Electromagnetic device for axillary Lymph Node diagnosis

The diagnosis of axillary lymph nodes (ALNs) is fundamental to determine breast cancer staging before making therapeutical decisions. Non-invasive medical imaging techniques are often used to diagnose ALNs, but they lack sensitivity and specificity. This thesis aims to contribute to the development of microwave imaging (MWI) prototype system to detect and diagnose ALNs. The dielectric properties of freshly excised animal lymph nodes (LNs) and human ALNs are measured (0.5-8.5GHz) with the Open-Ended Coaxial-Probe technique. The results show that the relative permittivity of healthy ALNs ranges between 30 and 50 at 4.5GHz, which contrasts well with the surrounding fat tissue, potentially enabling ALN detection with MWI. Additionally, the effects of freezing and defrosting of biological tissue dielectric properties are studied, which is motivated by the possibility of measuring previously frozen and defrosted LNs. The results suggest that measuring defrosted tissues does not affect the estimation of their dielectric properties by more than 9% at 4.5GHz, paving the way to measure previously frozen LN. The measured ALN dielectric properties are used to develop an anatomically realistic axillary phantom. The phantom derives from the segmentation of a thoracic computed-tomography scan, and it is made of polymeric containers filled with appropriate tissue mimicking liquids, representing fat and muscle. Finally, ALN microwave tomography is tested (0.5-2.5GHz) on the developed anthropomorphic phantom, using the distorted Born iterative method. The numerical results show that: (i) prior knowledge on the position of muscle tissue is fundamental for ALN detection; (ii) performing two-step measurements, with the antenna set in two different angular positions, can increase the amount of retrievable information, and enhance imaging results. Regarding experimental results, the proposed system can detect an ALN in different positions in the axillary region, which motivates further studies on ALN MWI

HF-VHF帯における生体等価ファントムを用いた電磁波と人体相互作用の検証

研究科: 千葉大学大学院工学研究科学位:千大院工博甲第工185号博士(工学)千葉大

Microwave Imaging to Improve Breast Cancer Diagnosis

Breast cancer is the most prevalent type of cancer worldwide. The correct diagnosis of Axillary Lymph Nodes (ALNs) is important for an accurate staging of breast cancer. The performance of current imaging modalities for both breast cancer detection and staging is still unsatisfactory. Microwave Imaging (MWI) has been studied to aid breast cancer diagnosis. This thesis addresses several novel aspects of the development of air-operated MWI systems for both breast cancer detection and staging. Firstly, refraction effects in air-operated setups are evaluated to understand whether refraction calculation should be included in image reconstruction algorithms. Then, the research completed towards the development of a MWI system to detect the ALNs is presented. Anthropomorphic numerical phantoms of the axillary region are created, and the dielectric properties of ALNs are estimated from Magnetic Resonance Imaging exams. The first pre-clinical MWI setup tailored to detect ALNs is numerically and experimentally tested. To complement MWI results, the feasibility of using machine learning algorithms to classify healthy and metastasised ALNs using microwave signals is analysed. Finally, an additional study towards breast cancer detection is presented by proposing a prototype which uses a focal system to focus the energy into the breast and decrease the coupling between antennas. The results show refraction calculation may be neglected in low to moderate permittivity media. Moreover, MWI has the potential as an imaging technique to assess ALN diagnosis as estimation of dielectric properties indicate there is sufficient contrast between healthy and metastasised ALNs, and the imaging results obtained in this thesis are promising for ALN detection. The performance of classification models shows these models may potentially give complementary information to imaging results. The proposed breast imaging prototype also shows promising results for breast cancer detection

Quality assurance guidelines for superficial hyperthermia clinical trials: II. Technical requirements for heating devices

Quality assurance (QA) guidelines are essential to provide uniform execution of clinical trials with uniform quality hyperthermia treatments. This document outlines the requirements for appropriate QA of all current superficial heating equipment including electromagnetic (radiative and capacitive), ultrasound, and infrared heating techniques. Detailed instructions are provided how to characterize and document the performance of these hyperthermia applicators in order to apply reproducible hyperthermia treatments of uniform high quality. Earlier documents used specific absorption rate (SAR) to define and characterize applicator performance. In these QA guidelines, temperature rise is the leading parameter for characterization of applicator performance. The intention of this approach is that characterization can be achieved with affordable equipment and easy-to-implement procedures. These characteristics are essential to establish for each individual applicator the specific maximum size and depth of tumors that can be heated adequately. The guidelines in this document are supplemented with a second set of guidelines focusing on the clinical application. Both sets of guidelines were developed by the European Society for Hyperthermic Oncology (ESHO) Technical Committee with participation of senior Society of Thermal Medicine (STM) members and members of the Atzelsberg Circle

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

Design and Simulation of Coils for High Field Magnetic Resonance Imaging and Spectroscopy

