PhD Thesis Defense: Arun J. Rao

Wednesday, February 27, 2019, 1:00–3:00pm

Rm. 105, Cummings Hall

“Design of Small Form Factor Electrical Impedance Tomography System”

Abstract

Electrical Impedance Tomography (EIT) is an imaging modality that incorporates the bio-impedances of the tissue to provide a spatial mapping of the region being probed. Using sinusoidal current interrogation, it is possible to determine the cancerous or benign nature of tissues due to differences in conductivity. Advantages of an EIT system is its relatively smaller size and inexpensive cost compared to Magnetic Resonance Imaging (MRI) or Computerized Tomography (CT). EIT is also non-invasive and non-radiative, which are desirable for continuous imaging and tele-monitoring.

Traditional bench-top EIT systems are power intensive, bulky and unsuitable for continuous imaging. Longer cables from electrodes to hardware degrade high frequency behavior due to increased parasitics and affect measurement accuracy. State-of-the-art EIT systems incorporating Application Specific Integrated Circuits (ASICs) do not achieve the necessary SNR or bandwidth of operation necessary for high frequency imaging.

In this work, a fully functional small form factor EIT system using ASICs is presented, which reduces form-factor and consumes less power than bench-top EIT systems. A CMOS wide-band current driver was designed, and measured operating up to 10 MHz, while delivering 1.2 mA current with less than 1% harmonic distortion. A four channel ASIC was fabricated in CMOS 0.18-μm technology, and incorporated the wide-band current driver, Instrumentation Amplifier (IA), Variable Gain Amplifier (VGA), 10-bit Analog to Digital Converter (ADC) and on-chip switches. The ASIC achieved an SNR of 71 dB with a measurement accuracy of 99.7% and frequency of operation up to 700 kHz. Finally, a 16-electrode EIT hardware system was designed with the four channel ASICs. Daughter-board modules and motherboard hardware were designed with a custom software framework for data acquisition, control and communication. Images were obtained from the system with saline tank experiments.

Thesis Committee

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.