British Technology Group Limited

University of Sheffield

David C Barber

Brian Hilton Brown

Francis Joseph McArdle

Ian Leslie Freeston

Investigation of a body

Image reconstruction

Electrical impedance tomography

Applied potential tomography

Real-time electrical impedance tomography system

A method of determining the external shape of a body comprises placing a plurality of electrodes adjacent the surface at spaced intervals around the body, causing currents to flow in the body by applying an electrical potential between pairs of electrodes in turn, measuring potentials between other pairs of electrodes, relating the measured potentials to the distances between the corresponding points of current introduction and of potential measurement, and determining electrode positions consistent with these distances, which electrode positions define the external shape of the body.

Tomographic images (I.sub.1 and I.sub.2) of a body are constructed by placing a plurality of surface electrodes (1 to 16) at spaced intervals on the body (M), causing currents to flow in the body, and measuring the potential between pairs of electrodes, calculating the potential in each case on the assumption that the body consists of one uniform medium, plotting the isopotentials corresponding to the calculated results to create a uniform image of the body, obtaining the ratio between the measured potential and the calculated potential in each case, and modifying the image in accordance with the respective ratios by increasing the impedance along an isopotential in proportion to a ratio greater than unity or decreasing the impedance in proportion to a ratio less than unity. The calculations of potentials and the obtaining of ratios are carried out using a computer and the plotting of the isopotentials is carried out by a visual display unit (VDU) and/or a print-out unit run off the computer. An additional method is provided for indicating a change of state in the body. This method includes the step of determining ratios between initial and subsequent measured actual potentials between electrodes.

Tomography

Growing community of inventors

Sheffield, United Kingdom

David C Barber