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  • 201.
    Nilsson, Gert
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Tenland, T.
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Biomedical Applications of Laser-Light Scattering1982In: Biomedical Applications of Laser-Light Scattering / [ed] David B. Sattelle, Amsterdam: Elsevier Biomedical press , 1982, p. 335-348Chapter in book (Other academic)
  • 202.
    Nilsson, Gert
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Salerud, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Tenland, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    The use of Laser Doppler flowmetry in microvascular research1981In: International vascular symposium,1981, 1981Conference paper (Other academic)
  • 203.
    Nilsson, Gert
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Elektriska säkerhetsproblem i: Styrd värmedyna för kliniskt bruk1974Report (Other (popular science, discussion, etc.))
  • 204.
    Nilsson, Gert
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Elektriska säkerhetsproblem II: En överblick över medicintekniska säkerhetsfrågor1974Report (Other (popular science, discussion, etc.))
  • 205.
    Nilsson, Gert
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Öberg, Åke
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Elektriska säkerhetsproblem III: Referenslista1974Report (Other (popular science, discussion, etc.))
  • 206.
    Nilsson, Lena
    et al.
    Linköping University, Department of Medicine and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Goscinski, T.
    Department of Anaesthesiology and Intensive Care, Linköping University Hospital, Linköping, Sweden.
    Kalman, S.
    Department of Anaesthesiology and Intensive Care, Karolinska University Hospital, Huddinge, Sweden.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Combined photoplethysmographic monitoring of respiration rate and pulse: A comparison between different measurement sites in spontaneously breathing subjects2007In: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 51, no 9, p. 1250-1257Article in journal (Refereed)
    Abstract [en]

    Background: The non-invasive photoplethysmographic (PPG) signal reflects blood flow and volume in a tissue. The PPG signal shows variation synchronous with heartbeat (PPGc), as used in pulse oximetry, and variations synchronous with breathing (PPGr). PPGr has been used for non-invasive monitoring of respiration with promising results. Our aim was to investigate PPG signals recorded from different skin sites in order to find suitable locations for parallel monitoring of variations synchronous with heartbeat and breathing. Methods: PPG sensors were applied to the forearm, finger, forehead, wrist and shoulder on 48 awake healthy volunteers. From these sites, seven PPG signals were simultaneously recorded during normal spontaneous breathing over 10 min. Capnometry served as respiration and electrocardiogram (ECG) as pulse reference signals. PPG signals were compared with respect to power spectral content and squared coherence. Results: Forearm PPG measurement showed significantly higher power within the respiratory region of the power spectrum [median (quartile range) 42 (26)%], but significantly lower power within the cardiac region [9 (10)%] compared with the other skin sites. PPG finger measurement showed the opposite, in transmission mode, the power within the respiratory region was significantly lower [4 (10)%] and within the cardiac region significantly higher [45 (25)%] than the other sites. PPGc coherence values were generally high [>0.96 (0.08)], and PPGr coherence values lower [0.83 (0.35)-0.94 (0.17)]. Conclusion: Combined PPG respiration and pulse monitoring is possible, but there are significant differences between the respiratory and cardiac components of the PPG signal at different sites. © 2007 Acta Anaesthesiol Scand.

  • 207.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Goscinski, Tomas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Detection of breaths by photoplethysmography is independent of age and sex2005In: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, p. 19-Conference paper (Refereed)
  • 208.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Goscinski, Tomas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Photoplethysmography for central and obstructive apnea detection2005In: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, p. 19-Conference paper (Refereed)
  • 209.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Goscinski, Tomas
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Lindberg, Lars-Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Time relation between respiratory signals can be analysed by automated algorithms2005In: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, p. 19-Conference paper (Refereed)
  • 210.
    Nilsson, Lena
    et al.
    Linköping University, Department of Medical and Health Sciences, Anesthesiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Anaesthesiology and Intensive Care in Linköping. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre.
    Goscinski, Tomas
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Lindenberger, Marcus
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Johansson, Anders
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Respiratory variations in the photoplethysmographic waveform: acute hypovolaemia during spontaneous breathing is not detected2010In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 31, no 7, p. 953-962Article in journal (Refereed)
    Abstract [en]

    Recent studies using photoplethysmographic (PPG) signals from pulse oximeters have shown potential to assess hypovolaemia during spontaneous breathing. This signal is heavily filtered and reports are based on respiratory variations in the small pulse synchronous variation of PPG. There are stronger respiratory variations such as respiratory synchronous variation (PPGr) in the baseline of the unfiltered PPG signal. We hypothesized that PPGr would increase during hypovolaemia during spontaneous breathing. Hemodynamic and respiratory data were recorded together with PPG infrared signals from the finger, ear and forearm from 12 healthy male volunteers, at rest and during hypovolaemia created by the application of a lower body negative pressure (LBNP) of 15, 30 and 60 cmH(2)O. Hemodynamic and respiratory values changed significantly. From rest to the LBNP of 60 cmH(2)O systolic blood pressure fell from median (IQR) 116 (16) to 101 (23) mmHg, the heart rate increased from 58 (16) to 73 (16) beats min(-1), and the respiratory rate increased from 9.5 (2.0) to 11.5 (4.0) breaths min(-1). The amplitude of PPGr did not change significantly at any measurement site. The strongest effect was seen at the ear, where the LBNP of 60 cmH(2)O gave an amplitude increase from 1.0 (0.0) to 1.31 (2.24) AU. PPG baseline respiratory variations cannot be used for detecting hypovolaemia in spontaneously breathing subjects.

  • 211.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Den andningssynkrona kompenenten av den fotopletysmorgrafiska signalen hos sövda påverkas inte av övertrycksandning2004In: Programbok SFAI-veckan 2004,2004, 2004, p. 149-19Conference paper (Other academic)
    Abstract [sv]

       

  • 212.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    The phase of the respiratory variation in the photoplethysmographic signal is not affected by sympathetic tone2004In: European Journal of Anaesthesiology, ISSN 0265-0215, E-ISSN 1365-2346, Vol. 21, p. 76-77Article in journal (Refereed)
  • 213.
    Nilsson, Lena
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Johansson, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Svanerudh, Johan
    Kalman, Sigga
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Anaesthesiology and Surgical Centre, Department of Anaesthesiology and Intensive Care VHN.
    Is the respiratory component of the photoplethysmographic signal of venous origin?1999In: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 37, p. 912-913Article in journal (Refereed)
  • 214.
    Norén, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Lundberg, Peter
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ressner, Marcus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Wirell, Staffan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology.
    Almer, Sven
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Molecular and Clinical Medicine, Gastroenterology and Hepatology. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease2005In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 15, no 1, p. 148-157Article in journal (Refereed)
    Abstract [en]

