Electrical impedance imaging of human muscle at the microscopic scale using a multi-electrode needle device: A simulation study.

OBJECTIVE: To use a standard modeling approach to evaluate the feasibility of imaging healthy and diseased skeletal muscle at the microscopic scale with a novel electrical impedance imaging (EII) needle. METHODS: We modeled an EII needle containing 16 impedance electrodes arranged circumferentially around the shaft of a non-conductive 19-gauge needle in 4 planes. We then combined the finite element method approach with a reconstruction algorithm to create imaging simulations of the electrical properties of the triceps brachii by localized intramuscular fat (as might be seen in any chronic neuromuscular disease) and by localized edema (as in inflammatory myositis or after direct muscle injury). RESULTS: We were able to image a 1 cm radial region of interest with a resolution of 200 µm. Modeling localized deposition of fat and pockets of inflammatory cells, showing clear differences between the two modeled clinical states. CONCLUSIONS: This modeling study shows needle EII's ability to image the internal composition of muscle. These results can serve as an initial guide in designing and manufacturing prototype EII needles for experimental testing in animals and eventually in humans. SIGNIFICANCE: Needle EII could serve as a new minimally invasive technique for imaging human muscle at the microscopic scale, potentially serving as a new biomarker to assess disease response to therapy.