Wireless capsule endoscopy: from diagnostic devices to multipurpose robotic systems

Endoscope Capsules: The Present Situation and Future Outlooks

This paper presents new perspectives on photonic technologies for capsule endoscopy. It first presents a review of conventional endoscopy (upper endoscopy and colonoscopy), followed by capsule endoscopy (CE), as well as their techniques, advantages, and drawbacks. The technologies for CEs presented in this paper include integration with the existing endoscopic systems that are commercially available. Such technologies include narrow-band imaging (NBI), photodynamic therapy (PDT), confocal laser endomicroscopy (CLE), optical coherence tomography (OCT), and spectroscopy in order to improve the performance of the gastrointestinal (GI) tract examination. In the context of NBI, two optical filters were designed and fabricated for integration into endoscopic capsules, allowing for the visualization of light centered at the 415 nm and 540 nm wavelengths. These optical filters are based on the principle of Fabry-Perot and were made of thin films of titanium dioxide (TiO2) and silicon dioxide (SiO2). Moreover, strategies and solutions for the adaptation of ECs for PDT are also discussed.

A Planar-Type Micro-Biopsy Tool for a Capsule-Type Endoscope Using a One-Step Nickel Electroplating Process

Millimeter-scale biopsy tools combined with an endoscope instrument have been widely used for minimal invasive surgery and medical diagnosis. Recently, a capsule-type endoscope was developed, which requires micromachining to fabricate micro-scale biopsy tools that have a sharp tip and other complex features, e.g., nanometer-scale end-tip sharpness and a complex scalpel design. However, conventional machining approaches are not cost-effective for mass production and cannot fabricate the micrometer-scale features needed for biopsy tools. Here, we demonstrate an electroplated nickel micro-biopsy tool which features a planar shape and is suitable to be equipped with a capsule-type endoscope. Planar-type micro-biopsy tools are designed, fabricated, and evaluated through in vitro tissue dissection experiments. Various micro-biopsy tools with a long shaft and sharp tip can be easily fabricated using a thick photoresist (SU8) mold via a simple one-step lithography and nickel electroplating process. The characteristics of various micro-biopsy tool design features, including a tip taper angle, different tool geometries, and a cutting scalpel, are evaluated for efficient tissue extraction from mice intestine. These fabricated biopsy tools have shown appropriate strength and sharpness with a sufficient amount of tissue extraction for clinical applications, e.g., cancer tissue biopsy. These micro-scale biopsy tools could be easily integrated with a capsule-type endoscope and conventional forceps.

Biocompatible and Long-Term Monitoring Strategies of Wearable, Ingestible and Implantable Biosensors: Reform the Next Generation Healthcare

Sensors enable the detection of physiological indicators and pathological markers to assist in the diagnosis, treatment, and long-term monitoring of diseases, in addition to playing an essential role in the observation and evaluation of physiological activities. The development of modern medical activities cannot be separated from the precise detection, reliable acquisition, and intelligent analysis of human body information. Therefore, sensors have become the core of new-generation health technologies along with the Internet of Things (IoTs) and artificial intelligence (AI). Previous research on the sensing of human information has conferred many superior properties on sensors, of which biocompatibility is one of the most important. Recently, biocompatible biosensors have developed rapidly to provide the possibility for the long-term and in-situ monitoring of physiological information. In this review, we summarize the ideal features and engineering realization strategies of three different types of biocompatible biosensors, including wearable, ingestible, and implantable sensors from the level of sensor designing and application. Additionally, the detection targets of the biosensors are further divided into vital life parameters (e.g., body temperature, heart rate, blood pressure, and respiratory rate), biochemical indicators, as well as physical and physiological parameters based on the clinical needs. In this review, starting from the emerging concept of next-generation diagnostics and healthcare technologies, we discuss how biocompatible sensors revolutionize the state-of-art healthcare system unprecedentedly, as well as the challenges and opportunities faced in the future development of biocompatible health sensors.

Experimental Research on a Capsule Robot with Spring-Connected Legs

Based on a previous study of a novel capsule robot (CR) with spring-connected legs that could collect intestinal juice for biopsy, in this research, an experiment system is designed, and two experiments are carried out. One of the experiments measures the torque and cutting force of this CR, and the other experiment tests and evaluates the biopsy function of this CR. In the measuring experiment, we analyze how the magnetic torque exerted on this CR changes. In the experiment with a biopsy, we decompose the biopsy actions and select the most effective biopsy action. The result of the experiments shows that this CR can collect and store biopsy samples ideally, and the most effective biopsy action is the rotation with legs extended.

