Theranostics 2018; 8(6):1636-1647. doi:10.7150/thno.22233

Research Paper

Non-Invasive Electrical Impedance Tomography for Multi-Scale Detection of Liver Fat Content

Yuan Luo1*, Parinaz Abiri2,3*, Shell Zhang1, Chih-Chiang Chang2, Amir H. Kaboodrangi2, Rongsong Li3, Ashish K. Sahib4,5, Alex Bui2,4, Rajesh Kumar4,5, Mary Woo6, Zhaoping Li3, René R. Sevag Packard3, Yu-Chong Tai1, Tzung K. Hsiai1,2,3✉

1. Department of Medical Engineering, California Institute of Technology, Pasadena, California.
2. Department of Bioengineering, Henry Samueli School of Engineering and Applied Sciences, University of California, Los Angeles, California.
3. Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California.
4. Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, California.
5. Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, California.
6. School of Nursing, University of California, Los Angeles, California.
* Both authors contributed equally to this manuscript

Abstract

Introduction: Obesity is associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). While Magnetic Resonance Imaging (MRI) is a non-invasive gold standard to detect fatty liver, we demonstrate a low-cost and portable electrical impedance tomography (EIT) approach with circumferential abdominal electrodes for liver conductivity measurements.

Methods and Results: A finite element model (FEM) was established to simulate decremental liver conductivity in response to incremental liver lipid content. To validate the FEM simulation, we performed EIT imaging on an ex vivo porcine liver in a non-conductive tank with 32 circumferentially-embedded electrodes, demonstrating a high-resolution output given a priori information on location and geometry. To further examine EIT capacity in fatty liver detection, we performed EIT measurements in age- and gender-matched New Zealand White rabbits (3 on normal, 3 on high-fat diets). Liver conductivity values were significantly distinct following the high-fat diet (p = 0.003 vs. normal diet, n=3), accompanied by histopathological evidence of hepatic fat accumulation. We further assessed EIT imaging in human subjects with MRI quantification for fat volume fraction based on Dixon procedures, demonstrating average liver conductivity of 0.331 S/m for subjects with low Body-Mass Index (BMI < 25 kg/m²) and 0.286 S/m for high BMI (> 25 kg/m²).

Conclusion: We provide both the theoretical and experimental framework for a multi-scale EIT strategy to detect liver lipid content. Our preliminary studies pave the way to enhance the spatial resolution of EIT as a marker for fatty liver disease and metabolic syndrome.

Keywords: Fatty Liver, Nonalcoholic Fatty Liver Disease, Electrical Impedance Tomography, Fat Volume Fraction

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How to cite this article:
Luo Y, Abiri P, Zhang S, Chang CC, Kaboodrangi AH, Li R, Sahib AK, Bui A, Kumar R, Woo M, Li Z, Packard RRS, Tai YC, Hsiai TK. Non-Invasive Electrical Impedance Tomography for Multi-Scale Detection of Liver Fat Content. Theranostics 2018; 8(6):1636-1647. doi:10.7150/thno.22233. Available from http://www.thno.org/v08p1636.htm