    Phosphorus-31 NMR spectroscopy using slice selection (DRESS) was used to investigate the absolute concentrations of metabolites in the human liver. Absolute concentrations provide more specific biochemical information compared to spectrum integral ratios. Nine patients with histopathologically proven diffuse liver disease and 12 healthy individuals were examined in a 1.5-T MR scanner (GE Signa LX Echospeed plus). The metabolite concentration quantification procedures included: (1) determination of optimal depth for the in vivo measurements, (2) mapping the detection coil characteristics, (3) calculation of selected slice and liver volume ratios using simple segmentation procedures and (4) spectral analysis in the time domain. The patients had significantly lower concentrations of phosphodiesters (PDE), 6.3±3.9 mM, and ATP-β, 3.6±1.1 mM, (P<0.05) compared with the control group (10.0±4.2 mM and 4.2±0.3 mM, respectively). The concentrations of phosphomonoesters (PME) were higher in the patient group, although this was not significant. Constructing an anabolic charge (AC) based on absolute concentrations, [PME]/([PME] + [PDE]), the patients had a significantly larger AC than the control subjects, 0.29 vs. 0.16 (P<0.005). Absolute concentration measurements of phosphorus metabolites in the liver are feasible using a slice selective sequence, and the technique demonstrates significant differences between patients and healthy subjects.

  • 215.
    Norén, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Ressner, Marcus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Lundberg, Peter
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Quantification of liver metabolites with phosphorus-31 Magnetic Resonance Spectroscopy2002In: European Congress of Radiology March 1-5, 2002,2002, 2002, p. 353-353Conference paper (Refereed)
  • 216.
    Olsson, E
    et al.
    Uppsala Universitet .
    Ugnell, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Photoplethysmography for simultaneous recording of heart and respiratory rates in new born infants2000In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 89, p. 853-861Article in journal (Refereed)
  • 217. Olsson, E
    et al.
    Ugnell, Håkan
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Photoplethysmography for surveillance of circulation and respiration in newborn infants2000In: International Conference on Fetal and Neonatal Physiological Measurements,2000, 2000Conference paper (Other academic)
  • 218. Palmerud, P.
    et al.
    Zhang, Q.
    Forsman, M.
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Non-invasive photoplethysmography for muscle blood flow assessment in ergonomic applications2010In: European Journal of Applied Physiology, ISSN 1439-6319Article in journal (Refereed)
  • 219.
    Pettersson, Hans
    et al.
    IMT LiU.
    Stenow, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Cai, Hongming
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Öberg, Åke
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Optical aspects of a fibre-optic sensor for respiratory rate monitoring1996In: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 34, p. 448-452Article in journal (Refereed)
  • 220.
    Pettersson, Nils-Erik
    et al.
    Örebro läns landsting.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    Ekstrand, Kristina
    Katrineholms kommun.
    Hult, peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    Lindén, Maria
    Mälardalen University Sweden.
    NovaMedTech – En satsning på att ny medicinsk teknik i Östra Mellansverige2010Conference paper (Other academic)
  • 221.
    Pilt, Kristjan
    et al.
    Tallinn University of Technology, Estonia .
    Ferenets, Rain
    Tallinn University of Technology, Estonia .
    Meigas, Kalju
    Tallinn University of Technology, Estonia .
    Lindberg, Lars-Göran
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Temitski, Kristina
    Tallinn University of Technology, Estonia .
    Viigimaa, Margus
    Tallinn University of Technology, Estonia .
    New Photoplethysmographic Signal Analysis Algorithm for Arterial Stiffness Estimation2013In: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, Vol. 2013Article in journal (Refereed)
    Abstract [en]

    The ability to identify premature arterial stiffening is of considerable value in the prevention of cardiovascular diseases. The "ageing index" (AGI), which is calculated from the second derivative photoplethysmographic (SDPPG) waveform, has been used as one method for arterial stiffness estimation and the evaluation of cardiovascular ageing. In this study, the new SDPPG analysis algorithm is proposed with optimal filtering and signal normalization in time. The filter parameters were optimized in order to achieve the minimal standard deviation of AGI, which gives more effective differentiation between the levels of arterial stiffness. As a result, the optimal low-pass filter edge frequency of 6 Hz and transitionband of 1 Hz were found, which facilitates AGI calculation with a standard deviation of 0.06. The study was carried out on 21 healthy subjects and 20 diabetes patients. The linear relationship (r = 0.91) between each subjects age and AGI was found, and a linear model with regression line was constructed. For diabetes patients, the mean AGI value difference from the proposed model y(AGI) was found to be 0.359. The difference was found between healthy and diabetes patients groups with significance level of P andlt; 0.0005.

    Download full text (pdf)
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  • 222.
    Pope, C E
    et al.
    University of Washington.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Tibbling, Lita
    Evaluation of intraluminal EMG electrodes for the oesophagus and gastrointestinal tract.1984In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 22, no 5, p. 461-464Article in journal (Refereed)
  • 223. POPE, CE
    et al.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    DEBLAN, H
    WINGATE, DL
    MEASUREMENT OF INSTANTANEOUS FLOW VELOCITY IN THE HUMAN GASTROINTESTINAL-TRACT1988In: Gastroenterology, ISSN 0016-5085, E-ISSN 1528-0012, Vol. 95, no 3Article in journal (Refereed)
  • 224. Order onlineBuy this publication >>
    Rattfält, Linda
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Smartware electrodes for ECG measurements: Design, evaluation and signal processing2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis work has been to study textile and screen printed smartware electrodes for electrocardiographic (ECG) measurements both in terms of their electrode properties and possibility to further improve their robustness to movement induced noise by using signal processing. Smartware electrodes for ECG measurements have previously been used in various applications but basic electrical electrode properties have not sufficiently been looked into. Furthermore, we believe that there is a possibility to reduce disturbances in the smartware ECG by adding redundant sensors and applying sensor fusion signal processing.

    Electrical properties of conductive textiles have been evaluated in terms of stability and electrode impedance. Three yarns and textile electrode surfaces were tested. The electrodes made from pure stainless steel and 50\% stainless steel/ 50\% polyester showed acceptable stability of electrode potentials. All electrode measurements were performed on skin.

    Furthermore, we produced six screen printed electrodes and their electrical performance was investigated in an electrochemical cell. The tested inks contained carbon or silver particles in the conduction lines, and Ag/AgCl particles in the electrode surface. Results show that all electrodes were stable in time, with a maximum drift of a few mV during 30 minutes. The silver ink is superior to the carbon based in terms of electrode impedance at the higher frequencies.

    To extract viable physiological information from noisy signals, canonical correlation analysis (CCA) was applied on multi-channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intended to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to averaging of the ECG channels and to the independent component analysis method (ICA). In the dataset consisting of noisy ECG recordings, the signal was uninterpretable in 7% after CCABSS. Corresponding values for averaging and ICA were 33% and 17%, respectively.

    Smartware applications often include heartbeat detection while moving, a measurement situation which is prone to produce noise corrupted ECG signals. To compensate for this, we used an event detector based on a multi-channel input, a model of the event and weighted correlation. For measurements at rest and static muscle tension, the sensitivity of the event detector was 97% and 77% respectively. Corresponding values for the golden standard detector Pan-Tompkins were 96% and 52%, respectively.

