A Portable, Low-Cost, and Open-Source Electrical Impedance Tomography System with a Modular Analog Front-End Based on STM32 and AD5933

Authors:
Preprint
Publisher website
Google Scholar
Abstract
Electrical impedance tomography (EIT) is a non-invasive, and radiation-free medical imaging technique. However, the high cost and complexity of commercial devices limit their widespread accessibility. This paper presents a portable, low-cost (< $100), open-source 16-electrode EIT hardware based on the AD5933 impedance converter and an STM32F407VGT6 microcontroller. Its highly modular analog front-end allows users to conveniently select between Load-in-the-Loop or Mirrored Howland Voltage-Controlled Current Source (VCCS) topologies, and AD620 or INA118P instrumentation amplifiers. Leveraging the STM32's computational efficiency, the system employs an adjacent pattern to rapidly acquire 208 independent boundary voltage measurements in 4 seconds per frame. Hardware validation demonstrated excellent signal stability, yielding an average Signal-to-Noise Ratio (SNR) of 35.8 dB and measurement repeatability less than 0.65 [[EQUATION]]. Experimental tests were conducted using a custom 3D-printed saline phantom containing non-conductive anomalies. The collected data were successfully reconstructed into 2D images utilizing the Python-based pyEIT framework, achieving a high Structural Similarity Index Measure (SSIM) of 0.92. Relying on free, open-source applications across the software, this easily replicable system provides a robust, versatile platform for EIT research and education.