Electromagnetic radiation from ingested sources in the human intestine between 150 MHz and 1.2 GHz

The conventional method of diagnosing disorders of the human gastro-intestinal (GI) tract is by sensors embedded in cannulae that are inserted through the anus, mouth, or nose. However, these cannulae cause significant patient discomfort and cannot be used in the small intestine. As a result, there is considerable ongoing work in developing wireless sensors that can be used in the small intestine. The radiation characteristics of sources in the GI tract cannot be readily calculated due to the complexity of the human body and its composite tissues, each with different electrical characteristics. In addition, the compact antennas used are electrically small, making them inefficient radiators. This paper presents radiation characteristics for sources in the GI tract that should allow for the optimum design of more efficient telemetry systems. The characteristics are determined using the finite-difference time-domain method with a realistic antenna model on an established fully segmented human body model. Radiation intensity outside the body was found to have a Gaussian-form relationship with frequency. Maximum radiation occurs between 450 and 900 MHz. The gut region was found generally to inhibit vertically polarized electric fields more than horizontally polarized fields

A system-on-chip digital pH meter for use in a wireless diagnostic capsule

This paper describes the design and implementation of a system-on-chip digital pH meter, for use in a wireless capsule application. The system is organized around an 8-bit microcontroller, designed to be functionally identical to the Motorola 6805. The analog subsystem contains a floating-electrode ISFET, which is fully compatible with a commercial CMOS process. On-chip programmable voltage references and multiplexors permit flexibility with the minimum of external connections. The chip is designed in a modular fashion to facilitate verification and component re-use. The single-chip pH meter can be directly connected to a personal computer, and gives a response of 37 bits/pH, within an operating range of 7 pH units

UWB Path Loss Models for Ingestible Devices

[EN] Currently, some medical devices such as the Wireless Capsule Endoscopy (WCE) are used for data transmission from inside to outside the body. Nevertheless, for certain applications such as WCE, the data rates offered by current medical frequency bands can result insufficient. Ultra Wideband (UWB) frequency band has become an interesting solution for this. However, to date, there is not a formal channel path loss model for the UWB frequency band in the gastrointestinal (GI) scenario due to the huge differences between the proposed studies. There are three main methodologies to characterize the propagation channel, software simulations and experimental measurements either in phantom or in in vivo animals. Previous works do not compare all the methodologies or present some disagreements with the literature. In this paper, a dedicated study of the path loss using the three methodologies aforementioned (simulations, phantoms and in vivo measurements) and a comparison with previous researches in the literature is performed. Moreover, numerical values for a path loss model which agrees with the three methodologies and the literature are proposed. This paper aims at being the starting point for a formal path loss model in the UWB frequency band for WBANs in the GI scenarioThis work was supported in part by the European Union's H2020-MSCA-ITN Program for the "Wireless In-body Environment Communication" Project under Grant 675353, in part by the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-16) from Universitat Politecnica de Valencia, and in part by the Ministerio de Economia y Competitividad, Spain under Grant TEC2014-60258-C2-1-R through the European FEDER Funds.Pérez-Simbor, S.; Andreu-Estellés, C.; Garcia-Pardo, C.; Frasson, M.; Cardona Marcet, N. (2019). UWB Path Loss Models for Ingestible Devices. IEEE Transactions on Antennas and Propagation. 67(8):5025-5034. https://doi.org/10.1109/TAP.2019.2891717S5025503467

Development of multi-material phantoms and implanted monopole antennas for bone fracture monitoring

