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  • 201.
    Nilsson, Gert
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Salerud, Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Tenland, T.
    Wahlberg, J.E.
    Öberg, Åke
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Laser Doppler Flowmetry A New Technique for Noninvasive Assessment of Skin Blood Flow.1983Ingår i: Cosmetics and toiletries, ISSN 0361-4387, Vol. 99, nr 3, s. 97-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

      

  • 202.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Salerud, Göran
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Tenland, T.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Biomedical Applications of Laser-Light Scattering1982Ingår i: Biomedical Applications of Laser-Light Scattering / [ed] David B. Sattelle, Amsterdam: Elsevier Biomedical press , 1982, s. 335-348Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 203.
    Nilsson, Gert
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Salerud, Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Tenland, Torsten
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Öberg, Åke
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    The use of Laser Doppler flowmetry in microvascular research1981Ingår i: International vascular symposium,1981, 1981Konferensbidrag (Övrigt vetenskapligt)
  • 204.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem i: Styrd värmedyna för kliniskt bruk1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 205.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem II: En överblick över medicintekniska säkerhetsfrågor1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 206.
    Nilsson, Gert
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Elektriska säkerhetsproblem III: Referenslista1974Rapport (Övrig (populärvetenskap, debatt, mm))
  • 207.
    Nilsson, Lena
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Anestesiologi med intensivvård. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    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
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Combined photoplethysmographic monitoring of respiration rate and pulse: A comparison between different measurement sites in spontaneously breathing subjects2007Ingår i: Acta Anaesthesiologica Scandinavica, ISSN 0001-5172, E-ISSN 1399-6576, Vol. 51, nr 9, s. 1250-1257Artikel i tidskrift (Refereegranskat)
    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.

  • 208.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Goscinski, Tomas
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi.
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Lindberg, Lars-Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Detection of breaths by photoplethysmography is independent of age and sex2005Ingår i: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, s. 19-Konferensbidrag (Refereegranskat)
  • 209.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Goscinski, Tomas
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi.
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Lindberg, Lars-Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Photoplethysmography for central and obstructive apnea detection2005Ingår i: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, s. 19-Konferensbidrag (Refereegranskat)
  • 210.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Goscinski, Tomas
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi.
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Lindberg, Lars-Göran
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Time relation between respiratory signals can be analysed by automated algorithms2005Ingår i: Congress of the Scandinavian Society of Anaesthesiology and intensive care,2005, 2005, s. 19-Konferensbidrag (Refereegranskat)
  • 211.
    Nilsson, Lena
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Anestesiologi med intensivvård. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Sinnescentrum, Anestesi- och intensivvårdskliniken US. Östergötlands Läns Landsting, Anestesi- och operationscentrum.
    Goscinski, Tomas
    Linköpings universitet, Institutionen för medicin och hälsa, Farmakologi. Linköpings universitet, Hälsouniversitetet.
    Lindenberger, Marcus
    Linköpings universitet, Institutionen för medicin och hälsa, Fysiologi. Linköpings universitet, Hälsouniversitetet.
    Länne, Toste
    Linköpings universitet, Institutionen för medicin och hälsa, Fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Johansson, Anders
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Respiratory variations in the photoplethysmographic waveform: acute hypovolaemia during spontaneous breathing is not detected2010Ingår i: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 31, nr 7, s. 953-962Artikel i tidskrift (Refereegranskat)
    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.

  • 212.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Den andningssynkrona kompenenten av den fotopletysmorgrafiska signalen hos sövda påverkas inte av övertrycksandning2004Ingår i: Programbok SFAI-veckan 2004,2004, 2004, s. 149-19Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

       

  • 213.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    The phase of the respiratory variation in the photoplethysmographic signal is not affected by sympathetic tone2004Ingår i: European Journal of Anaesthesiology, ISSN 0265-0215, E-ISSN 1365-2346, Vol. 21, s. 76-77Artikel i tidskrift (Refereegranskat)
  • 214.
    Nilsson, Lena
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Johansson, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Svanerudh, Johan
    Kalman, Sigga
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Anestesi- och intensivvårdskliniken VIN.
    Is the respiratory component of the photoplethysmographic signal of venous origin?1999Ingår i: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 37, s. 912-913Artikel i tidskrift (Refereegranskat)
  • 215.
    Norén, Bengt
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Wirell, Staffan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi.
    Almer, Sven
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för molekylär och klinisk medicin, Gastroenterologi och hepatologi. Östergötlands Läns Landsting, Medicincentrum, Endokrin- och magtarmmedicinska kliniken US.
    Smedby, Örjan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Medicinsk radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease2005Ingår i: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 15, nr 1, s. 148-157Artikel i tidskrift (Refereegranskat)
    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.