Recent developments in wireless capsule endoscopy imaging: Compression and summarization techniques

Wireless capsule endoscopy (WCE) can be viewed as an innovative technology introduced in the medical domain to directly visualize the digestive system using a battery-powered electronic capsule. It is considered a desirable substitute for conventional digestive tract diagnostic methods for a comfortable and painless inspection. Despite many benefits, WCE results in poor video quality due to low frame resolution and diagnostic accuracy. Many research groups have presented diversified, low-complexity compression techniques to economize battery power consumed in the radio-frequency transmission of the captured video, which allows for capturing the images at high resolution. Many vision-based computational methods have been developed to improve the diagnostic yield. These methods include approaches for automatically detecting abnormalities and reducing the amount of time needed for video analysis. Though various research works have been put forth in the WCE imaging field, there is still a wide gap between the existing techniques and the current needs. Hence, this article systematically reviews recent WCE video compression and summarization techniques. The review's objectives are as follows: First, to provide the details of the requirement, challenges and design percepts for the low complexity WCE video compressor. Second, to discuss the most recent compression methods, emphasizing simple distributed video coding methods. Next, to review the most recent summarization techniques and the significance of using deep neural networks. Further, this review aims to provide a quantitative analysis of the state-of-the-art methods along with their advantages and drawbacks. At last, to discuss existing problems and possible future directions for building a robust WCE imaging framework.

An Overview of the Evolution of Capsule Endoscopy Research—Text-Mining Analysis and Publication Trends

There has been a steady increase (annual percentage growth rate of 19.2%, average of 18.3 citations per document) in capsule endoscopy (CE) publications from a global, interdisciplinary research community on a growing range of CE applications over the last 20+ years. We here present the status of CE as a field of research, tracing its evolution over time and providing insight into its potential for diagnostics, prevention and treatment of gastrointestinal (GI) tract diseases. To portray the development of the CE research landscape in the 2000–2021 time span, we analyzed 5764 scientific publications. Analyses were performed using the R language and environment for statistical computing and graphics and VOSviewer, a software developed for scientific literature analysis by scientometricians. The aim of this paper is to provide a wide comprehensive analysis of the trends in CE publications. We thus performed subgroup analysis on the selected papers, including indications, annual percentage growth rate, average citations per document, most publications from research areas/interdisciplinary field of the articles, geography, collaboration networks through institutions, specific clinical keywords and device type. The firm increase in CE publications over the last two decades highlights the overall strength of the technology in GI applications. Furthermore, the introduction to the field of artificial intelligence (AI) tools has been promoting a range of technological advances that keep on affecting the diagnostic potential of CE.

Design and analysis of a wireless power transfer system for capsule robot using an optimised planar square spiral transmitting coil pair

BACKGROUND

The wireless power transfer system (WPTS) is a promising way to continuously provide efficient and stable power for gastrointestinal capsule robots with active movement ability.

METHODS

The proposed WPTS using an optimised planar square spiral transmitting coil pair with space-saving structure can flexibly adjust the distance between the coils according to the patient's condition, and thus has better applicability. To improve power transfer efficiency and uniformity of the generated magnetic field, design parameters are discussed and optimised based on the analytical calculation and simulation analysis.

RESULTS

The power demand can be guaranteed with spacing distance of 350-500 mm and the peak received power of 1124 mW with a remarkable transfer efficiency of 7.8% can be obtained when the spacing reaches the minimum. The human electromagnetic exposure safety in different situations is also discussed and verified.

CONCLUSIONS

The WPTS can provide power for capsule robots safely and efficiently.

Design and Control of a Magnetically-Actuated Capsule Robot with Biopsy Function

OBJECTIVE

Wireless capsule endoscopy has been well used for gastrointestinal (GI) tract diagnosis. However, it can only obtain images and cannot take samples of GI tract tissues. In this study, we designed a magnetically-actuated biopsy capsule (MABC) robot for GI tract diagnosis.

METHODS

The proposed robot can achieve locomotion and biopsy functions under the control of external electromagnetic actuation (EMA) system. Two types of active locomotion can be achieved, plane motion refers to the robot rolling on the surface of the GI tract with a rotating uniform magnetic field. 3D motion refers to the robot moving in 3D space under the control of the EMA system. After reaching the target position, the biopsy needle can be sprung out for sampling and then retracted under a gradient magnetic field.

RESULTS

A pill-shaped robot prototype (15mm 32mm) has been fabricated and tested with phantom experiments. The average motion control error is 0.32mm in vertical direction, 3.3mm in horizontal direction, and the maximum sampling error is about 5.0mm. The average volume of the sampled tissue is about 0.35mm3.

CONCLUSION

We designed a MABC robot and proposed a control framework which enables planar and 3D spatial locomotion and biopsy sampling.

SIGNIFICANCE

The untethered MABC robot can be remotely controlled to achieve accurate sampling in multiple directions without internal power sources, paving the way towards precision sampling techniques for GI diseases in clinical procedures.

Patient-Reported Outcomes and Preferences for Colon Capsule Endoscopy and Colonoscopy: A Systematic Review with Meta-Analysis

Colon capsule endoscopy as an alternative to colonoscopy for the diagnosis of colonic disease may serve as a less invasive and more tolerable investigation for patients. Our aim was to examine patient-reported outcomes for colon capsule endoscopy compared to conventional optical colonoscopy including preference of investigation modality, tolerability and adverse events. A systematic literature search was conducted in Web of Science, PubMed and Embase. Search results were thoroughly screened for in- and exclusion criteria. Included studies underwent assessment of transparency and completeness, after which, data for meta-analysis were extracted. Pooled estimates of patient preference were calculated and heterogeneity was examined including univariate meta-regressions. Patient-reported tolerability and adverse events were reviewed. Out of fourteen included studies, twelve had investigated patient-reported outcomes in patients who had undergone both investigations, whereas in two the patients were randomized between investigations. Pooled patient preferences were estimated to be 52% (CI 95%: 41-63%) for colon capsule endoscopy and 45% (CI 95%: 33-57%) for conventional colonoscopy: not indicating a significant difference. Procedural adverse events were rarely reported by patients for either investigation. The tolerability was high for both colon capsule endoscopy and conventional colonoscopy. Patient preferences for conventional colonoscopy and colon capsule endoscopy were not significantly different. Procedural adverse events were rare and the tolerability for colon capsule endoscopy was consistently reported higher or equal to that of conventional colonoscopy.

