Search results for "Electrical impedance tomography"
showing 10 items of 25 documents
From Feynman–Kac formulae to numerical stochastic homogenization in electrical impedance tomography
2016
In this paper, we use the theory of symmetric Dirichlet forms to derive Feynman–Kac formulae for the forward problem of electrical impedance tomography with possibly anisotropic, merely measurable conductivities corresponding to different electrode models on bounded Lipschitz domains. Subsequently, we employ these Feynman–Kac formulae to rigorously justify stochastic homogenization in the case of a stochastic boundary value problem arising from an inverse anomaly detection problem. Motivated by this theoretical result, we prove an estimate for the speed of convergence of the projected mean-square displacement of the underlying process which may serve as the theoretical foundation for the de…
Recent progress in electrical impedance tomography
2003
We consider the inverse problem of finding cavities within some body from electrostatic measurements on the boundary. By a cavity we understand any object with a different electrical conductivity from the background material of the body. We survey two algorithms for solving this inverse problem, namely the factorization method and a MUSIC-type algorithm. In particular, we present a number of numerical results to highlight the potential and the limitations of these two methods.
Explicit Characterization of Inclusions in Electrical Impedance Tomography
2001
In electrical impedance tomography one seeks to recover the spatial conductivity distribution inside a body from knowledge of the Neumann--Dirichlet map. In many practically relevant situations the conductivity is smooth apart from some inhomogeneities where the conductivity jumps to a higher or lower value. An explicit characterization of these inclusions is developed in this paper. To this end a class of dipole-like indicator functions is introduced, for which one has to check whether their boundary values are contained in the range of an operator determined by the measured Neumann--Dirichlet map. It is shown that this holds true if and only if the dipole singularity lies inside the inhom…
Toward morphological thoracic EIT: major signal sources correspond to respective organ locations in CT.
2012
Lung and cardiovascular monitoring applications of electrical impedance tomography (EIT) require localization of relevant functional structures or organs of interest within the reconstructed images. We describe an algorithm for automatic detection of heart and lung regions in a time series of EIT images. Using EIT reconstruction based on anatomical models, candidate regions are identified in the frequency domain and image-based classification techniques applied. The algorithm was validated on a set of simultaneously recorded EIT and CT data in pigs. In all cases, identified regions in EIT images corresponded to those manually segmented in the matched CT image. Results demonstrate the abilit…
Assessment of regional ventilation distribution: comparison of vibration response imaging (VRI) with electrical impedance tomography (EIT)
2013
BACKGROUND: Vibration response imaging (VRI) is a bedside technology to monitor ventilation by detecting lung sound vibrations. It is currently unknown whether VRI is able to accurately monitor the local distribution of ventilation within the lungs. We therefore compared VRI to electrical impedance tomography (EIT), an established technique used for the assessment of regional ventilation. METHODOLOGY/PRINCIPAL FINDINGS: Simultaneous EIT and VRI measurements were performed in the healthy and injured lungs (ALI; induced by saline lavage) at different PEEP levels (0, 5, 10, 15 mbar) in nine piglets. Vibration energy amplitude (VEA) by VRI, and amplitudes of relative impedance changes (rel.ΔZ) …
Novel technologies to detect atelectotrauma in the injured lung
2010
ABSTRACTCyclical recruitment and derecruitment of lung parenchyma (R/D) remains a serious problem in ALI/ARDS patients, defined as atelectotrauma. Detection of cyclical R/D to titrate the optimal respiratory settings is of high clinical importance. Image-based technologies that are capable of detecting changes of lung ventilation within a respiratory cycle include dynamic computed tomography (dCT), synchrotron radiation computed tomography (SRCT), and electrical impedance tomography (EIT). Time-dependent intra-arterial oxygen tension monitoring represents an alternative approach to detect cyclical R/D, as cyclical R/D can result in oscillations of PaO2 within a respiratory cycle. Continuous…
The Factorization Method for Electrical Impedance Tomography in the Half-Space
2008
We consider the inverse problem of electrical impedance tomography in a conducting half-space, given electrostatic measurements on its boundary, i.e., a hyperplane. We first provide a rigorous weak analysis of the corresponding forward problem and then develop a numerical algorithm to solve an associated inverse problem. This inverse problem consists of the reconstruction of certain inclusions within the half-space which have a different conductivity than the background. To solve the inverse problem we employ the so-called factorization method of Kirsch, which so far has only been considered for the impedance tomography problem in bounded domains. Our analysis of the forward problem makes u…
Chest electrical impedance tomography examination, data analysis, terminology, clinical use and recommendations: consensus statement of the translati…
2017
Electrical impedance tomography (EIT) has undergone 30 years of development. Functional chest examinations with this technology are considered clinically relevant, especially for monitoring regional lung ventilation in mechanically ventilated patients and for regional pulmonary function testing in patients with chronic lung diseases. As EIT becomes an established medical technology, it requires consensus examination, nomenclature, data analysis and interpretation schemes. Such consensus is needed to compare, understand and reproduce study findings from and among different research groups, to enable large clinical trials and, ultimately, routine clinical use. Recommendations of how EIT findi…
Principles of electrical impedance tomography and its clinical application
2008
This review outlines the basic principle, in addition to validated and upcoming clinical use of electrical impedance tomography (EIT). EIT generates functional tomograms of the thorax for detection of changes in regional lung aeration. These images allow an intraindividual comparison of changes in regional lung function. Specifically, EIT aims to optimize ventilation therapy in patients with acute lung failure.PubMed: National Library of Medicine and the National Institutes of Health.Studies with the key words "electrical impedance tomography" since 1983.Qualitative and quantitative results of the studies.We summarize basic principles of the technique and subsequent analyzing methods, and g…