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  • 151.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    KARLSSON, M
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    ERLANDSON, BE
    HYPERTHERMIA OF THE PROSTATE FROM A HEAT TRANSFER POINT OF VIEW1994Ingår i: PROCEEDINGS OF THE 16TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY - ENGINEERING ADVANCES: NEW OPPORTUNITIES FOR BIOMEDICAL ENGINEERS, PTS 1&2, 1994, Vol. 2, s. 768-769Konferensbidrag (Refereegranskat)
    Abstract [en]

    The finite element method is used to analyse the heat transfer at hyperthermia treatment of the prostate. The microwave antenna is enclosed in a water cooled intra urethral catheter. The purpose of this study is modeling and simulation of the temperature field during local microwave hyperthermal treatment of the prostate. Numerical calculations of the temperature field and the heat flux are necessary in order to get better knowledge of possibilities and restrictions of the method. The influence on the treatment from an incorrect location of the antenna has been studied. The location of the antenna is essential for a successful treatment. The effect of possible phase change processes associated with the heating is included in the analysis. A phase transition has a significant influence on the shape and the propagation speed of the temperature field. For the combination of microwave heating of the tissue and heat transfer from it there exists a transition zone of finite size instead of a transition front

  • 152.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    KARLSSON, Matts
    ANDERSSON, Gunnar
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hyperthermia treatment of the prostate - A complex heat transfer problem1993Ingår i: NUMERICAL METHODS IN THERMAL PROBLEMS, VOL VIII, PTS 1 AND 2, 1993, s. 1239-1250Konferensbidrag (Refereegranskat)
  • 153.
    Loyd, Dan
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Karlsson, Matts
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Erlandsson, B-E
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Computer analysis of hyperthermia treatment of the prostate1997Ingår i: Advances in Engineering Software, ISSN 0965-9978, E-ISSN 1873-5339, Vol. 28, s. 347-351Artikel i tidskrift (Refereegranskat)
  • 154.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    KARLSSON, Matts
    ERLANDSSON, Björn Erik
    SJODIN, Jan Gunnar
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Heat transfer analysis of hyperthermia treatment of the prostate1995Ingår i: COMPUTER SIMULATIONS IN BIOMEDICINE, 1995, s. 617-624Konferensbidrag (Refereegranskat)
  • 155.
    Lönn, Urban
    et al.
    Thoraxklin Universitetssjukhuset, Linköping.
    Wulff, J
    Keck, K-Y
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Peterzén, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Anestesiologi. Östergötlands Läns Landsting, Anestesi- och operationscentrum, Intensivvårdskliniken US.
    Ahn, Henrik Casimir
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Thoraxkirurgi. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Flow characteristics of the hemopump: An experimental in Vitro study1997Ingår i: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 63, nr 1, s. 162-166Artikel i tidskrift (Refereegranskat)
  • 156.
    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)
  • 157.
    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)
  • 158. 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)
  • 159.
    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.

  • 160.
    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.

  • 161.
    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.

  • 162.
    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.

  • 163.
    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]

      

  • 164.
    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.

  • 165.
    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)
  • 166.
    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.

  • 167.
    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.

  • 168.
    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.

  • 169.
    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)
  • 170.
    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)
  • 171.
    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.

  • 172.
    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)
  • 173.
    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)
  • 174.
    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)
  • 175.
    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.

  • 176. Rundquist, I
    et al.
    Smith, Q R
    Michel, M E
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Rapoport, S I
    Sciatic nerve blood flow measured by laser Doppler flowmetry and [14C]iodoantipyrine.1985Ingår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 248, nr 3 Pt 2, s. H311-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blood flow was examined in sciatic nerves of pentobarbital-anesthetized rats by means of laser Doppler flowmetry (LDF) and intravenous [14C]iodoantipyrine infusion. Continuous LDF signals demonstrated slow oscillations and acute, pressure-related changes in flow. The steady-state LDF signal was related linearly to nerve blood flow, as measured with [14C]iodoantipyrine, in intact nerves and nerves stripped of the epineurium. In 14 intact nerves, nerve blood flow averaged 0.27 +/- 0.03 (SE) ml X min-1 X g-1, whereas it averaged 0.13 +/- 0.01 in 5 stripped nerves. Autoradiographs of [3H]-nicotine-infused nerves and intra-arterial injection of 57Co-labeled microspheres demonstrated that flow was not uniform throughout the nerve cross section. The results indicate that LDF can be used to examine nerve blood flow in vivo, demonstrate a linear relation between the LDF signal and flow, and establish absolute values for blood flow in intact and stripped nerves of the anesthetized rat.

