liu.seSök publikationer i DiVA
Ändra sökning
Avgränsa sökresultatet
12345 101 - 150 av 208
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101.
    Eidenvall, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    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.
    Determination of regurgitant flow in a pulsatile model by integrating velocities from the entire 3D proximal velocity field1992Ingår i: American Heart Association,1993, 1992Konferensbidrag (Refereegranskat)
  • 102.
    Eidenvall, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Barclay, S A
    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.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Regurgitant heart valve flow from 3D proximal velocity field - continued search for the ideal method1995Ingår i: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 33, s. 131-139Artikel i tidskrift (Refereegranskat)
  • 103.
    Eidenvall, Lars
    et al.
    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.
    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.
    2D Doppler Flowvelocity profiles can be time corrected with an external ECG delay device1992Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 5, s. 405-413Artikel i tidskrift (Refereegranskat)
  • 104. Eidenvall, Lars
    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.
    Two-dimensional color Doppler flow velocity profiles can be time corrected with an external ECG-delay device.1992Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 5, nr 4, s. 405-413Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although two-dimensional ultrasound color flow imaging is often considered to be a real-time technique, the acquisition time for two-dimensional color images may be up to 200 msec. Time correction is therefore necessary to obtain correct flow velocity profiles. We have developed a time-correction method in which a specially designed unit detects the QRS complex from the patient and creates a trig pulse that is delayed incrementally in relation to the QRS complex. This trig pulse controls the acquisition of the ultrasound images. A number of consecutively delayed images, with known incremental delay between the sweeps, can thus be stored in the memory of the echocardiograph and transferred digitally to a computer. The time-corrected flow velocity profile is obtained by interpolation of data from the time-delayed profiles. The system was evaluated in a Doppler string phantom test. With this technique it is possible to study time-corrected flow velocity profiles without the need to alter existing ultrasound Doppler equipment.

  • 105. Eidenvall, Lars
    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.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    INFORMATION IN THE AORTIC BLOOD VELOCITY SIGNAL - A SIMULATION STUDY1991Ingår i: PROCEEDINGS OF THE ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 13, PTS 1-5, 1991, s. 2248-2249Konferensbidrag (Refereegranskat)
  • 106.
    Engvall, Jan
    et al.
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. 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.
    Coarctation of the aorta--a theoretical and experimental analysis of the effects of a centrally located arterial stenosis.1991Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 29, nr 3, s. 291-296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aortic coarctation is a local constriction of the aorta that may severely affect haemodynamics. It is therefore important to quantify these effects. Using Bernoulli's equation and the momentum theorem, the pressure drop is described including the pressure recovery distal to the coarctation and the effects of collateral flow; both laminar and turbulent. Assuming the coarctation and collaterals to be stiff, a quadratic relationship between flow and pressure drop is expected for flow through the coarctation and for turbulent collateral flow. For laminar collateral flow, a linear relationship is expected. The coarctation flow was studied in a model consisting of a rigid tube with local constriction, connected to a flooded-level tank, containing a 36 per cent by weight solution of sucrose, with a viscosity equivalent to that of blood at body temperature. The pressure drop across the constriction showed a quadratic relationship to flow in agreement with theoretical expectations. Pressure recovery in this model was very slight (0-4 mm Hg). Nine patients with aortic coarctation were catheterised. Cardiac output and pressure drop across the coarctation were measured at rest and during supine cycle exercise at two different workloads. The relationship between mean pressure drop and cardiac output tended to be either 'parabolic' or, in some cases, approximately linear, suggesting that the flow situation in aortic coarctation can be quantified by expressions that either linearly or quadratically relate pressure and flow.

