Wyniki 11-20 spośród 34 dla zapytania: authorDesc:"Tomasz RYMARCZYK"

Image reconstruction with discontinuous coefficient in electrical impedance tomography

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The problem of the image reconstruction in Electrical Impedance Tomography (EIT) is a highly ill-posed inverse problem. There are mainly two categories of image reconstruction algorithms, the direct algorithm and the iterative algorithm which was used in this publication. The representation of the shape of the boundary and its evolution during an iterative reconstruction process is achieved by the level set function and the Chan-Vese model. The forward problem was solved by the finite element method. Streszczenie. Rekonstrukcja obrazu w tomografii impedancyjnej jest dokonywana poprzez rozwiązanie zagadnienia odwrotnego. Stosując algorytmy deterministyczne mamy do dyspozycji dwie kategorie rozwiązania: metodę bezpośrednią i model iteracyjny, który został wykorzystany w tej publikacji. W procesie rekonstrukcji została użyta funkcja zbiorów poziomicowych oraz model Chana-Vese (Rekonstrukcja obrazu w zagadnieniu odwrotnym tomografii impedancyjnej). Keywords: Electrical Impedance Tomography, Level Set Methods, Chan-Vese Model, Inverse Problem Słowa kluczowe: tomografia impedancyjna, metoda zbiorów poziomicowych, model Chana-Vese, zagadnienie odwrotne Introduction In this paper was proposed a method based on the combination level set idea [5,7,8] and the finite element methods [2] to solve the inverse problem in the electrical impedance tomography. The presented method was based on a numerical scheme for the identification of piecewise constant conductivity. Electrical Impedance Tomography Electrical impedance tomography is a widely investigated problem with many applications in physical and biological sciences [3,4]. It is well known that the inverse problem is nonlinear and highly ill-posed. The forward problem in EIT is solved by Laplace’s equation: (1) div( grad u)  0 where: u - electric potential,  - conductivity. The following functional is minimized: (2)     [...]

Using Electrical Resistance Tomography to Detect Leaks in Landfills DOI:10.15199/48.2017.12.39

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Electrical tomography (ERT) is known that the inverse problem is nonlinear and highly ill-posed [13,18-24]. The problem is the low level of measured values which should be measured quite accurately and in a very short time. ERT involves placing electrodes on the examined object. The two electrodes are connected to AC power and the voltage drop is measured on others. Then, power supply is connected to the next two electrodes, and measuring steps are repeated until each electrode is connected to power supply. The measurement in electrical resistance tomography involves placing electrodes on the examined object. This solution allows to obtain a conductivity distribution within the test object, and this consequently allows a distinction between materials of different conductivity. Effective algorithms in the optimization process are topological methods [10-12, 14-17]. In carrying out further measurements over time and comparing them with previous we can observe the changes occurring in the study area. Fig. 1. Geophysical measurement model ERT is a geophysical technique in which DC electrical current is injected into the ground between one pair of electrodes and the voltage is measured between another pair [14]. Electrical signals are then transmitted through selected electrode locations while electrical potential measurements are recorded at numerous other locations. This process is repeated systematically for many different source-receiver combinations and the resulting data-set enables the reconstruction of a cross-section through the survey area [1-5,8,9]. The cross-sectional image, or tomographic slice, depicts a spatial distribution of electrical resistivity, which is closely related to the internal structure of the object. Contrasts in the electrical properties of different geological materials enable earth scientists to noninvasively map structures in the subsurface. Fig. 2. ERT measurements in the geophysical environm[...]

