Physical Multi-Layer Phantoms for Intra-Body Communications

This paper presents approaches to creating tissue mimicking materials that can be used as phantoms for evaluating the performance of Body Area Networks (BAN). The main goal of the paper is to describe a methodology to create a repeatable experimental BAN platform that can be customized depending on the BAN scenario under test. Comparisons between different material compositions and percentages are shown, along with the resulting electrical properties of each mixture over the frequency range of interest for intra-body communications; 100 KHz to 100 MHz. Test results on a composite multi-layer sample are presented confirming the efficacy of the proposed methodology. To date, this is the first paper that provides guidance on how to decide on concentration levels of ingredients, depending on the exact frequency range of operation, and the desired matched electrical characteristics (conductivity vs. permittivity), to create multi-layer phantoms for intra-body communication applications

Estudio de la variabilidad de las medidas de comunicaciones intracorporales ante diferentes sujetos con diferentes características

El significativo avance de las Tecnologías de la Información y la Comunicación (TIC) en los últimos tiempos permite su aplicación en el sector de la salud de numerosas maneras, aportando beneficios de calidad, seguridad y un importante ahorro económico. En este ámbito toman gran relevancia los Sistemas de Salud Personales (PHS) que suponen una innovación ideada para ofrecer una asistencia sanitaria ininterrumpida, individualizada y de calidad controlada. En este marco se presentan las redes de sensores corporales (BSN) como una solución para el seguimiento de personas con problemas de salud, ya que las redes de sensores corporales surgen como respuesta a la necesidad de garantizar la individualización en la asistencia sanitaria y la prevención, así como mejorar la calidad de vida del paciente. Las redes inalámbricas de sensores proporcionan sistemas personalizados de atención médica que permiten la monitorización remota del paciente [1] en cualquier momento y lugar. Que el paciente sea supervisado las 24 horas del día influye en la necesidad de considerar que estas redes de sensores sean inalámbricas para una mayor comodidad, así como el tamaño de los sensores, u otros aspectos como el consumo de baterías, la inmunidad frente a interferencias, el alcance y la tasa de transmisión de datos. Zigbee o Bluetooth Low Energy (BLE) son estándares de comunicaciones empleados en redes inalámbricas de área personal que actualmente son implementadas pero con una serie de limitaciones [2] como: el número de dispositivos que se pueden usar, la velocidad [3] de transmisión de datos o interferencias con dispositivos que trabajen en la misma frecuencia. Debido a estas limitaciones surgieron las Intrabody Communication (IBC). Las Intrabody Communication emplean el cuerpo humano como medio de transmisión de las señales eléctricas para la interconexión de sensores inalámbricos en los sistemas de monitorización biomédicos. En este caso, la señal queda confinada en la superficie de la piel sin radiar al exterior, por lo que disminuye tanto las interferencias con dispositivos cercanos, como el consumo. Por ello, este tipo de comunicación es adecuada para aplicaciones biomédicas. No obstante, al ser las señales transmitidas a través de la superficie corpotal, se ven condicionadas por las propiedades de los tejidos vivos creando incertidumbre en las medidas. En este trabajo se ha realizado un análisis de la influencia de las características antropométricas en las comunicaciones intracorporales. Para ello, y como consecuencia de la falta de estandarización en las medidas en IBC y la incertidumbre que presenta el cuerpo humano, se ha empleado un modelo circuital (phantom) con el propósito de validar los distintos montajes experimentales empleados antes de las pruebas finales sobre voluntarios. Dicho phantom modela el comportamiento en frecuencia de los distintos tejidos que componen el brazo humano. El análisis fue realizado desde dos puntos de vista. En primer lugar se analizó la impedancia de entrada, con el propósito de estimar la corriente inyectada y mantenerla dentro de los márgenes de seguridad. En segundo lugar se analizó la atenuación de la señal en diversas frecuencias y diferentes distancias con el propósito de proporcionar información sobre las características del canal de comunicaciones corporal. A continuación, se procedió a realizar las medidas experimentales con dos sujetos de diferentes características. Las diferencias encontradas pusieron de manifiesto la importancia de las características antropométricas en las comunicaciones corporales. Como la señal se atenuaba rápidamente a medida que aumentaba la distancia, se encontraron serios problemas a la hora de medir en distancias superiores a 12 cm. El ruido en los niveles de señal obtenidos también resultaba importante, lo que impedía la realización de medidas objetivas para distancias mayores. Para resolver el problema de la señal atenuada se diseñó una etapa amplificadora en recepción. Para ello se realizó un estudio de amplificadores y de posibles configuraciones de circuitos para conseguir amplificar la señal. Aun solventando este problema de la atenuación, la señal seguía estando interferida por el ruido. Se realizó un proceso