Understanding the Genesis of Cardiac Signals in Electrical Impedance Tomography

Electrical impedance tomography (EIT) is a safe and low-cost imaging technology allowing the monitoring of ventilation. While most EIT studies have investigated respiration-related events, EIT-based cardiovascular applications have received increasing attention over the last years only. Variations in intra-thoracic blood volume induce impedance changes that can be monitored with EIT and used for the estimation of hemodynamic parameters. There is, however, increasing evidence that variations in blood volume are not the only factors contributing to cardiac impedance changes within the heart. The mechanical action of the myocardium and movement of the heart-lung interface are suspected to generate impedance changes of non-negligible amplitude. To test this hypothesis we designed a dynamic 2D bio-impedance model from segmented human magnetic resonance data. EIT simulations were performed and showed that EIT signals in the heart area might be dominated up to 70% by motion-induced impedance changes.

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