This thesis presents a novel method for monitoring the healing of severe bone fractures. This would be particularly useful during the first two to four weeks after trauma where x-ray and computerised tomography scanning cannot provide an accurate indication regarding the healing status of the fractured bone. The technique involves measuring the radiofrequency transmission from one bone-implanted monopole to another, each one located on either side of the bone fracture. Throughout this thesis, it is envisaged that the monopoles will also act as the screws of an external fixation implanted into patients for the stabilization and alignment of the bone fragments. To replicate a simplified version of a human limb, several multi-material semi-solid phantoms were developed to represent bone marrow, bone cortical, blood and muscle. Medical literature indicates that the amount of blood found at the initial stage of a bone fracture decreases as bone regeneration takes place towards the healed state. The rate of change of the 21 of the implanted monopoles over time was shown to provide a tool that allowed the estimation of the amount of blood (hematoma) inside any bone fracture. In this thesis it has been shown that as the effective dielectric properties of the investigated fractured area shifted from the dielectric properties of blood towards the properties of bone, the 21 of the monopoles increased, thus, this technique can be used to indicate bone healing. The simulated results were validated in measurements using several multi-material phantoms and a real lamb joint. Finally, an analytical model on the approximation of the 21 of the monopoles in the near field inside the multi-material phantoms was developed. The results showed good agreement over the frequency spectrum of 1 to 4GHz and reasonable agreement over the parametric investigation of separation distance between them for the range of 1 to 7cm. This will potentially allow the application of the proposed technique for special types of fractures where the screws of the external fixation are separated by different distances

