Application of Wireless Power Transmission Systems in Wireless Capsule Endoscopy: An Overview
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paper_title: A wireless power transmission system for an active capsule endoscope for colon inspection

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Multipurpose active capsule endoscopes (ACE) have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. In order to deliver stable and sufficient energy safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a double-layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 500 mW usable power can be transmitted under the worst geometrical conditions and the safety restraints in a volume of Φ13 × 13 mm. The wireless power transmission system is integrated to an ACE and applied in animal experiments. The designed wireless power transmission is proved to be feasible and potentially safe in a future application.
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paper_title: 1 A Multi-Coil Inductive Powering System for an Endoscopic Capsule with Vibratory Actuation

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Abstract The transformation of endoscopic capsules from passive tools to robotic devices is increasingly attracting the interest of the research community. In the past few years, significant progress has been achieved in the areas of microelectronics and electromechanical systems. However, their use in commercial endoscopic capsules is hindered by their increased power demands, which, to present, cannot be adequately met by embedded power sources. A 3D inductive powering module, providing over 300 mW to the capsule, overcomes these limitations, thus enabling the integration of active locomotion systems, as well as advanced diagnostic and therapeutic features. This is demonstrated in the present study by a capsule prototype employing the wireless powering unit to drive an onboard vibratory motor for capsule propulsion. Simplified models are employed to illustrate the main principle of this vibratory locomotion scheme. Experimental results, involving movement of the prototype in various environments, confirm both the effectiveness of the wireless powering system, and the efficacy of the vibratory locomotion scheme.
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paper_title: Magnetic air capsule robotic system: proof of concept of a novel approach for painless colonoscopy

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Background ::: Despite being considered the most effective method for colorectal cancer diagnosis, colonoscopy take-up as a mass-screening procedure is limited mainly due to invasiveness, patient discomfort, fear of pain, and the need for sedation. In an effort to mitigate some of the disadvantages associated with colonoscopy, this work provides a preliminary assessment of a novel endoscopic device consisting in a softly tethered capsule for painless colonoscopy under robotic magnetic steering.
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paper_title: Silicon-Embedded Receiving Coil for High-Efficiency Wireless Power Transfer to Implantable Biomedical ICs

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In this letter, a silicon-embedded receiving coil is designed and fabricated for high-efficiency wireless power transfer to implantable biomedical ICs. The 4.5 mm × 4.5 mm embedded receiving coil achieved a large inductance of 4 μH and a high peak quality factor of 20 at 2.8 MHz. Measurement results of an inductive power link using the embedded receiving coil and a conventional printed-circuit-board transmitting coil (2 cm × 2 cm) demonstrated peak voltage gains of 0.84 and 0.24 and peak efficiency values of 30% and 4.3% for separation distances of 5 and 12 mm, respectively. This is the best reported wireless power transmission efficiency for separation distance similar to the implant chip size.
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paper_title: An endoscopic capsule robot: a meso-scale engineering case study

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A number of unique challenges arise in fabricating and assembling complex mechanisms at the meso-scale (hundreds of microns to centimetres). In general, for a complex multi-part mechanism at this length scale, no single machining technique can produce all the necessary parts—or often even a single individual part. Towards developing a comprehensive set of 'best practices' for combining multiple precision micromachining operations at the meso-scale, we present a case study on fabricating and assembling an endoscopic capsule robot. Existing passive imaging capsules have proven exceptionally useful in the diagnosis of the gastrointestinal tract, and robotic capsules promise to enhance their diagnostic capabilities and enable non-invasive treatment delivery. In this case study, we describe the fabrication of a robotic capsule (2.6 cm3 in volume) containing a complex mechanism consisting of 72 components, each of which requires a variety of meso- or even micro-scale features. We describe the manufacturing processes used to produce these components and features (combinations of high precision, multiply refixtured computer numerical control processes, sink and wire electro discharge machining, laser cutting, etc). These results contribute to the emerging framework of best practices in meso-scale design and manufacture, illustrating ways to effectively combine several processes to produce a complex meso-scale device.
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paper_title: Ingestible Wireless Capsule Technology: A Review of Development and Future Indication

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Ingestible wireless capsule endoscopy (WCE) is the one and only painless, effective, novel, diagnostic technology for inspecting the entire gastrointestinal (GI) tract for various diseases, such as obscure gastrointestinal bleeding (OGIB), tumors, cancer, Crohn’s disease, and celiac disease. Since the development of this technology, several companies have made remarkable improvements in their clinical products, but there are still some limitations that relate to the use of conventional wired endoscopy. Some of the major limitations that currently impede its wider application include its inability to repeat the view of critical areas, working time constraints, and poor image resolution. Many research groups currently are working on ways to solve these limitations. Presently, developing the ability to control the movement of the capsule, increasing its image transmission speed, and obtaining high-quality images are the main issues in the research area. A complex capsule with some therapeutic tools for the treatment of diseases of the GI tract also is at the beginning of development for the next generation of an active medical robot. In this paper, we report the status of several activities related to WCE, including improvement of capsule technology, research progress, technical challenges, and key indicators concerning the next-generation, active, medical robot.
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paper_title: Weekend Effect in Non-Variceal Upper Gastrointestinal Bleeding: Data From Nine Italian Gastrointestinal Units

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Weekend Effect in Non-Variceal Upper Gastrointestinal Bleeding: Data From Nine Italian Gastrointestinal Units
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paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

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Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
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paper_title: Personalizing therapies for gastric cancer: Molecular mechanisms and novel targeted therapies

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Globally, gastric cancer is the 4th most frequently diagnosed cancer and the 2nd leading cause of death from cancer, with an estimated 990000 new cases and 738000 deaths registered in 2008. In the advanced setting, standard chemotherapies protocols acquired an important role since last decades in prolong survival. Moreover, recent advances in molecular therapies provided a new interesting weapon to treat advanced gastric cancer through anti-human epidermal growth factor receptor 2 (HER2) therapies. Trastuzumab, an anti-HER2 monoclonal antibody, was the first target drug in the metastatic setting that showed benefit in overall survival when in association with platinum-5-fluorouracil based chemotherapy. Further, HER2 overexpression analysis acquired a main role in predict response for trastuzumab in this field. Thus, we conducted a review that will discuss the main points concerning trastuzumab and HER2 in gastric cancer, providing a comprehensive overview of molecular mechanisms and novel trials involved.
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paper_title: Wireless powering for a self-propelled and steerable endoscopic capsule for stomach inspection

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This paper describes the integration of an active locomotion module in a wirelessly powered endoscopic capsule. The device is a submersible capsule optimized to operate in a fluid environment in a liquid-distended stomach. A 3D inductive link is used to supply up to 400 mW to the embedded electronics and a set of 4 radio-controlled motor propellers. The design takes advantage of a ferrite-core in the receiving coil-set. This approach significantly improves the coupling with the external field source with respect to earlier work by the group. It doubles the power that can be received with a coreless coil-set under identical external conditions. The upper limit of the received power was achieved complying with the strict regulations for safe exposure of biological tissue to variable magnetic fields. The wireless transferred power was proven to be sufficient to achieve the speed of 7 cm/s in any directions. An optimized locomotion strategy was defined which limits the power consumption by running only 2 motors at a time. A user interface and a joystick controller allow to fully drive the capsule in an intuitive manner. The device functionalities were successfully tested in a dry and a wet environment in a laboratory set-up.
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paper_title: P-0126 Gastrointestinal Tumor Board: An Evolving Experience in Tehran Cancer Institute

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Gastrointestinal (GI) cancers are a significant source of morbidity and mortality in Iran, with stomach adenocarcinoma as the most common cancer in men and the second common cancer in women. Also, some parts of Northern Iran have one of the highest incidences of esophageal cancer in the world. Multi-disciplinary organ-based joint clinics and tumor boards are a well-recognized necessity for modern treatment of cancer and are routinely utilized in developed countries, especially in major academic centres. But this concept is relatively new in developing countries, where cancer treatment centres are burdened by huge loads of patients and have to cope with a suboptimum availability of resources and facilities. Cancer Institute of Tehran University of Medical Sciences is the oldest and the only comprehensive cancer treatment centre in Iran, with a long tradition of a general tumor board for all cancers. But with the requirements of modern oncology, there has been a very welcome attention to sub-specialized organ-based tumor boards and joint clinics here in the past few years. Considering this, we started a multi-disciplinary tumor board for GI cancers in our institute in early 2010 as the first such endeavor here. We hereby review this 2-year evolving experience. The process of establishment of a GI tumor board, participations from different oncology disciplines and related specialties, the cancers presented and discussed in the 2 years of this tumor board, the general intents of treatment for the decisions made and the development of interest in this tumor board among the Tehran oncology community will be reviewed. The GI tumor board of Tehran Cancer Institute started its work in January 2010, with routine weekly sessions. A core group of 2 physicians from each surgical, radiation and medical oncology departments plus one gastroenterologist, GI pathologist and radiologist was formed, but participation from all interested physicians was encouraged. An electronic database was kept from the beginning. The number of patients presented in the tumor board increased from 4 in January 2010 to 16 in December 2011. Most patients were presented by radiation oncology department (38%) and then surgical (36%) and medical oncology (20%) departments. Physicians' participation also grew from an average of 8 each session to 12 in the same months, with a number of cancer specialists taking part from other university hospitals in Tehran. A total number of 225 patients were presented with a treatment decision made in this 2-year period. The majority of cases were colorectal (32%), stomach (23%), and esophageal (17%) cancers. The number of pancreatic (7%) and hepatobiliary (6%) cancers were much smaller. Most decisions were for a primary treatment (surgery or radiochemotherapy) and then a neoadjuvant approach. Tehran Cancer Institute's GI tumor board is one of the first multi-disciplinary organ-based tumor boards in Iran, and as such has made a successful start, establishing itself as a recognized body for clinical decisions and consultations in GI oncology. This experience is growing and evolving, with newer presentation and discussion formats and adapted guidelines for treatment of GI cancers in Iran sought.
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paper_title: Clinical and Economic Burden of Emergency Department Visits Due to Gastrointestinal Diseases in the United States

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Clinical and Economic Burden of Emergency Department Visits Due to Gastrointestinal Diseases in the United States
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paper_title: PillCam small bowel capsule endoscopy gastric passage interval association with patient's complaints and pathological findings: a prospective study.

