CLINICAL-APPLICATIONS OF CHARACTERISTIC FREQUENCY MEASUREMENTS - PRELIMINARY IN-VIVO STUDY

In vivo electrical impedance tomography images have been available for some years, and most of them show variation in impedance amplitude be tween two different states, for example between inspiration and expira tion of the lungs. A refinement of the tomography technique has made i t possible to show images of the complex impedance of the body. If sev eral frequencies are used, more information on the investigated tissue s can be collected, and new areas made available for investigation. It has been shown that tissues exhibit a characteristic frequency that c an be derived from the maximum magnitude of the (negative) reactance. The characteristic frequency-related images can be calculated from sev eral imaginary part curves obtained using the back-projection techniqu e. The paper shows in vivo impedance spectra from different parts of t he body, determines the characteristic frequency of the different in v ivo measurements and suggests different applications of characteristic frequency imaging. Several data sets are collected to show the reprod ucibility of the measurements.