Dielectric Characterization of Biological Tissues for Medical Applications

[ES] Conocer las propiedades electromagnéticas de los tejidos biológicos con la mayor exactitud posible tiene una gran importancia en el diseño de un elevado número de aplicaciones biomédicas. El diseño de dispositivos médicos inalámbricos, antenas superficiales e intracorporales, evaluación de tasas de absorción electromagnética, técnicas de tratamiento y detección de cáncer como la hipertermia e imágenes médicas son ejemplos de aplicaciones que requieren esta información para su desarrollo. Debido a que el cáncer provoca modificaciones estructurales en las células que a su vez generan cambios en las propiedades electromagnéticas, es posible desarrollar aplicaciones de detección de cáncer que se basen en este hecho. Un objetivo potencial es el cáncer de colon (CRC), debido a que los tejidos de colon sospechosos son accesibles de forma más o menos sencilla durante procedimientos endoscópicos. Este tipo de cáncer es uno de los más extendidos, siendo responsable de aproximadamente el 10% de casos y muertes totales. Existe un gran número de factores de riesgo que pueden explicar la aparición de la enfermedad, aunque esencialmente la probabilidad se incrementa significativamente con el aumento de la edad de la población. Los programas de cribado sobre la población son críticos: si el cáncer se detecta en etapas tempranas, la probabilidad de sobrevivir se incrementa en gran medida, y además se reducen los costes asociados. Uno de los objetivos principales de esta tesis es proponer aplicaciones que ayuden en la detección de CRC durante la colonoscopia haciendo uso de las diferencias en las propiedades electromagnéticas. Aparte de mejoras en el diagnóstico, complementar la colonoscopia puede conllevar otros beneficios colaterales como una reducción en la carga de anatomía patológica. Para demostrar la viabilidad y el potencial desarrollo futuro de estas aplicaciones, en esta tesis se miden y se trata de encontrar diferencias entre las propiedades electromagnéticas de tejidos sanos, cancerosos y patológicos de colon humano. Las medidas han sido llevadas a cabo mediante la técnica del coaxial terminado en abierto. Con el propósito de incrementar la precisión del método, se ha evaluado el principio de funcionamiento y se ha mejorado el proceso de calibración. Dos fuentes de tejido de colon han sido analizadas en esta tesis: tejidos procedentes de colonoscopias (biopsias) y tejidos obtenidos a partir de procedimientos quirúrgicos. Aparte de tejido sano, se estudian las siguientes patologías: Adenocarcinomas (CRC), adenomas sin displasia, adenomas con bajo grado de displasia, adenomas con alto grado de displasia, hiperplasias y hamartomas. Debido a la alta variabilidad entre distintos sujetos, las propiedades electromagnéticas de los tejidos sospechosos de un paciente en concreto deben ser siempre comparadas con las propiedades de sus tejidos sanos, no evaluadas de forma independiente. El segundo gran objetivo de esta tesis es el desarrollo de una nueva base de datos de las propiedades electromagnéticas de tejidos biológicos medidas in vivo. Ahora mismo, las colecciones disponibles están limitadas en número de tejidos o frecuencias caracterizadas, obligando a los investigadores a escoger bases de datos más completas pero realizadas ex vivo. No obstante, usar este tipo de colecciones tienen fuentes de incertidumbre adicionales dado que las medidas están condicionadas por la deshidratación de los tejidos y la perdida de flujo sanguíneo. El desarrollo de esta nueva base de datos puede facilitar el diseño de aplicaciones que requieran conocer las propiedades electromagnéticas con alto grado de precisión.[CA] Conéixer les propietats electromagnètiques dels teixits biològics amb la major exactitud possible té una gran importància en el disseny d'un gran nombre d'aplicacions biomèdiques. El disseny de dispositius metges sense fil, antenes superficials i intracorporales, l'avaluació de taxes d'absorció electromagnètica, tècniques de tractament i detecció de càncer com ara la hipertèrmia i imatges mediques són exemples d'aplicacions que requerixen esta informació. Com el càncer provoca modificacions estructurals en les cèl·lules que generen canvis en les propietats electromagnètiques, es possible desenrotllar aplicacions de detecció de càncer que es basen en este fet. Un objectiu potencial és el càncer de colon (CRC), pel fet que els teixits de colon sospitosos són accessibles de forma més o menys senzilla durant procediments endoscòpics. Este tipus de càncer és un dels més estesos, sent responsable d'aproximadament el 10% de casos i morts totals. N'hi ha un gran nombre de factors de risc que poden explicar l'aparició de la malaltia, encara que en resum la probabilitat s'incrementa significativament amb l'augment de l'edat de la població. Els programes de cribratge sobre la població són crítics. Si el càncer es detecta en etapes primerenques, la probabilitat de sobreviure s'incrementa en gran manera, i a més es reduïxen els costos associats. Un dels objectius principals d'esta tesi és proposar aplicacions que ajuden en la detecció de CRC durant la colonoscòpia fent ús de les diferències en les propietats electromagnètiques. A banda de millores en el diagnòstic, complementar la colonoscòpia pot comportar altres beneficis col·laterals com una