Problems of cardiac output determination from electrical impedance tomography scans

Impedance variations within the thorax related to cardiac activity have been localised using cardiac gated electrical impedance images. Since quantitative measurements of local variations can be made from those images, electrical impedance tomography gives more valuable information than impedance cardiography (ICG). However, because of the three-dimensional (3D) and non-uniform nature of the sensitivity function, localised measurements from electrical impedance tomography (EIT) scans are related to the position and geometry of the regions in which a resistivity change occurs. For accurate determination of volume changes from conductivity variations, the 3D sensitivity distribution needs to be known.