     

    List of papers
    1. Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Open this publication in new window or tab >>Electrical characteristics of conductive yarns and textile electrodes for medical applications
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    2007 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 12, p. 1251-1257Article in journal (Refereed) Published
    Abstract [en]

    Clothing with conductive textiles for health care applications has in the last decade been of an upcoming research interest. An advantage with the technique is its suitability in distributed and home health care. The present study investigates the electrical properties of conductive yarns and textile electrodes in contact with human skin, thus representing a real ECG-registration situation. The yarn measurements showed a pure resistive characteristic proportional to the length. The electrodes made of pure stainless steel (electrode A) and 20% stainless steel/80% polyester (electrode B) showed acceptable stability of electrode potentials, the stability of A was better than that of B. The electrode made of silver plated copper (electrode C) was less stable. The electrode impedance was lower for electrodes A and B than that for electrode C. From an electrical properties point of view we recommend to use electrodes of type A to be used in intelligent textile medical applications. © International Federation for Medical and Biological Engineering 2007.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-40953 (URN)10.1007/s11517-007-0266-y (DOI)54747 (Local ID)54747 (Archive number)54747 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    2. Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
    Open this publication in new window or tab >>Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
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    2013 (English)In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12Article in journal (Refereed) Published
    Abstract [en]

    Background

    ECG (Electrocardiogram) measurements in home health care demands new sensor solutions. In this study, six different configurations of screen printed conductive ink electrodes have been evaluated with respect to electrode potential variations and electrode impedance.

    Methods

    The electrode surfaces consisted of a Ag/AgCl-based ink with a conduction line of carbon or Ag-based ink underneath. On top, a lacquer layer was used to define the electrode area and to cover the conduction lines. Measurements were performed under well-defined electro-chemical conditions in a physiologic saline solution.

    Results

    The results showed that all printed electrodes were stable and have a very small potential drift (less than 3 mV/30 min). The contribution to the total impedance was 2% of the set maximal allowed impedance (maximally 1 kΩ at 50 Hz), assuming common values of input impedance and common mode rejection ratio of a regular amplifier.

    Conclusion

    Our conclusions are that the tested electrodes show satisfying properties to be used as elements in a skin electrode design that could be suitable for further investigations by applying the electrodes on the skin.

    Keywords
    Screen printed electrodes, ECG, Electrode impedance, Electrode potential, Smartware electrodes
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-96422 (URN)10.1186/1475-925X-12-64 (DOI)000321916300001 ()
    Note

    Funding Agencies|VINNOVA - Swedens Innovation Agency||NovaMedTech||Linkoping Initiative for Life Science Technologies (LIST)||

    Available from: 2013-08-20 Created: 2013-08-19 Last updated: 2017-12-06
    3. A Canonical correlation approach to heart beat detection in textile ECG measurements
    Open this publication in new window or tab >>A Canonical correlation approach to heart beat detection in textile ECG measurements
    Show others...
    2006 (English)In: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    Research in textile sensors has lead to new ways to measure electrocardiograms (ECG). However, additional disturbances from e.g. muscular noise and high skin-electrode impedances often result in poor signal quality. The paper contains a simple application of canonical correlation analysis (CCA) on multi channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intend to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to simple averaging of the ECG channels and to the independent component analysis method (ICA). A heart beat detector was used to evaluate the signal quality. Results show that the signal was completely lost while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

    Place, publisher, year, edition, pages
    IEEE, 2006
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-34459 (URN)21497 (Local ID)08-6341-658-6 (e-book) (ISBN)978-08-6341-658-3 (ISBN)21497 (Archive number)21497 (OAI)
    Conference
    3rd International Conference on Advances in Medical Signal and Information Processing : MEDSIP 2006, July 17-19, 2006, Glasgow, Scotland
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2015-03-20Bibliographically approved
    4. Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Open this publication in new window or tab >>Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Show others...
    2013 (English)In: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, no 1, p. 61-71Article in journal, Meeting abstract (Refereed) Published
    Abstract [en]

    The aim of this study was to develop and evaluate a robust heartbeat detector for noisy electrocardiograms (ECGs) recorded with textile electrodes. We suggest a method based on weighted correlation in a multi-channel ECG to obtain a heartbeat detector. Signals were acquired during rest and at movements which simulate every day activities. From each recording a segment corresponding to a heartbeat was extracted and correlated with the whole signal. From the correlation data, heartbeat candidates were derived and weighted based on their variance similarity with the heartbeat model and previous heartbeats. Finally, the outputs of each channel were added to create the global output. The output was compared to the Pan Tompkins heartbeat detector. Results are promising for recordings at rest (sensitivity = 0.97, positive predictive value (PPV) = 0.97). For static muscle tension in the torso the results were much higher than the reference method (sensitivity = 0.77, PPV = 0.85). Corresponding values for the reference method were sensitivity = 0.96 and PPV = 0.95 at rest and sensitivity = 0.52 and PPV = 0.75 during muscle tension.

    Place, publisher, year, edition, pages
    IGI Global, 2013
    Keywords
    textile electrodes, multichannel ecg, noise suppression, heartbeat detector
    National Category
    Other Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-79772 (URN)10.4018/jehmc.2013010106 (DOI)
    Conference
    8th International Conference on Wearable Micro and Nano Technologies for Personalized Health
    Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2015-03-20
    Download full text (pdf)
    Smartware electrodes for ECG measurements: Design, evaluation and signal processing
    Download (pdf)
    omslag
  • 225.
    Rattfält, Linda
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Textile electrodes for ECG measurements in distributed care, performance and applications2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis work has been to explore textile electrodes for electrocardiographic (ECG) measurements both in terms of their electrode properties and possibility to further improve their robustness to noise with signal processing techniques. Previous research within the field has shown that acquisition of ECG is possible with textile electrodes, but little attention has been focused on how they function and especially if movements are included in the measurement protocol.

    In a first study, the electrical properties of conductive textiles were evaluated in the same manner as conventional Ag/AgCl ECG electrodes. Three yarns and textile electrode surfaces were tested. The electrodes made from pure stainless steel (A) and 20% stainless steel/ 80% polyester (B) showed acceptable stability of electrode potentials. The electrode made from silver plated copper (C) was less robust. The best electrode impedance characteristic had Electrode A and hence from an electrical properties point of view we recommend electrodes of type A to be used for ECG measurements.

    The second paper contains an application of canonical correlation analysis (CCA) on multi channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intended to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to averaging of the ECG channels and to the independent component analysis method (ICA). Results show a loss of the ECG signal while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

    A drawback with the CCABSS approach is however that it produces many outputs and that information regarding the wanted feature to detect is not included in the analysis. In the third article, an event detector based on a multichannel input, a model of the event and weighted correlation was used instead. For measurements at rest and upper body rotation, the sensitivity was 100% and 99% respectively. Muscle tension and walking were the hardest to detect with a sensitivity of 88% and 91% respectively.

