Wireless Capsule Endoscopy System Research Articles

Design of a Compact Circularly Polarized Implantable Antenna for Capsule Endoscopy Systems.

This research proposes a miniature circular polarization antenna used in a wireless capsule endoscopy system at 2.45 GHz for industrial, scientific, and medical bands. We propose a method of cutting a chamfer rectangular slot on a circular radiation patch and introducing a curved radiation structure into the centerline position of the chamfer rectangular slot, while a short-circuit probe is added to achieve miniaturization. Therefore, we significantly reduced the size of the antenna and made it exhibit circularly polarized radiation characteristics. A cross-slot is cut in the GND to enable the antenna to better cover the operating band while being able to meet the complex human environment. The effective axis ratio bandwidth is 120 MHz (2.38-2.50 GHz). Its size is π × 0.032λ02 × 0.007λ0 (where λ0 is the free-space wavelength of at 2.4 GHz). In addition, the effect of different organs such as muscle, stomach, small intestine, and big intestine on the antenna when it was embedded into the wireless capsule endoscopy (WCE) system was further discussed, and the results proved that the WCE system has better robustness in different organs. The antenna's specific absorption rate can follow the IEEE Standard Safety Guidelines (IEEE C95.1-1999). A prototype is fabricated and measured. The experimental results are consistent with the simulation results.

Review on Wireless Capsule Endoscopy System Issues, Challenges, and Technologies

Review on Wireless Capsule Endoscopy System Issues, Challenges, and Technologies

Dual-Polarized Transparent Antenna and Its Application for Capsule Endoscopy System

In this paper, we proposed a small transparent thin film antenna for a wireless capsule endoscopy system. The transparent thin film antenna is needed to provide a clear 360° broad-sight view of the wireless capsule system in the future. Furthermore, the transparent thin film is critical for performing the dual-polarized antenna operating at 2.45 GHz. The proposed transparent thin film uses the nano-alignment process to further achieve low resistivity from 3.78 × 10−4 Ω-cm to 9.14 × 10−5 Ω-cm and improves the transparency by over 70%. The nano-alignment process includes periodic electrodes with AC signals that can effectively rearrange the nano-material into an ordered arrangement, enhancing the thin film’s microwave characteristics. Due to applying to the capsule endoscopy system, the ability of water resistance is also considered in this design. Therefore, the O2 plasma treatment is used to improve the water contact angle from 76° to 31°, measured on the surface of the thin film. The proposed transparent antenna is designed to have a center frequency of 2.45 GHz, a bandwidth of 855 MHz, and an antenna gain of −26.3 dBi, and is helpful for capsule endoscopy systems.

A Wideband Dual-Polarized Ring-Loaded Cross Bowtie Antenna for Wireless Capsule Endoscopes: Design and Link Analysis

This work presents a novel on- body wideband dual-polarized antenna to stabilize and enhance the link performance of wireless capsule endoscopy systems. By introducing a cross-bowtie structure with a planar compact feed method, the antenna achieves a dual-polarized performance with high port-to-port isolation. A loaded ring with additional stubs is also implemented to further enhance the bandwidth and provide a flat in-band performance from 381 to 990 MHz. The proposed antenna is measured with both homogeneous phantom and ex vivo test to validate the impedance matching performance. To validate the effectiveness of the proposed on- body antenna on the communication link, a capsule helical antenna with omnidirectional radiation pattern is designed and measured. Finally, comprehensive link studies are conducted considering the varied capsule orientations and locations, with a peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert S_{21}\vert $ </tex-math></inline-formula> value of–25.5 dB at the 60 mm implant depth and an acceptable link loss due to the capsule position error. The proposed on- body antenna can be regarded as a good candidate for a practical capsule endoscopy system due to its stable and enhanced transmission performance when compared with its counterparts.

