Design of a Wearable Parallel Electrical Impedance Imaging System for Healthcare

TL;DR

A wireless wearable Electrical Impedance Tomography (EIT) system has been developed utilizing the AD5933 chip to achieve real-time imaging of lung respiration, demonstrating that this portable EIT system can accurately measure biological tissues with high precision and low cost.

Abstract

A wireless wearable Electrical Impedance Tomography (EIT) system has been developed utilizing the AD5933 chip to achieve real-time imaging of lung respiration. The system employs a voltage excitation method tailored to human impedance characteristics, injecting current by applying a known voltage and measuring the resulting current through the body. Additionally, specific measures have been implemented to effectively suppress signal oscillations and leakage currents caused by parasitic capacitances. To enhance data acquisition speed, the system employs five parallel AD5933 units, with multiple techniques implemented to ensure high synchronization during simultaneous measurements. Performance testing shows that the system achieves a signal-to-noise ratio greater than 50 dB, a relative standard deviation below 0.3%, and a reciprocity error under 0.8%. Imaging experiments using a water tank phantom, human lungs during breathing, and a resting human calf further demonstrate that this portable EIT system can accurately measure biological tissues with high precision and low cost.

Figures (16)

• Figure 1: Overview of the EIT system: (a) Block Diagram of Two-Terminal Serial Impedance Measurement; (b) Block Diagram of Four-Terminal Parallel Impedance Measurement; (c) photograph of the system prototype.
• Figure 2: Schematic Diagram of the Voltage Excitation Circuit.
• Figure 3: Schematic Diagram of the I–V Conversion Circuit.
• Figure 4: Equivalent Circuit Model of the I–V Conversion Circuit with Parasitic Capacitance.
• Figure 5: Equivalent Model of the Second Stage of the Voltage Excitation Circuit with Capacitive Load.