Yawen Chan

Wireless robotic capsule endoscopy: state-of-the-art and challenges

This paper surveys the state-of-the-art in wireless capsule endoscopy in terms of commercially available products and prototypes currently under development in research labs worldwide. Challenges facing us in designing and manufacturing active wireless capsule endoscopes are outlined, together with potential methods to tackle them.

Effects of Dielectric Parameters of Human Body on Radiation Characteristics of Ingestible Wireless Device at Operating Frequency of 430 MHz

In order to assess the sensitivities of the radiation characteristics and the compliance of ingestible wireless device (IWD) in human body due to the uncertainty and intersubject variability of dielectric properties of human body tissues, the specific absorption rate (SAR) and radiation characteristics of the IWD in two realistic human body models with changed and unchanged dielectric values are quantitatively compared using the finite-difference time-domain method. Simulations are carried out in 13 scenarios where the IWD is placed in the center positions of abdomens in the two body models at the operating frequency of 430 MHz with three orientations. Results show that the variation of radiation intensity near the surface of abdomen is around 2.5 dB within 20% variation of dielectric values. The maximum SAR values increase with the increase in conductivities of human body tissues and decrease with the increase in relative permittivities of human body tissues. A variation of up to 20% in conductivities and relative permittivities, alone or simultaneously, always causes a variation of SAR to be less than 10%. As far as the compliance of safety is concerned, the maxima of 1-g-averaged and 10-g-averaged SARs can reach 3.16 and 0.89 W/kg at the input power of 25 mW.

Experimental Study of Radiation Efficiency from an Ingested Source inside a Human Body Model

The attenuation of human body trunk at frequency range of 100 MHz to 6 GHz from an internal source was estimated using a simplified experimental model. Antennas were placed in the model which was filled with distilled water, 0.9% NaCl saline solution, and porcine body tissue alternately to determine the attenuation of the system. Saline has greater attenuation than water due to its higher conductivity, while porcine body tissue has attenuation bounded by saline solution and water. Estimated attenuation at the four ISM bands, 434 MHz, 915 MHz, 2.45 GHz and 5.8 GHz were given and all of these bands satisfied the safety and sensitivity requirements of a biomedical telemetry system. 915MHz and 2.45GHz are good choices for the wireless link because of their relatively larger electrical size of RF components such as antenna. In addition, with the growth in wireless LAN and Bluetooth technology, miniaturized antennas, camera modules, and other RF devices have been developed which can be employed in biomedical ingested or implanted devices. This paper gives a reference of attenuation values of a human body trunk of average size. It should be noted that the attenuation values can be different for different body size and different body composition, and therefore the values in this paper serves as a reference only

A low-cost tracking method based on magnetic marker for capsule endoscope

In this paper, a position tracking method based on a magnetic marker and hall sensors array, which could be used in capsule endoscope localization, is introduced. The experiment setup is shown, together with the minimization algorithm to analyze the data. It was demonstrated that the calculated position errors could be around 2mm when the marker is moving with a velocity of 2mm/s. Compared with other tracking system, this system cost much lower.

A prototype design of wireless capsule endoscope

Diseases of the gastrointestinal (GI) tract, such as intestinal bleeding and ulcer, are very common. In order to determine the location of the disease, as well as to diagnose the problem, endoscopy test is performed. A wireless capsule endoscope is a pill-sized device for the patient to swallow. It equips with a camera and a wireless transmitter so that as it travels through the patients GI tract, it take pictures or video of the tract and transmit the information out of the patient body wirelessly. This paper discusses the possible solutions and challenges of the wireless capsule endoscope, in terms of the choice of wireless frequency and circuit components. A prototype is built with commercially available components to demonstrate the concept of the device.

Physiological Factors of the Small Intestine in Design of Active Capsule Endoscopy

Wireless capsule endoscope is a device used to examine the diseases in the small intestine. At present, the capsule endoscope moves through the gastrointestinal tract by natural propulsion of peristalsis. In order to achieve real-time diagnosis and treatment-related procedure, the capsule endoscope is required to be self-actuated and controlled. Different from solid environment, the small intestine is an extremely flexible tube. The unique structure and tissue cause many challenges for the capsule actuation. In this paper, the features, motility, and frictional force of the small intestine are analyzed for determining the design strategy. In-vitro experiment results show the power of magnetic force needed for driving the capsule and the factors that affect the magnitude of the driving force as well. Based on the analysis of the small intestine, a scheme of magnetically-actuated active endoscopy is proposed in the end

Radiation characteristics of ingested wireless device at frequencies from 430 MHz to 3 GHz

In order to assess the compliance of high frequency ingested wireless devices (IWD) within the safety guidelines worldwide, the biological effects and the radiation efficiency of the IWD in a realistic human body model were studied using the Finite-Difference Time-Domain (FDTD) method. Simulations were carried out for three orientations of the IWD at seven positions in the human body model. Specific Absorption Rate (SAR), temperature rise, near field and far field characteristics were analyzed at frequencies from 430 MHz to 3 GHz. Results showed that the radiation intensity outside the body decreased with frequency. Furthermore, the orientation and position of the IWD, which gave maximum radiation efficiency, was frequency dependent. In our experiment, when the IWD was located at the front-most and back-most positions of the small intestine, the electric intensity outside the human body was maximum and minimum, respectively. The position influences the radiation efficiency of the IWD more than its orientation.

System architecture of a body area network and its web service based data publishing

Wireless Sensor Networks (WSN) is a research hotspot in recent years and has yielded many fruitful results. However, the biomedical applications of WSN haven’t received significant development due to its many unique challenges for the engineers and physicians. In this paper, a system architecture solution of body area network (BAN), our so called project “MediMesh”, is presented. A biomedical dedicated BAN node hardware platform is devised to fit the medical monitoring application. The sensor node is built up especially for healthcare monitoring while the biocompatibility and portability are considered. A light weight network protocol is designed considering the radiation effect and communication overhead. After data acquisition from sink stations, a data publishing system based on web service technology is implemented for typical hospital environment. The publishing of biomedical data is realized through 3 phases: first storing the data automatically in a database, then creating information sharing service by using Web Service technology, and finally allowing data access by the physicians and end users.

Influence of animal body on ingested wireless device before and after death

This paper measured the radiation characteristics of antennas inside the ingestible wireless devices (IWDs). Three monopole antennas were designed and put in two positions of the intestine of an adult female pig at the weight of 80 kg. The return losses of the antennas were measured when the pig was anesthetic and after euthanasia within one hour. The results demonstrate that the frequencies drift greatly from 2.78, 2.17, and 4.29 GHz at the free space into 1.42, 1.0, and 2.2 GHz when the antennas are put in the top position of the intestine of the anesthetic pig and the frequency will increase to 1.62, 1.15, and 2.85 GHz after the pigpsilas euthanasia within one hour. The frequencies increase from 1.5, 1.03, and 2.3 GHz to 1.67, 1.13, and 2.8 GHz when the antennas are put in the bottom position of the intestine of the pig after its euthanasia within one hour. The dead body of the pig absorbed less radiation energy than the living body. Our measurement results further validate the decrease of the dielectric properties of the animal tissues after death. These differences need to be taken into account in electromagnetic modeling for simulation, and should be taken into account before the design of ingested antennas.