DWUWYMIAROWE MODELOWANIE SONDY DO ELEKTRYCZNEJ TOMOGRAFII POJEMNOŚCIOWEJ W PAKIECIE ECTSIM

Electrical capacitance tomography is used to visualize a spatial distribution of dielectrical permittivity of materials placed in a tomographic sensor. An image is reconstructed from measurements of mutual capacitances of electrodes placed around the examined volume. This technique is characterized by very high temporal resolution – it is possible to achieve even few thousands of images per second. One of drawbacks of the method is low spatial resolution. Electrical capacitance tomography is mainly used in industry, e.g. for multiphase flow visualization. One of important elements of a tomographic system is a sensor which parameters influence quality of measurements and therefore affects quality of reconstructed images. In the Division of Nuclear and Medical Electronics a Matlab toolbox called ECTsim was developed. It is used for modelling of sensors, simulations of electrical field and image reconstruction. In this article we present the latest improvement which is modelling of a sensor using algebra of sets. Using primitive elements like rectangle and sector of a ring it is possible to perform operations like union, intersection and difference of two elements with a designed language. With such tools it is easy to prepare complex models of tomographic sensors which have different geometries. In this paper we show two models of sensors with different geometry in order to show how ECTsim solves forward problem.Elektryczna tomografia pojemnościowa służy do obrazowania rozkładu przenikalności elektrycznej materiałów w sondzie. Obraz rekonstruowany jest dzięki pomiarom pojemności wzajemnych elektrod umieszczonych wokół badanego obszaru. Ta technika obrazowa charakteryzuje się dużą rozdzielczością czasową – możliwe jest obrazowanie nawet kilku tysięcy przekrojów na minutę. Wadą jest niska przestrzenna zdolność rozdzielcza. Elektryczną tomografię pojemnościową stosuje się w przemyśle, między innymi do obrazowania przepływów wielofazowych. Istotnym elementem systemu tomograficznego jest sonda, której parametry wpływają na jakość pomiaru, a tym samym na jakość rekonstruowanego obrazu. W Zakładzie Elektroniki Jądrowej i Medycznej stworzono pakiet ECTsim uruchamiany w środowisku Matlab, który służy do modelowania sond tomograficznych, symulacji pola elektrycznego oraz rekonstrukcji obrazów. W niniejszym artykule opisano najnowszą modyfikację pakietu polegającą na modelowaniu sondy przy pomocy algebry zbiorów. Wprowadzono podstawowe kształty geometryczne, takie jak prostokąt i wycinek pierścienia, oraz zaproponowano język opisujący operacje sumowania, odejmowania i iloczynu elementów, co pozwala na proste tworzenie złożonych modeli sond tomograficznych o różnych geometriach. W artykule pokazujemy modele dwóch różnych sond tomograficznych i prezentujemy, jak ECTsim rozwiązuje problem prosty

PAKIET DO TRÓJWYMIAROWEGO MODELOWANIA I REKONSTRUKCJI OBRAZÓW W ELEKTRYCZNEJ TOMOGRAFII POJEMNOŚCIOWEJ

Electrical Capacitance Tomography is used to visualize a spatial distribution of electric permittivity in a tomographic sensor. ECT is able to create even thousands of frames per second which is suitable for application in the industry, e.g. monitoring of multiphase flows or material mixing. A tool for sensor modelling and image reconstruction is needed in order to develop improved solutions and to better understand phenomena in ECT. A software for 2D and 2D modelling is developed in the Division of Nuclear and Medical Electronics. In this paper a Matlab toolbox called ECTsim for 3D modelling is presented.Elektryczna tomografia pojemnościowa jest używana do obrazowania przestrzennego rozkładu przenikalności elektrycznej w sondzie tomograficznej. Elektryczna tomografia pojemnościowa pozwala uzyskać nawet kilka tysięcy obrazów na sekundę co sprawia, że znajduje zastosowanie w przemyśle, na przykład do monitorowania przepływów wielofazowych lub mieszania materiałów.  Dla uzyskania lepszych rezultatów obrazowania i lepszego zrozumienia zjawisk zachodzących w elektrycznej tomografii pojemnościowej potrzebne są narzędzia do modelowania i rekonstrukcji obrazów. W Zakładzie Elektroniki Jądrowej i Medycznej rozwijane jest oprogramowanie do modelowania 2D i 3D. W artykule przedstawiono pakiet ECTsim dla środowiska Matlab do modelowania trójwymiaroweg

Low Frequency Bio-Electrical Impedance Mammography and Dielectric Measurement

Assessment of electrical impedance of biological tissues at low frequencies offers a great potential for a safe, simple, and low-cost medical breast imaging techniques such as mammography. As such, in this dissertation a mammography method which uses tissue electrical impedance to detect breast malignancies was developed. The dissertation also introduces a new technique for measuring the dielectric properties of biological tissues at low frequencies. The impedance mammography technique introduced in this study is founded on the assumption that dielectric values of breast malignancies are significantly higher than the dielectric values of normal breast tissues. While previous studies have shown that this assumption is valid at high frequencies (50MHz-20GHz), less research efforts have been dedicated to ascertain the validity of such assumption at low frequencies (in silico and tissue mimicking phantom studies. Results of this investigation suggest that imaging the electrical impedance properties of biological tissues through the proposed electrical impedance mammography can be potentially employed for breast cancer detection in a reliable and safe manner