The growing availability of high-field magnetic resonance (MR) scanners has reignited interest in the in vivo investigation of metabolics in the body. In particular, multinuclear MR spectroscopy (MRS) data reveal physiological details inaccessible to typical proton (1H) scans. Carbon-13 (13C) MRS studies draw considerable appeal owing to the enhanced chemical shift range of metabolites that may be interrogated to elucidate disease metabolism and progression. To achieve the theoretical signal-to-noise (SNR) gains at high B0 fields, however, J-coupling from 1H-13C chemical bonds must be mitigated by transmitting radiofrequency (RF) proton-decoupling pulses. This irradiated RF power is substantial and intensifies with increased decoupling bandwidth as well as B0 field strength. The preferred 13C MRS experiment, applying broadband proton decoupling, thus presents considerable challenges at 7 T. Localized tissue heating is a paramount concern for all high-field studies, with strict Specific Absorption Rate (SAR) limits in place to ensure patient safety. Transmit coils must operate within these power guidelines without sacrificing image and spectral quality. Consequently, RF coils transmitting proton-decoupling pulses must be expressly designed for power efficiency as well as B1 field homogeneity. This dissertation presents innovations in high-field RF coil development that collectively improved the homogeneity, efficiency, and safety of high field 13C MRS. A review of electromagnetic (EM) theory guided a full-wave modeling study of coplanar shielding geometries to delineate design parameters for coil transmit efficiency. Next, a novel RF coil technique for achieving B1 homogeneity, dubbed forced current excitation (FCE), was examined and a coplanar-shielded FCE coil was implemented for proton decoupling of the breast at 7 T. To perform a series of simulation studies gauging SAR in the prone breast, software was developed to fuse a suite of anatomically-derived heterogeneous breast phantoms, spanning the standard four tissue density classifications, with existing whole-body voxel models. The effects of tissue density on SAR were presented and guidance for simulating the worst-case scenario was outlined. Finally, for improving capabilities of multinuclear coils during proton coil transmit, a high-power trap circuit was designed and tested, ultimately enabling isolation of 13C coil elements during broadband proton decoupling pulses. Together, this work advanced the hardware capabilities of high-field multinuclear spectroscopy with immediate applicability for performing broadband proton-decoupled 13C MRS in the breast at 7 T

Thermal dosimetry for bladder hyperthermia treatment. An overview.

The urinary bladder is a fluid-filled organ. This makes, on the one hand, the internal surface of the bladder wall relatively easy to heat and ensures in most cases a relatively homogeneous temperature distribution; on the other hand the variable volume, organ motion, and moving fluid cause artefacts for most non-invasive thermometry methods, and require additional efforts in planning accurate thermal treatment of bladder cancer. We give an overview of the thermometry methods currently used and investigated for hyperthermia treatments of bladder cancer, and discuss their advantages and disadvantages within the context of the specific disease (muscle-invasive or non-muscle-invasive bladder cancer) and the heating technique used. The role of treatment simulation to determine the thermal dose delivered is also discussed. Generally speaking, invasive measurement methods are more accurate than non-invasive methods, but provide more limited spatial information; therefore, a combination of both is desirable, preferably supplemented by simulations. Current efforts at research and clinical centres continue to improve non-invasive thermometry methods and the reliability of treatment planning and control software. Due to the challenges in measuring temperature across the non-stationary bladder wall and surrounding tissues, more research is needed to increase our knowledge about the penetration depth and typical heating pattern of the various hyperthermia devices, in order to further improve treatments. The ability to better determine the delivered thermal dose will enable clinicians to investigate the optimal treatment parameters, and consequentially, to give better controlled, thus even more reliable and effective, thermal treatments

Wideband Electromagnetic Body Phantoms for the Evaluation of Wireless Communications in the Microwave Spectrum

