Analysis of parameters for optimization of biological tissue impedance contrast

A system for determining the instantaneous position of a multielectrode intraventricular catheter, based on the principles of impedance plethysmography, is developed. In order to identify the conditions producing the highest impedance contrast (tissue to blood resistivity ratio), current density and frequency of the source, as well as the effects of the biological interfaces, are examined. Experimental measurements of blood and tissue resistivities confirm the existence of an operating range that maximizes the tissue-to-blood impedance contrast. The greatest impedance contrast can be obtained, at frequencies below 4 kHz, regardless of current density. The apparent nonlinear and capacitive effects at higher frequencies and lower current levels, also suggest operation at a lower frequency range to ensure system performance