  • 177.
    Sjöberg, Birgitta Janero
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Subaortic flow profiles in aortic valve disease: a two-dimensional color Doppler study.1994Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 7, nr 3 Pt 1, s. 276-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With time-corrected color Doppler echocardiography, the aortic subvalvular spatial flow velocity profile was registered in two perpendicular planes in 10 patients with aortic valve disease and in 5 healthy control subjects. Patients with predominant aortic valve stenosis had a fairly flat profile, and the subvalvular diameter, obtained from left parasternal two-dimensional tissue imaging, provided a good estimate of the mean of the two transverse flow axes. This explains the accuracy in determination of stroke volume and aortic valve area that is reported in studies on patients with aortic valve stenosis when the continuity equation is used. However, the use of apical pulsed Doppler ultrasound registrations from the left ventricular outflow tract and parasternal two-dimensional echocardiography for flow area calculation may introduce large errors in calculated stroke volume in certain patients with aortic regurgitation and in normal subjects, because of a non-flat spatial velocity profile or an inaccurate estimate of flow area.

  • 178.
    Sjöberg, Birgitta Janero
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Eidenvall, L
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Vascular characteristics influence the aortic ultrasound Doppler signal: computer and hydraulic model simulations.1993Ingår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 147, nr 3, s. 271-279Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is an increasing demand for non-invasive methods for the assessment of left ventricular function. Ultrasound Doppler methods are promising, and the early systolic flow velocity signal immediately distal to the aortic valve has been used clinically for this purpose. However, the signal is influenced not only by left ventricular ejection but also by systemic vascular characteristics. Their relative contribution to the time-velocity signal has not been analysed in depth previously. A theoretical analysis, based on a three-element Windkessel model, neglecting peripheral outflow in early systole and assuming linear pressure rise, was therefore tested in computer and hydraulic model simulations where peripheral outflow was included. Significant changes in early aortic flow velocity parameters were found when vascular characteristics were altered. As predicted by the theory, with a standardized aortic valve area and aortic pressure change, the simulations confirmed that maximal flow velocity is related to compliance of the aorta and the large arteries, and that maximal acceleration is inversely related to the characteristic impedance of the aorta. Therefore, maximal velocity and acceleration can be used for assessment of left ventricular function only in situations where vascular characteristics can be considered relatively constant or where they can be estimated.