  • 216.
    Norén, Bengt
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US.
    Smedby, Örjan
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiologi. Östergötlands Läns Landsting, Bildmedicinskt centrum, Avdelningen för radiologi US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Lundberg, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Radiofysik. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Radiofysikavdelningen. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Quantification of liver metabolites with phosphorus-31 Magnetic Resonance Spectroscopy2002Ingår i: European Congress of Radiology March 1-5, 2002,2002, 2002, s. 353-353Konferensbidrag (Refereegranskat)
  • 217.
    Olsson, E
    et al.
    Uppsala Universitet .
    Ugnell, Håkan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Photoplethysmography for simultaneous recording of heart and respiratory rates in new born infants2000Ingår i: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 89, s. 853-861Artikel i tidskrift (Refereegranskat)
  • 218. Olsson, E
    et al.
    Ugnell, Håkan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Photoplethysmography for surveillance of circulation and respiration in newborn infants2000Ingår i: International Conference on Fetal and Neonatal Physiological Measurements,2000, 2000Konferensbidrag (Övrigt vetenskapligt)
  • 219. Palmerud, P.
    et al.
    Zhang, Q.
    Forsman, M.
    Lindberg, Lars-Göran
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Non-invasive photoplethysmography for muscle blood flow assessment in ergonomic applications2010Ingår i: European Journal of Applied Physiology, ISSN 1439-6319Artikel i tidskrift (Refereegranskat)
  • 220.
    Pettersson, Hans
    et al.
    IMT LiU.
    Stenow, Erik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Cai, Hongming
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Öberg, Åke
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Optical aspects of a fibre-optic sensor for respiratory rate monitoring1996Ingår i: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 34, s. 448-452Artikel i tidskrift (Refereegranskat)
  • 221.
    Pettersson, Nils-Erik
    et al.
    Örebro läns landsting.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Ekstrand, Kristina
    Katrineholms kommun.
    Hult, peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Lindén, Maria
    Mälardalen University Sweden.
    NovaMedTech – En satsning på att ny medicinsk teknik i Östra Mellansverige2010Konferensbidrag (Övrigt vetenskapligt)
  • 222.
    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
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Temitski, Kristina
    Tallinn University of Technology, Estonia .
    Viigimaa, Margus
    Tallinn University of Technology, Estonia .
    New Photoplethysmographic Signal Analysis Algorithm for Arterial Stiffness Estimation2013Ingår i: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, Vol. 2013Artikel i tidskrift (Refereegranskat)
    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.

  • 223.
    Pope, C E
    et al.
    University of Washington.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Tibbling, Lita
    Evaluation of intraluminal EMG electrodes for the oesophagus and gastrointestinal tract.1984Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 22, nr 5, s. 461-464Artikel i tidskrift (Refereegranskat)
  • 224. POPE, CE
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    DEBLAN, H
    WINGATE, DL
    MEASUREMENT OF INSTANTANEOUS FLOW VELOCITY IN THE HUMAN GASTROINTESTINAL-TRACT1988Ingår i: Gastroenterology, ISSN 0016-5085, E-ISSN 1528-0012, Vol. 95, nr 3Artikel i tidskrift (Refereegranskat)
  • 225.
    Rattfält, Linda
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Smartware electrodes for ECG measurements: Design, evaluation and signal processing2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

     

    Delarbeten
    1. Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Öppna denna publikation i ny flik eller fönster >>Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Visa övriga...
    2007 (Engelska)Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, nr 12, s. 1251-1257Artikel i tidskrift (Refereegranskat) 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.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-40953 (URN)10.1007/s11517-007-0266-y (DOI)54747 (Lokalt ID)54747 (Arkivnummer)54747 (OAI)
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2017-12-13
    2. Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
    Öppna denna publikation i ny flik eller fönster >>Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell
    Visa övriga...
    2013 (Engelska)Ingår i: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12Artikel i tidskrift (Refereegranskat) 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.