iterativo para eliminar el ruido de la señal implementando un circuito electrónico de captura de señal con tres electrodos. Este tercer terminal permitía obtener un punto de referencia para las medidas y de esta forma se conseguía eliminar el ruido. Se realizaron simulaciones en el osciloscopio para analizar los efectos que se producían en la señal recibida cuando se implementaba el tercer electrodo en las mediciones. Una vez comprobado los efectos, se volvieron a realizar medidas con diferentes personas para estudiar la influencia de las características de los distintos sujetos. Los resultados obtenidos para los dos sujetos con el setup mejorado fueron muy distintos, y estos resultados, a su vez, discrepaban de los resultados obtenidos para los dos sujetos de la primera experimentación. El setup mejorado ha permitido realizar medidas del canal de comunicaciones corporal a mayores distancias que el setup inicial. Los circuitos electrónicos de la etapa de captura de señal para la amplificación y eliminación de ruido con el tercer electrodo podrían ser empleados para optimizar las prestaciones de un transceptor en comunicaciones intracorporales.The significant advancement of information and communications technology (ICT ) in recent times allows implementation in the health sector in many ways providing quality benefits , safety and significant financial savings. In this area Personal Health Systems ( PHS ) take great relevance which represent an innovation designed to deliver an uninterrupted , individualized and quality controlled health care. In this framework the body sensor networks (BSN ) are shown as a solution for tracking people with health problems because the body sensor networks arise in response to the necesity to ensure individualization in health care and prevention as well as improve the quality of life of patients. Wireless sensor networks provide personalized health care systems that allow remote monitoring of the patient at any time and place. The patient is monitored 24 hours a day influences the need to consider these sensor networks are wireless for comfort as well as the size of the sensors, or other aspects such as battery consumption, immunity against interference the extent and rate of data transmission. Standards such as Zigbee or Bluetooth Low Energy ( BLE ) are wireless personal area networks that they are currently implemented but with a number of limitations such as the number of devices that it can be used , the speed of data transmission or interference with devices that work in the same frequency. Because of these limitations intrabody Communication ( IBC ) emerged. The Intrabody Communication employ the human body as a transmission medium of electrical signals to interconnect wireless sensor in biomedical monitoring systems. In this case, the signal is confined to the skin surface without radiating to the outside, thereby decreasing both interference with nearby devices such as consumption. Therefore, this type of communication is suitable for biomedical applications. However, when signals are transmitted through the corpotal surface, they are conditioned by the properties of living tissue by creating uncertainty in the measurements. The analysis was conducted from two points of view. Firstly, the input impedance was analyzed in order to estimate the injected current and keep within safety margins analyzed. Secondly, the signal attenuation at different frequencies and different distances was analyzed in order to provide information on the channel characteristics body communications. Then it proceeded to perform experimental measurements with two subjects with different characteristics. The differences highlighted the importance of anthropometric characteristics in body communications. As the signal is attenuated rapidly with increasing distance, serious problems when measured at distances exceeding 12 cm were found. The noise in the signal levels obtained also was important, which prevented the realization of objective measures for greater distances. To solve the problem of the attenuated signal design a amplifier stage in reception. For this, study amplifiers and possible circuit configurations was performed for amplifying the signal. Even solving this problem of attenuation, the signal was still interfered by noise. An iterative process was performed to remove noise signal implementing a phantom with three terminals. This third terminal allowed to obtain a reference point for measurements and thus eliminate noise was achieved. Simulations were performed on the oscilloscope to analyze the effects that occurred in the received signal when the third electrode was implemented in measurements. Once verified the effects, measurements with different people returned to perform to study the influence of the characteristics of the different subjects. The results obtained for the two subjects with improved setup were very different, and these results, in turn, results obtained differed for the two subjects of the first experimentation. The setup has allowed improved measures body channel communications over greater distances than the initial setup. The electronic circuitry of the capture step signal for amplification and elimination of noise with the third electrode could be used to optimize the performance of a transceiver in intracorporeal communications.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

