Abstract
High-resolution (HR) mapping of the gastrointestinal (GI) bioelectrical activity is an emerging method to define the GI dysrhythmias such as gastroparesis and functional dyspepsia. Currently, there is no solution available to conduct HR mapping in long-term studies. We have developed an implantable 64-channel closed-loop near-field communication system for real-time monitoring of gastric electrical activity. The system is composed of an implantable unit (IU), a wearable unit (WU), and a stationary unit (SU) connected to a computer. Simultaneous data telemetry and power transfer between the IU and WU is carried out through a radio-frequency identification (RFID) link operating at 13.56 MHz. Data at the IU are encoded according to a self-clocking differential pulse position algorithm, and load shift keying modulated with only 6.25% duty cycle to be back scattered to the WU over the inductive path. The retrieved data at the WU are then either transmitted to the SU for real-time monitoring through an ISM-band RF transceiver or stored locally on a micro SD memory card. The measurement results demonstrated successful data communication at the rate of 125 kb/s when the distance between the IU and WU is less than 5 cm. The signals recorded in vitro at IU and received by SU were verified by a graphical user interface.
Highlights
Gastrointestinal (GI) peristalsis is coordinated by an underlying bioelectrical activity, known as slow waves (SWs)
Based on the analyses presented in Section 2.2.1 and Section 2.2.2, the 50 Ω capacitive matching of the wearable unit (WU)’s transmitter coil and the resonant network of the implantable unit (IU)’s receiver coil were calculated, network of the WU’s transmitter coil and the resonant network of the IU’s receiver coil were implemented and tuned at the radio-frequency identification (RFID) carrier frequency, i.e., 13.56 MHz
The system is featured with a 13.56 MHz inductive RFID-based closed-loop NFC between the IU and the WU
Summary
Gastrointestinal (GI) peristalsis is coordinated by an underlying bioelectrical activity, known as slow waves (SWs). Alvarez conducted pioneering studies in acquiring the SWs in 1920s [1]. SWs either directly taken from the stomach or the abdominal skin have been proven to be an indicator of the peristalsis. Direct recording of the SWs demonstrated a robust acquisition, and acceptable signal to noise ratio compared to non-invasive recordings [2]. The information that can be extracted from single channel recording of SWs is limited; as a result, high-resolution (HR) mapping has been employed in recent years [3]. HR mapping of the SWs has been shown to be an effective tool for accurately defining functional motility disorders such as gastroparesis, chronic nausea, and functional dyspepsia [4,5,6,7]
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