Gastrointestinal diagnosis using non-white light imaging capsule endoscopy

Capsule endoscopy (CE) has proved to be a powerful tool in the diagnosis and management of small bowel disorders since its introduction in 2001. However, white light imaging (WLI) is the principal technology used in clinical CE at present, and therefore, CE is limited to mucosal inspection, with diagnosis remaining reliant on visible manifestations of disease. The introduction of WLI CE has motivated a wide range of research to improve its diagnostic capabilities through integration with other sensing modalities. These developments have the potential to overcome the limitations of WLI through enhanced detection of subtle mucosal microlesions and submucosal and/or transmural pathology, providing novel diagnostic avenues. Other research aims to utilize a range of sensors to measure physiological parameters or to discover new biomarkers to improve the sensitivity, specificity and thus the clinical utility of CE. This multidisciplinary Review summarizes research into non-WLI CE devices by organizing them into a taxonomic structure on the basis of their sensing modality. The potential of these capsules to realize clinically useful virtual biopsy and computer-aided diagnosis (CADx) is also reported.The introduction of white light imaging capsule endoscopy has motivated research to improve its diagnostic capabilities through integration with other sensing modalities. In this Review, the authors summarize studies on non-white light imaging devices, such as those using optical coherence tomography, ultrasonography or biophysical measurementsKey pointsWhite light imaging (WLI) remains the dominant diagnostic modality in capsule endoscopy after nearly two decades of clinical use.WLI technology limits diagnosis to the mucosal surface of the gut owing to the limited penetration depth of optical wavelengths beyond the tissue surface.In the past few years, there has been an increase in the application of non-WLI diagnostic imaging and sensing technologies to capsule endoscopy, some of which are at a more advanced stage of testing than others.Integrating specific diagnostic imaging technologies into capsule endoscopy devices enables submucosal imaging, improved differentiation between malignant and benign tissue and new avenues for investigating the aetiology of disease.Many of these capsules require further testing to determine their clinical efficacy fully owing to the small sample sizes of the reported studies.New diagnostic capsule designs will provide new opportunities for improved computer-aided diagnosis, virtual biopsy and capsule localization that could benefit clinical practice in the future.