Ziemowit Klimonda, Ph.D. 

Doctoral thesis
20130524  Obrazowanie parametryczne tłumienia fali ultradźwiękowej w tkance miękkiej
 659 
Recent publications
1.  Klimonda Z., Postema M., Nowicki A., Litniewski J., Tissue Attenuation Estimation by Mean Frequency Downshift and Bandwidth Limitation, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, ISSN: 08853010, DOI: 10.1109/TUFFC.2016.2574399, Vol.63, No.8, pp.11071115, 2016 Abstract: Attenuation of ultrasound in tissue can be estimated from the propagating pulse center frequency downshift. This method assumes that the envelope of the emitted pulse can be approximated by a Gaussian function and that the attenuation linearly depends on frequency. The resulting downshift of the mean frequency depends not only on attenuation but also on pulse bandwidth and propagation distance. This kind of approach is valid for narrowband pulses and shallow penetration depth. However, for short pulses and deep penetration, the frequency downshift is rather large and the received spectra are modified by the limited bandwidth of the receiving system. In this paper, the modified formula modeling the mean frequency of backscattered echoes is presented. The equation takes into account the limitation of the bandwidth due to bandpass filtration of the received echoes. This approach was applied to simulate the variation of the mean frequency of the pulse propagating for both weakly and strongly attenuating media and for narrowband and wideband pulses. The behavior of both the standard and modified estimates of attenuation has been validated using RF data from a tissuemimicking phantom. The ultrasound attenuation of the phantom, determined with a corrected equation, was close to its true value, while the result obtained using the original formula was lower by as much as 50% at a depth of 8 cm. Keywords:Tissue attenuation, frequency downshift, bandwidth limitation Affiliations:
 
2.  Klimonda Z., Litniewski J., Karwat P., Nowicki A., Spatial and Frequency Compounding in Application to Attenuation Estimation in Tissue, ARCHIVES OF ACOUSTICS, ISSN: 01375075, DOI: 10.2478/aoa20140056, Vol.39, No.4, pp.519527, 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 rootmeansquare 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:
 
3.  Tasinkevych Y., Klimonda Z., Lewandowski M., Nowicki A., Lewin P.A.^{♦}, Modified multielement synthetic transmit aperture method for ultrasound imaging: A tissue phantom study, Ultrasonics, ISSN: 0041624X, DOI: 10.1016/j.ultras.2012.10.001, Vol.53, pp.570579, 2013 Abstract: The paper presents the modified multielement synthetic transmit aperture (MSTA) method for ultrasound imaging. It is based on coherent summation of RF echo signals with apodization weights taking into account the finite size of the transmit subaperture and of the receive element. The work presents extension of the previous study where the modified synthetic transmit aperture (STA) method was considered and verified [1]. In the case of MSTA algorithm the apodization weights were calculated for each imaging point and all combinations of the transmit subaperture and receive element using their angular directivity functions (ADFs). The ADFs were obtained from the exact solution of the corresponding mixed boundaryvalue problem for periodic baffle system modeling the transducer array. Performance of the developed method was tested using Field II simulated synthetic aperture data of point reflectors for 4 MHz 128element transducer array with 0.3 mm pitch and 0.02 mm kerf to estimate the visualization depth and lateral resolution. Also experimentally determined data of the tissuemimicking phantom (Dansk Fantom Service, model 571) obtained using 128 elements, 4 MHz, linear transducer array (model L145/38) and Ultrasonix SonixTOUCH Research platform were used for qualitative assessment of imaging contrast improvement. Comparison of the results obtained by the modified and conventional MSTA algorithms indicated 15 dB improvement of the noise reduction in the vicinity of transducer’s surface (1 mm depth), and concurrent increase in the visualization depth (86% augment of the scattered amplitude at the depth of 90 mm). However, this increase was achieved at the expense of minor degradation of the lateral resolution of approximately 8% at the depth of 50 mm and 5% at the depth of 90 mm. Keywords:Synthetic aperture imaging, Ultrasound imaging, Directivity function, Beamforming Affiliations:
 
4.  Litniewski J., Klimonda Z., Nowicki A., Parametric Sonographic Imaging – Application of Synthetic Aperture Technique to Imaging Attenuation of Ultrasound in Tissue Structures, HYDROACOUSTICS, ISSN: 16421817, Vol.15, pp.99110, 2012 Abstract: Ultrasonic imaging is a wellestablished 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. Keywords:soft tissue parametric imaging, attenuation imaging, synthetic aperture focusing technique Affiliations:
 