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BACKGROUND AND AIMS ::: Prolonged gastric transit interval of small bowel video capsule endoscopy (SBCE) can potentially indicate a motility disorder and disrupt whole small bowel visualization. The aim of this study was to prospectively examine the association of prolonged gastric passage interval with symptoms, anthropometric and laboratory factors, and factors related to the SBCE examination, such as indications and pathological findings. ::: ::: ::: MATERIALS AND METHODS ::: This was a prospective single-center study that included 100 patients who underwent SBCE for any indication. Before the examination, clinical, demographic, and anthropometric data were recorded. The patients filled the Gastroparesis Cardinal Symptoms Index (GCSI) questionnaire. We assessed the difference in the study parameters between the prolonged gastric transit (≥45 min) group and the group with a normal gastric transit. ::: ::: ::: RESULTS ::: Seventy-six patients had normal gastric passage interval and 24 patients had prolonged gastric passage interval. No significant differences were found between the groups in age, sex, prevalence of diabetes mellitus, use of antimotility drugs, indications for the exam and levels of hemoglobin, C-reactive protein, and albumin. Esophageal and small bowel transition intervals did not vary between both groups. The mean score for any GCSI item and the mean total GCSI score did not differ significantly between the normal and the prolonged gastric passage interval groups. There were no significant differences between the groups in pathological findings in the small bowel. ::: ::: ::: CONCLUSION ::: In the study population, prolonged SBCE gastric transit interval had no clinical significance, and therefore, probably does not mandate any further gastrointestinal evaluation.
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paper_title: An Inchworm-like Locomotion Mechanism Based on Magnetic Actuator for Active Capsule Endoscope

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Locomotion mechanism is a necessity for development of an active capsule endoscope. In this paper, we propose an inchworm-like locomotion mechanism, which is composed of a permanent magnet, a plunger, a solenoid and a cone-shaped polymer. When an alternating current is applied to the solenoid, the magnet will make a reciprocating movement under the electromagnetic force. With the friction difference produced by the polymer, the actuator could propel itself forward on a 2D surface. The working principle and kinetic model of the mechanism are analyzed. A prototype with a size of Phi12*37 mm were fabricated to study the feasibility of the mechanism. Experiments were carried out on the surfaces of various frictional coefficients. The results show that the actuator works more efficiently on the surface of the glass than on the paper, because the polymer has better clamping effect on the former. The velocity changes with the frequency and amplitude of the current. The mechanism consumes a low power and it can work under a relatively low voltage (less than 20 V). It has the potential for actuation of an active capsule endoscope
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paper_title: Wireless capsule endoscopy--a novel technique for visualising the gut.

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This review is presenting the "capsule endoscopy", a developing method for visualizing the gut and especially its "dark" areas, the small intestine. It is presented its description, and the evaluation of its present indications. The capsule endoscopy is good for identifying bleeding of unknown origin, tumors and inflammatory lesions of small bowel. Capsule endoscopy seems to be an expanding method for investigating the gut.
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paper_title: An asymmetric resonant coupling wireless power transmission link for Micro-Ball Endoscopy

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This paper investigates the design and optimization of a wireless power transmission link targeting Micro-Ball Endoscopy applications. A novel asymmetric resonant coupling structure is proposed to deliver power to an endoscopic Micro-Ball system for image read-out after it is excreted. Such a technology enables many key medical applications with stringent requirements for small system volume and high power delivery efficiency. A prototyping power transmission sub-system of the Micro-Ball system was implemented. It consists of primary coil, middle resonant coil, and cube-like full-direction secondary receiving coils. Our experimental results proved that 200mW of power can be successfully delivered. Such a wireless power transmission capability could satisfy the requirements of the Micro-Ball based endoscopy application. The transmission efficiency is in the range of 41% (worst working condition) to 53% (best working condition). Comparing to conventional structures, Asymmetric Resonant Coupling Structure improves power efficiency by 13%.
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paper_title: Small bowel video capsule endoscopy: an overview.

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Video capsule endoscopy (VCE) is being increasingly used to investigate small bowel pathology. It is the gold standard for obscure gastrointestinal bleeding and iron deficiency anemia. VCE has been in use since 2001 and indications for its use are expanding. VCE is also a useful diagnostic tool in small bowel Crohn's disease, celiac disease, surveillance of polyps, small bowel malignancy and drug-induced small bowel injury. Although VCE is considered a safe and easy procedure, there are a few limitations. These include cost, capsule retention and inability to take a biopsy and perform any therapeutic maneuvers. Contraindications for VCE include pregnancy, patients with a swallowing disorder, history of previous abdominal surgery or concurrent abdomino-pelvic irradiation. This is an overview of VCE, its role and indications in clinical practice, potential complications and contraindications, as well as the ongoing and expected advances in the field.
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paper_title: Active actuation system of wireless capsule endoscope based on magnetic field

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Capsule endoscopy, as a new technology involving integrated circuits, MEMS, image processing, radio transmission, and power supply, makes a significant break-through in the GI examination and therapy. However, there are still many problems for the applications of capsule endoscopes, especially for control or actuation of the capsule movement. Therefore, we propose a new technique to address these problems. First, we enclose a permanent magnet in the capsule, to find its localization and orientation by detecting the magnetic field distribution produced by the magnet, and this magnetic field can be measured by magnetic sensors. Second, we place 3 pairs of Helmholtz coils in spatial orthodox way around the human body, to form a rotative magnetic field, to actuate the magnet, so the capsule is propelled. In our system, the permanent magnet plays a role of both the localization, and actuation. This system is in closed-loop mode by using the feedback message from the localization system. Compared with other MEMS solutions, our actuation system has many advantages: no power supply, small space occupation, high-accuracy for positioning, and it will provide the medical doctor a feasible way to control capsule movement wirelessly.
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paper_title: Small-scale energy harvesting through thermoelectric, vibration, and radiofrequency power conversion

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As sensors for a wide array of applications continue to shrink and become integrated, increasing attention has been focused on creating autonomous devices with long-lasting power supplies. To achieve this, energy will have to be harvested from the sensors’ environment. An energy harvesting device can power the sensor either directly or in conjunction with a battery. Presented herein is a review of three types of energy harvesting with focus on devices at or below the cm3 scale. The harvesting technologies discussed are based on the conversion of temperature gradients, mechanical vibrations, and radiofrequency waves. Operation principles, current state of the art, and materials issues are presented. In addition, requirements and recent developments in power conditioning for such devices are discussed. Future challenges specific to miniaturization are outlined from both the materials and device perspectives.
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paper_title: Application of a magnetic dipole modelling approach to the problem of tracking a capsule endoscope

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This paper shows that a small cylindrical permanent magnet enclosed inside a capsule can be used as a marker in endoscopy procedures. A modelling approach that treats the magnetic marker as a magnetic dipole is presented and an efficient, non-invasive, and low-cost localization method to track the capsule is proposed. A sensor array consisting of 16 magneto-resistive sensors is used to measure the magnetic field at multiple predetermined positions. The position and orientation parameters of the marker are calculated by minimizing the error between calculated and measured values of the field. The Levenberg-Marquardt optimization method is used to solve the inverse magnetic problem. Results are presented that show that the method is accurate and can be used for real-time tracking. The technique is applicable in environments that do not contain ferromagnetic materials as is the case for the human body.
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paper_title: An Earthworm-Like Robotic Endoscope System for Human Intestine: Design, Analysis, and Experiment

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The existing endoscope brings too much discomfort to patients because its slim and rigid rod is difficult to pass through alpha, gamma loop of the human intestine. A robotic endoscope, as a novel solution, is expected to replace the current endoscope in clinic. A microrobotic endoscope based on wireless power supply was developed in this paper. This robot is mainly composed of a locomotion mechanism, a wireless power supply subsystem, and a communication subsystem. The locomotion mechanism is composed of three liner-driving cells connected with each other through a two-freedom universal joint. The wireless power supply subsystem is composed of a resonance transmit coil to transmit an alternating magnetic field, and a secondary coil to receive the power. Wireless communication system could transmit the image to the monitor, or send the control commands to the robot. The whole robot was packaged in the waterproof bellows. Activating the three driving cells under some rhythm, the robot could creep forward or backward as a worm. A mathematic model is built to express the energy coupling efficiency. Some experiments are performed to test the efficiency and the capability of energy transferring. The results show the wireless energy supply has enough power capacity. The velocity and the navigation ability in a pig intestine were measured in in vitro experiments. The results demonstrated this robot can navigate the intestine easily. In general, the wireless power supply and the wireless communication remove the need of a connecting wire and improve the motion flexibility. Meanwhile, the presented locomotion mechanism and principle have a high reliability and a good adaptability to the in vitro intestine. This research has laid a good foundation for the real application of the robotic endoscope in the future.
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paper_title: Wireless power and data transmission for robotic capsule endoscopes

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Capsular endoscopy is a promising alternative to traditional gastro-intestinal (GI) examination techniques launched in the late '90s. Although this approach has the potential to significantly change the examination procedure, the performance of currently available capsules is still too poor to take over traditional techniques. A major constraint that hinder the breakthrough of these devices is the limited power amount that can be stored into a tiny pill. Most commercial capsules use two watch batteries that can only provide an average power of 25 mW for about 6 hours, certainly not sufficient for a high resolution video stream or advanced robotic features. An inductive powering system has been developed which was proven to safely support the wireless transfer of over 300 mW. The system relies on a set of orthogonal ferrite (3D) coils, embedded in the capsule, and an external unit based on a Helmholtz coil driven by a class E amplifier. Control data can be sent through the inductive link by modulating the power carrier, whereas a dedicated high data rate RF link is used to transfer the images from the capsule to the base station. Besides evaluating the compatibility with radio transmission, several demonstrators were assembled combining the wireless powering system with various capsule dedicated modules.
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paper_title: Capsule Endoscopy: From Current Achievements to Open Challenges

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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: Looking forwards: not necessarily the best in capsule endoscopy?

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Since its first description in the early 2000s [1], the capsule endoscope (CE) has been consolidated in all diagnostic algorithms for the assessment of the small-bowel [2]. Nevertheless, the issue of the diagnostic yield (DY) in wireless, hence non-steerable, CE continues to trouble physicians [3-6]. It is already known that a broader angle (field) of view is associated with higher DY [7-10]. Most of the current CE models/systems employ a single-dome viewing philosophy, in which the lens with image sensor and light source are aligned in a single (and in theory the moving) direction, with a field of vision that varies 140°-170° [2]. Therefore, the lens should be of a wide-angle type, often associated with image distortion. Moreover, a combination of other factors such as the speed of small-bowel transit [8,11], and the cleansing of the small bowel [12] appear to significantly impact on the DY. ::: ::: Therefore, we read with great interest the study on the use of a newly developed CE (CapsoCam®SV-1; Capso Vision™, Saratoga, CA, USA) with panoramic (side-viewing) capability-by Friedrich et al [13]. CapsoCam® boasts an innovative design that employs four cameras (CMOS), each with an approximately 90° field of view, facing the sides of the capsule. Each camera obtains 5 frames-per sec (fps) for the first 2 h and thereafter 3 fps, resulting in 20 and 12 fps, respectively. CapsoCam®SV-1 (11×31mm) dimensions are similar to the PillCam®COLON (Given® Imaging Ltd, Yoqneam, Israel). Theoretically, the obtained images are more stable due to reduced camera motion and also reduced mucosal movement [14]. Moreover, the true wire-free (a step beyond “wireless”) design aims to enhance patient comfort and minimize procedural / maintenance costs [13,14]. Interestingly, CapsoCam®SV-1 employs motion sense technology, powered by an auto illumination controller to provide optimal light as required by the cameras, and has a battery life of ~15 h [13,14]. Furthermore, the Flash EPROM storage device does not generate or transmit radiofrequency (RF) waves, although recent evidence confirms the safety of capsule endoscopy in patients with implanted devices [15,16]. ::: ::: In their study, Friedrich et al [13] recruited 33 patients with a mean age of 45 years, referred for CE for a combination of indications including: anemia: 17, inflammatory bowel disease: 12, abdominal pain: 6, MALToma: 1 and elevated tumor markers: 2. ::: ::: One group of patients (n=23), swallowed the capsules immediately following colonoscopy. They were prepared with 150 mL of Sodium Picosulfate (SP) and 3-4 L of water. They were allowed clear fluids. The morning of the procedures they were given 150 mL SP and 1 L of water. The other group (n=8), who went straight on to CE were prepped with 2 L of polyethylene glycol solution in the afternoon before the examination. All patients received 20 mg of Metoclopramide and 160 mg of Simethicone 30 min before ingestion of the capsule. Average cleanliness of the small bowel was 3.3 ±0.5 (on a 1-4 scale). The quality of the images was scored by 3 independent gastroenterologists and the mean overall score was 3.6 ±0.06 (on a 0-4 scale) with 91.4% of images evaluated as good or excellent. ::: ::: The authors used the duodenal papilla (ampulla of Vater, AoV) as the only landmark in small-bowel. Identification of the duodenal papilla was possible in 22 patients (71%). The AoV was to be seen in 3.1±1.8 frames (median: 2.0 frames). Small-bowel transit time was 258 ±136 min (range: 40-621 min). Mean number of small-bowel frames was 14.209±7.671. Video review time was 48.8 ±11.4 min.
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paper_title: A wireless energy link for endoscopy with end-fire helix emitter and Load-Adaptive power converter