Nearfield radio link of normal mode helical antenna for wireless capsule endoscopy

Wireless capsule endoscopy (WCE) is designed to monitor the physical data from inside human stomach and gastro intestine (GI) tract and transfer data to the receiver device. Normal mode helical antenna (NMHA) that has high efficiency at a small size is selected for WCE. To clarify the radio wave communication link budget in the dielectric environment is crucial. In this paper, NMHA for WCE system at 402 MHz along with a link budget analysis is presented. The transmitter uses NMHA embedded in a cylindrical phantom mimicking human stomach tissue, whereas the receiver uses another NMHA located outside the body. The NMHA dimension of height and diameter are 18 mm × 11 and 37 mm × 18 mm respectively. Through this study, a novel method of analytical equations for the radio wave communication link in human body are derived. From the good agreement between simulated and measured S21, the effectiveness of derived equations is ensured.

Compacted conformal antenna at lower-UWB for wireless capsule endoscope system

Compacted conformal antenna at lower-UWB for wireless capsule endoscope system

Investigation of Localizing Precise Human Abdomen Models for Wireless Capsule Endoscopy Antenna Design

In order to keep safety of the antenna in wireless capsule endoscopy (WCE) to human body and its use range in different groups of people, 7 human abdomen models are established where the age, tissue thickness and organ shape have been considered. On basis of plane wave propagating theory in lossy multilayered media, each model is composed of simulated skin, subcutaneous fat, muscle, visceral fat and gastrointestinal organ. Different dielectric constant for the biological tissue component is used. A bendable dual-band antenna is designed for the WCE system, conformed to the capsule shell. An L-shaped branch is used to get the better impendence matching. Both the ISM band adopted for data transmission and the WMTS band for midfield wireless power transmission are studied. Fresh pork abdominal tissue samples are used as experiment materials; and it is properly kept consistent with the real human abdominal as far as possible. Experiment results show the performance of antenna stable in the ISM (433 MHz) band. The specific absorption ratio value is checked in different models. Results indicate dielectric parameters varying with age cannot be ignored; and the antenna must be aimed at the middle-aged and elderly population with high gastrointestinal diseases incidence.

In-vivo Experimental Validation of the Attenuation Path Loss Model for Localization of Wireless Implanted Transmitters at 2.45 GHz

Wireless capsule endoscopy (WCE) is a modern, non-invasive method of gastrointestinal examination that can significantly reduce mortality and morbidity. One of the current challenges in WCE is the precise localization of the capsule. An accurate path loss propagation model can be used to find the exact distance from the surface to the capsule inside the abdominal cavity. Unfortunately, there are no standardized In-to-On-Body channel models describing the signal propagation at ultra-high frequencies that are used in the most commercially available WCE systems. This study addresses the gap by conducting an experimental validation of a new propagation model for WCE applications at 2.45 GHz. The results were confirmed by conducting two separate <i>in-vivo</i> trials on porcine animals under general anesthesia. The performance of the model as well as the corresponding ranging errors were evaluated when it was used as an inverse solution for distance estimation to an ingested transmitter. The main advantage of the model is its theoretical basis, which can help further generalize the findings for similar communication scenarios. The obtained ranging error was smaller than one centimeter, suggesting that it can be used for accurate range-based positioning of implanted transmitters.

A miniaturized implantable antenna sensor for wireless capsule endoscopy system

In this paper, a miniaturized antenna sensor with both transmission and sensing capabilities is proposed for wireless capsule endoscopy system. To reduce the volume of the antenna, the proposed antenna adopts double-layer patches for radiation. When integrated in the capsule endoscopy system, the antenna sensor shows the advantage of high peak gain (−9.7 dBi) with a small volume of 2.6 mm × 3 mm × 0.381 mm in 2.4–2.4835 GHz ISM band. In addition, the disease of stomach can be detected by the resonance frequency of the antenna sensor. In order to verify the simulated results, the radiation and sensing performance of the antenna sensor were measured. It can be found that the measured results were consistent with the simulations. Hence, the proposed antenna sensor can be used for wireless data transmission and gastric juice detection for capsule endoscope system.

