Tomasz Steifer, M.Sc.

Department of Experimental Mechanics (ZMD)
Division of Non-Destructive Testing (PBN)
Laboratory of Professional Electronics
position: IT specialist
telephone: (+48) 22 826 12 81 ext.: 462
room: 538
e-mail: tsteifer

Recent publications
1.Steifer T., Lewandowski M., Ultrasound tissue characterization based on the Lempel–Ziv complexity with application to breast lesion classification, Biomedical Signal Processing and Control, ISSN: 1746-8094, DOI: 10.1016/j.bspc.2019.02.020, Vol.51, pp.235-242, 2019
Abstract:

Building upon the recent successes in the application of information-theoretic concepts (e.g. Shannon entropy) in quantitative ultrasound, the authors propose a novel tissue characterization method based on the Lempel–Ziv complexity. In this procedure, standard ultrasound B-Mode images are mapped onto words over finite alphabets before the corresponding Lempel–Ziv complexity of ultrasound images is calculated. Such complexity metric may be used to differentiate between types of tissues. Here, the method is utilized as a binary classifier for the malignancy of breast lesions. The method is tested on OASBUD – an open-access breast lesions image database. Images of 48 malignant and 48 benign lesions were used – two images for each lesion. The new procedure slightly outperforms the state-of-art classifier based on pixel entropy as measured in the size of area under the receiver operating curve (ROC AUC), which suggests that it may serve as a basis for computer-assisted breast cancer ultrasound diagnosis and possibly in other standard applications of the quantitative ultrasound.

Keywords:

A method based on Lempel–Ziv complexity is proposed for quantitative ultrasound tissue characterization, The method is used to classify breast lesions from an open access ultrasound image database, The method performance is compared with entropy-based classifier as entropy is related theoretically to Lempel–Ziv complexity, The new method achieves 0.87 ROC AUC as compared to 0.84 achieved by the reference method

Affiliations:
Steifer T.-IPPT PAN
Lewandowski M.-IPPT PAN
2.Kalociński D., Steifer T., On unstable and unoptimal prediction, MATHEMATICAL LOGIC QUARTERLY, ISSN: 1521-3870, DOI: 10.1002/malq.201800085, pp.1-10, 2019
Abstract:

We consider the notion of prediction functions (or predictors) studied before in the context of randomness and stochasticity by Ko, and later by Ambos‐Spies and others. Predictor is a total computable function which tries to predict bits of some infinite binary sequence. The prediction error is defined as the limit of the number of incorrect answers divided by the number of answers given so far. We discuss indefiniteness of prediction errors for weak 1‐generics and show that this phenomenon affects certain c.e. sequences as well. On the other hand, a notion of optimal predictor is considered. It is shown that there is a sequence for which increasingly better predictors exist but for which no predictor is optimal.

Affiliations:
Kalociński D.-University of Warsaw (PL)
Steifer T.-IPPT PAN
3.Lewandowski M., Walczak M., Witek B., Rozbicki J., Steifer T., Demonstrator przenosnego systemu Phased-Array z funkcją Full-Matrix Capture, BADANIA NIENISZCZĄCE I DIAGNOSTYKA, ISSN: 2451-4462, Vol.3, pp.70-71, 2018
Abstract:

Ultradźwiękowe systemy Phased-Array (PA) umożliwiają detekcję i ocenę wad za pomocą wieloelementowych głowic ze skanowaniem elektronicznym. Zaawansowane metody kierowania wiązki oraz wizualizacji znacznie ułatwiają badania obiektów o skomplikowanej geometrii. Należy jednak pamiętać, ze klasyczna metoda PA bazuje na tych samych zasadach fizycznych, co skanowanie standardowymi głowicami jednoelementowymi i posiada te same ograniczenia. W naszym laboratorium pracujemy nad implementacją nowej klasy metod obrazowania UT, które wykorzystują technikę Full-Matrix Capture (FMC) oraz Total Focusing Method (TFM). Metody te dają zupełnie nowe możliwości rekonstrukcji obrazów wad i pozwalają na uzyskanie jednorodnej rozdzielczości poprzecznej w całej głębokości badania. W tym celu zbudowaliśmy demonstrator przenośnego systemu PA wyposażony w funkcje FMC i TFM. Akwizycja pełnej macierzy ech oraz przetwarzanie softwarowe na wbudowanym procesorze GPU (Nvidia Tegra) zapewniają duże możliwości przetwarzania i analizy sygnałów. Demonstrator jest wyposażony w 32-kanały akwizycji w konfiguracji 32:128 i współpracuje ze standardowymi głowicami PA firmy Olympus.