reducció en la càrrega d'anatomia patològica. Per a demostrar la fiabilitat i el potencial desenrotllament d'aquestes aplicacions, en aquesta tesi es mesuren i es tracta de trobar diferències entre les propietats electromagnètiques de teixits sans, cancerosos i patològics de colon humà. Les mesures han sigut realitzades mitjançant la tècnica del coaxial acabat en obert. Amb el propòsit d'incrementar la precisió del mètode, s'ha avaluat el seu principi de funcionament i s'ha millorat el procés de calibratge. Dos fonts de teixit de colon s'han analitzat en aquesta tesi: teixits procedents de colonoscòpies (biòpsies) i teixits obtinguts a partir de procediments quirúrgics. Apart de teixit sà, s'estudien els següents teixits: Adenocarcinomes (CRC), adenomes sense displàsia, adenomes amb baix grau de displàsia, adenomes amb alt grau de displàsia, hiperplàsies y hamartomes. Degut a l'alta variabilitat entre diferents subjectes, les propietats electromagnètiques dels teixits sospitosos d'un pacient en particular han de ser comparades amb les propietats dels seus teixits sans, no avaluats independentment. El segon gran objectiu d'esta tesi és el desenrotllament d'una nova base de dades de les propietats electromagnètiques de teixits biològics mesurades in vivo. Ara mateix, les col·leccions disponibles estan limitades en nombre de teixits o freqüències caracteritzades, obligant els investigadors a triar bases de dades més completes però realitzades ex vivo. No obstant això, este tipus de col·leccions te fonts d'incertesa addicionals atés que les mesures estan condicionades per la deshidratació dels teixits i la pèrdua de flux sanguini. El desenrotllament d'esta nova base de dades pot facilitar el disseny d'aplicacions que requerisquen conéixer les propietats electromagnètiques amb alt grau de precisió.[EN] Nowadays, a careful knowledge of the electromagnetic properties of biological tissues is required for developing a great number of applications. The development of wireless medical devices, the design of in-body and on-body antennas, specific absorption rate evaluations, cancer treatment techniques such as hyperthermia and detection techniques like medical imaging are some examples of applications that rely on these data. Since cancer causes modifications on the biological structure of cells that can lead in turn to changes in the electromagnetic properties of the tissues, it is possible to develop novel detection applications taking advantage of it. One potential target is colorectal cancer (CRC), as suspicious tissues can be accessed quite easily through colonoscopy procedures. This kind of cancer is one of the most spread kinds, being responsible of about 1 out of 10 new cancer cases and deaths. There are several risk factors currently related to the apprising of this cancer, although in essence the higher the age of the population, the higher the incidence of CRC. Screening programs are key for detecting and diagnosing cancer: if found at early stages, the probability of survival increases greatly, and the cost of the treatment can be reduced as well. One of the major objectives of this dissertation is proposing applications for detecting CRC that aid in the colonoscopy procedures by making use of the differences in electromagnetic properties. Aside from enhancement in the diagnosis of CRC, improving the colonoscopy procedure can lead to collateral benefits like a lowering of the burden of anatomical pathology unit. With the aim at demonstrating the feasibility and the potential future development of these applications, in the framework of this thesis the dielectric properties of healthy, cancerous and pathological human colon tissues are measured and compared in order to find electromagnetic differences. Measurements are carried out by means of an open-ended coaxial system. Its principle of operation has been revisited with the aim at maximizing the accuracy of the method, and the calibration procedure has been optimized serving the same purpose. Two main sources of colon tissue have been analyzed: samples from colonoscopy biopsies and samples from surgery resections. Besides healthy tissue, the following colon tissues have been characterized: Adenocarcinomas (CRC), adenomas without dysplasia, adenomas with low-grade dysplasia, adenomas with high-grade dysplasia, hyperplastic polyps and hamartomatous polyps. Given the variability that can appear among subjects, the electromagnetic properties of suspicious tissues from a particular patient have to be always compared with those of his healthy ones, not evaluated independently. The second major objective of this thesis involves the development of a new database of electromagnetic properties of biological tissues obtained at in vivo conditions. Nowadays, the available collections are limited either in the number of tissues or the measured frequencies, and hence researchers have to make use of more complete databases but that were performed ex vivo. The drawback of using these collections is that results can be compromised by factors such as lack of blood perfusion and tissue dehydration. Developing this new database can facilitate the design of applications that needs of a careful knowledge of these properties.Fornés Leal, A. (2019). Dielectric Characterization of Biological Tissues for Medical Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/132188TESI