5.  Klimonda Z., Litniewski J., Nowicki A., Synthetic Aperture Technique Applied to Tissue Attenuation Imaging, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.36, No.4, pp.927935, 2011 Abstract: The attenuating properties of biological tissue are of great importance in ultrasonic medical imaging. Investigations performed in vitro and in vivo showed the correlation between pathological changes in the tissue and variation of the attenuation coefficient. In order to estimate the attenuation we have used the downshift of mean frequency (fm) of the interrogating ultrasonic pulse propagating in the medium. To determine the fm along the propagation path we have applied the fm estimator (I/Q algorithm adopted from the Doppler mean frequency estimation technique). The meanfrequency shift trend was calculated using Single Spectrum Analysis. Next, the trends were converted into attenuation coefficient distributions and finally the parametric images were computed. The RF data were collected in simulations and experiments applying the synthetic aperture (SA) transmitreceiving scheme. In measurements the ultrasonic scanner enabling a full control of the transmission and reception was used. The resolution and accuracy of the method was verified using tissue mimicking phantom with uniform echogenicity but varying attenuation coefficient. Keywords:tissue attenuation imaging, synthetic aperture, diagnosis enhancing Affiliations:
 
6.  Lewandowski M., Klimonda Z., Obrazowanie ultradźwiękowe wad za pomocą metod syntetycznej apertury, PRZEGLĄD SPAWALNICTWA, ISSN: 00332364, Vol.13, pp.2932, 2011 Abstract: Ultradźwiękowe metody badań nieniszczących przechodzą obecnie metamorfozę od systemów z głowicami jednoelementowymi do systemów wielokanałowych z głowicami fazowymi (PA Phased Array). Prowadzony obecnie w Zakładzie Ultradźwięków IPPT PAN projekt ma na celu opracowanie uniwersalnej wielokanałowej platformy ultradźwiękowej oraz metod rekonstrukcji obrazów mogących znaleźć zastosowanie zarówno w medycynie, jak i w badaniach nieniszczących. Przeprowadzono wstępne badania mające na celu porównanie różnych metod rekonstrukcji obrazów wad w trybie Bmode. W tym celu dokonano akwizycji ech ultradźwiękowych od wad w szynie kolejowej przy pomocy ultrasonografu badawczego wyposażonego w 128elementową głowicą fazową o częstotliwości 4 MHz. Uzyskane sygnały ech wysokiej częstotliwości poddano następnie obróbce cyfrowej w celu uzyskania obrazu Bmode. Zastosowano i porównano różne metody rekonstrukcji obrazu: klasyczny beamforming oraz metodę syntetycznej apertury. Wstępne wyniki wskazują na wysoką jakość rekonstrukcji metodą syntetycznej apertury, która zapewnia równomierną rozdzielczość poprzeczną w całej głębokości obrazowania. Zastosowanie alternatywnych schematów nadawczoodbiorczych w metodzie syntetycznej apertury umożliwia dodatkowo optymalizację metody pod względem prędkości badania lub jakości obrazowania. Wyniki te potwierdzają przydatność i konkurencyjność metody syntetycznej apertury do stosowanej obecnie metody beamformingu. Keywords:ultradźwiękowe badania nieniszczące, głowice PhasedArray, metody syntetycznej apertury Affiliations:
 
7.  Litniewski J., Klimonda Z., Nowicki A., The Synthetic Aperture technique for tissue attenuation imaging, Annual Report  Polish Academy of Sciences, ISSN: 16403754, pp.6567, 2011 Abstract: The mean frequency correlation estimator and SSA technique were implemented for processing of the RF ultrasonic echoes. The estimated attenuation values were equal to 0.7 and 0.9 dB/(MHz∙cm) and agreed well with the real values. We have found the RF data obtained using synthetic aperture technique (SA) to be much more reliable in terms of attenuation extraction then echoes recorded using the standard delay and sum (DAS) beamforming. The imaging of attenuation in tissue seems to be a promising technique in medical diagnostics, although the precision of a single scan is often unsatisfactory. Keywords:tissue attenuation imaging, sythetic aperture focusing technique Affiliations:
 
