A Review of Localization Systems for Robotic Endoscopic Capsules
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paper_title: At a watershed? Technical developments in wireless capsule endoscopy.

paper_content:

This article reviews some of the technical developments that allowed the introduction of the wireless capsule 10 years ago into human usage. Technical advances and commercial competition have substantially improved the performance of clinical capsule endoscopy, especially in optical quality. Optical issues including the airless environment, depth of focus, dome reflection, the development of white light light-emitting diodes, exposure length and the advent of adaptive illumination are discussed. The competition between charge coupled devices and complementary metal oxide silicone technologies for imaging, lens improvements and the requirements for different frame rates and their associated power management strategies and battery type choices and the introduction of field enhancement methods into commercial capsule technology are considered. Capsule technology stands at a watershed. It is mainly confined to diagnostic small intestinal imaging. It might overtake other forms of conventional diagnostic endoscopy, especially colonoscopy but also gastroscopy and esophagoscopy but has to improve both technically and compete in price. It might break out of its optical diagnostic confinement and become a therapeutic modality. To make this leap there have to be several technical advances especially in biopsy, command, micromechanical internal movements, remote controlled manipulation and changes in power management, which may include external power transmission.
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paper_title: Recent Patents on Wireless Capsule Endoscopy

paper_content:

Wireless capsule endoscopy is a medical procedure which has revolutionized endoscopy as it has enabled for the first time a painless inspection of the small intestine. The procedure was unveiled in 2000 and is based on a vitamin- size pill which captures images of the digestive tract while it is transported passively by peristalsis. The device consists of an image sensor, an illumination module, a radio-frequency transmitter and a battery. Wireless capsule endoscopy is a novel breakthrough in the biomedical industry and future progresses in key technologies are expected to drive the development of the next generation of such devices. Therefore, the purpose of this review is to illustrate the most recent and significant inventions patented from 2005 to present in those areas concerning measurement of human body parameters, advanced imaging features, localization, energy management and active propulsion. Finally, the manuscript reports a discussion on current and future developments in wireless capsule endoscopy.
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paper_title: Capsule Endoscopy: From Current Achievements to Open Challenges

paper_content:

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.
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paper_title: Wireless capsule endoscopy

paper_content:

With the introduction of the flexible fiber optic endoscope in 1950s visualization of the esophagus, stomach, upper small bowel and colon became possible. The flexible shaft of the instrument carried the fiber optic light bundles, power and the optical elements. It also contained cables, which allowed for control over the direction of the instrument. Therefore, the instrument was of relatively large diameter, making gastroscopy, small bowel endoscopy and colonoscopy an uncomfortable procedure requiring sedation. Recent advances in development of low power complementary metal‐oxide silicon (CMOS) imagers, mixed signal application specific integrated circuit (ASICs) and white light emitting diodes (LEDs) made possible development of a new type of endoscope – the swallowable video capsule. We describe the development of a video‐telemetry capsule endoscope that is small enough to swallow (11×26 mm) and has no external wires, fiber optic bundles or cables. Extensive clinical and healthy volunteer trials have p...
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paper_title: Wireless capsule endoscopy

paper_content:

Gastroscopy, small bowel endoscopy, and colonoscopy are uncomfortable because they require comparatively large diameter flexible cables to be pushed into the bowel, which carry light by fibreoptic bundles, power, and video signals. Small bowel endoscopy is currently especially limited by problems of discomfort and failure to advance enteroscopes far into the small bowel. There is a clinical need for better methods to examine the small bowel especially in patients with recurrent gastrointestinal bleeding from this site.
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paper_title: Upper Gastrointestinal Endoscopy: Current Status

paper_content:

Esophagogastroduodenoscopy occupies a predominant position in the diagnostic evaluation and therapeutic management of foregut disease. The safety, anatomic refinement, and tissue sampling capabilities offered by endoscopic examination support its use as a premier diagnostic tool. An increasingly diverse and ingenious set of endoscopically delivered tools are available to expand the diagnostic capability, and extend the therapeutic application of esophagogastroduodenoscopy to a wide range of pathology, both benign and neoplastic. Comparative outcome data support the utility of therapeutic esophagogastroduodenoscopy in the management of upper gastrointestinal bleeding and the palliative management of foregut neoplasia. Endoscopically delivered therapies may have an increasing role in the management of gastroesophageal reflux disease in the future, and the development of endoluminal ultrasound has added a whole new dimension to endoscopic diagnostic and, potentially, therapeutic capability. This review highlights the current status of esophagogastroduodenoscopy in the diagnosis and management of upper gastrointestinal pathology.
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paper_title: Capsule endoscopy—A mechatronics perspective

paper_content:

The recent advances in integrated circuit technology, wireless communication, and sensor technology have opened the door for development of miniature medical devices that can be used for enhanced monitoring and treatment of medical conditions. Wireless capsule endoscopy is one of such medical devices that has gained significant attention during the past few years. It is envisaged that future wireless capsule endoscopies replace traditional endoscopy procedures by providing advanced functionalities such as active locomotion, body fluid/tissue sampling, and drug delivery. Development of energy-efficient miniaturized actuation mechanisms is a key step toward achieving this goal. Here, we review some of the actuators that could be integrated into future wireless capsules and discuss the existing challenges.
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paper_title: A further step beyond wireless capsule endoscopy

paper_content:

Purpose – Aims to report on a new trend of research and development in the wireless capsule endoscope.Design/methodology/approach – Presents a conceptual design of a wireless capsule endoscope having new features like navigation control, self‐propulsion, higher rate image transmission, acquisition of samples, application of medications and so forth.Findings – The basic principle has been verified by experiments. Seems promising.Research limitations/implications – Yet to need a lot of effort for commercialization.Practical implications – If successful, it will provide another way of least invasive medical treatment that must reduce pain of patients drastically.Originality/value – Taking advantage of the state‐of‐the‐art micro‐technology it suggests a further step beyond the current wireless capsule endoscope.
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paper_title: Capsule endoscopy: progress update and challenges ahead

paper_content:

Capsule endoscopy (CE) enables remote diagnostic inspection of the gastrointestinal tract without sedation and with minimal discomfort. Initially intended for small-bowel endoscopy, modifications to the original capsule have since been introduced for imaging of the esophagus and the colon. This review presents a research update on CE. Emphasis is placed on PillCam SB, PillCam ESO, and PillCam COLON (Given Imaging, Yoqneam, Israel) since the majority of published studies have investigated these devices. Discussion of initial reports on competing devices, such as EndoCapsule (Olympus, Tokyo, Japan) and MiroCam (IntroMedic Co., Seoul, Republic of Korea) are also included. The last section of this review outlines ongoing research and development directed at the identification of capsule location, control of capsule movement and expansion of the capability of microcameras to enhance the diagnostic power of CE. Research efforts aimed at endowing the capsule with a range of functionalities are also discussed, from tissue sampling for biopsy to optical biopsy and, in some cases, actual treatment (interventional CE), so that CE may ultimately replace both diagnostic and interventional flexible endoscopy.
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paper_title: Wireless capsule endoscopy: from diagnostic devices to multipurpose robotic systems

paper_content:

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.
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paper_title: Swallowable medical devices for diagnosis and surgery: The state of the art

paper_content:

Abstract The first wireless camera pills created a revolutionary new perspective for engineers and physicians, demonstrating for the first time the feasibility of achieving medical objectives deep within the human body from a swallowable, wireless platform. The approximately 10 years since the first camera pill has been a period of great innovation in swallowable medical devices. Many modules and integrated systems have been devised to enable and enhance the diagnostic and even robotic capabilities of capsules working within the gastrointestinal (GI) tract. This article begins by reviewing the motivation and challenges of creating devices to work in the narrow, winding, and often inhospitable GI environment. Then the basic modules of modern swallowable wireless capsular devices are described, and the state of the art in each is discussed. This article is concluded with a perspective on the future potential of swallowable medical devices to enable advanced diagnostics beyond the capability of human visual perception, and even to directly deliver surgical tools and therapy non-invasively to interventional sites deep within the GI tract.
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paper_title: Novel electromagnetic actuation system for three-dimensional locomotion and drilling of intravascular microrobot

paper_content:

