Design and performance of the UCLH mark 1b 64 channel electrical impedance tomography (EIT) system, optimized for...

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Neuroscience

Background:

• Portable Electrical Impedance Tomography (EIT) systems are crucial for non-invasive brain function imaging.
• Existing systems may have limitations in portability and flexibility for ambulant recordings.
• Scalp electrode-based EIT offers a promising approach for monitoring brain activity.

Purpose of the Study:

• To introduce and evaluate the performance of the UCLH Mark 1b, a novel portable EIT system.
• To assess the system's capability for imaging brain function using scalp electrodes.
• To determine the system's suitability for clinical trials in neurological conditions.

Main Methods:

• The UCLH Mark 1b system utilizes a single impedance-measuring circuit and multiplexer for flexible electrode addressing.
• It operates in a low-frequency band (225 Hz - 77 kHz) suitable for detecting brain activity-related impedance changes.
• Performance was validated using resistor-capacitor networks and saline tanks containing a human skull.

Main Results:

• The system achieved a signal-to-noise ratio better than 50 dB and a maximum reciprocity error below 10%.
• Common-mode rejection ratio (CMMR) exceeded 80 dB at 38 kHz.
• The system successfully localized a 12% impedance increase caused by a 20 mm sponge in imaging tests.

Conclusions:

• The UCLH Mark 1b system demonstrates adequate performance for imaging clinically relevant impedance changes in the brain.
• The portable design facilitates recordings in ambulant subjects, expanding EIT applications.
• Clinical trials are underway to image conditions like epilepsy and stroke using this EIT system.