8.  Karwat P., Klimonda Z., Seklewski M.^{♦}, Lewandowski M., Nowicki A., Data reduction method for synthetic transmit aperture algorithm, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.35, No.4, pp.635642, 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 framerate than in case of conventional beamforming 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:
 
9.  Klimonda Z., Litniewski J., Nowicki A., Tissue attenuation estimation from backscattered ultrasound using spatial compounding technique – preliminary results, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.35, No.4, pp.643652, 2010 Abstract: 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 develop ing 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 atten uation 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. Keywords:ultrasound attenuation estimation, spatial compounding, parametric imaging Affiliations:
 
10.  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: 16421817, Vol.13, pp.243252, 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 setup 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:
 
11.  Klimonda Z., Litniewski J., Nowicki A., Preliminary results of attenuation estimation from tissue backscatter using commercial ultrasonic scanner, HYDROACOUSTICS, ISSN: 16421817, Vol.13, pp.127134, 2010 Abstract: 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. Keywords:tissue attenuation imaging, ultrasound attenuation estimation Affiliations:
 
12.  Klimonda Z., Litniewski J., Nowicki A., Spatial resolution of attenuation imaging, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.34, No.4, pp.461470, 2009 Abstract: The attenuating properties of biological tissue are of great importance in ultrasonic examination even though its anatomical variability limits diagnostics effectiveness. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The diagnostic usefulness of the proposed technique crucially depends on the precision of the attenuation estimate and the resolution of the parametric image. These two parameters are highly correlated, since the resolution is reduced whenever averaging is used to minimize the errors introduced by the random character of the backscatter. Here we report on the results of numerical processing of both, simulated and recorded from a tissuemimicking phantom echoes. We have analyzed the parameters of the estimation technique and examined their influence on the precision of the attenuation estimate and on the parametric image resolution. The optimal selection of attenuation image parameters depending on its intended diagnostic use, was also considered. Keywords:ultrasound attenuation, spatial resolution, parametric imaging Affiliations:
 
13.  Secomski W., Klimonda Z., Estimation and measurements of resonance scattering in the gas filled polymer microcapsules, HYDROACOUSTICS, ISSN: 16421817, Vol.12, pp.201208, 2009 Abstract: The gas filled polymer spheres are used either as an ultrasonic contrast agents or controlled drug delivery microcapsules. The power spectrum of the ultrasonic backscattered signal was calculated from the resonance scattering theory for the gas bubbles surrounded by elastic shield. The size distribution of the measured microspheres was included in the calculations. In experiment, the backscattered power spectrum of measured sample was recorded by Siemens Antares ultrasonic scanner. Radio frequency (RF) data was recorded for 2.5 – 6.7 MHz transmitted ultrasonic frequencies. The backscattered spectra were calculated by Matlab software and subtracted from the transmitter spectrum, recorded as an echo from the perfect reflector. The particle size in measured sample was 12 μm mean ± 8 μm sd. The resonance frequency, measured under the microscope, was 0.60 MHz for 45 μm diameter microsphere which corresponds to 2.25 MHz for 12 μm sphere. The sample volume was 10cm³ and the mean quantity of scatterers was 6·103/cm³. In conclusion, measured spectra matched those calculated from theory. The use of ultrasonic scanner with RF data output and the high sensitivity, wide bandwidth ultrasonic transducer allows to measure backscattered signal from the very small quantity of resonance scatterers with satisfactory results at 40 dB signal to noise ratio. Keywords:ultrasound, ultrasonic contrast agents, microcapsules, resonance frequency Affiliations:
 
14.  Litniewski J., Nowicki A., Klimonda Z., Lewandowski M., Sound fields for coded excitations in water and tissue, ULTRASOUND IN MEDICINE AND BIOLOGY, ISSN: 03015629, Vol.33, No.4, pp.601607, 2007 Abstract: Coded ultrasonography is intensively studied in many laboratories due to its remarkable properties, particularly increased penetration depth and signaltonoise ratio (SNR). However, no data on the spatial behavior of the pressure field generated by coded bursts transmissions in the tissue were yet reported. This paper reports the results of investigations of the field structure in water, in degassed beef liver and in pork tissue using four different excitations signals, two and 16 periods sine bursts and sinusoidal sequences with phase modulation using 13bits Barker code and 16bits Golay complementary codes. The results of measured pressure field distributions before and after compression were compared with those recorded using short pulse excitation. Keywords:Coded excitation, Ultrasound field distribution, Matching filtering Affiliations:
 
