Issues in Electrical Impedance Imaging

• Authors: Margaret Cheney;David Isaacson
• Venue: IEEE Computational Science & Engineering
• Year: 1995

Though electrocardiograms save lives every day, the information they give us is still much less than the complete picture we would like to have. One important reason for this is that we lack detailed knowledge of the complex electrical conductivity and permittivity distribution in a patient's body between the heart, where the signal is produced, and the surface of the chest, where we measure it. If we knew these parameters, we could tell more accurately what is going on inside.This is where Cheney and Isaacson's work comes in. Their research is not on heart monitoring, but on how to map electrical impedance accurately with a tomographic measurement setup based on electromagnetic principles. This is a nonlinear, ill-posed, inverse computational problem, typical of the challenges of parameter estimation in many disciplines, with some additional complications. For instance, to be medically useful this sort of mapping often has to be done very fast. Moreover, the impedance map changes in time; in fact, it changes with each heartbeat and with each breath in and out. The authors describe the formulation of the problem, the algorithms they use, and some aspects considered in designing the portable PC-based impedance imaging unit their team has developed, which shows promise for further developing into a clinically useful instrument for real-time monitoring. Such a capability has potential applications to a host of medical technologies, heart-related and otherwise, and might also help in mineral location and nondestructive testing, among other commercial uses.