Ultra-wideband Flexible Implantable Antenna for Wireless Capsule Endoscopy System with Performance Improvement

The implantable antenna is an important part of the wireless capsule endoscopy (WCE) system to achieve wireless communication. This paper designed an ultra-wideband flexible implantable antenna for wireless capsule endoscopy system. With a very wide bandwidth, the antenna can completely cover the industrial, scientific, and medical frequency bands (ISM, 2.4-2.48 GHz) and Wireless Medical Telemetry Service (WMTS, 1.395-1.4 GHz). The expanded size of the proposed antenna is 18mm× 10mm× 0.1mm. The conformal technology of the antenna has further reduced the space of the system and achieved miniaturization. The capsule antenna in this paper is a compact planar monopole antenna fed by a coplanar waveguide, and it uses a flexible material as a dielectric substrate to achieve the conformal shape of the antenna. U-shaped ground branch (UGB) and a loaded split ring resonator (SRR) structure were used to further improve the antenna performance. Simulation and measurement results were basically the same. On the premise of radiation safety and miniaturization of the antenna, the ultra-wideband operation of the antenna was realized. This antenna design provided reference value for the design and application of the capsule antenna.

Compact wideband antenna for wireless capsule endoscopy system

This paper proposes an implantable antenna to be used in either planar or conformal arrangements for implanted biomedical devices. The proposed antenna has a wide bandwidth characteristic. When it is in a conformal shape, the antenna can be used for wireless capsule endoscopy applications. In addition, the antenna can be a good candidate for biotelemetry applications while it is planar. A cubic phantom model was adopted in simulations for the initial design and optimization of the conformal antenna structure. The antenna was designed on the outer wall of the capsule to provide more space for other electronics inside. Implanted antennas are subject to detuning effects due to the proximity of various tissues in the gastrointestinal tract, presence of the electronic module in the capsule, different biocompatible coating thicknesses, and different bending conditions. Having a wide bandwidth makes this antenna less sensitive to these detuning effects. Performance of the proposed antenna was experimentally validated in the planar and conformal forms by using a solid muscle-mimicking phantom. Based on measurements, antenna exhibits wide impedance bandwidths, from 170 to 3500 MHz for the conformal antenna, and from 650 to 3600 MHz for the planar antenna inside muscle tissue phantom.

A Conformal UWB Dual-Polarized Antenna for Wireless Capsule Endoscope Systems

A conformal ultrawideband (UWB) dual-polarized capsule antenna is designed for ingestible wireless capsule endoscope (WCE) systems. To the best of our knowledge, this is the first time to study the UWB dual-polarized antenna for a capsule endoscope system. Dual polarization is realized by a step-shaped monopole and an irregular rectangular loop antenna, which are printed on the top and bottom side of the dielectric substrate, separately. The simulated antenna has very wide -10 dB impedance bandwidth of 2.15-14.75 GHz, which can cover 2.4-2.48 GHz, 5.725-5.875 GHz Industrial, Scientific, and Medical (ISM) band, 3.5-4.5 GHz impulse radio UWB (IR-UWB) and 3.1-10.6 GHz UWB. Moreover, because of the orthogonally polarized waves generated by two types of antennas, the simulated isolation between them is better than 40 dB in the whole band. Considering the application of the antenna in the wireless body area network system, this design focuses on 1-7 GHz frequency band, especially 4 GHz IR-UWB. An antenna prototype is fabricated and measured, and the measured S-parameters and radiation pattern demonstrate a reasonable agreement with the simulation results. Furthermore, specific absorption rate and link budget of the antenna are analyzed.

Design of a Dual-Polarized Omnidirectional Dielectric Resonator Antenna for Capsule Endoscopy System

In this paper, a new dual-polarized (DP) omnidirectional hemisphere dielectric resonator antenna (DRA) for wireless capsule endoscope system (WCE) is proposed. The antenna was excited in its omnidirectional TM018 and TE018 modes to radiate DP wave by a feeding probe and arc microstrip line, respectively. Omnidirectional DP wave can be obtained when the TM018 and TE018 mode are equal in amplitude and phase. The TM018 mode that is equivalent to electric dipole can be obtained by probe feeding. The TE018 mode is excited by four arc microstrip lines feeding. They provide a pair of equivalent magnetic dipoles that are orthogonal to TM018 mode. The DP omnidirectional DRA be fabricated without the need of feed network than circularly polarized. The WCE and the human body equivalent tissue model are adopted in simulation. Water is equivalent to gastric juice during measurement. Communication links between the proposed capsule antenna and the external receiving antenna are measured to demonstrate the advantages the DP brings when capsule antenna is placed in different orientations. The capsule endoscope system with different antennas is placed in water to measure receiving power. The measurement shows that the fabricated antenna exhibits a wide impedance bandwidth for S11 <; -10 dB (2.4-2.48 GHz). The radiation efficiency of the antenna is between 15-18%, and the peak gain is between -13.5 and -15dBi.

