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  • 201.
    Seoane, Fernando
    et al.
    School of Engineering, University College of Borås.
    Bragós, Ramon
    Department of Electronic Engineering, Technical University of Catalonia.
    Lindecrantz, Kaj
    School of Engineering, University College of Borås.
    Current Source for Multifrequency Broadband Electrical Bioimpedance Spectroscopy Systems: A Novel Approach2006In: 2006 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Vols 1-15, 2006, p. 5121-5125Conference paper (Refereed)
    Abstract [en]

    New research and clinical applications of broadband electrical bioimpedance spectroscopy arise; increasing the upper limit frequency used in the measurement systems. The current source, an essential block of an electrical bioimpedance impedance analyzer, must have a large-enough output impedance at any frequency of operation to keep the output current constant regardless of the value of working load. In this paper a novel approach to increase the output impedance of a common voltage controlled current source is proposed. The circuit is analyzed, implemented and tested. The results, remarking the significant effect of the circuit parasitic capacitances, show a clear increment of the output impedance, but smaller than the originally expected

  • 202.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Bragós, Ramon
    Technical University of Catalonia.
    Lindecrantz, Kaj
    Current Source for Wideband Electrical Bioimpedance Spectroscopy Based on a Single Operational Amplifier2006In: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING 2006, VOL 14, PTS 1-6 / [ed] Kim, SI; Suh, TS, 2006, p. 707-710Conference paper (Refereed)
    Abstract [en]

    Traditionally, measurements of electrical bioimpedance for medical diagnostic purposes have used only low frequencies, usually below 100 kHz. The analysis focused only on the resistive part of the impedance; very often at low frequencies the reactive part of the impedance is negligible. Recent studies of the electrical bioimpedance spectrum, both real and imaginary parts, have indicated new potential applications e.g. detection of meningitis, skin cancer assessment and brain cellular edema detection. An important functional unit in a wideband impedance spectrometer is the current source used to inject the current into the tissue under study. A current source must provide an output current virtually constant over the frequency range of interest and independent of the load at the output. Several designs have been proposed over the years but the performance of them all degraded markedly near bellow 1 MHz e.g. Ackmann in 1993, Bragos et al in 1994 and Bertemes-Filho et al in 2000. The development of electronic technology has made available devices that allow us to obtain a current source with large output impedance, larger than 100 k Omega, above I MHz and based in a simple single Op-Amp circuit topology. Simulation results and experimental measurements are compared and the most important parameters of the VCCS are analytically studied and experimentally tested, including the dependency to changes in the circuit elements and the incidence of the Op-Amp parameters on the current source features.

  • 203. Seoane, Fernando
    et al.
    Bragós, Ramon
    Technical University of Catalonia.
    Lindecrantz, Kaj
    Högskolan i Borås.
    Riu, Pere
    Technical University of Catalonia.
    Current Source Design for Electrical Bioimpedance Spectroscopy2008In: Encyclopedia of Healthcare Information Systems / [ed] N. Wickramasinghe, & E. Geisler, IGI Global, 2008, p. 359-367Chapter in book (Refereed)
    Abstract [en]

    The passive electrical properties of biological tissue have been studied since the 1920s, and with time, the use of Electrical Bioimpedance (EBI) in medicine has successfully spread (Schwan, 1999). Since the electrical properties of tissue are frequency-dependent (Schwan, 1957), observations of the bioimpedance spectrum have created the discipline of Electrical Impedance Spectroscopy (EIS), a discipline that has experienced a development closely related to the progress of electronic instrumentation and the dissemination of EBI technology through medicine.

  • 204. Seoane, Fernando
    et al.
    Buendia, Ruben
    Gil-Pita, Roberto
    Department of Theory of the Signal and Communications, University of Alcala, Madrid, Spain.
    Cole parameter estimation from electrical bioconductance spectroscopy measurements2010In: 2010 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), IEEE Press, 2010, Vol. 2010, p. 3495-3498Conference paper (Refereed)
    Abstract [en]

    Several applications of Electrical Bioimpedance (EBI) make use of Cole parameters as base of their analysis, therefore Cole parameters estimation has become a very common practice within Multifrequency- and EBI spectroscopy. EBI measurements are very often contaminated with the influence of parasitic capacitances, which contributes to cause a hook-alike measurement artifact at high frequencies in the EBI obtained data. Such measurement artifacts might cause wrong estimations of the Cole parameters, contaminating the whole analysis process and leading to wrong conclusions. In this work, a new approach to estimate the Cole parameters from the real part of the admittance, i.e. the conductance, is presented and its performance is compared with the results produced with the traditional fitting of complex impedance to a depressed semi-circle. The obtained results prove that is feasible to obtain the full Cole equation from only the conductance data and also that the estimation process is safe from the influence capacitive leakage.

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    RUBU-EBMC-2010
  • 205.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Ferreira, Javier
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Marquez, Juan Carlos
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Skrifvars, Mikael
    University of Borås.
    Conductive Polymer Films as Textrodes for Biopotential Sensing2011Conference paper (Other academic)
    Abstract [en]

    Introduction: After several years of progresses in textile technology and wearable measurement instrumentation, applications of wearable textile-electronics systems are arising providing a stable background for commercial applications. So far, the available commercial solutions are centered on fitness applications and mostly based in the acquisition of heart rate through Textile Electrodes (Textrodes) based on metallic threads or on conductive rubber compounds. Methods and Materials: In this work a novel material approach is presented to produce Textrodes for acquisition of Electrocardiographic (ECG) signals using a conductive polypropylene (PP1386 from Premix, Finland) polymer material. The polymer was film extruded into thin films, and used as such in the Textrode. Conductive Polymer Films (CPF) have been used to produce Textrodes, and its measurement performance has been compared with the ECG signals obtained with commercial Textrode fabrics and conventional Ag/AgCl electrodes. In order to set up the same measurement conditions, a chest strap tailored to host the testing electrodes has been used. Results: The close resemblance of the ECG acquired with the textile fabric electrodes, the Ag/AgCl electrodes and the PP1386 CPF electrodes suggest that the Polymer Electrodes PP1386 are a feasible alternative to the current textile fabrics that use silver thread as conductive material and also to conductive rubber material. Discussion & Conclusion: The availability of the Conductive Polymer Electrode PP1386 in a film form allows the manufacturing of electrodes by conventional textile processes, like lamination or sewing, therefore facilitating the transition from lab prototyping to industrial manufacturing. Replacing the traditional silver thread as conductive element in the fabrication of Textrodes will definitely reduce the material cost per Textrode. Biocompatibility issues and manufacturability issues must be addressed but the exhibited functional performance is showing encouraging results.

  • 206.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Ferreira, Javier
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Sanchéz, Juan José
    Bragós, Ramon
    Technical University of Catalonia.
    An analog front-end enables electrical impedance spectroscopy system on-chip for biomedical applications2008In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 29, no 6, p. S267-78Article in journal (Refereed)
    Abstract [en]

    The increasing number of applications of electrical bioimpedance measurements in biomedical practice, together with continuous advances in textile technology, has encouraged several researchers to make the first attempts to develop portable, even wearable, electrical bioimpedance measurement systems. The main target of these systems is personal and home monitoring. Analog Devices has made available AD5933, a new system-on-chip fully integrated electrical impedance spectrometer, which might allow the implementation of minimum-size instrumentation for electrical bioimpedance measurements. However, AD5933 as such is not suitable for most applications of electrical bioimpedance. In this work, we present a relatively simple analog front-end that adapts AD5933 to a four-electrode strategy, allowing its use in biomedical applications for the first time. The resulting impedance measurements exhibit a very good performance in aspects like load dynamic range and accuracy. This type of minimum-size, system-on-chip-based bioimpedance measurement system would lead researchers to develop and implement light and wearable electrical bioimpedance systems for home and personal health monitoring applications, a new and huge niche for medical technology development.

