The project provides a simple and reproducible methodology for the universal evaluation of the performance of electrical impedance tomography (EIT) systems using reconstructed images.

EIT is an impedance measurement technique that uses the tomography principle to reconstruct an image that illustrates the inner impedance distribution of the subject under test (SUT), it's basic working principle is as shown below:

Based on objective full referencing (FR), this evaluation method provides a visually distinguishable hot colormap and quantitative image quality metrics. It addresses the issues where common electrical parameters used in EIT hardware evaluation are not directly related to the quality of EIT images.

P_system is the system power consumption

f is the system EIT operating frequency

Global FR is the quantitative image quality metric

Frame Rate is the system image frame per second

Ensuring a fair evaluation and comparison of EIT system performance requires using identical:

• SUT that can produce a reference image (ground truth) while capable of being measured by hardware;
• Reconstruction software (inverse problem solver);
• FoM factor for evaluation.

As an imaging system, the comparison should be ultimately demonstrated in terms of an image quality factor, and to be widely adopted, the method should be simple and reproducible.

For hardware system evaluation, a resistive phantom is used and is shown below:

By skipping electrodes, this phantom can be used for 8, 16, or 32 electrode systems. 16 electrode EIT system was chosen as an illustrative example here.

The 16 electrode ideal dataset for the reference image (ground truth) was generated through simulation using the resistive phantom with adjacent EIT scan, the two X resistive elements was toggled between 68.1 Ω and 0 Ω for homogeneous and inhomogeneous datasets for EIT differential imaging.

The 16 electrode ground truth image datasets are provided in sample_data.mat as ref (inhomogeneous) and data (homogeneous).

The reconstruction software runs on MATLAB and includes (in codeFiles):

1. eidors-v3.10-ng.zip

2. FR_FOM_FORMAT.m

3. sample_data.mat includes REF_Data (example of measured inhomogeneous datasets) and EIT_Data_store (example of 50 frames of measured homogeneous datasets) with ref (inhomogeneous) and data (homogeneous) obtained through resistive phantom simulation as the ground truth for comparison.

Put FR_FOM_FORMAT.m and unzipped eidors-v3.10-ng into one folder and load the sample_data.mat. For details on how to use EIDORS or to download the latest version please refers to EIDORS.

Run the FR_FOM_FORMAT.m file to generate the FRx plot and the Global FR and ROI FR of the test EIT system. The Global FR can be used to compute the new image-based EIT FoM shown in the equation before.

To evaluate e.g. a 16-electrode EIT system, keep ref and data as the ground truth, and replace REF_Data and EIT_Data_store with datasets measured from the resistive phantom using the evaluating system.

Please refer to the paper below for more details: “An Imaged-Based Method for Universal Performance Evaluation of Electrical Impedance Tomography Systems,” in IEEE Transactions on Biomedical Circuits and Systems, 2021

The EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software) is a repository of free to use software algorithms, contributed by the EIT research community, designed to run on MATLAB.

The 32-electrode resistive phantom was designed by Swisstom AG (now Sentec AG, Switzerland)