    Nyckelord
    Screen printed electrodes, ECG, Electrode impedance, Electrode potential, Smartware electrodes
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-96422 (URN)10.1186/1475-925X-12-64 (DOI)000321916300001 ()
    Anmärkning

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

    Tillgänglig från: 2013-08-20 Skapad: 2013-08-19 Senast uppdaterad: 2017-12-06
    3. A Canonical correlation approach to heart beat detection in textile ECG measurements
    Öppna denna publikation i ny flik eller fönster >>A Canonical correlation approach to heart beat detection in textile ECG measurements
    Visa övriga...
    2006 (Engelska)Ingår i: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, s. 1-4Konferensbidrag, Publicerat paper (Refereegranskat)
    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.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2006
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-34459 (URN)21497 (Lokalt ID)08-6341-658-6 (e-book) (ISBN)978-08-6341-658-3 (ISBN)21497 (Arkivnummer)21497 (OAI)
    Konferens
    3rd International Conference on Advances in Medical Signal and Information Processing : MEDSIP 2006, July 17-19, 2006, Glasgow, Scotland
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2015-03-20Bibliografiskt granskad
    4. Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Öppna denna publikation i ny flik eller fönster >>Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Visa övriga...
    2013 (Engelska)Ingår i: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, nr 1, s. 61-71Artikel i tidskrift, Meeting abstract (Refereegranskat) 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.

    Ort, förlag, år, upplaga, sidor
    IGI Global, 2013
    Nyckelord
    textile electrodes, multichannel ecg, noise suppression, heartbeat detector
    Nationell ämneskategori
    Annan medicinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-79772 (URN)10.4018/jehmc.2013010106 (DOI)
    Konferens
    8th International Conference on Wearable Micro and Nano Technologies for Personalized Health
    Tillgänglig från: 2012-08-14 Skapad: 2012-08-14 Senast uppdaterad: 2015-03-20
  • 226.
    Rattfält, Linda
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Textile electrodes for ECG measurements in distributed care, performance and applications2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

    Delarbeten
    1. Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Öppna denna publikation i ny flik eller fönster >>Electrical characteristics of conductive yarns and textile electrodes for medical applications
    Visa övriga...
    2007 (Engelska)Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, nr 12, s. 1251-1257Artikel i tidskrift (Refereegranskat) 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.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-40953 (URN)10.1007/s11517-007-0266-y (DOI)54747 (Lokalt ID)54747 (Arkivnummer)54747 (OAI)
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2017-12-13
    2. A Canonical correlation approach to heart beat detection in textile ECG measurements
    Öppna denna publikation i ny flik eller fönster >>A Canonical correlation approach to heart beat detection in textile ECG measurements
    Visa övriga...
    2006 (Engelska)Ingår i: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, s. 1-4Konferensbidrag, Publicerat paper (Refereegranskat)
    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.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2006
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-34459 (URN)21497 (Lokalt ID)08-6341-658-6 (e-book) (ISBN)978-08-6341-658-3 (ISBN)21497 (Arkivnummer)21497 (OAI)
    Konferens
    3rd International Conference on Advances in Medical Signal and Information Processing : MEDSIP 2006, July 17-19, 2006, Glasgow, Scotland
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2015-03-20Bibliografiskt granskad
    3. Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Öppna denna publikation i ny flik eller fönster >>Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes
    Visa övriga...
    2013 (Engelska)Ingår i: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, nr 1, s. 61-71Artikel i tidskrift, Meeting abstract (Refereegranskat) 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.

    Ort, förlag, år, upplaga, sidor
    IGI Global, 2013
    Nyckelord
    textile electrodes, multichannel ecg, noise suppression, heartbeat detector
    Nationell ämneskategori
    Annan medicinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-79772 (URN)10.4018/jehmc.2013010106 (DOI)
    Konferens
    8th International Conference on Wearable Micro and Nano Technologies for Personalized Health
    Tillgänglig från: 2012-08-14 Skapad: 2012-08-14 Senast uppdaterad: 2015-03-20
  • 227.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Ahlström, Christer
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Wiklund, Urban
    Dept. of Biomedical Engineering & Informatics, Umeå University Hospital, Umeå, Sweden.
    A Canonical correlation approach to heart beat detection in textile ECG measurements2006Ingår i: IET 3rd International Conference On Advances in Medical, Signal and Information Processing, 2006. MEDSIP 2006, IEEE , 2006, s. 1-4Konferensbidrag (Refereegranskat)
    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.

  • 228.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Ahlström, Christer
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Eneling, Martin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ragnemalm, Bengt
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    Lindén, M.
    Intelligent Sensor Systems, Mälardalen University, Västerås, Sweden.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Biomedical Engineering, Örebro County Council, Örebro, Sweden.
    A platform for physiological signals including an intelligent stethoscope2009Ingår i: 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, s. 1038-1041Kapitel i bok, del av antologi (Refereegranskat)
    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.

