Electrical Impedance Tomography (EIT) is a technique for imaging the spatial distribution of conductivity inside a body using the boundary voltages, in response to applied current patterns, to reconstruct an image. Even though EIT has been proved useful in several medical applications such as mechanical respiration and ventilation monitoring of the lungs, its reported success in localising cerebral conductivity changes due to brain stimulation is very scant. In the case of the human head, the amplitude of the brain response to stimulation is usually very small and gets contaminated with physiological noise initiated from inside the cranium or the scalp. Three types of evoked responses were experimentally investigated: auditory startle response (ASR), CO2 reactivity response, and transient hyperaemic response (THR). ASR is expected to be a result of the brain’s functioning processes. However, the responses to CO2 and THR are expected to be due to cerebral blood volume or flow, due to physiological intervention in blood supply. According to the results, even when the amplitude of EIT measurements shows profound variation as in the case of CO2 reactivation, those could not be physiologically linked to the targeted responses and have been shown to be initiated from the scalp. The consistency of the measurements in the case of CO2 reactivation response was poor (37.50-50%). Meanwhile in the case of THR, although the magnitude of conductivity changes was overall 50% smaller than the previous cases, the subject movement was not necessary. This could be a reason that the consistency of THR case was very good (87%), and this can emphasize the necessity to maintain the changes in the scalp at minimum levels. In the case of ASR the response magnitude was very small (six times smaller than the CO2 reactivity case), and the evoked response can be detected with only 50% consistency. To measure very small EIT signals (such as those expected due to brain function) effectively, one must improve the sensitivity of the measurements to conductivity changes by increasing the excitation current. The functional EIT for Evoked Response (fEITER) system used in our investigations was modified from its initial configuration to increase its excitation current from 1 mApk-pk to 2 mApk-pk or 1 mArms. The bit-truncation in the process of Phase-Sensitive Detection (PSD) has also been improved, to modify the original 16-bit data readout to be 24-bit data readout. These improvements have doubled the instrument’s sensitivity, and have substantially reduced the truncation error to about 183 times. The quality of the physiological waveform was also significantly improved. Therefore, one could study more effectively very fast brain response using the modified system. For example, the latency of responses can be more precisely extracted, or the monitoring of the conductivity change in a period of only a few tens of milliseconds is then possible. The reconstruction of brain images corresponding to these physiologically evoked responses has been the ultimate goal of this thesis. To ensure obtaining the correct images, some crucial issues regarding EIT reconstruction were firstly investigated. One of these issues concerns the modelling error of the numerical head models. The reconstruction requires an accurate model capturing the geometry of the subject’s head with electrodes attached and accurate in-vivo tissue conductivities. However, since it is usually impractical to have a personalised model for each subject, many different head models (including a subject model) were constructed and investigated, to evaluate the possibility of using a generic model for all subjects. The electrode geometry was also carefully included into the models to minimise error. Another issue concerns the appropriate reconstruction algorithm. A novel nonlinear reconstruction method, based on the difference imaging approach and Generalized Minimal Residual method (GMRes) algorithm, with optimal parameters and prior information, was proposed to deal with significant modelling errors. With this algorithm, the experimental results showed that it is possible to use a generic model for reconstructing an impedance change, but the magnitude of the change should be rather small. The last issue tackled was regarding the a priori choice of model parameters, and in particular the tissue conductivities. The tissue conductivities of the scalp and the skull were also estimated by a proposed methodology based on the Gauss-Newton method. The estimation showed that, compared to previous reported values, the conductivity of the scalp was higher, at 0.58 S/m, and that of the skull lower, at 0.008 S/m. Eventually, by exploiting the hardware and firmware advances in the measuring instrument in conjunction with the proposed modelling and reconstruction algorithm, processing our experimental EIT data captured on human heads and a head-like tank confirm that the localisation and imaging of conductivity changes occurring within the head is indeed possible. From the low quality measurements in the case of the CO2 reactivity response, the reconstructed images of this response do not reflect the true conductivity change. The consistency of the images to localise the sources of the changes was very poor (0-50%), i.e. the conductivity changing locations in the images were likely to be random. Our analysis suggests that the changes inside the cranium are likely to be due to the large change in the scalp. In the case of THR, the reconstructed images were able to localise the response in a similar manner to what had been found on the measurements, and the consistency was quite high (76%). Meanwhile, in the case of ASR, surprisingly the consistency of the images was 82%, much higher than the consistency of the measurements, which was only 50%. This was because the changing amplitude of the measurements was too small to be noticed by visualisation, and it was practically cumbersome to investigate all measurements. This statistic confirms that image reconstruction can reveal information that is not directly apparent by observing the measurements. In summary, EIT can be used in brain (function) imaging applications to some extent. The targeted response, which typically originates from inside the cranium is always infused with neurophysiological noise or physical noise at the scalp, and the amplitude of noise determines the possibility to localise the changes. It is also necessary for the desired response to have sufficiently large amplitude. These results show that EIT has been successful in THR and ASR, but for CO2 reactivity response, EIT lacks the necessary sensitivity.

