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Direct EIT Jacobian calculations for conductivity change and electrode movement

Summary: Direct EIT Jacobian calculations for conductivity
change and electrode movement
Camille G´omez-Laberge and Andy Adler
Systems and Computer Engineering, Carleton University, Ottawa, Canada
E-mail: adler@sce.carleton.ca
Abstract. Electrical Impedance Tomography (EIT) is very sensitive to deformations
of the medium boundary shape. For lung imaging, breathing and posture changes
move the electrodes and change the chest shape, resulting in image artefacts. Several
approaches have been proposed to improve the reconstructed images; most methods
reconstruct both boundary deformation and conductivity change from the measured
data. These techniques require calculation of the "movement Jacobian" reflecting
measurement changes due to boundary deformation. Previous papers have calculated
this Jacobian using perturbation techniques, which are slow (requiring multiple
solutions of the forward problem) and become inaccurate with increasing finite element
model size. This effect has limited reconstruction algorithms for deformable media to
mostly 2D.
To address this problem, we propose a direct method to calculate the Jacobian,
based on a formulation of the derivatives of the finite element system matrix with
respect to geometry changes. An illustrative example of these calculations is given
as well as a comparison between the proposed method and a perturbation method.


Source: Adler, Andy - Department of Systems and Computer Engineering, Carleton University


Collections: Computer Technologies and Information Sciences