Applied potential tomography: possible clinical applications

Abstract

Applied potential tomography (APT) or electrical impedance imaging has received considerable attention during the past few years and some in vivo images have been produced. This paper reviews the current situation in terms of what in vivo results have been and are likely to be obtained in the near future. Both static and dynamic imaging are possible and these two areas are dealt with separately. Features of the existing in vivo imaging system are good tissue contrast, high-speed data collection, good sensitivity to resistivity changes, low spatial resolution, low cost and no known hazard. It is concluded that the most promising way forward to clinical application in the short term is to use dynamic as opposed to static imaging. An example of lung imaging is shown and the application to measuring regional ventilation and pulmonary oedema is discussed. Use of APT for the detection of intraventricular bleeding in neonates is discussed as is the proven ability to study gastric physiology by imaging resistivity distribution changes following the ingestion of conducting or insulating fluids. Other areas of possible application which are considered are blood flow measurement, cell counting, measurement of lean-fat ratios and the detection of soft tissue lesions.

Changes in lung volume and ventilation following transition from invasive to noninvasive respiratory support and prone positioning in preterm infants

“…Second, the absence of endotracheally delivered positive airway pressure following extubation may have increased venous return to the heart. This in turn may have limited an increase in lung aeration and thus lung impedance in the ventral part of the chest, as blood has a five times lower impedance than lung tissue at expiration (23).…”

Two-dimensional impedance imaging of cell migration and epithelial stratification

“…10 As suggested by Brown et al in 1985, it should be possible to obtain images with a resolution on the order of a few microns by using sufficiently small electrodes. 11 Recently, there have indeed been reports on miniaturized EIT systems, [12][13][14] but the smallest object presented so far is a 80 mm metal wire. Given that the subject has been under investigation for several decades, it is somewhat surprising that there have not been more reports on miniaturized impedance imaging systems.…”

Electrical resistance tomography for monitoring the infiltration of water into a pavement section

“…For example, Dines and Lytle [1981] used a circuit analysis approach to generate estimates of the conductivity using an iterative process on network equations that are linearized in the unknown conductance variables. Other early approaches met with varying degrees of success (e.g., Henderson and Webster [1978], Pelton et al [1978], Nariida and Vozoof [1984], Tripp et al, [1984], Kohn and Vogelius [1987], Wexler et al [1985], Brown et al [1985], Isaacson [1986], Yorkey [1986], Yorkey et al, [1987]). Recent work by Berryman and Kohn [1990] shows that variational constraints can be used to stabilize such inversions.…”