  • 229.
    Rattfält, Linda
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Alod, Tanja
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Den textila elektrodens utformning - En studie i hur designparametrar inverkar på signalkvaliteten i EKG-mätningar2006Ingår i: Medicinteknikdagarna 06,2006, 2006Konferensbidrag (Övrigt vetenskapligt)
  • 230.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Alod, Tanja
    Linköpings universitet, Institutionen för medicinsk teknik.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    The Textile Electrode Configuration - How signal quality in ECG-measurements is affected by design parameters. (Poster)2006Konferensbidrag (Övrigt vetenskapligt)
  • 231.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Electrical Characterization of Screen Printed Electrodes for ECG Measurements2011Ingår i: Mediterranean conference on medical and biological engineering and computing 2013 / [ed] Roa Romero, Laura M., Springer Berlin/Heidelberg, 2011, Vol. 34, nr 2011, s. 219-221Kapitel i bok, del av antologi (Refereegranskat)
    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.

  • 232.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Properties of screen printed electrocardiography smartware electrodes investigated in an electro-chemical cell2013Ingår i: Biomedical engineering online, ISSN 1475-925X, E-ISSN 1475-925X, Vol. 12Artikel i tidskrift (Refereegranskat)
    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.

  • 233.
    Rattfält, Linda
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Chedid, Michel
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Tillverkningsmetodens inverkan på elektriska egenskaper hos textila elektroder.2007Ingår i: Posterpresentation på Medecinteknikdagarna, Conventum,2007, 2007Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

      

  • 234.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Chedid, Michel
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Lindén, Maria
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Electrical Properties of Textile Electrodes2007Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007, IEEE , 2007, s. 5735-5738Konferensbidrag (Refereegranskat)
    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.

  • 235.
    Rattfält, Linda
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hagström, Caroline
    Medicinsk teknik Örebro universitet.
    Lindén, Maria
    Inst för Datavetenskap och elektronik Mälardalens Högskola.
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Implementations of a technical system in distributed care - attitudes and possibilies2005Ingår i: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, s. 50-Konferensbidrag (Refereegranskat)
  • 236.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    A platform for physiological signals including an intelligent stethoscope.2008Konferensbidrag (Övrigt vetenskapligt)
  • 237.
    Rattfält, Linda
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Lindén, Maria
    Mälardalens Högskola Västerås.
    Hagström, Caroline
    Medicinsk teknik Örebro Läns Landsting.
    Berglin, Lena
    Textilhögskolan,Borås .
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Kroppsnära multisensorer och smarta textiplagg för vård och övervakning i hemmet.2005Ingår i: Läkarsällskapets Riksstämma 2005,2005, 2005Konferensbidrag (Övrigt vetenskapligt)
  • 238.
    Rattfält, Linda
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Lindén, Maria
    Mälardalen University.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Borga, Magnus
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska högskolan.
    Robust Heart Beat Detector Based on Weighted Correlation and Multichannel Input: Implementation on the ECG recorded with textile electrodes2013Ingår i: International Journal of E-Health and Medical Communications, ISSN 1947-315X, Vol. 4, nr 1, s. 61-71Artikel i tidskrift (Refereegranskat)
    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.

  • 239.
    Rattfält, Linda
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Lindén, Maria
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Berglin, Lena
    Data- och informationsteknik Göteborgs universitet.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Electrical characteristics of conductive yarns and textile electrodes for medical applications2007Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, nr 12, s. 1251-1257Artikel i tidskrift (Refereegranskat)
    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.

  • 240.
    Ressner, Marcus
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    On Nonlinear Acoustics in Contrast Echocardiography2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

    Delarbeten
    1. Effects of ultrasound contrast agents on doppler tissue velocity estimation
    Öppna denna publikation i ny flik eller fönster >>Effects of ultrasound contrast agents on doppler tissue velocity estimation
    Visa övriga...
    2006 (Engelska)Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 19, nr 2, s. 154-164Artikel i tidskrift (Refereegranskat) 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.

    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-28716 (URN)10.1016/j.echo.2005.09.025 (DOI)13885 (Lokalt ID)13885 (Arkivnummer)13885 (OAI)
    Tillgänglig från: 2009-10-09 Skapad: 2009-10-09 Senast uppdaterad: 2017-12-13
    2. Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging
    Öppna denna publikation i ny flik eller fönster >>Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging
    Visa övriga...
    2009 (Engelska)Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, nr 3, s. 447-457Artikel i tidskrift (Refereegranskat) 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.

    Nyckelord
    Ultrasound, Tissue Doppler, Contrast, Microbubbles, Velocity estimation
    Nationell ämneskategori
    Medicin och hälsovetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-17277 (URN)10.1016/j.ultrasmedbio.2008.09.012 (DOI)
    Tillgänglig från: 2009-03-16 Skapad: 2009-03-16 Senast uppdaterad: 2017-12-13
    3. Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment
    Öppna denna publikation i ny flik eller fönster >>Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment
    Visa övriga...
    2004 (Engelska)Ingår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, nr 01-Sep, s. 301-307Artikel i tidskrift (Refereegranskat) 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.