  • 107.
    Engvall, Jan
    et al.
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    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.
    Nylander, 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.
    Importance of collateral vessels in aortic coarctation: Computer simulation at rest and exercise using transmission line elements1994Ingår i: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 32, s. 115-122Artikel i tidskrift (Refereegranskat)
  • 108. Flachskampf, FA
    et al.
    Köhler, J
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Lepper, W
    Haltern, G
    Hanrath, P
    Overestimation of flow velocity through leaks in mechanical prosthese and other small orifices1997Ingår i: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 10, s. 904-914Artikel i tidskrift (Refereegranskat)
  • 109.
    Flachskampf, Frank A
    et al.
    Institute of Aerodynamics RWTH, Aachen, Germany.
    Köhler, Josef
    Institute of Aerodynamics RWTH, Aachen, Germany.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Lepper, Wolfgang
    Institute of Aerodynamics RWTH, Aachen, Germany.
    Hanrath, Peter
    Institute of Aerodynamics RWTH, Aachen, Germany.
    Overestimation of flow velocity through leaks in mechanical valve prostheses and through small orifices by continuous-wave Doppler.1997Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 10, nr 9, s. 904-914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reliability of continuous-wave Doppler flow velocity measurements through small regurgitant lesions, such as in prosthetic leakage, has not been systematically analyzed. To evaluate the accuracy of continuous-wave Doppler in prosthetic valve leakage and small orifices in an in vitro, steady-flow model-flow velocities through the leaks of twelve intact mechanical prostheses and through six circular nozzles (area 0.5 to 20 mm2) were measured at pressure drops between 30 and 105 mm Hg. These results were compared with those predicted by the modified Bernoulli equation. Laser Doppler anemometry of flow velocities through the nozzles was also performed. Despite high correlation, there was substantial overestimation of Bernoulli predicted velocities by echo Doppler in the prosthetic leaks (mean +12.3% +/- 9.4%; range 90.3% to 143.4%). In the nozzles < or = 10 mm2, but not in the largest (20 mm2) nozzle, there was also overestimation of the Bernoulli predicted velocities (mean +6.2% +/- 2%). Laser Doppler anemometry of flow velocities through the nozzles showed slightly lower values than predicted by the Bernoulli equation. Thus, continuous-wave echo Doppler overestimates flow velocities through small orifices. This apparently is, at least in part, due to transit time effects and should be taken into account when using echo Doppler in small (< 10 mm2) orifices, such as in mild to moderate regurgitant lesions and prosthetic valve leakage.

  • 110.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska fakulteten.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Babic, Ankica
    Linköpings universitet, Institutionen för medicinsk teknik, Medicinsk informatik. Linköpings universitet, Tekniska fakulteten. Department of Information Science and Media Studies, University of Bergen, Norway.
    A pattern recognition framework for detecting dynamic changes on cyclic time series2015Ingår i: Pattern Recognition, ISSN 0031-3203, E-ISSN 1873-5142, Vol. 48, nr 3, s. 696-708Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a framework for binary classification of the time series with cyclic characteristics. The framework presents an iterative algorithm for learning the cyclic characteristics by introducing the discriminative frequency bands (DFBs) using the discriminant analysis along with k-means clustering method. The DFBs are employed by a hybrid model for learning dynamic characteristics of the time series within the cycles, using statistical and structural machine learning techniques. The framework offers a systematic procedure for finding the optimal design parameters associated with the hybrid model. The proposed  model is optimized to detect the changes of the heart sound recordings (HSRs) related to aortic stenosis. Experimental results show that the proposed framework provides efficient tools for classification of the HSRs based on the heart murmurs. It is also evidenced that the hybrid model, proposed by the framework, substantially improves the classification performance when it comes to detection of the heart disease.

  • 111.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Lindèn, Maria
    Mälardalen University, Sweden.
    Babic, Ankica
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan. Univeristy of Bergen, Norway.
    A Novel Model for Screening Aortic Stenosis Using Phonocardiogram2015Ingår i: 16th Nordic-Baltic Conference on Biomedical Engineering / [ed] Henrik Mindedal and Mikael Persson, Springer Science Business Media , 2015, s. 48-51Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study presents an algorithm for screening aortic stenosis, based on heart sound signal processing. It benefits from an artificial intelligent-based (AI-based) model using a multi-layer perceptron neural network. The AI-based model learns disease related murmurs using non-stationary features of the murmurs. Performance of the model is statistically evaluated using two different databases, one of children and the other of elderly volunteers with normal heart condition and aortic stenosis. Results showed a 95% confidence interval of the high accuracy/sensitivity (84.1%-86.0%)/(86.0%-88.4%) thus exhibiting a superior performance to a cardiologist who relies on the conventional auscultation. The study suggests including the heart sound signal in the clinical decision making due to its potential to improve the screening accuracy.