Caracterización del canal radio en entornos especiales

En el presente proyecto se estudia el canal radio en dos casos especiales de Redes Inalámbricas de Área Personal (WPAN). El primero de los casos es la transmisión durante un incendio indoor. El objetivo es caracterizar el canal en la banda UWB (Banda Ultra-Ancha, por sus siglas en inglés) para averiguar si se producen pérdidas adicionales a las de espacio libre debidas al fuego, y con ello conocer en una primera aproximación si la implantación de nuevos sistemas para mejorar la seguridad de los bomberos es factible. El segundo caso a estudiar es la transmisión en Redes de Área Corporal (BAN), en concreto en un medio sintético que simula dieléctricamente un músculo humano. Se caracterizará el canal en las bandas UWB (3.1 a 10.6 GHz) e ISM (Industrial, Científica y Médica, por sus siglas en inglés, entorno a 2.4 GHz), y se obtendrán datos que podrían ser de ayuda de cara al diseño de futuros dispositivos en BAN.Fornés Leal, A. (2014). Caracterización del canal radio en entornos especiales. http://hdl.handle.net/10251/46612.Archivo delegad

Dielectric characterization of healthy and malignant colon tissues in the 0.5 18 GHz frequency band

Several reports over the last few decades have shown that the dielectric properties of healthy and malignant tissues of the same body organ usually show different values. However, no intensive dielectric studies of human colon tissue have been performed, despite colon cancer's being one of the most common types of cancer in the world. In order to provide information regarding this matter, a dielectric characterization of healthy and malignant colon tissues is presented. Measurements are performed on ex vivo surgery samples obtained from 20 patients, using an open-ended coaxial probe in the 0.5 18 GHz frequency band. Results show that the dielectric constant of colon cancerous tissue is 8.8% higher than that of healthy tissues (p = 0.002). Besides, conductivity is about 10.6% higher, but in this case measurements do not have statistical significance (p = 0.038). Performing an analysis per patient, the differences in dielectric constant between healthy and malignant tissues appear systematically. Particularized results for specific frequencies (500 MHz, 900 MHz, 2.45 GHz, 5 GHz, 8.5 GHz and 15 GHz) are also reported. The findings have potential application in early-stage cancer detection and diagnosis, and can be useful in developing new tools for hyperthermia treatments as well as creating electromagnetic models of healthy and cancerous tissues.The authors would like to thank the medical staff of the endoscopy unit of Hospital Universitari i Politecnic La Fe for their assistance in the gathering of tissue samples. This work was supported by Ministerio de Economia y Competitividad, Spain (ref. TEC2014-60258-C2-1-R, TEC2014-56469-REDT), by FEDER funds, and by a UPV-IISLaFe action (CEI-2G, 2014).Fornés Leal, A.; García Pardo, C.; Frasson, M.; Pons Beltrán, V.; Cardona Marcet, N. (2016). Dielectric characterization of healthy and malignant colon tissues in the 0.5 18 GHz frequency band. Physics in Medicine and Biology. 61(20):7334-7346. https://doi.org/10.1088/0031-9155/61/20/7334S73347346612

