Localization of Passively Guided Capsule Endoscopes—A Review

Traditional endoscopy is conducted stationary in the hospital and requires sedation of the patient. Contrary, capsule endoscopy (CE) requires no sedation, and the patients are allowed to leave the hospital for their daily life during the procedure that lasts for several hours. Commercially available capsule endoscopes are passively moved through the gastrointestinal tract (GIT) by peristalsis. For diagnosis and intervention planning, the traveled distance and orientation of the capsules for each video frame would be highly relevant. Nevertheless, commercial capsule endoscope systems do not offer precise localization of the capsules. In the past years, many different scientific localization approaches have been proposed. These methods can be divided into video-, radio frequency-(RF), and magnetic field-based methods. In this review, a requirement profile for a localization method suitable for a commercial capsule endoscopy system is defined. The defined requirements of a localization system for capsule endoscopy are high accuracy, robustness during the daily life of a patient, and integrability with commercial capsule endoscopy systems. Afterward, promising approaches are reviewed and discussed concerning these requirements. It was revealed that the magnetic field- and video-based methods are the most promising methods, and these methods would complement each other very well. Therefore, a hybrid magnetic-field-/video-based method is suggested, which has, to the best of our knowledge, not been proposed so far.