Quantification in impedance imaging.

Applied potential tomography (APT) is a technique for producing tomographic images of the distribution of electrical resistivity within electrically conducting objects. Human tissues exhibit a wide range of resistivities and images of resistivity within the body should show good contrast. The data used to reconstruct such images are measurements of the voltages developed on the surface of the object when various patterns of current are passed through the object. The reconstruction problem is much harder than for other tomographic modalities but we have shown that provided we restrict ourselves to imaging changes in resistivity, it is possible to reconstruct images from data collected in vivo. We describe some possible clinical uses of the technique.