Various types of actuation methods for microrobots have been proposed. Among the actuation methods, electromagnetic based actuation (EMA) has been considered a promising actuation mechanism. In this paper, a new EMA system for three-dimensional (3D) locomotion and drilling of the microrobot is proposed. The proposed system consists of four fixed coil pairs and one rotating coil pair. In detail, the coil system has three pairs of stationary Helmholtz coil, a pair of stationary Maxwell coil and a pair of rotating Maxwell coil. The Helmholtz coil pairs can magnetize and align the microrobot to the desired direction and the two pairs of Maxwell coil can generate the propulsion force of the microrobot. In addition, the Helmholtz coil pairs can rotate the microrobot about a desired axis. The rotation of the microrobot is a drilling action through an occlusion in a vessel. Through various experiments, the 3D locomotion and drilling of the microrobot by using the proposed EMA system are demonstrated. Compared with other EMA systems, the proposed system can provide the advantages of consecutive locomotion and drilling of the microrobot.
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paper_title: Position and orientation detection of capsule endoscopes in spiral motion

paper_content:

In this paper, a position and orientation detection method for the capsule endoscopes devised to move through the human digestive organs in spiral motion, is introduced. The capsule is equipped with internal magnets and flexible threads on their outer shell. It is forced to rotate by an external rotating magnetic field that produces a spiral motion. As the external magnetic field is generated by rotating a permanent magnet, the 3-axes Cartesian coordinate position and 3-axes orientation of the capsule endoscopes can be measured by using only 3 hall-effect sensors orthogonally installed inside the capsule. However, in this study, an additional hall-effect sensor is employed along the rotating axis at a symmetrical position inside the capsule body to enhance measurement accuracy. In this way, the largest position detection error appearing along the rotating axis of the permanent magnet could be reduced to less than 15mm, when the relative position of the capsule endoscope to the permanent magnet is changed from 0mm to 50mm in the X-direction, from −50mm to +50mm in the Y-direction and from 200mm to 300mm in the Z-direction. The maximum error of the orientation detection appearing in the pitching direction ranged between −4° and +15°.
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paper_title: A flexible chain-based screw propeller for capsule endoscopes

paper_content:

In this paper, a new type of screw propeller for capsule endoscopes is introduced whose rotation motion is enforced by magnetic forces between an armature magnet inside the capsule and an external rotating permanent magnet working like an AC stator. The screw propeller consists of flexible threads attached on the capsule body. The spiral angle of the flexible threads switches automatically due to the friction force between intestine wall and the capsule body when the rotating direction of the capsule body is reversed. Therefore, the moving direction of the capsule is independent of the rotating direction of the capsule body. This will help the capsule advance especially in curved tracts by changing its effective thread angle for reduction of friction torque. In order to investigate main parameters that influence the performance of the new screw propeller, we evaluated the speed of the capsule with various shapes and sizes of the flexible threads, changing the parameters such as rotational speed of the external permanent magnet, distance between the external magnet and the armature magnet inside the capsule, and viscosity of lubrication oil in artificial intestine tract. The speed of the capsule with the flexible screw propeller was mainly dependent on the shape of threads. Also, the distance between the magnets highly influenced the speed of the capsule since thrust force of the capsule was dependent on it. On the contrary, rotational speed and oil viscosity insignificantly contributed to the speed of the capsule. Especially in curved tracts, the effective thread angle of the screw propeller which could be changed by its rotation direction played a great role in advancing the capsule efficiently.
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paper_title: Volumetric characterization of the Aurora magnetic tracker system for image-guided transorbital endoscopic procedures.

paper_content:

In some medical procedures, it is difficult or impossible to maintain a line of sight for a guidance system. For such applications, people have begun to use electromagnetic trackers. Before a localizer can be effectively used for an image-guided procedure, a characterization of the localizer is required. The purpose of this work is to perform a volumetric characterization of the fiducial localization error (FLE) in the working volume of the Aurora magnetic tracker by sampling the magnetic field using a tomographic grid. Since the Aurora magnetic tracker will be used for image-guided transorbital procedures we chose a working volume that was close to the average size of the human head. A Plexiglass grid phantom was constructed and used for the characterization of the Aurora magnetic tracker. A volumetric map of the magnetic space was performed by moving the flat Plexiglass phantom up in increments of 38.4 mm from 9.6 mm to 201.6 mm. The relative spatial and the random FLE were then calculated. Since the target of our endoscopic guidance is the orbital space behind the optic nerve, the maximum distance between the field generator and the sensor was calculated depending on the placement of the field generator from the skull. For the different field generator placements we found the average random FLE to be less than 0.06 mm for the 6D probe and 0.2 mm for the 5D probe. We also observed an average relative spatial FLE of less than 0.7 mm for the 6D probe and 1.3 mm for the 5D probe. We observed that the error increased as the distance between the field generator and the sensor increased. We also observed a minimum error occurring between 48 mm and 86 mm from the base of the tracker.
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paper_title: Diamagnetically-stabilized levitation control of an intraluminal magnetic capsule

paper_content:

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.
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paper_title: Capsule Endoscopy: From Current Achievements to Open Challenges

paper_content:

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.
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paper_title: Remote magnetic manipulation of a wireless capsule endoscope in the esophagus and stomach of humans (with videos).

paper_content:

BACKGROUND ::: Remote manipulation of wireless capsule endoscopes might improve diagnostic accuracy and facilitate therapy. ::: ::: ::: OBJECTIVE ::: To test a new capsule-manipulation system. ::: ::: ::: SETTING ::: University hospital. ::: ::: ::: DESIGN AND INTERVENTIONS ::: A first-in-human study tested a new magnetic maneuverable wireless capsule in a volunteer. A wireless capsule endoscope was modified to include neodymium-iron-boron magnets. The capsule's magnetic switch was replaced with a thermal one and turned on by placing it in hot water. One imager was removed from the PillCam colon-based capsule, and the available space was used to house the magnets. A handheld external magnet was used to manipulate this capsule in the esophagus and stomach. The capsule was initiated by placing it in a microg of hot water. The capsule was swallowed and observed in the esophagus and stomach by using a gastroscope. Capsule images were viewed on a real-time viewer. ::: ::: ::: MAIN OUTCOME MEASUREMENTS ::: The capsule was manipulated in the esophagus for 10 minutes. It was easy to make the capsule turn somersaults and to angulate at the cardioesophageal junction. In the stomach, it was easy to move the capsule back from the pylorus to the cardioesophageal junction and hold/spin the capsule at any position in the stomach. The capsule in the esophagus and stomach did not cause discomfort. ::: ::: ::: LIMITATIONS ::: Magnetic force varies with the fourth power of distance. ::: ::: ::: CONCLUSIONS ::: This study suggests that remote manipulation of a capsule in the esophagus and stomach of a human is feasible and might enhance diagnostic endoscopy as well as enable therapeutic wireless capsule endoscopy.
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paper_title: Novel MIMO 4-DOF position control for Capsule Endoscope

paper_content:

In this paper, a novel actuation system for Wireless Capsule Endoscopes (WCE) based on magnetic levitation is proposed. This study focuses on the design of a multi-input, multi-output (MIMO), controller to maintain a desired position and orientation of the capsule relative to the movable electromagnet frame so that it can navigate the intestine by moving this frame and/or the patient. Tracking algorithms for the linear controller based on pole placement, entire eigenstructure assignment (EEA), and linear quadratic regulator (LQR) techniques are designed and simulated using Matlab/Simulink. Simulation results suggest that the LQR controller can be used for capsule actuation.
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paper_title: Robotic magnetic steering and locomotion of capsule endoscope for diagnostic and surgical endoluminal procedures

paper_content:

This paper describes a novel approach to capsular endoscopy that takes advantage of active magnetic locomotion in the gastrointestinal tract guided by an anthropomorphic robotic arm. Simulations were performed to select the design parameters allowing an effective and reliable magnetic link between the robot end-effector (endowed with a permanent magnet) and the capsular device (endowed with small permanent magnets). In order to actively monitor the robotic endoluminal system and to efficiently perform diagnostic and surgical medical procedures, a feedback control based on inertial sensing was also implemented. The proposed platform demonstrated to be a reliable solution to move and steer a capsular device in a slightly insufflated gastrointestinal lumen.
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paper_title: A Cubic 3-Axis Magnetic Sensor Array for Wirelessly Tracking Magnet Position and Orientation

paper_content:

