Image reconstruction algorithms for electrical capacitance tomography: State of the art

Image reconstruction for electrical capacitance tomography (ECT) seeks to calculate the permittivity distribution from capacitance measurements. This paper reviews existing ECT image reconstruction algorithms, including linear back projection (LBP), singular value decomposition (SVD), Tikhonov regularisation, Newton-Raphson, steepest descent, Landweber iteration, the algebraic reconstruction technique (ART), the simultaneous iterative reconstruction technique (SIRT), and model-based reconstruction. The most commonly used ECT image reconstruction algorithms, LBP, SVD, Tikhonov regularization, iterative Tikhonov, and projected Landweber iteration, were evaluated using simulations and experimental data. The evaluation results are compared in terms of capacitance error, image error, correlation coefficient, and the time required for image reconstruction. Future possibilities on ECT image reconstruction algorithms are also discussed.