Towards Non-Invasive Bladder Volume Sensing via Bio-Impedance Spectroscopy: Feasibility Demonstration in Ex-Vivo Bladder Models

Abstract

A bladder volume sensing method based on Bio-Impedance Spectroscopy (BIS) is presented in this paper. The 10 kHz to 0.5 MHz BIS is performed using a Vector Network Analyzer (VNA) on an ex-vivo porcine bladder. The bio-impedance response of the bladder is measured for a saline solution from 0 to 600 ml in increments of 100 ml. The measured data was further post-processed to establish a correlation between the change in bio-impedance data and the amount of change in bladder volume. The measurement was validated across five different bladders with three iterations per bladder for further assessment of data reliability. All experiments showed a decreasing pattern in bio-impedance magnitude with respect to the increase in the bladder volume, which indicates an inverse relationship between the bio-impedance magnitude and the bladder volume. In this regard, the Impedance Change Ratio (ICR) is proposed as a metric to quantitatively characterize the change in the measured impedance associated with the change in the bladder volume. The ICR showed the impedance decrease pattern for the volume increase.