  • 179. Språngberg, Anders
    et al.
    TERIO, Heikki
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    ENGBERG, Anders
    Griffiths, Derek
    PRESSURE-FLOW STUDIES PREOPERATIVELY AND POSTOPERATIVELY IN PATIENTS WITH BENIGN PROSTATIC HYPERTROPHY - ESTIMATION OF THE URETHRAL PRESSURE-FLOW RELATION AND URETHRAL ELASTICITY1991Ingår i: Neurourology and Urodynamics, ISSN 0733-2467, E-ISSN 1520-6777, Vol. 10, nr 2, s. 139-167Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pressure/flow studies were performed in 28 men with benign prostatic hypertrophy. Twenty-three of the men were also studied postoperatively. Urethral function during micturition was quantified by the urethral pressure/flow relation, P(det) = P(mo) + L(m) Q(m), where P(det) is detrusor pressure, P(mo) is minimal opening pressure, Q is flow rate, and m and L(m) are parameters. Using this method to quantify urethral function, three urodynamically different types of obstruction can be defined. In the first of these, P(mo) is elevated corresponding to Schafer’s compressive obstruction. The second is a constrictive type of obstruction in which m greater-than-or-equal-to 4/3 and L(m) is elevated and the third is a low-compliant type of obstruction in which m less-than-or-equal-to 1 and L(m) is elevated. The two latter types of obstruction may be combined with a compressive obstruction. The preoperative pressure/flow relations were mostly characterized by a very high P(mo), a moderately elevated L(m), and a low m. Thus the majority of patients had a combination of compressive and low-compliant obstruction. Postoperatively, micturitions were much improved and the pressure/flow relations often had an even lower P(mo) than normal, a normal L(m), and a high m. From the pressure/flow relations, the elasticity of the flow-controlling zone can be estimated and described by the urethral pressure/area relation, p(A) = P(mo) + K(n) A(n), where p(A) is the intrinsic urethral pressure, A is the cross-sectional area of the flow-controlling zone and K(n) and n are parameters describing the distensibility of the flow-controlling zone. Preoperatively, the flow-controlling zone had a low distensibility. The shape of the curve suggested that the urethra could have been distended further by higher pressure. Postoperatively, the urethra was distended to larger cross-sectional areas, but in many cases the shape of the curve suggested that distension was restricted by fibrosis. Median and range values for the model parameters as well as discriminating limits between the preoperative micturitions and micturitions in elderly men without voiding problems are presented. The exponent m is not perfectly reproducible but tends to be the same if a person performs several micturitions. The residual sum of squares is often increased more than 100% if an exponent m value other than the optimal one is used for curve fitting. Results when the micturitions were analysed with Schafer’s model and classified using the maximum flow/pressure at maximum flow diagram recommended by the International Continence Society are also shown.

  • 180. Spånberg, Anders
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    ENGBERG, Anders
    TERIO, Hikki
    URODYNAMIC ASSESSMENT OF OBSTRUCTION - SHOULD IT BE EVALUATED ACCORDING TO GRIFFITHS OR SCHAFER MODEL1987Ingår i: Scandinavian Journal of Urology and Nephrology, ISSN 0036-5599, E-ISSN 1651-2065, nr 105Artikel i tidskrift (Refereegranskat)
  • 181. Spånberg, Anders
    et al.
    Terio, Hikki
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    PRESSURE-FLOW STUDIES IN ELDERLY MEN WITHOUT VOIDING PROBLEMS - ESTIMATION OF THE URETHRAL PRESSURE-FLOW RELATION AND URETHRAL ELASTICITY1990Ingår i: Neurourology and Urodynamics, ISSN 0733-2467, E-ISSN 1520-6777, Vol. 9, nr 2, s. 123-138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow in the urethra is controlled by an elastic constriction, the flow-controlling zone. The distensibility of this zone is described by the pressure/area relation, which gives the static pressure as a function of the cross-sectional area at the flow-controlling zone. The pressure/area relation can be calculated from the pressure/flow relation, which is estimated from the pressure/flow plot obtained at a urodynamic examination. In this study the urethral pressure/flow and pressure/area relations were estimated for 21 randomly selected men (62–75 years old) without voiding problems.

    Nineteen of 21 persons in this group had pressure/flow relations with a low slope. This corresponds to a low slope in the pressure/area relation indicating high distensibility of the flow-controlling zone, which for 18 persons was estimated to be distended to areas larger than 10 mm2 during micturition. Twenty persons had a minimal urethral opening pressure below 55 cm H2O. The estimated pressure/area relation was linear in 59% of the micturitions, indicating that the flow-controlling zone could have been distended to a larger cross-sectional area, if the bladder had achieved a higher pressure. The 10th–90th percentiles for maximum flow and detrusor pressure at maximum flow were 7.2–24.3 ml/s and 24–76 cm H2O, respectively. Four persons had low flow and low pressure, indicating diminished detrusor contractility with age. Twenty-four percent of the persons had unstable bladder contractions with a pressure rise < 15cm H2O and 19% with a pressure rise < 15cm H2O.