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    FSM-PM-2008
  • 207.
    Seoane, Fernando
    et al.
    Högskolan i Borås.
    Lindecrantz, Kaj
    Högskolan i Borås.
    A Novel Approach for Estimation of Electrical Bioimpedance: Total Least Square2007In: 13TH INTERNATIONAL CONFERENCE ON ELECTRICAL BIOIMPEDANCE AND THE 8TH CONFERENCE ON ELECTRICAL IMPEDANCE TOMOGRAPHY 2007, 2007, p. 190-193Conference paper (Refereed)
    Abstract [en]

    There are several methods used for AC-impedance estimation in Electrical Bioimpedance measurements. In this paper we propose a novel method for digital estimation of electrical impedance based in the Total Least Square (TLS) technique and we carry out a performance comparison between the proposed method and the typical Digital Sine Correlation (DSC) method. The TLS method has been implemented using the Singular Value Decomposition approach and the performance of both methods have been compared in terms of robustness against noise and size of the data set. The results indicate that the TLS method shows a better performance for impedance estimation than the DSC with reduced set of measurement samples and high SNR levels, while its performance worsen for increasing number of samples and decreasing SNR. The DSC method exhibits a better robustness against noise, especially for increasing the number of data samples. The main observed advantage of the TLS method is that it suffers from less mathematical constrains than the DSC method, and since the noise levels in bioimpedance applications are not expected to be very high we conclude that the TLS method is a good choice as impedance estimator.

  • 208.
    Seoane, Fernando
    et al.
    Högskolan i Borås.
    Lindecrantz, Kaj
    Högskolan i Borås.
    Electrical Bioimpedance Cerebral Monitoring2008In: Encyclopedia of Healthcare Information Systems / [ed] N. Wickramasinghe, & E. Geisler, IGI Global, 2008, p. 480-486Chapter in book (Refereed)
    Abstract [en]

    Electrical Bioimpedance (EBI) is now a mature technology in medicine, with applications in clinical investigations, physiological research, and medical diagnosis (Schwan, 1999). The first monitoring application of bioimpedance techniques, impedance cardiography, date back to 1940. Since then, bioimpedance measurements have been used in several medical applications, from lung function monitoring and body composition, to skin cancer detection. A complete historical review is available in Malmivuo and Plonsey (1995). A medical imaging modality based on bioimpedance, Electrical Impedance Tomography (EIT) has also been developed. EBI has been used to study the effect in the brain of spreading depression, seizure activity, asphyxia and cardiac arrest since 1950s and 1960s (Ochs & Van Harreveld, 1956), but the most important activities in electrical cerebral bioimpedance research has been during the last 20 years (Holder, 1987; Holder & Gardner-Medwin, 1988).

  • 209.
    Seoane, Fernando
    et al.
    Chalmers University of Technology.
    Lindecrantz, Kaj
    Chalmers University of Technology.
    Enhancement of a Voltage Controlled Current Source for Wideband Electrical Bioimpedance Spectroscopy2006In: Proceedings of Medicinteknikdagarna 2006, 2006, p. 40-41Conference paper (Other academic)
  • 210.
    Seoane, Fernando
    et al.
    Chalmers University of Technology.
    Lindecrantz, Kaj
    Chalmers University of Technology.
    Extraction of Structural Information from Impedance Spectrum Data: A Step towards the Identification of Cellular Oedema2006In: Analysis of Biomedical Signals and Images: 18th EURASIP Conference Biosignal 2006 Proceedings, Brno: VUTIUM press , 2006, p. 90-93Conference paper (Refereed)
  • 211.
    Seoane, Fernando
    et al.
    University of Borås.
    Lindecrantz, Kaj
    University of Borås.
    The Transcephalic Electrical Impedance Method: Principles for Brain Tissue State Monitoring2005In: EU-Biopattern Brain Workshop / [ed] Emmanuel Ifeachor & Kaj Lindecrantz, 2005, p. 11-12Conference paper (Other academic)
  • 212. Seoane, Fernando
    et al.
    Lindecrantz, Kaj
    Olsson, T
    Kjellmer, I
    Flisberg, A
    Bagenholm, R
    Brain electrical impedance at various frequencies: the effect of hypoxia2004In: Proceedings of the 26th Annual International Conference of the IEEE EMBS, San Francisco, CA, USA • September 1-5, 2004, IEEE Engineering in Medicine and Biology Society , 2004, Vol. 3, p. 2322-2325Conference paper (Refereed)
    Abstract [en]

    Non-invasive multi-frequency measurements of transcephalic impedance, both reactance and resistance, can efficiently detect cell swelling of brain tissue and can be used for early detection of threatening brain damage. We have performed experiments on piglets to monitor transcephalic impedance during hypoxia. The obtained results have confirmed the hypothesis that changes in the size of cells modify the tissue impedance. During tissue inflammation after induced hypoxia, cerebral tissue exhibits changes in both reactance and resistance. Those changes are remarkably high, up to 71% over the baseline, and easy to measure especially at certain frequencies. A better understanding of the electrical behaviour of cerebral tissue during cell swelling would lead us to develop effective non-invasive clinical tools and methods for early diagnosis of cerebral edema and brain damage prevention.

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    FSM-EMBC-2004
  • 213.
    Seoane, Fernando
    et al.
    School of Engineering, University College of Borås, SE-50190 Borås.
    Lindecrantz, Kaj
    School of Engineering, University College of Borås, SE-50190 Borås.
    Olsson, Torsten
    bDepartment of Signal and Systems, Chalmers University of Technology, SE-41296 Gothenburg.
    Kjellmer, Ingemar
    cDepartment of Pediatrics, Göteborg University, The Queen Silvia Children's Hospital, SE-41685 Gothenburg.
    Bioelectrical Impedance During Hypoxic Cell Swelling: Modeling of Tissue as a Suspension of Cells2004Conference paper (Refereed)
    Abstract [en]

    Non-invasive multi-frequency measurements of transcephalic impedance, both reactance and resistance, can efficiently detect cytotoxic edema in brain tissue and can be used for early detection of threatening brain damage. The model of biological tissue as a suspension of cells can be used as a valuable guide to identify the optimum range of frequencies for electrical impedance monitoring to detect cell swelling efficiently. We have performed experiments on piglets to monitor transcephalic impedance during hypoxia. The obtained results have confirmed the hypothesis that changes in the size of cells modify the tissue impedance. During tissue inflammation after induced hypoxia, cerebral tissue exhibits changes in both reactance and resistance. Those changes in impedance exhibit certain dependency of frequency in concordance with the suspension of cells model. The experimentally observed changes are remarkably high, up to 71% over the baseline, and easy to measure especially at certain frequencies. A better understanding of the electrical behaviour of cerebral tissue during cell swelling may lead the development effective non-invasive clinical tools and methods for early diagnosis of cerebral edema and brain damage prevention.

