Mechanical Attributes of Fractal Dragons

Fractals are ubiquitous natural emergences that have gained increased attention in engineering applications, thanks to recent technological advancements enabling the fabrication of structures spanning across many spatial scales. We show how the geometries of fractals can be exploited to determine their important mechanical properties, such as the first and second moments, which physically correspond to the center of mass and the moment of inertia, using a family of complex fractals known as the dragons

Localization and tracking of robotic endoscopic capsules using multiple positron emission markers

Wireless capsule endoscope (WCE) is a first-line medical tool for the diagnosis of many gastrointestinal (GI) tract diseases such as obscure gastrointestinal bleeding, Crohn’s disease, small bowel tumors, and Celiac disease. In the past few years, significant research attention has been dedicated to upgrading the WCE from a diagnostic-only tool to an active medical robot having not only diagnostic capabil- ities but also therapeutic functionalities such as biopsy, microsurgery, and targeted drug delivery. One of the major limitations that impedes the development of such a robotic-type endoscope is the lack of a highly accurate localization system. In this thesis, a novel localization method based on tracking multiple positron emis- sion markers is presented. In the method, three spherical markers with diameters of less than 1 mm are embedded in the cover of an endoscopic capsule. Two pairs of gamma ray detector modules are arranged around a patient’s body to detect co- incidence gamma rays emitted from the three markers. The positions of the three markers, which refer to the position and orientation of the capsule, can then be determined using an effective tracking algorithm. The algorithm consists of four consecutive steps: a method to remove corrupted data, an initialization method, a clustering method based on the Fuzzy C-means clustering algorithm, and a failure prediction method

A review of localization systems for robotic endoscopic capsules

Obscure gastrointestinal (GI) bleeding, Crohn disease, Celiac disease, small bower tumors, and other disorders that occur in the GI tract have always been challenging to be diagnosed and treated due to the inevitable difficulty in accessing such a complex environment within the human body. With the invention of wireless capsule endoscope, the next generation of the traditional cabled endoscope, not only a dream has come true for the patients who have experienced a great discomfort and unpleasantness caused by the conventional endoscopic method, but also a new research field has been opened to develop a complete miniature robotic device that is swallowable and has full functions of diagnosis and treatment of the GI diseases. However, such an ideal device needs to be equipped with a highly accurate localization system to be able to exactly determine the location of lesions in the GI tract and provide essential feedback to an actuationmechanism controlling the device’s movement. This paper presents a comprehensive overview of the localization systems for robotic endoscopic capsules, for which the motivation, challenges, and possible solutions of the proposed localization methods are also discussed

Modeling and experimental investigation of rotational resistance of a spiral-type robotic capsule inside a real intestine

In this study, the rotational resistance of a spiral-type capsule rotating inside a small intestine is investigated by in vitro experiments and analytical modeling, on which a limited literature is available. The results presented exhibit viscoelastic nature of the intestinal tissue. The significance of various spiral structures and rotating speeds is quantitatively evaluated from the propulsion point of view. Also, an analytical torque model is proposed and subsequently validated. The close match between the experimental results and numerical results from the model shows that the model is reasonably accurate to estimate the rotational resistance torque of the small intestine. Both the experimental and modeling works provide a useful guide to determine the torque required for a spiral-type endoscopic capsule operating in a \u27really\u27 small intestine. Therefore, the proposed torque model can be used in the design and optimization of in-body robotic systems, which can remotely be articulated using magnetic actuation

Modeling and experimental investigation on the mechanical behavior of a spiral-type capsule in the small intestine

This paper reports on the study of the behavior of the viscoelastic contact between a spiral-type capsule and the small intestine. Both 2D and 3D simulations show that the traction force, which is due to the pressure difference between the two sides of the spirals, is velocity dependent. With an increase in the sliding velocity, the traction force decreases initially due to the reduced stress relaxation. However, if the velocity reaches some certain magnitude, the reduction in the stress becomes negligibly small. The traction force starts to increase because of the higher stress coming from the higher strain rates. The experimental torque and force measurements were taken for the capsules with different cross-section profiles. The results show that the traction force can be raised by carving grooves on the spirals\u27 surface or using a higher and narrower spiral structure. The difference between the mechanical behaviors of a rotating-only capsule and a rotating-and-translating capsule were experimentally studied and explained in detail. The results show that a rotating-and-advancing capsule gets slightly more resistive torque than a rotating-only capsule

Magnetic propulsion of a spiral-type endoscopic microrobot in a real small intestine

This paper reports on the magnetic propulsion of a spiral-type endoscopic mircorobot in a real small intestine. Magnetic modeling was carried out to design and commission an external electromagnetic system, which wirelessly provides power to the robotic agent. The capsules with different spiral structures were magnetically propelled inside a segment of porcine small intestine. From the results, it is shown that the propulsive velocities of the tested capsules are in the range of 2.5 ~ 35 mm/s when rotating frequencies varying between 1 ~ 5 Hz are applied. Among all the capsules prepared for this study, the capsule No. 5, with one spiral and a helical angle of 20° and spiral height of 1 mm, shows the best performance. The effects of the spiral parameters, such as helical angle, number of spirals and spiral height, are evaluated by using the propulsion velocity and the slip ratio as the evaluation criteria

Concept and simulation study of a novel localization method for robotic endoscopic capsules using multiple positron emission markers

Purpose: Over the last decade, wireless capsule endoscope has been the tool of choice for noninvasive inspection of the gastrointestinal tract, especially in the small intestine. However, the latest clinical products have not been equipped with a sufficiently accurate localization system which makes it difficult to determine the location of intestinal abnormalities, and to apply follow-up interventions such as biopsy or drug delivery. In this paper, the authors present a novel localization method based on tracking three positron emission markers embedded inside an endoscopic capsule. Methods: Three spherical 22Na markers with diameters of less than 1 mm are embedded in the cover of the capsule. Gamma ray detectors are arranged around a patient body to detect coincidence gamma rays emitted from the three markers. The position of each marker can then be estimated using the collected data by the authors\u27 tracking algorithm which consists of four consecutive steps: a method to remove corrupted data, an initialization method, a clustering method based on the Fuzzy C-means clustering algorithm, and a failure prediction method. Results: The tracking algorithm has been implemented in MATLAB utilizing simulation data generated from the Geant4 Application for Emission Tomography toolkit. The results show that this localization method can achieve real-time tracking with an average position error of less than 0.4 mm and an average orientation error of less than 2°. Conclusions: The authors conclude that this study has proven the feasibility and potential of the proposed technique in effectively determining the position and orientation of a robotic endoscopic capsule

Wireless Endoscopy

Wireless endoscopy device is a miniature medical device that travels through the digestive system to collect images or physiological data and transfers them to an external console worn by patients or to a nearby TV/computer for display and monitoring. The current commercial devices have a dimension of approximately 11 x 26 mm with the shape of a pill so as to reach areas such as the small intestine to obtain video images. These devices record and transmit images over approximately an eight hour journey through the gastrointestinal (GI) tract. A video-based capsule device produces a large amount of data from high-resolution cameras, which is delivered over a high capacity wireless link. The commercially available capsules operate based on passive motion with no control over its position or orientation. These devices operate using small batteries with limited energy source. This article discusses implementation issues and presents details of techniques for design of wireless capsule systems. In addition, it outlines new studies involving motion control, localization and wireless energy transfer to increase the battery life of current wireless capsule devices. These new features will enable the next generation wireless capsule endoscopy devices to actively navigate within the GI tract of the human body and enable new therapeutic operations. Finally, the limitations of current devices are discussed and future directions and design challenges are highlighted for designers and researchers