  • 182. Spånberg, Anders
    et al.
    Terio, Hikki
    Enberg, Anders
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    QUANTIFICATION OF URETHRAL FUNCTION BASED ON GRIFFITHS MODEL OF FLOW THROUGH ELASTIC TUBES1989Ingår i: Neurourology and Urodynamics, ISSN 0733-2467, E-ISSN 1520-6777, Vol. 8, nr 1, s. 29-52Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Griffiths' model of flow-through elastic tubes makes it possible to relate the elastic properties of the flow-controlling zone to the pressure/flow relation of the urethra. In this work the pressure function p(A) = Pmo + Kn An, where A is cross-sectional area, Pmo the minimal opening pressure, and Kn and n parameters describing urethral distensibility, describes the elastic properties of the flow-controlling zone. By curve-fitting in the pressure/flow plot, the three parameters pmo, Kn, and n can be estimated analytically. Using this model it is possible to identify three different biomechanical changes that may cause obstruction. First, pmo may be elevated. Second, the urethra can be distended to a certain area only, corresponding to high values of Kn and n. Third, the urethra can be distended but a higher-than-normal pressure increase above Pmo is needed, Kn is high, and n is low. With this model it is possible to quantify urethral function for both scientific and clinical purposes.

  • 183.
    Spångberg, Anders
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för biomedicin och kirurgi, Avdelningen för kirurgi. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Urologiska kliniken i Östergötland.
    Folkestad, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för biomedicin och kirurgi, Avdelningen för kirurgi. Östergötlands Läns Landsting, Kirurgi- och onkologicentrum, Urologiska kliniken i Östergötland.
    Kristjansson, B
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    New method to quantify the urodynamic improvement when treating bladder utlet obstruction - The efficacy of transurethral resectionin benign prostatic hypertrophy1995Ingår i: Neurology, ISSN 0028-3878, E-ISSN 1526-632X, Vol. 14, nr 4, s. 325-335Artikel i tidskrift (Refereegranskat)
  • 184. Storck, K
    et al.
    Karlsson, Matts
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Heat transfer simulation in the evaluation of the nasal thermistor technique1996Ingår i: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 43, s. 1187-1191Artikel i tidskrift (Refereegranskat)
  • 185. Sun, Y
    et al.
    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.
    Eidenvall, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Estimation of pulsatile flow by surface integration of velocity vectors in Doppler ultrasound images from two arthogonal planes1995Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 8, s. 904-914Artikel i tidskrift (Refereegranskat)
  • 186. Sun, Y
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Sjöberg, Birgitta Janero
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Eidenvall, L
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images.1995Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 8, nr 6, s. 904-914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (+/- 10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

  • 187. Sun, Y
    et al.
    Janerot-Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Mathematical model that characterizes transmitral and pulmonary venous flow velocity patterns1995Ingår i: American journal of physiology, ISSN 0002-9513, Vol. 268, s. 476-489Artikel i tidskrift (Refereegranskat)
  • 188. Sun, Y
    et al.
    Sjöberg, Birgitta Janero
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Mathematical model that characterizes transmitral and pulmonary venous flow velocity patterns.1995Ingår i: American Journal of Physiology, ISSN 0002-9513, E-ISSN 2163-5773, Vol. 268, nr 1 Pt 2, s. H476-89Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The transmitral and pulmonary venous flow velocity (TMFV and PVFV, respectively) patterns are related to the physiological state of the left heart by use of an electrical analog model. Filling of left ventricle (LV) through the mitral valve is characterized by a quadratic Bernoulli's resistance in series with an inertance. Filling of the left atrium (LA) through the pulmonary veins is represented by a lumped network of linear resistance, capacitance, and inertance. LV and LA are each represented by a time-varying elastance. A volume dependency is incorporated into the LV model to produce physiological pressure-volume loops and Starling curves. The state-space representation of the analog model consists of 10 simultaneous differential equations, which are solved by numerical integration. Model validity is supported by the following. First, the expected effects of aging and decreasing LV compliance on TMFV and PVFV are accurately represented by the model. Second, the model-generated TMFV and PVFV waveforms fit well to pulsed-Doppler recordings in normal and postinfarct patients. It is shown that the TMFV deceleration time is prolonged by the increase in LV compliance and, to a lesser extent, by the increase in LA compliance. A shift from diastolic dominance to systolic dominance in PVFV occurs when LA compliance or pulmonary perfusion pressure increases or when LV compliance or mitral valve area decreases. The present model should serve as a useful theoretical basis for echocardiographic evaluation of LV and LA functions.

