Finite element modeling of electrode-skin contact impedance in electrical impedance tomography

1993 ◽  
Vol 40 (4) ◽  
pp. 335-343 ◽  
Author(s):  
P. Hua ◽  
E.J. Woo ◽  
J.G. Webster ◽  
W.J. Tompkins
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Electrical Impedance Tomography ◽  
Electrical Impedance ◽  
Contact Impedance ◽  
Impedance Tomography ◽  
Element Modeling ◽  
Skin Contact

scholarly journals Self-Abrading Servo Electrode Helmet for Electrical Impedance Tomography

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7058
Author(s):  
James Avery ◽  
Brett Packham ◽  
Hwan Koo ◽  
Ben Hanson ◽  
David Holder
Keyword(s):  
Acute Stroke ◽  
Electrical Impedance Tomography ◽  
Large Scale ◽  
Electrical Impedance ◽  
Applied Pressure ◽  
High Sensitivity ◽  
Haemorrhagic Stroke ◽  
Contact Impedance ◽  
Impedance Tomography ◽  
Skin Contact

Electrical Impedance Tomography (EIT) is a medical imaging technique which has the potential to reduce time to treatment in acute stroke by rapidly differentiating between ischaemic and haemorrhagic stroke. The potential of these methods has been demonstrated in simulation and phantoms, it has not yet successfully translated to clinical studies, due to high sensitivity to errors in scalp electrode mislocation and poor electrode-skin contact. To overcome these limitations, a novel electrode helmet was designed, bearing 32 independently controlled self-abrading electrodes. The contact impedance was reduced through rotation on an abrasive electrode on the scalp using a combined impedance, rotation and position feedback loop. Potentiometers within each unit measure the electrode tip displacement within 0.1 mm from the rigid helmet body. Characterisation experiments on a large-scale test rig demonstrated that approximately 20 kPa applied pressure and 5 rotations was necessary to achieve the target 5 kΩ contact impedance at 20 Hz. This performance was then replicated in a simplified self-contained unit where spring loaded electrodes are rotated by servo motors. Finally, a 32-channel helmet and controller which sequentially minimised contact impedance and simultaneously located each electrode was built which reduced the electrode application and localisation time to less than five minutes. The results demonstrated the potential of this approach to rapidly apply electrodes in an acute setting, removing a significant barrier for imaging acute stroke with EIT.

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