Tailor-Made Tissue Phantoms Based on Acetonitrile Solutions for Microwave Applications up to 18 GHz

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Tissue-equivalent phantoms play a key role in the development of new wireless communication devices that are tested on such phantoms prior to their commercialization. However, existing phantoms cover a small number of tissues and do not reproduce them accurately within wide frequency bands. This paper aims at enlarging the number of mimicked tissues as well as their working frequency band. Thus, a variety of potential compounds are scanned according to their relative permittivity from 0.5 to 18 GHz. Next, a combination of these compounds is characterized so the relation between their dielectric properties and composition is provided. Finally, taking advantage of the previous analysis, tailor-made phantoms are developed for different human tissues up to 18 GHz and particularized for the main current body area network (BAN) operating bands. The tailor-made phantoms presented here exhibit such a high accuracy as would allow researchers and manufacturers to test microwave devices at high frequencies for large bandwidths as well as the use of heterogeneous phantoms in the near future. The key to these phantoms lies in the incorporation of acetonitrile to aqueous solutions. Such compounds have a suitable behavior to achieve the relative permittivity values of body tissues within the studied frequency band.This work was supported by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R) and by the European FEDER Funds.Castelló-Palacios, S.; García Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2016). Tailor-Made Tissue Phantoms Based on Acetonitrile Solutions for Microwave Applications up to 18 GHz. IEEE Transactions on Microwave Theory and Techniques. 64(11):3987-3994. https://doi.org/10.1109/TMTT.2016.2608890S39873994641

Wideband phantoms of different body tissues for heterogeneous models in body area networks

[EN] One of the key issues about wireless technologies is their interaction with the human body. The so-called internet of things will comprise many devices that will transmit either around or through the human body. These devices must be tested either in their working medium, when possible, or in the most realistic one. For this purpose, tissue-like phantoms are the best alternative to carry out realistic analyses of the performance of body area networks. In addition, they are the conventional way to certify the compliance of commercial standards by these devices. However, the number of phantoms that work in large bandwidths is limited in literature. This work aims at presenting chemical solutions that will be useful to prepare a variety of wideband tissue phantoms. Besides, the colon was mimicked in two ways, the healthy tissue and the malignant one, taking into account studies that relate changes on the relative permittivity with cancer. They were designed on the basis of acetonitrile in aqueous solutions as described in a previous work. Thus, many scenarios could be developed such as multilayers which imitate parts of the heterogeneous body.Research supported by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) from Universitat Politècnica de València, by the Ministerio de Economía y Competitividad, Spain (TEC2014-60258-C2-1- R) and by the European FEDER Funds.Castelló-Palacios, S.; Garcia-Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2018). Wideband phantoms of different body tissues for heterogeneous models in body area networks. IEEE. 3032-3035. https://doi.org/10.1109/EMBC.2017.8037496S3032303

Accurate broadband measurement of electromagnetic tissue phantoms using open-ended coaxial systems