Detection and Classification of Gastrointestinal Diseases using Machine Learning

BACKGROUND

Traditional endoscopy is an invasive and painful method of examining the gastrointestinal tract (GIT) not supported by physicians and patients. To handle this issue, video endoscopy (VE) or wireless capsule endoscopy (WCE) is recommended and utilized for GIT examination. Furthermore, manual assessment of captured images is not possible for an expert physician because it's a time taking task to analyze thousands of images thoroughly. Hence, there comes the need for a Computer-Aided-Diagnosis (CAD) method to help doctors analyze images. Many researchers have proposed techniques for automated recognition and classification of abnormality in captured images.

METHODS

In this article, existing methods for automated classification, segmentation and detection of several GI diseases are discussed. Paper gives a comprehensive detail about these state-of-theart methods. Furthermore, literature is divided into several subsections based on preprocessing techniques, segmentation techniques, handcrafted features based techniques and deep learning based techniques. Finally, issues, challenges and limitations are also undertaken.

RESULTS

A comparative analysis of different approaches for the detection and classification of GI infections.

CONCLUSION

This comprehensive review article combines information related to a number of GI diseases diagnosis methods at one place. This article will facilitate the researchers to develop new algorithms and approaches for early detection of GI diseases detection with more promising results as compared to the existing ones of literature.

Next-generation ingestible devices: sensing, locomotion and navigation

There is significant interest in exploring the human body's internal activities and measuring important parameters to understand, treat and diagnose the digestive system environment and related diseases. Wireless capsule endoscopy (WCE) is widely used for gastrointestinal (GI) tract exploration due to its effectiveness as it provides no pain and is totally tolerated by the patient. Current ingestible sensing technology provides a valuable diagnostic tool to establish a platform for monitoring the physiological and biological activities inside the human body. It is also used for visualizing the GI tract to observe abnormalities by recording the internal cavity while moving. However, the capsule endoscopy is still passive, and there is no successful locomotion method to control its mobility through the whole GI tract. Drug delivery, localization of abnormalities, cost reduction and time consumption are improvements that can be gained from having active ingestible WCEs. In this article, the current technological developments of ingestible devices including sensing, locomotion and navigation are discussed and compared. The main features required to implement next-generation active WCEs are explored. The methods are evaluated in terms of the most important features such as safety, velocity, complexity of design, control, and power consumption.

Retention of an endoscopic videocapsule on inflammatory polyposis of the small bowel

The Video Capsule Diagnostic Imaging is a technique for exploring the digestive tract, particularly the small bowel. It is indicated for any unexplained digestive bleeding or as a means of monitoring intestinal polyposis or inflammatory diseases. This videocapsule is not digestible, and the risk of its retention, symptomatic or not, is not negligible following an inflammatory, anastomatous or tumoral stenosis. This retention or blockage is defined by the presence of the Video Capsule in the digestive tract at least two weeks after ingestion. Surgical approach is considered effective to retrieve the retained capsule, treat the pathology responsible and prevent acute complications.

We report the case of retention of a video capsule in a young patient with severe anaemia due to inflammatory polyposis of the small bowl, whose removal required surgery to extract the capsule and resect the segment of the small intestine stenosis by the polyps.

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The video Capsule Endoscopy is the most sensitive examination for the detection of inflammatory lesions of the small bowel.

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It does not currently allow a biopsy but it is indicated for unexplained or occult digestive bleeding.

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Its main limitation is the risk of blockage in a stenosis with or without occlusion.

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Surgical approach is considered effective to retrieve the retained capsule, and treat the pathology responsible.

A Review on Lossless Compression Techniques for Wireless Capsule Endoscopic Data

BACKGROUND

The videos produced during wireless capsule endoscopy have larger data size causing difficulty in transmission with limited bandwidth. The constraint on wireless capsule endoscopy hinders the performance of the compression module.

OBJECTIVES

The objectives of this paper are as follows: (i) to conduct an extensive review of the lossless compression techniques and (ii) to find out the limitations of the existing system and the possibilities for improvement.

METHODS

The literature review was conducted with a focus on the compression schemes satisfying minimum computational complexity, less power dissipation and low memory requirements for hardware implementation. A thorough study of various lossless compression techniques was conducted under two perspectives, i.e., techniques applied to Bayer CFA and RGB images. The detail of the various stages of wireless capsule endoscopy compression was investigated to have a better understanding. The suitable performance metrics for evaluating the compression techniques were listed from various literature studies.

RESULTS

In addition to the Gastrolab database, WEO clinical endoscopy atlas and Gastrointestinal atlas were found to be better alternatives for experimentation. Pre-processing operations, especially new subsampling patterns need to be given more focus to exploit the redundancies in the images. Investigations showed that encoder module can be modified to bring more improvement towards compression. The real-time endoscopy still exists as a promising area for exploration.

