| 1. |
- Abtahi, Farhad, 1981-
(författare)
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Aspects of Electrical Bioimpedance Spectrum Estimation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrical bioimpedance spectroscopy (EBIS) has been used to assess the status or composition of various types of tissue, and examples of EBIS include body composition analysis (BCA) and tissue characterisation for skin cancer detection. EBIS is a non-invasive method that has the potential to provide a large amount of information for diagnosis or monitoring purposes, such as the monitoring of pulmonary oedema, i.e., fluid accumulation in the lungs. However, in many cases, systems based on EBIS have not become generally accepted in clinical practice. Possible reasons behind the low acceptance of EBIS could involve inaccurate models; artefacts, such as those from movements; measurement errors; and estimation errors. Previous thoracic EBIS measurements aimed at pulmonary oedema have shown some uncertainties in their results, making it difficult to produce trustworthy monitoring methods. The current research hypothesis was that these uncertainties mostly originate from estimation errors. In particular, time-varying behaviours of the thorax, e.g., respiratory and cardiac activity, can cause estimation errors, which make it tricky to detect the slowly varying behaviour of this system, i.e., pulmonary oedema.The aim of this thesis is to investigate potential sources of estimation error in transthoracic impedance spectroscopy (TIS) for pulmonary oedema detection and to propose methods to prevent or compensate for these errors. This work is mainly focused on two aspects of impedance spectrum estimation: first, the problems associated with the delay between estimations of spectrum samples in the frequency-sweep technique and second, the influence of undersampling (a result of impedance estimation times) when estimating an EBIS spectrum. The delay between frequency sweeps can produce huge errors when analysing EBIS spectra, but its effect decreases with averaging or low-pass filtering, which is a common and simple method for monitoring the time-invariant behaviour of a system. The results show the importance of the undersampling effect as the main estimation error that can cause uncertainty in TIS measurements. The best time for dealing with this error is during the design process, when the system can be designed to avoid this error or with the possibility to compensate for the error during analysis. A case study of monitoring pulmonary oedema is used to assess the effect of these two estimation errors. However, the results can be generalised to any case for identifying the slowly varying behaviour of physiological systems that also display higher frequency variations. Finally, some suggestions for designing an EBIS measurement system and analysis methods to avoid or compensate for these estimation errors are discussed.
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| 2. |
- Abtahi, Farhad, 1981-
(författare)
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Towards Heart Rate Variability Tools in P-Health : Pervasive, Preventive, Predictive and Personalized
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heart rate variability (HRV) has received much attention lately. It has been shown that HRV can be used to monitor the autonomic nervous system and to detect autonomic dysfunction, especially vagal dysfunction. Reduced HRV is associated with several diseases and has also been suggested as a predictor of poor outcomes and sudden cardiac death. HRV is, however, not yet widely accepted as a clinical tool and is mostly used for research. Advances in neuroimmunity with an improved understanding of the link between the nervous and immune systems have opened a new potential arena for HRV applications. An example is when systemic inflammation and autoimmune disease are primarily caused by low vagal activity; it can be detected and prognosticated by reduced HRV. This thesis is the result of several technical development steps and exploratory research where HRV is applied as a prognostic diagnostic tool with preventive potential. The main objectives were 1) to develop an affordable tool for the effective analysis of HRV, 2) to study the correlation between HRV and pro-inflammatory markers and the potential degree of activity in the cholinergic anti-inflammatory pathway, and 3) to develop a biofeedback application intended for support of personal capability to increase the vagal activity as reflected in increased HRV. Written as a compilation thesis, the methodology and the results of each study are presented in each appended paper. In the thesis frame/summary chapter, a summary of each of the included papers is presented, grouped by topic and with their connections. The summary of the results shows that the developed tools may accurately register and properly analyse and potentially influence HRV through the designed biofeedback game. HRV can be used as a prognostic tool, not just in traditional healthcare with a focus on illness but also in wellness. By using these tools for the early detection of decreased HRV, prompt intervention may be possible, enabling the prevention of disease. Gamification and serious gaming is a potential platform to motivate people to follow a routine of exercise that might, through biofeedback, improve HRV and thereby health.