Este trabalho estuda a técnica de reconstrução de imagens conhecido como tomografia por impedância elétrica em um domínio bidimensional. Esta técnica consiste na alocação de eletrodos na fronteira do volume e uma fonte injeta padrões de corrente através dos eletrodos e medem-se as voltagens resultantes na fronteira. Com estes dados estima-se a condutividade (ou resistividade) do interior do domínio criando-se uma imagem do mesmo. A tomografia por impedância elétrica é um problema inverso e mal posto no sentido de Hadamard. Estudam-se diversos métodos de solução para resolver o problema direto usando métodos numéricos como diferenças finitas e volumes finitos. Proporemos os métodos numéricos a serem aplicados na solução do problema direto os quais serão testados com problemas onde a solução analítica é conhecida. Posteriormente aplicaremos os métodos propostos ao problema especifico. Uma questão importante na reconstrução de imagens é propor a maneira como aproximar o Jacobiano (ou matriz de sensibilidade) do problema, assim desenvolvemos uma técnica para a aproximação do mesmo usando os dados fornecidos pelo problema direto. / In this work is studied the technique of reconstruction of images known as electrical impedance tomography for a two-dimensional domain. This technique consists in the allocation of electrodes on the border of the volume and a source injects patterns of current through the electrodes and then measuring voltages through the other electrodes. With these data it is estimated the conductivity (or resistivity) on the interior of the domain and an image is create of it. The electrical impedance tomography is an inverse and ill conditioned problem in the Hadamard sense. In this work, is studying some numerical methods to solve the direct problem and are applied numerical methods such as the finite difference method and the finite volume method. It is proposed some numerical methods to solve the direct problem which will be tested with analytical problems where the solution is known. Later, apply the methods proposed to the specific issue. An important issue in the reconstruction problems is about the Jacobian (or sensitivity matrix) aproximation, thus proposing a technique for the calculation of even using the data provided by the direct problem. Keywords:

Atualmente existem diversos métodos e equipamentos disponíveis no mercado para análise da biomecânica do movimento humano. No entanto, mesmo uma equipe multidisciplinar, dispondo de um laboratório completo de análise do movimento, pode falhar na identificação de quais grupos musculares estão sendo recrutados durante um exercício. Sobretudo quando a musculatura de interesse é profunda. O objetivo desta tese é propor formas de detectar a contração muscular através da Tomografia por Impedância Elétrica (TIE). Um modelo de elementos finitos de condução elétrica é utilizado para resolver o problema inverso através do algoritmo de Newton-Raphson de forma a obter as imagens de TIE. Um novo modelo de eletrodo e o método de erro de discretização da malha são introduzidos como forma de melhorar as imagens de TIE. Além disso, a variabilidade da impeditividade de tecidos musculo-esqueléticos é medida experimentalmente, in vivo tanto em repouso quanto em exercício. Os resultados mostram que o sangue tem um papel importante nas mudanças de impeditividade e que as variações medidas durante as contrações musculares parecem estar relacionadas à taxa de contração do movimento. As imagens de TIE, obtidas in vivo de um voluntário, apresentam um aumento de resistividade durante a contração muscular. / Presently, there are several methods and equipment available in the market for the biomechanical analysis of human movement. However, even a well trained multidisciplinary team, equipped with a complete motion analysis laboratory, may fail to identify which muscle groups are being recruited during an exercise. Specially when deep muscles are being considered. The main objective of this work is to propose forms to detect muscle contraction from Electrical Impedance Tomography (EIT) images. A finite element electrical conduction model is used to solve an inverse problem with Newton-Raphson algorithm in order to produce EIT images. A new electrode model is proposed and the mesh discretization error method is implemented to improve EIT images. Additionally the variability of impeditivity of musculo-skeletal tissues is measured experimentally in vivo both at rest and during exercise. The results show that blood has an important role in muscle impeditivity changes and that resistivity variations during muscle contractions seem to be related to movement contraction rate. The EIT images, obtained in vivo from a volunteer, show an increase of resistivity during muscle contraction.