Colored Video Analysis in Wireless Capsule Endoscopy: A Survey of State-of-the-Art.

Wireless Capsule Endoscopy (WCE) is a highly promising technology for gastrointestinal (GI) tract abnormality diagnosis. However, low image resolution and low frame rates are challenging issues in WCE. In addition, the relevant frames containing the features of interest for accurate diagnosis only constitute 1% of the complete video information. For these reasons, analyzing the WCE videos is still a time consuming and laborious examination for the gastroenterologists, which reduces WCE system usability. This leads to the emergent need to speed-up and automates the WCE video process for GI tract examinations. Consequently, the present work introduced the concept of WCE technology, including the structure of WCE systems, with a focus on the medical endoscopy video capturing process using image sensors. It discussed also the significant characteristics of the different GI tract for effective feature extraction. Furthermore, video approaches for bleeding and lesion detection in the WCE video were reported with computer-aided diagnosis systems in different applications to support the gastroenterologist in the WCE video analysis. In image enhancement, WCE video review time reduction is also discussed, while reporting the challenges and future perspectives, including the new trend to employ the deep learning models for feature Learning, polyp recognition, and classification, as a new opportunity for researchers to develop future WCE video analysis techniques.

What is the effective clinical use of small bowel capsule endoscopy in real life?

Capsule endoscopy is a noninvasive and easy method for evaluating the gastrointestinal tract. Since the wireless capsule endoscopy system was first developed, many new technical improvements have been made in order to gain maximum benefit from the procedure. However, at this stage, it remains a diagnostic modality, the main indication for its use being obscure gastrointestinal bleeding. Capsule endoscopy is only contraindicated in symptomatic intestinal obstruction. New indications for use and therapeutic options may become possible with the further development of nanotechnologies.

Automated Detection of Bleeding in Capsule Endoscopy Using On-Chip Multispectral Imaging Sensors

Gastrointestinal (GI) bleeding is a common problem and may lead to fatal consequences. The detection of bleeding is currently determined through conventional examination of wireless capsule endoscopy (WCE) images. Image-based bleeding detection is performed using only color pixels; therefore, image and color distortion affect the accuracy of RGB-based methods adversely. On the other hand, imaging modalities like multispectral features contain several unique characteristics of the target material, and therefore are less error-prone. In this regard, an on-chip bleeding detection sensor based on blood's optical properties is developed in this article. For creating this sensor, an array of 12 optical sensors, six in visible and six in near-infrared range, is tested with blood samples (BS) in various concentrations and non-blood samples (NBS), such as food pigments and natural foods (digestible and nondigestible). Various feature selection and machine learning approaches have been used to select the optimal bandwidth for the best detection accuracy. A capsule prototype is designed that uses 450 nm, 610 nm, and 810 nm of wavelengths. The prototype is tested in two in vitro experiments using two porcine intestines to validate the proof of concept. The results indicate that the designed system can distinguish occult and acute bleeding from a distance of 1 cm with angles of 45 and 90 degrees. An F1-score of 99% is achieved using the bagged decision tree algorithm. The proposed solution for detecting GI bleeding will eliminate the need to use a camera module and large data transmission, and thereby consumes 1.48 times less power than conventional WCE systems.

