goal is to design a versatile ultrasound platform with GPU real-time processing. The project is based on a new system architecture allowing for bandwidth and scalability of processing power. We implemented and optimized SAFT image reconstruction algorithms on CUDA. The study shows that a single GTX-580 GPU card is capable of reconstructing the 128-channel I/Q data into 256×256 High Resolution Images (HRI) at a frame-rate of 44.64 fps which is an equivalent of 5700 Low Resolution Images (LRI) per second.

Keywords:

ultrasonic imaging, synthetic aperture, GPU, CUDA

Affiliations:
Lewandowski M.-IPPT PAN
Karwat P.-IPPT PAN
Kudelka J.-other affiliation
Kleczek T.-other affiliation
5.Karwat P., Litniewski J., Secomski W., Kujawska T., Krawczyk K., Kruglenko E., Gambin B., Nowicki A., Nieinwazyjne obrazowanie temperatury tkanki miękkiej in vitro metodą analizy przemieszczenia ech ultradźwiękowych, 59th Open Seminar on Acoustics, 2012-09-10/09-14, Boszkowo (PL), pp.101-104, 2012
Abstract:

Terapeutyczne i chirurgiczne zastosowania ogniskowych ultradźwięków wymagają monitorowania lokalnych zmian temperatury w tkance. Najkorzystniejsze z punktu widzenia użytkowego i ekonomicznego byłoby zastosowanie do tych celów technik ultradźwiękowych.
Praca przedstawia próbę zastosowania metody estymacji przemieszczenia ech do monitorowania zmian temperatury podczas ultradźwiękowego nagrzewania tkanki in vitro. Dane uzyskane drogą pomiarów ultradźwiękowych zostały przetworzone w celu wyznaczenia mapy przemieszczeń ech i odniesione do pomiarów rozkładu temperatury przeprowadzonych za pomocą termopar. Uzyskane wyniki umożliwiają ocenę pola temperatury i pozytywnie rokują połączeniu ultradźwiękowych technik nagrzewania i szacowania lokalnej temperatury tkanki.

Keywords:

obrazowanie temperatury, prędkość akustyczna

Affiliations:
Karwat P.-IPPT PAN
Litniewski J.-IPPT PAN
Secomski W.-IPPT PAN
Kujawska T.-IPPT PAN
Krawczyk K.-IPPT PAN
Kruglenko E.-IPPT PAN
Gambin B.-IPPT PAN
Nowicki A.-IPPT PAN
6.Karwat P., Litniewski J., Secomski W., Kujawska T., Krawczyk K., Kruglenko E., Gambin B., Non-invasive imaging of thermal fields induced in soft tissues in vitro by focused ultrasound using analysis of ultrasonic echoes displacement, International Conference Biomedical Engineering, 2012-10-25/10-26, Kaunas (LT), pp.66-72, 2012
Abstract:

Therapeutic and surgical applications of focused ultrasound require monitoring of local temperature rises induced inside tissues. From an economic and practical point of view ultrasonic imaging techniques seem to be the best for a temperature control. In this work an attempt to apply the method of the ultrasonic echoes displacement estimation for monitoring local temperature rises in tissues during their heating by focused ultrasound is presented. The estimated temperature rise was compared with this measured by a thermocouple. The obtained results enable to evaluate the temperature fields induced in tissues by pulsed focused ultrasonic beams using non-invasive imaging ultrasound technique.

Keywords:

HIFU, therapeutic ultrasound, ultrasonic imaging, echo strain estimation

Affiliations:
Karwat P.-IPPT PAN
Litniewski J.-IPPT PAN
Secomski W.-IPPT PAN
Kujawska T.-IPPT PAN
Krawczyk K.-IPPT PAN
Kruglenko E.-IPPT PAN
Gambin B.-IPPT PAN
7.Karwat P., Klimonda Z., Sęklewski M., Lewandowski M., Nowicki A., Metoda przerzedzania danych dla algorytmu syntetycznej apertury nadawczej, 57 Otwarte Seminarium z Akustyki, 2010-09-20/09-24, Gliwice (PL), pp.91-94, 2010
Abstract:

Metody ultradźwiękowego obrazowania struktur wewnętrznych człowieka są nieustannie ulepszane. Opracowywane są nowe algorytmy umożliwiające poprawę niektórych parametrów wynikowych. Przykładem jest metoda syntetycznej apertury (SA), która pozwala wyświetlać obrazy o wysokiej rozdzielczości z większą częstotliwością niż standardowa metoda formowania wiązki.
Ograniczeniem metody SA jest większa złożoność obliczeniowa, która przy znacznej ilości danych może uniemożliwić osiągnięcie pożądanej szybkości rekonstrukcji. Problem ten można ominąć rezygnując z części zarejestrowanych sygnałów. Wiąże się to oczywiście z pogorszeniem jakości obrazowania, jednak przy odpowiedniej technice przerzedzania danych degradacja obrazu jest niewielka. Proponowany sposób przerzedzania ma zastosowanie w metodzie syntetycznej apertury nadawczej (STA) i opiera się na założeniu, że sygnał uzyskany za pomocą dowolnej pary przetworników jest taki sam niezależnie od tego, który z przetworników nadawał, a który odbierał. W tej sytuacji można pominąć blisko połowę zapisanych danych i wciąż
możliwe będzie zrekonstruowanie obrazu w poprzedniej jakości. Na podstawie prezentowanych wyników symulacji oraz pomiarów na fantomach nitkowym i tkankowym wykazano, że stosując opisaną technikę przerzedzania można zmniejszyć o połowę ilość danych przy zachowaniu rozdzielczości i nieznacznym spadku parametru SNR oraz kontrastu rekonstruowanych obrazów.

Keywords:

metody syntetycznej apertury, przerzedzanie danych

Affiliations:
Karwat P.-IPPT PAN
Klimonda Z.-IPPT PAN
Sęklewski M.-IPPT PAN
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
8.Sęklewski M., Karwat P., Klimonda Z., Lewandowski M., Nowicki A., Preliminary results: analysis of Synthetic Transmit Aperture technique in ultrasonic imaging, 57 Otwarte Seminarium z Akustyki, 2010-09-20/09-24, Gliwice (PL), pp.173-176, 2010
Abstract:

The Synthetic Aperture (SA) methods are widespread and successfully used in radar technology, as well as in the sonar systems. The advantages of relatively good resolution in the whole area of scanning without decrease of framerate, make this technique an object of interest in medical imaging methods such as ultrasonography (US).This paper describes the possible usage of the SA method in ultrasound imaging. The measurements of different SA schemes were conducted using the set-up consisting of the research ultrasonograph module, the PC and the special wire phantom. The results for different schemes of image reconstruction are presented. Particularly the Synthetic Transmit Aperture (STA) technique was concerned. Results of the STA method are discussed in this paper.

Keywords:

ultrasonic imaging, synthetic aperture focusing technique

Affiliations:
Sęklewski M.-IPPT PAN
Karwat P.-IPPT PAN
Klimonda Z.-IPPT PAN
Lewandowski M.-IPPT PAN
Nowicki A.-IPPT PAN
9.Walczak M., Kulesza P., Lewandowski M., Karwat P., Witek B., Implementacja w układzie FPGA wybranego filtru ech stałych dla wielobramkowego systemu Dopplera przezczaszkowego, 57 Otwarte Seminarium z Akustyki, 2010-09-20/09-24, Gliwice (PL), pp.209-212, 2010
Abstract:

W artykule opisano wybór i implementację filtrów ech stałych w programowalnych układach logicznych (FPGA) dla ultradźwiękowego wielobramkowego systemu przezczaszkowego przepływomierza krwi opracowywanego w Zakładzie Ultradźwięków IPPT PAN. Implementacja filtrów w FPGA miała na celu redukcję obciążenia softwarowego przetwarzania sygnałów dopplerowskich. W pracy przedstawiono badania modelowe i porównanie filtrów ech stałych o skończonej odpowiedzi impulsowej (SOI) oraz nieskończonej odpowiedzi impulsowej (NOI). Przeanalizowany został zakres stabilnej pracy filtru NOI. Wyselekcjonowany filtr górnoprzepustowy typu SOI został następnie zaimplementowany i zoptymalizowany do architektury układów FPGA oraz zastosowania w przepływomierzu. Zastosowano ekonomiczny układ FPGA Altera Cyclone III EP3C25F324C8. Opracowany filtr ech stałych realizuje 100 identycznych górnoprzepustowych filtrów typu SOI, co zapewnia filtrowanie sygnału dopplerowskiego w 100 bramkach jednocześnie. Filtry operują na 16 bitowych próbkach sygnału, a ich charakterystyka jest programowalna przez 65 16-bitowych współczynników. Zweryfikowano poprawność przetwarzania na komputerze PC w środowisku Altera Quartus II 9.1 oraz ModelSim 6.5b poprzez symulacje i porównanie odpowiedzi impulsowej oraz skokowej filtrów. W wyniku opisanych prac powstała struktura logiczna filtru ech stałych przeznaczona do implementacji w układzie FPGA Cyclone III, zajmująca 5% zasobów logicznych układu oraz 34% zasobów pamięciowych.