  • 214. Seoane, Fernando
    et al.
    Lindecrantz, Kaj
    Olsson, Torsten
    Kjellmer, Ingemar
    Fliesberg, Anders
    Bågenholm, Ralph
    Electrical Bioimpedance Cerebral Monitoring2005In: Medicinteknikdagarna, 2005Conference paper (Other academic)
  • 215. Seoane, Fernando
    et al.
    Lindecrantz, Kaj
    Olsson, Torsten
    Kjellmer, Ingemar
    Flisberg, Anders
    Bågenholm, Ralph
    Spectroscopy study of the dynamics of the transencephalic electrical impedance in the perinatal brain during hypoxia2005In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 26, no 5, p. 849-863Article in journal (Refereed)
    Abstract [en]

    Hypoxia/ischaemia is the most common cause of brain damage in neonates. Thousands of newborn children suffer from perinatal asphyxia every year. The cells go through a response mechanism during hypoxia/ischaemia, to maintain the cellular viability and, as a response to the hypoxic/ischaemic insult, the composition and the structure of the cellular environment are altered. The alterations in the ionic concentration of the intra- and extracellular and the consequent cytotoxic oedema, cell swelling, modify the electrical properties of the constituted tissue. The changes produced can be easily measured using electrical impedance instrumentation. In this paper, we report the results from an impedance spectroscopy study on the effects of the hypoxia on the perinatal brain. The transencephalic impedance, both resistance and reactance, was measured in newborn piglets using the four-electrode method in the frequency range from 20 kHz to 750 kHz and the experimental results were compared with numerical results from a simulation of a suspension of cells during cell swelling. The experimental results make clear the frequency dependence of the bioelectrical impedance, confirm that the variation of resistance is more sensitive at low than at high frequencies and show that the reactance changes substantially during hypoxia. The resemblance between the experimental and numerical results proves the validity of modelling tissue as a suspension of cells and confirms the importance of the cellular oedema process in the alterations of the electrical properties of biological tissue. The study of the effects of hypoxia/ischaemia in the bioelectrical properties of tissue may lead to the development of useful clinical tools based on the application of bioelectrical impedance technology.

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    FSM-PM-2005
  • 216.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Lindecrantz, Kaj
    Olsson, Torsten
    Kjellmer, Ingemar
    Mallard, Carina
    Evolution of Cerebral Bioelectrical Resistance at Various Frequencies During Hypoxia in Fetal Sheep2004In: Australasian physical & engineering sciences in medicine, ISSN 0158-9938, E-ISSN 1879-5447, Vol. 27, no 4Article in journal (Refereed)
  • 217.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Macias, Raul
    Technical University of Catalonia.
    Bragós, Ramon
    Technical University of Catalonia.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Simple voltage-controlled current source for wideband electrical bioimpedance spectroscopy: circuit dependences and limitations2011In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 22, no 11Article in journal (Refereed)
    Abstract [en]

    In this work, the single Op-Amp with load-in-the-loop topology as a current source is revisited. This circuit topology was already used as a voltage-controlled current source (VCCS) in the 1960s but was left unused when the requirements for higher frequency arose among the applications of electrical bioimpedance (EBI). The aim of the authors is not only limited to show that with the currently available electronic devices it is perfectly viable to use this simple VCCS topology as a working current source for wideband spectroscopy applications of EBI, but also to identify the limitations and the role of each of the circuit components in the most important parameter of a current for wideband applications: the output impedance. The study includes the eventual presence of a stray capacitance and also an original enhancement, driving with current the VCCS. Based on the theoretical analysis and experimental measurements, an accurate model of the output impedance is provided, explaining the role of the main constitutive elements of the circuit in the source's output impedance. Using the topologies presented in this work and the proposed model, any electronic designer can easily implement a simple and efficient current source for wideband EBI spectroscopy applications, e.g. in this study, values above 150 kΩ at 1 MHz have been obtained, which to the knowledge of the authors are the largest values experimentally measured and reported for a current source in EBI at this frequency.

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    FSM-MST-2011
  • 218.
    Seoane, Fernando
    et al.
    University College of Borås.
    Mai, Lu
    Persson, Mikael
    Lindecrantz, Kaj
    University College of Borås.
    The Role of the Cerebrospinal Fluid in the Distribution of Electrical Current within the Brain and its Implications for Electrical Bioimpedance Cerebral Monitoring2007In: Medicinteknikdagarna, 2007, Vol. 1Conference paper (Other academic)
  • 219.
    Seoane, Fernando
    et al.
    School of Engineering, University of Borås.
    Marquez, Juan Carlos
    School of Engineering, University of Borås.
    Ferreira, Javier
    School of Engineering, University of Borås.
    Buendia, Ruben
    School of Engineering, University of Borås.
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    The Challenge of the Skin-Electrode Contact in Textile-enabled Electrical Bioimpedance, Measurements for Personalized Healthcare Monitoring Applications2011In: Biomedical Engineering, Trends in Materials Science / [ed] Anthony N. Laskovski, IN-TECH, 2011Chapter in book (Refereed)
  • 220.
    Seoane, Fernando
    et al.
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Rempfer, Markus
    University of Borås.
    Marquez, Juan Carlos
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Lindecrantz, Kaj
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Textile-enabled Instrumentation for Impedance Cardiographic Signals2011Conference paper (Other academic)
  • 221.
    Seoane, Fernando
    et al.
    University of Borås.
    Valero, Miguel Angel
    Technical University of Madrid.
    Garcia-Perez, Agustin
    University of Borås.
    Gallar, Paloma
    Severo Ochoa Hospital.
    Implementation of an Open Telenephrology Platform to Support Home Monitoring2008In: 4th European Conference of the International Federation for Medical and Biological Engineering, ECIFMBE 2008, 2008, p. 1026-1029Conference paper (Refereed)
    Abstract [en]

    Clinical experience on the field of telenephrology validates that televisit sessions effectively support Peritoneal Dialysis (PD) therapies for homebound patients. After achieving the initial priority to enhance the relationship between health professionals and patients, by establishing audiovisual contact through videoconference systems, the next step is to securely integrate biomedical data with telenephrology services. This paper details a validated open interoperable platform for PD home monitoring that provides reliable wireless acquisition and integration of blood pressure, weight and other measurements like peritoneal ultra filtration. The availability of this supplementary information positively enhances the benefits of telenephrology at home. This implementation takes advantage of HL7 CDA and XML standards to integrate data within the Electronic Patient Record (EPR) at hospital premises. The resulting platform provides clinicians at distance with critical information to look for edema, signs of cardiac insufficiency or results of the peritoneal ultrafiltration and the daily urine volume, this way increasing the quality of care and preventing severe renal crisis. The ongoing clinical validation, supported by clinicians and renal homebound patients, shows high acceptation for successful and effective support to PD home patients.

  • 222.
    Shahgaldi, Kambiz
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Manouras, Aristomenis
    KTH, School of Technology and Health (STH), Medical Engineering.
    Abrahamsson, Anna
    Gudmundsson, Petri
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Winter, Reidar
    Three-dimensional echocardiography using single-heartbeat modality decreases variability in measuring left ventricular volumes and function in comparison to four-beat technique in atrial fibrillation2010In: Cardiovascular Ultrasound, E-ISSN 1476-7120, Vol. 8, no 1Article in journal (Refereed)
    Abstract [en]

    Background: Three dimensional echocardiography (3DE) approaches the accuracy of cardiac magnetic resonance in measuring left ventricular (LV) volumes and ejection fraction (EF). The multibeat modality in comparison to single-beat (SB) requires breath-hold technique and regular heart rhythm which could limit the use of this technique in patients with atrial fibrillation (AF) due to stitching artifact. The study aimed to investigate whether SB full volume 3DE acquisition reduces inter-and intraobserver variability in assessment of LV volumes and EF in comparison to four-beat (4B) ECG-gated full volume 3DE recording in patients with AF.

