Development and Validation of a μm-Scale Gastric Contractions Motion Tracking System Using Infrared Cameras

Monitoring mechanical muscular activity within the stomach is critical for investigating gastric dynamics. The rat model is often used but is challenging due to its small size. This paper introduces and validates a novel technique that employs infrared cameras to track reflective markers for monitoring µm-scale stomach muscular motions in rats. The proposed method offers advantages, including its high precision and insensitivity to electromagnetic interference or stimulation artifacts, and avoids the need for additional leads typically required for physiological measurements. The setup includes four Optitrack infrared cameras. Its precision was assessed using a linear motor, demonstrating the capability to discernate 5 µm variations and noise levels of 1.19 µm Root Mean Square (RMS). In vivo experiments further validated the setup on sedated Wistar rats. Stomach movements acquired by the cameras were correlated with electromyographic (EMG) recordings. Both natural contractions (i.e., intrinsic gastric frequency) and contractions under stimulation were considered. The experiments showed matching frequencies between the reference EMG and motion-tracking signals. The motion tracking setup demonstrated the ability to differentiate µm-scale steps and monitor small physiological signals. Despite limitations related to reflective artifacts, and the need for continuous visual contact, the proposed technique presents a valuable tool for monitoring stomach motions, contributing to the methodologies available for tracking muscular activity. Future work aims to enhance understanding of gastric stimulation to treat obesity.