Keywords:

UT, Phased-Array, akwizycja pełnej macierzy, GPU

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Witek B.-IPPT PAN
Rozbicki J.-IPPT PAN
Steifer T.-IPPT PAN
4.Lewandowski M., Walczak M., Steifer T., Zastosowanie metody pełnej akwizycji macierzy do wizualizacji wad w technice UT Phased-Array, PRZEGLĄD SPAWALNICTWA, ISSN: 0033-2364, Vol.88, No.10, pp.43-45, 2016
Abstract:

Ultradźwiękowe systemy Phased-Array pozwalają na różne tryby skanowania i wizualizacji wad oraz zapewniają wyższą jakość inspekcji niż tradycyjne systemy jednokanałowe. Kolejnym krokiem w rozwoju tych systemów będzie metoda akwizycji pełnej macierzy oraz zaawansowane algorytmy rekonstrukcji obrazów. W artykule przedstawiono zasady działania tych technik oraz wymagania jakie stawiają one przed systemami akwizycji i przetwarzania sygnałów. Zaprezentowano także badawczy system Uniwersalnej Platformy Ultradźwiękowej, który został opracowany specjalnie do testowania i praktycznego wdrażania tych metod. Platforma posłużyła do badań i porównania dwóch metod rekonstrukcji przy wykorzystaniu akwizycji pełnej macierzy – metody STA (Synthetic Transmit Aperture) i metody PWI (Plane Wave Imaging).

Keywords:

UT Phased-Array, akwizycja pełnej macierzy, syntetyczna apertura

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Steifer T.-IPPT PAN

Conference papers
1.Lewandowski M., Walczak M., Witek B., Rozbicki J., Steifer T., A GPU-Based Portable Phased-Array System with Full-Matrix Capture, IUS 2018, IEEE International Ultrasonics Symposium, 2018-10-22/10-25, KOBE (JP), DOI: 10.1109/ULTSYM.2018.8579964, pp.1-3, 2018
Abstract:

The widely adopted ultrasound Phased-Array (PA) systems for nondestructive testing (NDT) use standard beamforming for line-by-line image creation. The introduction of the new full-matrix capture (FMC) technique enables the implementation of advanced processing algorithms (e.g. the total focusing method, multi-pass adaptive techniques). However, the limited availability of portable PA systems with FMC capabilities prevents widespread introduction. Our goal was to demonstrate the feasibility of a portable PA solution with FMC and advanced processing with the help of a mobile GPU. Using an OEM ultrasound front-end module (us4us Ltd., Poland), we integrated a complete PA system with an embedded Nvidia Tegra X2 module. An external probe adapter enables a direct connection to commercial Olympus-NDT PA probes with up to 128-elements (32-element active RX aperture). The system is fully programmable, both in the front-end (TX/RX schemes, acquisition parameters), as well as in the digital signal processing chain. Raw RF data is acquired and transferred to mobile GPU memory for processing. The algorithm can be conveniently implemented using a standard Nvidia CUDA toolkit. We implemented real-time B-mode imaging with the total focusing method for demonstration purposes. The presented all-in-one system is a fully flexible tool for the research and evaluation of novel Phased-Array FMC methods and complex signal processing algorithms. An extended programmability and real-time access to raw channel data allows to create custom solutions specifically dedicated to any one NDT application. Mobile GPU parallel processing provides a strong enough performance for real-time imaging. Its small size and low-power consumption make the system an ideal candidate for a portable industrial flaw detector with advanced processing.

