- Phase I: Participants swallow the tethered capsule endoscope (TCE) so that the distal end of the TCE enters the stomach. The TCE is then slowly withdrawn by the physician in order to visualize the gastroesophageal junction and the esophagus in a retrograde fashion until the upper esophageal sphincter is reached. The image acquisition process is repeated and the participant may be asked to swallow the TCE in up to 7 different positions with 2 swallows per position (no more than 20 swallows total).