Implementation Image Analysis and Optimization Techniques in e-Medicus System DOI:10.15199/48.2018.01.24

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In this paper. gradient reconstruction algorithms, medical and stereoscopic images in e-Medicus system were implemented. The reconstruction problem is a nonlinear and ill-posed, whose solution calls for special regularized algorithms [6-8]. In many cases the linear systems arising in practice consist of real number coefficients and data. The image reconstruction is very sensitive to the ubiquitous modelling errors which are caused by inaccurately known auxiliary variables of the measurement model [21-25]. Figure 1 presents the model of the imaging system. Fig. 1. The model of the imaging system The image data is of immense practical importance in medical informatics. Medical images, such as Computed Axial Tomography (CAT), Magnetic Resonance Imaging (MRI), Ultrasound, and X-Ray, in standard DICOM formats are often stored in Picture Archiving and Communication Systems (PACS) and linked with other clinical information in EHR clinical management systems. Research efforts have been devoted to processing and analysing medical images to extract meaningful information such as volume, shape, motion of organs, to detect abnormalities, and to quantify changes in follow-up studies. Recent advances in a wide range of medical imaging technologies have revolutionized how we view functional and pathological events in the body and define anatomical structures in which these events take place. X-ray, CAT, MRI, Ultrasound, nuclear medicine, among other medical imaging technologies, enable 2D or tomographic 3D images to capture in-vivo structural and functional information inside the body for diagnosis, prognosis, treatment planning and other purposes. Stereoscopic images Stereoscopic imaging techniques allow for 3D images. Simultaneous recording of two images allows for the mutual dependence of the spatial object, the distance from the observer and the depth of the scene. In order to obtain stereosc[...]

Effective algorithm for tomography imaging in threedimensional problems DOI:10.15199/48.2019.03.27

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There are many different methods to optimize the imaging problem solution [1-11]. Let us consider an Ultrasonic wave for which we can assume propagation along straight lines. Using this feature, an effective modification of an important part of image reconstruction algorithm (called Algebraic Reconstruction Techniques - ART), invented in 1938 by S. Kaczmarz, has been proposed in this paper. The essence of proposed algorithm modification in 3D space is an approximation of the voxel, so far treated as cube, by a sphere inscribed in this cube. The attempt of using sphere-shaped voxels instead of cubic voxels could be questionable. In case of cubes the whole object volume can be covered because any wall of one cubic cling to another wall of the neighbouring cube. In case of sphere, it touches another sphere only in one point. So, between spheres there exists volume of object outside spheres which is not contained in voxels. The authors refer to this issue later in this paper (for example Fig. 6 and Fig. 7) showing that it has no significant influence on imaging. This modification is one more simplifying assumption for that kind of imaging. That is why the main goal of this paper is to prove effectiveness of such an approach by numerical experiment. What is more, such modification allows to significantly accelerate the method for determining voxels, through which the ray passes in the considered region. In such a way we have got much faster imaging software, which is particular important in cases where "on line" imaging is needed. Time profit is particularly high for 3D problems [12- 18]. Tomographic images construction in 3D space In the case of the modelling area in 3D space, you must make its discretization on a cube voxel, in which the points common for rays and voxel walls should be determined (see for example Fig. 1). Such calculations are pretty complicated. Ray passing through the voxel perforate two of six walls. Th[...]

Tomography Technology Application for Workflows of Gases Monitoring in the Automotive Systems

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Taking into consideration growing ecology and safety demands, there is a need for more accurate and cheaper ways to monitor workflows of gases, which can be used in automotive applications. Such investigations come into prominence in case of more commonly applied gas systems, that use hydrocarbons as well as hydrogen. In case of running down of oil resources, they are predicated as the most prob[...]

Level set methods in electrical impedance tomography

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This paper presents the applications of the level set function for identification the unknown shape of an interface motivated by Electrical Impedance Tomography (EIT). A new approach was adopted based on a continuous approximation of material coefficient distribution using a combination of the level set methods and the finite element method. The representation of the shape of the boundary and it[...]

