Norbert Żołek, Ph.D.

Department of Ultrasound (ZU)
Division of Ultrasonic Introscopy (PIU)
position: main specialist
telephone: (+48) 22 826 12 81 ext.: 335
room: 514
e-mail: nzolek

Recent publications
1.Żołek N., Ranachowski Z., Ranachowski P., Jóźwiak-Niedźwiedzka D., Kúdela Jr S., Dvorak T., Statistical assessment of the microstructure of barite aggregate from different deposits using x-ray microtomography and optical microscopy, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0104, Vol.62, No.2, pp.697-702, 2017
Abstract:

Two different barite ore (barium sulfate BaSO4) specimens from different localizations were tested and described in this paper. Analysis of the microstructure was performed on polished sections, and on thin sections using X-ray microtomography (micro-CT), and optical microscopy (MO). Microtomography allowed obtaining three-dimensional images of the barite aggregate specimens. In the tomograms, the spatial distribution of the other polluting phases, empty space as well as cracks, pores, and voids – that exceeded ten micrometers of diameter-were possible to visualize. Also, the micro-CT allowed distinguishing between minerals of different density, like SiO2 and BaSO4. Images obtained and analyzed on thin sections with various methods using the optical microscopy in transmitted light delivered additional information on the aggregate microstructure, i.e. allow for estimation of the different kinds of inclusions (like the different density of the minerals) in the investigated specimens. Above methods, which were used in the tests, completed each another in order to supply a set of information on inclusions’ distribution and to present the important differences of the barite aggregate specimens microstructure.

Keywords:

barite ore, barite aggregate, microstructure, optical microscopy, thin sections analysis, X-ray tomography

Affiliations:
Żołek N.-IPPT PAN
Ranachowski Z.-IPPT PAN
Ranachowski P.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Dvorak T.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
2.Wójcik J., Lewandowski M., Żołek N., Grating Lobes Suppression by Adding Virtual Receiving Subaperture in Synthetic Aperture Imaging, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2016.12.013, Vol.76, pp.125-135, 2017
Abstract:

A method of suppression of grating lobes is presented, analyzed, and verified. The method is based on creating a Virtual Receiving Subaperture (VRS) by adding virtual transducer elements not existing in the physical layout of the receiver. The VRS channels are filled with data based on signals from real channels. The analytical model of the synthetic aperture imaging system’s impulse response is presented to describe the properties of the VRS. The model shows a reduction of the receiving grating lobes’ amplitude (with a comparison to the main lobe’s amplitude) by a magnitude equal to the number of receiving transducer elements. It is shown that effective properties of the entire system with a VRS are similar to a system with a pitch in the receiving aperture that is twice as small. The numerical calculations of the impulse response show a doubling of the signal to noise ratio, which results in a reduction of the receiving grating lobes. For experimental validation, the generalized Plane Wave Imaging with and without the VRS is compared with a basic synthetic transmit aperture (STA) imaging. The experiment confirmed that the use of a VRS allows for visualizat ion of the objects in a medium in which they are not imaged without a VRS or are visualized with a lower contrast. The reduction of grating lobes attained using the proposed method is at the level of 15dB in the visualization of the superficial cyst.

Keywords:

Grating lobes, Image quality, Synthetic aperturę, Virtual subaperture

Affiliations:
Wójcik J.-IPPT PAN
Lewandowski M.-IPPT PAN
Żołek N.-IPPT PAN
3.Wabnitz H., Jelzow A., Mazurenka M., Steinkellner O., Macdonald R., Milej D., Żołek N., Kacprzak M., Sawosz P., Maniewski R., Liebert A., Magazov S., Hebden J., Martelli F., Di Ninni P., Zaccanti G., Torricelli A., Contini D., Re R., Zucchelli L., Spinelli L., Cubeddu R., Pifferi A., Performance assessment of timedomain optical brain imagers, part 2: nEUROPt protocol, JOURNAL OF BIOMEDICAL OPTICS, ISSN: 1083-3668, DOI: 10.1117/1.JBO.19.8.086012, Vol.19, No.8, pp.086012-1-12, 2014
Abstract:

The nEUROPt protocol is one of two new protocols developed within the European project nEUROPt to characterize the performances of time-domain systems for optical imaging of the brain. It was applied in joint measurement campaigns to compare the various instruments and to assess the impact of technical improvements. This protocol addresses the characteristic of optical brain imaging to detect, localize, and quantify absorption changes in the brain. It was implemented with two types of inhomogeneous liquid phantoms based on Intralipid and India ink with well-defined optical properties. First, small black inclusions were used to mimic localized changes of the absorption coefficient. The position of the inclusions was varied in depth and lateral direction to investigate contrast and spatial resolution. Second, two-layered liquid phantoms with variable absorption coefficients were employed to study the quantification of layer-wide changes and, in particular, to determine depth selectivity, i.e., the ratio of sensitivities for deep and superficial absorption changes. We introduce the tests of the nEUROPt protocol and present examples of results obtained with different instruments and methods of data analysis. This protocol could be a useful step toward performance tests for future standards in diffuse optical imaging.

Affiliations:
Wabnitz H.-Physikalisch-Technische Bundesanstalt (DE)
Jelzow A.-Physikalisch-Technische Bundesanstalt (DE)
Liebert A.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Magazov S.-University College London (GB)
Hebden J.-University College London (GB)
Martelli F.-University of Florence (IT)
Di Ninni P.-University of Florence (IT)
Zaccanti G.-University of Florence (IT)
Torricelli A.-Politecnico di Milano (IT)
Contini D.-Politecnico di Milano (IT)
Re R.-Politecnico di Milano (IT)
Zucchelli L.-Politecnico di Milano (IT)
Mazurenka M.-Physikalisch-Technische Bundesanstalt (DE)
Spinelli L.-Consiglio Nazionale delle Ricerche–Istituto di Fotonica e Nanotecnologie (IT)
Cubeddu R.-Politecnico di Milano (IT)
Pifferi A.-Consiglio Nazionale delle Ricerche–Istituto di Fotonica e Nanotecnologie (IT)
Steinkellner O.-Physikalisch-Technische Bundesanstalt (DE)
Macdonald R.-Physikalisch-Technische Bundesanstalt (DE)
Milej D.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Żołek N.-other affiliation
Kacprzak M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Sawosz P.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Maniewski R.-other affiliation
4.Spinelli L., Botwicz M., Żołek N., Kacprzak M., Milej D., Sawosz P., Liebert A., Weigel U., Durduran T., Foschum F., Kienle A., Baribeau F., Leclair S., Bouchard J.P., Noiseux I., Gallant P., Mermut O., Farina A., Pifferi A., Torricelli A., Cubeddu R., Ho H.C., Mazurenka M., Wabnitz H., Klauenberg K., Bodnar O., Elster C., Bénazech-Lavoué M.Y., Bérubé-Lauzière Y., Lesage F., Khoptyar D., Subash A.A., Andersson-Engels S., Di Ninni P., Martelli F., Zaaccanti G., Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink, BIOMEDICAL OPTICS EXPRESS, ISSN: 2156-7085, DOI: 10.1364/BOE.5.002037, Vol.5, No.7, pp.2037-2053, 2014
Abstract:

A multi-center study has been set up to accurately characterize the optical properties of diffusive liquid phantoms based on Intralipid and India ink at near-infrared (NIR) wavelengths. Nine research laboratories from six countries adopting different measurement techniques, instrumental set-ups, and data analysis methods determined at their best the optical properties and relative uncertainties of diffusive dilutions prepared with common samples of the two compounds. By exploiting a suitable statistical model, comprehensive reference values at three NIR wavelengths for the intrinsic absorption coefficient of India ink and the intrinsic reduced scattering coefficient of Intralipid-20% were determined with an uncertainty of about 2% or better, depending on the wavelength considered, and 1%, respectively. Even if in this study we focused on particular batches of India ink and Intralipid, the reference values determined here represent a solid and useful starting point for preparing diffusive liquid phantoms with accurately defined optical properties. Furthermore, due to the ready availability, low cost, long-term stability and batch-to-batch reproducibility of these compounds, they provide a unique fundamental tool for the calibration and performance assessment of diffuse optical spectroscopy instrumentation intended to be used in laboratory or clinical environment. Finally, the collaborative work presented here demonstrates that the accuracy level attained in this work for optical properties of diffusive phantoms is reliable.

