Effect of stimulation patterns on bladder volume measurement based on fringe effect of EIT sensors

Real-time monitoring of bladder volume is necessary for patients with bladder dysfunction. Electrical impedance tomography (EIT) has the potential to be used for bladder volume measurement due to its advantages of noninvasive and real-time sensing. To overcome the sensitiveness of conventional EIT measurement methods to the urine conductivity, fringe effect of EIT sensors is explored for bladder volume measurement. In order to find the best stimulation pattern, this paper simulates seven stimulation patterns (using an integer value A as indicator) with a 16-electrodes EIT sensor. Meanwhile, it is investigated how stimulation patterns act with two typical electrodes arrangement, i.e. ring and semicircle. Sensitivity distribution and characteristic values related to the fringe effect of EIT sensors are used as evaluation criteria. The results show that when A=2 and the electrodes arrangement is semicircle, the bladder region has the highest mean sensitivity. Using semicircle arrangement ensures that all stimulation patterns except A=6 and 7 have satisfactory measurement sensitivities and less errors under changes of urine conductivity.