PRZEDZIAŁAMI LINIOWE ITERACYJNE ALGORYTMY REKONSTRUKCJI OBRAZÓW W ELEKTRYCZNEJ TOMOGRAFII POJEMNOŚCIOWEJ

The paper concerns the non-linear algorithms for image reconstruction in electrical capacitance tomography for which Jacobi matrix computation time is very long. The paper presents the idea of an iterative linearization in nonlinear problems, which leads to a reduction in the number of steps calculating Jacobi matrix. The linear Landweber algorithm with sensitivity matrix updating and non-linear Levenberg-Marquardt algorithm with Jacobi matrix updating in selected steps only were presented.Artykuł dotyczy nieliniowych algorytmów rekonstrukcji obrazów w elektrycznej tomografii pojemnościowej, dla których czas wyznaczenia macierzy Jacobiego jest bardzo długi. W pracy przedstawiono ideę iteracyjnej linearyzacji w problemach nieliniowych, która prowadzi do zmniejszenia liczby kroków wyznaczających macierz Jacobiego. Przedstawiono liniowy algorytm Landwebera z uaktualnianiem macierzy wrażliwości oraz algorytm Levenberga-Marquardta z wyznaczaniem macierzy Jacobiego tylko w wybranych krokach

Electrical Impedance Based Spectroscopy and Tomography Techniques for Obesity and Heart Diseases

Despite advances in diagnosis and therapy, atherosclerosis cardiovascular disease remains the leading cause of morbidity and mortality. Predicting metabolically active atherosclerotic lesions has remained an unmet clinical need. Specially, atherosclerotic plaques that are prone to rupture are of extremely high-risk and can cause detrimental heart attacks and/or strokes, leading to sudden death. It has been shown that atheroscleroses is correlated to the level of obesity of an individual [1] Usually in clinical practice, the doctor will assess a patient's "risk factor" based on his or her Body Mass Index (BMS), and measurement of the waist circumference. Meanwhile the level of fatty droplet deposits in the liver is an important bio-marker to assess the patient's risk factor, however the patient will need to undergo radiation imaging such as CT scan or MRI scan. For the vulnerable plaques that can lead to sudden rupture, the ability to distinguish them at an early stage remains largely lacking. Therefore it is of great clinical interest to find improved diagnostic techniques to identify and localize such vulnerable plaques. Meanwhile, lipid has significantly lower electrical impedance than the rest of the vessel tissues in certain frequency bands [2]. In this thesis we explore spectroscopic and tomographic methods to characterize such plaques. In addition, with the Electrical Impedance Tomography method we will propose a novel method to detect fatty liver in an early stage with non-radiating and non-invasive manner.</p

Active complex electrode (ACE1) electrical impedance tomography system & anatomically inspired modeling of electrode-skin contact impedance, The

Includes bibliographical references.2016 Summer.Electrical Impedance Tomography (EIT) is a technique used to image the varying electrical properties of biological tissues or tissue conductivity and permittivity. There are many clinical uses of EIT, but as a newer imaging modality, there is interest in improving hardware to acquire EIT data, creating models of the system and generating high quality images. The two main contributions of this work include: (1) EIT hardware advancements and (2) software modeling to simulate measured human subject data. Specifically, this dissertation includes the design and testing of Colorado State University's first EIT system, the pairwise current injection active complex electrode (ACE1) system for phasic voltage measurement. The ACE1 system was primarily designed for thoracic EIT applications, and its performance and limitations were tested through a variety of experiments. Additionally, the EIT forward problem was used to investigate electrode-skin contact impedance

Advanced electrode models and numerical modelling for high frequency Electrical Impedance Tomography systems

The thesis discusses various electrode models and finite element analysis methods for Electrical Impedance Tomography (EIT) systems. EIT is a technique for determining the distribution of the conductivity or admittivity in a volume by injecting electrical currents into the volume and measuring the corresponding potentials on the surface of the volume. Various electrode models were investigated for operating EIT systems at higher frequencies in the beta-dispersion band. Research has shown that EIT is potentially capable to distinguish malignant and benign tumours in this frequency band. My study concludes that instrumental effects of the electrodes and full Maxwell effects of EIT systems are the major issues, and they have to be addressed when the operating frequency increases. In the thesis, I proposed 1) an Instrumental Electrode Model (IEM) for the quasi-static EIT formula, based on the analysis of the hardware structures attached to electrodes; 2) a Complete Electrode Model based on Impedance Boundary Conditions (CEM-IBC) that introduces the contact impedances into the full Maxwell EIT formula; 3) a Transmission line Port Model (TPM) for electrode pairs with the instrumental effects, the contact impedance, and the full Maxwell effects considered for EIT systems. Circuit analysis, Partial Differential Equations (PDE) analysis, numerical analysis and finite element methods were used to develop the models. The results obtained by the proposed models are compared with widely used Commercial PDE solvers. This thesis addresses the two major problems (instrumental effects of the electrodes and full Maxwell effects of EIT systems) with the proposed advanced electrode models. Numerical experiments show that the proposed models are more accurate in the high frequency range of EIT systems. The proposed electrode models can be also applicable to inverse problems, and the results show promising. Simple hardware circuits for verifying the results experimentally have been also designed