Non - invasive Bio - impedance Measurement Using Voltage - Current Pulse Technique

Noninvasive detection is a fundamental prerequisite for pervasive healthcare system and biosensing. Along with different noninvasive techniques such as ultrasound, X-ray, magnetic resonance and optical imaging, electrical impedance spectroscopy is emerging as more suitable technique for tissue level diagnosis. This paper presents a noninvasive technique for bioelectrical impedance estimation by means of impedance spectroscopy applying voltagecurrent pulse technique and least square curve fitting method. Simple circuit for current injection and voltage detection is presented with common mode noise suppression circuit requires only two electrodes would reduce problems due to electrode polarization. The current source is presented with constant output current as low as 100 μA, about 1MΩ load variation and 10 MHz mid-range bandwidth. Voltage detection and impedance estimation is done with Data Acquisition (DAQ) tool box of Matlab R2008a and curve fitting technique. Successful simulation results in bioelectrical impedance estimation are found with 1.5% maximum error; suggest impedance measurement below 100 kHz because of higher response of permittivity and conductivity of biological tissues in this band than the high frequency band (MHz band). Keywords—bioelectrical impedance, impedance spectroscopy, curve fitting, data acquisition tool box, non-invasive biosensing.