    Methods: A total of 78 patients were included in this study. Fifty-five with sinus rhythm (group A) and 23 having AF (group B). 4B and SB 3DE was performed in all patients. LV volumes and EF was determined by these two modalities and inter-and intraobserver variability was analyzed.

    Results: SB modality showed significantly lower inter-and intraobserver variability in group B in comparison to 4B when measuring LV volumes and EF, except for end-systolic volume (ESV) in intraobserver analysis. There were significant differences when calculating the LV volumes (p < 0.001) and EF (p < 0.05) with SB in comparison to 4B in group B.

    Conclusion: Single-beat three-dimensional full volume acquisition seems to be superior to four-beat ECG-gated acquisition in measuring left ventricular volumes and ejection fraction in patients having atrial fibrillation. The variability is significantly lower both for ejection fraction and left ventricular volumes.

  • 223. Shahgaldi, Kambiz
    et al.
    Söderqvist, Emil
    Gudmundsson, Petri
    Winter, Reidar
    Nowak, Jacek
    Brodin, Lars-Åke
    KTH, School of Technology and Health (STH), Medical Engineering.
    Flow-volume loops derived from three-dimensional echocardiography: a novel approach to the assessment of left ventricular hemodynamics2008In: Cardiovascular Ultrasound, E-ISSN 1476-7120, Vol. 6Article in journal (Refereed)
    Abstract [en]

    Background: This study explores the feasibility of non-invasive evaluation of left ventricular (LV) flow-volume dynamics using 3-dimensional (3D) echocardiography, and the capacity of such an approach to identify altered LV hemodynamic states caused by valvular abnormalities.

    Methods: Thirty-one patients with moderate-severe aortic (AS) and mitral (MS) stenoses (21 and 10 patients, respectively) and 10 healthy volunteers underwent 3D echocardiography with full volume acquisition using Philips Sonos 7500 equipment. The digital 3D data were post-processed using TomTec software. LV flow-volume loops were subsequently constructed for each subject by plotting instantaneous LV volume data sampled throughout the cardiac cycle vs. their first derivative representing LV flow. After correction for body surface area, an average flow-volume loop was calculated for each subject group.

    Results: Flow-volume loops were obtainable in all subjects, except 3 patients with AS. The flow-volume diagrams displayed clear differences in the form and position of the loops between normal individuals and the respective patient groups. In patients with AS, an "obstructive" pattern was observed, with lower flow values during early systole and larger end-systolic volume. On the other hand, patients with MS displayed a "restrictive" flow-volume pattern, with reduced diastolic filling and smaller end-diastolic volume.

    Conclusion: Non-invasive evaluation of LV flow-volume dynamics using 3D-echocardiographic data is technically possible and the approach has a capacity to identify certain specific types of alteration of LV flow-volume pattern caused by valvular abnormalities, thus reflecting underlying hemodynamic states specific for these abnormalities.

  • 224. Shum, Judy
    et al.
    Martufi, Giampaolo
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Di Martino, Elena
    Washington, Christopher B.
    Grisafi, Joseph
    Muluk, Satish C.
    Finol, Ender A.
    Quantitative Assessment of Abdominal Aortic Aneurysm Geometry2011In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 39, no 1, p. 277-286Article in journal (Refereed)
    Abstract [en]

    Recent studies have shown that the maximum transverse diameter of an abdominal aortic aneurysm (AAA) and expansion rate are not entirely reliable indicators of rupture potential. We hypothesize that aneurysm morphology and wall thickness are more predictive of rupture risk and can be the deciding factors in the clinical management of the disease. A non-invasive, image-based evaluation of AAA shape was implemented on a retrospective study of 10 ruptured and 66 unruptured aneurysms. Three-dimensional models were generated from segmented, contrast-enhanced computed tomography images. Geometric indices and regional variations in wall thickness were estimated based on novel segmentation algorithms. A model was created using a J48 decision tree algorithm and its performance was assessed using ten-fold cross validation. Feature selection was performed using the chi(2)-test. The model correctly classified 65 datasets and had an average prediction accuracy of 86.6% (kappa = 0.37). The highest ranked features were sac length, sac height, volume, surface area, maximum diameter, bulge height, and intra-luminal thrombus volume. Given that individual AAAs have complex shapes with local changes in surface curvature and wall thickness, the assessment of AAA rupture risk should be based on the accurate quantification of aneurysmal sac shape and size.

  • 225.
    Sinzinger, Fabian
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    van Kerkvoorde, Jelle
    Eindhoven Univ Technol, Eindhoven, Netherlands..
    Pahr, Dieter H.
    Vienna Univ Technol, Inst Lightweight Design & Struct Biomech, Vienna, Austria.;Karl Landsteiner Univ, Biomech Div, Vienna, Austria..
    Moreno, Rodrigo
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    Predicting the trabecular bone apparent stiffness tensor with spherical convolutional neural networks2022In: Bone Reports, E-ISSN 2352-1872, Vol. 16, p. 101179-, article id 101179Article in journal (Refereed)
    Abstract [en]

    The apparent stiffness tensor is relevant for characterizing trabecular bone quality. Previous studies have used morphology-stiffness relationships for estimating the apparent stiffness tensor. In this paper, we propose to train spherical convolutional neural networks (SphCNNs) to estimate this tensor. Information of the edges, trabecular thickness, and spacing are summarized in functions on the unitary sphere used as inputs for the SphCNNs. The concomitant dimensionality reduction makes it possible to train neural networks on relatively small datasets. The predicted tensors were compared to the stiffness tensors computed by using the micro-finite element method (mu FE), which was considered as the gold standard, and models based on fourth-order fabric tensors. Combining edges and trabecular thickness yields significant improvements in the accuracy compared to the methods based on fourth-order fabric tensors. From the results, SphCNNs are promising for replacing the more expensive mu FE stiffness estimations.

  • 226.
    Smedberg, Åsa
    KTH, School of Information and Communication Technology (ICT), Computer and Systems Sciences, DSV.
    Web Communities for Preventive Health Care - Experienced Usability and Health Impact among Smokers and Overweight People2010In: SECOND INTERNATIONAL CONFERENCE ON EHEALTH, TELEMEDICINE, AND SOCIAL MEDICINE: ETELEMED 2010, PROCEEDINGS / [ed] Finkelstein J; Ossebaard HC; VanGemertPijnen, LOS ALAMITOS: IEEE COMPUTER SOC , 2010, p. 153-158Conference paper (Refereed)
    Abstract [en]

    The number of web based health communities has increased during the latest years, and so has also the number of users. Among these, we find the health communities for people who suffer from lifestyle problems. These communities aim at helping people change their habits, and thereby preventing them from getting severe illnesses later. The communities are used for conversations about everyday struggles for a healthier lifestyle, and they contain issues concerning treatments, exercises, motivation, setbacks, etc. The question is in what ways and to what extent these communities support self-management among the members. This paper presents the results from a survey to members of a web community on overweight and another one on smoking. The results showed the members' appreciation for existing conversational topics on facts and motivation. They also thought that answers in which the senders offer new perspectives were valuable and could increase.