  • 189. Sun, Ying
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Sjöberg, Birgitta Janero
    Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Eindvall, Lars
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images1997Ingår i: Journal of the American College of Cardiology, ISSN 0735-1097, E-ISSN 1558-3597, Vol. 8, nr 6, s. 904-914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (±10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

  • 190. Teriö, H
    et al.
    Spångberg, A
    Engberg, A
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Estimation of elastic properties in the urethral flow controlling zone by signal analysis of urodynamic pressure/flow data.1989Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 27, nr 3, s. 314-321Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When urethral flow is treated as a lossless flow through an elastic tube, the relationship between the detrusor pressure and the urinary flow can be related to the elasticity of the flow-controlling zone of the urethra. A recent analytical method of describing urethral elasticity is implemented on a computer. The function p(Q) = pmo + LmQm is fitted to the recorded pressure/flow data. p(Q) is the detrusor pressure, Q the flow and pmo, m and Lm parameters. The elastic properties are then obtained as p(A) = pmo + KnAn, where p(A) is the static pressure, A the cross-sectional area of the flow-controlling zone and n and Kn calculated parameters. The urodynamic methods used and the computer implementation of the analytical method are described. In obstructed and unobstructed men without neurological symptoms, the elastic properties could be estimated in 94 per cent of the micturitions. The method makes it possible to describe urethral flow properties with Griffiths' model in a standardised way and compare results obtained by different investigators. It is recommended for quantification of urethral obstruction in research and for assessment of borderline cases of obstruction in clinical practice.

  • 191.
    Thurin, Anders
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik.
    Goushegir, G
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Thulesius, O
    Venous flow in an in vitro model: effect of extravascular pressure1997Ingår i: Journal of Vascular Surgery, ISSN 0741-5214, E-ISSN 1097-6809, Vol. 3, s. 130-136Artikel i tidskrift (Refereegranskat)
  • 192. Tibbling, Lita
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Pope, C E
    Electromyography of human oesophageal smooth muscle.1986Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 21, nr 5, s. 559-567Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim was to study whether electromyography (EMG) activity is synchronous with oesophageal motor activity as assessed by manometry from the same oesophageal site. Patients with different motor disorders of the oesophagus and control subjects were investigated. EMG recordings were made by means of a suction capsule with silver/silver chloride spike electrodes. Slow EMG waves synchronous with respiration were recorded from the lower oesophageal sphincter and intermittently from the body of the oesophagus. Edrophonium increased spike discharges; atropine diminished or abolished spike discharges after swallowing. Swallowing caused a burst of spiking activity which began immediately after deglutition. Continuous sips of water produced constant EMG activity but no peristaltic contractions as seen by manometry. In a patient with scleroderma and aperistalsis, swallowing elicited vigorous electrical activity. The different EMG findings without simultaneous contractions at manometry are interpreted as a response to a swallow by the longitudinal muscle of the oesophagus.

  • 193. Tibbling, Lita
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    POPE, CE
    ELECTROMYOGRAPHY OF THE HUMAN ESOPHAGUS1982Ingår i: Gastroenterology, ISSN 0016-5085, E-ISSN 1528-0012, Vol. 82, nr 5Artikel i tidskrift (Refereegranskat)
  • 194.
    Tibbling, Lita
    et al.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Oto-Rhino-Laryngologi. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Sökjer, H.
    Oesophagus fysiology mot bakgrund av nya medicintekniska landvinningar1977Ingår i: Svensk Oe NH Tidskrift, ISSN 1400-0121, Vol. 1, nr 2, s. 1-1Artikel i tidskrift (Övrigt vetenskapligt)
  • 195. Tibbling, Lita
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Öberg, Åke
    Linköpings universitet, Institutionen för medicinsk teknik.
    ACCURACY AND VALIDITY OF ESOPHAGEAL MANOMETRY SYSTEMS1980Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 25, nr 5Artikel i tidskrift (Refereegranskat)
  • 196.
    Walker, Andrew
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Henriksen, Egil
    Centre for Clinical Research, Central Hospital, Västerås, Sweden.
    Ringqvist, Ivar
    Department of Clinical Physiology, Central Hospital, Västerås, Sweden.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    A Rotating Cylinder Phantom for Flow and Tissue Color Doppler Testing2009Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, nr 11, s. 1892-1898Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultrasound Doppler using two-dimensional (2D) techniques is commonly used to study blood flow and myocardial tissue motion. This use includes measurement of velocity and time intervals, often in relation to the electrocardiogram (ECG) signal. 2D Doppler is frequently considered a real-time technique but in reality the acquisition time can be as long as 200 ms per image. We have developed a test-phantom using a rotating cylinder to simulate blood flow and tissue motion in a whole sector or space angle to evaluate velocity and timing characteristics.The phantom can produce constant velocities for velocity testing, as well as accelerating movement for testing the timing characteristics of ultrasound systems. Our investigation shows that the cylinder phantom is especially suitable for timing measurements in 2D Doppler imaging and that time delays between the Dopplersignals and the ECG signal exist in the tested ultrasound system.

