Multi-channel Electrical Impedance Tomography with Field Programmable Gate Array

Abstract

In this thesis a digital system for biomedical applications is proposed. A framework synthesizing analog waveforms and digital processing of measured analog signals is implemented. This is relevant for biomedical instrumentation because electrical signals in tissue are often small and noisy. Field Programmable Gate Array (FPGA) is chosen for this role, and the task is performed by generating reference signals with an implemented Direct Digital Synthesizer (DDS), the Digital Signal Processing (DSP) on the sampled data were done with a Lock-In Amplifier (LIA) and Coordination Rotational Digital Computer (CORDIC). Because of this the system is able to calculate the real and imaginary parts of a measured system, as well as the phase difference and magnitude. These data are written to files for use on the computer. Examples of application include, but are not limited to Electrical Impedance Tomography (EIT), impedance measurements over fixed frequencies and frequency sweeps. EIT is a non-invasive, non-ionized form of imaging, typically used in medical medical applications, and is often used in intensive care units. For EIT imaging, the open source EIDORS libraries can be used.