A Method for Absolute Electrical Impedance Tomography without Measuring Reference Voltages.

Electrical impedance tomography (EIT) is a non-invasive imaging technology that reconstructs the interior conductivity distribution (variation) of the cross-section of an object through two different sets of measurement data. However, due to the unavailable reference measurements, it is usually hard to reconstruct the absolute distribution in practice. In this paper, it is verified that any measurement set of a uniform field can be expressed as the product of a parameter and a normalized reference frame. The effect of reference voltage bias on reconstruction is explored in two kinds of models, and \pm 4% is set as the reference tolerable bias. It is found that the midrange of measured voltage sets is always within the tolerable bias as the conductivity distribution changing under constant background conductivity. In the proposed method, the reference voltages are estimated by the product of the midrange of real-time measurements and the normalized reference voltages that can be obtained in simulation. This method is tested and compared to the standard method in simulations and experiments. The result illustrates that the proposed method can reconstruct absolute conductivity distribution effectively, and the image qualities in some cases can even be slightly enhanced.