    List of papers
    1. Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Open this publication in new window or tab >>Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Show others...
    2007 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 12, p. 1251-1257Article in journal (Refereed) Published
    Abstract [en]

    Clothing with conductive textiles for health care applications has in the last decade been of an upcoming research interest. An advantage with the technique is its suitability in distributed and home health care. The present study investigates the electrical properties of conductive yarns and textile electrodes in contact with human skin, thus representing a real ECG-registration situation. The yarn measurements showed a pure resistive characteristic proportional to the length. The electrodes made of pure stainless steel (electrode A) and 20% stainless steel/80% polyester (electrode B) showed acceptable stability of electrode potentials, the stability of A was better than that of B. The electrode made of silver plated copper (electrode C) was less stable. The electrode impedance was lower for electrodes A and B than that for electrode C. From an electrical properties point of view we recommend to use electrodes of type A to be used in intelligent textile medical applications. © International Federation for Medical and Biological Engineering 2007.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-40953 (URN)10.1007/s11517-007-0266-y (DOI)54747 (Local ID)54747 (Archive number)54747 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    2. A Canonical correlation approach to heart beat detection in textile ECG measurements
    Open this publication in new window or tab >>A Canonical correlation approach to heart beat detection in textile ECG measurements
    Show others...
    2006 (English)In: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, p. 1-4Conference paper, Published paper (Refereed)
    Abstract [en]

    Research in textile sensors has lead to new ways to measure electrocardiograms (ECG). However, additional disturbances from e.g. muscular noise and high skin-electrode impedances often result in poor signal quality. The paper contains a simple application of canonical correlation analysis (CCA) on multi channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intend to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to simple averaging of the ECG channels and to the independent component analysis method (ICA). A heart beat detector was used to evaluate the signal quality. Results show that the signal was completely lost while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

    Place, publisher, year, edition, pages
    IEEE, 2006
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-34459 (URN)21497 (Local ID)08-6341-658-6 (e-book) (ISBN)978-08-6341-658-3 (ISBN)21497 (Archive number)21497 (OAI)
    Conference
    3rd International Conference on Advances in Medical Signal and Information Processing : MEDSIP 2006, July 17-19, 2006, Glasgow, Scotland
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2015-03-20Bibliographically approved
    3. Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Open this publication in new window or tab >>Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Show others...
    2013 (English)In: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, no 1, p. 61-71Article in journal, Meeting abstract (Refereed) Published
    Abstract [en]

    The aim of this study was to develop and evaluate a robust heartbeat detector for noisy electrocardiograms (ECGs) recorded with textile electrodes. We suggest a method based on weighted correlation in a multi-channel ECG to obtain a heartbeat detector. Signals were acquired during rest and at movements which simulate every day activities. From each recording a segment corresponding to a heartbeat was extracted and correlated with the whole signal. From the correlation data, heartbeat candidates were derived and weighted based on their variance similarity with the heartbeat model and previous heartbeats. Finally, the outputs of each channel were added to create the global output. The output was compared to the Pan Tompkins heartbeat detector. Results are promising for recordings at rest (sensitivity = 0.97, positive predictive value (PPV) = 0.97). For static muscle tension in the torso the results were much higher than the reference method (sensitivity = 0.77, PPV = 0.85). Corresponding values for the reference method were sensitivity = 0.96 and PPV = 0.95 at rest and sensitivity = 0.52 and PPV = 0.75 during muscle tension.

    Place, publisher, year, edition, pages
    IGI Global, 2013
    Keywords
    textile electrodes, multichannel ecg, noise suppression, heartbeat detector
    National Category
    Other Medical Engineering
    Identifiers
    urn:nbn:se:liu:diva-79772 (URN)10.4018/jehmc.2013010106 (DOI)
    Conference
    8th International Conference on Wearable Micro and Nano Technologies for Personalized Health
    Available from: 2012-08-14 Created: 2012-08-14 Last updated: 2015-03-20
    Download (jpg)
    presentationsbild
  • 226.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Ahlström, Christer
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Berglin, Lena
    The Swedish School of Textiles, University College of Borås, Borås, Sweden.
    Lindén, Maria
    Dept. of Computer Science and Electronics, Mälardalen University, Västerås, Sweden.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Wiklund, Urban
    Dept. of Biomedical Engineering & Informatics, Umeå University Hospital, Umeå, Sweden.
    A Canonical correlation approach to heart beat detection in textile ECG measurements2006In: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Research in textile sensors has lead to new ways to measure electrocardiograms (ECG). However, additional disturbances from e.g. muscular noise and high skin-electrode impedances often result in poor signal quality. The paper contains a simple application of canonical correlation analysis (CCA) on multi channel ECG signals recorded with textile electrodes. Using CCA to solve the blind source separation (BSS) problem, we intend to separate the ECG signal from the various noise sources. The method (CCABSS) was compared to simple averaging of the ECG channels and to the independent component analysis method (ICA). A heart beat detector was used to evaluate the signal quality. Results show that the signal was completely lost while simulating various noise in 33%, 17% and 7% of the cases for averaging, ICA and CCA, respectively.

  • 227.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Ahlström, Christer
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Eneling, Martin
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Ragnemalm, Bengt
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Hult, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Lindén, M.
    Intelligent Sensor Systems, Mälardalen University, Västerås, Sweden.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    A platform for physiological signals including an intelligent stethoscope2009In: 4th European Conference of the International Federation for Medical and Biological Engineering: ECIFMBE 2008 23–27 November 2008 Antwerp, Belgium / [ed] Jos Sloten, Pascal Verdonck, Marc Nyssen, Jens Haueisen, Springer Berlin/Heidelberg, 2009, Vol. 22, p. 1038-1041Chapter in book (Refereed)
    Abstract [en]

    We have developed a physiological signal platform where presently phonocardiographic (PCG) and electrocardiographic (ECG) signals can be acquired and on which our signal analysis techniques can be implemented. The platform can also be used to store patient data, to enable comparison over time and invoke distance consultation if necessary. Our studies so far indicate that with our signal analysis techniques of heart sounds we are able to separate normal subject from those with aortic stenosis and mitral insufficiency. Further we are able to identify the third heart sound. The platform is being tested in a primary health care setting.

  • 228.
    Rattfält, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Alod, Tanja
    Hult, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Den textila elektrodens utformning - En studie i hur designparametrar inverkar på signalkvaliteten i EKG-mätningar2006In: Medicinteknikdagarna 06,2006, 2006Conference paper (Other academic)
  • 229.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    Alod, Tanja
    Linköping University, Department of Biomedical Engineering.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    The Textile Electrode Configuration - How signal quality in ECG-measurements is affected by design parameters. (Poster)2006Conference paper (Other academic)
  • 230.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Bjorefors, F.
    Dept of Materials Chemistry, Uppsala Universitet, Sweden.
    Wang, X.
    Acreo, Norrköping, Sweden.
    Nilsson, D.
    Acreo, Norrköping, Sweden.
    Norberg, P.
    Acreo, Norrköping, Sweden.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Electrical Characterization of Screen Printed Electrodes for ECG Measurements2011In: Mediterranean conference on medical and biological engineering and computing 2013 / [ed] Roa Romero, Laura M., Springer Berlin/Heidelberg, 2011, Vol. 34, no 2011, p. 219-221Chapter in book (Refereed)
    Abstract [en]

    Screen printed electrodes with conductive ink made of Carbon and Ag/AgCl were tested for polarization potentials and electrode impedances. In 30 minutes the mean decrease of polarization potential was 2 mV. The electrode impedances at 10 Hz were between 670 and 250 Ohms. These characteristics seem adequate for personalized health care applications.

