In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of ∼0.7 dB and ∼1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

Characterization of the Fat Channel for Intra-Body Communication at R-Band Frequencies

In recent studies, it has been found that fat tissue can be used as a microwave communication channel. In this article, the effect of thickness inhomogeneities in fat tissues on the performance of in-body microwave communication at 2.45 GHz is investigated using phantom models. We considered two models namely concave and convex geometrical fat distribution to account for the thickness inhomogeneities. The thickness of the fat tissue is varied from 5 mm to 45 mm and the Gap between the transmitter/receiver and the starting and ending of concavity/convexity is varied from 0 mm to 25 mm for a length of 100 mm to study the behavior in the microwave propagation. The phantoms of different geometries, concave and convex, are used in this work to validate the numerical studies. It was noticed that the convex model exhibited higher signal coupling by an amount of 1 dB (simulation) and 2 dB (measurement) compared to the concave model. From the study, it was observed that the signal transmission improves up to 30 mm thick fat and reaches a plateau when the thickness is increased further.

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Effect of Thickness Inhomogeneity in Fat Tissue on In-Body Microwave Propagation

Recently, interest in medical and health monitoring systems has increased significantly, since these have the potential to address some of the challenges related to the aging population. Furthermore, medical monitoring enhances diagnosis and medical treatments in hospitals. New self and remote diagnosis and monitoring solutions are being developed and implemented constantly. Smooth design of monitoring devices requires deep knowledge of off-body, on-body, and in-body propagation. This thesis presents studies on in-body propagation for different wireless body area network (WBAN) applications. The main focuses are on 1) survey of the electromagnetic (EM) simulation techniques used in WBAN applications, 2) in-body propagation in the human chest area, and 3) in-body propagation in the human abdomen area. The study is carried out using radio channel measurements, finite integration technique -based channel simulations, as well as propagation path calculations. Part 2 involves studies on the impact that medical implants, which contain highly conductive materials, may have impact on channel characteristics. Sternotomy wires and an aortic valve implant are considered as example cases. This knowledge is useful for the design of monitoring devices in which the antennas are located on the chest area, especially close to the sternum. Part 3 shows how signal propagates inside the abdomen preferring the tissues which are easier for propagation due to their dielectric properties. This knowledge is useful for abdominal monitoring system design, especially antenna location design, for instance in capsule endoscopy. Part 3 also involves studies of the channel evaluations between the receiving on-body antenna and the capsule endoscope in different parts of the intestine area. Human voxels with different sizes and body constitutions are used in this study. In general, the results presented in this thesis provide new information on the propagation within the tissues, which is useful for designing monitoring devices for different WBAN applications.

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UWB in-body propagation and radio channel characteristics for wireless body area network applications

This paper presents comprehensive study on fat as propagation medium in abdominal implant communication system at low ultrawideband (UWB) frequency range 3.75-4.25 GHz. The main aim is to investigate how signal propagates through visceral and subcutaneous fat layers and how that information can be exploited in implant communication systems. The study is conducted using different methods: electromagnetic simulations, power flow analysis, propagation path calculations and radio channel measurements with animal meat pieces. Simulations are conducted using layer models and anatomical voxel models having different sizes. Results of channel simulations are verified with propagation path calculations. Power flow analysis on cross-cuts of the voxel models is conducted to investigate how the signal propagates inside the tissues. Furthermore, measurements using different animal meat pieces are performed to evaluate the impact of fat constitution on channel characteristics. It is found that similar tendency on fat propagation is seen in the evaluations with different methods. It is also observed that channel attenuation depends not only on the types and thicknesses of the tissues between transmitter and receiver antennas, but also how the tissues, especially fat, is located between the antennas. Channel attenuation difference between different voxels is maximum 14 dB in the studied antenna locations. Furthermore, propagation channel is evaluated with measurements using pork meat having different fat and muscle constitutions. It is found that antenna location respect to fat layers has clear impact on the channel strength although the fat tissue is not directly above the in-body antenna. The difference is noted to be 3–15 dB especially on the side peaks of channel impulse response. The knowledge on fat as a propagation medium is crucial when designing medical monitoring or implant communication systems. Location of antennas/sensor nodes for the monitoring devices can be established so that propagation through fat layer can be exploited.

/pdf/simulation-and-measurement-data-based-study-on-fat-as-3qdik7kk5n.pdf

Simulation and Measurement Data-Based Study on Fat as Propagation Medium in WBAN Abdominal Implant Communication Systems

The potential offered by the intra-body communication (IBC) over the past few years has resulted in a spike of interest for the topic, specifically for medical applications. Fat-IBC is subsequently ...

/pdf/assessment-of-blood-vessel-effect-on-fat-intrabody-1lp73ss3jv.pdf

Assessment of Blood Vessel Effect on Fat-Intrabody Communication Using Numerical and Ex-Vivo Models at 2.45 GHz

Recently, the human fat tissue has been proposed as a microwave channel for intra-body sensor applications. In this work, we assess how disturbances can prevent reliable microwave propagation through the fat channel. Perturbants of different sizes are considered. The simulation and experimental results show that efficient communication through the fat channel is possible even in the presence of perturbants such as embedded muscle layers and blood vessels. We show that the communication channel is not affected by perturbants that are smaller than 15 mm cube.

/pdf/reliability-of-the-fat-tissue-channel-for-intra-body-466x37gbx3.pdf

Yaiful Redzwan

Papers

Reliability of the fat tissue channel for intra-body microwave communication