Le toucher est considéré comme l’un des sens primordiaux à modéliser chez un robot afin de lui permettre de générer des comportements plus souples et plus agiles comme attraper un objet, toucher (ou être touché par) une personne. Même si les capteurs tactiles actuels sont encore très limités en comparaison à la peau humaine, combinés à la vision et à la proprioception, le développement de nouveaux capteurs proches de la peau humaine pourrait démultiplier les capacités d’interactions d’un robot afin d’interagir directement avec une personne en toute sécurité et de partager avec lui son environnement physique et social. A la différence de la peau humaine, les principaux capteurs tactiles utilisés en robotique actuellement ne sont capables de détecter des variations de pression et de poids que sur de petites surfaces uniquement. De plus, ceux-ci sont souvent très rigides et n’ont pas les propriétés élastiques de déformation de la peau humaine. Les travaux de cette thèse se basent sur le développement d’une interface tactile proche d’une "peau artificielle" en terme de surface de recouvrement (qui peuvent atteindre plusieurs dizaines de centimètres carrés) et de localisation des points de contact de quelques dizaines de millinewtons. Deux aspects principaux sont développés : (i) aspect d’ingénierie comprenant le développement d’un prototype de peau artificielle conçue pour un robot humanoïde afin de lui conférer une perception tactile, et (ii) aspect cognitifs qui s’appuient sur l’intégration de multiples rétroactions sensorielles (tactile, visuelle, proprioceptive) dans le but d’avoir un robot qui puisse interagir physiquement avec des personnes.Le prototype tactile développé est basé sur la reconstruction du champ électrique à la surface d’un matériau conducteur, suivant le principe de la Tomographie par Impédance Électrique (TIE). Notre innovation principale a été d’implémenter des techniques d’apprentissage par réseau de neurones artificiels afin de reconstruire l’information sans utiliser les techniques analytiques d’inversion de matrice coûteuse en temps de calcul. De plus, nous montrons que l’utilisation de réseaux de neurones artificiels permet d’avoir un système beaucoup plus biomimétique, indispensable pour comprendre la perception du toucher chez l’être humain.Nous avons ensuite abordé le problème de l’intégration des informations tactiles et motrices. Après avoir recouvert un bras manipulateur avec la peau artificielle, nous avons fait apprendre un réseau de neurones son schéma corporel et adapter sa compliance par retour tactile. Le fonctionnement du moteur est basé sur le contrôle par admittance du bras robotique. Des expériences montrent que les réseaux de neurones peuvent contrôler l’interaction adaptative entre le bras du robot avec une personne grâce à l’estimation du couple appris selon la position où la force tactile avait été appliquée lors de la phase d’apprentissage.Enfin, nous nous sommes intéressées à la problématique de la représentation du corps au niveau neuronal, comment les êtres humains perçoivent leur propre corps à travers tous les sens (visuel, tactile et proprioceptif). Nous avons proposé un modèle biologique au niveau du cortex pariétal qui s’appuie sur l’intégration de multiples rétroactions sensorielles du corps du robot (son bras) et sur la synchronisation des rétroactions visuelles et proprioceptives. Nos résultats montrent l’apprentissage d’une image corporelle