Emerging issues and future developments in capsule endoscopy
Introduction
Since 1950, orally administered capsules with radiofrequency (RF) transmission capability have been prototyped with an aim to study the physiological parameters of the gastrointestinal (GI) tract. A dearth of miniaturized electronic technology such as semiconductors and integrated circuits prevented development of these capsules until the beginning of the 21st century [1]. Working independently, Gavriel Iddan (Israel) and Paul Swain (UK) introduced capsule endoscopy (CE) in 2000 as a means for providing patients with endoscopic imaging of the small bowel [2]. First CE human trials were presented in 2001 by Given Imaging Ltd. (Yoqneam, Israel), which was the first to commercialize the technology [1]. Given Imaging’s first clinical CE, marketed as M2A (Mouth-to-Anus), was awarded approval from the Food And Drug Administration (FDA) in 2001. The second capsule to gain FDA approval was the M2A Plus, which was later remarketed under the now familiar name: PillCam. Since the first FDA CE approval, more than 2 million capsules have been ingested worldwide [3]. The PillCam series of capsules now encompasses approximately 95% of the CE market and has been used in more than 1.7 million procedures worldwide and in more than 1900 clinical studies (www.givenimaging.co). Today, leading CE companies include the following: Medtronic Inc (USA) (Given Imaging Ltd was acquired by Covidien Ltd, which was, in turn, acquired by Medtronic Inc in 2014), Olympus Corporation (Japan), Chongqing Jinshan Science & Technology Co Ltd, (China), IntroMedic Co Ltd, (South Korea), and CapsoVision Inc (USA). Originally developed for diagnostic use in the small bowel, CE application has spread to use in the esophagus, stomach, and colon. CE is still most widely used in the small bowel owing to a lack of a noninvasive alternative. This review examines current technology in clinical CE as well as the latest developments in image enhancement, investigation of active locomotion, and therapeutic possibilities.
Section snippets
Esophageal CE
As opposed to the slow CE propagation through the small bowel, CE traversing the esophagus can reach speeds as high as 20 cm/s, leading to difficulties in assessing for pathology [4]. Esophageal capsule primary indications include diagnosing reflux esophagitis, Barrett esophagus, and varices [5]. The most prevalent esophageal capsule, the PillCam ESO (Given Imaging Ltd), captures images at 7 frames per second (fps) from each of 2 cameras at its longitudinal ends, for a cumulative 14 fps. During a
Image-enhanced CE
Image enhancement is used to improve standard colonoscopy procedures and is beginning to be applied in CE [22]. Compared with healthy tissue, neoplastic intestinal tissue has been shown to exhibit a lower autofluorescent response to blue or ultraviolet light. A sarcoma-detecting capsule prototype has been developed that uses an autofluorescence intensity system. Narrow band imaging and white light imaging would complement the system owing to the high false-positive rate of autofluorescence
Conclusions and future direction
CE is the primary mode of small bowel examination, and the technology has expanded to clinical applications in the esophagus, stomach, and colon. Current CEs are limited to acquiring images of the mucosa while being passively moved throughout the GI tract via peristalsis. The primary focus of CE research in recent years has been enabling active CE manipulation and extension of the technology to therapeutic functionality. The most promising mode of CE control involves actuating tethered capsules
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The author reports no direct financial interests that might pose a conflict of interest in connection with the submitted manuscript.
The research reported in this publication was supported in part by the National Institute of Biomedical Imaging and Bioengineering, USA of the National Institutes of Health under Award no. R01EB018992, and in part by the National Science Foundation, USA under grant no. CNS-1239355 and no. IIS-1453129. This material is also based on work supported by the National Science Foundation Graduate Research Fellowship Program under Grant no. 1445197. Any opinions, findings and conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Institutes of Health or the National Science Foundation.