  • 112.
    Gharehbaghi, Arash
    et al.
    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. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Janerot Sjöberg, Birgitta
    Division of Medical Imaging and Technology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden; Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden; School of Technology and Health, KTH Royal Institute of Technology, Stockholm, Sweden.
    Per, Ask
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    A novel method for discrimination between innocent and pathological heart murmurs2015Ingår i: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 37, nr 7, s. 674-682Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a novel method for discrimination between innocent and pathological murmurs using the growing time support vector machine (GTSVM). The proposed method is tailored for characterizing innocent murmurs (IM) by putting more emphasis on the early parts of the signal as IMs are often heard in early systolic phase. Individuals with mild to severe aortic stenosis (AS) and IM are the two groups subjected to analysis, taking the normal individuals with no murmur (NM) as the control group. The AS is selected due to the similarity of its murmur to IM, particularly in mild cases. To investigate the effect of the growing time windows, the performance of the GTSVM is compared to that of a conventional support vector machine (SVM), using repeated random sub-sampling method. The mean value of the classification rate/sensitivity is found to be 88%/86% for the GTSVM and 84%/83% for the SVM. The statistical evaluations show that the GTSVM significantly improves performance of the classification as compared to the SVM.

  • 113.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Dutoit, Thierry
    University of Mons, Belgium .
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Sornmo, Leif
    Lund University, Sweden .
    Detection of systolic ejection click using time growing neural network2014Ingår i: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 36, nr 4, s. 477-483Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a novel neural network for classification of short-duration heart sounds: the time growing neural network (TGNN). The input to the network is the spectral power in adjacent frequency bands as computed in time windows of growing length. Children with heart systolic ejection click (SEC) and normal children are the two groups subjected to analysis. The performance of the TGNN is compared to that of a time delay neural network (TDNN) and a multi-layer perceptron (MLP), using training and test datasets of similar sizes with a total of 614 normal and abnormal cardiac cycles. From the test dataset, the classification rate/sensitivity is found to be 97.0%/98.1% for the TGNN, 85.1%/76.4% for the TDNN, and 92.7%/85.7% for the MLP. The results show that the TGNN performs better than do TDNN and MLP when frequency band power is used as classifier input. The performance of TGNN is also found to exhibit better immunity to noise.

  • 114.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Dutoit, Thierry
    TCTS Lab,University of Mons, Belgium.
    Sepehri, Amir
    ICT research center, Amir Kabir University, Tehran, Iran.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    An Automatic Tool for Pediatric Heart Sounds SegmentationManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, we present a novel algorithm for pediatric heart sound segmentation, incorporated into a graphical user interface. The algorithm employs both the Electrocardiogram (ECG) and Phonocardiogram (PCG) signals for an efficient segmentation under pathological circumstances.First, the ECG signal is invoked in order to determine the beginning and end points of each cardiac cycle by using wavelet transform technique. Then, first and second heart sounds within the cycles are identified over the PCG signal by paying attention to the spectral properties of the sounds. The algorithm is applied on 120 recordings of normal and pathological children, totally containing 1976 cardiac cycles. The accuracy of the segmentation algorithm is 97% for S1 and 94% for S2 identification while all the cardiac cycles are correctly determined.

  • 115.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ekman, Inger
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Nylander, Eva
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Janerot Sjöberg, Birgitta
    Departments of Clinical Science, Intervention and Technology, Karolinska Institutet & Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden.
    Severity assessments of aortic stenosis using intelligent phonocardiographyManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Objectives: To study capabilities of the intelligent phonocardiography (IPCG) in automatic grading severity of the aortic stenosis (AS).

