Email: kaot@rpi.edu
CompanyName: Rensselaer Polytechnic Institute
Country: USA
Abstract Title:
Distingishability of Inhomogeneities Using Planar Electrode Arrays and
Different Patterns of Applied Current and Voltage in EIT
Tzu-Jen Kao1, J.C. Newell1, and G. J. Saulnier2 and D. Isaacson3
Rensselaer Polytechnic Institute Troy, NY 12180
1Department of Biomedical Engineering, 2Department of Electrical, Computer and
Systems Engineering, 3Department of Mathematical Sciences
Abstract
Three methods are presently used for breast cancer diagnosis by Electrical
Impedance Tomography (EIT). One applies a constant voltage to a flat array of
electrodes on the body and measures the resulting currents at each of several
electrodes. Another method applies multiple patterns of current and measures
the resulting voltages. The third uses voltage sources to apply specified
current levels, and then analyzes the voltages that were required.
The purpose of the present study was to compare the distinguishability
obtainable by these three methods. We used various current patterns with small
and large conducting and insulating targets placed at several different depths
and positions relative to a flat electrode array. We also compared the single
current sources as used by Korjenevsky et al. [1] and the voltage sources used
by the T-SCAN system [2] with these current patterns. We made these comparisons
using several sizes and numbers of electrodes.
A rectangular saline filled tank containing an array of stainless steel
electrodes was used as the conductive medium. The Adaptive Current Tomograph
III system [3] was used as the impedance imaging device. In some studies, a
second array was introduced at the opposite end of the tank. We studied the
distinguishability of different inhomogeneities by applying optimal currents [4]
and measuring voltages. We then compared these results with those obtained by
applying a uniform voltage at all electrodes and measuring the currents at each
electrode. A third case consisted of applying currents to one electrode at a
time, and measuring voltages at all electrodes. The results are interpreted in
terms of the distinguishability defined by Isaacson [4]. The optimal patterns
allowed one to detect inhomogeneities almost twice as far from the electrodes as
was possible with the other patterns.
References:
1. A Korjenevsky, V. Cherepenin and V. Kornienko "Electric Mammograph with 3D
visualization" 1st EPSRC Engineering Network meeting. London, 1999.
2. www.transscan.co.il TransScan T-Scan 2000 - P970033, United States Food and
Drug Administration, April 16, 1999.
http://www.fda.gov/cdrh/pdf/p970033.htm
3. Edic, P.M., G.J. Saulnier, J.C. Newell and D. Isaacson. "A real-time
electrical impedance tomograph " IEEE Trans. Biomed. Eng. 42(9): 849-859, 1995.
4 Isaacson, D. Distinguishability of Conductivities by Electric Current
Computed Tomography. IEEE Trans Med Imaging MI-5 (2): 92-95, 1986.