  • 227. Sommer, G.
    et al.
    Regitnig, P.
    Költringer, L.
    Holzapfel, Gerhard A.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Biaxial mechanical properties of intact and layer-dissected human carotid arteries at physiological and supraphysiological loadings2010In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 298, no 3, p. H898-H912Article in journal (Refereed)
    Abstract [en]

    Sommer G, Regitnig P, Koltringer L, Holzapfel GA. Biaxial mechanical properties of intact and layer-dissected human carotid arteries at physiological and supraphysiological loadings. Am J Physiol Heart Circ Physiol 298: H898-H912, 2010. First published December 24, 2009; doi:10.1152/ajpheart.00378.2009.-Specimens of intact wall tubes of human common carotid arteries (CCA), internal carotid arteries (ICA) (n = 11, age 77.6 yr, SD 6.3), and related adventitia and media-intima tubes are mechanically examined. Cyclic, quasi-static extension-inflation tests at different axial stretches are performed on preconditioned tube specimens. Stress-free configurations show significant stress releases in the circumferential direction of the intact CCA and ICA walls and in the axial directions of the intact CCA walls and the CCA and ICA adventitias. All investigated tissues exhibit strong nonlinear, pseudoelastic mechanical behavior with small hysteresis. The "inversion" feature, where the pressure/axial stretch relationship becomes a vertical line, is found only for intact walls. Axial "inversion stretches" are 1.15 (SD 0.06) for CCA and 1.14 (SD 0.06) for ICA, and related external axial forces are 0.43 N (SD 0.15) and 0.30 N (SD 0.22), respectively. Significant negative correlations between age and axial inversion stretches for CCA (r = -0.67, P = 0.03) and ICA (r = -0.29, P = 0.04) are identified. Adventitias are very compliant at low pressures, but change into stiff tubes at high pressures. The burst pressure of the adventitia is beyond 250 kPa. A relatively low burst pressure of similar to 60 kPa is found in the media-intima tubes, in which the pressure/circumferential stretch relationships are almost independent of the axial stretches. Stress analyses indicate a high degree of material anisotropy for all investigated tissues. High circumferential and axial stresses occur in the media-intima tubes at physiological conditions. The obtained data are intended to serve for an improvement of constitutive laws, determination of constitutive parameters, and enhancing our knowledge of the mechanical functions of arteries and their associated layers in specific pathophysiological and clinical problems, such as hypertension and angioplasty with stenting.

  • 228.
    Stenberg, Mattias
    KTH, School of Technology and Health (STH).
    Concept design and In Vitro evaluation of a novel dynamic displacement Ventricular Assist Device2006Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Ventricular Assist Devices (VADs) are mechanical pumps used to off-load a deceased heart, primarily in late stage congestive heart failure patients. VAD employment may facilitate cardiac recovery, but most often provides time before a suitable heart transplant can be found. Lately, long term use VAD systems have been introduced as an alternative to a heart transplant.

    Traditionally, design of VADs has employed either displacement based pump technologies or radial-flow pumps, also known as rotodynamic pumps. A displacement pump induces a mechanical force on a fluid contained within a defined space, hence giving it motion. Radial-flow pumps impart momentum to a fluid, most often by placing a rotating device in the fluid.

    This thesis introduces a novel pumping concept, combining features from both displacement and radial-flow pumps. A first prototype, the VivicorTM pump, has been designed, fabricated and evaluated In Vitro, the results reported in this thesis.

    The In Vitro evaluation of the VivicorTM pump provides evidence of a pump with mechanical self-regulation based on pump pre-load level, much like a displacement pump. The VivicorTM pump also displays pulsating outflow in combination with an inflow both during pump systole and diastole. The latter provides potential advantages over traditional displacement pumps as smaller cannulae or catheters can be used, facilitating miniaturization. Continuos filling throughout the pumping cycle also require less pressure to be exerted on the fluid, compared to displacement pumps, limiting the risk of mechanical damage to the pumped fluid. The In Vitro evaluation has also provided further insights on necessary design modifications in the second-generation VivicorTM prototype, currently planned. The VivicorTM pumping technology is highly interesting for further development and evaluation for use in ventricular assist applications.

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  • 229.
    Sturm, Dennis
    KTH, School of Technology and Health (STH), Medical sensors, signals and systems (MSSS).
    Wireless Multi-Sensor Feedback Systems for SportsPerformance Monitoring: Design and Development2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless applications have become a common part of daily life. Whether it is mobile phones, the Wi-Fi router at home, the keycard which has replaced the car key, a radio frequency identification access system to a building or a Bluetooth headset for your computer or phone, the means of modern wireless data exchange is an omnipresent technology. In sports, the market is in its infancy for wireless, technical applications or gadgets. Only heart rate monitors and GPS watches are currently used by recreational athletes. Even though most of the larger sports equipment companies regularly launch new products related to sports performance monitoring and mobile phone technology, product innovation leaps are rare.In this work the design of a wireless sports performance measurement platform is presented. Using the example of kayaking, this platform is configured as a paddle performance measuring system, the Kayak XL System, which can monitor propulsive paddle force, paddle kinematics and boat velocity, interalia. A common mobile phone platform has been chosen as the user interface for this system. The design approach focussing on user requests, demands and expectations in combination with the process of iterative technical development are unveiled in this thesis. An evaluation of the system is presented and the work is finalised with an overview of further systems which have been designed based on the developed measurement platform. The Kayak XL System is a flexible system designed to be mounted onto any standard kayak paddle and installed in any competition kayak. Versatility, unobtrusiveness and usability were major design concerns. The developed system consists of four modules plus a software which has been designed for Android mobile phones. The phone communicates with each of the four modules trough Bluetooth radio. These four modules are also referred to as nodes and have specific measurement purposes. Two nodes have been designed to measure paddle force and kinematics, one node has the purpose to measure foot stretcher force and boat motion data, and the fourth node enables a more convenient method of calibrating paddle force measurement. The fourth node is therefore only needed prior to performance data acquisition. Results show that paddle and foot stretcher force can be measured with a resolution below 1N after calibration. Installing the paddle nodes on a previously configured paddle without repeated calibration is facilitated with the compromise of a doubled error margin. The default sampling frequency is set to 100 Hz and can, like all system parameters, be configured on the mobile phone. Real-time computation of complex performance parameters is only limited by the phone CPU. The system adds twice 109 g to the paddle and approximately 850 g to the kayak, excluding the mass of the mobile phone

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  • 230.
    Svantesson, Oscar
    KTH, School of Technology and Health (STH), Medical Engineering.
    Software platform for gait evaluation using MATLAB and off-the-shelf MEMS sensors2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis presents a real time software program written in MATLAB using off-the-self MEMS sensors from Shimmer-Research®. Parallel to the software development, a proof of concept was conducted using the produced program to quantify stride length, stride length variance and stride time for patients diagnosed with Parkinson's disease. Results from testing showed that the system measured the mean stride length error to 2.4% of stride length and a standard deviation of 13.7% of stride length. Results from testing further showed a stride time error of 2.70% of individual stride times with a standard deviation of 1.89%. The system shows promise as a pedagogical, gait analysis training tool for physiotherapists as well as in academic teaching. The system is flexible and data processing functions can be readily re-programmed with other or additional processing features while maintaining user feedback, storage and plotting functionalities implemented in the current version of the program. 