Keywords:

ultradźwiękowy Doppler przezczaszkowy, filtry ech stałych, cyfrowe przetwarzanie, FPGA

Affiliations:
Walczak M.-IPPT PAN
Kulesza P.-IPPT PAN
Lewandowski M.-IPPT PAN
Karwat P.-IPPT PAN
Witek B.-IPPT PAN
10.Lewandowski M., Klimonda Z., Karwat P., Sęklewski M., Nowicki A., Bassi L., Tortoli P., Comparison of different schemes of synthetic transmit aperture using an ultrasound advanced open platform (ULA-OP), IUS 2010, IEEE International Ultrasonics Symposium, 2010-10-11/10-14, San Diego (US), DOI: 10.1109/ULTSYM.2010.5935656, pp.1988-1991, 2010
Abstract:

Increasing efforts are currently dedicated to incorporate the Synthetic Transmit Aperture (STA) method in ultrasound imaging systems. The STA technique can provide a pixel-like focusing (dynamic focusing at both transmit and receive) without impairment of the frame rate. This goal can only be achieved by a careful design of the transmission and reception schemes. In this paper, the preliminary results of resolution, Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) measurements for a specific SA scheme with different transmit apertures are presented. The measurements were made using a novel ultrasound advanced open platform (ULA-OP) developed at the University of Florence. The ULA-OP is fully programmable and enables access to the RF echo-data from each transducer element.

Keywords:

synthetic aperture, ultrasound open platform

Affiliations:
Lewandowski M.-IPPT PAN
Klimonda Z.-IPPT PAN
Karwat P.-IPPT PAN
Sęklewski M.-IPPT PAN
Nowicki A.-IPPT PAN
Bassi L.-other affiliation
Tortoli P.-other affiliation

Conference abstracts
1.Karwat P., Computationally efficient method for reconstruction of sound speed in soft tissues, OSA 16, LXIII Otwarte Seminarium z Akustyki, 2016-09-13/09-16, Białowieża (PL), pp.619, 2016
2.Litniewski J., Klimonda Z., Karwat P., Piotrzkowska-Wróblewska H., Dobruch-Sobczak K., Tymkiewicz R., Gambin B., Cancer Malignancy Sonic Markers, OSA 16, LXIII Otwarte Seminarium z Akustyki, 2016-09-13/09-16, Białowieża (PL), DOI: 10.1515/aoa-2016-0059, No.3, pp.622, 2016
3.Gambin B., Kruglenko E., Secomski W., Karwat P., Temperature dependencies of ultrasound signals backscattered from an agar-oil soft-tissue mimicking material, PCM-CMM 2015, 3rd Polish Congress of Mechanics and 21st Computer Methods in Mechanics, 2015-09-08/09-11, Gdańsk (PL), pp.215-216, 2015
Abstract:

Tissue mimicking materials for ultrasound research, phantoms, should be acousticaly similar to the tissues. Such requirements are filled by the AGO (agar-oil) phantoms. Here, they have been used in experiment of heating internal region of samples by the high intensity ultrasound (HIFU) transducer. During heating the RF (radio frequency) ultrasound signals have been collected. It is demonstrated that the temperature changes in AGO phantoms can be described by the special properties of the backscattered RF signals, namely the shape parameter of the Nakagami distribution and SNR (signal to noise ratio) of signal envelopes random distribution. Reveal of qualitative relationships between the temperature increase/decrease measured by thermocouples and the statistical parameters changes are the main result of the paper.

Keywords:

soft tissue phantom, absorption of acoustic energy, temperature marker, signal-to-noise ratio, Nakagami distribution

Affiliations:
Gambin B.-IPPT PAN
Kruglenko E.-IPPT PAN
Secomski W.-IPPT PAN
Karwat P.-IPPT PAN
4.Lewandowski M., Walczak M., Karwat P., Witek B., Nowicki A., Karłowicz P., Research & Medical Doppler platform, 11th Congrès Français d'Acoustique, 2012 IOA annual meeting, 2012-04-23/04-27, Nantes (FR), pp.x1-x6, 2012
Abstract:

A new ultrasound digital transcranial Doppler system (digiTDS) is introduced. The digiTDS enables diagnosis of intracranial vessels which are difficult to penetrate for standard systems. The device can display a color map of flow velocities in time-depth domain and a spectrogram of a Doppler signal received from a particular depth. The system offers a multigate processing that allows to display simultaneously a number of spectrograms and to reconstruct a flow velocity profile. The digital signal processing in digiTDS is partitioned between hardware and software parts. The hardware part (based on FPGA) executes a signal demodulation and reduces data stream. The software part (PC) performs the Doppler processing and display tasks. The hardware-software partitioning allowed to build a flexible Doppler platform at a relatively low cost. The digiTDS design fulfills all necessary medical standards being a new useful tool in transcranial field as well as in heart velocimetry research.

Keywords:

ultrasound transcranial Doppler, RF signal processing, DSP, FPGA

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Karwat P.-IPPT PAN
Witek B.-IPPT PAN
Nowicki A.-IPPT PAN
Karłowicz P.-other affiliation