  • 231.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Bjorefors, Fredrik
    Department of Materials Chemistry, Uppsala, Sweden.
    Nilsson, David
    Acreo AB, Norrköping, Sweden.
    Wang, Xin
    Acreo AB, Norrköping, Sweden.
    Norberg, Petronella
    Acreo AB, Norrköping, Sweden.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell2013In: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12Article in journal (Refereed)
    Abstract [en]

    Background

    ECG (Electrocardiogram) measurements in home health care demands new sensor solutions. In this study, six different configurations of screen printed conductive ink electrodes have been evaluated with respect to electrode potential variations and electrode impedance.

    Methods

    The electrode surfaces consisted of a Ag/AgCl-based ink with a conduction line of carbon or Ag-based ink underneath. On top, a lacquer layer was used to define the electrode area and to cover the conduction lines. Measurements were performed under well-defined electro-chemical conditions in a physiologic saline solution.

    Results

    The results showed that all printed electrodes were stable and have a very small potential drift (less than 3 mV/30 min). The contribution to the total impedance was 2% of the set maximal allowed impedance (maximally 1 kΩ at 50 Hz), assuming common values of input impedance and common mode rejection ratio of a regular amplifier.

    Conclusion

    Our conclusions are that the tested electrodes show satisfying properties to be used as elements in a skin electrode design that could be suitable for further investigations by applying the electrodes on the skin.

    Download full text (pdf)
    fulltext
  • 232.
    Rattfält, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Chedid, Michel
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Tillverkningsmetodens inverkan på elektriska egenskaper hos textila elektroder.2007In: Posterpresentation på Medecinteknikdagarna, Conventum,2007, 2007Conference paper (Other academic)
    Abstract [en]

      

  • 233.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Chedid, Michel
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Lindén, Maria
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Electrical Properties of Textile Electrodes2007In: Engineering in Medicine and Biology Society, 2007. EMBS 2007, IEEE , 2007, p. 5735-5738Conference paper (Refereed)
    Abstract [en]

    In this study we aim to explain the behavior of textile electrodes due to their construction techniques. Three textile electrodes were tested for electrode impedance and polarization potentials. The multifilament yarn (A) is favorable for its low thread resistance. Although, when knitted into electrodes, the staple fiber yarn (B) showed a comparable and satisfiable electrode impedance. The multifilament yarn had however a lower polarization potential drift then the other specimens. The monofilament yarn (C) had high electrode impedance and varying mean polarization potentials due to its conductive material and small contact area with the skin.

  • 234.
    Rattfält, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Hagström, Caroline
    Medicinsk teknik Örebro universitet.
    Lindén, Maria
    Inst för Datavetenskap och elektronik Mälardalens Högskola.
    Hult, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Implementations of a technical system in distributed care - attitudes and possibilies2005In: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, p. 50-Conference paper (Refereed)
  • 235.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Faculty of Science & Engineering.
    A platform for physiological signals including an intelligent stethoscope.2008Conference paper (Other academic)
  • 236.
    Rattfält, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Hult, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Lindén, Maria
    Mälardalens Högskola Västerås.
    Hagström, Caroline
    Medicinsk teknik Örebro Läns Landsting.
    Berglin, Lena
    Textilhögskolan,Borås .
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kroppsnära multisensorer och smarta textiplagg för vård och övervakning i hemmet.2005In: Läkarsällskapets Riksstämma 2005,2005, 2005Conference paper (Other academic)
  • 237.
    Rattfält, Linda
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Lindén, Maria
    Mälardalen University.
    Hult, Peter
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes2013In: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, no 1, p. 61-71Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop and evaluate a robust heartbeat detector for noisy electrocardiograms (ECGs) recorded with textile electrodes. We suggest a method based on weighted correlation in a multi-channel ECG to obtain a heartbeat detector. Signals were acquired during rest and at movements which simulate every day activities. From each recording a segment corresponding to a heartbeat was extracted and correlated with the whole signal. From the correlation data, heartbeat candidates were derived and weighted based on their variance similarity with the heartbeat model and previous heartbeats. Finally, the outputs of each channel were added to create the global output. The output was compared to the Pan Tompkins heartbeat detector. Results are promising for recordings at rest (sensitivity = 0.97, positive predictive value (PPV) = 0.97). For static muscle tension in the torso the results were much higher than the reference method (sensitivity = 0.77, PPV = 0.85). Corresponding values for the reference method were sensitivity = 0.96 and PPV = 0.95 at rest and sensitivity = 0.52 and PPV = 0.75 during muscle tension.

  • 238.
    Rattfält, Linda
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Lindén, Maria
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Hult, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Berglin, Lena
    Data- och informationsteknik Göteborgs universitet.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Electrical characteristics of conductive yarns and textile electrodes for medical applications2007In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 12, p. 1251-1257Article in journal (Refereed)
    Abstract [en]

    Clothing with conductive textiles for health care applications has in the last decade been of an upcoming research interest. An advantage with the technique is its suitability in distributed and home health care. The present study investigates the electrical properties of conductive yarns and textile electrodes in contact with human skin, thus representing a real ECG-registration situation. The yarn measurements showed a pure resistive characteristic proportional to the length. The electrodes made of pure stainless steel (electrode A) and 20% stainless steel/80% polyester (electrode B) showed acceptable stability of electrode potentials, the stability of A was better than that of B. The electrode made of silver plated copper (electrode C) was less stable. The electrode impedance was lower for electrodes A and B than that for electrode C. From an electrical properties point of view we recommend to use electrodes of type A to be used in intelligent textile medical applications. © International Federation for Medical and Biological Engineering 2007.

  • 239.
    Ressner, Marcus
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    On Nonlinear Acoustics in Contrast Echocardiography2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ultrasound is one of the most commonly used noninvasive medical imaging techniques. Ultrasound contrast agents (UCA), consisting of encapsulated gas-filled microbubbles, have shown to increase the diagnostic precision in selected low echogenic patients. UCA also holds promise for bedside evaluation of myocardial perfusion quantification, but is not yet reproducible and specific enough for clinical use. In addition risks have been addressed when used, as first recommended, together with high mechanical index (MI) for reperfusion assessment by contrast destruction. We clinically observed increased myocardial velocities after UCA-administration when applied simultaneously with color tissue Doppler imaging (CTDI) arising the question if this increase was due to physiological factors or physical changes in the backscattered signals when UCA were present.