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| 3. |
- Ferreira, Javier, 1982-
(författare)
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Modular textile-enabled bioimpedance system for personalized health monitoring applications
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A growing number of factors, including costs, technological advancements, ageing populations, and medical errors, are leading industrialized countries to invest in research on alternative solutions to improve their health-care systems and increase patients’ quality of life. Personal health systems (PHS) examplify the use of information and communication technologies that enable a paradigm shift from the traditional hospital-centered healthcare delivery model toward a preventive and person-centered approach. PHS offer the means to monitor a patient’s health using wearable, portable or implantable systems that offer ubiquitous, unobtrusive biodataacquisition, allowing remote monitoring of treatment and access to the patient’s status. Electrical bioimpedance (EBI) technology is non-invasive, quick and relatively affordable technique that can be used for assessing and monitoring different health conditions, e.g., body composition assessments for nutrition. When combined with state-of-the-art advances in sensors and textiles, EBI technologies are fostering the implementation of wearable bioimpedance monitors that use functional garments for personalized healthcare applications. This research work isfocused on the development of wearable EBI-based monitoring systems for ubiquitous health monitoring applications. The monitoring systems are built upon portable monitoring instrumentation and custom-made textile electrode garments.Portable EBI-based monitors have been developed using the latest material technology and advances in system-on-chip technology. For instance, a portable EBI spectrometer has been validated against a commercial spectrometer for total body composition assessment using functional textile electrode garments. The development of wearable EBI-based monitoring units using functional garments and dry textile electrodes for body composition assessment and respiratory monitoring has been shown to be a feasible approach. The availability of these measurement systems indicates progress toward the real implementation of personalized healthcare systems.
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| 4. |
- Marquez Ruiz, Juan Carlos
(författare)
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Sensor-Based Garments that Enable the Use of Bioimpedance Technology : Towards PersonalizedHealthcare Monitoring.
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Functional garments for physiological sensing purposes have been utilized in several disciplinesi.e. sports, firefighting, military and medical. In most of the cases textile electrodes (Textrodes)embedded in the garment are employed to monitor vital signs and other physiologicalmeasurements. Electrical Bioimpedance (EBI) is a non-invasive and effective technology that canbe used for detection and supervision of different health conditions. In some specific applicationssuch as body composition assessment EBIS has shown encouraging results proving good degreeof effectiveness and reliability. In a similar way Impedance Cardiography (ICG) is anothermodality of EBI primarily concerned with the determination of Stroke Volume SV, indices ofcontractility, and other aspects of hemodynamics.EBI technology in the previously mentioned modalities can benefit from a integration with agarment; however, a successful implementation of EBI technology depends on the goodperformance of textile electrodes. The main weakness of Textrodes is a deficient skin-electrodeinterface which produces a high degree of sensitivity to signal disturbances. This sensitivity canbe reduced with a suitable selection of the electrode material and an intelligent and ergonomicgarment design that ensures an effective skin-electrode contact area.This research work studies the performance of textile electrodes and garments for EBIspectroscopy for Total Body Assessment and Transthoracic Electrical Bioimpedance (TEB) forcardio monitoring. Their performance is analyzed based on impedance spectra, estimation ofparameters, influence of electrode polarization impedance Zep and quality of the signals using asreference Ag/AgCl electrodes. The study includes the analysis of some characteristics of thetextile electrodes such as conductive material, skin-electrode contact area size and fabricconstruction.The results obtained in this research work present evidence that textile garments with a dry skinelectrodeinterface like the ones used in research produce reliable EBI measurements in bothmodalities: BIS for Total Body Assessment and TEB for Impedance Cardiography. Textiletechnology, if successfully integrated, may enable the utilization of EBI in both modalities andconsequently implementing wearable applications for home and personal health monitoring.
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| 5. |
- Seoane, Fernando, 1976-
(författare)
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Electrical Bioimpedance Cerebral Monitoring : Effects of Hypoxia
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrical bioimpedance spectroscopy is one way to study the electrical properties of biological matter. Different applications of electrical bioimpedance measurements have already been used in both research and clinical scenarios i.e. impedance plethysmography, total body water contents, etc. The electrical properties of tissue reflect the electrical characteristics of the constituent elements of the tissue and depend on its structure. Thus study of the electrical properties not only makes it possible to differentiate among tissues but also to determine the tissue condition. During hypoxia/ischemia the cell activates a certain chain of mechanisms of cellular adaptation in response to the insult. A consequence of these response mechanisms is that the biochemical composition of the cellular environment is altered and the cells swell (cellular edema). These alterations affect the electrical properties of tissue and the changes can be observed through measurement of the electrical bioimpedance of the affected tissue. Based on these ideas, this research work studies the effects of hypoxia/ischemia on the brain electrical impedance. The aim is to obtain the fundamental knowledge that may lead to the development of useful clinical tools for cerebral monitoring based on electrical bioimpedance spectroscopy.