In medical diagnoses and treatments, e.g., endoscopy, dosage transition monitoring, it is often desirable to wirelessly track an object that moves through the human GI tract. In this paper, we propose a magnetic localization and orientation system for such applications. This system uses a small magnet enclosed in the object to serve as excitation source, so it does not require the connection wire and power supply for the excitation signal. When the magnet moves, it establishes a static magnetic field around, whose intensity is related to the magnet's position and orientation. With the magnetic sensors, the magnetic intensities in some predetermined spatial positions can be detected, and the magnet's position and orientation parameters can be computed based on an appropriate algorithm. Here, we propose a real-time tracking system developed by a cubic magnetic sensor array made of Honeywell 3-axis magnetic sensors, HMC1043. Using some efficient software modules and calibration methods, the system can achieve satisfactory tracking accuracy if the cubic sensor array has enough number of 3-axis magnetic sensors. The experimental results show that the average localization error is 1.8 mm.
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paper_title: Perspective of active capsule endoscope: actuation and localisation

paper_content:

The self-contained wireless capsule endoscope provides non-invasive, painless and effective diagnosis of the diseases in the small intestine. One anticipation is to embed the capsule with therapeutic tools and enable not only diagnosis but also treatment of the GI diseases. Prior to the accomplishment of this objective, controlled movement of the capsule should be achieved first. In this paper, we focused on the actuation and localisation issues of the active capsule endoscope. After a survey on the related work, the challenges were presented and the possible solutions were discussed.
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paper_title: A novel method of three-dimensional localization based on a neural network algorithm

paper_content:

In order to track the three-dimensional position of a non-invasive detecting microcapsule in the alimentary tract, a novel localization method has been developed. Three coils were respectively energized by square wave signals to generate an electromagnetic field. A 3-axis magnetic sensor was sealed in the microcapsule to measure the electromagnetic field strength. Based on the principle of magnetic dipole a corresponding localization model was established. By resolving the localization equations by means of the neural network algorithm, the spatial position of the microcapsule can be obtained. The experiment shows that the localization principle is correct and has high precision. Compared with other methods, this novel method needs no special equipment and after integration the system can be made into a portable type.
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paper_title: Sensor Arrangement Optimization of Magnetic Localization and Orientation system

paper_content:

A magnetic localization and orientation system is used to track the movement of the capsule endoscope during the gastrointestinal examination process. The system is made of a magnetic sensors array collecting the intensity of the magnetic field from a magnet in the capsule. In this paper, we try to optimize the sensor arrangement in the 3D space around the human body, to improve the tracking precision. Different sensor arrangement schemes are evaluated, and the tracking accuracy can be significantly increased with the appropriate arrangement.
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paper_title: Magnetic markers as a noninvasive tool to monitor gastrointestinal transit

paper_content:

A novel method to monitor gastrointestinal transit of solid oral dosage forms or nutrients is presented, providing a simultaneous recording of gastrointestinal motility of the traversed section. Based on the measurement of the magnetic field of an ingested magnetized marker, its location is found by fitting a magnetic dipole field to the measured data. >
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paper_title: An electromagnetic localization method for medical micro-devices based on adaptive particle swarm optimization with neighborhood search

paper_content:

Abstract In order to non-invasively track a medical micro-device in gastrointestinal tract, an alternating electromagnetic tracking method was presented and a prototype was developed. In the tracking method, several energizing coils were excited by time-sharing sinusoidal signal to generate varying magnetic fields by one coil and then another coil. A wireless magnetic sensor measured the magnetic field strength at the location of the micro-device. The root-mean-square value of the magnetic field strength is a high-order nonlinear system of equations with respect to the position and orientation of the micro-device. Based on the adaptive particle swarm optimization (PSO) with neighborhood search, the position and orientation of the micro-device could be obtained. The experimental results show that the tracking method is valid and the modified algorithm succeeds in dealing with the nonlinear system of equations in localization. Comparing to the standard PSO algorithm, it does not require a good initial guess to guarantee convergence. Furthermore, it has high precision and fast convergence.
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paper_title: High-resolution monitoring of the gastrointestinal transit of a magnetically marked capsule.

paper_content:

The purpose of this study was to demonstrate that it is possible to continuously monitor the gastrointestinal transit of magnetically marked, solid, oral dosage forms with multichannel biomagnetic measuring equipment and by magnetic source imaging (MSI) methods. For the investigations presented, a sucrose pellet was coated with powdered magnetite (Fe3O4) in poly(methyl methacrylate). Then, the pellet was enclosed in a capsule prepared from silicone rubber and magnetized to obtain a net magnetic dipole moment. After ingestion of the capsule, its magnetic field distribution over the abdomen was recorded for several time intervals with a 37-channel superconducting quantum interference device (SQUID) magnetometer. At each time point, the position of the capsule within the gastrointestinal tract was calculated from the measured field distribution, assuming a magnetic dipole model. The data presented here demonstrate that with this noninvasive method of magnetic marker monitoring it is possible to investigate the gastrointestinal transit of a solid oral dosage form with a temporal resolution in the order of milliseconds and a spatial resolution within a range of millimeters.
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paper_title: A magnetic tracking system based on highly sensitive integrated hall sensors

paper_content:

A tracking system with five degrees of freedom based on a 2D-array of 16 Hall sensors and a permanent magnet is presented in this paper. The sensitivity of the Hall sensors is increased by integrated micro- and external macro-flux-concentrators. Detection distance larger than 20cm (during one hour without calibration) is achieved using a magnet of 0.2cm3. This corresponds to a resolution of the sensors of 0.05µTrms. The position and orientation of the marker is displayed in real time at least 20 times per second. The sensing system is small enough to be hand-held and can be used in a normal environment. This presented tracking system has been successfully applied to follow a small swallowed magnet through the entire human digestive tube. This approach is extremely promising as a new non-invasive diagnostic technique in gastro-enterology.
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paper_title: A new calibration method for magnetic sensor array for tracking capsule endoscope

paper_content:

To track the movement of wireless capsule endoscope in the human body, we design a magnetic localization and orientation system. In this system, capsule contains a permanent magnet as the movable object. A wearable magnetic sensor array is arranged out of the human body to capture the magnetic signal. This sensor array is composed of magnetic sensors, Honeywell product HMC1043. The variations of magnet field intensity and direction are related to the capsule position and orientation. Therefore, the 3D localization information and 2D orientation parameters of capsule can be computed based on the captured magnetic signals and by applying an appropriate algorithm. In order to initialize the system and improve the tracking accuracy, we propose a calibration technique based on high-accurate localization equipment, FASTRAK. The calibration method includes two steps. Firstly, we acquire the accurate reference data from FASTRAK tracking equipment, and transform them into the position and orientation parameters of the magnet. Secondly, we calculate three important parameters for the sensor calibration: the sensitivity, the center position, and the orientation. Based on the calibration, we can adjust the magnetic localization and orientation system quickly and accurately. The experimental results prove that the calibration method used in our system can improve the system with satisfactory tracking accuracy.
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paper_title: Magnetism and Magnetic Materials

paper_content:

1. Introduction 2. Magnetostatics 3. Magnetism of electrons 4. Magnetism of localized electrons on the atom 5. Ferromagnetism and exchange 6. Antiferromagnetism and other magnetic order 7. Micromagnetism, domains and hysteresis 8. Nanoscale magnetism 9. Magnetic resonance 10. Experimental methods 11. Magnetic materials 12. Applications of soft magnets 13. Applications of hard magnets 14. Spin electronics and magnetic recording 15. Special topics Appendixes Index.
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paper_title: An hybrid localization system based on optics and magnetics

paper_content:

Magnetic tracking systems have been increasing in popularity due to their lower expense and small size of their tracked objects, but they are sensitive to ferromagnetic objects within their work volumes. Optical tracking systems can overcome this disadvantage, however there are some occlusions problem in optical system. Hence, we present a novel hybrid localization system combining optical one and magnetic one. The hybrid localization algorithm will be introduced in this paper. Experiments show that the localization accuracy of optical and magnetic hybrid localizer can be enhanced to some extent.
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paper_title: Efficient magnetic localization and orientation technique for capsule endoscopy

paper_content:

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).
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paper_title: Tracking system with five degrees of freedom using a 2D-array of Hall sensors and a permanent magnet

paper_content:

Abstract Based on a 2D-array of 16 cylindrical Hall sensors and a permanent magnet, a tracking system with five degrees of freedom is analysed in this paper. The system accuracy is studied, including offset drifts, sensitivity mismatches and the number of sensors. A detection distance as large as 14 cm (during 1 h without calibration) is achieved using a magnet of 0.2 cm 3 . The position and orientation of the marker is displayed in real time with a sampling frequency up to 50 Hz. The sensing system is small enough to be hand-held and can be used in a normal environment.
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paper_title: 3D magnetic tracking of a single subminiature coil with a large 2D-array of uniaxial transmitters

paper_content:

A novel system and method for magnetic tracking of a single subminiature coil is described. The novelty of the method consists in employing a large, 8 /spl times/ 8 array of coplanar transmitting coils. This allows us to always keep the receiving coil not far from the wide, flat transmitting array, to increase the signal-to-noise ratio, and to decrease the retransmitted interference. The whole transmitting array, 64 coils, is sequentially activated only at the initiation stage to compute the initial position of the receiving coil. The redundancy in the transmitters number provides fast and unambiguous convergence of the optimization algorithm. At the following tracking stages, a small (8 coils) transmitting subarray is activated. The relatively small subarray size allows us to keep a high update rate and resolution of tracking. For a 50-Hz update rate, the tracking resolution is not worse than 0.25 mm, 0.2/spl deg/ rms at a 200-mm height above the transmitting array's center. This resolution corresponds to an /spl sim/1-mm, 0.6/spl deg/ tracking accuracy. The novelty of the method consists as well in optimizing the transmitting coils' geometry to substantially (down to 0.5 mm) reduce the systematic error caused by the inaccuracy of the dipole field approximation.
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paper_title: Development of a small wireless position sensor for medical capsule devices

paper_content:

Medical capsule devices such as video capsule endoscopes are finding increasing use in clinical applications. At present, technologies capable of measuring capsule position in the digestive tract have not yet been established. The present study aims to develop a small wireless position sensor capable of measuring capsule position based on the phenomenon of mutual induction. Currents into primary coils are adjusted to maintain electromotive force induced in secondary coils at a constant level. Electromotive forces induced in the secondary coils are modulated to FM signals using an astable multivibrator, and the signals are passed directly through living tissue at low current and then demodulated by detectors on the surface of the body. A prototype wireless sensor was developed and evaluated in vitro. The sensor was capable of accurately measuring capsule position up to 500 (mm) from the primary coils with an accuracy of 5 (mm). Miniaturization of the sensor is necessary for commercialization.
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paper_title: Capsule Endoscopy: From Current Achievements to Open Challenges

paper_content:

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.
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paper_title: A Real-Time Tracking System for an Endoscopic Capsule using Multiple Magnetic Sensors

paper_content:

A tracking system for visualizing the location of a magnetically marked diagnostic capsule in real time is proposed. The intended application is the gas- trointestinal (GI) tract which is regarded by gastroenterologists as a black box. An endoscopic capsule capable of releasing diagnostic biomarker probes to areas of the gastrointestinal tract that are inaccessible via conventional means will enable gas- troenterologists to accurately determine the changes in functionality of the GI tract due to diseases. This requires a tracking system that can show the location of the capsule in real-time as it travels down the digestive tract. This paper presents the de- sign and implementation of such a tracking system using multiple magnetic sensors. It is free from the disadvantages most radio-frequency tracking systems suffer from. We report on the developments of the magnetic sensing hardware, tracking algo- rithm based on empirically developed models and experimental results. The results reveal the suitability of the proposed system for in vivo applications.
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paper_title: Wearable magnetic locating and tracking system for MEMS medical capsule

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Abstract This work focuses on a wearable magnetic tracking technology for the MEMS medical capsule. As a booming non-invasive medical diagnostic technology, the MEMS medical capsule provides effective solutions in deep intestines as wireless endoscopes, wireless parameter detectors or drug deliverers. To provide a precise, easy-to-operate and low-cost tracking solution for the capsule, we develop a wearable magnetic tracking system based on Hall-Effect and magnetic dipole model. The system basically consists of the wearable tracking vest and operating software. To accomplish the real-time data collection and prevent the interference from the earth magnetic field, some effective multi-channel data collecting and processing solutions are implemented. Several trial tests have been performed with relatively accurate expectation to justify the precision of the system. The volunteer experiments showed that the system can be adjusted for suitable wearing. The effective reduction of the interference from the earth magnetic filed allows the volunteer make basic movement during wearing the system. Moreover, the results compared with the X-ray image of the small intestine demonstrate that this system can successfully trace the motion of the capsule inside the twisted intestine.
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paper_title: Position and Orientation Accuracy Analysis for Wireless Endoscope Magnetic Field Based Localization System Design

paper_content:

This paper focuses on wireless capsule endoscope magnetic field based localization by using a linear algorithm, an unconstrained optimization method and a constrained optimization method. Eight sensor populations are employed for performance evaluation. For each of five sensor populations, four different sensor configurations are investigated, which represent potential sensor placements in practice. Accuracy is evaluated over a range of noise standard deviations and the position area is set on a solid cylinder which well represents the realistic scenario of the human body. It is observed that the optimization method greatly outperforms the linear algorithm that should not be used alone in general. The constrained optimization approach outperforms the unconstrained optimization method in presence of large noise. Simulation results show that best position accuracy is achieved when the sensors are uniformly deployed on a 2D plane with some sensors on the boundary of the position area. For the sensor populations considered, when increasing sensor population by one, the accuracy improves by about 0.45 divided by the sensor population. The results provide useful information for the design of wireless endoscope localization systems.
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paper_title: An improved magnetic localization and orientation algorithm for wireless capsule endoscope

paper_content:

In this paper, we propose a novel localization algorithm for tracking a magnet inside the capsule endoscope by 3-axis magnetic sensors array. In the algorithm, we first use an improved linear algorithm to obtain the localization parameters by finding the eigenvector corresponding to the minimum eigenvalue of the objective matrix. These parameters are used as the initial guess of the localization parameters in the nonlinear localization algorithm, and the nonlinear algorithm searches for more appropriate parameters that can minimize the objective error function. As the results, we obtain more robust and accurate localization results than those by using linear algorithm only. Nevertheless, the time efficiency of the nonlinear algorithm is enhanced. The real experimental data show that the average localization accuracy is about 2mm and the average orientation accuracy is about 1.6° when the magnet moves within the sensing area of 240mm ×240mm square.
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paper_title: Improved Modeling of Electromagnetic Localization for Implantable Wireless Capsules

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Abstract An electromagnetic localization method for implantable wireless capsules has been developed that employs a three-axial magnetic sensor embedded in the capsules and three energized coils attached on the abdomen. In order to further improve the localization accuracy, a novel localization model has been derived based on the Biot-Savart Law. For simplicity of the calculation without increasing the position error, the method of truncated series expansion has been used in modeling. The experiment showed that the improved model had higher precision than the original dipole model. Using the improved model, the localization error can be greatly reduced. The improved model is an elementary math function and suitable for resolving some inverse magnetic problems in engineering.
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paper_title: A further step beyond wireless capsule endoscopy

paper_content:

Purpose – Aims to report on a new trend of research and development in the wireless capsule endoscope.Design/methodology/approach – Presents a conceptual design of a wireless capsule endoscope having new features like navigation control, self‐propulsion, higher rate image transmission, acquisition of samples, application of medications and so forth.Findings – The basic principle has been verified by experiments. Seems promising.Research limitations/implications – Yet to need a lot of effort for commercialization.Practical implications – If successful, it will provide another way of least invasive medical treatment that must reduce pain of patients drastically.Originality/value – Taking advantage of the state‐of‐the‐art micro‐technology it suggests a further step beyond the current wireless capsule endoscope.
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paper_title: A New Calibration Procedure for Magnetic Tracking Systems