    Methods: Phonocardiogram signals were recorded from the patients with AS, as diagnosed by echocardiography. The patient group is comprised of signals, recorded from 5 patients (2 recordings from each), mostly elderly referrals (>60 years) with mild to severe AS. An advanced processing algorithm, consisted of the wavelet transform and the stepwise regression analysis, characterizes the systolic murmur caused by the AS in order to predict the 5 indicators; mean pressure gradient over the aortic valve (MPG), maximum jet velocity (MJV), aortic valve area (AVA), velocity time integral and the ejection period. The automatic assessment is performed by an artificial neural network using the predicted values of the indicators as the input data. Reliability of the IPCG is validated by applying repeated random sub-sampling (RRSS) with 70%/30% of the training/testing data, and calculating the accuracy. The RRSS is also employed to validate reproducibility of the IPCG by using 70% of the signals for training and the second recording of the same individuals for  testing.

    Results: Accuracy of the IPCG is estimated to be and (95% confidence interval) for the reliability and the reproducibility, respectively. Linear correlation between the characterized systolic murmur and the MPG (r>0.81), the MJV (r>0.82) and the AVA (r>0.85) is observed.

    Conclusions: The IPCG has the potential to objectively serve as a clinical tool for grading severity of the aortic stenosis.

  • 116.
    Gharehbaghi, Arash
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Ekman, Inger
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska fakulteten.
    Nylander, Eva
    Region Östergötland, Hjärt- och Medicincentrum, Fysiologiska kliniken US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten.
    Janerot-Sjoberg, Birgitta
    Karolinska Institute, Sweden; Karolinska University Hospital, Sweden; Karolinska University Hospital, Sweden; KTH Royal Institute Technology, Sweden.
    Letter: Assessment of aortic valve stenosis severity using intelligent phonocardiography2015Ingår i: International Journal of Cardiology, ISSN 0167-5273, E-ISSN 1874-1754, Vol. 198, s. 58-60Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 117.
    Hass, Ursula
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för hälsa och samhälle, Centrum för utvärdering av medicinsk teknologi.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Wårdell, Karin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Competence Centre NIMED and it's graduate education - collaboration between university and industry.1999Ingår i: Ann Int Conf of the IEEE Engineering in Medicine and Biology Society,1999, 1999Konferensbidrag (Övrigt vetenskapligt)
  • 118.
    Hoglund, K.
    et al.
    Höglund, K., Department of Anatomy and Physiology, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
    Ahlström, Christer
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Haggstrom, J.
    Häggström, J., Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hult, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Kvart, C.
    Department of Anatomy and Physiology, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden.
    Time-frequency and complexity analyses for differentiation of physiologic murmurs from heart murmurs caused by aortic stenosis in boxers2007Ingår i: American Journal of Veterinary Research, ISSN 0002-9645, E-ISSN 1943-5681, Vol. 68, nr 9, s. 962-969Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective - To investigate whether time-frequency and complexity analyses of heart murmurs can be used to differentiate physiologic murmurs from murmurs caused by aortic stenosis (AS) in Boxers. Animals - 27 Boxers with murmurs. Procedures - Dogs were evaluated via auscultation and echocardiography. Analyses of time-frequency properties (TFPs, ie, maximal murmur frequency and duration of murmur frequency > 200 Hz) and correlation dimension (T2) of murmurs were performed on phonocardiographic sound data. Time-frequency property and T2 analyses of low-intensity murmurs in 16 dogs without AS were performed at 7 weeks and 12 months of age. Additionally, TFP and T2 analyses were performed on data obtained from 11 adult AS-affected dogs with murmurs. Results - In dogs with low-intensity murmurs, TFP or T2 values at 7 weeks and 12 months did not differ significantly. For differentiation of physiologic murmurs from murmurs caused by mild AS, duration of murmur frequency > 200 Hz was useful and the combination assessment of duration of frequency > 200 Hz and T2 of the murmur had a sensitivity of 94% and a specificity of 82%. Maximal murmur frequency did not differentiate dogs with AS from those without AS. Conclusions and Clinical Relevance - Results suggested that assessment of the duration of murmur frequency > 200 Hz can be used to distinguish physiologic heart murmurs from murmurs caused by mild AS in Boxers. Combination of this analysis with T2 analysis may be a useful complementary method for diagnostic assessment of cardiovascular function in dogs.