Development of piezoresistive sensors for biomedical applications

Tese de doutoramento em Engenharia Electrónica Industrial e de ComputadoresIn the last decades there has been an increase in sensing systems applied in a variety of situations with a large variety of sensor ranges. This represents a growing area with high potential. One of the areas of sensor development that require a great deal of attention is the area of sensor for biomedical applications and biosensors. These sensors have to overcome a number of challenges and limitations inherent to the environment where they are introduced. These difficulties lead to the necessity of using new materials and new techniques for their construction together with the more traditional materials, e.g. silicon based, which have already proven their potential in this area. Among the various materials, polymers have proven to be a good choice, due to a set of advantages such as simple processing, flexibility and facility of being obtained in different shapes. Therefore it is interesting to fabricate polymer based piezoresistive sensors for functional coatings of implantable hip prosthesis. These sensors will allow coating the prosthesis and provide new functionalities to the implants such as the possibility to measure forces and deformations between the prosthesis and the bone and therefore improving the postoperative diagnostic. In this works, a model of hip prosthesis with coated sensors was developed. For this purpose, flexible piezoresistive sensors have been developed that allow being implanted. Strain sensors were fabricated based on thin films of n+-nc-si.H by the technique of hot-wire chemical vapor deposition at a temperature of 150 ºC on a polymeric substrate, using the lithographic technique to construct the various layers of the sensors. The sensor has a gauge factor of -28 for low frequency deformation cycles. In the last decades there has been an increase in sensing systems applied in a variety of situations with a large variety of sensor ranges. This represents a growing area with high potential. One of the areas of sensor development that require a great deal of attention is the area of sensor for biomedical applications and biosensors. These sensors have to overcome a number of challenges and limitations inherent to the environment where they are introduced. These difficulties lead to the necessity of using new materials and new techniques for their construction together with the more traditional materials, e.g. silicon based, which have already proven their potential in this area. Among the various materials, polymers have proven to be a good choice, due to a set of advantages such as simple processing, flexibility and facility of being obtained in different shapes. Therefore it is interesting to fabricate polymer based piezoresistive sensors for functional coatings of implantable hip prosthesis. These sensors will allow coating the prosthesis and provide new functionalities to the implants such as the possibility to measure forces and deformations between the prosthesis and the bone and therefore improving the postoperative diagnostic. In this works, a model of hip prosthesis with coated sensors was developed. For this purpose, flexible piezoresistive sensors have been developed that allow being implanted. Strain sensors were fabricated based on thin films of n+-nc-si.H by the technique of hot-wire chemical vapor deposition at a temperature of 150 ºC on a polymeric substrate, using the lithographic technique to construct the various layers of the sensors. The sensor has a gauge factor of -28 for low frequency deformation cycles.In the last decades there has been an increase in sensing systems applied in a variety of situations with a large variety of sensor ranges. This represents a growing area with high potential. One of the areas of sensor development that require a great deal of attention is the area of sensor for biomedical applications and biosensors. These sensors have to overcome a number of challenges and limitations inherent to the environment where they are introduced. These difficulties lead to the necessity of using new materials and new techniques for their construction together with the more traditional materials, e.g. silicon based, which have already proven their potential in this area. Among the various materials, polymers have proven to be a good choice, due to a set of advantages such as simple processing, flexibility and facility of being obtained in different shapes. Therefore it is interesting to fabricate polymer based piezoresistive sensors for functional coatings of implantable hip prosthesis. These sensors will allow coating the prosthesis and provide new functionalities to the implants such as the possibility to measure forces and deformations between the prosthesis and the bone and therefore improving the postoperative diagnostic. In this works, a model of hip prosthesis with coated sensors was developed. For this purpose, flexible piezoresistive sensors have been developed that allow being implanted. Strain sensors were fabricated based on thin films of n+-nc-si.H by the technique of hot-wire chemical vapor deposition at a temperature of 150 ºC on a polymeric substrate, using the lithographic technique to construct the various layers of the sensors. The sensor has a gauge factor of -28 for low frequency deformation cycles. Sensors with larger flexibility were also developed though inkjet printing technique. Various configurations and materials were used to evaluate which materials are most appropriate for these types of sensors. Sensors with a gauge factor of approximately 2.5 for an active layer of PeDOT were obtained. A sensor matrix of 4 x 5 sensors was fabricated with an active area of 1.8 x 1.5 mm2 per sensor. These sensors were subjected to a set of electromechanical tests to evaluate its performance in situations close to end use. So the prosthesis was coated with the various sensors, cemented and subjected to deformation cycles for three levels of force according to standard ISO7206. An adaptive system read-out electronic circuit was developed and built that allows reading piezoresistive sensors with different characteristics. This system allows measuring a matrix of 8x8 sensors, but can be scaled to a large number of sensors. The readable range of the system is between 50 Ω and 100 kΩ according to the needs of the sensors being implanted. The total area of the circuit is 135 mm2, according to the requirements of a circuit to be used in in-vivo applications. An energy management system was also implemented that allows to activate and deactivate parts of the circuit when they are not needed, reducing the energy consumption. The system was validated by measuring a matrix of sensors with different characteristics. Finally, simulations were performed in order to evaluate the best options for the development of a wireless communications system. Three possible operation frequency ranges were used for three types of standard antennas. The communication system was introduced into a model simulating the characteristics of the various layers that constitute the human body. These simulations allow evaluate the frequency range most appropriate for implantable devices, the most appropriate antenna and the best location within the body. So the frequency chosen for the implementation was 868 Mhz for a Inverted- F antenna (IFA). In conclusion, the key elements for the implementations of an instrumented hip prosthesis were development and validated. The developed and/or simulated elements, including sensors, circuits for reading and communication system can also be used in other applications due to characteristics.These simulations allow evaluate the frequency range most appropriate for implantable devices, the most appropriate antenna and the best location within the body. So the frequency chosen for the implementation was 868 Mhz for a Inverted- F antenna (IFA). In conclusion, the key elements for the implementations of an instrumented hip prosthesis were development and validated. The developed and/or simulated elements, including sensors, circuits for reading and communication system can also be used in other applications due to characteristics. Neste trabalho foi desenvolvido um modelo de prótese de anca com implementação de sensores. Para atingir esse objectivo, foram desenvolvidos sensores piezoresitivos flexíveis que permitam ser implantados. Assim foram fabricados sensores de deformação baseados em filmes finos de n+-nc-si.H pela técnica de hot-wire chemical vapor deposition a uma temperatura de 150ºC sobre um substrato polimérico. Recorreu-se a técnica de litografia para construir as várias camadas do sensor. Os sensores apresentam um gauge factor de -28, para ciclos de baixa frequência em testes de four-point-bending. Foram ainda desenvolvidos sensores com uma maior flexibilidade através da técnica de inkjet printing. Para esse desenvolvimento foram usadas várias configurações e materiais, para avaliar quais os materiais mais adequados para este tipo de sensores. Na caracterização destes sensores obteve-se um gauge factor de aproximadamente 2.5 para uma camada ativa de PeDOT. Com os melhores sensores obtidos foram construídas matrizes de 4 x 5 sensores que apresentam uma área ativa de 1.8 x 1.5mm2 por sensor. Estes sensores foram sujeitos a um conjunto de ensaios electromecânicos, para avaliar o seu desempenho em situações próximas da utilização final. Desta forma foi revestida uma prótese com os diferentes sensores, cimentada e sujeita a ciclos de deformação para três níveis de força, segundo a norma ISO7206. Foi desenvolvido e construído um sistema de leitura adaptável que permite medir sensores piezoresistivos com diferentes características entre eles. Este sistema permite medir uma matriz de 8x8 sensores, mas pode ser escalada para um número maior de sensores. A gama de leitura do sistema varia entre 50 Ω e 100 kΩ, de acordo com as necessidades dos sensores a serem implementados. A área total deste circuito é de 135 mm2, de acordo com as necessidades de um circuito a ser utilizado em aplicações in-vivo. Foi também implementado um sistema de gestão de energia que permite ativar e desativar partes do circuito quando estas não são necessárias, permitindo, desta forma, reduzir os consumos de energia. O sistema foi validado através da medição de uma matriz de sensores com diferentes características. foram realizadas simulações de forma a avaliar as melhores opções para o desenvolvimento do sistema de comunicação sem fios. Foram usadas três possíveis gamas de frequência de operação para três tipos de antenas standard. O sistema de comunicação foi introduzido num modelo simulando as características das várias camadas que constituem o corpo humano. Estas simulações permitem aferir a gama de frequências mais adequadas para os dispositivos implantáveis, a antena mais adequada e a sua melhor localização, pois foi verificado como as várias camadas que constituem o corpo humano influenciam a comunicação. Assim, a frequência escolhida para a implementação foi de 868 MHz e a antena foi a IFA. Em conclusão, os elementos principais para a implementação de uma prótese de anca instrumentada, foram desenvolvidos e validados. Os elementos desenvolvidos e/ou simulados, incluindo os sensores, circuitos de leitura e sistema de comunicação, poderão igualmente ser utilizados em outras aplicações devido às suas boas características

