On-body Receiver Research Articles

Error reduction through post processing for wireless capsule endoscope video

The wireless capsule endoscope (WCE) is a pill-sized device taking images, which are transmitting to an on-body receiver, while traveling through the digestive system. Since image data is transmitted through the human body, which is a harsh medium for electromagnetic wave propagation, noise may at times heavily corrupt the reconstructed image frames. A common way to combat noise is to use error-correcting codes. In addition one may also utilize inter- and intra frame correlation to reduce the impact of noise at the receiver side, placing no extra demand on the WCE. However, it is then of great importance that the chosen post processing methods do not alter the content of the image as this can lead to miss-detection by gastroenterologists. In this paper we will investigate the possibility for additional noise suppression and error concealment at the receiver side in a high intensity error regime. Due to the high correlation generally inherent in WCE video, satisfactory results are obtained, as concluded from both subjective tests with gastroenterologists as well as the structural similarity (SSIM) metric. More surprisingly, the subjective tests indicate that the inpainted frames in many cases can be used for clinical assessment. These results indicate that one can apply error reduction through post processing together with error-correcting codes to obtain a more noise-robust system without any further demand on the WCE.

A Stochastic Channel Model for Ultra Wideband In-Body Communication.

For wireless capsule endoscopy, high quality images need to be transmitted from inside the digestive tract to an on-body receiver. Ultra wideband transmission offers the possibility to achieve much larger data rates than achievable with today's technology. To design such an ultra wideband transmission system a comprehensible channel model is needed for simulation of the propagation behavior through the human abdomen. In this paper we present a stochastic channel model, that includes the variation of the radio propagation depending on the location of a receive antenna on the body as well as on the physiological properties of different human body models.

Antenna System Design for Improved Wireless Capsule Endoscope Links at 433 MHz

Wireless capsule endoscopy (WCE) systems are used to capture images of the human digestive tract for medical applications. The antenna is one of the most important components in a WCE system. In this paper, we present novel small antenna solutions for a WCE system operating at the 433 MHz ISM band along with a link budget analysis. The in-body capsule transmitter uses an ultrawideband outer wall conformal loop antenna, whereas the on-body receiver uses a printed monopole antenna with a partial ground plane. A colon-equivalent tissue phantom and CST Gustav voxel human body model were used for the numerical studies of the capsule antenna. The simulation results in the colon-tissue phantom were validated through in vitro measurements using a liquid phantom. According to the phantom simulations, the capsule antenna has −10 dB impedance matching from 309 to 1104 MHz. The ultrawideband characteristic enables the capsule antenna to tolerate the detuning effects due to electronic modules in the capsule and due to the proximity of various different tissues in gastrointestinal tracts. The same design methodology was applied to on-body antennas followed by in vitro and ex vivo measurements for validation. The on-body antenna exceeds −10 dB impedance matching from 385 to 502 MHz both in simulations and measurements. The path loss for the radio link between an in-body capsule transmitter and an on-body receiver using our antenna solutions, in simulations and measurements, is less than 50 dB for any capsule orientation and location, ensuring sufficient signal level at the receiver, hereby enabling an improved capsule endoscope.

A Broadband Implantable and a Dual-Band On-Body Repeater Antenna: Design and Transmission Performance

The design of a new miniature broadband implantable antenna and a dual-band on-body antenna are presented along with the transmission performance between the two. The former and latter antennas are intended for integration into implantable medical devices (IMDs) and on-body repeaters, respectively. The on-body repeater antenna favors the use of very low power IMDs. The on-body repeater receives low power data from an IMD (MedRadio band, 401-406 MHz) and retransmits it to remote devices placed further apart (ISM band, 2400-2480 MHz ). The MedRadio implantable antenna maintains miniature size (399 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), and exhibits two close resonances which increase the -10 dB bandwidth inside muscle tissue (87 MHz). The on-body antenna is relatively small (6720 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), and exhibits dual resonances in the MedRadio and ISM bands. Assuming a typical arm implantation scenario and an on-body receiver sensitivity of -75 dBm, the proposed configuration is found to enable reduction of the IMD power by a factor of 100. Patient safety and tolerance to electromagnetic interference are, thus, preserved, and lifetime of the IMD is increased. The setup is, finally, shown to be robust to antenna misalignment and polarization rotation.

A Novel Pathloss Model for Angular and Spatial Dependency of Ultra Wideband Off-Body Radio Channels

In this paper variations in path loss model with respect to distance and orientation of human body for both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios for ultra wideband off-body communication is experimentally and statistically investigated. Results show that for every 1° change in orientation angle between off-body transmitter and on-body receiver, path loss varies by almost 0.097 dB for LOS case and 0.12 dB for NLOS case. A novel path loss model with respect to distance and angle is also presented in this paper.

LINK BUDGET OF MAGNETIC ANTENNAS FOR INGESTIBLE CAPSULE AT 40 MHZ

Magnetic antennas are suitable in short range medical in-body applications because they are less perturbed in the presence of the human tissues comparing to electrical antennas. After a preliminary study on magnetic antennas designed separately at 40 MHz with a matching system, a link budget between a spiral coil ingestible capsule transmitter antenna and a square coil onbody receiver antenna has been established in the presence of the human body. The efficiency (ratio of received power to transmitted power) of the magnetic induction link through a homogeneous human body (muscle) is equal to 0.6 % when the TX (transmitter) capsule is in front of the RX (receiver) antenna. If the transmission channel is a three-layered human body (muscle / fat / skin) the performances of the inductive link can be enhanced and the efficiency reaches 0.8 %. These performances can be improved (up to 1 %) when the dimensions of the receiver antenna increase. Consequently, the power consumption can be reduced and hence the battery life of the wireless capsule increases. Additionally, when the TX antenna is located randomly at an arbitrary orientation and position, the efficiency of the magnetic induction link can be improved by orienting the RX antenna parallel and perpendicularly to the human body surface.