  • 119.
    Hult, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ahlström, Christer
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Rattfält, Linda
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hagström, Caroline
    Medicinsk teknik Örebro universitetssjukhus.
    Pettersson, Nils-Erik
    Medicinsk teknik Örebro universitetssjukhus.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    The intelligent stethoscope as a tool in modern health care2005Ingår i: Nordic Baltic Conference Biomedical Engineering and Medical Physics,2005, Umeå: IFMBE , 2005, s. 79-Konferensbidrag (Refereegranskat)
  • 120.
    Hult, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ahlström, Christer
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Rattfält, Linda
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hagström, Cecilia
    Örebro University Hospital .
    Pettersson, Nils-Erik
    Örebro University Hospital .
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    The intelligent stethoscope2005Ingår i: EMBEC05,2005, Prag: IFMBE , 2005Konferensbidrag (Refereegranskat)
  • 121.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Fjällbrant, Tore
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Detection of the third heart sound using a tailored wavelet approach2004Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, nr 2, s. 253-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The third heart sound is normally heard during auscultation of younger individuals but disappears with increasing age. However, this sound can appear in patients with heart failure and is thus of potential diagnostic use in these patients. Auscultation of the heart involves a high degree of subjectivity. Furthermore, the third heart sound has low amplitude and a low-frequency content compared with the first and second heart sounds, which makes it difficult for the human ear to detect this sound. It is our belief that it would be of great help to the physician to receive computer-based support through an intelligent stethoscope, to determine whether a third heart sound is present or not. A precise, accurate and low-cost instrument of this kind would potentially provide objective means for the detection of early heart failure, and could even be used in primary health care. In the first step, phonocardiograms from ten children, all known to have a third heart sound, were analysed, to provide knowledge about the sound features without interference from pathological sounds. Using this knowledge, a tailored wavelet analysis procedure was developed to identify the third heart sound automatically, a technique that was shown to be superior to Fourier transform techniques. In the second step, the method was applied to phonocardiograms from heart patients known to have heart failure. The features of the third heart sound in children and of that in patients were shown to be similar. This resulted in a method for the automatic detection of third heart sounds. The method was able to detect third heart sounds effectively (90%), with a low false detection rate (3.7%), which supports its clinical use. The detection rate was almost equal in both the children and patient groups. The method is therefore capable of detecting, not only distinct and clearly visible/audible third heart sounds found in children, but also third heart sounds in phonocardiograms from patients suffering from heart failure.

  • 122.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency2000Ingår i: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 22, nr 6, s. 425-433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well known that the flow of air through the trachea during respiration causes vibrations in the tissue near the trachea, which propagate to the surface of the body and can be picked up by a microphone placed on the throat over the trachea. Since the vibrations are a direct result of the airflow, accurate timing of inspiration and expiration is possible. This paper presents a signal analysis solution for automated monitoring of breathing and calculation of the breathing frequency. The signal analysis approach uses tracheal sound variables in the time and frequency domains, as well as the characteristics of the disturbances that can be used to discriminate tracheal sound from noise. One problem associated with the bioacoustic method is its sensitivity for acoustic disturbances, because the microphone tends to pick up all vibrations, independent of their origin. A signal processing method was developed that makes the bioacoustic method clinically useful in a broad variety of situations, for example in intensive care and during certain heart examinations, where information about both the precise timing and the phases of breathing is crucial.

  • 123.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Fjällbrant, T.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Hildén, Katrin
    Linköpings universitet, Institutionen för medicin och vård. Linköpings universitet, Hälsouniversitetet.
    Dahlström, Ulf
    Linköpings universitet, Institutionen för medicin och vård. Linköpings universitet, Hälsouniversitetet.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Bioacoustic detection of the third heart sound: a preliminary patient studyManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Body sounds are related to mechanical processes in the body. Thus, the heart can be seen as a sound generator and the heart sounds as mechanical fingerprints of myocardial function.