et l’espace péri-personnel avec l’émergence de neurones qui codent une information spatiale visuo-tactile relative au déplacement du bras et centrée soit sur le bras robotique soit centrée sur l’objet. / The touch perception is considered as one of the crucial senses to be recreated in a robot so that it could generate a more flexible and agile behavior. For instance, grasping an object, as well as touch or be touched by a person. Although modern touch sensors are still very limited compared to the human skin, combined with vision and proprioception, the development of new sensors similar to human skin could multiply the robot’s capacity to interact directly and safely with a person, as well as to share his or her physical and social environment.Unlike human skin, the main touch sensors used in modern robotics are only capable of detecting the pressure and weight variations on small batches of surface. Moreover, they are often quite stiff and do not have the elastic deformation capacity intrinsic to the human skin. The purpose of this thesis is to develop a touch interface close to "artificial skin" in terms of the covered area (which can reach several square decimeters) and localization of the contact points (several dozen millinewtons). Two main aspects have been developed: (i) the engineering aspect including the development of an artificial skin prototype for a humanoid robot designed to impart a tactile perception, and (ii) the cognitive aspect that is based on the integration of multiple sensory feedbacks (tactile, visual, proprioceptive) in order to conceive a robot that can physically interact with people.The developed tactile prototype is based on the reconstruction of the electric field on the surface of a conductive material, following the principle of Electrical Impedance Tomography (EIT). Our main innovation was to implement the neural network learning techniques to reconstruct the information without using the inverse matrix analytical techniques which imply time consuming computation. Moreover, we show that the application of artificial neural networks allows to obtain a much more biomimetic system, essential to understand the perception of the human touch.Then, we addressed the issue of integrating tactile and motor information. After having covered a manipulator arm with artificial skin, we have learn a neural network its body schema and enables it to adjust its compliance with tactile feedback. The functioning of the motor is based on the admittance control of the robot arm. Experiments show that neural networks can control the adaptive interaction between the robot arm and a human being by estimating the torque perceived according to the position where the touch force had been applied during the learning phase.Finally, we turned our attention to the issue of the body representation at the neuronal level, namely, how human beings perceive their own body through all their senses (visual, tactile, and proprioceptive). We have proposed a biological model in the parietal cortex, which is based on the integration of multiple sensory feedbacks from the robot’s body (its arm) and on the synchronization of visual and proprioceptive feedback. Our results show the capacity to perceive the body image with the emergence of neurons that encode a spatial visual-tactile information of the arm movement and is centered on either the robotic arm or on the object.

No description available.

