Ionic Parameters Estimation in Multi-Scale Cardiac Electrophysiology Modelling

In this work, we present an optimal control formulation for the bidomain model in order to estimate maximal conductance parameters in cardiac electrophysiology multiscale modelling. We consider a general Hodgkin-Huxley formalism to describe the ionic exchanges at the microscopic level. We treat the desired parameters as control variables in a cost function minimizing the gap between the measured and the computed transmembrane potentials. First, we establish the existence of an optimal control solution and we formally derive the optimality system. Second, we propose a strategy for solving the estimation problem for both single and multiple parameters cases. Our algorithm is based on a gradient descent method, where the gradient is obtained by solving an adjoint problem. Both the state and the adjoint problems are solved using the finite element method. Numerical simulations for single and multiple conductances estimations show the capability of this approach to identify the values of sodium, calcium and potassium ion channels conductances of the Luo Rudy phase I model

On the identification of multiple space dependent ionic parameters in cardiac electrophysiology modelling

In this paper, we consider the inverse problem of space dependent multiple ionic parameters identification in cardiac electrophysiology modelling from a set of observations. We use the monodomain system known as a state-of-the-art model in cardiac electrophysiology and we consider a general Hodgkin-Huxley formalism to describe the ionic exchanges at the microscopic level. This formalism covers many physiological transmembrane potential models including those in cardiac electrophysiology. Our main result is the proof of the uniqueness and a Lipschitz stability estimate of ion channels conductance parameters based on some observations on an arbitrary subdomain. The key idea is a Carleman estimate for a parabolic operator with multiple coefficients and an ordinary differential equation system

Ionic parameters identification of an inverse problem of strongly coupled PDE's system in cardiac electrophysiology using Carleman estimates

International audienceIn this paper, we consider an inverse problem of determining multiple ionic parameters of a 2 × 2 strongly coupled parabolic-elliptic reaction-diffusion system arising in cardiac electrophysiology modelling. We use the bidomain model coupled to an ODE system and we consider a general formalism of physiologicaly-detailed cellular membrane models to describe the ionic exchanges at the microscopic level. Our main result is the uniqueness and a Lipschitz stability estimate of the ion channels con-ductance parameters of the model using subboundary observations over an interval of time. The key ingredients are a global Carleman-type estimate with a suitable observations acting on a part of the boundary

Robust numerical algorithms based on analytic approximation for the solution of inverse problems in annular domains

See also INRIA RR-6456 (2008)International audienceWe consider the Cauchy problem of recovering both Neumann and Dirichlet data on the inner part of the boundary of an annular domain from measurements of a harmonic function on some part of the outer boundary. Using tools from complex analysis and best approximation in Hardy classes, we present a family of fast data completion algorithms which are shown to provide constructive and robust identification schemes. These are applied to the computation of an impedance or Robin coefficient and are validated by a thorough numerical study

Analytic extensions and Cauchy-type inverse problems on annular domains. I: theoretical aspects and stability results

We consider the Cauchy issue of recovering boundary values on the inner circle of a two-dimensional annulus from available overdetermined data on the outer circle, for solutions to the Laplace equation. Using tools from complex analysis, Hardy classes and approximation, we establish stability properties and error estimates, as well as a recovery scheme, illustrated by some numerical computations

On some robust algorithms for the Robin inverse problem

International audienceThe problem we are dealing with is to recover a Robin coefficient (or impedance) from measurements performed on some part of the boundary of a domain, in the framework of nondestructive testing by the means of Electric Impedance Tomography. The impedance can provide information on the location of a corroded area, as well as on the extent of the damage, which has possibly occurred on an unaccessible part of the boundary. Two different identification algorithms are presented and studied: the first one is based on a Kohn and Vogelius cost function, actually an energetic least squares one, which turns the inverse problem into an optimization one ; as for the second, it makes use of the best approximation in Hardy classes, in order to extend the Cauchy data to the unreachable part of the boundary, and then compute the Robin coefficient from these extended data. Special focus is put on the robustness with respect to noise, both from a mathematical and and numerical point of view. Some numerical experiments are eventually presented and compared.Dans ce travail nous nous sommes intéressé à un problème d’identification d’un coefficient de Robin (ou une impédence) à partir de mesures effectuées sur une certaine partie de la frontière d’un domaine. Ce problème est motivé par le contrôle non destructif des matériaux en tomographie par impédance électrique. L’impédance peut fournir des informations sur l’emplacement d’une zone de corrosion, ainsi que sur l’étendue des dommages, qui a peut-être eu lieu sur une partie inaccessible de la frontière. Deux algorithmes d’identification sont présentés et étudiés: le premier est basé sur la minimisation des fonctionnelles d’écart énergétiques, dite de Kohn et Vogelius, comme pour le second, il fait usage à l’approximation dans les classes de Hardy afin de prolonger les données de Cauchy à la partie inaccessible de la frontière, puis calculer le coefficient de Robin qui est le quotient de ces données étendues. L’accent est mis sur la robustesse par rapport au bruit, à la fois d’un point de vu mathématique et numérique. Des expériences numériques sont finalement présentées et comparées

Ionic Parameters Estimation in Multi-Scale Cardiac Electrophysiology Modelling

In this work, we present an optimal control formulation for the bidomain model in order to estimate maximal conductance parameters in cardiac electrophysiology multiscale modelling. We consider a general Hodgkin-Huxley formalism to describe the ionic exchanges at the microscopic level. We treat the desired parameters as control variables in a cost function minimizing the gap between the measured and the computed transmembrane potentials. First, we establish the existence of an optimal control solution and we formally derive the optimality system. Second, we propose a strategy for solving the estimation problem for both single and multiple parameters cases. Our algorithm is based on a gradient descent method, where the gradient is obtained by solving an adjoint problem. Both the state and the adjoint problems are solved using the finite element method. Numerical simulations for single and multiple conductances estimations show the capability of this approach to identify the values of sodium, calcium and potassium ion channels conductances of the Luo Rudy phase I model

Numerical Investigation on the usefulness of Proper Orthogonal Decomposition method in cardiac electrophysiology

Numerical simulation of cardiac electrophysiology is very time consuming. Reduced order method have been recently used in different fields including cardiac electro- physiology. In this paper we use a reduced order method based on the proper orthogonal decomposition (POD), and we propose to evaluate the accuracy of this method while changing different parameters in the model. To describe the propagation of the action potential in the myocardium, we use the monodomain model which is a reaction diffusion PDE system coupled to a dynamic system of ODEs representing the time evolution of the electrophysiology in the cell membrane. We build the reduced order model using a set of parameters, afterwards, we evaluate the accuracy of the reduced model while changing the parameters of the model. We numerically analyze the sensitivity of the reduced order method to the model parameters including the change of the whole ionic model

Stability results for the parameter identification inverse problem in cardiac electrophysiology

The aim of this work is to establish stability estimates for the parameter identification problem in cardiac electrophys-iology modeling. The propagation of the electrical wave in the heart is described by the monodomain equation. The model consists of a reaction-diffusion non linear equation coupled to an ODE system representing the electrical activity of the cell membrane