    The aims of the thesis was to explain this velocity shift and simultaneously to contribute to a future safe and contrast specific application by further characterizing the non-linear acoustic properties of UCA when located in an acoustic field. Of specific interest was to evaluate in which way nonlinear wave propagation affects the response from UCA and if a change in pulse shape, length or polarity can be utilized to increase the nonlinear signal contribution.

    Twelve patients with ischemic heart disease were examined with CTDI before and after UCA-administration in order to verify the change in peak systolic velocity. An experimental in vitro model including flow and tissue phantoms for UCA was established for CTDI. Raw data from single-element transducers and clinical ultrasound systems were collected for three different UCA and analyzed to determine if the observed velocity shift could be reproduced in vitro and to find a possible cause. Our results show in vivo and in vitro that UCA will affect the autocorrelation phase shift estimator used for CTDI in terms of contribution from rupturing UCA microbubbles, which explains the velocity shift. CTDI during contrast infusion should therefore be avoided unless it can be performed at low MI where the majority of the UCA are intact.

    The computational model for spatial superposition of attenuated waves was modified to include an operator for pulse distortion from nonlinear wave propagation. The Matlab™ toolbox Bubblesim based on a modified Rayleigh-Plesset-equation and with insonation parameters such as frequency, pressure amplitude, pulse length and polarity was used to study the response from single microbubbles either for simulated pulses or for pulses generated by clinical ultrasound systems and single element transducers. The combination of the two models also provided a computational platform to asses pulse distortion from nonlinear wave propagation, the response of the UCA bubble and the linear backscatter of the low amplitude bubble echo. When evaluating the harmonic response in simulations and in vitro, the interaction of the excitation pulses with the contrast bubbles was identified as the main cause of nonlinear scattering, and a 2-3 dB increase of the second harmonic amplitude depends on nonlinear distortions of the incident pulse. By applying small changes of short (<3.5 cycles) and fragmented transmitted wideband pulses of 2-2.5 MHz, it is shown that inverted pulse polarity considerably modulates power without affecting a low and safe MI (<0.4), and the results lodged promise to further to enhance a contrast response.

    List of papers
    1. Effects of ultrasound contrast agents on doppler tissue velocity estimation
    Open this publication in new window or tab >>Effects of ultrasound contrast agents on doppler tissue velocity estimation
    Show others...
    2006 (English)In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 19, no 2, p. 154-164Article in journal (Refereed) Published
    Abstract [en]

    The combination of Doppler tissue imaging and myocardial contrast echocardiography has the potential to provide information about motion and perfusion of the myocardium in a single examination. The purpose of this study was to establish how the presence of ultrasound contrast agent (UCA) affects measurements of Doppler tissue velocities in vivo and in vitro. We performed echocardiography in 12 patients with ischemic heart disease before and immediately after a slow intravenous infusion of the UCA Optison, using color Doppler tissue imaging to examine the effect of contrast agents in vivo. The myocardial peak systolic velocities and their integrals were analyzed in digitally stored cineloops before and after contrast administration. To distinguish between methodologic and physiologic factors affecting the measurement of tissue velocity in vitro, experiments with a rotating disk and a flow cone phantom were also carried out for the 3 contrast agents: Optison, Sonovue, and Sonazoid. In vivo results show that the values for peak systolic velocity increased by about 10% during contrast infusion, from mean 5.2 ± 1.8 to 5.7 ± 2.3 cm/s (P = .02, 95% confidence interval 2%-16%). The increase in myocardial peak systolic velocities was verified in experimental models in which the UCA increased the estimated mean velocity in the order of 5% to 20% for the motion interval of 5 to 7 cm/s, corresponding to the myocardial velocities studied in vivo. The response was similar for all 3 contrast agents and was not affected by moderate variations in concentration of the agent. We have shown that the presence UCA will affect Doppler tissue measurements in vivo and in vitro. The observed bias is presumed to be an effect of harmonic signal contribution from rupturing contrast agent microbubbles and does not indicate biologic or physiologic effects. Copyright 2006 by the American Society of Echocardiography.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-28716 (URN)10.1016/j.echo.2005.09.025 (DOI)13885 (Local ID)13885 (Archive number)13885 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    2. Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging
    Open this publication in new window or tab >>Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging
    Show others...
    2009 (English)In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 3, p. 447-457Article in journal (Refereed) Published
    Abstract [en]

    Quantitative assessment of regional myocardial function at rest and during stress with Doppler tissue imaging (DTI) plays an important role in daily routine echocardiography. However, reliable visual analysis is largely dependent on image quality and adequate border delineation, which still remains a challenge in a significant number of patients. In this respect, an ultrasound contrast agent (UCA) is often used to improve visualization in patients with suboptimal image quality. The knowledge of how DTI measurements will be affected by UCA present in the tissue is therefore of significant importance for an accurate interpretation of local myocardial motion. The aim of this paper was to investigate how signal contribution from UCA and nonlinear wave propagation influence the performance of the autocorrelation phase shift estimator used for DTI applications. Our results are based on model experiments with a clinical 2-D grayscale scanner and computational simulations or the DTI velocity estimator for synthetically-derived pulses, simulated bubble echoes and experimentally-sampled RF data of transmitted pulses and backscattered contrast echoes. The results show that destruction of UCA present in the tissue will give rise to an apparent bidirectional velocity bias of individual velocity estimates, but that spatial averaging of individual velocity measurements within a region-of-interest will result in a negative bias (away from the transducer) of the estimated mean or mean peak velocity. The UCA destruction will also have a significant impact on the measured integrated mean velocity over time, i.e., displacement. To achieve improved visualization with UCA during DTI-examinations, we either recommend that it is performed at low acoustic powers, mechanical index <= 0.3, thereby minimizing the effects from bubble rupture, or that each Doppler pulse package is preceded by a destruction burst similar to "Flash imaging" to clear the target area of contrast microbubbles.

    Keywords
    Ultrasound, Tissue Doppler, Contrast, Microbubbles, Velocity estimation
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-17277 (URN)10.1016/j.ultrasmedbio.2008.09.012 (DOI)
    Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2017-12-13
    3. Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment
    Open this publication in new window or tab >>Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment
    Show others...
    2004 (English)In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, no 01-Sep, p. 301-307Article in journal (Refereed) Published
    Abstract [en]

    The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse. (C) 2004 Elsevier B.V. All rights reserved.

