What are the main problems in obtaining a permittivity image from the capacitance measurements?
The number of pixels in the image usually exceeds the number of capacitance measurements by several orders of magnitude. Unfortunately, it is not possible to obtain a unique solution for each image pixel when the number of pixels in the image exceeds the number of capacitance measurements. Furthermore, image distortion can occur because ECT is an inherently soft-field imaging method (the electric field is distorted by the material distribution inside the sensor).
