Generalized Optimal Current Patterns and Electrical Safety in EIT

Abstract

There are a number of constraints which limit the current and voltages which can be applied on a multiple drive electrical imaging system. One obvious constraint is to limit the maximum Ohmic power dissipated in the body. Current patterns optimising distinguishability with respect to this constraint are singular functions of the difference of transconductance matrices with respect to the power norm. (the optimal currents of Isaacson). If one constrains the total current ($L^1$ norm) the optimal patterns are pair drives. On the other hand if one constrains the maximum current on each drive electrode (an $L^\infty$ norm), the optimal patterns have each drive channel set to the maximum source or sink current value. In this paper we consider appropriate safety constraints and discuss how to find the optimal current patterns with those constraints.