This thesis concerns the approximation of optimally controlled partial differential equations for applications in optimal design and reconstruction. Such optimal control problems are often ill-posed and need to be regularized to obtain good approximations. We here use the theory of the corresponding Hamilton-Jacobi-Bellman equations to construct regularizations and derive error estimates for optimal design problems. The constructed Pontryagin method is a simple and general method where the first, analytical, step is to regularize the Hamiltonian. Next its stationary Hamiltonian system, a nonlinear partial differential equation, is computed efficiently with the Newton method using a sparse Jacobian. An error estimate for the difference between exact and approximate objective functions is derived, depending only on the difference of the Hamiltonian and its finite dimensional regularization along the solution path and its L2 projection, i.e. not on the difference of the exact and approximate solutions to the Hamiltonian systems. In the thesis we present solutions to applications such as optimal design and reconstruction of conducting materials and elastic structures. / QC 20101110

​​Electrical resistance tomography (ERT) and electrical impedance tomography (EIT) are imaging techniques reconstructing the internal conductivity distribution image of an object based on voltage measurements at the periphery of the object with a given applied current. ERT uses a direct current (DC), while EIT uses an alternating current (AC). However, for low frequencies both ERT and EIT have the same governing equation, which is often referred to as a non-linear and ill-posed inverse problem. Both methods have diverse applications in biology, biomedicine, and industry. ​This master’s degree project aims to create a low-cost imaging system for the ERT, which is the main focus, as well as for the EIT. The project includes three main components: 1) Simulations and reconstructions using EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software), 2) Developing an experimental workbench (a measurement system), and 3) developing a machine learning model for the ERT. ​EIDORS was used to simulate and reconstruct ERT and EIT images. It was also used to generate training data for the machine learning model to be developed. ​The measurement system includes a circular water tank with electrodes, power supplies, and measurement units. Tanks with 8 and 16 electrodes were designed using 3D printers. Initially, aluminium electrodes provided inconsistent measurements due to magnetization and electrolysis, later replaced by graphite electrodes, offering better but not yet accurate enough results. ​After implementing reconstruction algorithms in EIDORS, a machine learning model was developed for ERT. It involved: 1) generating a training set, containing over 5000 simulated data points, 2) preprocessing the generated data set which included PCA dimensionality reduction, 3) and lastly a linear regression model developed. The model struggled with small object detection and occasional inconclusive results, likely due to limited training dataset diversity. Additionally, images of two cases were reconstructed using EIT and comparing it to ERT it can be concluded that EIT performs better than ERT. ​

Thesis (MScPhysio)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Question: What are the effects of Intermittent Positive Pressure Breathing (with and without a Positive End Expiratory Pressure [PEEP] Valve), compared to deep breathing exercises, on ventilation distribution in high-risk adults following open upper abdominal surgery (UAS)? Design: This study comprised an observational descriptive component as well as a prospective triple blind randomised controlled crossover trial with concealed allocation and patient, assessor and statistician blinding Participants: Seven patients at high risk for postoperative pulmonary complications following UAS Intervention: Deep breathing exercises (DBExs) were compared to Intermittent Positive Pressure Breathing (IPPB), with IPPB further applied with and without a PEEP Valve, using a randomised cross-over design with 30 minute washout duration between periods. Outcome measures: Global and regional impedance changes in the lungs were measured using Electrical Impedance Tomography. Vital signs, visual analogue pain scale (VAS) and modified Borg scale (MBS) were measured pre– and post-intervention. Results: A greater mean global lung impedance change ( Z) was detected with IPPB compared to DBExs (mean difference in Z 2803.8; 95% CI 5189.9 to 8512.5 and 2046 to 96047.9; P<0.01). These changes in lung