Staff

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

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

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.

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

Abstract:
The paper presents chosen results obtained during the investigation of welded joints (laser, spot and friction) tested using acoustic microscopy method. Detection of welds properties and the defects strongly depends on ultrasonic transducer’s parameters. For the purpose of this research a prototype hardware setup was built – enabling evaluation of various types of ultrasonic probes. The system can be easily adjusted to the geometry of an object and is well equipped with appropriate software for the analysis and processing of images such as B-scan or C-scan. The setup enables determination of welds geometry, in particular the depth of the weld penetration in some cases.

Keywords:
spot welds, high frequency ultrasonic imaging

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

Abstract:
Ultrasound transmit push sequences put a high stress on a pulser IC due to power dissipation that could result in overheating. The aim of this work was to determine the safe range of parameters of push sequences for a high-voltage, high-speed, 4-channel pulser STHV748 (STMicroelectronics). The impact of using ceramic capacitors and electrolytic capacitors on the HV supply was also examined. The reaction of the pulser was measured with three output loading conditions. A safe range of values of pulser voltage for a given transmit frequency and sequence length were determined by monitoring chip temperature. Additionally, maximum pulse repetition frequency was evaluated in function of the maximum supply voltage. The STHV748 pulser is capable of generating push sequences. The duty-cycle is a key parameter that determines the safe operating conditions of the pulser. Limiting the amplitude of the HV supply enables us to increase push burst duration or decrease the frequency of the transmit signal.

Keywords:
acoustic radiation force, shear wave imaging, push sequences, HV pulser

Abstract:
The objective of our project is to develop a complete ultrasound platform with real-time GPU processing. The platform is designed to be modular and scalable both in number of ultrasound channels (64-256), as well as in communication bandwidth and processing power. By standardizing on the PCIe switch fabric, we are planning to integrate all the ultrasound modules and processing resources (GPU) in a single rack enclosure. Using PCIe direct peer-to-peer communication for transferring the data from the ultrasound acquisition modules to the GPUs, we maximize the system bandwidth and minimize CPU usage. The first developed module of our platform is RX64 - a 64-channel ultrasound acquisition PCIe card. The RX64 contains a high-end FPGA Altera Stratix IV 70 GX interfaced to: two 32-channels mixed-signal front-end ultrasound modules and two 64-bit 8GB DDR3 SO-DIMM memories for data buffering. We also develop GPU kernels for SAFT based ultrasound imaging, as well as GPU Framework for building complete signal processing pipeline.

Keywords:
ultrasonic imaging, synthetic aperture, GPU, FPGA

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

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