Electrical capacitance tomography (ECT) is a method for determination of the dielectric permittivity distribution in the interior of an object from external capacitance measurements. It is a close relative of electrical impedance tomography and is proposed as a method for industrial process monitoring, although it has yet to see widespread use. Potential applications include the measurement of flow of fluids in pipes and measurement of the concentration of one fluid in another, or the distribution of a solid in a fluid. Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... Electrical Impedance Tomography (EIT), is a medical imaging technique in which an image of the conductivity or permittivity of part of the body is inferred from surface electrical measurements. ...

Although capacitance sensing methods were in widespread use the idea of using capacitance measuremnet to form images is attributed to Maurice Beck and co-workers at UMIST in the 1980s. UMIST Main Building on Whitworth Street The University of Manchester Institute of Science and Technology (UMIST) was a university based in the centre of the city of Manchester in England (, ). It specialised in technical and scientific subjects and was a major centre for research. ... The 1980s refers to the years of 1980 to 1989. ...

Although usually called tomography, the technique differs from conventional tomographic methods, in which high resolution images are formed of slices of a material. The measurement electrodes, which are metalic plates, must be sufficiently large to give a measureable change in capactiance. This measns that very few electrodes are used and eight or twelve electrodes is common. An N-eleectrode system can only provide N(N-1)/2 independent measurements. This means that the technique is limited to producing very low resolution images of approximate slices. However, ECT is fast, and relatively inexpensive. Tomography is imaging by sections or sectioning. ...

References

• S M Huang, A Plaskowski, C G Xie and M S Beck, Capacitance-based tomographic flow imaging system, Electronics Letters, 24 (7), 1988, pp 418-419.
• W Q Yang, Hardware design of electrical capacitance tomography systems, Meas. Sci. Technol., 7 (3), 1996, pp 225-232
• M Soleimani, W R B Lionheart, Nonlinear image reconstruction in electrical capacitance tomography using experimental data, Meas. Sci. Technol., 16, 2005, pp 1987-1996
• W Q Yang and L H Peng, Image reconstruction algorithms for electrical capacitance tomography, Meas. Sci. Technol., 14, 2003, pp R1-R13 (invited review article)