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| 6. |
- Alonso, Fabiola, 1980-
(författare)
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Models and Simulations of the Electric Field in Deep Brain Stimulation : Comparison of Lead Designs, Operating Modes and Tissue Conductivity
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deep brain stimulation (DBS) is an established surgical therapy for movement disorders such as Parkinson’s disease (PD) and essential tremor (ET). A thin electrode is implanted in a predefined area of the brain with the use of stereotactic neurosurgery. In the last few years new DBS electrodes and systems have been developed with possibilities for using more parameters for control of the stimulation volume.In this thesis, simulations using the finite element method (FEM) have been developed and used for investigation of the electric field (EF) extension around different types of DBS lead designs (symmetric, steering) and stimulation modes (voltage, current). The electrode surrounding was represented either with a homogeneous model or a patient-specific model based on individual preoperative magnetic resonance imaging (MRI). The EF was visualized and compared for different lead designs and operating modes.In Paper I, the EF was quantitatively investigated around two lead designs (3389 and 6148) simulated to operate in voltage and current mode under acute and chronic time points following implantation.Simulations showed a major impact on the EF extension between postoperative time points which may explain the clinical decisions to change the stimulation amplitude weeks after implantation. In Paper II, the simulations were expanded to include two leads having steering function (6180, Surestim1) and patient-specific FEM simulations in the zona incerta. It was found that both the heterogeneity of the tissue and the operating mode, influence the EF distribution and that equivalent contact configurations of the leads result in similar EF. The steering mode presented larger volumes in current mode when using equivalent amplitudes. Simulations comparing DBS and intraoperative stimulation test using a microelectrode recording (MER) system (Paper III), showed that several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution and that the DBS EF volume can cover, but also extend to, other anatomical areas.Paper IV introduces a method for an objective exploitation of intraoperative stimulation test data in order to identify the optimal implant position in the thalamus of the chronic DBS lead. Patient-specific EF simulations were related to the anatomy with the help of brain atlases and the clinical effects which were quantified by accelerometers. The first results indicate that the good clinical effect in ET is due to several structures around the ventral intermediate nucleus of the thalamus.
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| 7. |
- Ferreira Gonzalez, Javier, 1982-
(författare)
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Textile-enabled Bioimpedance Instrumentation for Personalised Health Monitoring Applications
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A growing number of factors, including the costs, technological advancements, an ageing population, and medical errors are leading industrialised countries to invest in research on alternative solutions to improving their health care systems and increasing patients’ life quality. Personal Health System (PHS) solutions envision the use of information and communication technologies that enable a paradigm shift from the traditional hospital-centred healthcare delivery model toward a preventive and person-centred approach. PHS offers the means to follow patient health using wearable, portable or implantable systems that offer ubiquitous, unobtrusive bio-data acquisition, allowing remote access to patient status and treatment monitoring.Electrical Bioimpedance (EBI) technology is a non-invasive, quick and relatively affordable technique that can be used for assessing and monitoring different health conditions, e.g., body composition assessments for nutrition. EBI technology combined with state-of-the-art advances in sensor and textile technology are fostering the implementation of wearable bioimpedance monitors that use functional garments for the implementation of personalised healthcare applications.This research studies the development of a portable EBI spectrometer that can use dry textile electrodes for the assessment of body composition for the purposes of clinical uses. The portable bioimpedance monitor has been developed using the latest advances in system-on-chip technology for bioimpedance spectroscopy instrumentation. The obtained portable spectrometer has been validated against commercial spectrometer that performs total body composition assessment using functional textrode garments.The development of a portable Bioimpedance spectrometer using functional garments and dry textile electrodes for body composition assessment has been shown to be a feasible option. The availability of such measurement systems bring closer the real implementation of personalised healthcare systems.