15.  Klimonda Z., Nowicki A., Imaging of the mean frequency of the ultrasonic echoes, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.32, No.4, pp.7780, 2007 Abstract: A standard USG image is in fact a visualization of a distribution of the reflexion coefficients. There is an increasing interest in imaging of the different parameters, which might characterize another physical properties of a tissue. The attenuation coefficient is one of such parameters and theoretically it can be estimated using frequency shift of the RF signal. The frequency shift results from dispersive character of the attenuation in tissue and is a function of attenuation along the propagate path. In this work authors use echo’s mean frequency as an imaging modality. The results of measurement of tissue phantom using 10 MHz linear array are presented. The preliminary results are encouraging being the first attempt towards mapping of the attenuation in tissue. Keywords:parametric visualization, mean frequency, attenuation estimation Affiliations:
 
16.  Nowicki A., Klimonda Z., Lewandowski M., Litniewski J., Lewin P.A.^{♦}, Trots I., Comparison of sound fields generated by different coded excitations experimental results, Ultrasonics, ISSN: 0041624X, Vol.44, pp.121129, 2006 Abstract: This work reports the results of measurements of spatial distributions of ultrasound fields obtained from five energizing schemes. Three different codes, namely, chirp signal and two sinusoidal sequences were investigated. The sequences were phase modulated with 13 bits Barker code and 16 bits Golay complementary codes. Moreover, two reference signals generated as two and sixteen cycle sine tone bursts were examined. Planar, 50% (fractional) bandwidth, 15 mm diameter source transducer operating at 2 MHz center frequency was used in all measurements. The experimental data were collected using computerized scanning system and recorded using wideband, PVDF membrane hydrophone (Sonora 804). The measured echoes were compressed, so the complete pressure field in the investigated location before and after compression could be compared. In addition to a priori anticipated increase in the signal to noise ratio (SNR) for the decoded pressure fields, the results indicated differences in the pressure amplitude levels, directivity patterns, and the axial distance at which the maximum pressure amplitude was recorded. It was found that the directivity patterns of noncompressed fields exhibited shapes similar to the patterns characteristic for sinusoidal excitation having relatively long time duration. In contrast, the patterns corresponding to compressed fields resembled those produced by brief, wideband pulses. This was particularly visible in the case of binary sequences. The location of the maximum pressure amplitude measured in the 2 MHz field shifted towards the source by 15 mm and 25 mm for Barker code and Golay code, respectively. The results of this work may be applicable in the development of new coded excitation schemes. They could also be helpful in optimizing the design of imaging transducers employed in ultrasound systems designed for coded excitation. Finally, they could shed additional light on the relationship between the spatial field distribution and achievable image quality and in this way facilitate optimization of the images obtained using coded systems. Keywords:coded excitation, sound fields Affiliations:
 
17.  Klimonda Z., Lewandowski M., Nowicki A., Trots I., Lewin P.A.^{♦}, Direct and postcompressed sound fields for different coded excitations  experimental results, ARCHIVES OF ACOUSTICS, ISSN: 01375075, Vol.30, No.4, pp.507514, 2005 Abstract: Coded ultrasonography is intensively studied in many laboratories due to its remarkable properties: increased depth penetration, signaltonoise ratio (SNR) gain and improved axial resolution. However, no data concerning the spatial behavior of the pressure field generated by coded bursts transmissions were reported so far. Five different excitation schemes were investigated. Flat, circular transducer with 15 mm diameter, 2 MHz center frequency and 50% bandwidth was used. The experimental data was recorded using the PVDF membrane hydrophone and collected with computerized scanning system developed in our laboratory. The results of measured pressure fields before and after compression were then compared to those recorded using standard ultrasonographic shortpulse excitation. The increase in the SNR of the decoded pressure fields is observed. The modification of the spatial pressure field distribution, especially in the intensity and shape of the sidelobes is apparent. Coded sequences are relatively long and, intuitively, the beam shape could be expected to be very similar to the sound field of longperiod sine burst. This is true for noncompressed distributions of examined signals. However, as will be shown, the compressed sound fields, especially for the measured binary sequences, are similar rather to field distributions of short, wideband bursts. Keywords:coded excitation, ultrasonic field distribution, pulse compression, matched filtration, medical imaging Affiliations:

List of chapters in recent monographs
1. 494  Klimonda Z., DobruchSobczak K., PiotrzkowskaWróblewska H., Tymkiewicz R., Litniewski J., Postępy Akustyki 2016, rozdział: Obrazowanie tłumienia ultradźwięków w tkance nowotworowej, Polskie Towarzystwo Akustyczne, Oddział Warszawski, Warszawa, Poland, pp.3948, 2016 
2. 495  Litniewski J., Klimonda Z., Karwat P., PiotrzkowskaWróblewska H., DobruchSobczak K., Tymkiewicz R., Gambin B., Postępy Akustyki 2016, rozdział: Cancer malignancy sonic markers, Polskie Towarzystwo Akustyczne, Oddział Warszawski, Warszawa, Poland, pp.4960, 2016 
3. 261  Klimonda Z., Litniewski J., Nowicki A., Acoustical Imaging, rozdział: Enhancing tissue attenuation estimation from backscattered ultrasound using spatial compounding and synthetic aperture techniques, Springer, Nowicki A., Litniewski J., Kujawska T. (Eds.), 31, pp.181190, 2012 
4. 306  Tasinkevych Y., Klimonda Z., Lewandowski M., Nowicki A., Acoustical Imaging, rozdział: Sound Field Directivity Correction in Synthetic Aperture Algorithm for Medical Ultrasound, Springer, Nowicki A., Litniewski J., Kujawska T. (Eds.), 31, pp.169179, 2012 
5. 311  Litniewski J., Klimonda Z., Nowicki A., Acoustical Imaging, rozdział: Applying Echoes Mean Frequency Shift for Attenuation Imaging in Tissue, Springer, 30, pp.97103, 2011 
6. 126  Nowicki A., Klimonda Z., Lewandowski M., Litniewski J., Lewin P.A.^{♦}, Trots I., Acoustical imaging, rozdział: Direct and postcompressed sound fields for different coded excitations, Springer, André M.P. et al (Eds.), 28, pp.399407, 2007 
Conference papers
1.  Steifer T., Klimonda Z., Lewandowski M., Multiply and Sum Spatial Compounding in Plane Wave Imaging, IUS 2016, IEEE International Ultrasonics Symposium, 20160918/0921, Tours (FR), DOI: 10.1109/ULTSYM.2016.7728887, pp.13, 2016 Abstract: This paper is a part of the IUS 2016 Planewave Imaging Challenge submission. Spatial compounding of several lowresolution images taken from different angles is a wellestablished practice in ultrasound imaging. The usual procedure relies on averaging several images using arithmetic mean. An alternative approach is presented, which relies on multiplication of the lowresolution images. Keywords:ultrasound, plane wave imaging Affiliations:
 
2.  Klimonda Z., Litniewski J., Nowicki A., Compounded plane wave technique applied to imaging attenuation of ultrasound in tissue structures, FA2014, 7th FORUM ACUSTICUM 2014, 20140907/0912, Kraków (PL), No.SS27_1, pp.15, 2014 Abstract: The parametric imaging can enhance ultrasonic examinations that are widely used in medical diagnostics. Attenuation of the wave propagating through the soft tissue reflects the state of the tissue, what is clearly demonstrated in literature. The visualization of the spatial distribution of attenuation may support the diagnosis by accurate discrimination of the lesions from normal tissue at the early stage of the disease. This research is focused on the developing of the method of attenuation estimation from ultrasonic backscatter. It would allow to produce the parametric images from the same data as the standard Bmode images. The attenuation estimation method bases on the spectral mean frequency (fm) downshift of the propagating pulse, that results from the frequency dependence of attenuation. The fm was determined (using fm correlation estimator and trend extraction with Single Spectrum Analysis algorithm) from the ultrasonic echoes scattered in the tissue mimicking phantom which contained a cylinder with the attenuation coefficient higher than in the background. The data acquisition were performed using ultrasonic scanner. The earlier research indicated the effectiveness of attenuation estimation method using the synthetic aperture technique to collect the data. The use of the synthetic transmit aperture scheme to acquire the data results in better attenuation imaging comparing to standard beamforming, however it lower the penetration depth. In this research the compounded plane wave transmitreceiving scheme was used, to improve the penetration range. Compensation for the diffraction effects was included in the data processing. The results indicate suitability of this approach for attenuation imaging. We can measure attenuation in the tissue mimicking materials with the spatial resolution of approximately 10mm and accuracy of 0.2dB/(MHz·cm). In the presentation, the attenuation images of tissue mimicking phantoms and the images of human liver, obtained in vivo, will be presented. Keywords:attenuation imaging, plane wave imaging Affiliations:
 
