Future of capsule endoscopy

Shape memory alloy-based biopsy device for active locomotive intestinal capsule endoscope

Recently, capsule endoscopes have been used for diagnosis in digestive organs. However, because a capsule endoscope does not have a locomotive function, its use has been limited to small tubular digestive organs, such as small intestine and esophagus. To address this problem, researchers have begun studying an active locomotive intestine capsule endoscope as a medical instrument for the whole gastrointestinal tract. We have developed a capsule endoscope with a small permanent magnet that is actuated by an electromagnetic actuation system, allowing active and flexible movement in the patient's gut environment. In addition, researchers have noted the need for a biopsy function in capsule endoscope for the definitive diagnosis of digestive diseases. Therefore, this paper proposes a novel robotic biopsy device for active locomotive intestine capsule endoscope. The proposed biopsy device has a sharp blade connected with a shape memory alloy actuator. The biopsy device measuring 12 mm in diameter and 3 mm in length was integrated into our capsule endoscope prototype, where the device's sharp blade was activated and exposed by the shape memory alloy actuator. Then the electromagnetic actuation system generated a specific motion of the capsule endoscope to extract the tissue sample from the intestines. The final biopsy sample tissue had a volume of about 6 mm(3), which is a sufficient amount for a histological analysis. Consequently, we proposed the working principle of the biopsy device and conducted an in-vitro biopsy test to verify the feasibility of the biopsy device integrated into the capsule endoscope prototype using the electro-magnetic actuation system.

Computerized 3-dimensional localization of a video capsule in the abdominal cavity: validation by digital radiography

BACKGROUND

Wireless video capsule endoscopy allows the noninvasive visualization of the small intestine. Currently, capsules do not provide localization information while traversing the GI tract.

OBJECTIVE

To report on the radiological validation of 3-dimensional localization software incorporated in a newly developed capsule. By using radiofrequency transmission, the software measures the strength of the capsule's signal to locate the position of the capsule.

SETTING

This study was performed at the University of Massachusetts Medical Center, Worcester, Mass.

PATIENTS

Thirty healthy volunteers consented to the experimental procedure.

DESIGN

After ingestion of the capsule, subjects had 5 sets of anteroposterior and lateral radiographs taken every 30 minutes while the software calculated the position of the capsule. By using the radiographs, we calculated the location of the capsule in the abdominal cavity and compared the results with those generated by the software.

RESULTS

Average error (and standard deviation) among the 3-dimensional coordinates was X, 2.00 cm (1.64); Y, 2.64 cm (2.39); and Z, 2.51 cm (1.83). The average total spatial error among all measurements was 13.26 cm(3) (22.72). There was a correlation between increased subject body mass index and the 3-dimensional software measurement error.

LIMITATIONS

This study was performed in healthy volunteers and needs further validation in patients with small intestinal disorders.

CONCLUSIONS

The new 3-dimensional software provides localization of the capsule consistent with radiological observations. However, further validation of the software's clinical utility is required with a prospective clinical trial.

Biopsy using a magnetic capsule endoscope carrying, releasing, and retrieving untethered microgrippers

This paper proposes a new wireless biopsy method where a magnetically actuated untethered soft capsule endoscope carries and releases a large number of thermo-sensitive, untethered microgrippers (μ-grippers) at a desired location inside the stomach and retrieves them after they self-fold and grab tissue samples. We describe the working principles and analytical models for the μ-gripper release and retrieval mechanisms, and evaluate the proposed biopsy method in ex vivo experiments. This hierarchical approach combining the advanced navigation skills of centimeter-scaled untethered magnetic capsule endoscopes with highly parallel, autonomous, submillimeter scale tissue sampling μ-grippers offers a multifunctional strategy for gastrointestinal capsule biopsy.

3-D Localization Method for a Magnetically Actuated Soft Capsule Endoscope and Its Applications

In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0-3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis.

Efficient linear algorithm for magnetic localization and orientation in capsule endoscopy

To build a new wireless robotic capsule endoscope with external guidance for controllable GI tract examination, a sensing system is required for tracking the capsule's 3D location and 2D orientation. An appropriate sensing approach is to enclose a small permanent magnet in the capsule so as to establish a static magnetic field around. With the magnetic sensors outside the patient's body, some parameters related to this magnetic field can be detected, and the capsule's location and orientation can be calculated using an appropriate algorithm. In this paper, a linear algorithm is proposed to provide faster, more reliable computation, compared to the nonlinear algorithms. The results of simulation and real experiment show that satisfactory localization and orientation accuracy can be achieved using a sensor array with enough number of 3-axis sensors.