CONCLUSION

This review presents a research update on the details of wireless capsule endoscopy compression together with the findings as an eye-opener and guidance for further research.

Understanding deep learning in capsule endoscopy: Can artificial intelligence enhance clinical practice?

Wireless capsule endoscopy (WCE) enables physicians to examine the gastrointestinal tract by transmitting images wirelessly from a disposable capsule to a data recorder. Although WCE is the least invasive endoscopy technique for diagnosing gastrointestinal disorders, interpreting a WCE study requires significant time effort and training. Analysis of images by artificial intelligence, through advances such as machine or deep learning, has been increasingly applied to medical imaging. There has been substantial interest in using deep learning to detect various gastrointestinal disorders based on WCE images. This article discusses basic knowledge of deep learning, applications of deep learning in WCE, and the implementation of deep learning model in a clinical setting. We anticipate continued research investigating the use of deep learning in interpreting WCE studies to generate predictive algorithms and aid in the diagnosis of gastrointestinal disorders.

USB capsule endoscope for retrograde imaging of the esophagus

SIGNIFICANCE

Endoscopes represent electro-optical devices that are used to visualize internal body cavities. The specialized endoscopic procedure of the upper gastrointestinal tract from the esophagus down to the duodenum is called an esophagogastroduodenoscopy.

AIM

We bring our newly developed capsule endoscopy device as a promising alternative diagnostic method for visualization of the upper gastrointestinal tract.

APPROACH

Capsule endoscopy has become an attractive method that uses a tiny wireless camera to take pictures of the digestive tract. Existing esophageal capsule endoscopy does not allow a retrograde view of the esophagus while retrograde scanning can provide information on the esophageal pathology.

RESULTS

In comparison to the existing esophageal capsule endoscopy, our system is much simpler and cheaper due to the need for fewer electronic devices. Moreover, its use is not limited by the capacity of the batteries used by existing capsule endoscopes. The new esophageal endoscopic system was created by combining the universal serial bus (USB) endoscope module with the thin power wires that are routed through the USB port to the computer.

CONCLUSIONS

The endoscope was tested on a volunteer without any side effects such as nausea, belching, and general discomfort. The examination of the patient is performed in a sitting position and the patient discomfort during the examination is minimal so it can be performed without anesthesia.

Current Advances in Drug Delivery Systems for Capsule Endoscopy

BACKGROUND

Oral administration of medications and current oral modified-release systems are the most preferred drug delivery routes, but they provide efficacy up to 12-24 hours per administration and are not useful when the patient has short transit time. The once-daily administered formulations are the endpoint of many types of drug development, and some innovations in capsule endoscopy (CE) can solve this problem.

OBJECTIVE

This review aims to reveal recent advances in drug delivery systems (DDS) for CE as an essential field of research for more precise drug targeting at the gastrointestinal (GI) tract.

METHODS

We performed a narrative overview of the MEDLINE database from 1991-2020 using the keywords of DDS and CE with synthesizing the findings, hand searches, and authoritative articles.

RESULTS

There are microelectromechanical systems and non-mechanical patent technologies for DDS for CE, and the implementation of wireless-capsule medical devices into the human body will provide new diagnostic and therapeutic options. Integrating biomedical CE with DDS and the cloud technology will bring remote real-time feedbackbased automated treatment or responsive medication.

CONCLUSION

Swallowable drug delivery systems for capsule endoscopy brings an entirely new approach for diagnostic and therapeutic methods in digestive diseases.

Super-Soft and Super-Elastic DNA Robot with Magnetically Driven Navigational Locomotion for Cell Delivery in Confined Space

Soft organisms such as earthworms can access confined, narrow spaces, inspiring scientists to fabricate soft robots for in vivo manipulation of cells or tissues and minimally invasive surgery. We report a super-soft and super-elastic magnetic DNA hydrogel-based soft robot (DNA robot), which presents a shape-adaptive property and enables magnetically driven navigational locomotion in confined and unstructured space. The DNA hydrogel is designed with a combinational dynamic and permanent crosslinking network through chain entanglement and DNA hybridization, resulting in shear-thinning and cyclic strain properties. DNA robot completes a series of complex magnetically driven navigational locomotion such as passing through narrow channels and pipes, entering grooves and itinerating in a maze by adapting and recovering its shape. DNA robot successfully works as a vehicle to deliver cells in confined space by virtue of the 3D porous networked structure and great biocompatibility.

Investigation of Current Control for a New Bi-directional Linear Capsule Robot

In this paper, a bi-directional linear capsule robot (capsulbot) for potential applications in Gastrointestinal (GI) tract inside human body is studied. Compared with the conventional endoscope limited by its poor locomotion and steering capabilities, active locomotion actuator will play an important role in the diagnosis of narrow organ tract of the human body in the future. This paper studies a new simple-structured actuator that can realize bi-directional linear motion by properly controlling the supplied current profile. It is demonstrated that the linear motion of the new capsulbot is affected by three main factors: current waveform, current duty ratio, and current amplitude. The optimized current profile that can maximize the capsulbot displacement is verified experimentally on a prototype capsulbot.