    Nyckelord
    ultrasound, simulation, nonlinear, contrast agents
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-46245 (URN)10.1016/j.ultras.2004.01.023 (DOI)
    Tillgänglig från: 2009-10-11 Skapad: 2009-10-11 Senast uppdaterad: 2017-12-13
    4. Ultrasound contrast response to variation of incident pulse length and polarity
    Öppna denna publikation i ny flik eller fönster >>Ultrasound contrast response to variation of incident pulse length and polarity
    Visa övriga...
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    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.

    Nyckelord
    Ultrasound contrast agents, nonlinear imaging, harmonic imaging, contrast echocardiography
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-65417 (URN)
    Tillgänglig från: 2011-02-07 Skapad: 2011-02-07 Senast uppdaterad: 2011-02-07
  • 241.
    Ressner, Marcus
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Effects of ultrasound contrast agents on doppler tissue velocity estimation2006Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 19, nr 2, s. 154-164Artikel i tidskrift (Refereegranskat)
    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.

  • 242.
    Ressner, Marcus
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Brodin, Lars-Åke
    Jansson, Tomas
    Dept of Electrical Measurements Lund University.
    Hoff, Lars
    Faculty of Science and Engineering Vestfold University, Horten, Norge.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Effekter av ultraljudskontrast vid hastighetsestimering med vävnadsdoppler2005Ingår i: Svenska Läkaresällskapets Riksstämma 2005,2005, 2005Konferensbidrag (Övrigt vetenskapligt)
  • 243.
    Ressner, Marcus
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Brodin, L-Å.
    Jansson, Tomas
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    How Ultrasound Contrast Agents effects Doppler Tissue Velocity Estimation2006Konferensbidrag (Övrigt vetenskapligt)
  • 244.
    Ressner, Marcus
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    Gustafsson, Disa
    Karolinska Institutet, Stockholm.
    Gustafsson, Agnetha
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk radiofysik. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
    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 system2011Konferensbidrag (Övrigt vetenskapligt)
  • 245.
    Ressner, Marcus
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Jansson, Tomas
    Lund University.
    Cedefamn, Jonny
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Contrast Biases the Autocorrelation Phase Shift Estimation in Doppler Tissue Imaging2009Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, nr 3, s. 447-457Artikel i tidskrift (Refereegranskat)
    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.

  • 246.
    Ressner, Marcus
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Kvikliene, Adriana
    Kaunas University of Technology.
    Hoff, Lars
    Westfold University College.
    Jurkonis, Rytis
    Kaunas University of Technology.
    Jansson, Tomas
    Lunds universitet.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Lukosevicius, Arunas
    Kaunas University of Technology.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Backscattered ultrasound from contrast microbubbles: effects of tissue and bubble interaction2004Ingår i: EMBS,2004, San Francisco: IEEE , 2004, s. 849-Konferensbidrag (Refereegranskat)
  • 247.
    Ressner, Marcus
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    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
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Lukosevicius, Arunas
    Inst of Biomedical Engineering Kaunas University of Technology, Lithuania.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ultrasound contrast for perfusion studies2005Ingår i: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, s. 107-Konferensbidrag (Refereegranskat)
  • 248.
    Ressner, Marcus
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    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
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Lukosevicius, Arunas
    Kaunas University of Technology .
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ultrasound contrast microbubbles: simulations and in vitro experiments2005Ingår i: EMBEC05,2005, Prag: IFMBE , 2005Konferensbidrag (Refereegranskat)
  • 249.
    Ressner, Marcus
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    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
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Janerot‐Sjoberg, Birgitta
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Ultrasound contrast response to variation of incident pulse length and polarityManuskript (preprint) (Övrigt vetenskapligt)
    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.

  • 250.
    Roback, Kerstin
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Nelson, Nina
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Pediatrik. Linköpings universitet, Hälsouniversitetet.
    Johansson, Anders
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hass, Ursula
    Linköpings universitet, Institutionen för medicin och hälsa, Medicinsk teknologiutvärdering. Linköpings universitet, Tekniska högskolan.
    Strömberg, Tomas
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan.
    A New Fiberoptical Respiratory Rate Monitor for the Neonatal Intensive Care Unit2005Ingår i: Pediatric Pulmonology, ISSN 8755-6863, Vol. 39, nr 2, s. 120-126Artikel i tidskrift (Refereegranskat)
    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.

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