Affiliations:
Spinelli L.-Consiglio Nazionale delle Ricerche–Istituto di Fotonica e Nanotecnologie (IT)
Botwicz M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Kienle A.-Universit at Ulm (DE)
Baribeau F.-National Optics Institute (CA)
Leclair S.-National Optics Institute (CA)
Bouchard J.P.-National Optics Institute (CA)
Noiseux I.-National Optics Institute (CA)
Gallant P.-National Optics Institute (CA)
Mermut O.-National Optics Institute (CA)
Farina A.-Consiglio Nazionale delle Ricerche–Istituto di Fotonica e Nanotecnologie (IT)
Pifferi A.-Consiglio Nazionale delle Ricerche–Istituto di Fotonica e Nanotecnologie (IT)
Torricelli A.-Politecnico di Milano (IT)
Żołek N.-other affiliation
Cubeddu R.-Politecnico di Milano (IT)
Ho H.C.-ITRI, Industrial Technology Research Institute (TW)
Mazurenka M.-Physikalisch-Technische Bundesanstalt (DE)
Wabnitz H.-Physikalisch-Technische Bundesanstalt (DE)
Klauenberg K.-Physikalisch-Technische Bundesanstalt (DE)
Bodnar O.-PTB, Physikalisch-Technische Bundesanstalt (DE)
Elster C.-Physikalisch-Technische Bundesanstalt (DE)
Bénazech-Lavoué M.Y.-Université de Sherbrooke (CA)
Bérubé-Lauzière Y.-Université de Sherbrooke (CA)
Lesage F.-École Polytechnique de Montreal (CA)
Kacprzak M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Khoptyar D.-Lund University (SE)
Subash A.A.-Lund University (SE)
Andersson-Engels S.-Lund University (SE)
Di Ninni P.-University of Florence (IT)
Martelli F.-University of Florence (IT)
Zaaccanti G.-University of Florence (IT)
Milej D.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Sawosz P.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Liebert A.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Weigel U.-ICFO, Institut de Ciències Fotòniques (ES)
Durduran T.-ICFO, Institut de Ciències Fotòniques (ES)
Foschum F.-Universit at Ulm (DE)
5.Gerega A., Milej D., Weigl W., Botwicz M., Żołek N., Kacprzak M., Wierzejski W., Toczyłowska B., Mayzner-Zawadzka E., Maniewski R., Lieberta A., Multiwavelength time-resolved detection of fluorescence during the inflow of indocyanine green into the adult’s brain, JOURNAL OF BIOMEDICAL OPTICS, ISSN: 1083-3668, DOI: 10.1117/1.JBO.17.8.087001, Vol.17, No.8, pp.087001-1-9, 2012
Abstract:

Optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for clinical assessment of brain perfusion in adults at the bedside. Methodology of multiwavelength and time-resolved detection of fluorescence light excited in the ICG is presented and advantages of measurements at multiple wavelengths are discussed. Measurements were carried out: 1. on a physical homogeneous phantom to study the concentration dependence of the fluorescence signal, 2. on the phantom to simulate the dynamic inflow of ICG at different depths, and 3. in vivo on surface of the human head. Pattern of inflow and washout of ICG in the head of healthy volunteers after intravenous injection of the dye was observed for the first time with time-resolved instrumentation at multiple emission wavelengths. The multiwavelength detection of fluorescence signal confirms that at longer emission wavelengths, probability of reabsorption of the fluorescence light by the dye itself is reduced. Considering different light penetration depths at different wavelengths, and the pronounced reabsorption at longer wavelengths, the time-resolved multiwavelength technique may be useful in signal decomposition, leading to evaluation of extra- and intracerebral components of the measured signals

Keywords:

indocyanine green bolus, near-infrared spectroscopy, fluorescence, time-resolved spectra, multiwavelength detection

Affiliations:
Gerega A.-other affiliation
Milej D.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Lieberta A.-other affiliation
Weigl W.-other affiliation
Botwicz M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Żołek N.-other affiliation
Kacprzak M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Wierzejski W.-other affiliation
Toczyłowska B.-other affiliation
Mayzner-Zawadzka E.-other affiliation
Maniewski R.-other affiliation
6.Sawosz P., Kacprzak M., Weigl W., Borowska-Solonynko A., Krajewski P., Żołek N., Ciszek B., Maniewski R., Liebert A., Experimental estimation of the photons visiting probability profiles in time-resolved diffuse reflectance measurement, PHYSICS IN MEDICINE AND BIOLOGY, ISSN: 0031-9155, DOI: 10.1088/0031-9155/57/23/7973, Vol.57, pp.7973-7981, 2012
Abstract:

A time-gated intensified CCD camera was applied for time-resolved imaging of light penetrating in an optically turbid medium. Spatial distributions of light penetration probability in the plane perpendicular to the axes of the source and the detector were determined at different source positions. Furthermore, visiting probability profiles of diffuse reflectance measurement were obtained by the convolution of the light penetration distributions recorded at different source positions. Experiments were carried out on homogeneous phantoms, more realistic two-layered tissue phantoms based on the human skull filled with Intralipid–ink solution and on cadavers. It was noted that the photons visiting probability profiles depend strongly on the source–detector separation, the delay between the laser pulse and the photons collection window and the complex tissue composition of the human head

Affiliations:
Sawosz P.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Kacprzak M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Weigl W.-other affiliation
Borowska-Solonynko A.-other affiliation
Krajewski P.-other affiliation
Żołek N.-other affiliation
Ciszek B.-other affiliation
Maniewski R.-other affiliation
Liebert A.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
7.Milej D., Gerega A., Żołek N., Weigl W., Kacprzak M, Sawosz P., Mączewska J., Fronczewska K., Mayzner-Zawadzka E., Królicki L., Maniewski R., Liebert A., Time-resolved detection of fluorescent light during inflow of ICG to the brain - a methodological study, PHYSICS IN MEDICINE AND BIOLOGY, ISSN: 0031-9155, DOI: 10.1088/0031-9155/57/20/6725, Vol.57, pp.6725-6742, 2012
Abstract:

It was reported that time-resolved reflectance measurements carried out during inflow and washout of an optical contrast agent may provide information on the blood supply to the brain cortex of human adults. It was also shown that a measurement of fluorescence excited in the dye circulating in the brain is feasible. Unfortunately, patterns of time-resolved fluorescence signals observed during in vivo measurements are difficult to interpret. The aim of this study was to analyze the influence of several factors on the fluorescence signals measured during in vivo experiments. A laboratory instrument for recording the distributions of arrival of fluorescence photons was constructed and optimized for measurements on humans. Monte Carlo simulations and laboratory measurements on liquid phantoms as well as in vivo measurements on healthy volunteers were carried out. An influence of source–detector separation, position of the source–detector pair on the head, as well as a dose of the injected indocyanine green (ICG) on the fluorescence signals were studied in detail. It was shown that even for a small dose of ICG (0.025 mg kg−1) the time-resolved signals can be successfully detected on the surface of the head. Strong influence of the studied factors on the fluorescence signals was observed. It was also noted that the changes in moments of distributions of arrival times of fluorescence photons depend on the anatomical structure of the tissues located between the source and the detector.

Affiliations:
Milej D.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Gerega A.-other affiliation
Maniewski R.-other affiliation
Liebert A.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Żołek N.-other affiliation
Weigl W.-other affiliation
Kacprzak M-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Sawosz P.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Mączewska J.-other affiliation
Fronczewska K.-other affiliation
Mayzner-Zawadzka E.-other affiliation
Królicki L.-other affiliation
8.Sawosz P., Żołek N., Kacprzak M., Maniewski R., Liebert A., Application of time-gated CCD camera with image intensifier in contactless detection of absorbing inclusions buried in optically turbid medium which mimics local changes in oxygenation of the brain tissue, OPTO-ELECTRONICS REVIEW, ISSN: 1230-3402, DOI: 10.2478/s11772-012-0041-y, Vol.20, No.4, pp.309-314, 2012
Abstract:

The near infrared spectroscopy may be implemented using various optoelectronic techniques, however, most of them do notallow to carry out measurements at short source−detector separation. We propose a method, based on time−gated intensifiedCCD camera, which allows for contactless measurements and can be carried out at short source−detector separation. This technique was tested on a phantom with absorbing inclusions buried in an optically turbid medium which mimics localchanges in oxygenation of the brain tissue