[ES] La constante evolución de la tecnología y la búsqueda de nuevas aplicaciones que mejoren la vida de las personas ha llevado a la incorporación de estas tecnologías en el organismo. Las redes inalámbricas de área corporal (WBAN) son un buen ejemplo de esto, que consisten en redes de comunicaciones ubicadas en el propio cuerpo, tanto en la superficie como implantadas en su interior mediante el uso de dispositivos inalámbricos. Estas redes utilizan el cuerpo humano como medio de transmisión, por lo que debe evaluarse la influencia del mismo sobre la propagación. Además, las nuevas generaciones de comunicaciones móviles se están moviendo hacia el uso de frecuencias cada vez más altas, como las ondas milimétricas, que son más sensibles a la presencia de cualquier objeto en el entorno, incluidos los humanos. La investigación y el diseño de antenas y dispositivos que tengan en cuenta el cuerpo humano requiere pruebas en el entorno donde se supone que deben usarse. Los fantomas se convierten en una herramienta para evaluar la transmisión de señales electromagnéticas en un medio equivalente al cuerpo para evitar la experimentación en humanos o animales. Además de eso, se puede estudiar la influencia de estas ondas electromagnéticas sobre los propios tejidos en cuanto a la tasa de absorción específica (SAR).[CA] L'evolució constant de la tecnologia i la recerca de noves aplicacions que milloren la vida de les persones ha portat a la incorporació d'aquestes tecnologies en l'organisme. Les xarxes sense fils d'àrea corporal (WBAN) són un bon exemple d'açò, que consisteixen en xarxes de comunicacions ubicades al propi cos, tant en la superfície com implantades en el seu interior mitjançant l'ús de dispositius sense fils. Aquestes xarxes empren el cos humà com a medi de transmissió, per la qual cosa se n'ha d'avaluar la influència sobre la propagació. A més, les noves generacions de comunicacions mòbils s'estan movent cap a l'ús de freqüències cada vegada més altes, com les ones mil·limètriques, que són més sensibles a la presència de qualsevol objecte en l'entorn, incloent-hi els humans. La investigació i el disseny d'antenes i dispositius que tinguen en compte el cos humà requereix proves en l'entorn on se suposa que han d'usar-se. Els fantomes esdevenen una eina per a avaluar la transmissió de senyals electromagnètics en un medi equivalent al cos per tal d'evitar l'experimentació en humans o animals. A més d'això, es pot estudiar la influència d'aquestes ones electromagnètiques sobre els teixits mateixos en relació amb la taxa d'absorció específica (SAR).[EN] The constant evolution of technology and the search for new applications that improve people's lives has led to the arrival of the incorporation of these technologies in the organism. Wireless body area networks (WBANs) are a good example of this, consisting of communications networks located in the body itself, both on the surface and implanted inside it through the use of wireless devices. These networks use the human body as the transmitting medium, so its influence over the propagation has to be assessed. Besides, new generations of mobile communications are moving towards the use of higher frequencies, as the millimetre waves, which are more sensitive to the presence of any object in the environment, including humans. The research and design of antennas and devices that take into account the human body requires testing in the environment where these are supposed to be used. Phantoms become a tool for evaluating the transmission of electromagnetic signals in a body-equivalent medium in order to avoid experimentation on humans or animals. In addition to that, the influence of these electromagnetic waves over the tissues themselves can be studied with regard to the specific absorption rate (SAR).This thesis has been possible thanks to the funding contribution of the Universitat Polit`ecnica de Val`encia through the PAID-01-16 programme. This work was also supported by the UPV-IIS La Fe programme (STUDER, 2016 and EMOTE, 2017). The research stay was supported by the European Union’s Erasmus+ funding programme under a traineeship grant.Castelló Palacios, S. (2019). Wideband Electromagnetic Body Phantoms for the Evaluation of Wireless Communications in the Microwave Spectrum [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/13218

Dielectric Characterization of In Vivo Abdominal and Thoracic Tissues in the 0.5 26.5 GHz Frequency Band for Wireless Body Area Networks

(c) 2019 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.[EN] The dielectric properties of biological tissues are of utmost importance in the development of wireless body area networks (WBANs), especially for implanted devices. The early design stages of medical devices like capsule endoscopy, pacemakers, or physiological sensors rely on precise knowledge of the dielectric properties of the tissues present in their surrounding medium. Many of these applications make use of electromagnetic phantoms, which are software or physical models that imitate the shape and the electromagnetic properties of the tissues. They are used for designing devices in software simulations and for testing them in laboratory trials, aiding in both the development of WBAN antennas or in communication link evaluations. The existing reports about dielectric in vivo properties are limited and have drawbacks like: low variety of characterized tissues, lacking some relevant ones, and limitations and inhomogeneity in the measured frequency range. This paper aims at filling that gap by providing a new database of dielectric properties of biological tissues measured in vivo . In particular, it is focused on the tissues of the thoracic and the abdominal regions, measured at the same wide frequency band, on the same animal specimen, and under the same conditions. The properties have been obtained by measuring porcine tissues in the 0.5¿26.5 GHz band with the open-ended coaxial technique. In this paper, we focus on those tissues that have been scarcely characterized so far in the literature, like heart, esophagus, stomach, and pancreas. The Cole¿Cole fitting parameters of the measured tissues and their uncertainties are provided.This work was supported in part by UPV-IIS LaFe Program (STuDER, 2016, and EMOTE, 2018), in part by the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-16) from the Universitat Politecnica de Valencia, in part by the European Union's H2020: MSCA: ITN Programs for the "Wireless In-Body Environment Communication-WiBEC'' Project, under Grant 675353, and in part by the "mmWave Communications in the Built Environments-WaveComBE'' Project, under Grant 766231.Fornés Leal, A.; Cardona Marcet, N.; Frasson, M.; Castelló-Palacios, S.; Nevárez, A.; Pons Beltrán, V.; Garcia-Pardo, C. (2019). Dielectric Characterization of In Vivo Abdominal and Thoracic Tissues in the 0.5 26.5 GHz Frequency Band for Wireless Body Area Networks. IEEE Access. 7:31854-31864. https://doi.org/10.1109/ACCESS.2019.2903481S3185431864