    Keywords
    ultrasound, simulation, nonlinear, contrast agents
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-46245 (URN)10.1016/j.ultras.2004.01.023 (DOI)
    Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
    4. Ultrasound contrast response to variation of incident pulse length and polarity
    Open this publication in new window or tab >>Ultrasound contrast response to variation of incident pulse length and polarity
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Microbubbles are used as ultrasound contrast agents (UCA) in diagnostic ultrasound as they considerably enhance the backscattered signal and generate specific signal characteristics that can be used to isolate echoes that originate from the blood volume. Emerging new advanced contrast specific insonation techniques have shown to better discriminate the backscattered UCA-signal but has not gained clinical practice due to their complexity and the need for additional soft- and hardware, or due to the debated safety aspects regarding microbubble cavitation at mechanical index (MI >>0.4). In this study we investigate a simplified approach to improve the nonlinear signal contribution from UCA at low MI < 0.4 by utilizing the asymmetry between positive and negative peak pressures for pulse lengths ≤3.5 cycles. In vitro registrations of the transmitted pulse peak pressure asymmetry from a single element transducer were obtained with a needle hydrophone after a transducer excitation pulse with increasing length from 0.5 to 5 cycles. A computational model (Bubblesim) was used to investigate the response from a single microbubble after interaction with transmitted pulse with variations of length, shape and polarity. Our results show that small changes (quarters of a pulse cycle) will change the transmitted pulse shape and distribution of peak pressures and that this effect can be used to change the scattering behavior of UCA in simulations and in vitro. This effect will increase with decreasing pulse lengths <5 cycles. The best case scenario for differentiation of harmonic UCA response with polarity change at MI <0.4 and real time imaging can for transducer frequencies of 2-2.5 MHz be found for pulse lengths of 2.25 and 2.75 cycles in the acoustic pressure interval of 300-500 kPa.

    Keywords
    Ultrasound contrast agents, nonlinear imaging, harmonic imaging, contrast echocardiography
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-65417 (URN)
    Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2011-02-07
    Download (pdf)
    COVER01
  • 240.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Brodin, Lars-Åke
    The Royal Institute of Technology, Stockholm, Sweden.
    Jansson, Tomas
    Lund Institute of Technology, Lund, Sweden.
    Hoff, Lars
    Vestfold University College, Noway.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Janerot-Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Effects of ultrasound contrast agents on doppler tissue velocity estimation2006In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 19, no 2, p. 154-164Article in journal (Refereed)
    Abstract [en]

    The combination of Doppler tissue imaging and myocardial contrast echocardiography has the potential to provide information about motion and perfusion of the myocardium in a single examination. The purpose of this study was to establish how the presence of ultrasound contrast agent (UCA) affects measurements of Doppler tissue velocities in vivo and in vitro. We performed echocardiography in 12 patients with ischemic heart disease before and immediately after a slow intravenous infusion of the UCA Optison, using color Doppler tissue imaging to examine the effect of contrast agents in vivo. The myocardial peak systolic velocities and their integrals were analyzed in digitally stored cineloops before and after contrast administration. To distinguish between methodologic and physiologic factors affecting the measurement of tissue velocity in vitro, experiments with a rotating disk and a flow cone phantom were also carried out for the 3 contrast agents: Optison, Sonovue, and Sonazoid. In vivo results show that the values for peak systolic velocity increased by about 10% during contrast infusion, from mean 5.2 ± 1.8 to 5.7 ± 2.3 cm/s (P = .02, 95% confidence interval 2%-16%). The increase in myocardial peak systolic velocities was verified in experimental models in which the UCA increased the estimated mean velocity in the order of 5% to 20% for the motion interval of 5 to 7 cm/s, corresponding to the myocardial velocities studied in vivo. The response was similar for all 3 contrast agents and was not affected by moderate variations in concentration of the agent. We have shown that the presence UCA will affect Doppler tissue measurements in vivo and in vitro. The observed bias is presumed to be an effect of harmonic signal contribution from rupturing contrast agent microbubbles and does not indicate biologic or physiologic effects. Copyright 2006 by the American Society of Echocardiography.

  • 241.
    Ressner, Marcus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Brodin, Lars-Åke
    Jansson, Tomas
    Dept of Electrical Measurements Lund University.
    Hoff, Lars
    Faculty of Science and Engineering Vestfold University, Horten, Norge.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Janerot-Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Effekter av ultraljudskontrast vid hastighetsestimering med vävnadsdoppler2005In: Svenska Läkaresällskapets Riksstämma 2005,2005, 2005Conference paper (Other academic)
  • 242.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Brodin, L-Å.
    Jansson, Tomas
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Janerot-Sjöberg, Birgitta
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    How Ultrasound Contrast Agents effects Doppler Tissue Velocity Estimation2006Conference paper (Other academic)
  • 243.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Gustafsson, Disa
    Karolinska Institutet, Stockholm.
    Gustafsson, Agnetha
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL.
    Jonsson, Cathrine
    Karolinska universitetssjukhuset Solna, Stockholm.
    Experimental evaluation of iterative reconstruction for whole-body F-18 PET in a 3- and 4-ring PET/CT system2011Conference paper (Other academic)
  • 244.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Jansson, Tomas
    Lund University.
    Cedefamn, Jonny
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Janerot Sjöberg, Birgitta
    Linköping University, Department of Medicine and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging2009In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 3, p. 447-457Article in journal (Refereed)
    Abstract [en]

    Quantitative assessment of regional myocardial function at rest and during stress with Doppler tissue imaging (DTI) plays an important role in daily routine echocardiography. However, reliable visual analysis is largely dependent on image quality and adequate border delineation, which still remains a challenge in a significant number of patients. In this respect, an ultrasound contrast agent (UCA) is often used to improve visualization in patients with suboptimal image quality. The knowledge of how DTI measurements will be affected by UCA present in the tissue is therefore of significant importance for an accurate interpretation of local myocardial motion. The aim of this paper was to investigate how signal contribution from UCA and nonlinear wave propagation influence the performance of the autocorrelation phase shift estimator used for DTI applications. Our results are based on model experiments with a clinical 2-D grayscale scanner and computational simulations or the DTI velocity estimator for synthetically-derived pulses, simulated bubble echoes and experimentally-sampled RF data of transmitted pulses and backscattered contrast echoes. The results show that destruction of UCA present in the tissue will give rise to an apparent bidirectional velocity bias of individual velocity estimates, but that spatial averaging of individual velocity measurements within a region-of-interest will result in a negative bias (away from the transducer) of the estimated mean or mean peak velocity. The UCA destruction will also have a significant impact on the measured integrated mean velocity over time, i.e., displacement. To achieve improved visualization with UCA during DTI-examinations, we either recommend that it is performed at low acoustic powers, mechanical index <= 0.3, thereby minimizing the effects from bubble rupture, or that each Doppler pulse package is preceded by a destruction burst similar to "Flash imaging" to clear the target area of contrast microbubbles.