[EN] New technologies and devices for wireless communication networks are continually developed. In order to assess their performance, they have to be tested in realistic environments taking into account the influence of the body in wireless communications. Thus, the development of phantoms, which are synthetic materials that can emulate accurately the electromagnetic behaviour of different tissues, is mandatory. An accurate dielectric measurement of these phantoms requires using a measurement method with a low uncertainty. The open-ended coaxial technique is the most spread technique but its accuracy is strongly conditioned by the calibration procedure. A typical calibration is performed using an open circuit, a short circuit and water. However, this basic calibration is not the most accurate approach for measuring all kinds of materials. In this paper, an uncertainty analysis of the calibration process of open-ended coaxial characterization systems when a polar liquid is added to the typical calibration is provided. Measurements are performed on electromagnetically well-known liquids in the 0.5 - 8.5 GHz band. Results show that adding methanol improves the accuracy in the whole solution domain of the system, mainly when measuring phantoms that mimic high water content tissues, whereas ethanol is more suitable for measuring low water content tissue phantoms.This work was supported by the Ministerio de Educacion y Ciencia, Spain (ref. TEC2014-60258-C2-1-R, TEC2014-56469-REDT), by the European FEDER funds.Fornés Leal, A.; Garcia-Pardo, C.; Castelló-Palacios, S.; Vallés Lluch, A.; Cardona Marcet, N. (2007). Accurate broadband measurement of electromagnetic tissue phantoms using open-ended coaxial systems. IEEE. 32-36. https://doi.org/10.1109/ISMICT.2017.7891761S323

Formulas for easy-to-prepare tailored phantoms at 2.4 GHz ISM band

[EN] Emerging integration of communication networks into wearable or implantable body devices involves a challenge due to the transmitting medium, the body itself. This medium is heterogeneous and lossier than air, so devices that are supposed to work on it should be tested in tissue-equivalent materials. A number of materials with the electromagnetic response of body tissues have been proposed. Most of them are sucrose aqueous solutions that are supposed to simulate human's muscle tissue mainly within medical frequency bands. However, these recipes are restricted to a single tissue and it is difficult to adapt them to fit the permittivity values of different body tissues. The significance of this study lies in the development of a mathematical relationship that models the dielectric properties of an aqueous solution according to the concentration of sugar and salt at 2.4 GHz, the frequency around which an Industrial, Scientific and Medical (ISM) band is placed. Thus, it becomes possible to create custom-made phantoms with simple and accessible ingredients that are easy to prepare in any laboratory.This work was supported by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R) and by the European FEDER Funds.Castelló-Palacios, S.; Garcia-Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2017). Formulas for easy-to-prepare tailored phantoms at 2.4 GHz ISM band. IEEE. 27-31. https://doi.org/10.1109/ISMICT.2017.7891760S273

Spectrum Sharing for LTE-A and DTT: Field Trials of an Indoor LTE-A Femtocell in DVB-T2 Service Area

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.In this paper, we study a particular case which goes a step beyond the previous ones, as it aims at sharing the same frequency band in the same area between long term evolution-advance (LTE-A) and digital video broadcasting-terrestrial second generation (DVB-T2) technologies. Those geographical areas that are not covered because the useful DTT signal is obstructed by the environment or it has a limited coverage by the network design can be called micro-TVWS. We assume that a DVB-T2 transmitter provides coverage for fixed rooftop reception as a primary service, to a building in which a LTE-A femtocell is installed indoors for local coverage, as a secondary service. The results have been obtained by laboratory emulation and validated through field measurements using professional equipment. Our results provide the technical restrictions of the LTE-A femtocell, mainly on the maximum allowable effective isotropic radiated power that could transmit on the DTT band in terms of carrier separation, from co-channel to adjacent band. These results meet the need of spectrum for IMT-Advanced technologies, so spectrum sharing is proposed in this paper as a new solution to make an efficient use of this resource.This work was supported in part by the Ministerio de Educacion y Ciencia, Spain, under Grant "DEFINE5G" TEC2014-60258-C2-1-R and Grant "ARCO5G" TEC2014-56469-REDT, and in part by the European FEDER Funds.Martínez Pinzón, G.; Cardona Marcet, N.; García Pardo, C.; Fornés Leal, A.; Ribadeneira-Ramírez, JA. (2016). Spectrum Sharing for LTE-A and DTT: Field Trials of an Indoor LTE-A Femtocell in DVB-T2 Service Area. IEEE Transactions on Broadcasting. 62(3):552-561. https://doi.org/10.1109/TBC.2016.2582338S55256162