Evaluation of Propagation Characteristics Using the Human Body as an Antenna

In this paper, an inhomogeneous human body model was presented to investigate the propagation characteristics when the human body was used as an antenna to achieve signal transmission. Specifically, the channel gain of four scenarios, namely, (1) both TX electrode and RX electrode were placed in the air, (2) TX electrode was attached on the human body, and RX electrode was placed in the air, (3) TX electrode was placed in the air, and RX electrode was attached on the human body, (4) both the TX electrode and RX electrode were attached on the human body, were studied through numerical simulation in the frequency range 1 MHz to 90 MHz. Furthermore, the comparisons of input efficiency, accepted efficiency, total efficiency, absorption power of human body, and electric field distribution of different distances of four aforementioned scenarios were explored when the frequency was at 44 MHz. In addition, the influences of different human tissues, electrode position, and the distance between electrode and human body on the propagation characteristics were investigated respectively at 44 MHz. The results showed that the channel gain of Scenario 4 was the maximum when the frequency was from 1 MHz to 90 MHz. The propagation characteristics were almost independent of electrode position when the human body was using as an antenna. However, as the distance between TX electrode and human body increased, the channel gain decreased rapidly. The simulations were verified by experimental measurements. The results showed that the simulations were in agreement with the measurements

Modelamiento de redes de transmisión inalámbricas para la comunicación de sensores dentro del cuerpo humano

En esta tesis se realiza una comparación entre los modelos actualmente existentes para el modelado de transmisión de señales en el cuerpo humano más concretamente IBC, para esto se desarrolló un modelo por diferencias finitas para evaluar el SAR (Tasa de absorción específica) en las diferentes capas orgánicas del cuerpo humano, realizando esta simulación entre capas a diferentes frecuencias con el fin observar su comportamiento y validarlo contra los parámetros del estándar IEEE 802.15.6. Lo cual dio resultados de tasa de absorción con un máximo de 0.15 W/kg a 20 GHz y con una tendencia a disminuir a menores frecuencias.Abstract: In this thesis a comparison is made between the currently existing models for the modeling of signal transmission in the human body, more specifically IBC, for this a model was developed by finite differences to evaluate the SAR (Specific absorption rate) in the different organics layers of the human body, performed this simulation between layers at different frequencies in order to observe their behavior and validate it against the parameters of the IEEE 802.15.6 standard.Maestrí

A survey on wireless body area networks for eHealthcare systems in residential environments

The progress in wearable and implanted health monitoring technologies has strong potential to alter the future of healthcare services by enabling ubiquitous monitoring of patients. A typical health monitoring system consists of a network of wearable or implanted sensors that constantly monitor physiological parameters. Collected data are relayed using existing wireless communication protocols to the base station for additional processing. This article provides researchers with information to compare the existing low-power communication technologies that can potentially support the rapid development and deployment of WBAN systems, and mainly focuses on remote monitoring of elderly or chronically ill patients in residential environments

Conformable transistors for bioelectronics

The diversity of network disruptions that occur in patients with neuropsychiatric disorders creates a strong demand for personalized medicine. Such approaches often take the form of implantable bioelectronic devices that are capable of monitoring pathophysiological activity for identifying biomarkers to allow for local and responsive delivery of intervention. They are also required to transmit this data outside of the body for evaluation of the treatment’s efficacy. However, the ability to perform these demanding electronic functions in the complex physiological environment with minimum disruption to the biological tissue remains a big challenge. An optimal fully implantable bioelectronic device would require each component from the front-end to the data transmission to be conformable and biocompatible. For this reason, organic material-based conformable electronics are ideal candidates for components of bioelectronic circuits due to their inherent flexibility, and soft nature. In this work, first an organic mixed-conducting particulate composite material (MCP) able to form functional electronic components and non-invasively acquire high–spatiotemporal resolution electrophysiological signals by directly interfacing human skin is presented. Secondly, we introduce organic electrochemical internal ion-gated transistors (IGTs) as a high-density, high-amplification sensing component as well as a low leakage, high-speed processing unit. Finally, a novel wireless, battery-free strategy for electrophysiological signal acquisition, processing, and transmission that employs IGTs and an ionic communication circuit (IC) is introduced. We show that the wirelessly-powered IGTs are able to acquire and modulate neurophysiological data in-vivo and transmit them transdermally, eliminating the need for any hard Si-based electronics in the implant