Use of Electrical Impedance Spectroscopy in Vivo to Distinguish Active and Rest Stages of Salivary Glands

Xerostomia, or dry mouth syndrome, is one of the radiation therapy (RT)-induced side effects experienced by head and neck cancer patients. Measuring the severity of xerostomia can be performed by several techniques such as measuring the differential weight of dental rolls placed in the mouth for a fixed time period, measuring the electromyographic activity of musculus digastricus, using parotid cup, and electrophysiological measurements by electrical impedance. The present study focuses on detecting the change in bioimpedance around the oral cavity when salivation is induced using lime juice on healthy human subjects. In this study, impedance changes between stimulated and resting states of the salivary glands for 31 healthy volunteers were measured and analyzed. Pre- and post-stimulation impedance measurement was performed on healthy volunteer subjects using impedance spectroscopy over 50 frequencies ranging from 10 kHz to 1 MHz. The electrical properties of salivary glands were extracted by fitting the measured admittance data to the well-known Cole model. Comparison of measured electrical properties of gland at the resting and stimulated states reveals the changes in the intra- and extra-cellular spaces of salivary gland as a result of saliva secretion. Statistical analysis of the spectroscopy data collected shows that there is a significant difference in electrical properties of tissue between resting and stimulated states of the salivary activity. These electrical impedance spectroscopy measurements will be used to benchmark changes of impedance due to salivary gland stimulation.