The Practical Success of Impedance Techniques from an Historical Perspective

Abstract: Future problems are based on achievements of the past. They may be unresolved problems of a more basic nature or future practical applications made possible by recent technical innovations. The introductory part of this paper deals with recent history and its many significant advances. This is followed by a survey of the bioimpedance field. Past advances include contributions of the bioimpedance field to electrophysiology, biophysics, and biochemistry. More practical contributions include the data necessary for the development of diathermy techniques and modern dosimetry in the field of electromagnetic biohazards. A large array of practical applications relate to monitoring physiological events such as impedance plethysmography, impedance encephalography, impedance tomography, and body water, lung, and heart function parameters. Unresolved problems of a basic nature include topics that relate to mechanisms responsible for observed dielectric dispersions and membrane biophysics. Practical applications that can now be realized include several new electronic laboratory diagnostic techniques. Tissue spectroscopy of small biopsy samples and tissue culture samples should permit rapid extraction of valuable cellular data. This can be done for both normal and abnormal states, thus providing new diagnostic techniques. Possible sophistication of the Coulter counter principle should permit rapid investigations of many individual cell parameters, including cellular shape, using multielectrode techniques (microimpedance tomography). The theory of field‐evoked force effects is well established now and can be used to develop electronic cell manipulation and new electronic cell sorting technologies. Additional significant practical applications to the biomedical field are now possible.