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| 8. |
- Gunnarsson, Emanuel
(författare)
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On the elements of E-textiles : Fabrication and characterisation of textile routing and electrodes
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- “Smart textile” as a notion was demarcated approximately 25 years ago, leading to an enthusiastic hype around the research. Both academic efforts and members of the maker community developed prototypes and artistic creations that incorporated smart features into textiles. From the start of this research era, numerous authors suggested that smart textiles had the potential to revolutionise the healthcare sector. At around the same time, the European Commission had started raising concerns about the demographic trends in Europe, with an ageing population and decreasing birth rates. The need for long-term solutions to address the predicted increase in healthcare demands became evident. Despite 25 years of research with many papers suggesting a soon-to-come commercial breakthrough for smart textiles, such a breakthrough has yet to be seen. There is only a handful of smart textile products on the market currently, and the much-anticipated improvement in the healthcare sector promised by smart textile research is still absent. At the time of writing this thesis, the European Standardisation Committee (CEN) expresses the view that part of the reason for the lack of a commercial breakthrough for smart textiles is the absence of regulations and standards. Technical reports and testing standards regarding smart textiles are being issued continuously by both the International Electrotechnical Committee (IEC), the CEN and the International Organization for Standardization (ISO). These organisations also strive to harmonise the issued guidelines. It is crucial that these regulatory documents describe metrics that are relevant to the applications. Moreover, if easily adopted textile-friendly methods for producing smart textile elements were available to potential producers, in addition to these regulations, the preconditions for a less financially risky market with better functioning smart textile products could be established. This, in turn, might stimulate an increase in the production of smart textile products intended for personalised health. This thesis summarises several aspects of smart textile intended for personalised health (P-health). It provides both suggestions on how to test elements of the textiles properly (their interface with the human body) and how to manufacture components of a smart textile system, such as electrodes and electrical routing. The main objectives of the work behind this thesis include: 1) investigating how functional building blocks for smart textile garments intended for p-health can be manufactured in a textile-friendly way and 2) investigating how to characterise these building blocks in the most appropriate way. It is concluded that such building blocks can be produced and used for smart textile garments in both daily life activities and therapeutic situations. The thesis demonstrates the production of electrically insulated routing integrated into a textile fabric, all done in a single textile production step. For the measurement methods, it is argued that skin-electrode impedance between human subjects and textile electrodes should be measured in-vivo using a three-electrode setup. Additionally, the thesis proposes that instead of measuring sheet resistance, it is better to measure the resistance of the specific smart textile element, as it is shown that sheet resistance is not always applicable to conductive fabrics made from interlaced conductive yarns.
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| 9. |
- Vega Barbas, Mario, 1984-
(författare)
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Accessible interaction solution based on confidence for the deployment of pervasive sensitive services in intelligent environments
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Services based on the Information and Communications Technologies (ICT) are present more and more in the lives of people. The advancement of ICT in technical and social acceptance terms has led the creation of new models of service provision. These provision models involve further integration with people's activities so that are not only present in their professions or civic space but also in a more intimate areas related to their own identity. So it is now common to find services aware of user's health, their domestic habits, ideology, etc. Therefore, the analysis of existing services must be open out to include other aspects related to the way of being and feeling of their members. This way is possible to ensure both the technical correctness of its features as promoting safe and respectful solutions both of civic rights as the way of being and feeling of its members.From the engineering point of view, the user perspective has historically encompassed under the concept of technological acceptance. Within this field can be interpreted as friendly solutions adapted to users will encourage the acceptance by them. Solution acceptance is desirable although it is difficult to ensure. This difficulty is due to the lack of the number of variables that affect the acceptance of technological solutions and the difficulty of optimizing the known variables.In this thesis it is studied and characterized one of the variables that affect the acceptance of existing services: confidence. Confidence is defined in psychological terms, providing its characterization with the aim of be used in typical methods of engineering. Also different tools are proposed to facilitate the optimization of this confidence in services whose complexity establishes this variable in a basic issue to improve acceptance.Health services deployed in a home have been chosen as working context for this thesis. This scenario presents a number of acceptance restrictions on the technology used to create services and how they manage the acquired user information. It comes to highly sensitive and delocalized services that can affect to the user's perception of the environment, the home, and generate fear or rejection to prevent final adoption as a valid solution.Once defined the generic framework, the main objective of this dissertation is focused on promote the acceptance of new pervasive and personalized health services and their deployment in domestic intelligent environments through a layout that promotes a psychological state of confidence in users. To achieve this goal, a set of results, both conceptual, technological and experimental, have been provided. In particular, it has offered a complete characterization of the feeling of confidence from a viewpoint of engineering and a definition of sensitive or delocalized pervasive service. Furthermore, a method for the inclusion of the Interaction Design discipline in engineering processes of such services through a set of patterns of interaction is offered. Finally, this thesis provides the development of a software architecture to ensure proper deployment of these pervasive sensitive services in intelligent environments in a confident way.Discussion of the results suggests the extension of the deployment model to different services of the Information Society that handle sensitive data both in the context of the digital home and other settings where the user perform everyday activities such as work spaces or schools. The future work lines include the imminent need to apply the results to ongoing developments, within research projects in those the author takes part, and the development of new research lines aimed at creating new spaces and interaction technologies as advanced accessible interfaces, toys of the future, confident visualization systems or security systems based on the condition of the user.
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