Bladder monitoring with time-frequency-difference electrical impedance tomography technique

Patients experiencing urinary bladder dysfunction have difficulties sensing the bladder fullness and this affects their quality of life. Continuous bladder volume measurement assists in determining when voiding is necessary. Electrical Impedance Tomography (EIT) is a noninvasive technique that can be used for monitoring the bladder volume by producing images of conductivity distribution, and the time-difference EIT (tdEIT) is usually used. Even though the global conductivity obtained from the images is reported the possibility to reflect the volume, the investigations were restricted to well-controlled environments or short-term measurements where long-term measurements with moderate body movement allowed are practically expected. The movement, however, could immensely affect the image reconstruction. In this study, a time–frequency difference EIT (tfdEIT) is proposed. The tfdEIT was mainly based on frequency-difference imaging and adapted to use in the time-difference manner. The investigation was conducted on five female participants, allowing moderate movement of the lower body, and the measurement lasted for ∼1 h. Fabric electrodes were also developed for this purpose. The tfdEIT could serve long-term and movement-allowed measurement. Artifacts in the images were significantly reduced with the tfdEIT. The global conductivity of tfdEIT could reflect changes in bladder volume with a higher average correlation coefficient (r = 0.84) compared to tdEIT, where r was only 0.66. Fabric electrodes could handle long-term measurement with easy and firm attachment as well.