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    Oscar Svantesson Examensarbete
  • 231.
    Svenberg, Hugo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems.
    Sondur, Smyan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems.
    Design och simulering av en elektronkanon som fasplatta till TEM2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The problem with today’s phase plates in transmission electron microscopes (TEM), that are used to improve contrast, are their noise contributions and low resolution. A potential solution to this problem is an electron phase plate which utilize the field potential of an external electron beam that creates a potential crossing for the primary electron beam in the TEM and hence shifts their phase. The aim of this project was to design an electron gun by simulating an electrostatic lens system that should produce an electron phase plate with a certain current and crossover. The lens system design was created in the CAD-software Solid Edge and the simulations were performed in COMSOL Multiphysics. The simulations showed that it is possible to design an electron gun which is able to produce an electron phase plate with a crossover of ~1,8 µm and a current of ~10 µA. The simulations however showed that the electron gun was unable to transfer the electron phase plate into the microscope whilst maintaining its crossover size. The conclusions were, to successfully transfer the electron phase plate, the particle interactions in the electron beam and the spherical aberrations of the lenses must be reduced either by changing to magnetic lenses or by implementing CS-correctors.

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  • 232.
    Söderqvist, Emil
    KTH, School of Technology and Health (STH).
    New approaches to monitoring of cardiac function2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Left ventricular pumping performance may be described by intraventricular pressure and volume variables, usually presented as a pressure-volume plot. However, on-line monitoring of left ventricular pressure and volume with high temporal resolution requires the use of an invasive catheter technique such as, for example, the conductance catheter method. On the other hand, the very invasiveness and complexity of this approach makes it less suitable for clinical use. It is then not surprising that there has been long-felt need to make the conductance method less invasive and attempts have been made to adjust the method to clinical demands and routine in order to extract more information from pressure-volume interplay and possibly translate relevant data to their non-invasive estimates.

    In the present studies, a standard five segmental conductance catheter was used in animal (pig) experiments. Segmental conductances were compared to global conductance. Since the mid-ventricular segment was shown to reflect global volume, which was also shown on theoretical basis, it was concluded that a single segmental catheter most probably could be used to estimate global left ventricular volume.

    Subsequently, a thin and flexible single segmental conductance catheter was constructed and applied to an animal (pig) experimental model. Results were reproducible and very few arrythmias were detected.

    At the next stage, left ventricular isovolumic phases were investigated using the standard conductance catheter method, as well as echocardiographically derived tissue velocity doppler. Conductance was shown to decrease during isovolumic contraction, and an adjustment method was proposed in order to account for the subsequent decrease in pressure-volume loop area.

    In separate experiments, the left ventricular pressure wave form during left ventricular systole was examined, and an algorithm was proposed to discriminate between the changes in afterload, preload and contractility. Results showed clearly discernible patterns of the respective load and contractility alternation.

    Finally, the left ventricular continuous area was monitored continuously during the entire cardiac cycle as a measure of left ventricular volume dynamics in normal subjects and three patients with left ventricular abnormalities using echocardiographic automatic boundary detection. The left ventricular area thus obtained was plotted against its first derivative, to form a flow-volume estimates loop, in accordance with the flow-volume examinations used in respiratory physiology. Data obtained from the abnormal ventricles were presented as flow-volume estimates loops, exemplifying the possible use of the method.

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  • 233.
    Söderqvist, Emil
    et al.
    Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
    Cain, Peter
    Lind, Britta
    Division of Clinical Physiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
    Winter, Reidar
    Nowak, Jacek
    Brodin, Lars-Åke
    Division of Clinical Physiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
    Feasibility of creating estimates of left ventricular flow-volume dynamics using echocardiography2006In: Cardiovascular Ultrasound, E-ISSN 1476-7120, no 4:40Article in journal (Refereed)
    Abstract [en]

    Background:This study explores the feasibility of non-invasive assessment of left ventricular volume and flow relationship throughout cardiac cycle employing echocardiographic methods.

    Methods:Nine healthy individuals and 3 patients with severe left-sided valvular abnormalities were subject to resting echocardiography with automated endocardial border detection allowing real-time estimation of left ventricular volume throughout the cardiac cycle. Global and regional (6 different left ventricular segments) estimates of flow-volume loops were subsequently constructed by plotting acquired instantaneous left ventricular 2-D area data (left ventricular volume) vs. their first derivatives (flow).

    Results:Flow-volume loop estimates were obtainable in 75% of all echocardiographic images and displayed in normal individuals some regional morphological variation with more pronounced isovolumic events in the paraseptal segments and significantly delayed maximal systolic flow paraapically. In patients with aortic stenosis, maximal systolic flow occurred at a lower estimated left ventricular systolic volume whereas in mitral stenosis, maximal diastolic flow was observed at a higher estimated left ventricular diastolic volume. Aortic regurgitation caused a complex alteration of the estimated flow-volume loop shape during diastole.

    Conclusion:Non-invasive assessment of left ventricular flow-volume relationship with echocardiography is technically feasible and reveals the existence of regional variation in flow-volume loop morphology. Valvular abnormalities cause a clear and specific alteration of the estimates of the normal systolic or diastolic flow-volume pattern, likely reflecting the underlying pathophysiology.

  • 234.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments (pre-2005), KTH Syd.
    Carlsson, Camilla
    Brodin, Lars-Åke
    Conductance measurements in the left ventricle: a pressure-flow approach2002In: IFMBE proc., 2002, p. 1012-3Conference paper (Refereed)
  • 235.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments (pre-2005), KTH Syd.
    Carlsson, Camilla
    Brodin, Lars-Åke
    Elmqvist, Håkan
    Kronander, Håkan
    Ericsson, Anders B.
    Design of a single segment conductance catheter for measurement of left ventricular volume2001In: Annual Reports of the Research Reactor Institute, Kyoto University, 2001, p. 151-154Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is to investigate how to best position the sensing electrodes on a single segment conductance catheter, and to calculate the expected performance. Using electrode potential data, obtained with the present five segment conductance catheter in pig experiments, we have interpolated the electrical field at any given point of time, and calculated what volume curve to expect with only two sensing electrodes. Comparison shows that the deviation between our calculated method and the present one is stable and small. Mean deviation with optimized electrode positions was 0.05% per sample, and the maximum deviation found for a single time sample was 2.57%. This indicates that it is possible to build a thin single segment catheter with as good performance as for the present five segment conductance catheter.

  • 236.
    Söderqvist, Emil
    et al.
    Department of Medical Engineering, Karolinska Institutet, Stockholm, Sweden.
    Hultman, Jan
    Källner, Göran
    Nowak, Jacek
    Brodin, Lars-Åke
    Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden.
    The assessment of acute load and contractility changes by left ventricular pressure measurements2006In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 27, no 12, p. 1281-1292Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to establish whether analysis of the left ventricular pressure waveform provides indicative information about cardiac load and contractility and to develop an algorithm for computer-based assessment of changes in these variables. In eight healthy standard breed anaesthetized open-chest pigs, a high frequency response guide-wire mounted pressure sensor was introduced into the left ventricle. Preload reduction was induced by vena cava occlusion, afterload increase by an i.v. injection of phenylephrine and increased contractility by an i.v. injection of adrenalin. Left ventricular pressure waveform analysis was performed by plotting the slope of the pressure curve during the systolic ejection period versus maximal systolic pressure. The analysis revealed characteristic changes in left ventricular pressure and pressure waveform and identified easily discernible reaction patterns in the slope versus maximal pressure plot, specific for each provocation. Analysis of the left ventricular waveform provides indicative information about loading conditions and contractility. The proposed algorithm can easily be implemented in pressure monitoring systems allowing real-time assessment and discrimination of acute changes in preload, afterload and myocardial performance.

