Real-time three-dimensional electrical impedance imaging

Electrical impedance tomography is a technology for producing images of int ernal body structures based upon electrical measurements made from electrod es on the body surface. Typically a single plane of electrodes is used, see king to reconstruct a cross-section of the body. Yet the majority of image reconstruction algorithms ignore the three-dimensional (3D) characteristics of the current Row in the body. Actually, a substantial amount of current Rows out of the electrode plane, creating distortions in the resulting imag es. This paper describes a reconstruction algorithm, ToDLeR, for solving a linearized 3D inverse problem in impedance imaging. The algorithm models th e body as a homogeneous cylinder and accounts for the 3D current flow in th e body by analytically solving for the current Row from one or more layers of electrodes on the surface of the cylinder. The algorithm was implemented on the ACT3 real-time imaging system and data were collected From a 3D tes t phantom using one, two and four layers of electrodes. By using multiple p lanes of electrodes, improved accuracy in any particular electrode plane wa s obtained, with decreased sensitivity to out-of-plane objects. A cylindric al target located vertically more than 8 cm below a single layer of 16 elec trodes, and positioned radially midway between the centre and the boundary, produced an image that had 35% of the value obtained when the target was i n the electrode plane. By adding an additional layer of 16 electrodes below the first electrode plane, and using 3D current patterns, this artefact wa s reduced to less than 10% of the peak value. We conclude that the 3D algor ithm, used with multiple planes of electrodes, reduces the distortions from out-of-plane structures in the body.