Signal conditioning using logarithmic amplifier for biomedical applications of electrical impedance tomography

Area of Science:

• Biomedical Engineering
• Electrical Engineering
• Medical Imaging

Background:

• Electrical Impedance Tomography (EIT) systems require high-resolution analog-to-digital conversion (ADC) cards due to the wide dynamic range of measured signals (µV to mV).
• Signal conditioning is crucial for optimizing EIT system performance, particularly in low-cost implementations.

Purpose of the Study:

• To investigate the efficacy of a logarithmic amplifier in enhancing the spatial resolution (RES) of a low-cost EIT system.
• To evaluate the performance of a logarithmic amplifier compared to a linear amplifier for signal conditioning in EIT.

Main Methods:

• Designed and implemented two EIT systems: one utilizing a linear amplifier and another a logarithmic amplifier.
• Conducted phantom experiments with low current injection to assess signal-to-noise ratio (SNR), image quality, and detection limits.

Main Results:

• The logarithmic amplifier-based EIT system demonstrated a 4 dB increase in average SNR.
• Improvements were observed in spatial resolution (RES) and contrast-to-noise ratio.
• The system achieved detection of a minimum object radius of 0.25 cm and a minimum conductivity change of 11%.

Conclusions:

• Logarithmic amplifier-based signal conditioning is a viable and promising technique for improving the spatial resolution of low-cost EIT systems.
• This approach enables the use of lower-resolution ADC cards, contributing to cost-effectiveness.
• The findings suggest a significant advancement in accessible EIT technology.