  • 237.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments (pre-2005), KTH Syd.
    Lang, Helmuth
    Källner, Göran
    Hultman, Jan
    Lind, Britta
    KTH, Superseded Departments (pre-2005), KTH Syd. KTH, School of Technology and Health (STH).
    Brodin, Lars-Åke
    Left ventricular pressure indicies help to evaluate loading conditions and contractility2002In: IFMBE proc, ISSN 1680-0737, p. 1014-5Article in journal (Refereed)
  • 238.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments (pre-2005), KTH Syd.
    Storaa, Camilla
    KTH, School of Engineering Sciences (SCI), Physics.
    Ericsson, Anders B.
    Brodin, Lars-Åke
    Ultrasound tissue doppler measurements imply that conductance changes in the left ventricle during isovolumic phases are due to tissue motion.2002In: IFMBE proc.,, 2002, p. 1016-7Conference paper (Refereed)
  • 239.
    Ternström, Sten
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Does the acoustic waveform mirror the voice?2005In: Logopedics, Phoniatrics, Vocology, ISSN 1401-5439, E-ISSN 1651-2022, Vol. 30, no 3-4, p. 100-107Article in journal (Refereed)
    Abstract [en]

    Over recent decades, much effort has been invested in the search for acoustic correlates of vocal function and dysfunction. The convenience of non-invasive voice measurements has been a major incentive for this effort. The acoustic signal is a rich but also very diversified source of information. Computer literacy and technical curiosity in the voice care and voice performance communities are now higher than ever, and tools for voice analysis are proliferating. On such a busy scene, a review may be useful of some basic principles for what we can and cannot hope to determine from non-invasive acoustic analysis. One way of doing this is to consider communication by voice as though it were engineered, with layered protocols. This results in a scheme for systematizing the many sources of variation that are present in the acoustic signal, that can complement other strategies for extracting information.

  • 240.
    Ternström, Sten
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Speech, Music and Hearing, TMH.
    Special Issue on Current Trends and Future Directions in Voice Acoustics Measurement2023In: Applied Sciences, E-ISSN 2076-3417, E-ISSN 2076-3417, Vol. 13, no 6Article in journal (Other academic)
    Abstract [en]

    The human voice production mechanism implements a superbly rich communication channel that at once tells us what, who, how, and much more [...]

  • 241.
    Ternström, Sten
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Speech, Music and Hearing, TMH.
    Update 3.1 to FonaDyn: A system for real-time analysis of the electroglottogram, over the voice range2024In: SoftwareX, E-ISSN 2352-7110, Vol. 26Article in journal (Refereed)
    Abstract [en]

    The human voice is notoriously variable, and conventional measurement paradigms are weak in terms of providing evidence for effects of treatment and/or training of voices. New methods are needed that can take into account the variability of metrics and types of phonation across the voice range. The “voice map” is a generalization of the Voice Range Profile (a.k.a. the phonetogram), with the potential to be used in many ways, for teaching, training, therapy and research. FonaDyn is intended as a proof-of concept workbench for education and research on phonation, and for exploring and validating the analysis paradigm of voice-mapping. Version 3.1 of the FonaDyn system adds many new functions, including listening from maps; displaying multiple maps and difference maps to track effects of voice interventions; smoothing/interpolation of voice maps; clustering not only of EGG shapes but also of acoustic and EGG metrics into phonation types; extended multichannel acquisition;24-bit recording with optional max 140 dB SPL; a built-in SPL calibration and signal diagnostics tool; EGG noise suppression; more Matlab integration; script control; the acoustic metrics Spectrum Balance, Cepstral Peak Prominence and Harmonic Richness Factor (of the EGG); and better window layout control. Stability and usability are further improved. Apple M-series processors are now supported natively.

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  • 242.
    Ternström, Sten
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Speech, Music and Hearing, TMH, Music Acoustics.
    Pabon, Peter
    Royal Conservatoire, The Hague, NL.
    Voice Maps as a Tool for Understanding and Dealing with Variability in the Voice2022In: Applied Sciences, E-ISSN 2076-3417, Vol. 12, no 22, p. 11353-11353Article in journal (Refereed)
    Abstract [en]

    Individual acoustic and other physical metrics of vocal status have long struggled to prove their worth as clinical evidence. While combinations of metrics or “features” are now being intensely explored using data analytics methods, there is a risk that explainability and insight will suffer. The voice mapping paradigm discards the temporal dimension of vocal productions and uses fundamental frequency (fo) and sound pressure level (SPL) as independent control variables to implement a dense grid of measurement points over a relevant voice range. Such mapping visualizes how most physical voice metrics are greatly affected by fo and SPL, and more so individually than has been generally recognized. It is demonstrated that if fo and SPL are not controlled for during task elicitation, repeated measurements will generate “elicitation noise”, which can easily be large enough to obscure the effect of an intervention. It is observed that, although a given metric’s dependencies on fo and SPL often are complex and/or non-linear, they tend to be systematic and reproducible in any given individual. Once such personal trends are accounted for, ordinary voice metrics can be used to assess vocal status. The momentary value of any given metric needs to be interpreted in the context of the individual’s voice range, and voice mapping makes this possible. Examples are given of how voice mapping can be used to quantify voice variability, to eliminate elicitation noise, to improve the reproducibility and representativeness of already established metrics of the voice, and to assess reliably even subtle effects of interventions. Understanding variability at this level of detail will shed more light on the interdependent mechanisms of voice production, and facilitate progress toward more reliable objective assessments of voices across therapy or training.

  • 243.
    Thaning, Elin M.
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Asplund, Maria
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Inganäs, Olle W.
    Biomolecular and Organic Electronics, IFM, Linköping University.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Stability of Poly(3,4-ethylene dioxythiophene) Materials Intended for Implants2010In: Journal of Biomedical Materials Research - Part B Applied Biomaterials, ISSN 1552-4973, Vol. 93B, no 2, p. 407-415Article in journal (Refereed)
    Abstract [en]

    This study presents experiments designed to study the stability of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions using phosphate-buffered saline (PBS) and hydrogen peroxide (H2O2) (0 01M) at 37 degrees C over a 5- to 6-week period Voltage pulsing in PBS was used as an additional test environment The influence of switching the counter ion used in electropolymerization from polystyrene sulphonate (PSS) to heparin was investigated Absorbance spectroscopy and cyclic voltammetry were used to evaluate the material properties Most of the samples in H2O2 lost both electroactivity and optical absorbance within the study period, but PEDOT.PSS was found slightly more stable than PEDOT heparin. Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after 5 weeks, disregarding delamination, which was a significant problem especially for polymer on indium tin oxide substrates Voltage pulsing in PBS did not increase degradation. The counter ion influenced the time course of degradation in Oxidizing agents.

  • 244.
    Turco, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Colarieti-Tosti, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Modular miniPET: A comparison between 10 and 12 detector modules2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), IEEE , 2012, p. 2598-2602Conference paper (Refereed)
    Abstract [en]

    By means of computer simulations, scatter fraction, spatial resolution and sensitivity of two 10-detector-module small-animal PET (r77-miniPET and r106-miniPET), are analyzed and compared to the performance of the 12-detector-module PET scanner miniPET II [1]. All simulations have been performed with the well validated Geant4 Application for Emission Tomography (GATE) [2]. Sensitivity and scatter fraction speak in favor of the 10-module scanner: a clear improvement in count rate and scatter fraction was found. Moreover, steeper slopes of noise equivalent count rate curves at low levels of activity was found. Spatial resolution instead was found to be better in the 12-module scanner.