  • 245.
    Ressner, Marcus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kvikliene, Adriana
    Kaunas University of Technology.
    Hoff, Lars
    Westfold University College.
    Jurkonis, Rytis
    Kaunas University of Technology.
    Jansson, Tomas
    Lunds universitet.
    Janerot-Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lukosevicius, Arunas
    Kaunas University of Technology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Backscattered ultrasound from contrast microbubbles: effects of tissue and bubble interaction2004In: EMBS,2004, San Francisco: IEEE , 2004, p. 849-Conference paper (Refereed)
  • 246.
    Ressner, Marcus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kvikliene, Adriana
    Inst of Biomedical Engineering Kaunas University of Technology,Lithuania.
    Hoff, Lars
    Faculty ofScience and Engineering Vestfold University, Horten, Norge.
    Jurkonis, Rytis
    Inst of Biomedical Engineering Kaunas University of Technology, Lithuania.
    Jansson, Tomas
    Dept of Electrical Measurements Lunds universitet.
    Janerot-Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lukosevicius, Arunas
    Inst of Biomedical Engineering Kaunas University of Technology, Lithuania.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Ultrasound contrast for perfusion studies2005In: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, p. 107-Conference paper (Refereed)
  • 247.
    Ressner, Marcus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Kvikliene, Adriana
    Kaunas University of Technology .
    Hoff, Lars
    Vestfold University, Horten Norge.
    Jurkonis, Rytis
    Kaunas University of Technology .
    Jansson, Tomas
    Lund University .
    Janerot-Sjöberg, Birgitta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lukosevicius, Arunas
    Kaunas University of Technology .
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Ultrasound contrast microbubbles: simulations and in vitro experiments2005In: EMBEC05,2005, Prag: IFMBE , 2005Conference paper (Refereed)
  • 248.
    Ressner, Marcus
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Kviklienė, Adriana
    Institute of Biomedical Engineering, Kaunas University of Technology, Kaunas LT-3006, Lithuania.
    Jansson, Tomas
    Department of Electrical Measurements, Lund University, SE-22100 Lund, Sweden.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Janerot‐Sjoberg, Birgitta
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Ultrasound contrast response to variation of incident pulse length and polarityManuscript (preprint) (Other academic)
    Abstract [en]

    Microbubbles are used as ultrasound contrast agents (UCA) in diagnostic ultrasound as they considerably enhance the backscattered signal and generate specific signal characteristics that can be used to isolate echoes that originate from the blood volume. Emerging new advanced contrast specific insonation techniques have shown to better discriminate the backscattered UCA-signal but has not gained clinical practice due to their complexity and the need for additional soft- and hardware, or due to the debated safety aspects regarding microbubble cavitation at mechanical index (MI >>0.4). In this study we investigate a simplified approach to improve the nonlinear signal contribution from UCA at low MI < 0.4 by utilizing the asymmetry between positive and negative peak pressures for pulse lengths ≤3.5 cycles. In vitro registrations of the transmitted pulse peak pressure asymmetry from a single element transducer were obtained with a needle hydrophone after a transducer excitation pulse with increasing length from 0.5 to 5 cycles. A computational model (Bubblesim) was used to investigate the response from a single microbubble after interaction with transmitted pulse with variations of length, shape and polarity. Our results show that small changes (quarters of a pulse cycle) will change the transmitted pulse shape and distribution of peak pressures and that this effect can be used to change the scattering behavior of UCA in simulations and in vitro. This effect will increase with decreasing pulse lengths <5 cycles. The best case scenario for differentiation of harmonic UCA response with polarity change at MI <0.4 and real time imaging can for transducer frequencies of 2-2.5 MHz be found for pulse lengths of 2.25 and 2.75 cycles in the acoustic pressure interval of 300-500 kPa.

  • 249.
    Roback, Kerstin
    et al.
    Linköping University, Department of Medicine and Health Sciences, Health Technology Assessment. Linköping University, The Institute of Technology.
    Nelson, Nina
    Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Linköping University, Faculty of Health Sciences.
    Johansson, Anders
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hass, Ursula
    Linköping University, Department of Medicine and Health Sciences, Health Technology Assessment. Linköping University, The Institute of Technology.
    Strömberg, Tomas
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A New Fiberoptical Respiratory Rate Monitor for the Neonatal Intensive Care Unit2005In: Pediatric Pulmonology, ISSN 8755-6863, Vol. 39, no 2, p. 120-126Article in journal (Refereed)
    Abstract [en]

    A new technique for respiratory rate measurement in the neonatal intensive care unit, fiberoptic respirometry (FORE), was tested using a specially designed nasal adapter. The aim was to investigate the system's accuracy and compare it to the transthoracic impedance (TTI) method and manual counting (MC). Further, the relationship between accuracy and degree of body movement was investigated. Seventeen neonates of median gestational age 35 weeks were included in the study. Video recordings (synchronized with data recordings) were used for classification of body movement. Breaths per minute data were obtained for 23-32-min periods per child, and a subset of these included MC performed by experienced nurses. A Bland-Altman analysis showed low accuracy of both FORE and TTI. A >20% deviation from MC was found in 22.7% and 23.8% of observations for the two methods, respectively. Both methods had accuracy problems during body movement. FORE tended to underestimate respiratory rate due to probe displacement, while TTI overestimated due to motion artefacts. The accuracy was also strongly subject-dependent. The neonates were undisturbed by the FORE device. In some cases, though, it was difficult to keep the adapter positioned in the airway. Further development should, therefore, focus on FORE adapter improvements to maintain probe position over time.

  • 250.
    Rovai, Daniele
    et al.
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Janerot-Sjöberg, Birgitta
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL.
    Nagy, András
    Gottsegen György Hungarian Institute of Cardiology, Budapest, Hungary.
    Marini, Cecilia
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Burchielli, Silvia
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Castellari, Michele
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Morales, Maria-Aurora
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Trivella, M. Giovanna
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Ostensen, Jonny
    Nycomed Imaging AS, Oslo, Norway.
    Distante, Allessandro
    University of Pisa, Pisa, Italy.
    L'Abbate, Antonio
    CNR, Institute of Clinical Physiology, Pisa, Italy.
    Myocardial perfusion abnormalities by intravenous administration of the contrast agent NC100100 in an experimental model of coronary artery occlusion and reperfusion1998In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 15, no 8, p. 731-740Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate a second-generation echo contrast agent (NC100100) for the study of myocardial perfusion. In eight anesthetized open-chest dogs, this agent was injected intravenously under baseline conditions, during acute coronary thrombosis, and after reperfusion, using both fundamental (FI) and harmonic (HI) imaging, both continuous and intermittent imaging, and both ultrasound (US) and integrated backscatter (IBS) imaging. Contrast injections did not modify the hemodynamic parameters. With all imaging modalities, myocardial contrast enhancement (MCE) was higher with intermittent than with continuous imaging (134 vs 82 gray level/pixel using FI, P = 0.02; 62 vs 32 acoustic units using US HI, P = 0.02; and 52 vs 12 dB using IBS, P = 0.05). MCE equally increased using either US or IBS imaging. The accuracy of MCE in detecting perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis was very good (sensitivity and specificity = 93% and 95% and 89% and 93%, respectively). The extent of myocardial perfusion defects by echo contrast showed a closer correlation with microspheres using HI (r = 0.82) than FI (r = 0.53). Thus, the intravenous administration of NC100100 during intermittent HI allows myocardial perfusion abnormalities to be accurately detected during acute myocardial infarction.

234567 201 - 250 of 341
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