  • 197.
    Walker, Andrew
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Olsson, Eva
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ringqvist, Ivar
    Centrallasarettet i Västerås.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Accuracy of spectral Doppler flow and tissue velocity measurements in ultrasound systems2004Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 30, nr 1, s. 127-132Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Blood and tissue velocity are measured and analysed in cardiac, vascular and other applications of diagnostic ultrasound (US). An error in system calibration is a potential risk for misinterpretation of the measurements. To determine the accuracy in velocity calibration, we tested three common commercial US systems using a Doppler string phantom. We tested pulsed and continuous-wave Doppler modes for velocities relevant to both cardiac blood flow and tissue-velocity estimation. The US systems were tested with settings and transducers commonly used in cardiac applications. One system consistently overestimated velocity by about 5%, whereas the other two systems were quite accurate in velocity estimation. These findings emphasize the importance of continuous quality control of US equipment.

  • 198.
    Walker, Andrew
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Olsson, Eva
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Ringqvist, Ivar
    Västerås.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik.
    Time delays in ultrasound systems can result in fallacious measurements.2002Ingår i: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 28, s. 259-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Even short time delays (less than 30 ms) in cardiac motion pattern may have clinical relevance. These delays can be measured with echocardiography, using techniques such as flow and tissue Doppler and M-mode together with external signals (e.g., ECG and phonocardiography). If one or more of these signals are delayed in relation to the other signals (asynchronous), an incorrect definition of cardiac time intervals can occur, the consequence of which is invalid measurement. To determine if this time delay in signal processing is a problem, we tested three common ultrasound (US) systems using the ECG as the reference signal. We used a digital ECG simulator and a Doppler string phantom to obtain test signals for flow and tissue pulsed Doppler, M-mode, phonocardiography, auxiliary and ECG signals. We found long time delays of up to 90 ms in one system, whereas delays were mostly short in the two other systems. The time delays varied relative to system settings. Consequently, to avoid these errors, precise knowledge of the characteristics of the system being used is essential.

    Federation for Ultrasound in Medicine & Biology.

  • 199. Wandel, Björn
    et al.
    Pettersson, Nils-Erik
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Certification of Clinical Engineers in Sweden2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Swedish Society for Biomedical Engineering and Physics has certified clinical engineers since 1994. The certification is performed at two levels: Master of Science and Bachelor of Science. We have in total received had 695 applications and certified 391 engineers. We have also developed a system to certify Specialists in Clinical engineering.

  • 200.
    Wranne, Bengt
    et al.
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hök, B
    Inte så lätt att anvanda stetoskopet på rätt sätt. Auskultationens svåra konst bör ha stort utrymme i läkarutbildningen.1999Ingår i: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 96, nr 24, s. 2981-2984Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although the stethoscope is used daily by almost every physician, the full potential of the art of stethoscopy is seldom tapped. It has been replaced by newer and more costly techniques. In the article it is argued that more time in medical education should be allocated to stethoscopy, so that it can be used in selecting patients who will benefit most from examination with modern diagnostic tools. The medical technological background of stethoscopy is also reviewed, as are the reasons why it is difficult to give sound advice on the choice of stethoscope.

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