Conformal antenna-based wireless telemetry system for capsule endoscopy

Capsule endoscopy for imaging the gastrointestinal tract is an innovative tool for carrying out medical diagnosis and therapy. Additional modalities beyond optical imaging would enhance current capabilities at the expense of denser integration, due to the limited space available within the capsule. We therefore need new designs and technologies to increase the smartness of the capsules for a given volume. This thesis presents the design, manufacture and performance characterisation of a helical antenna placed conformally outside an endoscopic capsule, and the characterisation in-silico, in-vitro and in-vivo of the telemetry system in alive and euthanised pigs. This method does not use the internal volume of the capsule, but does use an extra coating to protect the antenna from the surrounding tissue and maintain biocompatibility for safe use inside the human body. The helical antenna, radiating at 433 MHz with a bandwidth of 20 MHz within a muscle-type tissue, presents a low gain and efficiency, which is typical for implantable and ingestible medical devices. Telemetry capsule prototypes were simulated, manufactured and assembled with the necessary internal electronics, including a commercially available transceiver unit. Thermistors were embedded into each capsule shell, to record any temperature increase in the tissue surrounding the antenna during the experiments. A temperature increase of less than 1°C was detected for the tissue surrounding the antenna. The process of coating the biocompatible insulation layer over the full length of the capsule is described in detail. Data transmission programmes were established to send programmed data packets to an external receiver. The prototypes radiated at different power levels ranging from -10 to 10 dBm, and all capsules demonstrated a satisfactory performance at a data rate of 16 kbps during phantom and in-vivo experiments. Data transmission was achieved with low bit-error rates below 10-5. A low signal strength of only -54 dBm still provided effective data transfer, irrespective of the orientation and location of the capsule, and this successfully demonstrated the feasibility of the system

Design and implementation of miniaturised capsule for autofluorescence detection with possible application to the bowel disease