Methods for powering bioelectronic microdevices

Bioelectronic microdevices are an emerging class of biomedical devices miniaturized at the scale of a millimeter or less, which promise new capabilities for monitoring and treating human disease. Although rapid progress has been made in the sensing and actuation capabilities of microdevices, a major technological challenge remains in the way that these devices are powered within the body. In this review, we revisit the power requirements of microdevices, describe current methods for storing, transferring or harvesting energy in microdevices, provide an overview of emerging powering approaches and discuss the promise of microdevices in biomedicine.

A Locomotion Control Platform With Dynamic Electromagnetic Field for Active Capsule Endoscopy

Conventional radiological and endoscopic techniques utilizing long tubes were ineffective in visualizing the small bowel mucosa until the development of wireless capsule endoscopy (WCE). WCE is a revolutionary endoscopic technology that can diagnose the complete gastrointestinal tract. However, the existing capsule technologies are passive, and thus they cannot be navigated to or held in a specific location. The design of an active capsule will present the opportunity to move and stop a device at any targeted locations leading to numerous medical applications such as drug delivery or collecting tissue samples for examinations in the laboratory. This paper implements a new locomotion methodology for WCE systems using an electromagnetic platform. The platform produces a dynamic electromagnetic field to control the motion of the capsule. The strength and the direction of the electromagnetic field that is generated by the platform are continuously adjusted in order to maintain the equilibrium state during the capsule movement. We present the detailed design of the proposed platform with an experimental setup with polyvinyl chloride tubes and ex vivo to demonstrate the performance of the capsule motion.

Robotic Endoscopy

Endoscopes extend the eyes of the physician into the patient's body. They are widely used in gastrointestinal (GI) diagnostics and minimally invasive surgery. Endoscopes can be classified into 3 types: rigid, flexible, and capsule endoscopes. Rigid and flexible endoscopes are traditionally held and manipulated by the physician to visualize the region of interest, while capsule endoscopes move passively along with the GI peristalsis. With the advancement of technology, robotic endoscopy has been increasingly developed and accepted. In this work, robotic endoscopy from 3 categories (robot-assisted rigid endoscopy, robot-assisted flexible endoscopy, and active GI endoscopy including active flexible colonoscopy and active capsule endoscopy) is reviewed by PubMed search with the criteria ('Robotics' OR 'Robot') and ('Endoscopy' OR 'Endoscope').

Are Current Advances of Compression Algorithms for Capsule Endoscopy Enough? A Technical Review

The recent technological advances in capsule endoscopy system have revolutionized the healthcare system by introducing new techniques and functionalities to diagnose gastrointestinal tract. These techniques improve diagnostic accuracy and reduce the risk of hospitalization. Although many benefits of capsule endoscopy are known, there are still limitations including lower battery life, higher bandwidth, poor image quality and lower frame rate, which have restricted its wide use. In order to solve these limitations, the importance of a low-cost compression algorithm, that produces higher frame rate with better image quality and yet consumes lower bandwidth and transmission power, is paramount. While several review papers have been published describing the capability of capsule endoscope in terms of its functionality and emerging features, an extensive review on the compression algorithms from past and for future applications is still of great interest. Hence, in this review, we aim to address the issue by exploring the characteristics of endoscopic images, analyzing the strengths and weaknesses of useful compression techniques, and making suggestions for possible future adaptation.

Acoustic Sensing and Ultrasonic Drug Delivery in Multimodal Theranostic Capsule Endoscopy

Video capsule endoscopy (VCE) is now a clinically accepted diagnostic modality in which miniaturized technology, an on-board power supply and wireless telemetry stand as technological foundations for other capsule endoscopy (CE) devices. However, VCE does not provide therapeutic functionality, and research towards therapeutic CE (TCE) has been limited. In this paper, a route towards viable TCE is proposed, based on multiple CE devices including important acoustic sensing and drug delivery components. In this approach, an initial multimodal diagnostic device with high-frequency quantitative microultrasound that complements video imaging allows surface and subsurface visualization and computer-assisted diagnosis. Using focused ultrasound (US) to mark sites of pathology with exogenous fluorescent agents permits follow-up with another device to provide therapy. This is based on an US-mediated targeted drug delivery system with fluorescence imaging guidance. An additional device may then be utilized for treatment verification and monitoring, exploiting the minimally invasive nature of CE. While such a theranostic patient pathway for gastrointestinal treatment is presently incomplete, the description in this paper of previous research and work under way to realize further components for the proposed pathway suggests it is feasible and provides a framework around which to structure further work.

Magnetically guided capsule endoscopy

Wireless capsule endoscopy (WCE) is a powerful tool for medical screening and diagnosis, where a small capsule is swallowed and moved by means of natural peristalsis and gravity through the human gastrointestinal (GI) tract. The camera-integrated capsule allows for visualization of the small intestine, a region which was previously inaccessible to classical flexible endoscopy. As a diagnostic tool, it allows to localize the sources of bleedings in the middle part of the gastrointestinal tract and to identify diseases, such as inflammatory bowel disease (Crohn's disease), polyposis syndrome, and tumors. The screening and diagnostic efficacy of the WCE, especially in the stomach region, is hampered by a variety of technical challenges like the lack of active capsular position and orientation control. Therapeutic functionality is absent in most commercial capsules, due to constraints in capsular volume and energy storage. The possibility of using body-exogenous magnetic fields to guide, orient, power, and operate the capsule and its mechanisms has led to increasing research in Magnetically Guided Capsule Endoscopy (MGCE). This work shortly reviews the history and state-of-art in WCE technology. It highlights the magnetic technologies for advancing diagnostic and therapeutic functionalities of WCE. Not restricting itself to the GI tract, the review further investigates the technological developments in magnetically guided microrobots that can navigate through the various air- and fluid-filled lumina and cavities in the body for minimally invasive medicine.