  • 245.
    Töpfer, Fritzi
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Micromachined Microwave Sensors for Non-Invasive Skin Cancer Diagnostics2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Malignant melanoma is one of the cancers with the highest incident rates. It is also the most dangerous skin cancer type and an early diagnosis is crucial for the successful treatment of malignant melanoma patients. If it is diagnosed and treated at an early stage, the survival rate for patients is 99%, however, this is reduced to only 25% if diagnosed at a later stage. The work in this thesis combines microsystem technology, microwave engineering and biomedical engineering to develop a sensing tool for early-stage malignant melanoma diagnostics. Such a tool could not only increase the clinical accuracy of malignant melanoma diagnosis, but also reduce the time needed for examination, and lower the number of unnecessary biopsies. Furthermore, a reliable and easy-to-use tool can enable non-specialist healthcare personnel, including primary care physicians or nurses, to perform a prescreening for malignant melanoma with a high sensitivity. Consequently, a large number of patients could receive a timely examination despite the shortage of dermatologists, which exists in many healthcare systems. The dielectric properties of tumor tissue differ from healthy tissue, which is mainly accounted to a difference in the water content. This difference can be measured by a microwave-based sensing technique called microwave reflectometry. Previously reported microwave-based skin measurements largely relied on standard open-ended waveguide probes that are not suitable for early-stage skin tumor diagnosis. Thus, alternative near-field probe designs based on micromachined dielectric-rod waveguides are presented here. The thesis focuses on a broadband microwave probe that operates in the W-band (75 to 110 GHz), with a sensing depth and resolution tailored to small and shallow skin tumors, allowing a high sensitivity to early-stage malignant melanoma. Prototypes of the probe were fabricated by micromachining and characterized. For the characterization, a novel type of silicon-based heterogeneous sample with tailor-made permittivity was introduced. Furthermore, the performance of the probe was evaluated in vivo. First, through measurements on human volunteers, it was shown that the probe is sensitive to artificially induced changes of the skin hydration. Then, measurements on murine skin melanoma models were performed and small early-stage skin tumors were successfully distinguished from healthy skin. Additionally, a resonant probe for microwave skin sensing was designed and micromachined protoypes were tested on phantom materials. However, the resonant probe was found less suitable than the broadband probe for the measurements on skin. The broadband probe presented in this thesis is the first microwave nearfield probe specifically designed for early-stage malignant melanoma diagnostics and successfully evaluated in vivo.

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  • 246.
    Töpfer, Fritzi
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Emtestam, L.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Diagnosis of malignant melanoma by micromachined near-field millimeter-wave probe2016In: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    A micromachined millimeter-wave probe, optimized for early-stage skin tumor diagnosis has been verified using a murine skin cancer model. Malignant melanoma tumors are clearly distinguishable from surrounding healthy tissue, since the difference in S11 between a malignant melanoma skin tumor and surrounding healthy tissue is 6.7 times larger than typical standard deviations of measurements on the same spot. Furthermore, the probe has an 8 times higher selectivity to a tumor growing in the skin close to the surface as compared to a subcutaneous tumor buried beneath a thick healthy tissue layer. This confirms the optimized sensitivity of the probe to the targeted upper portion of the skin, in which skin tumor growth starts in malignant melanoma patients.

  • 247.
    Töpfer, Fritzi
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Emtestam, Lennart
    Oberhammer, Joachim
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Long-Term Monitoring of Skin Recovery by Micromachined Microwave Near-Field Probe2017In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 27, no 6, p. 605-607Article in journal (Refereed)
    Abstract [en]

    The water content in the epidermis correlates with different pathologic states of the skin; thus its assessment can aid the diagnosis and monitoring of conditions such as inflammation, edema, burns, and skin cancer. A micromachined microwave near-field probe, operating from 90 to 106 GHz, which, in contrast to earlier used microwave probes, has a minimized sensing area of 0.6 mm x 0.5 mm and an optimized sensing depth of 400 mu m in tissue, has been developed and technically characterized by the authors earlier. This letter reports on the long-term monitoring of sodium lauryl sulfate (SLS)-induced skin irritations with the micromachined microwave probe. Aqueous solutions with 1%, 2%, 5%, and 10% SLS were applied to the forearm of a volunteer for 24 h and microwave reflection measurements were taken before and during 11 days after the SLS application. For all SLS-treated spots the microwave absorption reached the highest levels of 4 to 7 days after SLS application and afterward converged toward baseline levels again. The observed biphasic progression of the microwave reflection signal agrees well with trends from the literature for capacitance measurements and for epidermal thickness and signal attenuation in optical coherence tomography after SLS exposure. The measurements indicate that the microwave probe is very suitable to determine changes in the water content in the epidermis and can aid in the diagnosis of pathologic conditions including skin cancer.

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  • 248.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Hegyesi, G.
    Kalinka, G.
    Molnar, J.
    Novak, D.
    LSO based dual slice helical CT and PET demonstrators2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, p. S300-S302Article in journal (Refereed)
    Abstract [en]

    Two demonstrators, a spiralCT and a miniPET, have been designed and constructed for educational purposes. Computed tomographs (CTs) and positron emission tomographs (PETs) are some of the most commonly used structural and functional imaging devices in medicine, respectively. There is a need for transparent demonstrators where the principles of the different modalities and their functions are presented. The aim of the developments of these systems was to present the major building blocks of CT and PET for undergraduate students. Photon detection in both systems is based on small pixelised scintillation crystals with position sensitive PMT readout. Similar analogue and digital data processing based on FPGA technique is applied for the demonstrators and common image reconstruction and presentation software components are used.

  • 249.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnar, J.
    Novak, D.
    Vegh, J.
    Emri, M.
    Tron, L.
    A SPECT demonstrator - revival of a gamma camera2006In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, no 1, p. 274-277Article in journal (Refereed)
    Abstract [en]

    A gamma camera has been updated and converted to serve as a demonstrator for educational purposes. The gantry and the camera head were the only part of the system that remained untouched. The main reason for this modernization was to increase the transparency of the gamma camera by partitioning the different logical building blocks of the system and thus providing access for inspection and improvements throughout the chain. New data acquisition and reconstruction software has been installed. By taking these measures, the camera is now used in education and also serves as a platform for tests of new hardware and software solutions. The camera is also used to demonstrate 3D (SPECT) imaging by collecting 2D projections from a rotatable cylindrical phantom. Since the camera head is not attached mechanically to the phantom, the effect of misalignment between the head and the rotation axis of the phantom can be studied. (c) 2006 Elsevier B.V. All rights reserved.

  • 250. Valentín, A.
    et al.
    Holzapfel, Gerhard A.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Constrained mixture models as tools for testing competing hypotheses in arterial biomechanics: A brief survey2012In: Mechanics research communications, ISSN 0093-6413, E-ISSN 1873-3972, Vol. 42, p. 126-133Article, review/survey (Refereed)
    Abstract [en]

    Hypothesis testing via numerical models has emerged as a powerful tool which permits the verification of theoretical frameworks against canonical experimental and clinical observations. Cleverly designed computational experiments also inspire new methodologies by elucidating important biological processes and restricting parametric spaces. Constrained mixture models of arterial growth and remodeling (G&R) can facilitate the design of computational experiments which can bypass technical limitations in the laboratory, by considering illustrative special cases. The resulting data may then inform the design of focused experimental techniques and the development of improved theories. This work is a survey of computational hypothesis-testing studies, which exploit the unique abilities offered by the constrained mixture theory of arterial G&R. Specifically, we explore the core hypotheses integrated in these models, review their basic mathematical conceptualizations, and recapitulate their most salient and illuminating findings. We then assess how a decade's worth of constrained mixture models have contributed to a lucid, emerging picture of G&R mechanisms.

23456 201 - 250 of 265
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