impedance lasted 30 minutes before returning to baseline. There was no difference in Z when patients received IPPB with 5cmH20 PEEP compared to IPPB with no PEEP. No specific regional ventilation changes were noted. IPPB did not increase VAS, MBS scores or adversely affect vital signs. Conclusion: IPPB is an effective technique to improve lung volumes compared to deep breathing exercises. Further studies are required to investigate the effect of IPPB on clinical outcome. / AFRIKAANSE OPSOMMING: Vraag: Watter uitwerking het onderbroke positiewe-drukasemhaling (met én sonder ’n positiewe-endekspiratoriesedruk-[PEEP-]klep) in vergelyking met diepasemhalings-oefeninge op ventilasieverspreiding by hoërisikovolwassenes ná bo-buikchirurgie? Ontwerp: ’n Waarnemingsgegronde, vergelykende en ondersoekende, driedubbelblinde, verewekansigde gekontroleerde oorskakelproef, met verborge toewysing en blinding van pasiënte, die assesseerder en statistikus Deelnemers: Sewe pasiënte met ’n hoë risiko vir post-operatiewe pulmonêre komplikasies na bo-buikchirurgie Intervensie: Diepasemhalingsoefeninge (DBEx) is vergelyk met onderbroke positiewedrukasemhaling (IPPB), wat op sy beurt met én sonder ’n PEEP-klep toegepas is, met behulp van ’n verewekansigde oorskakelstudie met ’n halfuur lange uitspoeling tussen oorskakelings. Uitkomsmetings: Algehele en regionale impedansieveranderinge in die longe is met behulp van elektriese impedansietomografie gemeet. Vitale tekens, die visuele analoogskaal (VAS) en die aangepaste Borg-skaal (MBS) is voor, sowel as na die intervensie afgeneem. Resultate: ’n Groter gemiddelde algehele impedansieverandering ( Z) is opgemerk met IPPB in vergelyking met DBEx (gemiddelde verskil 2803.8; 95% CI 5189.9: 8512.5 en 2046: 96047.9; P<0.01). Hierdie veranderinge in longimpedansie het ’n halfuur of langer geduur voordat dit na die basislyn teruggekeer het. Daar was geen verskil in Z toe pasiënte IPPB met ’n PEEP-klep van 5cmH20 ontvang het teenoor IPPB sonder ’n PEEP-klep nie. Geen spesifieke regionale voorkeure is opgemerk nie. IPPB het nie die VAS- of MBS-tellings verhoog of vitale tekens verswak nie. Stellenbosch University https://scholar.sun.ac.za iv Gevolgtrekking: In vergelyking met DBEx, is IPPB ’n doeltreffende tegniek om longvolumes te verbeter. Verdere studies word vereis om die uitwerking van IPPB op kliniese uitkomste te ondersoek.

A principal causa da disfunção respiratória em equinos durante anestesia geral inalatória é atribuída à hipoxemia devido a formação de áreas de atelectasias. Visando reverter estes quadros são instituídas as manobras de recrutamento alveolar (MRA) através da administração de elevadas pressões no sistema respiratório. Estas manobras quando utilizadas de maneira inadequada podem contribuir para a formação de atelectasias, barotrauma, volutrauma e até mesmo atelectrauma; sendo de suma importância a sua monitoração. Com isso, uma nova técnica, a tomografia por impedância elétrica (TIE), vem sendo estudada, no qual, seu funcionamento se dá por emissão de corrente elétrica de baixa frequência e intensidade nos tecidos, gerando uma imagem dos tecidos avaliados. Sendo assim, o objetivo do presente estudo experimental foi avaliar se na espécie equina a TIE é capaz de visualizar as alterações de volume corrente global e regional, em pulmões saudáveis, durante a ventilação mecânica e escalonamento da PEEP como MRA. Para tanto foram utilizados 14 equinos de peso médio de 306 kg, submetidos a anestesia geral inalatória em decúbito dorsal. Os animais foram mecanicamente ventilados com volume corrente de 14 mL/kg e frequência respiratória de 7-9 mpm. Foi instituída manobra de recrutamento alveolar, aumentando-se a PEEP de 5 em 5 cmH2O, a cada 5 minutos, até 32 cmH2O, seguido de seu decréscimo também de 5 em 5 cmH2O, a cada 5 minutos, até 7 cmH2O. Foram realizadas coletadas de amostras de sangue arterial para hemogasometria, imagens do TIE e registrados os parâmetros hemodinâmicos e de mecânica respiratória em cada estágio do escalonamento da PEEP. Durante a MRA foram observados aumento na PaO2/FiO2 dos pacientes assim como aumento na complacência estática pulmonar, associado a uma diminuição no shunt pulmonar, e deslocamento da ventilação para região pulmonar dependente por meio da TIE, principalmente em PEEP acima de 17 cmH2O. Como efeitos adversos foram observados alterações em parâmetros hemodinâmicos sendo estas transitórias. Portanto o TIE demonstrou-se capaz de avaliar as mudanças de ventilação pulmonar durante a MRA e mostrou relação com os ganhos em oxigenação e mecânica pulmonar. / The main cause of respiratory dysfunction in horses under isoflurane anaesthesia is