Ingestible Sensors

Ingestible sensing capsules are fast emerging as a critical technology that has the ability to greatly impact health, nutrition, and clinical areas. These ingestible devices are noninvasive and hence are very attractive for customers. With widespread access to smart phones connected to the Internet, the data produced by this technology can be readily seen and reviewed online, and accessed by both users and physicians. The outputs provide invaluable information to reveal the state of gut health and disorders as well as the impact of food, medical supplements, and environmental changes on the gastrointestinal tract. One unique feature of such ingestible sensors is that their passage through the gut lumen gives them access to each individual organ of the gastrointestinal tract. Therefore, ingestible sensors offer the ability to gather images and monitor luminal fluid and the contents of each gut segment including electrolytes, enzymes, metabolites, hormones, and the microbial communities. As such, an incredible wealth of knowledge regarding the functionality and state of health of individuals through key gut biomarkers can be obtained. This Review presents an overview of the gut structure and discusses current and emerging digestible technologies. The text is an effort to provide a comprehensive overview of ingestible sensing capsules, from both a body physiology point of view as well as a technological view, and to detail the potential information that they can generate.

Design of a Wireless Medical Capsule for Measuring the Contact Pressure Between a Capsule and the Small Intestine

A wireless medical capsule for measuring the contact pressure between a mobile capsule and the small intestine lumen was developed. Two pressure sensors were used to measure and differentiate the contact pressure and the small intestine intraluminal pressure. After in vitro tests of the capsule, it was surgically placed and tested in the proximal small intestine of a pig model. The capsule successfully gathered and transmitted the pressure data to a receiver outside the body. The measured pressure signals in the animal test were analyzed in the time and frequency domains, and a mathematic model was presented to describe the different factors influencing the contact pressure. A novel signal processing method was applied to isolate the contraction information from the contact pressure. The result shows that the measured contact pressure was 1.08 ± 0.08 kPa, and the small intestine contraction pressure's amplitude and rate were 0.29 ± 0.046 kPa and 12 min−1. Moreover, the amplitudes and rates of pressure from respiration and heartbeat were also estimated. The successful preliminary evaluation of this capsule implies that it could be used in further systematic investigation of small intestine contact pressure on a mobile capsule-shaped bolus.

Bio-inspired enhancement of friction and adhesion at the polydimethylsiloxane-intestine interface and biocompatibility characterization

An active navigation of self-propelled miniaturized robot along the intestinal tract without injuring the soft tissue remains a challenge as yet. Particularly in this case an effective control of the interfacial friction and adhesion between the material used and the soft tissue is crucial. In the present study, we investigated the frictional and adhesive properties between polydimethylsiloxane (PDMS, microscopically patterned with micro-pillar arrays and non-patterned with a flat surface) and rabbit small intestinal tract using a universal material tester. The friction coefficient-time plot and adhesive force-time plot were recorded during the friction test (sliding speed: 0.25mm/s; normal loading: 0.4N) and adhesion test (preloading: 0.5N; hoisting speed: 2.5×10^-3mm/s). In addition, biocompatibility of the PDMS samples was characterized in terms of cell morphology (scanning electron microscope) and cell cytotoxicity (alamarBlue assay) using human vascular endothelial cells (HUVECs). The results demonstrated that the interfacial friction (0.27 vs 0.19) and adhesion (34.9mN vs 26.7mN) were greatly increased using microscopically patterned PDMS, in comparison with non-patterned PDMS. HUVECs adhered to and proliferated on non-patterned/microscopically patterned PDMS very well, with a relative cell viability of about 90% following seeding at 1d, 3d, and 5d. The favorable enhancement of the frictional and adhesive properties, along with the excellent biocompatibility of the microscopically patterned PDMS, makes it a propitious choice for clinical application of self-propelled miniaturized robots.

A Review of Locomotion Systems for Capsule Endoscopy

Wireless capsule endoscopy for gastrointestinal (GI) tract is a modern technology that has the potential to replace conventional endoscopy techniques. Capsule endoscopy is a pill-shaped device embedded with a camera, a coin battery, and a data transfer. Without a locomotion system, this capsule endoscopy can only passively travel inside the GI tract via natural peristalsis, thus causing several disadvantages such as inability to control and stop, and risk of capsule retention. Therefore, a locomotion system needs to be added to optimize the current capsule endoscopy. This review summarizes the state-of-the-art locomotion methods along with the desired locomotion features such as size, speed, power, and temperature and compares the properties of different methods. In addition, properties and motility mechanisms of the GI tract are described. The main purpose of this review is to understand the features of GI tract and diverse locomotion methods in order to create a future capsule endoscopy compatible with GI tract properties.