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This paper proposes a new Wireless-Powered Micro-Ball Endoscopy system, in which wireless power is emitted from an emitter array embedded in a floor and resonantly relayed by a passive wireless power jacket on patients. Comparing to other wireless powering endoscopy systems, both the patients' freedom of movement and the power efficiency are improved. To enhance the power efficiency, an End-Fire Helix Emitter is proposed, which is a fundamentally novel structure used for generating near field alternative magnetic field with high efficiency. This paper also proposes a Load-Adaptive power converter circuit to keep optimal power efficiency by matching the varied load impedance. A prototyping design is fabricated. At the frequency of 24.05MHz, the power efficiency of transmission from floor to wireless jacket is 44.6%, and the overall energy efficiency from floor to Endoscopic Micro-Ball is 2.5% at best.
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paper_title: Design and Rolling Locomotion of a Magnetically Actuated Soft Capsule Endoscope

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This paper proposes a magnetically actuated soft capsule endoscope (MASCE) as a tetherless miniature mobile robot platform for diagnostic and therapeutic medical applications inside the stomach. Two embedded internal permanent magnets and a large external magnet are used to actuate the robot remotely. The proposed MASCE has three novel features. First, its outside body is made of soft elastomer-based compliant structures. Such compliant structures can deform passively during the robot-tissue contact interactions, which makes the device safer and less invasive. Next, it can be actively deformed in the axial direction by using external magnetic actuation, which provides an extra degree of freedom that enables various advanced functions such as axial position control, drug releasing, drug injection, or biopsy. Finally, it navigates in three dimensions by rolling on the stomach surface as a new surface locomotion method inside the stomach. Here, the external attractive magnetic force is used to anchor the robot on a desired location, and the external magnetic torque is used to roll it to another location, which provides a stable, continuous, and controllable motion. The paper presents design and fabrication methods for the compliant structures of the robot with its axial deformation and position control capability. Rolling-based surface locomotion of the robot using external magnetic torques is modeled, and its feasibility is tested and verified on a synthetic stomach surface by using a magnetically actuated capsule endoscope prototype.
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paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

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Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
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paper_title: Gastric cancer with large bowel obstruction as the first presentation: A case report

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Gastric adenocarcinoma with a large bowel obstruction as the first presentation of the condition is rare. The present study describes the case of a 59-year-old female who was diagnosed with a large bowel obstruction that was caused by gastric adenocarcinoma. The patient suffered from abdominal pain and had not defecated for 15 days. The patient had no significant medical history. The right epigastric region was slightly tender and active bowel sounds were identified. A computed tomography (CT) scan revealed a dilated fluid-filled colon with a thickened wall and adjacent fat infiltration. An upper gastrointestinal endoscopy revealed that the margin and gastric mucosa in the antrum were raised and thickened without evidence of ulcerative lesions. The patient underwent surgery and was administered adjuvant chemotherapy. The patient was followed-up for 18 months without recurrence of the tumor. This study demonstrates that the presentation of gastric cancer may vary.
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paper_title: A wireless power supply system for robotic capsular endoscopes

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Abstract In expanding capsular endoscopy from a mere passive screening tool to a multipurpose robot, batteries become inadequate. Wireless power supply overcomes the problem of power shortage and enables the integration of high-power modules. This work focuses on wireless inductive power transfer and its technology optimization in size, materials and efficiency. A user friendly and stable external unit has been developed that supports power and data transmission through the downlink (from the external world to the capsule). The possibility of using a Helmholtz coil at the primary side has been investigated and a preliminary set-up has been implemented. The ongoing development on 3D coil geometries is further refined by the introduction of a laser machined ferrite core to boost the amount of available power. It is demonstrated that 330 mW can be transferred to a capsule under all possible orientations, within a 0.48 cm 3 volume.
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paper_title: Portable Wireless Power Transmission System of a Video Capsule Endoscopy: Design and Realization

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Video capsule endoscopy, as a new technology, has brought a revolution in the diagnosis of gastrointestinal tract diseases. However, power limitation has become a great problem that restricts its development and application. Meanwhile, the diagnostic procedure usually lasts more than ten hours or more. So, a portable wireless power transmission system based on inductive coupling is designed for the video capsule endoscopy. The system consists of a double layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 150 mW usable power can be transmitted under the worst geometrical conditions, which totally meet requirements of the video capsule endoscopy. On the other hand, the weight of the wireless power transmission system is only 4.98kg, which realized the portability.
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paper_title: The present and future state of nonpulsatile artificial heart technology

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The difference between Japan and the United States in the roles of the artificial heart, domestic needs for the artificial heart, and classification of artificial hearts according to configuration and generation are described. The present trend in the third generation is toward long-term nonpulsatile artificial hearts. Individual characteristics of the second and third generations are described, and the performance data are listed for all pulsatile and nonpulsatile pumps in the world.
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paper_title: Therapeutic Capsule Endoscopy: Opportunities and Challenges

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The increasing demand for non-invasive (or less-invasive) monitoring and treatment of medical conditions has attracted both physicians and engineers to work together and investigate new methodologies. Wireless capsule endoscopy is a successful example of such techniques which has become an accepted routine for diagnostic inspection of the gastrointestinal tract. This method offers a non-invasive alternative to traditional endoscopy and provides the opportunity for exploring distal areas of the small intestine which are otherwise not accessible. Despite these advantages, wireless capsule endoscopy is still limited in functionality compared to traditional endoscopy. Wireless capsule endoscopes with advanced functionalities, such as biopsy or drug delivery, are highly desirable. In this article, the current status of wireless capsule endoscopy is reviewed together with some of its possible therapeutic applications as well as the existing challenges.
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paper_title: Energy scavenging for mobile and wireless electronics

paper_content:

Energy harvesting has grown from long-established concepts into devices for powering ubiquitously deployed sensor networks and mobile electronics. Systems can scavenge power from human activity or derive limited energy from ambient heat, light, radio, or vibrations. Ongoing power management developments enable battery-powered electronics to live longer. Such advances include dynamic optimization of voltage and clock rate, hybrid analog-digital designs, and clever wake-up procedures that keep the electronics mostly inactive. Exploiting renewable energy resources in the device's environment, however, offers a power source limited by the device's physical survival rather than an adjunct energy store. Energy harvesting's true legacy dates to the water wheel and windmill, and credible approaches that scavenge energy from waste heat or vibration have been around for many decades. Nonetheless, the field has encountered renewed interest as low-power electronics, wireless standards, and miniaturization conspire to populate the world with sensor networks and mobile devices. This article presents a whirlwind survey through energy harvesting, spanning historic and current developments.
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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: Clinical application of wireless capsule endoscopy

paper_content:

BACKGROUND: Diagnostic modalities for identifying lesions within the small bowel have been quite limited. Wireless capsule endoscopy (WCE) is a new, innovative technique that can detect very small mucosal lesions in the entire small bowel and can be used in the outpatient setting. The present study explored the diagnostic value, tolerance and safety of WCE in the identification of small bowel pathology that was not detected with conventional small bowel imaging studies. ::: ::: ::: ::: METHODS: From May through September 2002, 15 patients with suspected small bowel diseases were prospectively examined, Of them, 12 presented with persistent obscure gastrointestinal bleeding and negative findings on upper endoscopy, colonoscopy, small bowel radiography, and bleeding-scan scintig-raphy or mesenteric angiography. ::: ::: ::: ::: RESULTS: Wireless capsule endoscopy identified pathologic small bowel findings in 11 of the 15 patients (73%): angioectasias, Dieulafoy's lesion, polypoid lesion, submucosal mass, Crohn's disease, carcinoid tumor, lipoma, aphthous ulcer, and hemorrhagic gastritis; four of the patients had two lesions. The images displayed were considered to be good. The capsule endoscopes remained in the stomach for an average of 82 min (range 6−311 min) and the mean transit time in the small bowel was 248 min (range 104−396 min). The mean time of recording was 7 h 29 min (from 5 h to 8 h 30 min). The mean time to reach the cecum was 336 min (180−470 min). The average number of the images transmitted by the capsule was 57 919 and the average time the physician took to review the images transmitted by the capsule was 82 min (range 30−120 min). The average time of elimination of the capsule was 33 h (range 24−48 h). All 15 patients reported that the capsule was easy to swallow, painless, and preferable to conventional endoscopy. No complications were observed. ::: ::: ::: ::: CONCLUSIONS: Wireless capsule endoscopy is safe, well tolerated, and useful for identifying occult lesions of the small bowel, especially in patients who present with obscure gastrointestinal bleeding.
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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: Swallowable Wireless Capsule Endoscopy: Progress and Technical Challenges

paper_content:

Wireless capsule endoscopy (WCE) offers a feasible noninvasive way to detect the whole gastrointestinal (GI) tract and revolutionizes the diagnosis technology. However, compared with wired endoscopies, the limited working time, the low frame rate, and the low image resolution limit the wider application. The progress of this new technology is reviewed in this paper, and the evolution tendencies are analyzed to be high image resolution, high frame rate, and long working time. Unfortunately, the power supply of capsule endoscope (CE) is the bottleneck. Wireless power transmission (WPT) is the promising solution to this problem, but is also the technical challenge. Active CE is another tendency and will be the next geneion of the WCE. Nevertheless, it will not come true shortly, unless the practical locomotion mechanism of the active CE in GI tract is achieved. The locomotion mechanism is the other technical challenge, besides the challenge of WPT. The progress about the WPT and the active capsule technology is reviewed.
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paper_title: Diagnostic yield of small bowel capsule endoscopy depends on the small bowel transit time

paper_content:

AIM: To investigate whether the small bowel transit time (SBTT) influences the diagnostic yield of capsule endoscopy (CE). ::: ::: METHODS: Six hundred and ninety-one consecutive CE procedures collected in a database were analyzed. SBTT and CE findings were recorded. A running mean for the SBTT was calculated and correlated to the diagnostic yield with a Spearman’s correlation test. Subgroup analyses were performed for the various indications for the procedure. ::: ::: RESULTS: There was a positive correlation between the diagnostic yield and SBTT (Spearman’s rho 0.58, P < 0.01). Positive correlations between diagnostic yield and SBTT were found for the indication obscure gastrointestinal bleeding (r = 0.54, P < 0.01), for polyposis and carcinoid combined (r = 0.56, P < 0.01) and for the other indications (r = 0.90, P <0.01), but not for suspected Crohn’s disease (r = -0.40). ::: ::: CONCLUSION: The diagnostic yield in small bowel capsule endoscopy is positively correlated with the small bowel transit time. This is true for all indications except for suspected Crohn’s disease.
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paper_title: 1 A Multi-Coil Inductive Powering System for an Endoscopic Capsule with Vibratory Actuation

paper_content:

Abstract The transformation of endoscopic capsules from passive tools to robotic devices is increasingly attracting the interest of the research community. In the past few years, significant progress has been achieved in the areas of microelectronics and electromechanical systems. However, their use in commercial endoscopic capsules is hindered by their increased power demands, which, to present, cannot be adequately met by embedded power sources. A 3D inductive powering module, providing over 300 mW to the capsule, overcomes these limitations, thus enabling the integration of active locomotion systems, as well as advanced diagnostic and therapeutic features. This is demonstrated in the present study by a capsule prototype employing the wireless powering unit to drive an onboard vibratory motor for capsule propulsion. Simplified models are employed to illustrate the main principle of this vibratory locomotion scheme. Experimental results, involving movement of the prototype in various environments, confirm both the effectiveness of the wireless powering system, and the efficacy of the vibratory locomotion scheme.
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paper_title: Inductive powering of a freely moving system

paper_content:

Abstract To inductively feed a freely moving system in a confined space, two basic approaches are conceivable. One is to provide with three or more differently directed magnetic fields from the outside. The other is to use three or more differently oriented receiving coils. In this text, the achievable efficiency under worst-case conditions is investigated for both options. Some basic working methodologies are handed as a means to identify the worst-case conditions. The wireless endoscope – or swallowable camera-pill – will serve as an example for which both approaches will be compared. Based on the conclusions of this comparison, an inductive link is realized and the predicted efficiency is verified through measurement.
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paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

paper_content:

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
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paper_title: Micro-system Design for Wireless Endoscopy System

paper_content:

This paper proposes a micro-system design for the wireless endoscopic capsule, which assures that the capsule has small size(less than 25 mm*10 mm), can implement the diagnosis of whole human digestive tract and provide real time endoscopic image monitoring. The designs of two core hardware parts inside the capsule, low power analog-digital mix-mode single-chip and micro-antenna are discussed in detail. A new automatic retransmission request (ARQ) communication scheme is proposed for the high quality image communication system. The micro-antenna design with less than 9 mm diameter is implemented. The digital circuits have been verified on FPGAs and analog circuits have been simulated. The analog-digital mix-mode single-chip has been implemented in 0.18 mum CMOS process
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paper_title: Development of a micro-robot for endoscopes based on wireless power transfer.

paper_content:

This paper develops a new prototype of a wireless micro-robot system for endoscopes. The micro-robot we have fabricated and tested is able to propel itself in the intestine of pig. Its autonomous manner is earthworm-like and driven by linear actuators based on a DC motor. Unlike with conventional micro-robot endoscopes, that wireless module is used for communicating and power transfer. The experimental results show that the driving force of the linear actuator can reach up to 2.55 N and the stable supplying power is up to 480 mW DC power for the receiving coil in the proposed system, which all fulfill the need of the micro-robot system. The micro-robot can creep reliably in the small and large intestine of a pig. The video communication module embedded in the head of the micro-robot can capture the inner picture of the intestine and broadcast it to PC in real-time.
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paper_title: A wireless power supply system for robotic capsular endoscopes

paper_content:

Abstract In expanding capsular endoscopy from a mere passive screening tool to a multipurpose robot, batteries become inadequate. Wireless power supply overcomes the problem of power shortage and enables the integration of high-power modules. This work focuses on wireless inductive power transfer and its technology optimization in size, materials and efficiency. A user friendly and stable external unit has been developed that supports power and data transmission through the downlink (from the external world to the capsule). The possibility of using a Helmholtz coil at the primary side has been investigated and a preliminary set-up has been implemented. The ongoing development on 3D coil geometries is further refined by the introduction of a laser machined ferrite core to boost the amount of available power. It is demonstrated that 330 mW can be transferred to a capsule under all possible orientations, within a 0.48 cm 3 volume.
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paper_title: Portable Wireless Power Transmission System of a Video Capsule Endoscopy: Design and Realization

paper_content:

Video capsule endoscopy, as a new technology, has brought a revolution in the diagnosis of gastrointestinal tract diseases. However, power limitation has become a great problem that restricts its development and application. Meanwhile, the diagnostic procedure usually lasts more than ten hours or more. So, a portable wireless power transmission system based on inductive coupling is designed for the video capsule endoscopy. The system consists of a double layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 150 mW usable power can be transmitted under the worst geometrical conditions, which totally meet requirements of the video capsule endoscopy. On the other hand, the weight of the wireless power transmission system is only 4.98kg, which realized the portability.
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paper_title: High-Efficiency Wireless Power Transfer for Biomedical Implants by Optimal Resonant Load Transformation

paper_content:

Wireless power transfer provides a safe and robust way for powering biomedical implants, where high efficiency is of great importance. A new wireless power transfer technique using optimal resonant load transformation is presented with significantly improved efficiency at the cost of only one additional chip inductor component. The optimal resonant load condition for the maximized power transfer efficiency is explained. The proposed technique is implemented using printed spiral coils with discrete surface mount components at 13.56 MHz power carrier frequency. With an implantable coil having an area of 25 mm × 10 mm and a thickness of 0.5 mm, the power transfer efficiency of 58% is achieved in the tissue environment at 10-mm distance from the external coil. Compared to previous works, the power efficiency is much higher and the structure is compact with planar integration, easy to tune, and suitable for batch production, as well as biocompatible owing to no incorporation of ferromagnetic core.
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paper_title: Energy sources and their development for application in medical devices.

paper_content:

Electronic medical devices have become an indispensable part of modern healthcare. Currently, a wide variety of electronic medical devices are being used to monitor physiological parameters of the body, perform therapy and supplement or even entirely replace complex biological functions. Cardiac pacemakers, cardioverter-defibrillators and cochlear implants are a few examples of such medical devices. Proper functionality of these devices relies heavily on the continuous supply of a sufficient amount of electricity to them. In this sense, a reliable, safe and convenient method for the provision of energy is very crucial. Various approaches have been developed to fulfil the divergent and challenging energy requirements of medical devices. In this article, we present a brief overview of the energy requirements of medical devices and review the existing and emerging energy sources for application in these devices, particularly wearable and implantable devices.
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paper_title: A Low-Frequency Versatile Wireless Power Transfer Technology for Biomedical Implants

paper_content:

Implantable biomedical sensors and actuators are highly desired in modern medicine. In many cases, the implant's electrical power source profoundly determines its overall size and performance. The inductively coupled coil pair operating at the radio-frequency (RF) has been the primary method for wirelessly delivering electrical power to implants for the last three decades. Recent designs significantly improve the power delivery efficiency by optimizing the operating frequency, coil size and coil distance. However, RF radiation hazard and tissue absorption are the concerns in the RF wireless power transfer technology (RF-WPTT) [4], [5]. Also, it requires an accurate impedance matching network that is sensitive to operating environments between the receiving coil and the load for efficient power delivery. In this paper, a novel low-frequency wireless power transfer technology (LF-WPTT) using rotating rare-earth permanent magnets is demonstrated. The LF-WPTT is able to deliver 2.967 W power at ~ 180 Hz to an 117.1 Ω resistor over 1 cm distance with 50% overall efficiency. Because of the low operating frequency, RF radiation hazard and tissue absorption are largely avoided, and the power delivery efficiency from the receiving coil to the load is independent of the operating environment. Also, there is little power loss observed in the LF-WPTT when the receiving coil is enclosed by non-magnetic implant-grade stainless steel.
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paper_title: Omnidirectional Inductive Powering for Biomedical Implants

paper_content:

Omnidirectional Inductive Powering for Biomedical Implants investigates the feasibility of inductive powering for capsule endoscopy and freely moving systems in general. The main challenge is the random position and orientation of the power receiving system with respect to the emitting magnetic field. Where classic inductive powering assumes a predictable or fixed alignment of the respective coils, the remote system is now free to adopt just any orientation while still maintaining full power capabilities. Before elaborating on different approaches towards omnidirectional powering, the design and optimisation of a general inductive power link is discussed in all its aspects. Special attention is paid to the interaction of the inductive power link with the patient s body. Putting theory into practice, the implementation of an inductive power link for a capsule endoscope is included in a separate chapter.
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paper_title: Wireless power transfer via strongly coupled magnetic reso- nances

paper_content:

Using self-resonant coils in a strongly coupled regime, we experimentally demonstrated efficient nonradiative power transfer over distances up to 8 times the radius of the coils. We were able to transfer 60 watts with ∼40% efficiency over distances in excess of 2 meters. We present a quantitative model describing the power transfer, which matches the experimental results to within 5%. We discuss the practical applicability of this system and suggest directions for further study.
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paper_title: A wireless power transmission system for an active capsule endoscope for colon inspection

paper_content:

Multipurpose active capsule endoscopes (ACE) have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. In order to deliver stable and sufficient energy safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a double-layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 500 mW usable power can be transmitted under the worst geometrical conditions and the safety restraints in a volume of Φ13 × 13 mm. The wireless power transmission system is integrated to an ACE and applied in animal experiments. The designed wireless power transmission is proved to be feasible and potentially safe in a future application.
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paper_title: A stable wireless energy transmission system for gastrointestinal microsystems.

paper_content:

A wireless energy transmission system using a Helmholtz primary coil outside and a 3-dimensional secondary coil inside the body is introduced. It is designed to transmit stable power to a gastrointestinal microsystem regardless of its position and orientation when working in the gastric tract. Up to 310 mW of usable DC power can be delivered under worst-case geometrical conditions. Measured data of the system performance are presented and evaluated.
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paper_title: A wireless power transmission system for an active capsule endoscope for colon inspection

paper_content:

Multipurpose active capsule endoscopes (ACE) have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. In order to deliver stable and sufficient energy safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a double-layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 500 mW usable power can be transmitted under the worst geometrical conditions and the safety restraints in a volume of Φ13 × 13 mm. The wireless power transmission system is integrated to an ACE and applied in animal experiments. The designed wireless power transmission is proved to be feasible and potentially safe in a future application.
---
paper_title: 1 A Multi-Coil Inductive Powering System for an Endoscopic Capsule with Vibratory Actuation

paper_content:

Abstract The transformation of endoscopic capsules from passive tools to robotic devices is increasingly attracting the interest of the research community. In the past few years, significant progress has been achieved in the areas of microelectronics and electromechanical systems. However, their use in commercial endoscopic capsules is hindered by their increased power demands, which, to present, cannot be adequately met by embedded power sources. A 3D inductive powering module, providing over 300 mW to the capsule, overcomes these limitations, thus enabling the integration of active locomotion systems, as well as advanced diagnostic and therapeutic features. This is demonstrated in the present study by a capsule prototype employing the wireless powering unit to drive an onboard vibratory motor for capsule propulsion. Simplified models are employed to illustrate the main principle of this vibratory locomotion scheme. Experimental results, involving movement of the prototype in various environments, confirm both the effectiveness of the wireless powering system, and the efficacy of the vibratory locomotion scheme.
---
paper_title: Inductive powering of a freely moving system

paper_content:

Abstract To inductively feed a freely moving system in a confined space, two basic approaches are conceivable. One is to provide with three or more differently directed magnetic fields from the outside. The other is to use three or more differently oriented receiving coils. In this text, the achievable efficiency under worst-case conditions is investigated for both options. Some basic working methodologies are handed as a means to identify the worst-case conditions. The wireless endoscope – or swallowable camera-pill – will serve as an example for which both approaches will be compared. Based on the conclusions of this comparison, an inductive link is realized and the predicted efficiency is verified through measurement.
---
paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

paper_content:

