Information retrieval by electrical capacitance tomography: Evaluation of an iterative algorithm and the importance of boundary conditions

Empirical performance of a newly developed iterative image reconstruction algorithm for electrical capacitance tomography (ECT) has been assessed by the use of various phantoms. It is based on the retrieval of information relating to the gross features of each phantom, rather than er of each individual pixel. Some practical limitations of the present algorithm have been identified. It has been found experimentally that the number of independent information elements retrieved approaches the number of independent capacitance measurements. Analysis of electrostatic boundary conditions for ECT is also presented, indicating a large number of physical constraints for image reconstruction, in addition to the capacitance measurements. It is suggested that the iterative algorithm carries out implicit regularisation with those constraints, and that the information content of ECT images could be much larger than previously suggested. An alternative measurement protocol is proposed to enhance further the information content.