Dual-frequency electrical impedance tomography in vitro and in vivo

Dual-frequency electrical impedance tomography has been performed with frequencies of 40.96 and 81.92 kHz, giving clear images of porcine liver in vitro. For measurements in vivo on the abdomen of a human subject two features appeared consistently on the images in a posterior, peripheral position and are assumed to be the erector spinae muscles. The dual-frequency approach provides the reference measurement needed in static imaging, referencing the measurement at one frequency to that at the other to exploit the changes in conductivity with frequency in tissue. The images suffered from systematic errors arising from variations in the response of the measuring system with frequency