In vivo imaging of cardiac related impedance changes.

Electrical impedance tomography (EIT) produces cross-sectional images of the electrical resistivity distribution within the body, made from voltage or current measurements through electrodes attached around the body. The authors describe a gated EIT system to image the cardiogenic electrical resistivity variations and the results of in vivo studies on human subjects. It is shown that the sensitivity of EIT to tissue resistivity variations due to blood perfusion is good enough to image blood flow to the lungs; hence, abnormalities in pulmonary perfusion, such as pulmonary embolism, should appear in EIT images. In addition, more valuable information related to the cardiac activity can be gained from EIT images than from impedance cardiography. It is thus likely that a cardiac output index may be calculable from the average resistivity variations over the ventricles, but considerable research is required before the images can be understood in detail.