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
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paper_title: An active endoscopic robot based on wireless power transmission and electromagnetic localization

paper_content:

Background ::: ::: Conventional endoscopes have the disadvantages of causing pain to patients because of their large dimensions and allowing incomplete inspection because of their limited power. ::: ::: ::: ::: Methods ::: ::: An active inchworm-like endoscopic robot has been designed, which is based on electromagnetic localization and synthesis of magnetic field strength vectors. ::: ::: ::: ::: Results ::: ::: The efficiency of wireless power transmission can be kept above 0.9% when the power-receiving coil is at arbitrary position and orientation. The position error of localization is < 10 mm and the average error of orientation angle is 2° . When the robot moves through part of the porcine colon, images are transmitted outwards continuously at a speed of 30 fps and the temperature rise of the colon is < 1 °C. By simulation, the electromagnetic exposures to the human body are lower than international standards. ::: ::: ::: ::: Conclusions ::: ::: The endoscopic robot is a promising tool for use by doctors, although further experiments and improvements need to be done. Copyright © 2008 John Wiley & Sons, Ltd.
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paper_title: An inductive power link for a wireless endoscope

paper_content:

Abstract An inductive link is presented that can handle freedom of motion. The envisaged application is to power a wireless camera capsule used for non-invasive visual inspection of the small bowel. Up to 150 mW of usable dc power can be delivered to the capsule for the entire duration of its travel along the gastric track. The outer dimensions of the power receiver compartment inside the capsule are O 10 mm × 13 mm. The power efficiency of the link is measured to be 1% under worst-case geometrical conditions. The issue of patient's health and safety regarding exposure to the electromagnetic field is addressed. To this purpose, an experimental method is applied to predict specific absorption rates. Conversely, the effect of biological tissue on link performance and practical workability is evaluated as well. Electric shielding of the transmitter coil is applied to reduce biological tissue interaction. In this way, appliance on a living subject is made both safe and practically feasible.
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paper_title: Wireless power transfer system for capsule endoscopy based on strongly coupled magnetic resonance theory

paper_content:

Capsule endoscopy is a new technique that allows complete exploration of the small intestine, and widely used all over the world, for its convenience and less pains compared with traditional endoscopy. However, the limited power supplies of batteries handicap the development of capsule endoscopy. This paper presents a novel wireless power transfer system for the capsule endoscopy utilizing the strongly coupled magnetic resonances theory. The wireless power transfer system consists of four coils, an excitation source and a load. In order to evaluate the system performance, experiments were carried out in which the working frequency is determined at 8.2MHz. The results demonstrate that the distance between two sets of transmission coils have great effect on the system efficiency and the maximal system efficiency can reach 26.14%. Therefore, this power supply system has a promising prospect on wireless power transfer for capsule endoscopy. Improving the quality factor of coils can effectively increase the efficiency of the system, which is the key to the future work.
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paper_title: A Class-E driven inductive power delivery system covering the complete upper body

paper_content:

Abstract The design, simulation and implementation of a dedicated Class-E driver for inductive power transfer is presented. Whereas focus is placed on wireless endoscopy, other upper body monitoring applications can be powered simultaneously. The driver is developed to generate a sinusoidal current signal through a coil, for the generation of an alternating magnetic field at 1 MHz with a field intensity of about 300 μT. The volume within the coil, implemented in a Helmholtz configuration, wherein this magnetic field is guaranteed, allows to cover a volume up to ∼0.2 m 3 . This is an improvement by a factor of 20 compared to previous work [1] and sufficiently large to cover the full upper body of patients. The magnetic field thereby generated, is adequate to provide up to 300 mW of power to previously developed capsules, in all possible orientations. Patient safety and solutions to reduce parasitic influences are addressed briefly.
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paper_title: Three-dimensional power receiver for in vivo robotic capsules

paper_content:

A three-dimensional wireless power receiver is introduced in this study for in vivo robotic capsules. It is designed to retrieve hundreds of milliwatts of power, regardless of orientation relative to the time-varying magnetic field generated by the external transmitter outside a test animal body. Design issues, such as antenna structure and rectification topology, are discussed, considering limitations of physical space. Various design parameters are implemented and experimented. A selected design is implemented and tested for power variations on rotational positions relative to the transmitter magnetic field. The presented receiver delivers more than 300 mW of power regardless of its orientation. A test capsule is assembled with LED load for in vivo experiments. Visual verification of the light intensity of LED shows that the power-receiving performance of the receiver is not affected inside the animal body.
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paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

paper_content:

Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
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paper_title: An efficiency-enhanced wireless power transfer system with segmented transmitting coils for endoscopic capsule

paper_content:

This paper proposes a new wireless power transfer (WPT) system for the endoscopic capsule. In the system, a group of vertically segmented primary coils around the human body are adopted as the transmitting coils. According to the position of the endoscopic capsule, one of the transmitting coils is intelligently selected to transfer the power with the highest efficiency. This paper also presents a coil selection and control algorithm for the unique WPT system. Compared with the conventional design, the calculated transmission efficiencies of the new solution at the best and worst points of the body are enhanced by 53.5% and 138% respectively. And the average efficiency of the proposed solution is about 3.8%.
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paper_title: Power transmission for gastrointestinal microsystems using inductive coupling.

paper_content:

Much research on the development of a robotic capsule and microrobot for the diagnosis of gastrointestinal diseases has been carried out. The powering of these microsystems is becoming very important as the implementation of such systems is becoming more feasible by advances in relevant technologies. A wireless power transmission system employing two coils, based on inductive coupling, is discussed in this note. The coupling coefficient between the two coils was measured on axial, lateral and pitch misalignment. The power transmission efficiency was deduced and optimized by selecting proper tuning capacitors and transmission frequency. A serial resonant circuit (SRC) on a receiving side is more adaptive by comparison with parallel resonant circuit (PRC) topology. A multi-receiving coil structure was proposed and examined in an attempt to resolve the orientation indetermination problem of a receiving coil. Experiments show that a dc power level up to 170 mW, with an efficiency of 1.3%, could be steadily received when the receiving coil was placed at the center of the transmitting coil, which can meet the requirement for electric power of some microsystems.
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paper_title: Analyzing the uniformity of the generated magnetic field by a practical one-dimensional Helmholtz coils system.

paper_content:

Using the Helmholtz coils system is one of the most suitable approaches which have been introduced for generating uniform magnetic fields. In this paper, uniformity of the generated magnetic field by a practical one-dimensional (1D) Helmholtz coils system has been analyzed, mathematically. For this purpose, relationships between the magnetic field uniformity and different practical unavoidable mismatches have been extracted. The theoretical analysis clearly demonstrates the effect of assembly misalignments and manufacturing mismatches on the magnetic field achieved by a practical 1D Helmholtz coils system. The given analyses have been confirmed by the experimental results which are in good agreement with the calculated values. This analysis and the experimental results illustrate that to achieve a very high uniform magnetic field, practical assembly misalignments, and manufacturing mismatches must be as small as possible, and the background magnetic field distortion must be avoided, too. The results of this work are important in the design of instruments and systems where Helmholtz coils are used.
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paper_title: Design and Development of Low-Loss Transformer for Powering Small Implantable Medical Devices

paper_content:

Small implantable medical devices, such as wireless capsule endoscopes, that can be swallowed have previously been developed. However, these devices cannot continuously operate for more than 8 h because of battery limitations; moreover, additional functionalities cannot be introduced. This paper proposes a design method for a high-efficiency energy transmission transformer (ETT) that can transmit energy transcutaneously to small implantable medical devices using electromagnetic induction. First, the authors propose an unconventional design method to develop such a high-efficiency ETT. This method can be readily used to calculate the exact transmission efficiency for changes in the material and design parameters (i.e., the magnetic material, transmission frequency, load resistance, etc.). Next, the ac-to-ac energy transmission efficiency is calculated and compared with experimental measurements. Then, suitable conditions for practical transmission are identified. A maximum efficiency of 33.1% can be obtained at a transmission frequency of 500 kHz and a receiving power of 100 mW for a receiving coil size of ?5 mm × 20 mm. Future design optimization is possible by using this method.
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paper_title: Ingestible Wireless Capsule Technology: A Review of Development and Future Indication

paper_content:

Ingestible wireless capsule endoscopy (WCE) is the one and only painless, effective, novel, diagnostic technology for inspecting the entire gastrointestinal (GI) tract for various diseases, such as obscure gastrointestinal bleeding (OGIB), tumors, cancer, Crohn’s disease, and celiac disease. Since the development of this technology, several companies have made remarkable improvements in their clinical products, but there are still some limitations that relate to the use of conventional wired endoscopy. Some of the major limitations that currently impede its wider application include its inability to repeat the view of critical areas, working time constraints, and poor image resolution. Many research groups currently are working on ways to solve these limitations. Presently, developing the ability to control the movement of the capsule, increasing its image transmission speed, and obtaining high-quality images are the main issues in the research area. A complex capsule with some therapeutic tools for the treatment of diseases of the GI tract also is at the beginning of development for the next generation of an active medical robot. In this paper, we report the status of several activities related to WCE, including improvement of capsule technology, research progress, technical challenges, and key indicators concerning the next-generation, active, medical robot.
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paper_title: Three-dimensional power receiver for in vivo robotic capsules

paper_content:

A three-dimensional wireless power receiver is introduced in this study for in vivo robotic capsules. It is designed to retrieve hundreds of milliwatts of power, regardless of orientation relative to the time-varying magnetic field generated by the external transmitter outside a test animal body. Design issues, such as antenna structure and rectification topology, are discussed, considering limitations of physical space. Various design parameters are implemented and experimented. A selected design is implemented and tested for power variations on rotational positions relative to the transmitter magnetic field. The presented receiver delivers more than 300 mW of power regardless of its orientation. A test capsule is assembled with LED load for in vivo experiments. Visual verification of the light intensity of LED shows that the power-receiving performance of the receiver is not affected inside the animal body.
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paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

paper_content:

Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
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paper_title: A wireless power supply system for robotic capsular endoscopes

paper_content:

Abstract In expanding capsular endoscopy from a mere passive screening tool to a multipurpose robot, batteries become inadequate. Wireless power supply overcomes the problem of power shortage and enables the integration of high-power modules. This work focuses on wireless inductive power transfer and its technology optimization in size, materials and efficiency. A user friendly and stable external unit has been developed that supports power and data transmission through the downlink (from the external world to the capsule). The possibility of using a Helmholtz coil at the primary side has been investigated and a preliminary set-up has been implemented. The ongoing development on 3D coil geometries is further refined by the introduction of a laser machined ferrite core to boost the amount of available power. It is demonstrated that 330 mW can be transferred to a capsule under all possible orientations, within a 0.48 cm 3 volume.
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paper_title: Wireless power and data transmission strategies for next-generation capsule endoscopes

paper_content:

Capsular endoscopy is becoming increasingly popular as an alternative to traditional gastro-intestinal (GI) examination techniques. However, the breakthrough of these devices is hindered by the limited amount of power that can be stored in a tiny pill. Most commercial devices use two watch batteries that can only provide an average power of 25 mW for about 6 h, certainly not sufficient for advanced robotic features. A dedicated inductive powering system, operating at 1 MHz to limit the human body absorption, has been developed which was proven to support the transfer of over 300 mW. The system relies on a condensed set of orthogonal ferrite coils, embedded in the capsule, and an external unit based on a Helmholtz coil driven by a class E amplifier. Control data can be sent through the inductive link by modulating the power carrier, whereas a dedicated high data rate RF link is used to transfer the images from the capsule to the base station. Besides evaluating the compatibility with radio transmission, several demonstrators were assembled combining the wireless powering system with various locomotion strategies and LED illumination. This paper describes the design and implementation of the inductive powering system, its combination with data transmission techniques and the testing activity with other capsule-dedicated modules.
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paper_title: Power transmission for gastrointestinal microsystems using inductive coupling.

paper_content:

Much research on the development of a robotic capsule and microrobot for the diagnosis of gastrointestinal diseases has been carried out. The powering of these microsystems is becoming very important as the implementation of such systems is becoming more feasible by advances in relevant technologies. A wireless power transmission system employing two coils, based on inductive coupling, is discussed in this note. The coupling coefficient between the two coils was measured on axial, lateral and pitch misalignment. The power transmission efficiency was deduced and optimized by selecting proper tuning capacitors and transmission frequency. A serial resonant circuit (SRC) on a receiving side is more adaptive by comparison with parallel resonant circuit (PRC) topology. A multi-receiving coil structure was proposed and examined in an attempt to resolve the orientation indetermination problem of a receiving coil. Experiments show that a dc power level up to 170 mW, with an efficiency of 1.3%, could be steadily received when the receiving coil was placed at the center of the transmitting coil, which can meet the requirement for electric power of some microsystems.
---
paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
---
paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: A Two-Hop Wireless Power Transfer System With an Efficiency-Enhanced Power Receiver for Motion-Free Capsule Endoscopy Inspection

paper_content:

This paper presents a wireless power transfer system for a motion-free capsule endoscopy inspection. Conventionally, a wireless power transmitter in a specifically designed jacket has to be connected to a strong power source with a long cable. To avoid the power cable and allow patients to walk freely in a room, this paper proposes a two-hop wireless power transfer system. First, power is transferred from a floor to a power relay in the patient's jacket via strong coupling. Next, power is delivered from the power relay to the capsule via loose coupling. Besides making patients much more conformable, the proposed techniques eliminate the sources of reliability issues arisen from the moving cable and connectors. In the capsule, it is critical to enhance the power conversion efficiency. This paper develops a switch-mode rectifier (rectifying efficiency of 93.6%) and a power combination circuit (enhances combining efficiency by 18%). Thanks to the two-hop transfer mechanism and the novel circuit techniques, this system is able to transfer an average power of 24 mW and a peak power of 90 mW from the floor to a 13 mm × 27 mm capsule over a distance of 1 m with the maximum dc-to-dc power efficiency of 3.04%.
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paper_title: Energy Transmission Transformer for a Wireless Capsule Endoscope: Analysis of Specific Absorption Rate and Current Density in Biological Tissue

paper_content:

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.
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paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: THE USE OF A HUMAN BODY MODEL TO DETERMINE THE VARIATION OF PATH LOSSES IN THE HUMAN BODY CHANNEL IN WIRELESS CAPSULE ENDOSCOPY

paper_content:

Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a high- speed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at difierent frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difierence between the maximum and minimum path loss at difierent anatomical regions, which is the most important information in the link-margin setup for highly e-cient telemetry systems in next-generation capsules. In order
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paper_title: A wireless power transmission system for an active capsule endoscope for colon inspection

paper_content:

Multipurpose active capsule endoscopes (ACE) have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. In order to deliver stable and sufficient energy safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a double-layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 500 mW usable power can be transmitted under the worst geometrical conditions and the safety restraints in a volume of Φ13 × 13 mm. The wireless power transmission system is integrated to an ACE and applied in animal experiments. The designed wireless power transmission is proved to be feasible and potentially safe in a future application.
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paper_title: An inductive power link for a wireless endoscope

paper_content:

Abstract An inductive link is presented that can handle freedom of motion. The envisaged application is to power a wireless camera capsule used for non-invasive visual inspection of the small bowel. Up to 150 mW of usable dc power can be delivered to the capsule for the entire duration of its travel along the gastric track. The outer dimensions of the power receiver compartment inside the capsule are O 10 mm × 13 mm. The power efficiency of the link is measured to be 1% under worst-case geometrical conditions. The issue of patient's health and safety regarding exposure to the electromagnetic field is addressed. To this purpose, an experimental method is applied to predict specific absorption rates. Conversely, the effect of biological tissue on link performance and practical workability is evaluated as well. Electric shielding of the transmitter coil is applied to reduce biological tissue interaction. In this way, appliance on a living subject is made both safe and practically feasible.
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paper_title: A wireless energy link for endoscopy with end-fire helix emitter and Load-Adaptive power converter

paper_content:

This paper proposes a new Wireless-Powered Micro-Ball Endoscopy system, in which wireless power is emitted from an emitter array embedded in a floor and resonantly relayed by a passive wireless power jacket on patients. Comparing to other wireless powering endoscopy systems, both the patients' freedom of movement and the power efficiency are improved. To enhance the power efficiency, an End-Fire Helix Emitter is proposed, which is a fundamentally novel structure used for generating near field alternative magnetic field with high efficiency. This paper also proposes a Load-Adaptive power converter circuit to keep optimal power efficiency by matching the varied load impedance. A prototyping design is fabricated. At the frequency of 24.05MHz, the power efficiency of transmission from floor to wireless jacket is 44.6%, and the overall energy efficiency from floor to Endoscopic Micro-Ball is 2.5% at best.
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paper_title: The optimization of wireless power transmission: design and realization.

paper_content:

BACKGROUND ::: A wireless power transmission system is regarded as a practical way of solving power-shortage problems in multifunctional active capsule endoscopes. ::: ::: ::: METHODS ::: The uniformity of magnetic flux density, frequency stability and orientation stability are used to evaluate power transmission stability, taking into consideration size and safety constraints. Magnetic field safety and temperature rise are also considered. Test benches are designed to measure the relevent parameters. Finally, a mathematical programming model in which these constraints are considered is proposed to improve transmission efficiency. To verify the feasibility of the proposed method, various systems for a wireless active capsule endoscope are designed and evaluated. ::: ::: ::: RESULTS ::: The optimal power transmission system has the capability to supply continuously at least 500 mW of power with a transmission efficiency of 4.08%. ::: ::: ::: CONCLUSIONS ::: The example validates the feasibility of the proposed method. Introduction of novel designs enables further improvement of this method.
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paper_title: An efficiency-enhanced wireless power transfer system with segmented transmitting coils for endoscopic capsule

paper_content:

This paper proposes a new wireless power transfer (WPT) system for the endoscopic capsule. In the system, a group of vertically segmented primary coils around the human body are adopted as the transmitting coils. According to the position of the endoscopic capsule, one of the transmitting coils is intelligently selected to transfer the power with the highest efficiency. This paper also presents a coil selection and control algorithm for the unique WPT system. Compared with the conventional design, the calculated transmission efficiencies of the new solution at the best and worst points of the body are enhanced by 53.5% and 138% respectively. And the average efficiency of the proposed solution is about 3.8%.
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paper_title: Power transmission for gastrointestinal microsystems using inductive coupling.

paper_content:

Much research on the development of a robotic capsule and microrobot for the diagnosis of gastrointestinal diseases has been carried out. The powering of these microsystems is becoming very important as the implementation of such systems is becoming more feasible by advances in relevant technologies. A wireless power transmission system employing two coils, based on inductive coupling, is discussed in this note. The coupling coefficient between the two coils was measured on axial, lateral and pitch misalignment. The power transmission efficiency was deduced and optimized by selecting proper tuning capacitors and transmission frequency. A serial resonant circuit (SRC) on a receiving side is more adaptive by comparison with parallel resonant circuit (PRC) topology. A multi-receiving coil structure was proposed and examined in an attempt to resolve the orientation indetermination problem of a receiving coil. Experiments show that a dc power level up to 170 mW, with an efficiency of 1.3%, could be steadily received when the receiving coil was placed at the center of the transmitting coil, which can meet the requirement for electric power of some microsystems.
---
paper_title: A Two-Hop Wireless Power Transfer System With an Efficiency-Enhanced Power Receiver for Motion-Free Capsule Endoscopy Inspection

paper_content:

This paper presents a wireless power transfer system for a motion-free capsule endoscopy inspection. Conventionally, a wireless power transmitter in a specifically designed jacket has to be connected to a strong power source with a long cable. To avoid the power cable and allow patients to walk freely in a room, this paper proposes a two-hop wireless power transfer system. First, power is transferred from a floor to a power relay in the patient's jacket via strong coupling. Next, power is delivered from the power relay to the capsule via loose coupling. Besides making patients much more conformable, the proposed techniques eliminate the sources of reliability issues arisen from the moving cable and connectors. In the capsule, it is critical to enhance the power conversion efficiency. This paper develops a switch-mode rectifier (rectifying efficiency of 93.6%) and a power combination circuit (enhances combining efficiency by 18%). Thanks to the two-hop transfer mechanism and the novel circuit techniques, this system is able to transfer an average power of 24 mW and a peak power of 90 mW from the floor to a 13 mm × 27 mm capsule over a distance of 1 m with the maximum dc-to-dc power efficiency of 3.04%.
---
paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

paper_content:

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
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paper_title: An active endoscopic robot based on wireless power transmission and electromagnetic localization

paper_content:

Background ::: ::: Conventional endoscopes have the disadvantages of causing pain to patients because of their large dimensions and allowing incomplete inspection because of their limited power. ::: ::: ::: ::: Methods ::: ::: An active inchworm-like endoscopic robot has been designed, which is based on electromagnetic localization and synthesis of magnetic field strength vectors. ::: ::: ::: ::: Results ::: ::: The efficiency of wireless power transmission can be kept above 0.9% when the power-receiving coil is at arbitrary position and orientation. The position error of localization is < 10 mm and the average error of orientation angle is 2° . When the robot moves through part of the porcine colon, images are transmitted outwards continuously at a speed of 30 fps and the temperature rise of the colon is < 1 °C. By simulation, the electromagnetic exposures to the human body are lower than international standards. ::: ::: ::: ::: Conclusions ::: ::: The endoscopic robot is a promising tool for use by doctors, although further experiments and improvements need to be done. Copyright © 2008 John Wiley & Sons, Ltd.
---
paper_title: Three-dimensional power receiver for in vivo robotic capsules

paper_content:

A three-dimensional wireless power receiver is introduced in this study for in vivo robotic capsules. It is designed to retrieve hundreds of milliwatts of power, regardless of orientation relative to the time-varying magnetic field generated by the external transmitter outside a test animal body. Design issues, such as antenna structure and rectification topology, are discussed, considering limitations of physical space. Various design parameters are implemented and experimented. A selected design is implemented and tested for power variations on rotational positions relative to the transmitter magnetic field. The presented receiver delivers more than 300 mW of power regardless of its orientation. A test capsule is assembled with LED load for in vivo experiments. Visual verification of the light intensity of LED shows that the power-receiving performance of the receiver is not affected inside the animal body.
---
paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
---
paper_title: A wireless power supply system for robotic capsular endoscopes

paper_content:

Abstract In expanding capsular endoscopy from a mere passive screening tool to a multipurpose robot, batteries become inadequate. Wireless power supply overcomes the problem of power shortage and enables the integration of high-power modules. This work focuses on wireless inductive power transfer and its technology optimization in size, materials and efficiency. A user friendly and stable external unit has been developed that supports power and data transmission through the downlink (from the external world to the capsule). The possibility of using a Helmholtz coil at the primary side has been investigated and a preliminary set-up has been implemented. The ongoing development on 3D coil geometries is further refined by the introduction of a laser machined ferrite core to boost the amount of available power. It is demonstrated that 330 mW can be transferred to a capsule under all possible orientations, within a 0.48 cm 3 volume.
---
paper_title: 1 A Multi-Coil Inductive Powering System for an Endoscopic Capsule with Vibratory Actuation

paper_content:

Abstract The transformation of endoscopic capsules from passive tools to robotic devices is increasingly attracting the interest of the research community. In the past few years, significant progress has been achieved in the areas of microelectronics and electromechanical systems. However, their use in commercial endoscopic capsules is hindered by their increased power demands, which, to present, cannot be adequately met by embedded power sources. A 3D inductive powering module, providing over 300 mW to the capsule, overcomes these limitations, thus enabling the integration of active locomotion systems, as well as advanced diagnostic and therapeutic features. This is demonstrated in the present study by a capsule prototype employing the wireless powering unit to drive an onboard vibratory motor for capsule propulsion. Simplified models are employed to illustrate the main principle of this vibratory locomotion scheme. Experimental results, involving movement of the prototype in various environments, confirm both the effectiveness of the wireless powering system, and the efficacy of the vibratory locomotion scheme.
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paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

paper_content:

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
---
paper_title: An active endoscopic robot based on wireless power transmission and electromagnetic localization

paper_content:

Background ::: ::: Conventional endoscopes have the disadvantages of causing pain to patients because of their large dimensions and allowing incomplete inspection because of their limited power. ::: ::: ::: ::: Methods ::: ::: An active inchworm-like endoscopic robot has been designed, which is based on electromagnetic localization and synthesis of magnetic field strength vectors. ::: ::: ::: ::: Results ::: ::: The efficiency of wireless power transmission can be kept above 0.9% when the power-receiving coil is at arbitrary position and orientation. The position error of localization is < 10 mm and the average error of orientation angle is 2° . When the robot moves through part of the porcine colon, images are transmitted outwards continuously at a speed of 30 fps and the temperature rise of the colon is < 1 °C. By simulation, the electromagnetic exposures to the human body are lower than international standards. ::: ::: ::: ::: Conclusions ::: ::: The endoscopic robot is a promising tool for use by doctors, although further experiments and improvements need to be done. Copyright © 2008 John Wiley & Sons, Ltd.
---
paper_title: An inductive power link for a wireless endoscope

paper_content:

Abstract An inductive link is presented that can handle freedom of motion. The envisaged application is to power a wireless camera capsule used for non-invasive visual inspection of the small bowel. Up to 150 mW of usable dc power can be delivered to the capsule for the entire duration of its travel along the gastric track. The outer dimensions of the power receiver compartment inside the capsule are O 10 mm × 13 mm. The power efficiency of the link is measured to be 1% under worst-case geometrical conditions. The issue of patient's health and safety regarding exposure to the electromagnetic field is addressed. To this purpose, an experimental method is applied to predict specific absorption rates. Conversely, the effect of biological tissue on link performance and practical workability is evaluated as well. Electric shielding of the transmitter coil is applied to reduce biological tissue interaction. In this way, appliance on a living subject is made both safe and practically feasible.
---
paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
---
paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

paper_content:

Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
---
paper_title: Power transmission for gastrointestinal microsystems using inductive coupling.

paper_content:

Much research on the development of a robotic capsule and microrobot for the diagnosis of gastrointestinal diseases has been carried out. The powering of these microsystems is becoming very important as the implementation of such systems is becoming more feasible by advances in relevant technologies. A wireless power transmission system employing two coils, based on inductive coupling, is discussed in this note. The coupling coefficient between the two coils was measured on axial, lateral and pitch misalignment. The power transmission efficiency was deduced and optimized by selecting proper tuning capacitors and transmission frequency. A serial resonant circuit (SRC) on a receiving side is more adaptive by comparison with parallel resonant circuit (PRC) topology. A multi-receiving coil structure was proposed and examined in an attempt to resolve the orientation indetermination problem of a receiving coil. Experiments show that a dc power level up to 170 mW, with an efficiency of 1.3%, could be steadily received when the receiving coil was placed at the center of the transmitting coil, which can meet the requirement for electric power of some microsystems.
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paper_title: Wireless power and data transmission strategies for next-generation capsule endoscopes

paper_content:

Capsular endoscopy is becoming increasingly popular as an alternative to traditional gastro-intestinal (GI) examination techniques. However, the breakthrough of these devices is hindered by the limited amount of power that can be stored in a tiny pill. Most commercial devices use two watch batteries that can only provide an average power of 25 mW for about 6 h, certainly not sufficient for advanced robotic features. A dedicated inductive powering system, operating at 1 MHz to limit the human body absorption, has been developed which was proven to support the transfer of over 300 mW. The system relies on a condensed set of orthogonal ferrite coils, embedded in the capsule, and an external unit based on a Helmholtz coil driven by a class E amplifier. Control data can be sent through the inductive link by modulating the power carrier, whereas a dedicated high data rate RF link is used to transfer the images from the capsule to the base station. Besides evaluating the compatibility with radio transmission, several demonstrators were assembled combining the wireless powering system with various locomotion strategies and LED illumination. This paper describes the design and implementation of the inductive powering system, its combination with data transmission techniques and the testing activity with other capsule-dedicated modules.
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paper_title: An active endoscopic robot based on wireless power transmission and electromagnetic localization

paper_content:

Background ::: ::: Conventional endoscopes have the disadvantages of causing pain to patients because of their large dimensions and allowing incomplete inspection because of their limited power. ::: ::: ::: ::: Methods ::: ::: An active inchworm-like endoscopic robot has been designed, which is based on electromagnetic localization and synthesis of magnetic field strength vectors. ::: ::: ::: ::: Results ::: ::: The efficiency of wireless power transmission can be kept above 0.9% when the power-receiving coil is at arbitrary position and orientation. The position error of localization is < 10 mm and the average error of orientation angle is 2° . When the robot moves through part of the porcine colon, images are transmitted outwards continuously at a speed of 30 fps and the temperature rise of the colon is < 1 °C. By simulation, the electromagnetic exposures to the human body are lower than international standards. ::: ::: ::: ::: Conclusions ::: ::: The endoscopic robot is a promising tool for use by doctors, although further experiments and improvements need to be done. Copyright © 2008 John Wiley & Sons, Ltd.
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paper_title: Energy Transmission Transformer for a Wireless Capsule Endoscope: Analysis of Specific Absorption Rate and Current Density in Biological Tissue

paper_content:

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.
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paper_title: An inductive power link for a wireless endoscope

paper_content:

Abstract An inductive link is presented that can handle freedom of motion. The envisaged application is to power a wireless camera capsule used for non-invasive visual inspection of the small bowel. Up to 150 mW of usable dc power can be delivered to the capsule for the entire duration of its travel along the gastric track. The outer dimensions of the power receiver compartment inside the capsule are O 10 mm × 13 mm. The power efficiency of the link is measured to be 1% under worst-case geometrical conditions. The issue of patient's health and safety regarding exposure to the electromagnetic field is addressed. To this purpose, an experimental method is applied to predict specific absorption rates. Conversely, the effect of biological tissue on link performance and practical workability is evaluated as well. Electric shielding of the transmitter coil is applied to reduce biological tissue interaction. In this way, appliance on a living subject is made both safe and practically feasible.
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paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

paper_content:

Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
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paper_title: The optimization of wireless power transmission: design and realization.

paper_content:

BACKGROUND ::: A wireless power transmission system is regarded as a practical way of solving power-shortage problems in multifunctional active capsule endoscopes. ::: ::: ::: METHODS ::: The uniformity of magnetic flux density, frequency stability and orientation stability are used to evaluate power transmission stability, taking into consideration size and safety constraints. Magnetic field safety and temperature rise are also considered. Test benches are designed to measure the relevent parameters. Finally, a mathematical programming model in which these constraints are considered is proposed to improve transmission efficiency. To verify the feasibility of the proposed method, various systems for a wireless active capsule endoscope are designed and evaluated. ::: ::: ::: RESULTS ::: The optimal power transmission system has the capability to supply continuously at least 500 mW of power with a transmission efficiency of 4.08%. ::: ::: ::: CONCLUSIONS ::: The example validates the feasibility of the proposed method. Introduction of novel designs enables further improvement of this method.
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paper_title: Design and Development of Low-Loss Transformer for Powering Small Implantable Medical Devices

paper_content:

Small implantable medical devices, such as wireless capsule endoscopes, that can be swallowed have previously been developed. However, these devices cannot continuously operate for more than 8 h because of battery limitations; moreover, additional functionalities cannot be introduced. This paper proposes a design method for a high-efficiency energy transmission transformer (ETT) that can transmit energy transcutaneously to small implantable medical devices using electromagnetic induction. First, the authors propose an unconventional design method to develop such a high-efficiency ETT. This method can be readily used to calculate the exact transmission efficiency for changes in the material and design parameters (i.e., the magnetic material, transmission frequency, load resistance, etc.). Next, the ac-to-ac energy transmission efficiency is calculated and compared with experimental measurements. Then, suitable conditions for practical transmission are identified. A maximum efficiency of 33.1% can be obtained at a transmission frequency of 500 kHz and a receiving power of 100 mW for a receiving coil size of ?5 mm × 20 mm. Future design optimization is possible by using this method.
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paper_title: A 3D Ferrite Coil Receiver for Wireless Power Supply of Endoscopic Capsules

paper_content:

Abstract To expand capsular endoscopy from a mere passive screening tool towards a multipurpose robot, batteries become inadequate. Wireless power supply overcomes the problem of power shortage allowing the integration of high power demanding modules. This work focuses on wireless inductive power transfer and its optimization in size and materials. The ongoing development on 3D coil geometries is further refined by the introduction of a laser machined ferrite core to boost the amount of available power. It is demonstrated that 330mW can be transferred to a capsule under all possible orientations, within a 0.63cm3 volume.
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paper_title: 1 A Multi-Coil Inductive Powering System for an Endoscopic Capsule with Vibratory Actuation

paper_content:

Abstract The transformation of endoscopic capsules from passive tools to robotic devices is increasingly attracting the interest of the research community. In the past few years, significant progress has been achieved in the areas of microelectronics and electromechanical systems. However, their use in commercial endoscopic capsules is hindered by their increased power demands, which, to present, cannot be adequately met by embedded power sources. A 3D inductive powering module, providing over 300 mW to the capsule, overcomes these limitations, thus enabling the integration of active locomotion systems, as well as advanced diagnostic and therapeutic features. This is demonstrated in the present study by a capsule prototype employing the wireless powering unit to drive an onboard vibratory motor for capsule propulsion. Simplified models are employed to illustrate the main principle of this vibratory locomotion scheme. Experimental results, involving movement of the prototype in various environments, confirm both the effectiveness of the wireless powering system, and the efficacy of the vibratory locomotion scheme.
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paper_title: A video wireless capsule endoscopy system powered wirelessly: design, analysis and experiment

paper_content:

Wireless capsule endoscopy (WCE), as a relatively new technology, has brought about a revolution in the diagnosis of gastrointestinal (GI) tract diseases. However, the existing WCE systems are not widely applied in clinic because of the low frame rate and low image resolution. A video WCE system based on a wireless power supply is developed in this paper. This WCE system consists of a video capsule endoscope (CE), a wireless power transmission device, a receiving box and an image processing station. Powered wirelessly, the video CE has the abilities of imaging the GI tract and transmitting the images wirelessly at a frame rate of 30 frames per second (f/s). A mathematical prototype was built to analyze the power transmission system, and some experiments were performed to test the capability of energy transferring. The results showed that the wireless electric power supply system had the ability to transfer more than 136 mW power, which was enough for the working of a video CE. In in vitro experiments, the video CE produced clear images of the small intestine of a pig with the resolution of 320 × 240, and transmitted NTSC format video outside the body. Because of the wireless power supply, the video WCE system with high frame rate and high resolution becomes feasible, and provides a novel solution for the diagnosis of the GI tract in clinic.
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paper_title: Energy Transmission Transformer for a Wireless Capsule Endoscope: Analysis of Specific Absorption Rate and Current Density in Biological Tissue

paper_content:

This paper reports on the electromagnetic influences on the analysis of biological tissue surrounding a prototype energy transmission system for a wireless capsule endoscope. Specific absorption rate (SAR) and current density were analyzed by electromagnetic simulator in a model consisting of primary coil and a human trunk including the skin, fat, muscle, small intestine, backbone, and blood. First, electric and magnetic strength in the same conditions as the analytical model were measured and compared to the analytical values to confirm the validity of the analysis. Then, SAR and current density as a function of frequency and output power were analyzed. The validity of the analysis was confirmed by comparing the analytical values with the measured ones. The SAR was below the basic restrictions of the International Commission on Nonionizing Radiation Protection (ICNIRP). At the same time, the results for current density show that the influence on biological tissue was lowest in the 300-400 kHz range, indicating that it was possible to transmit energy safely up to 160 mW. In addition, we confirmed that the current density has decreased by reducing the primary coil's current.
---
paper_title: An inductive power link for a wireless endoscope

paper_content:

Abstract An inductive link is presented that can handle freedom of motion. The envisaged application is to power a wireless camera capsule used for non-invasive visual inspection of the small bowel. Up to 150 mW of usable dc power can be delivered to the capsule for the entire duration of its travel along the gastric track. The outer dimensions of the power receiver compartment inside the capsule are O 10 mm × 13 mm. The power efficiency of the link is measured to be 1% under worst-case geometrical conditions. The issue of patient's health and safety regarding exposure to the electromagnetic field is addressed. To this purpose, an experimental method is applied to predict specific absorption rates. Conversely, the effect of biological tissue on link performance and practical workability is evaluated as well. Electric shielding of the transmitter coil is applied to reduce biological tissue interaction. In this way, appliance on a living subject is made both safe and practically feasible.
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paper_title: A Wideband Spiral Antenna for Ingestible Capsule Endoscope Systems: Experimental Results in a Human Phantom and a Pig

paper_content:

This paper presents the design of a wideband spiral antenna for ingestible capsule endoscope systems and a comparison between the experimental results in a human phantom and a pig under general anesthesia. As wireless capsule endoscope systems transmit real-time internal biological image data at a high resolution to external receivers and because they operate in the human body, a small wideband antenna is required. To incorporate these properties, a thick-arm spiral structure is applied to the designed antenna. To make practical and efficient use of antennas inside the human body, which is composed of a high dielectric and lossy material, the resonance characteristics and radiation patterns were evaluated through a measurement setup using a liquid human phantom. The total height of the designed antenna is 5 mm and the diameter is 10 mm. The fractional bandwidth of the fabricated antenna is about 21% with a voltage standing-wave ratio of less than 2, and it has an isotropic radiation pattern. These characteristics are suitable for wideband capsule endoscope systems. Moreover, the received power level was measured using the proposed antenna, a circular polarized receiver antenna, and a pig under general anesthesia. Finally, endoscopic capsule images in the stomach and large intestine were captured using an on-off keying transceiver system.
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paper_title: Study of a wireless power transmission system for an active capsule endoscope

paper_content:

Background ::: ::: An active capsule endoscope (ACE) will consume much more energy than can be power by batteries. Its orientation and position are always undetermined when it continues the natural way down the gastrointestinal track. ::: ::: ::: ::: Methods ::: ::: In order to deliver stable and sufficient energy to ACE safely, a wireless power transmission system based on inductive coupling is presented. The system consists of a Helmholtz primary coil outside and a multiple secondary coils inside the body. The Helmholtz primary coil is driven to generate a uniform alternating magnetic field covering the whole of the alimentary tract, and the multiple secondary coils receive energy regardless of the ACE's position and orientation relative to the generated magnetic field. The human tissue safety of the electromagnetic field generated by transmitting coil was evaluated, based on a high-resolution realistic human model. ::: ::: ::: ::: Results ::: ::: At least 310 mW usable power can be transmitted under the worst geometrical conditions. Outer dimensions of the power receiver, 10 mm diameter × 12 mm; transmitting power, 25 W; resonant frequency, 400 kHz. The maximum specific absorption rate (SAR) and current density of human tissues are 0.329 W/kg and 3.82 A/m2, respectively, under the basic restrictions of the International Commission on Non-ionizing Radiation Protection (ICNIRP). ::: ::: ::: ::: Conclusions ::: ::: The designed wireless power transmission is shown to be feasible and potentially safe in a future application. Copyright © 2010 John Wiley & Sons, Ltd.
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paper_title: Efficiency optimization of wireless power transmission systems for active capsule endoscopes

paper_content:

Multipurpose active capsule endoscopes have drawn considerable attention in recent years, but these devices continue to suffer from energy limitations. A wireless power supply system is regarded as a practical way to overcome the power shortage problem in such devices. This paper focuses on the efficiency optimization of a wireless energy supply system with size and safety constraints. A mathematical programming model in which these constraints are considered is proposed for transmission efficiency, optimal frequency and current, and overall system effectiveness. To verify the feasibility of the proposed method, we use a wireless active capsule endoscope as an illustrative example. The achieved efficiency can be regarded as an index for evaluating the system, and the proposed approach can be used to direct the design of transmitting and receiving coils.
---
paper_title: Development of a micro-robot for endoscopes based on wireless power transfer.

paper_content:

This paper develops a new prototype of a wireless micro-robot system for endoscopes. The micro-robot we have fabricated and tested is able to propel itself in the intestine of pig. Its autonomous manner is earthworm-like and driven by linear actuators based on a DC motor. Unlike with conventional micro-robot endoscopes, that wireless module is used for communicating and power transfer. The experimental results show that the driving force of the linear actuator can reach up to 2.55 N and the stable supplying power is up to 480 mW DC power for the receiving coil in the proposed system, which all fulfill the need of the micro-robot system. The micro-robot can creep reliably in the small and large intestine of a pig. The video communication module embedded in the head of the micro-robot can capture the inner picture of the intestine and broadcast it to PC in real-time.
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paper_title: Portable Wireless Power Transmission System of a Video Capsule Endoscopy: Design and Realization

paper_content:

Video capsule endoscopy, as a new technology, has brought a revolution in the diagnosis of gastrointestinal tract diseases. However, power limitation has become a great problem that restricts its development and application. Meanwhile, the diagnostic procedure usually lasts more than ten hours or more. So, a portable wireless power transmission system based on inductive coupling is designed for the video capsule endoscopy. The system consists of a double layer solenoid pair primary coil outside and a multiple secondary coils inside the body. At least 150 mW usable power can be transmitted under the worst geometrical conditions, which totally meet requirements of the video capsule endoscopy. On the other hand, the weight of the wireless power transmission system is only 4.98kg, which realized the portability.
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paper_title: Analysis of SAR and Current Density in Human Tissue Surrounding an Energy Transmitting Coil for a Wireless Capsule Endoscope

paper_content:

This paper reports on a prototype energy transmission system for a wireless capsule endoscope and the electromagnetic effects that influence its use in biological tissues. Specific absorption rate (SAR) and current density were analyzed by an electromagnetic simulator in a model consisting of a primary coil and a human trunk that included eighteen different organs. SAR and current density as a function of frequency were analyzed. The SAR was maximized at muscle and fat, and was below the basic restrictions of the International Commission on Non Ionizing Radiation Protection (ICNIRP). At the same time, the results for current density were maximized at muscle and intestine, and were below the ICNIRP basic restrictions, indicating that it was possible to safely transmit energy up to 30 mW at the frequency of 300-600 kHz.
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paper_title: Outer-Wall Loop Antenna for Ultrawideband Capsule Endoscope System

paper_content:

The capsule endoscopy system has been used to obtain an image from the inside of the human digestive tract. To acquire high-resolution images, a loop antenna with ultrawide bandwidth is proposed. It is part of the outer wall of the capsule, thus decreasing volume and increasing performance, and uses a meandered line for resonance in an electrically small area. The proposed antenna makes maximal use of the capsule's outer surface, enabling the antenna to be larger than inner antennas. The measured result shows that the gain of the proposed antenna is higher than that of inner antennas. Return loss and radiation pattern are investigated through simulation and measurement, showing that the proposed antenna has an ultrawide bandwidth of 260 MHz (from 370 to 630 MHz) for VSWR <; 2 and an omnidirectional radiation pattern. Using identical antenna pairs in the equivalent body phantom fluid, antenna efficiency is measured to 43.7% (-3.6 dB).
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Title: Application of Wireless Power Transmission Systems in Wireless Capsule Endoscopy: An Overview

Section 1: Introduction
Description 1: This section introduces the background, significance of wireless capsule endoscopes (WCEs), and the challenges associated with their power requirements.

Section 2: Power Requirement for Future WCE
Description 2: This section discusses the increasing power demands of future WCEs due to enhanced features like high-resolution imaging, advanced electronics, and multifunctional capabilities.

Section 3: WPT System for WCE
Description 3: This section provides an overview of Wireless Power Transmission (WPT) systems, focusing on inductive and radiative coupling techniques suitable for WCE applications.

Section 4: Inductive Power Transmitter
Description 4: This section details the components and design considerations of the inductive power transmitter, including the power amplifier and transmitting coil.

Section 5: Inductive Power Receiver
Description 5: This section describes the power receiver coil (RC), rectifier, and regulator circuit, and examines factors affecting the received power.

Section 6: Safety Limitations for Biological Tissues
Description 6: This section addresses the safety concerns of WPT systems, focusing on specific absorption rate (SAR) and current density in human tissues.

Section 7: Existing WPT System Performance
Description 7: This section reviews the performance of existing solenoid coil-based and Helmholtz coil-based WPT systems, discussing their efficiency and design optimizations.

Section 8: Stability of WPT Systems
Description 8: This section evaluates the stability of WPT systems in terms of alignment-related issues between the transmitting and receiving coils.

Section 9: Safety Verification of WPT Systems
Description 9: This section analyzes various studies on SAR and current density to ensure patient safety during the operation of WPT systems.

Section 10: Discussion
Description 10: This section consolidates the findings, highlighting the gaps in current research, challenges in achieving stable power transfer, and the need for further studies on WPT systems in practical environments.

Section 11: Concluding Remarks
Description 11: This section summarizes the critical issues in the current WPT systems for WCE, emphasizing the necessity for further research to enhance system feasibility and safety.