Capsule endoscopy: from current achievements to open challenges

Wireless capsule endoscopy (WCE) can be considered an example of disruptive technology since it represents an appealing alternative to traditional diagnostic techniques. This technology enables inspection of the digestive system without discomfort or need for sedation, thus preventing the risks of conventional endoscopy, and has the potential of encouraging patients to undergo gastrointestinal (GI) tract examinations. However, currently available clinical products are passive devices whose locomotion is driven by natural peristalsis, with the drawback of failing to capture the images of important GI tract regions, since the doctor is unable to control the capsule's motion and orientation. To address these limitations, many research groups are working to develop active locomotion devices that allow capsule endoscopy to be performed in a totally controlled manner. This would enable the doctor to steer the capsule towards interesting pathological areas and to accomplish medical tasks. This review presents a research update on WCE and describes the state of the art of the basic modules of current swallowable devices, together with a perspective on WCE potential for screening, diagnostic, and therapeutic endoscopic procedures.

A Robotic Biopsy Device for Capsule Endoscopy

This paper introduces a robotic biopsy device for capsule endoscopes. The proposed device consists of three modules for the complete process of biopsy, which includes monitoring the intestinal wall by a tissue monitoring module (TMM), aligning onto a polyp by an anchor module (AM), and sampling of the polyp tissue by a biopsy module (BM). The TMM utilizes a trigonal mirror as well as an on-board camera; since the TMM continuously takes images through lateral apertures, an operator such as a medical doctor is able to anchor the capsule endoscope onto the polyp and biopsy it with the visual feedback in real-time. When the operator finds a polyp using the TMM and the frontal camera of a capsule endoscope, then the AM is used to approach the polyp for biopsy. When the AM is in use, outriggers are extruded by shape-memory-alloy (SMA) springs, which results in the swelling of capsule endoscope body. In addition, an alignment module, which is a part of the AM, rotates the body of the capsule endoscope such that the biopsy razor can be aligned onto the polyp. Then, the BM excises a part of the polyp and seals the aperture, and the capsule endoscope continues exploring the intestine. The concept and working principles of the proposed device are introduced in this paper and are verified by a prototype that successfully integrates the three modules.

EFFICIENT MAGNETIC LOCALIZATION AND ORIENTATION TECHNIQUE FOR CAPSULE ENDOSCOPY

To build a new wireless robotic capsule endoscope with external guidance for controllable and interactive GI tract examination, a sensing system is needed for tracking 3D location and 2D orientation of the capsule endoscope movement. An appropriate sensing method is to enclose a small permanent magnet in the capsule. The intensities of the magnetic field produced by the magnet in different spatial points can be measured by the magnetic sensors outside the patient's body. With the sensing data of magnetic sensor array, the 3D location and 2D orientation of the capsule can be calculated. Higher calculation accuracy can be obtained if more sensors and optimal algorithm are applied. In this paper, different nonlinear optimization algorithms were evaluated to solve the magnet's 5D parameters, e.g. Powell's, Downhill Simplex, DIRECT, Multilevel Coordinate Search, and Levenberg Marquardt method. We have found that Levenberg-Marquardt method provides satisfactory calculation accuracy and faster speed. Simulations were done for investigating the de-noise ability of this algorithm based on different sensor arrays. Also the real experiment shows that the results are satisfactory with high accuracy (average localization error is 5.6 mm).

Capsule endoscopy: Future horizons

Capsule endoscopy (CE) was launched at the beginning of this millennium and has since become a well established methodology for evaluating the entire small bowel for manifold pathologies. CE far exceeded early expectations by providing a tool for establishing the correct diagnosis for elusive gastrointestinal (GI) conditions such as obscure GI bleeding, Crohn’s disease, polyposis syndrome and others. Contemporary CE, like radiology, gives results that can only be read, unlike conventional endoscopic procedures which enable concomitant biopsy when indicated. This is one of the major limitations of the technique. The ideal CE should improve the quality of the image and have a faster frame rate than the currently available one. There should be a therapeutic capsule capable of performing a biopsy, aspirating fluid, delivering drugs as well as measuring the motility of the small bowel wall. Another major leap forward would be the capability of remote control of the capsule’s movement in order to navigate it to reach designated anatomical areas for carrying out a variety of therapeutic options. Technology for improving the capability of the future generation capsule is almost within grasp and it would not be surprising to witness the realization of these giant steps within the coming decade.

The future of wireless capsule endoscopy

We outline probable and possible developments with wireless capsule endoscopy. It seems likely that capsule endoscopy will become increasingly effective in diagnostic gastrointestinal endoscopy. This will be attractive to patients especially for cancer or varices detection because capsule endoscopy is painless and is likely to have a higher take up rate compared to conventional colonoscopy and gastroscopy. Double imager capsules with increased frame rates have been used to image the esophagus for Barrett’s and esophageal varices. The image quality is not bad but needs to be improved if it is to become a realistic substitute for flexible upper and lower gastrointestinal endoscopy. An increase in the frame rate, angle of view, depth of field, image numbers, duration of the procedure and improvements in illumination seem likely. Colonic, esophageal and gastric capsules will improve in quality, eroding the supremacy of flexible endoscopy, and become embedded into screening programs. Therapeutic capsules will emerge with brushing, cytology, fluid aspiration, biopsy and drug delivery capabilities. Electrocautery may also become possible. Diagnostic capsules will integrate physiological measurements with imaging and optical biopsy, and immunologic cancer recognition. Remote control movement will improve with the use of magnets and/or electrostimulation and perhaps electromechanical methods. External wireless commands will influence capsule diagnosis and therapy and will increasingly entail the use of real-time imaging. However, it should be noted that speculations about the future of technology in any detail are almost always wrong.