Applying the level set methods and the immersed interface method in EIT

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This paper presents a new approach was based on a continuous approximation of material coefficient distribution using level set methods and the immersed interface method. The representation of the shape of the boundary and its evolution during an iterative reconstruction process is achieved by the level set method. The immersed interface method provides an effective discretisation for differential equations with discontinuous coefficients across a interface. Streszczenie. W pracy została przedstawiona nowa metoda rekonstrukcji obrazu tomograficznego przy użyciu metody zbiorów poziomicowych oraz metody granicy podobszarów. W procesie iteracyjnym za pomocą metody zbiorów poziomicowych dokonano reprezentacji kształtu brzegu i jego ewolucji. Metoda granicy podobszarów została wskazana ja[...]

A piecewise-constant minimal partition problem in the image reconstruction

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This paper presents the applications for identification the unknown shape of an interface motivated by Electrical Impedance Tomography (EIT) by using the Mumford-Shah algorithm and level set methods. The conductivity values in different regions are determined by the finite element method. The representation of the shape of the boundary and its evolution during an iterative reconstruction process is achieved by the level set method. The Mumford-Shah functional was proposed in the iterative algorithm. Streszczenie. Publikacja przedstawia aplikację do identyfikacji nieznanych obiektów w impedancyjnej tomografii komputerowej przy użyciu algorytmu Mumford-Shaha oraz metody zbiorów poziomicowych. Wartość konduktywności wyznaczana jest za pomocą metody elementów skończonych. Nieznane obiekt[...]

Jakość obrazowania w tomografii wielościeżkowej

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Współczesne tomograficzne techniki pomiarowe pozwalają na dość dokładne monitorowanie badanych obiektów. Praca przedstawia problematykę uzyskiwania odwzorowań tomograficznych o wysokiej jakości. W pracy zamieszczono przykład badań symulacyjnych obiektu o złożonym kształcie. Zastosowane metody umożliwiły uzyskanie obrazów tomograficznych wiernie odwzorowujących badane fantomy. Abstract. Today tomographic measurement techniques allow fairly accurate monitoring of the test objects. The work presents the problem of obtaining high quality tomography images. This paper contains examples of simulation researches of the complex shape objects. Chosen methods made it possible to obtain tomographic images that accurately map tested phantoms. (Quality of Imaging in Multipath Tomography). Słowa k[...]

ECT Measurement System with Optical Detection for Quality Control of Flow Process DOI:10.15199/48.2016.12.40

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Multi-phase flow measurement technologies are still built and improved. There is a clear trend in the industry to implement more optimum related functions, where the focus is put on an active control and the monitoring system. Control related active optimum functions can only be realised with a system that allows the electronic control. Electrical capacitance tomography (ECT) is a method of imaging cross-sections of vessels and pipelines containing dielectric material. Permittivity distribution is determined with a multi-electrode sensor and interpreted by software. This paper provides description of the device as well as results of exemplary measurements. Streszczenie. Technologie pomiarowe przepływu wielofazowego są wciąż budowane i ulepszane. Istnieje wyraźna tendencja w przemyśle do realizacji funkcji związanych z bardziej optymalnym sterowaniem, w którym nacisk kładziony jest na aktywną kontrolę i system monitoringu. Optymalizacja funkcji do aktywnej kontroli może być realizowana tylko w systemie, który umożliwia sterowanie elektroniczne. Elektryczna tomografia pojemnościowa (ETP) jest metodą obrazowania przekrojów naczyń i rurociągów zawierających materiał dielektryczny. Przenikalność elektryczna jest wyznaczana za pomocą czujnika wieloelektrodowego i interpretowana przez oprogramowanie. Niniejszy dokument zawiera opis urządzenia, jak również przykładowe wyniki pomiarów.(System pomiaru ETP z optyczna detekcją do kontroli jakości procesów przepływu). Keywords: Electrical Capacitance Tomography, Image Analysis, Sensors Słowa kluczowe: elektryczna tomografia pojemnościowa, analiza obrazów, sensory Introduction Simple and low cost intrusive probes have been used in many operation systems to obtain flow information. Process tomography becomes even more appealing when nonintrusive sensors are used to obtain the cross-sectional images. Designed control system allows for correlative studies using sets of measuring electrodes (Fig. 1). The [...]

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