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Witek B.-IPPT PAN
Rozbicki J.-IPPT PAN
Steifer T.-IPPT PAN
2.Rozbicki J., Witek B., Steifer T., Lewandowski M., Doppler-based blood pressure measurement system for patients supported by a continuous-flow rotary left ventricular assist device, IUS 2017, IEEE International Ultrasonics Symposium, 2017-09-06/09-09, Washington (US), DOI: 10.1109/ULTSYM.2017.8091990, pp.1-4, 2017
Abstract:

The medical management of patients with continuous-flow left ventricular assist devices (LVADs) requires frequent measurement and analysis of various physiological parameters. Among the most important is blood pressure (BP), which cannot be reliably measured by the standard oscillometric method because of an impaired pulsation due to continuous flow. The objective of this work is to show the feasibility of ultrasound-based BP measurement in a portable, easy to use device for patients with LVAD in home-based rehabilitation environments, enabling long-term remote monitoring. We have implemented a BP measurement system which uses continuous wave (CW) Doppler ultrasound for blood flow detection. The system is based on a standard cuff design with custom analog CW circuitry connected to a high-performance, low-power 32-bit microcontroller (ARM Cortex-M7). The uC is responsible for system control, as well as Doppler signal acquisition and processing. A dedicated ultrasound probe equipped with an elastic strap is placed over the radial artery. In the target solution, the cuff pressure and CW signal will be analyzed in real-time to provide systolic and/or mean blood pressure. At present, we have acquired raw signals for off-line analysis. The system was tested in clinical experiments both on healthy patients and patients with three types of commercially available LVADs (HeartWare, HeartMate II and HeartMate III). The observed morphology of Doppler signals in patients with LVADs was much more variable between patients and pumps. In most cases, we were able to estimate the systolic pressure, but the measurement of diastolic pressure was not conclusive. We observed variable blood flow patterns generated by the Lavare cycle (a periodic speed modulation feature of some LVADs), which further complicates the estimation. A prototype of an automatic BP measuring device for patients with rotary LVADs has been demonstrated. In the next step, we are planning an animal validation study with invasive blood pressure monitoring

Keywords:

Biomedical monitoring, Doppler effect, Blood pressure, Blood, Pressure measurement, Ultrasonic variables measurement, Standards

Affiliations:
Rozbicki J.-IPPT PAN
Witek B.-IPPT PAN
Steifer T.-IPPT PAN
Lewandowski M.-IPPT PAN
3.Lewandowski M., Walczak M., Witek B., Steifer T., A GPU-based Ultrasound Phased-Array Research System for Non-destructive Testing, IUS 2016, IEEE International Ultrasonics Symposium, 2016-09-18/09-21, Tours (FR), DOI: 10.1109/ULTSYM.2016.7728843, pp.1-4, 2016
Abstract:

Ultrasound Phased-Array (PA) systems for nondestructive testing (NDT) use standard beamforming for line-byline image creation. New methods utilizing full-matrix capture (FMC) enable the application of advance processing algorithms, such as the total focusing method and multi-pass adaptive techniques for enhanced flaw visualization. The effective FMC data acquisition and its real-time processing require a very high data throughput and powerful computational resources. Most commercial PA systems support some form of FMC acquisition, but the limited external data bandwidth prevents this mode of operation from being useful. We have developed a fully programmable ultrasound research system capable of performing FMC data acquisition and image reconstruction with a high framerate. The ultrasound platform is supporting up to 192 parallel TX/RX electronics channels integrated with an embedded control PC and a GPU cluster for parallel processing. The implemented software libraries give the end-user control over TX/RX schemes, the acquisition process and signal processing algorithms. This all-in-one system is a fully flexible tool for the research and evaluation of novel Phased-Array FMC imaging methods and complex signal processing algorithms.

Keywords:

GPU, ultrasound, Phased-Array

Affiliations:
Lewandowski M.-IPPT PAN
Walczak M.-IPPT PAN
Witek B.-IPPT PAN
Steifer T.-IPPT PAN
4.Steifer T., Klimonda Z., Lewandowski M., Multiply and Sum Spatial Compounding in Plane Wave Imaging, IUS 2016, IEEE International Ultrasonics Symposium, 2016-09-18/09-21, Tours (FR), DOI: 10.1109/ULTSYM.2016.7728887, pp.1-3, 2016
Abstract:

This paper is a part of the IUS 2016 Planewave Imaging Challenge submission. Spatial compounding of several low-resolution images taken from different angles is a well-established 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 low-resolution images.

Keywords:

ultrasound, plane wave imaging

Affiliations:
Steifer T.-IPPT PAN
Klimonda Z.-IPPT PAN
Lewandowski M.-IPPT PAN
5.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