Infrared Fluorescence-Based Cancer Screening Capsule for the Small Intestine

Infrared fluorescence endoscopy (IRFE), in conjunction with an infrared fluorescent-labelling contrast agent, is a well known technique used for efficient early-stage cancer detection. In this paper we present a cost-effective (< $500) screening capsule prototype, which is able to detect infrared (IR) fluorescence emitted by indocyanine green (ICG) fluorophore dye. Rather than image, the capsule works as a high-sensitivity fluorometer that records fluorescence levels throughout the small intestine. The presented mixed-signal system has a small size, consumes very little power (≈ 6.3 mA) and does not require an external belt and hardware for data collection. By determining fluorescence levels in the intestine, rather than collecting images, we avoid the need for labour intensive video analysis. The whole system is contained within a compact ingestible capsule, that is sized so as to come into close contact with the intestine walls during peristalsis. Ex-vivo experiments, on ICG-impregnated swine intestine, have shown that the prototype system is able to detect low concentrations of ICG in the nanomolar and micromolar region, which is required to detect early cancer in the small intestine.

A novel hybrid microrobot using rotational magnetic field for medical applications

Magnetically actuated microrobots for such tools have potential accomplish procedures in biological and medical applications. In this paper, a novel magnetically actuated hybrid microrobot with hybrid motion driven by an electromagnetic actuation system has been proposed. An o-ring type permanent magnet is embedded in the hybrid microrobot as an actuator driven by rotational magnetic field which is generated by a 3 axes Helmholtz coils. It is composed by two motion mechanisms. One is the spiral jet motion moved by rotating its body. The other one is fin motion moved by vibrating its body. Because only one permanent magnet is used inside the hybrid microrobot, two motions can be controlled separately without any interference. The hybrid microrobot can change its two motions to realize multi-DOFs movement and flexibility motion. The verified experiments are conducted in the pipe. The experimental results indicate that the moving speed can be controlled by adjusting the magnetic field changing frequency and the direction of motion can be controlled by changing the magnetic field direction.

Swallowable fluorometric capsule for wireless triage of gastrointestinal bleeding

Real-time detection of gastrointestinal bleeding remains a major challenge because there does not yet exist a minimally invasive technology that can both i) monitor for blood from an active hemorrhage and ii) uniquely distinguish it from blood left over from an inactive hemorrhage. Such a device would be an important tool for clinical triage. One promising solution, which we have proposed previously, is to inject a fluorescent dye into the blood stream and to use it as a distinctive marker of active bleeding by monitoring leakage into the gastrointestinal tract with a wireless fluorometer. This paper reports, for the first time to our knowledge, the development of a swallowable, wireless capsule with a built-in fluorometer capable of detecting fluorescein in blood, and intended for monitoring gastrointestinal bleeding in the stomach. The embedded, compact fluorometer uses pinholes to define a microliter sensing volume and to eliminate bulky optical components. The proof-of-concept capsule integrates optics, low-noise analog sensing electronics, a microcontroller, battery, and low power Zigbee radio, all into a cylindrical package measuring 11 mm × 27 mm and weighing 10 g. Bench-top experiments demonstrate wireless fluorometry with a limit-of-detection of 20 nM aqueous fluorescein. This device represents a major step towards a technology that would enable simple, rapid detection of active gastrointestinal bleeding, a capability that would save precious time and resources and, ultimately, reduce complications in patients.

A UWB wireless capsule endoscopy device

Wireless capsule endoscopy (WCE) presents many advantages over traditional wired endoscopic methods. The performance of WCE devices can be improved using high-frequency communication systems such as Impulse Radio-Ultra-Wideband (IR-UWB) to enable a high data rate transmission with low-power consumption. This paper presents the hardware implementation and experimental evaluation of a WCE device that uses IR-UWB signals in the frequency range of 3.5 GHz to 4.5 GHz to transmit image data from inside the body to a receiver placed outside the body. Key components of the IR-UWB transmitter, such as the narrow pulse generator and up-conversion based RF section are described in detail. This design employs a narrowband receiver in the WCE device to receive a control signal externally in order to control and improve the data transmission from the device in the body. The design and performance of a wideband implantable antenna that operates in the aforementioned frequency range is also described. The operation of the WCE device is demonstrated through a proof-of-concept experiment using meat.

Color multiplexing method to capture front and side images with a capsule endoscope

This paper proposes a capsule endoscope (CE), based on color multiplexing, to simultaneously record front and side images. Only one lens associated with an X-cube prism is employed to catch the front and side view profiles in the CE. Three color filters and polarizers are placed on three sides of an X-cube prism. When objects locate at one of the X-cube's three sides, front and side view profiles of different colors will be caught through the proposed lens and recorded at the color image sensor. The proposed color multiplexing CE (CMCE) is designed with a field of view of up to 210 deg and a 180 lp/mm resolution under f-number 2.8 and overall length 13.323 mm. A ray-tracing simulation in the CMCE with the color multiplexing mechanism verifies that the CMCE not only records the front and side view profiles at the same time, but also has great image quality at a small size.