Early signs of intestinal cancer may be detected through variations in tissue autofluorescence (AF), however current endoscope-based AF systems are unable to inspect the small intestine. This thesis describes the design, fabrication, implantation, testing and packaging of a wireless pill capable of detecting the autofluorescence from cancerous cells, and able to reach parts of the gastrointestinal tract that are inaccessible to endoscopes. The pill exploits the fact that there is a significant difference in the intensity of autofluorescence emitted by normal and cancerous tissues when excited by a blue or ultra violet light source. The intensity differences are detected using very sensitive light detectors. The pill has been developed in two stages. The first stage starts with using an off-chip multi-pixel photon counter (MPPC) device as a light detector. In the second stage, the light detector is integrated into an application specific integrated circuit (ASIC). The pill comprises of an ASIC, optical filters, an information processing unit and a radio transmission unit, to transmit acquired data to an external base station. Two ASICs have been fabricated, the first stage of this work involved implementing an ASIC that contains two main blocks; the first block is capable of providing a variable DC voltage more than 72 V from a 3 V input to bias the MPPC device. The second main block is a front-end consisting of a high speed transimpedance amplifier (TIA) and voltage amplifiers to capture the very small current pulses produced by the MPPC. The second ASIC contains a high voltage charge pump up to (37.9 V) integrated with a single photon avalanche detector (SPAD). The charge pump is used to bias the SPAD above its breakdown voltage and therefore operate the device in Geiger mode. The SPAD was designed to operate in the visible region where its photon detection efficiency (PDE) peaks at 465 nm, which is near to human tissues autofluorescence peaking region (520±10 nm). The use of the ultra low light detector to detect the autofluorescence permits a lower excitation light intensity and therefore lower overall power consumption. The two ASICs were fabricated using a commercial triple-well high-voltage CMOS process. The complete device operates at 3V and draws an average of 7.1mA, enabling up to 23 hours of continuous operation from two 165mAh SR44 batteries

Conception d'antennes de communication à travers le corps humain pour le suivi thérapeutique

Avec le développement rapide des technologies sans fil modernes et la miniaturisation des antennes et des systèmes électriques, l'emploi des antennes à l'intérieur du corps humain pour le suivi thérapeutique est devenu possible. Des batteries permettent d'alimenter ces antennes ; la réduction de la consommation de puissance implique l'augmentation de la durée de vie de circuits ingérables. Le corps humain, qui a une conductivité non nulle, n'est pas un milieu idéal pour la transmission des ondes RF à cause de l'atténuation liée aux propriétés diélectriques des tissus biologiques. Cependant, les tissus humains ne perturbent pas le champ magnétique car celui-ci dépend de la perméabilité du milieu qui est égale à un dans le corps humain. Bien que la puissance du champ magnétique décroisse avec l'exposant six de la distance, la technique utilisant les communications par induction magnétique en champ proche a été adoptée dans cette étude pour concevoir une liaison sans fil à faible portée à travers le corps humain. Durant ces travaux de thèse, après une caractérisation détaillée de la bobine d'émission située à l'intérieur du corps humain et de la bobine de réception localisée à sa surface, nous avons mis en place un bilan de liaison pour contribuer à l'amélioration du transfert de puissance dans ce milieu dissipatif. Un modèle analytique, déterminant les facteurs qui peuvent affecter le bilan de liaison par induction magnétique, a été vérifié à travers les simulations et les mesures. La variation de la position et de l'orientation de l'antenne ingérable ont été prises en compte pour évaluer la réponse de couplage entre la bobine émettrice et la bobine réceptrice. Les résultats obtenus constituent un pas en avant vers de futures recherches sur la conception de antennes dans les milieux dissipatifs et en particulier le corps humainWith the rapid growth of wireless technology and the miniaturization of modern antennas and electrical systems, the use of antennas inside the human body for therapeutic monitoring became possible. Batteries are used to supply these antennas; reducing the power consumption allows to increase the lifetime of ingestible systems. The human body, which has non-zero conductivity, is not an ideal environment for the transmission of RF waves because of the attenuation due to the dielectric properties of biological tissues. However, the human tissues do not disrupt the magnetic field as it depends on the permeability of the medium which is equal to one in the human body. Although the magnetic field power decreases with the distance exponent six, the technique using near-field magnetic induction communications was adopted in this study to design a short range wireless link through the human body. In this thesis, after a detailed characterization of the transmitting coil antenna located inside the human body and the receiving coil placed on its surface, we have implemented a link budget to contribute to the improvement of power transfer in the dissipative medium. An analytical model, identifying factors that can affect the link budget by magnetic induction, has been verified through simulations and measurements. The variation of the position and the orientation of the ingestible antenna were taken into account to evaluate the coupling response between the transmitting coil and the receiving coil. The results are a step toward future research on the design of antennas in dissipative media, in particular the human bodyPARIS-EST-Université (770839901) / SudocSudocFranceF