3.  Tasinkevych Y., Klimonda Z., Lewandowski M., Trots I., Nowicki A., Sound field directivity in multielement synthetic transmit aperture method for ultrasound imaging, Conference on Medical Imaging  Physics of Medical Imaging, 20120205/0208, San Diego (US), DOI: 10.1117/12.910584, Vol.8313, pp.8313691, 2012 Abstract: A modified multielement synthetic transmit aperture (MSTA) method for ultrasound imaging with RF echoes correction taking into account the influence of the element directivity is presented. The property is significant as the element width becomes commensurable with the wavelength of the emitted signal. The angular dependence of the radiation efficiency of the transmit/receive aperture is obtained from exact solution of the corresponding mixed boundaryvalue problem for periodic baffle system, modeling the transducer array. It is evaluated at the nominal frequency of the excitation signal and is implemented in the developed MSTA algorithm as apodization weights calculated for each imaging point and all combinations of the transmit/receive apertures. The performance of developed method is tested using FIELDII simulated synthetic aperture data of the point reflectors to estimate the visualization depth and lateral resolution. Besides, a FIELDII simulated and measurement data of cyst phantom are used for qualitative assessment of the imaging contrast. Comparison of the results obtained by the modified and conventional MSTA algorithms is given which reveals considerable improvement of the image quality in the area neighboring to the transducer’s aperture, and increase of the visualization depth at the cost of slight degradation of lateral resolution near the transducer face. Keywords:synthetic aperture, ultrasound imaging, beamforming Affiliations:
 
4.  Klimonda Z., Litniewski J., Nowicki A., Correcting for bounded bandwidth when estimating tissue attenuation from mean frequency downshift, IUS 2012, IEEE International Ultrasonics Symposium, 20121007/1010, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0413, pp.16471650, 2012 Abstract: The attenuation of tissue can be estimated utilizing the downshift of the center frequency of a propagating pulse. In general it is assumed that the shape of the emitted pulse can be approximated by a Gaussian function and attenuation is assumed to change linearly with frequency. At this conditions the downshift of the mean frequency of pulse spectrum depends linearly on attenuation coefficient, pulse bandwidth and propagation distance. This is a good approximation for relatively narrowband pulses and small penetration depth. But for short pulses and deep penetration the frequency downshift is large and the ultrasonic pulse is no more Gaussian, thus the previous assumption is no longer correct. The closer is the mean frequency of the pulse to the lower frequency bound of the receiving system the bigger deformation of the pulse spectrum occurs and consequently the attenuation is determined with bigger error. The following paper presents how to correct the experimentally determined mean frequency and to obtain reliable results when investigating tissue attenuation with wideband pulses. We propose a new formula for the dependence between pulse mean frequency, tissue attenuation, pulse bandwidth and traveled distance. The formula was derived from the mean frequency of Gaussian pulse spectrum determined in the limited frequency band. The formula was applied to simulate variation of mean frequency MF of the pulse propagating in the medium with attenuation coefficient corresponding to the attenuation in the tissue mimicking phantom. The MF was also determined (using the correlation estimator of MF and next trend extraction using Single Spectrum Analysis) from the simulated ultrasonic echoes and echoes scattered in the tissue phantom. The corrected nonlinear formula describes well MF variation along the pulse propagation path. The departure from the linear dependence increases with large MF shift, thus it is well pronounced for highly attenuating tissue, the wideband pulses and deep penetration. Keywords:attenuation estimation, frequency downshift Affiliations:
 
5.  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, 20121007/1010, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0590, pp.23612363, 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 echoessets 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:
 
6.  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, 20121007/1010, Dresden (DE), DOI: 10.1109/ULTSYM.2012.0320, pp.12831286, 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 multielement 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 contrasttonoise ratio (CNR) was equal 18, 19, and 19 dB for BFR, STA and PWI respectively. Keywords:Ultrasonic imaging, SAFT, Plane Wave Imaging Affiliations:
 