Dual-head wireless powered video capsule based on new type of receiving coils

Wireless capsule endoscopy (WCE) has been a great breakthrough in visually detecting the pathological changes of gastrointestinal (GI) wall, but the limit of viewing angle and power by batteries still hinder the wide application of WCE. In order to address these shortcomings, a dual-head video capsule system based on new type of receiving coils is presented. First, the dual-head video capsule system is designed, which could capture images of the whole GI tract in two channels, transforming the images into NTSC videos at a frame rate of 30 f s(-1) and transmitting the signals outside the body. Second, the wireless power transmission platform with new type of receiving coils is established to provide at least 108 mW of continuous, stable energy for the capsule. Then a prototype was fabricated and applied in animal experiments. The designed dual-head video capsule system is proved to be feasible and a potential solution for future clinical application.

Design of endoscopic micro-robotic end effectors: safety and performance evaluation based on physical intestinal tissue damage characteristics

During the last several years, legged locomotive mechanism has been considered as one of the main self-propelling mechanisms for future endoscopic microrobots due to its superior propulsion efficiency of an endoscopic microrobot inside the intestinal track. Nevertheless, its clinical application has been largely limited since the legged locomotive mechanism utilizes an end effector which has a sharp tip to generate sufficient traction by physically penetrating and interlocking with the intestinal tissue. This can cause excessive physical tissue damage or even complete perforation of the intestinal wall that can lead to abdominal inflammation. Hence, in this work two types of new end effectors, penetration-limited end effector (PLEE) and bi-material structured end effector (BMEE) were specially designed to acquire high medical safety as well as effective traction generation performance. The microscopic end effector specimens were fabricated with micro-wire electric discharge machining process. Traction generation performance of the end effectors was evaluated by direct measurement of resistance forces during contact-sliding tests using a custom-built contact-sliding tester. The safety of the end effector design was evaluated by examination of microscopic intestinal tissue damage using a scanning electron microscope (SEM). Physical damage characteristics of the intestinal tissue and related contact physics of the end effectors were discussed. From the results, the end effectors were evaluated with respect to their prospects in future medical applications as safe end effectors as well as micro-surgical tools.

A real-time localization system for an endoscopic capsule using magnetic sensors

Magnetic sensing technology offers an attractive alternative for in vivo tracking with much better performance than RF and ultrasound technologies. In this paper, an efficient in vivo magnetic tracking system is presented. The proposed system is intended to localize an endoscopic capsule which delivers biomarkers around specific locations of the gastrointestinal (GI) tract. For efficiently localizing a magnetic marker inside the capsule, a mathematical model has been developed for the magnetic field around a cylindrical magnet and used with a localization algorithm that provides minimum error and fast computation. The proposed tracking system has much reduced complexity compared to the ones reported in the literature to date. Laboratory tests and in vivo animal trials have demonstrated the suitability of the proposed system for tracking a magnetic marker with expected accuracy.

Intestinal biomechanics simulator for robotic capsule endoscope validation

This work describes the development and validation of a novel device which simulates important forces experienced by Robotic Capsule Endoscopes (RCE) in vivo in the small intestine. The purpose of the device is to expedite and lower the cost of RCE development. Currently, there is no accurate in vitro test method nor apparatus to validate new RCE designs; therefore, RCEs are tested in vivo at a cost of ∼$1400 per swine test. The authors have developed an in vitro RCE testing device which generates two peristaltic waves to accurately simulate the two biomechanical actions of the human small intestine that are most relevant to RCE locomotion: traction force and contact force. The device was successfully calibrated to match human physiological ranges for traction force (4-40 gf), contact force (80-500 gf) and peristaltic wave propagation speed (0.08-2 cm s(-1)) for a common RCE capsule geometry of 3.5 cm length and 1.5 cm diameter.

Robotics in Colonoscopy

Colorectal cancer is the second leading cause of mortality in men and women in the United States. While there is a definite advantage regarding the use of colonoscopies in screening, there is still a lack of widespread acceptance of colonoscopy use in the general public. This is evident by the fact that up to 75% of patients diagnosed with colorectal cancer present with locally advanced disease. In order to make colonoscopy and in turn colorectal cancer screening a patient friendly and a comfortable test some changes in tool are necessary. The conventional colonoscope has not changed much since its development. There are several new advances in colorectal screening practices. One of the most promising new advances is the advent of robotic endoscopic techniques.

Implantable photonic devices for improved medical treatments

An evolving area of biomedical research is related to the creation of implantable units that provide various possibilities for imaging, measurement, and the monitoring of a wide range of diseases and intrabody phototherapy. The units can be autonomic or built-in in some kind of clinically applicable implants. Because of specific working conditions in the live body, such implants must have a number of features requiring further development. This topic can cause wide interest among developers of optical, mechanical, and electronic solutions in biomedicine. We introduce preliminary clinical trials obtained with an implantable pill and devices that we have developed. The pill and devices are capable of applying in-body phototherapy, low-level laser therapy, blue light (450 nm) for sterilization, and controlled injection of chemicals. The pill is also capable of communicating with an external control box, including the transmission of images from inside the patient’s body. In this work, our pill was utilized for illumination of the sinus-carotid zone in dog and red light influence on arterial pressure and heart rate was demonstrated. Intrabody liver tissue laser ablation and nanoparticle-assisted laser ablation was investigated. Sterilization effect of intrabody blue light illumination was applied during a maxillofacial phlegmon treatment.