NaCl doping and the conductivity of agar phantoms

A recipe for manipulating the conductivity of agar impedance-imaging phantoms through their NaCl (salt) content is reexamined. The conductivities at frequencies 100 kHz and below are characterized for phantoms created with the recipe. The data are compared against the recipe's predictive formula for conductivity as a function of salt content. Based on analysis of the data a modified version of the conductivity formula is generated. The modified predictive formula better approximates the observed NaCl dependence of conductivity in phantoms with salt concentrations under 0.1 M. The experimental data also provide verification for the asymptotic dependence of contact impedance on frequency and phantom conductivity. The results of these experiments will be helpful in better constructing agar phantoms to electrical specifications for future impedance-imaging experiments.