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In this study, we suggest a new approach for the calibration of magnetic tracking systems that allows us to calibrate the entire system in a single setting. The suggested approach is based on solving a system of equations involving all the system parameters. These parameters include: 1) the magnetic positions of the transmitting coils; 2) their magnetic moments; 3) the magnetic position of the sensor; 4) its sensitivity; and 5) the gain of the sensor output amplifier. We choose a set of parameters that define the origin, orientation, and scale of the reference coordinate system and consider them as constants in the above system of equations. Another set of constants is the sensor output measured at a number of arbitrary positions. The unknowns in the above equations are all the other system parameters. To define the origin and orientation of the reference coordinate system, we first relate it to a physical object, e.g., to the transmitter housing. We then use special supports to align the sensor with the edges of the transmitter housing and measure the sensor output at a number of aligned positions. To define the scale of the reference coordinate system, we measure the distance between two arbitrary sensor locations with a precise instrument (a caliper). This is the only parameter that should be calibrated with the help of an external measurement tool. To illustrate the efficiency of the new approach, we applied the calibration procedure to a magnetic tracking system employing 64 transmitting coils. We have measured the systematic tracking errors before and after applying the calibration. The systematic tracking errors were reduced by an order of magnitude due to applying the new calibration procedure.
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paper_title: Estimating Body Segment Orientation by Applying Inertial and Magnetic Sensing Near Ferromagnetic Materials

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Inertial and magnetic sensors are very suitable for ambulatory monitoring of human posture and movements. However, ferromagnetic materials near the sensor disturb the local magnetic field and, therefore, the orientation estimation. A Kalman-based fusion algorithm was used to obtain dynamic orientations and to minimize the effect of magnetic disturbances. This paper compares the orientation output of the sensor fusion using three-dimensional inertial and magnetic sensors against a laboratory bound opto-kinetic system (Vicon) in a simulated work environment. With the tested methods, the difference between the optical reference system and the output of the algorithm was 2.6 degrees root mean square (rms) when no metal was near the sensor module. Near a large metal object instant errors up to 50 degrees were measured when no compensation was applied. Using a magnetic disturbance model, the error reduced significantly to 3.6 degrees rms.
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paper_title: A Cubic 3-Axis Magnetic Sensor Array for Wirelessly Tracking Magnet Position and Orientation

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In medical diagnoses and treatments, e.g., endoscopy, dosage transition monitoring, it is often desirable to wirelessly track an object that moves through the human GI tract. In this paper, we propose a magnetic localization and orientation system for such applications. This system uses a small magnet enclosed in the object to serve as excitation source, so it does not require the connection wire and power supply for the excitation signal. When the magnet moves, it establishes a static magnetic field around, whose intensity is related to the magnet's position and orientation. With the magnetic sensors, the magnetic intensities in some predetermined spatial positions can be detected, and the magnet's position and orientation parameters can be computed based on an appropriate algorithm. Here, we propose a real-time tracking system developed by a cubic magnetic sensor array made of Honeywell 3-axis magnetic sensors, HMC1043. Using some efficient software modules and calibration methods, the system can achieve satisfactory tracking accuracy if the cubic sensor array has enough number of 3-axis magnetic sensors. The experimental results show that the average localization error is 1.8 mm.
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paper_title: Perspective of active capsule endoscope: actuation and localisation

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The self-contained wireless capsule endoscope provides non-invasive, painless and effective diagnosis of the diseases in the small intestine. One anticipation is to embed the capsule with therapeutic tools and enable not only diagnosis but also treatment of the GI diseases. Prior to the accomplishment of this objective, controlled movement of the capsule should be achieved first. In this paper, we focused on the actuation and localisation issues of the active capsule endoscope. After a survey on the related work, the challenges were presented and the possible solutions were discussed.
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paper_title: Numerical Study on the Improvement of Detection Accuracy for a Wireless Motion Capture System

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A detection technique having an accuracy of better than 1 mm is required for body motion analysis in the field of medical treatment. A wireless magnetic motion capture system is one such effective detection technique. We propose a candidate system using an LC resonant magnetic marker (LC marker). Previous studies have showed that the system is capable of repeatable position detection accuracy of better than 1 mm if the system has an adequate signal-to-noise (S/N ratio). However, there are some cases in which the detection results include unignorable errors because some approximations, e.g. a magnetic dipole assumption of the LC marker, are applied to solve the inverse problem to determine the position and orientation of the LC marker. Therefore, a numerical analysis is employed to realize a motion capture system having a high detection accuracy. To elucidate the problem of detection error, the influence of variations in the sizes of the LC marker and the pick-up coil are considered in the numerical simulation. After studying the analysis, the main cause of detection error is determined to be the size of the pick-up coil rather than the size of the LC marker. It was also is found that a pick-up coil measuring 10 mm in diameter with a wound coil width of 1 mm achieves a detection accuracy of better than 0.1 mm.
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paper_title: Robotic magnetic steering and locomotion of capsule endoscope for diagnostic and surgical endoluminal procedures

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This paper describes a novel approach to capsular endoscopy that takes advantage of active magnetic locomotion in the gastrointestinal tract guided by an anthropomorphic robotic arm. Simulations were performed to select the design parameters allowing an effective and reliable magnetic link between the robot end-effector (endowed with a permanent magnet) and the capsular device (endowed with small permanent magnets). In order to actively monitor the robotic endoluminal system and to efficiently perform diagnostic and surgical medical procedures, a feedback control based on inertial sensing was also implemented. The proposed platform demonstrated to be a reliable solution to move and steer a capsular device in a slightly insufflated gastrointestinal lumen.
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paper_title: Wireless Magnetic Position-Sensing System Using Optimized Pickup Coils for Higher Accuracy

paper_content:

With the aim of improving the detection accuracy of a wireless magnetic position-sensing system using an LC resonant magnetic marker, a pickup coil with an optimal size (10 mm in diameter × mm thick), as calculated by a previous simulation study, was used and tested in this paper. Our study confirmed that positional errors were reduced to a submillimeter order in the area within y=120 mm from the pickup coil array. On the contrary, in the area outside y=130 mm from the pickup coil array, the errors increased by about 0.5-2 mm compared to the results for the previous pickup coil size (25 mm in diameter × 2 mm thick). Regardless of the size of the pickup coil, however, compensation can be made for these positional deviations, including the influence of the mutual inductance between the LC marker and the exciting coil. After application of the compensation process, the detection results were corrected approximately to the actual positions of the LC marker.
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paper_title: Position and orientation detection of capsule endoscopes in spiral motion

paper_content:

In this paper, a position and orientation detection method for the capsule endoscopes devised to move through the human digestive organs in spiral motion, is introduced. The capsule is equipped with internal magnets and flexible threads on their outer shell. It is forced to rotate by an external rotating magnetic field that produces a spiral motion. As the external magnetic field is generated by rotating a permanent magnet, the 3-axes Cartesian coordinate position and 3-axes orientation of the capsule endoscopes can be measured by using only 3 hall-effect sensors orthogonally installed inside the capsule. However, in this study, an additional hall-effect sensor is employed along the rotating axis at a symmetrical position inside the capsule body to enhance measurement accuracy. In this way, the largest position detection error appearing along the rotating axis of the permanent magnet could be reduced to less than 15mm, when the relative position of the capsule endoscope to the permanent magnet is changed from 0mm to 50mm in the X-direction, from −50mm to +50mm in the Y-direction and from 200mm to 300mm in the Z-direction. The maximum error of the orientation detection appearing in the pitching direction ranged between −4° and +15°.
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paper_title: Swallowable medical devices for diagnosis and surgery: The state of the art

paper_content:

Abstract The first wireless camera pills created a revolutionary new perspective for engineers and physicians, demonstrating for the first time the feasibility of achieving medical objectives deep within the human body from a swallowable, wireless platform. The approximately 10 years since the first camera pill has been a period of great innovation in swallowable medical devices. Many modules and integrated systems have been devised to enable and enhance the diagnostic and even robotic capabilities of capsules working within the gastrointestinal (GI) tract. This article begins by reviewing the motivation and challenges of creating devices to work in the narrow, winding, and often inhospitable GI environment. Then the basic modules of modern swallowable wireless capsular devices are described, and the state of the art in each is discussed. This article is concluded with a perspective on the future potential of swallowable medical devices to enable advanced diagnostics beyond the capability of human visual perception, and even to directly deliver surgical tools and therapy non-invasively to interventional sites deep within the GI tract.
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paper_title: Adaptive Linearized Methods for Tracking a Moving Telemetry Capsule

paper_content:

In this paper, we discuss system and method of determining the real-time location of an omni-directional diagnostic radio frequency (RF) system while the object (transmitter) is moving freely inside an inaccessible organ. A specific application to the human gastrointestinal (GI) organ is presented, showing the importance of the method in accessing a specific site for drug administration or for extracting fluid or tissue samples for biopsy and similar medical investigations. For practical purposes, omnidirectional antenna on the transmitter at 433 MHz, normalized transmitter power 1 W was modeled for simplicity, and Es/No = 20 dB (corresponding to the linear region of the target transceiver). A brief discussion of how the original analogue signals, after conversion to voltage, was adapted for position tracking. In the tracking algorithm, we employed a path loss scenario based on the popular log-normal model to simulate the effects of organs on signal quality between transmitter and receiver at various distances.
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paper_title: A Review and Adaptation of Methods of Object Tracking to Telemetry Capsules

paper_content:

Abstract This review considers techniques employing radio frequency (RF) as well as ultrasound signals for tracking. Medical capsules have been employed since the SOs to measure various physiological parameters in the human body. Examples are temperature, pH, or pressure inside the gastrointestinal (GI) tract. The development and subsequent incorporation of new technology into reasonably priced, commercially available devices have made ultrasound and RF devices readily accessible for medical diagnosis. Some applications for telemetry capsules are drug delivery, and collection of tissue/fluid samples. Samples are taken from the GI to understand or treat diseases where diagnosis can only be made by taking a biopsy from the intestinal walls. Such biopsies have traditionally been performed using customized endoscopes. In order for a telemetry capsule to be effective in the above named tasks, accurate knowledge of the location of the capsule within the body during tests is necessary. As such, methods for calcu...
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paper_title: Ground-Based Wireless Positioning

paper_content:

Ground Based Wireless Positioning provides an in-depth treatment of non-GPS based wireless positioning techniques, with a balance between theory and engineering practice. The book presents the architecture, design and testing of a variety of wireless positioning systems based on the time-of-arrival, signal strength, and angle-of-arrival measurements. These techniques are essential for developing accurate wireless positioning systems which can operate reliably in both indoor and outdoor environments where the Global Positioning System (GPS) proves to be inadequate. The book covers a wide range of issues including radio propagation, parameter identification, statistical signal processing, optimization, and localization in large and multi-hop networks. A comprehensive study on the state-of-the-art techniques and methodologies in wireless positioning and tracking is provided, including anchor-based and anchor-free localisation in wireless sensor networks (WSN). The authors address real world issues such as multipath, non-line-of-sight (NLOS) propagation, accuracy limitations and measurement errors. Presenting the latest advances in the field, Ground Based Wireless Positioning is one of the first books to cover non-GPS based technologies for wireless positioning. It serves as an indispensable reference for researchers and engineers specialising in the fields of localization and tracking, and wireless sensor networks. Provides a comprehensive treatment of methodologies and algorithms for positioning and tracking Includes practical issues and case studies in designing real wireless positioning systems Explains non-line-of-sight (NLOS) radio propagation and NLOS mitigation techniques Balances solid theory with engineering practice of non-GPS wireless systems
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paper_title: Position and Orientation Accuracy Analysis for Wireless Endoscope Magnetic Field Based Localization System Design

paper_content:

This paper focuses on wireless capsule endoscope magnetic field based localization by using a linear algorithm, an unconstrained optimization method and a constrained optimization method. Eight sensor populations are employed for performance evaluation. For each of five sensor populations, four different sensor configurations are investigated, which represent potential sensor placements in practice. Accuracy is evaluated over a range of noise standard deviations and the position area is set on a solid cylinder which well represents the realistic scenario of the human body. It is observed that the optimization method greatly outperforms the linear algorithm that should not be used alone in general. The constrained optimization approach outperforms the unconstrained optimization method in presence of large noise. Simulation results show that best position accuracy is achieved when the sensors are uniformly deployed on a 2D plane with some sensors on the boundary of the position area. For the sensor populations considered, when increasing sensor population by one, the accuracy improves by about 0.45 divided by the sensor population. The results provide useful information for the design of wireless endoscope localization systems.
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paper_title: A novel RF-based propagation model with tissue absorption for location of the GI tract

paper_content:

In order to accurately estimate (build) the radio signal propagation attenuation model, especially inside the gastro-intestine (GI) tract of the human body, the Radio Frequency (RF) absorption characterization in human body is investigated. This characterization provides a criterion to design the Received Signal Strength (RSS) based localization system for the objective inside the human body. In this paper, the Specific Absorption Rate (SAR), E-field, H-field of the near and far field are investigated at frequencies of 434MHz, 868MHz, 1.2GHz and 2.4GHz respectively. Then, the numerical electromagnetic analysis with the finite-differencetime-domain (FDTD) is applied to model the in vivo radio propagation channels by using a dipole antenna. Finally, simulation experiments are carried out in homogenous and heterogeneous mediums. The results show that the electromagnetic (EM) propagation is not only distance and orientation dependent, but also tissue absorption dependent in human body. The proposed model is in agreement with measurements in the simulation experiments.
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paper_title: Performance bounds for RF positioning of endoscopy camera capsules

paper_content:

In this paper, we evaluate the factors affecting the accuracy achievable in localization of an endoscopic wireless capsule as it passes through the digestive system of the human body. Using a three-dimension full electromagnetic wave simulation model, we obtain bounds on the capsule-location estimation errors when the capsule is in each of three individual organs: stomach, small intestine and large intestine. The simulations assume two different external sensor arrays topologies. We compare these performance bounds and draw the conclusion that location-estimation errors are different for different organs and for various topologies of the external sensor arrays.
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paper_title: Adaptive Linearized Methods for Tracking a Moving Telemetry Capsule

paper_content:

In this paper, we discuss system and method of determining the real-time location of an omni-directional diagnostic radio frequency (RF) system while the object (transmitter) is moving freely inside an inaccessible organ. A specific application to the human gastrointestinal (GI) organ is presented, showing the importance of the method in accessing a specific site for drug administration or for extracting fluid or tissue samples for biopsy and similar medical investigations. For practical purposes, omnidirectional antenna on the transmitter at 433 MHz, normalized transmitter power 1 W was modeled for simplicity, and Es/No = 20 dB (corresponding to the linear region of the target transceiver). A brief discussion of how the original analogue signals, after conversion to voltage, was adapted for position tracking. In the tracking algorithm, we employed a path loss scenario based on the popular log-normal model to simulate the effects of organs on signal quality between transmitter and receiver at various distances.
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paper_title: Capsule endoscopy: the localization system

paper_content:

Capsule endoscopy (CE) has become a valuable tool in the armamentarium used to investigate the small bowel. It has been shown to be superior to pushenteroscopy in patients with occult gastrointestinal bleeding for the detection of distal lesions, and to barium follow through in patients with suspected small bowel pathology or Crohn’s disease [1–3]. One of the obstacles with CE was its inability to precisely determine the location of the pathologies found. The Localization Module is an additional feature incorporated into the RAPID Workstation Software of the Given Imaging system (Yoqneam, Israel) to assist the physician in determining the relative location of pathologies found by the M2A capsule. The localization is based on the strength of capsule emitted signal received by the eight sensors (antennas) on the exterior of the abdomen. The output of the localization module is a graphic trajectory of the capsule as it is transported through the GI tract. In addition, the module calculates and presents GI transit times based on the identified and labeled images of the entrance to the stomach, the passage in the pylorus, and the passage through the ileocecal valve. The localization capability of the system is based on the off-line processing of the level of the radio frequency (RF) signals from the sensor array and as such, does not require any additional signals or equipment.
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paper_title: Design and Implementation of 3D Positioning Algorithms Based on RF Signal Radiation Patterns for In Vivo Micro-robot

paper_content:

Recent popularity of capsule endoscopes as a medical means to investigate lesions along digestive tract has prompted complaints by doctors about the in sufficient positioning system for the capsules. The possible major reason would be that current positioning system is based on time difference of arrival whose precision is hard to improve for short flight distances. To enable better control of active capsules, we propose to exploit the radiation patterns of radio frequency (RF) signals from the capsules. The symmetric RF signals can be sensed by receivers in similar areas of external receiver arrays. The similarity, position, shape and size of those areas are considered to make back projection calculation and identify accurate 3D positions of the signal source. Our positioning algorithms are scalable to achieve better precision than the density of receivers.
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paper_title: Phase difference based RFID navigation for medical applications

paper_content:

RFID localization is a promising new field of work that is eagerly awaited for many different types of applications. For use in a medical context, special requirements and limitations must be taken into account, especially regarding accuracy, reliability and operating range. In this paper we present an experimental setup for a medical navigation system based on RFID. For this we applied a machine learning algorithm, namely support vector regression, to phase difference data gathered from multiple RFID receivers. The performance was tested on six datasets of different shape and placement within the volume spanned by the receivers. In addition, two grid based training sets of different size were considered for the regression. Our results show that it is possible to reach an accuracy of tag localization that is sufficient for some medical applications. Although we could not reach an overall accuracy of less than one millimeter in our experiments so far, the deviation was limited to two millimeters in most cases and the general results indicate that application of RFID localization even to highly critical applications, e. g., for brain surgery, will be possible soon.
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paper_title: A novel radio propagation radiation model for location of the capsule in GI tract

paper_content:

In this paper, we discuss the influence of the antenna orientation radiation pattern in localization algorithm based on Received Signal Strength Indicator (RSSI). We also improve the empirical model of signal propagation by building the path loss function of the human gastro-intestine (GI) tract. The novel model includes information of both the distance and azimuth angle variables. The numerical electromagnetic analysis with the finite-difference time-domain (FDTD) is applied to model the vivo radio propagation channels by using a dipole antenna suitable for the model related to the human body. The proposed propagation model is compared with empirical model, and the simulation results show that the compensated model is more accurate by calculating the azimuth radiation attenuation. It demonstrates that the often overlooked antenna orientation has the dominant effect on the signal strength sensitivity.
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paper_title: An empirically-based path loss model for wireless channels in suburban environments

paper_content:

We present a statistical path loss model derived from 1.9 GHz experimental data collected across the United States in 95 existing macrocells. The model is for suburban areas, and it distinguishes between different terrain categories. Moreover, it applies to distances and base antenna heights not well-covered by existing models. The characterization used is a linear curve fitting the dB path loss to the dB-distance, with a Gaussian random variation about that curve due to shadow fading. The slope of the linear curve (corresponding to the path loss exponent, /spl gamma/) is shown to be a random variate from one macrocell to another, as is the standard deviation, /spl sigma/ of the shadow fading. These two parameters are statistically modeled, with the dependencies on base antenna height and terrain category made explicit. The resulting path loss model applies to base antenna heights from 10 to 80 meters; base-to-terminal distances from 0.1 to 8 km; and three distinct terrain categories.
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paper_title: Accurate localization of RFID tags using phase difference

paper_content:

Due to their light weight, low power, and practically unlimited identification capacity, radio frequency identification (RFID) tags and associated devices offer distinctive advantages and are widely recognized for their promising potential in context-aware computing; by tagging objects with RFID tags, the environment can be sensed in a cost- and energy-efficient means. However, a prerequisite to fully realizing the potential is accurate localization of RFID tags, which will enable and enhance a wide range of applications. In this paper we show how to exploit the phase difference between two or more receiving antennas to compute accurate localization. Phase difference based localization has better accuracy, robustness and sensitivity when integrated with other measurements compared to the currently popular technique of localization using received signal strength. Using a software-defined radio setup, we show experimental results that support accurate localization of RFID tags and activity recognition based on phase difference.
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paper_title: Development of a Tracking Algorithm for an In-Vivo RF Capsule Prototype

paper_content:

This paper presents the design of a tracking algorithm for an in-vivo capsule swallowed by patients. Such devices play a very important role in the diagnosis and treatment of internal disorders, for example, in the digestive tract. Tracking the location of the capsule as it travels down the digestive tract is critical to ensure its position near the affected area. Various sensing mechanisms that can be applied for tracking the capsule include the use of radio frequency and magnetic signals. The work reported in this paper mainly focuses on the development of an intelligent tracking algorithm that could potentially be coupled with a variety of sensing technologies. In this paper we use RF-based capsule and sensor prototypes for developing and testing the tracking algorithm. Encouraging practical results have been obtained which demonstrate the validity of the tracking algorithm and the underlying look-up table based methodology.
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paper_title: Design of 3D Positioning Algorithm Based on RFID Receiver Array for In Vivo Micro-Robot

paper_content:

The clinical applications of capsule endoscopes have been increasing consistently since the invention of a passive capsule endoscope was made [1]. Though the capsule endoscopes are effective in detecting large lesions along human digestive tract, they cannot meet doctors’ requirements of active control of the capsules to carefully examine small lesions. The poor precision of positioning system is one of the major hurdles blocking robots from approaching the accurate position of suspected areas. In this paper, we propose a novel algorithm to exploit the radiation pattern of a radio frequency (RF) tag inside the capsule, which forms shadows or traces on a set of receiver arrays. According to the shape of the traces and the radiation pattern, the position of the radiation source, i.e. the tag inside the capsule can be calculated with our algorithm. The details of our algorithm are presented with the simulation results in the paper. With the settings under medical constraints, the degree of positioning precision in simulation is improved to less than 1cm horizontally and 2cm vertically.
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paper_title: Data Processing Tasks in Wireless GI Endoscopy: Image-Based Capsule Localization & Navigation and Video Compression

paper_content:

The paper addresses data processing support that is required in capsule gastrointestinal endoscopy. First, capsule position estimation method using standard MPEG-7 image features (descriptors) is discussed. The proposed approach makes use of vector quantization, principal component analysis and neural networks. Next, new algorithms dedicated for virtual colonoscopy (VC) human body inspection are described. The VC images can be registered with endoscopic ones and help in capsule localization and navigation. Finally, an original, low- complexity, efficient image compression method, based on integer-to-integer 4x4 DCT transform, is presented and experimentally verified.
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paper_title: Localization of Endoscopic Capsule in the GI Tract Based on MPEG-7 Visual Descriptors

paper_content:

The paper addresses the problem of localization of video endoscopic capsule in the gastrointestinal (GI) tract on the base of appropriate classification of images received from it. In this context usefulness of MPEG-7 image descriptors as classification features has been verified. For classification purpose various state of the art tools were used including Neural Networks and Vector Quantization. The dimension of the problem was also reduced by the Principal Component Analysis. Novelty of the presented approach consists in joint application of mentioned above techniques for recognition of the GI region inspected by the capsule by means of classification of MPEG-7 features to different parts of GI tract. In this research recognition of the upper part organs of the GI tract has been performed.
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paper_title: Capsule endoscope localization based on computer vision technique

paper_content:

To build a new type of wireless capsule endoscope with interactive gastrointestinal tract examination, a localization and orientation system is needed for tracking 3D location and 3D orientation of the capsule movement. The magnetic localization and orientation method produces only 5 DOF, but misses the information of rotation angle along capsule’s main axis. In this paper, we presented a complementary orientation approach for the capsule endoscope, and the 3D rotation can be determined by applying computer vision technique on the captured endoscopic images. The experimental results show that the complementary orientation method has good accuracy and high feasibility.
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paper_title: Magnetically Controllable Gastrointestinal Steering of Video Capsules

paper_content:

Wireless capsule endoscopy (WCE) allows for comfortable video explorations of the gastrointestinal (GI) tract, with special indication for the small bowel. In the other segments of the GI tract also accessible to probe gastroscopy and colonscopy, WCE still exhibits poorer diagnostic efficacy. Its main drawback is the impossibility of controlling the capsule movement, which is randomly driven by peristalsis and gravity. To solve this problem, magnetic maneuvering has recently become a thrust research area. Here, we report the first demonstration of accurate robotic steering and noninvasive 3-D localization of a magnetically enabled sample of the most common video capsule (PillCam, Given Imaging Ltd, Israel) within each of the main regions of the GI tract (esophagus, stomach, small bowel, and colon) in vivo, in a domestic pig model. Moreover, we demonstrate how this is readily achievable with a robotic magnetic navigation system (Niobe, Stereotaxis, Inc, USA) already used for cardiovascular clinical procedures. The capsule was freely and safely moved with omnidirectional steering accuracy of 1°, and was tracked in real time through fluoroscopic imaging, which also allowed for 3-D localization with an error of 1 mm. The accuracy of steering and localization enabled by the Stereotaxis system and its clinical accessibility world wide may allow for immediate and broad usage in this new application. This anticipates magnetically steerable WCE as a near-term reality. The instrumentation should be used with the next generations of video capsules, intrinsically magnetic and capable of real-time optical-image visualization, which are expected to reach the market soon.
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paper_title: The role of gamma-scintigraphy in oral drug delivery.

paper_content:

The gastrointestinal tract is usually the preferred site of absorption for most therapeutic agents, as seen from the standpoints of convenience of administration, patient compliance and cost. In recent years there has been a tendency to employ sophisticated systems that enable controlled or timed release of a drug, thereby providing a better dosing pattern and greater convenience to the patient. Although much about the performance of a system can be learned from in vitro release studies using conventional and modified dissolution methods, evaluation in vivo is essential in product development. The non-invasive technique of gamma-scintigraphy has been used to follow the gastrointestinal transit and release characteristics of a variety of pharmaceutical dosage forms. Such studies provide an insight into the fate of the delivery system and its integrity and enable the relationship between in vivo performance and resultant pharmacokinetics to be examined (pharmacoscintigraphy).
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paper_title: Development of a new engineering-based capsule for human drug absorption studies.

paper_content:

Over recent years, there has been a significant growth in the number of new drugs entering development with challenging pharmaceutical (e.g. solubility) and biopharmaceutical (e.g. permeability) properties. As a consequence, there is an increasing number of pharmaceutical companies using human absorption studies to provide a 'route map' for development. These projects are typically undertaken early in clinical development and utilize engineering-based capsules to provide non-invasive drug delivery to the selected sites of the human gut. The Enterion capsule has recently been developed to provide for the delivery of a wide range of different drug formulations, for example, solution, powder and granulate, into any region of the gut, both easily and efficiently.
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paper_title: Ultrasound Emitter Localization in Heterogeneous Media

paper_content:

A novel algorithm to accurately determine the location of an ultrasound source within heterogeneous media is presented. The method obtains a small spacial error of 748 microm+/-310 microm for 100 different measurements inside a circular area with 140 mm diameter. The new algorithm can be used in targeted drug delivery for cancer therapies as well as to accurately locate any kind of ultrasound sources in heterogeneous media, such as ultrasonically marked medical devices or tumors.
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paper_title: A wireless acoustic emitter for passive localization in liquids

paper_content:

For the localization of minimally invasive medical devices, such as capsule endoscopes in the human body, ultrasound combines good resolution, minimal adverse health effects, high speed, adequate frame rates, and low cost. In the case of capsule endoscopes, small onboard ultrasonic emitters with minimal power requirements have the potential to provide significantly enhanced localization. We demonstrate for the first time acoustic emission in the kHz range using a wireless emitter based on the actuation principle of the wireless resonant magnetic microactuator developed recently in our institute. Our experiments show good agreement with the theoretical model, and simulations show the potential for high resolution localization.
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paper_title: An MRI-Compatible Robotic System With Hybrid Tracking for MRI-Guided Prostate Intervention

paper_content:

This paper reports the development, evaluation, and first clinical trials of the access to the prostate tissue (APT) II system-a scanner independent system for magnetic resonance imaging (MRI)-guided transrectal prostate interventions. The system utilizes novel manipulator mechanics employing a steerable needle channel and a novel six degree-of-freedom hybrid tracking method, comprising passive fiducial tracking for initial registration and subsequent incremental motion measurements. Targeting accuracy of the system in prostate phantom experiments and two clinical human-subject procedures is shown to compare favorably with existing systems using passive and active tracking methods. The portable design of the APT II system, using only standard MRI image sequences and minimal custom scanner interfacing, allows the system to be easily used on different MRI scanners.
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paper_title: Real-time position monitoring of invasive devices using magnetic resonance.

paper_content:

Techniques which can be used to follow the position of invasive devices in real-time using magnetic resonance (MR) are described. Tracking of an invasive device is made possible by incorporating one or more small RF coils into the device. These coils detect MR signals from only those spins near the coil. Pulse sequences which employ nonselective RF pulses to excite all nuclear spins within the field-of-view are used. Readout magnetic field gradient pulses, typically applied along one of the primary axes of the imaging system, are then used to frequency encode the position of the receive coil(s). Data are Fourier transformed and one or more peaks located to determine the position of each receiver coil in the direction of the applied field gradient. Subsequent data collected on orthogonal axes permits the localization of the receiver coil in three dimensions. The process can be repeated rapidly and the position of each coil can be displayed in real-time.
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paper_title: Capsule tracking in the GI tract: a novel microcontroller based solution

paper_content:

Telemetry capsules that will provide facilities for on-site drug delivery and those that are capable of taking tissue/fluid samples within the human gastro-intestinal (GI) are quite invaluable for diagnosing GI related diseases where diagnosis can only be made by taking a biopsy from the intestinal walls. Such biopsies have traditionally been preformed using custom endoscopes. To be effective in the above named tasks, accurate knowledge of the location of telemetry capsules within the GI tract is a necessity. This paper presents a method of tracking a capsule inside the human GI tract based on the application of a microcontroller to control the generation and transmission of ultrasonic pulses. The capsule, i.e. object, and the central receiver are capable of transmit and receive functions, others are receive-only stations. This ensures the collection of a reliable round-trip time of flight (TOF) data. Application of triangulation to the TOF data facilitates the determination of the real-time positions of the object with less than 10% aggregate measurement error
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paper_title: A hybrid method for 6-DOF tracking of MRI-compatible robotic interventional devices

paper_content:

This paper reports a novel hybrid method of tracking the position and orientation of robotic medical instruments within the imaging volume of a magnetic resonance imaging (MRI) system. The method utilizes two complementary measurement techniques: passive MRI fiducial markers and MRI compatible joint encoding. This paper reports an experimental evaluation of the tracking accuracy of this system. The accuracy of this system compares favorably to that of a previously reported active tracking system. Moreover, the hybrid system is quickly and easily deployed on different MRI scanner systems
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paper_title: Microrobots for Minimally Invasive Medicine

paper_content:

Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical microrobots; second, to explore the potential impact of medical microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical microrobots.
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paper_title: Design of a novel MRI compatible manipulator for image guided prostate interventions

paper_content:

This paper reports a novel remotely actuated manipulator for access to prostate tissue under magnetic resonance imaging guidance (APT-MRI) device, designed for use in a standard high-field MRI scanner. The device provides three-dimensional MRI guided needle placement with millimeter accuracy under physician control. Procedures enabled by this device include MRI guided needle biopsy, fiducial marker placements, and therapy delivery. Its compact size allows for use in both standard cylindrical and open configuration MRI scanners. Preliminary in vivo canine experiments and first clinical trials are reported.
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Title: A Review of Localization Systems for Robotic Endoscopic Capsules

Section 1: Introduction
Description 1: Overview of endoscopy, limitations of traditional methods, and introduction to wireless capsule endoscopy (WCE).

Section 2: Localization Methods Based on Magnetic Field Strength
Description 2: Discussion on tracking systems utilizing magnetic field strength, including magnetic localization for passive and active actuation systems.

Section 3: Localization Methods Based on Electromagnetic Waves
Description 3: Investigation of capsule tracking using different regions of the electromagnetic spectrum, focusing on radio, visible, X-ray, and gamma rays.

Section 4: Other Localization Methods
Description 4: Additional techniques for localization, including MRI and ultrasound-based methods.

Section 5: Conclusion
Description 5: Summary of the studied localization systems, their current limitations, and the future challenges for developing an effective capsule localization system.

Section 6: References
Description 6: Complete list of all the references cited in the paper.