Gel Phantoms for Body Microwave Propagation in the (2 to 26.5) GHz Frequency Band

[EN] Tissue phantoms are widely used for assessing the interaction between the electromagnetic waves and the human body. These are especially key in body area networks, where the body itself acts as the propagation medium since transmission is highly influenced by its diverse dielectric properties. Gels are suitable materials because of their high water content, which is required to mimic the dielectric properties of most tissues. In this paper, PHEA gels are suggested for achieving those properties due to their synthetic nature, which gives them the possibility to be swollen reversibly in more types of mixtures, in addition to water. These gels can be tailored to control the amount of liquid they embed so that they can imitate different body tissues in a wide bandwidth (2¿26.5 GHz), which includes most of the current mobile communication and medical bands. This versatility offers the chance to create heterogeneous models of particular regions of the body, and thus improve the test realism. In addition, they own better mechanical and stability properties than the widely used agar or gelatin.This work was supported in part by the Universitat Politecnica de Valencia-Institut d'Investigacio Sanitaria La Fe (UPV-IIS La Fe) Program [Early Stage Colon Tumour Diagnosis by Electromagnetic Reflection (STuDER), 2016 and Electromagnetic Probe for Early Tumour Detection (EMOTE), 2017], in part by the Universitat Politecnica de Valencia through the Programa de Ayudas de Investigacion y Desarrollo under Grant PAID-01-16, and in part by the European Union's H2020: MSCA: ITN Program for the "mmWave Communications in the Built Environments - WaveComBE" Project under Grant 766231.Castelló-Palacios, S.; Garcia-Pardo, C.; Alloza-Pascual, M.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2019). Gel Phantoms for Body Microwave Propagation in the (2 to 26.5) GHz Frequency Band. IEEE Transactions on Antennas and Propagation. 67(10):6564-6573. https://doi.org/10.1109/TAP.2019.2920293S65646573671

Spatial In-Body Channel Characterization Using an Accurate UWB Phantom

"(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works."Ultra-wideband (UWB) systems have emerged as a possible solution for future wireless in-body communications. However, in-body channel characterization is complex. Animal experimentation is usually restricted. Furthermore, software simulations can be expensive and imply a high computational cost. Synthetic chemical solutions, known as phantoms, can be used to solve this issue. However, achieving a reliable UWB phantom can be challenging since UWB systems use a large bandwidth and the relative permittivity of human tissues are frequency dependent. In this paper, a measurement campaign within 3.1-8.5 GHz using a new UWB phantom is performed. Currently, this phantom achieves the best known approximation to the permittivity of human muscle in the whole UWB band. Measurements were performed in different spatial positions, in order to also investigate the diversity of the in-body channel in the spatial domain. Two experimental in-body to in-body (IB2IB) and in-body to on-body (IB2OB) scenarios are considered. From the measurements, new path loss models are obtained. Besides, the correlation in transmission and reception is computed for both scenarios. Our results show a highly uncorrelated channel in transmission for the IB2IB scenario at all locations. Nevertheless, for the IB2OB scenario, the correlation varies depending on the position of the receiver and transmitter.This work was supported by the Ministerio de Economia y Competitividad, Spain, under Grant TEC2014-60258-C2-1-R and Grant TEC2014-56469-REDT and by the European FEDER Funds.Andreu Estellés, C.; Castelló Palacios, S.; García Pardo, C.; Fornés Leal, A.; Vallés Lluch, A.; Cardona Marcet, N. (2016). Spatial In-Body Channel Characterization Using an Accurate UWB Phantom. IEEE Transactions on Microwave Theory and Techniques. 64(11):3995-4002. doi:10.1109/TMTT.2016.2609409S39954002641