Diamagnetically-stabilized levitation control of an intraluminal magnetic capsule

Controlled navigation promotes full utilization of capsule endoscopy for reliable real-time diagnosis in the gastrointestinal (GI) tract, but intermittent natural peristalsis can disturb the navigational control, destabilize the capsule and take it out of levitation. A real-size magnetic navigation system that can handle peristaltic forces of up to 1.5 N was designed utilizing the computer-aided design (CAD) system Maxwell 3D (Ansoft, Pittsburg, PA), and was verified using a small-size physical experimental setup. The proposed system contains a pair of 50-cm in diameter, 10,000-turns copper electromagnets with a 10-cm by 10-cm ferrous core driven by currents of up to 300 Amperes and can successfully maintain position control over the levitating capsule during peristalsis. The addition of Bismuth diamagnetic casing for stabilizing the levitating capsule was also studied.

Wireless capsule endoscopy: from diagnostic devices to multipurpose robotic systems

In the recent past, the introduction of miniaturised image sensors with low power consumption, based on complementary metal oxide semiconductor (CMOS) technology, has allowed the realisation of an ingestible wireless capsule for the visualisation of the small intestine mucosa. The device has received approval from Food and Drug Administration and has gained momentum since it has been more successful than traditional techniques in the diagnosis of small intestine disorders. In 2004 an esophagus specific capsule was launched, while a solution for colon is still under development. However, present solutions suffer from several limitations: they move passively by exploiting peristalsis, are not able to stop intentionally for a prolonged diagnosis, they receive power from an internal battery with short length, and their usage is restricted to one organ, either small bowel or esophagus. However the steady progresses in many branches of engineering, including microelectromechanical systems (MEMS), are envisaged to affect the performances of capsular endoscopy. The near future foreshadows capsules able to pass actively through the whole gastrointestinal tract, to retrieve views from all organs and to perform drug delivery and tissue sampling. In the long term, the advent of robotics could lead to autonomous medical platforms, equipped with the most advanced solutions in terms of MEMS for therapy and diagnosis of the digestive tract. In this review, we discuss the state of the art of wireless capsule endoscopy (WCE): after a description on the current status, we present the most promising solutions.

Diagnosis of small-bowel diseases in the era of capsule endoscopy

Capsule endoscopy is a major breakthrough in gastrointestinal endoscopy and is a first-line tool to detect abnormalities of the small bowel, in up to 50% of patients, intestinal disorders are not associated with any physical findings or positive tests. Indications, yield and impact on patient management of this method of diagnosing small-bowel diseases are analyzed critically in light of current scientific knowledge.

The European experience with double-balloon enteroscopy: indications, methodology, safety, and clinical impact

BACKGROUND

Double-balloon enteroscopy (DBE) is a new technique that allows high-resolution visualization, biopsies, and therapeutic interventions in all segments of the GI tract. The objective of the study was to evaluate the indications, the safety, and the clinical impact of DBE.

METHODS

This is a retrospective analysis conducted at 4 European medical centers. A total of 62 patients with suspected or documented small-bowel diseases were investigated by DBE. A total of 89 procedures were performed (26 and 9 patients from the oral or the anal route, respectively; 27 patients from both). The main outcome measurements were complications, depth and time of insertion, diagnostics, and therapeutics rates.

RESULTS

No complications occurred. Mean time was 70 +/- 30 minutes and 90 +/- 35 minutes from the oral and the anal route, respectively. Length of insertion was 254 +/- 174 cm beyond the pylorus, 180 +/- 150 cm beyond the ileocecal valve, whereas the entire small bowel was completely explored in 10 patients. DBE was diagnostic in 80% of the patients: in 29 of 33 of patients with GI bleeding, in one of 5 patients with iron deficiency anemia and positive fecal occult blood testing, in 3 of 5 patients with chronic diarrhea, in two of 3 patients with abdominal pain, in two of 3 patients with GI cancer (follow-up), in all patients with suspected or refractory celiac disease, and in two of 3 patients with Crohn's disease. Treatment was performed in 41.9% of patients (22 polyps and 29 angioectesias).

CONCLUSIONS

DBE is a safe and feasible diagnostic and therapeutic tool for suspected or documented small-bowel diseases. At present, the best candidates for the procedure appear to be those with obscure GI bleeding.