hypoxemia attributed to the atelectasis formation areas. In order to revert these sets, alveolar recruitment manoeuvres (ARM) are instituted through high pressures administration in the respiratory system. These manoeuvres when used improperly can contribute to the atelectasis formation, barotrauma, volutrauma and even atelectrauma; being of utmost importance its monitoring. A new technique, electrical impedance tomography (EIT), has been studied, in which its operation is due to the low frequency and intensity of electric current emission in the tissues, generating tissues images for evaluation. Therefore, the present experimental study aimed to evaluate whether in horses the EIT is able to visualize changes of global and regional tidal volume in healthy lungs during mechanical ventilation and titration of PEEP as ARM. For this purpose, 14 horses weighting 306 kg were used, undergoing general inhalation anaesthesia in dorsal recumbence. The animals were mechanically ventilated with tidal volume of 14 mL/kg and respiration rate of 7-9 bpm. An alveolar recruitment manoeuvre was instituted, increasing the PEEP by 5 cmH2O every 5 minutes until 32 cmH2O, followed by decreasing it by 5 cmH2O every 5 minutes to 7 cmH2O. Arterial blood samples were collected for hemogasometry, EIT images and hemodynamic parameters and respiratory mechanics were recorded at each stage of PEEP. During ARM, patients\' PaO2/FiO2 increased as well as increased pulmonary static compliance, associated with a decrease in pulmonary shunt, and pulmonary ventilation moving to dependent areas, mainly when 17 cmH2O or more were applied. As adverse effects were observed transient changes in hemodynamic parameters. So TIE is capable of presenting the changes in pulmonary ventilation in horse in dorsal recumbency undergoing ARM, and showed good relation to oxygenation gain and respiratory mechanics.

A Tomografia por Impedância elétrica (TIE) tem como objetivo gerar imagens da distribuição de resistividade dentro de um domínio. A TIE injeta correntes em eletrodos alocados na fronteira do domínio e mede potenciais elétricos através dos mesmos eletrodos. A TIE é considerada um problema inverso, não-linear e mal posto. Atualmente, para gerar uma solução do problema inverso, existem duas classes de algoritmos para estimar a distribuição de resistividade no interior do domínio, os que estimam variações da distribuição de resistividade do domínio e os absolutos, que estimam a distribuição de resistividade. Variações da distribuição de resistividade são o resultado da solução de um sistema linear do tipo Ax = b. O objetivo do presente trabalho é avaliar o desempenho da Programação Linear (PL) na solução do sistema linear, avaliar o algoritmo quanto a propaga- ção de erros numéricos e avaliar os efeitos de restringir o espaço solução através de restrições de PL. Os efeitos do uso de Programação Linear é avaliado tanto em métodos que geram imagens de diferenças, como o Matriz de Sensibilidade, como em métodos absolutos, como o Gauss-Newton. Mostra-se neste trabalho que o uso da PL diminui o erro numérico propagado quando comparado ao uso do algoritmo LU Decomposition. Resulta também que reduzir o espaço solução, diretamente através de restrições de PL, melhora a resolução em resistividade e a resolução espacial da imagem quando comparado com o uso de LU Decomposition. / Electrical impedance tomography (EIT) generates images of the resistivity distribution of a domain. The EIT method inject currents through electrodes placed on the boundary of the domain and measures electric potentials through the same electrodes. EIT is considered an inverse problem, non-linear and ill-conditioned. There are two classes of algorithms to estimate the resistivity distribution inside the domain, difference images algorithms, which estimate resistivity distribution variations, and absolute images algorithms, which estimate the resistivity distribution. Resistivity distribution variations are the solution of a linear system, say Ax = b. In this work, the main objective is to evaluate the performance of Linear Programming (LP) solving an EIT linear system from the point of view of the numerical error propagation and the ability to constrain the solution space. The impact of using LP to solve an EIT linear system is evaluated on a difference image algorithm and on an absolute algorithm. This work shows that the use of LP diminishes the numerical error propagation compared to LU Decomposition. It is also shown that constraining the solution space through LP improves the resistivity resolution and the spatial resolution of the images when compared to LU Decomposition.