7.  Klimonda Z., Litniewski J., Nowicki A., Zastosowanie uśredniania częstotliwościowego i przestrzennego przy estymacji tłumienia w tkance miękkiej, 59th Open Seminar on Acoustics, 20120910/0914, Boszkowo (PL), Vol.1, pp.14, 2012 Abstract: Standardowe obrazy ultrasonograficzne przestawiają rozkład zmian impedancji akustycznej wewnątrz tkanki. Możliwe jest jednak obrazowanie innych parametrów akustycznych. Takie parametryczne obrazy dostarczałyby dodatkowych informacji o stanie tkanki, przydatnych w diagnostyce. Zmiany wartości współczynnika tłumienia fali ultradźwiękowej często towarzyszą patologicznym zmianom struktury tkanki, np. nowotworom. Jedną z metod estymacji tłumienia jest metoda bazująca na przesunięciu częstotliwości średniej widma sygnału w czasie jego propagacji w tkance. Główną niedogodnością metody jest duża wariancja otrzymywanych estymat. W niniejszej pracy przedstawiono rezultaty zastosowania metod uśredniania przestrzennego i częstotliwościowego w celu polepszenia jakości otrzymywanych obrazów rozkładu tłumienia. Weryfikacje metod przeprowadzono w oparciu o dane symulacyjne i dane z fantomu tkankowego o stałej echogeniczności i zmiennym tłumieniu. Keywords:estymacja tłumienia, uśrednianie przestrzenne, uśrednianie częstotliwościowe Affiliations:
 
8.  Klimonda Z., Litniewski J., Nowicki A., Tissue attenuation estimation from backscattered ultrasound using spatial compounding technique  preliminary results, 57 Otwarte Seminarium z Akustyki, 20100920/0924, Gliwice (PL), pp.9598, 2010 Abstract: The pathological states of biological tissues are often connected with 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 hanges 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 mean frequency trends extraction. 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 with uniform echogenicity but varying attenuation coefficient (DFS, Denmark). Keywords:tissue attenuation estimation, spatial compounding Affiliations:
 
9.  Karwat P., Klimonda Z., Sęklewski M., Lewandowski M., Nowicki A., Metoda przerzedzania danych dla algorytmu syntetycznej apertury nadawczej, 57 Otwarte Seminarium z Akustyki, 20100920/0924, Gliwice (PL), pp.9194, 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. metody syntetycznej apertury, przerzedzanie danych Affiliations:
 
10.  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, 20100920/0924, Gliwice (PL), pp.173176, 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 setup 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:
 
11.  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 (ULAOP), IUS 2010, IEEE International Ultrasonics Symposium, 20101011/1014, San Diego (US), DOI: 10.1109/ULTSYM.2010.5935656, pp.19881991, 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 pixellike 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 (ULAOP) developed at the University of Florence. The ULAOP is fully programmable and enables access to the RF echodata from each transducer element. Keywords:synthetic aperture, ultrasound open platform Affiliations:
 
12.  Litniewski J., Klimonda Z., Lewandowski M., Nowicki A., Szymańska E.^{♦}, Correcting for focusing when estimating tissue attenuation from mean frequency shift, IUS 2009, IEEE International Ultrasonics Symposium, 20090920/0923, Rzym (IT), DOI: 10.1109/ULTSYM.2009.5441930, pp.23832385, 2009 Abstract: Determination of attenuating properties of the tissue from the echoes of waves emitted by the focused transducer requires to compensate the echo signal for the effects of focusing. We propose the diffraction/focusing effects correcting (FC) technique that compensates focusinginduced mean frequency attenuation estimation, difraction correction, parametric imaging Affiliations:

Conference abstracts
1.  Klimonda Z., DobruchSobczak K., PiotrzkowskaWróblewska H., Tymkiewicz R., Litniewski J., Ultrasound attenuation imaging of tumor tissue, OSA 16, LXIII Otwarte Seminarium z Akustyki, 20160913/0916, Białowieża (PL), DOI: 10.1515/aoa20160059, pp.619620, 2016 Keywords: attenuation estimation, parametric imaging Affiliations:
 
2.  Litniewski J., Klimonda Z., Karwat P., PiotrzkowskaWróblewska H., DobruchSobczak K., Tymkiewicz R., Gambin B., Cancer Malignancy Sonic Markers, OSA 16, LXIII Otwarte Seminarium z Akustyki, 20160913/0916, Białowieża (PL), DOI: 10.1515/aoa20160059, No.3, pp.622, 2016 