Non-invasive bladder volume sensing via FMCW radar: Feasibility demonstration in simulated and ex-vivo bladder models

This paper presents a proof of concept for noncontact and noninvasive bladder volume sensing in patients suffering from Neurological Lower Urinary Tract Dysfunction (NLUTD) caused by spinal cord injuries. The study investigates the feasibility of utilizing Frequency Modulated Continuous Wave (FMCW) radar as the underlying sensing modality. An algorithm for spectral data analysis is proposed to map radar measurements to bladder volume and is evaluated through MATLAB simulations. Additionally, time domain simulations of a tissue model are conducted to further assess the proposed spectral data analysis algorithm and demonstrate the feasibility of the sensing modality. The effectiveness of the sensing modality is demonstrated through a proof-of-concept measurement setup using an ex-vivo porcine bladder model, which is incrementally filled with saline solution in 200 ml portions. The results of the proposed spectral data analysis on the measured reflected waveforms reveal a strong correlation between the shift in peak frequency and the bladder volume in the model. These findings provide evidence supporting the potential of FMCW radar as a reliable and noninvasive method for continuous bladder volume monitoring.