A Cole phantom for EIT

Abstract

A phantom was designed for testing and comparing multifrequency EIT data collection systems. The phantom simulates a cylinder of homogeneous conductor with 16 drive and 16 receive electrodes interleaved. Combinations of resistors and capacitors were used to simulate the complex impedance, Z*, of a typical tissue in the frequency range 8-2048 kHz obeying the Cole equation Z*=Z_infinity +(Z₀-Z_infinity )/(1+(if/f_c)^{(1- alpha )}). Where Z* is the complex impedance at frequency f, Z₀ and Z_infinity are the limiting values of impedance at low and high frequencies, f_c is the characteristic frequency and alpha is a constant. A practical phantom was then constructed on which four different sets of spectroscopic parameters could be selected: (i) alpha =0.20, f_c=150 kHz, Z₀/Z_infinity =3.31; (ii) alpha =0, f_c=273 kHz, Z₀/Z_infinity =2.64; (iii) alpha =0, f_c=71.1 kHz, Z₀/Z_infinity =1.36 and (iv) Z₀/Z_infinity =1.00 with no dispersion.