Keywords:

time−resolved NIRS, time−gated intensified CCD camera, short source−detector separation

Affiliations:
Sawosz P.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Żołek N.-other affiliation
Kacprzak M.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)
Maniewski R.-other affiliation
Liebert A.-Nałęcz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences (PL)

List of chapters in recent monographs
1.
501
Wójcik J., Żołek N., Lewandowski M., Advances in Acoustics 2016, rozdział: Influence of transmission-reception characteristics of ultrasound transducers on statistics of echoesfrom nonhomogeneous media, Polish Acoustical Society, Warsaw Division, Institute of Fundamental Technological Research PAS, pp.627-633, 2016

Conference papers
1.Żołek N., Wójcik J., Optimized Acoustic Echoes Simulator in Fourier domain, 2017 IEEE, 2017 IEEE International Ultrasonics Symposium, 2017-09-06/09-09, Washington, DC (US), DOI: 10.1109/ULTSYM.2017.8092654, pp.1-3, 2017
Abstract:

A new toolbox for the simulation of acoustic wave fields is described. The toolbox, USim, is designed to make an acoustic modeling of ultrasound propagation in tissues reliable and fast. The forward simulations of the wave field are based on the Born-Neumann single scattering approximation of the solution of Sturm-Liouville equation. The toolbox allows simulating the ultrasound wave propagation in non-homogeneous media containing finite size scatterers similar to those existing in a real tissues. The approach of calculations conducted in Fourier space increases the efficiency and allows taking into account the absorption and density phenomena in a simple and correct way.

Keywords:

acoustic propagation; numerical simulations; fourier domain

Affiliations:
Żołek N.-IPPT PAN
Wójcik J.-IPPT PAN
2.Walczak M., Lewandowski M., Żołek N., Optimization of real-time ultrasound PCIe data streaming and OpenCL processing for SAFT imaging, IUS 2013, IEEE International Ultrasonics Symposium, 2013-07-21/07-25, Praga (CZ), DOI: 10.1109/ULTSYM.2013.0527, Vol.1, pp.2064-2067, 2013
Abstract:

Our goal is to develop a complete ultrasound platform based on real-time SAFT (Synthetic Aperture Focusing Technique) GPU processing. We are planning to integrate all the ultrasound modules and processing resources (GPU) in a single rack enclosure with the PCIe switch fabric backplane. The first developed module (RX64) provides acquisition and streaming of 64 ultrasound channels. We implemented and benchmarked data streaming from the RX64 to the GPU memory and the SAFT image reconstruction on the GPU. A high system performance was achieved using hardware assisted direct memory transfers and pipelined processing workflow. The complete system throughput, including 128 channel data transfer at 16kS per line and low-resolution 256×256 pixel image SAFT reconstruction on a single Nvidia K5000 GPU, reached 450 fps. The obtained results proved the feasibility of the ultrasound real-time imaging system with GPU SAFT processing.

Keywords:

ultrasonic imaging, synthetic aperture, GPGPU, FPGA

Affiliations:
Walczak M.-IPPT PAN
Lewandowski M.-IPPT PAN
Żołek N.-IPPT PAN

Conference abstracts
1.Walczak M., Lewandowski M., Żołek N., A real-time streaming DAQ for Ultrasonix Research scanner, IUS 14, IEEE International Ultrasonics Symposium, 2014-09-03/09-06, Chicago (US), DOI: 10.1109/ULTSYM.2014.0310, pp.1257-1260, 2014
Abstract:

A new 128 channel parallel acquisition module for the Ultrasonix SonixTouch ultrasound scanner was developed. Although the module provides similar functionality to the original SonixDAQ system, it presents new possibilities of real-time data streaming and processing on GPU, thanks to a fast PCIe communication interface. Direct access and processing of pre-beamformed channel data with fully programmable transmit schemes enables the research implementation of new advanced imaging modalities (eg. plane wave imaging, vector Doppler, shear wave elastography). The presented RX-DAQ system is enriched with a GPU software framework, for Python and Matlab, enabling the integration of user processing functions.

Keywords:

ultrasonic imaging, pre-beamformed data, real-time processing, GPU, FPGA

Affiliations:
Walczak M.-IPPT PAN
Lewandowski M.-IPPT PAN
Żołek N.-IPPT PAN