Abstract:
Electrogastrography (EGG) is a non-invasive technique of recording a summation of the electrical activity in the stomach from the body surface. The electrical activity in the healthy stomach, also known as slow-waves, propagates from the proximal to the distal ends of the stomach at a frequency of approximately three cycles per minute (cpm) in humans. Any deviation in the normal slow-waves (i.e., frequency and propagation) is deemed abnormal and correlated with symptoms of functional gastric disorders. This thesis aimed to assess the performance of active and passive electrodes to improve the quality of EGG signals. This thesis consists of three primary studies: first, multi-channel passive electrodes present a design of a 64-channel electrode array and experimental validations in six human volunteers in a postprandial state using the electrode array with three different skin-electrode contact materials. A dominant frequency of 2.6 ± 0.3 cpm and antegrade propagation of the slow-waves was reported in the postprandial state; second, a design of an active electrode and experimental validations in synthetic and ECG signals were conducted. The result of this study shows that the OP2325 and TLC272 opamps demonstrated comparable performances to their passive electrodes with high signal-to-noise ratios (47-49 dB in synthetic signals and ~38 dB in ECG signals); third, integration of the opamps presents a design of flexible active electrode and experimental validation in animal studies with simultaneous ground-truth recording. The result of this study shows that the active electrodes have comparable ECG and EGG performance to their passive electrodes under experimental conditions (SNR of 17-33 dB). In conclusion, the active and passive electrodes mapping arrays are capable of detecting the dominant frequency and propagation of gastric slow-waves under normal conditions.