State of the art on advancements in wireless capsule endoscopy telemetry: a systematic approach

In the last decades an innovative technique has emerged in clinical gastroenterology as a compelling alternative to the traditional wired endoscopy, known as Wireless Capsule Endoscopy (WCE). Such cutting-edge application is able to investigate the gastrointestinal (GI) tract through a miniaturized, swallowable and biocompatible capsule, equipped with electronic components. This allows for the noninvasive measurement of biological data, that is then sent to an external receiving unit through a wireless link. This systematic review prepared according to PRISMA guidelines focuses on the main technological advances of data transmission from the in-body ingestible capsule to an external receiver. A total of 142 studies were screened from a comprehensive literature search, performed in Scopus, Science Direct, and IEEE Xplore database. A final number of 47 met the inclusion criteria and were included in the review. The results highlight innovative technologies to optimize the wireless link efficacy and safety to an external receiver. High gain, wideband, omnidirectional radiation pattern, and low levels of specific absorption rate (SAR) are of crucial importance. Despite the capsule telemetry design being rather advanced, the bulk of the existing studies focus on the transmission unit design, rather than the receiving one. Moreover, comprehensive numerical studies on realistic human body models are lacking.