Low-cost functional imaging-Electrical Impedance Tomography

Functional imaging has been identified by the major medical research funding bodies in the United Kingdom as a growing area which merits research funding. This area includes techniques such as Positron Emission Tomography, Scintigraphy, Ultrasound and Biomagnetic imaging. High resolution techniques such as CT and MRI give detailed anatomical images, but functional imaging techniques, whilst having poorer spatial resolution, have the ability to image organ function. The imaging of organ function can be of much greater value to a clinician than an anatomical image. Electrical Impedance Imaging has been developed over the past ten years and uses an array of electrodes placed around a body segment to produce an image of tissue impedance. The technique has been used in clinical trials in various areas such as the measurement of gastric function and pulmonary monitoring. It is a low cost technique which may well be particularly appropriate to use in developing countries. Recent research work in Sheffield on the technique has extended the possible uses of EIT by using multi-frequency measurements to produce spectroscopic images (EITS). These images enable tissue to be characterised in terms of extracellular spaces, intracellular spaces and relaxation frequencies and so enable conditions such as lung water to be monitored. The paper presents the development of the technique of Electrical Impedance Spectroscopy (EITS) and discusses the appropriateness of its use as an affordable technology in developing countries