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In-vivo human head conductivity estimation by SEEG and EEG recorded in simultaneous with intracerebral electrical stimulation

Abstract : EEG source localization is becoming an important tool for treating epileptic patients by localizing the epileptogenic zones before performing a resection surgery. Given a forward head model, EEG source localization is performed by solving the inverse problem. The forward head model is a biophysical model which describes the electrical distribution in the human head. When considering the propagation as the only way for the current distribution to move in the head, the focus is directed primarily on two parameters for having an accurate forward head model. These parameters are: the geometry of the head model and the conductivity value of each compartment of the head model. Due to the recent advances in computers and imaging techniques (like MRI and CT), it is possible to generate human head models that represent with a high accuracy the geometry of the real head. However, there is still an argument about the conductivity values and the method by which it should be estimated. In literature, the common values for conductivities come mostly from in-vitro experiments. In this work we are performing in-vivo conductivity estimation by considering the data of three epileptic patients. This data consists of MR images and CT scans for building a five-compartment FEM head model for each patient along with SEEG and EEG recordings that were acquired in simultaneous with intracerebral electrical stimulation (IES). The originality of this work lies in evaluating the performance of in-vivo conductivity estimation by EEG and/or SEEG measurements in function of different spatial parameters and locations of the IES. The following work consists of three major parts: the first part aims to determine the most robust optimization algorithm among common algorithms for optimizing the forward head model. The objective of the second part is to analyze the sensitivity of the conductivity values given different conditions on stimulation position, measurement positions and number of compartments. While in the final part, the conductivities of an isotropic and homogeneous five-compartment FEM head model were estimated with previously selected parameters for three drug-resistant epileptic patients. Finally the effect of changing the stimulation frequency on the estimated conductivities was determined
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  • HAL Id : tel-01709247, version 1

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Hamza Fawzi Altakroury. In-vivo human head conductivity estimation by SEEG and EEG recorded in simultaneous with intracerebral electrical stimulation. Automatic. Université de Lorraine, 2017. English. ⟨NNT : 2017LORR0304⟩. ⟨tel-01709247⟩

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