Electrical impedance tomography using code division multiplexing

Electrical Impedance Tomography (EIT) is an imaging modality that discriminates among impedances of internal constituents of objects to create a map or image of such contents. EIT has been dominated by the use of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM) as methods of achieving orthogonal injection of excitation signals. Recently, an alternative: Code Division Multiplexing (CDM) has been proposed for the same purpose. To the authors knowledge no fully functional system or simulation platform using simultaneous injection of CDM currents has been reported. In this paper we formulate and simulate a fully functional pseudorandom code driven EIT system with 16 excitation and 16 separate measurement electrodes. In the work we verify the use of Gold codes in CDM as a multiplexing modality for EIT. The simulations are performed using the Electrical Impedance and Diffuse Optics Reconstruction Software (EIDORS). The results of this study show that: (a) Gold codes can successfully be used, in simultaneous injection as excitation current patterns in a Code Division Multiplexed EIT system. A simple image processing approach is proposed, to extract measures of reconstructed image quality. This method does not require the raw reconstruction data but uses the created images.