Shadow-free motorized capsule enables accurate beam positioning and sectorized OCT imaging of the esophagus

In this study, we demonstrate a 12x36 mm motorized capsule for OCT imaging of the esophagus. The capsule produces unobstructed images by using a distal reflector design, thus avoiding shadow caused by the motor wires. The motor synchronous control enables three working modes: circumferential imaging, angular sector imaging and accurate beam positioning. Distortion artifacts shown in the sector imaging were found to be induced by velocity changes of the motor. We specifically characterized the motor speed and found a symmetric and repeatable behavior during sector scanning. Resampling of the sector images A-lines was carried out to achieve uniform angular spacing according to the measured speed profile. Also, distortion between consecutive sector frames was corrected using image registration to achieve stable imaging.