Multi-frequency EIT hardware system based on DSP

An open-source and easily replicable hardware for Electrical Impedance Tomography

Electrical Impedance Tomography (EIT) is a powerful imaging tool for investigating electrical properties of tissues such as that of human bodies. The cheap, harmless and portable nature of this tool has made EIT a popular choice in many biomedical applications. However, performing EIT requires strong development at both hardware and software levels. In particular, performing in-lab experiences remains a challenge due to the cost of commercially available devices or the complexity of systems proposed in scientific literature. In this paper, an efficient and easily replicable EIT hardware is presented. This hardware was developed with the objective of making EIT accessible to as many people as possible. It has been designed for operating frequencies between 1 kHz and 50 kHz, and can be used for in-lab validation of proof of concept. Special care has been paid to the choice of components in order to optimize the performance versus cost ratio. Also, the overall footprint has been reduced by using recent and up-to-date integrated circuits. In particular, the use of a lock-in amplifier is a compact solution that allows both narrow-band filtering of the signal and provides an easily quantifiable DC signal at the output. Circuit schematics as well as manufacturing files are shared so that understanding, replication and improvement of circuits are facilitated. Fabrication and usage procedures are given as well. At last, the proposed hardware is experimentally tested and validated first by comparing experimental data to simulations, then by reconstructing an inclusion in biological tissues.

A 128-electrode three dimensional electrical impedance tomography system

Electrical impedance tomography (EIT) is a new functional imaging technique. This paper presents the development of a new electrical impedance tomography system with 128 electrodes for impedance change detection and 3D imaging of the human thorax. The system consists of several modules, including multi-frequency current source, driving, measuring, data acquisition, and controlling and signal processing modules. A high speed digital signal processor (DSP) is used as the controller. The 64 driving electrodes and 64 measuring electrodes are positioned uniformly in four planes around the surface of a cylindrical phantom filled with a saline solution and objects of varying conductivities. The performance has been tested, and these preliminary experiments demonstrate the feasibility this system.

To detect lung ventilation with multi-frequency EIT system

The paper presents an EIT system based on the DDS AD9852 which could provide a multi-frequency current source and fast data acquisition. It has been used in monitoring human lung ventilation by a series of differential images. Experiments were performed successfully. The results show that the multi-frequency EIT system is reasonable, consistent and extendable. It is shown to be a suitable and reliable method of imaging human lung ventilation and the EIT technique has the potential to become a useful tool for monitoring respiration function.