A Circularly Polarized Omnidirectional Antenna for Wireless Capsule Endoscope System

This article presents the first report of a circularly polarized (CP) omnidirectional radiation antenna for wireless capsule endoscope (WCE) system applications. The proposed antenna incorporates an integrated design concept, and achieves operation at 0.915 GHz Industrial, Scientific, and Medical (ISM) band (0.902-0.928 GHz) with a compact size of π×5.5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ×22 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The simulation is performed in Ansys HFSS, with the antenna being placed in the center of a cylindrical homogeneous muscle tissue with a size of π×55 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ×80 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The simulated results show that the capsule antenna has an impedance bandwidth (BW) ( |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB) from 0.82 to 0.99 GHz and a CP BW (AR <; 3 dB) from 0.84 to 1.09 GHz. Moreover, the omnidirectional CP radiation properties remain stable for a very wide θ range (49°-144°) in the elevation plane. The robust CP performance and the integrated design concept make the proposed antenna suitable for advanced WCE systems.

Miniaturized Dual-Band Circularly Polarized Implantable Antenna for Capsule Endoscopic System

This study proposes a miniaturized dual-band antenna with a circular-polarization characteristic for a wireless-capsule endoscopic system operating in the industrial, scientific, and medical bands: 915 and 2450 MHz. The proposed capsule device is intended for deep-tissue implantation with the standard dimensions of 26×11 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The key features of the proposed antenna are its CP characteristic at both bands, satisfactory gain values, and a smallest volume ( 6.5×6.5×0.05=2.11 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) with a via-less ground plane compared with the state-of-the-art device. The CP wave performance and the miniaturization of the antenna are achieved via the introduction of slots accompanied by meandered line segments in a radiating patch and open-end slots in a ground plane. Furthermore, the proposed antenna offers a reasonable axial ratio (AR) of <; 3 dB at the desired frequency bands. The circularly polarized radiator attains the AR bandwidths (BWs) of 33.0% and 8.67% and the measured -10 dB impedance BWs of 13.63% and 6.28% at 915 and 2450 MHz, respectively. The measurements of the reflection coefficient and radiation pattern are performed using a fabricated prototype of the proposed antenna system in a saline solution and minced pork. Finally, the safety considerations and link budget calculations are evaluated to analyze the performance of the proposed capsule device. Due to the AR BW, impedance BW, and ease of fabrication, the proposed antenna system is a suitable candidate for use in endoscopic applications.

A Fluorescence-Based Wireless Capsule Endoscopy System for Detecting Colorectal Cancer.

Wireless capsule endoscopy (WCE) has been widely used in gastrointestinal (GI) diagnosis that allows the physicians to examine the interior wall of the human GI tract through a pain-free procedure. However, there are still several limitations of the technology, which limits its functionality, ultimately limiting its wide acceptance. Its counterpart, the wired endoscopic system is a painful procedure that demotivates patients from going through the procedure, and adversely affects early diagnosis. Furthermore, the current generation of capsules is unable to automate the detection of abnormality. As a result, physicians are required to spend longer hours to examine each image from the endoscopic capsule for abnormalities, which makes this technology tiresome and error-prone. Early detection of cancer is important to improve the survival rate in patients with colorectal cancer. Hence, a fluorescence-imaging-based endoscopic capsule that automates the detection process of colorectal cancer was designed and developed in our lab. The proof of concept of this endoscopic capsule was tested on porcine intestine and liquid phantom. The proposed WCE system offers great possibilities for future applicability in selective and specific detection of other fluorescently labelled cancers.

Performance of Predictive Coders for Wireless Capsule Endoscopy Image Compression

Wireless capsule endoscopy is a medical diagnostic technique developed for the endoscopic examination of the small bowel. The encoder module is the core of the wireless capsule endoscopic system impacting on power and area requirement for the hardware implementation of the capsule. One of the remarkable features of the endoscopic image is that the neighboring pixels are highly correlated. Two predictive coding techniques are considered in this work exploiting the above fact. The first predictive coder i.e., DPCM coder is based on previous horizontal neighboring pixel, whereas the second predictive coder is based on adjacent horizontal and diagonal neighbors. The performance of the predictive coders is tested with 41 small bowel type endoscopic images available in the Gastrolab dataset. The results show that the average compression rate and peak signal to noise ratio attained by DPCM coder and newly tested predictive coder are 66.37 % &amp; 73.03 % and 32.17 dB &amp; 35.55 dB, respectively.