    This sound normally occurs in children but disappear with maturation. The sound can also appear in patients with heart failure. The sound is characterized by its low amplitude and low frequency content, which makes it difficult to identify by the use of the traditional stethoscope.

    We have recently developed a wavelet based method for detection of the third heart sound. Our intention with this study was to investigate if a third heart sound could be identified in patients with a diagnosis of heart failure attending the heart failure clinic using this detection method. It was also our intention to compare our method with auscultation using a conventional phonocardiography, and characterizing the patients with echocardiography.

    Using the wavelet method (study 1), 87% of the third heart sounds that were identified from the recordings (with the visual method as a reference) were detected, 12% were missed and 2% were false positive. In study 2, the wavelet detection method identified all (100%) of patients with identified third heart sound and regular phonocardiography identified 2 (13%) of the subjects.

  • 124.
    Hult, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Fjällbrant, T
    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.
    Detection of the third heart sound using a tailored wavelet approach.2004Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 42, nr 2, s. 253-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The third heart sound is normally heard during auscultation of younger individuals but disappears with increasing age. However, this sound can appear in patients with heart failure and is thus of potential diagnostic use in these patients. Auscultation of the heart involves a high degree of subjectivity. Furthermore, the third heart sound has low amplitude and a low-frequency content compared with the first and second heart sounds, which makes it difficult for the human ear to detect this sound. It is our belief that it would be of great help to the physician to receive computer-based support through an intelligent stethoscope, to determine whether a third heart sound is present or not. A precise, accurate and low-cost instrument of this kind would potentially provide objective means for the detection of early heart failure, and could even be used in primary health care. In the first step, phonocardiograms from ten children, all known to have a third heart sound, were analysed, to provide knowledge about the sound features without interference from pathological sounds. Using this knowledge, a tailored wavelet analysis procedure was developed to identify the third heart sound automatically, a technique that was shown to be superior to Fourier transform techniques. In the second step, the method was applied to phonocardiograms from heart patients known to have heart failure. The features of the third heart sound in children and of that in patients were shown to be similar. This resulted in a method for the automatic detection of third heart sounds. The method was able to detect third heart sounds effectively (90%), with a low false detection rate (3.7%), which supports its clinical use. The detection rate was almost equal in both the children and patient groups. The method is therefore capable of detecting, not only distinct and clearly visible/audible third heart sounds found in children, but also third heart sounds in phonocardiograms from patients suffering from heart failure.

  • 125.
    Hult, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Fjällbrant, Tore
    Dahle, S
    Danielsson, P
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    A method for respiration in monitoring by use of a bioacoustic signal2000Ingår i: Medical signal and information processing MEDSIP,2000, IET , 2000, s. 22-25Konferensbidrag (Refereegranskat)
    Abstract [en]

    The sound that generates during the act of respiration can be picked up by a bioacoustic sensor, a specially designed microphone. The aim of the work was to describe a method for monitoring of respiration and where the start and stop of the respiration phases can be timed accurately. A method is presented where the time position of the different respiration phases can be determined by a time resolution of 51 ms. A microphone applied over the trachea and the features of the respiration sounds frequency content was used for the development of the method

  • 126.
    Hult, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Fjällbrant, Tore
    Hildén, Karin
    Linköpings universitet, Institutionen för medicin och vård. Linköpings universitet, Hälsouniversitetet.
    Dahlström, Ulf
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Kardiologi. Östergötlands Läns Landsting, Hjärtcentrum, Kardiologiska kliniken.
    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.
    Detection of the third heart sound using a tailored wavelet approach: Method verification2005Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 43, nr 2, s. 212-217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heart sounds can be considered as mechanical fingerprints of myocardial function. The third heart sound normally occurs in children but disappears with maturation. The sound can also appear in patients with heart failure. The sound is characterised by its low-amplitude and low-frequency content, which makes it difficult to identify by the traditional use of the stethoscope. A wavelet-based method has recently been developed for detection of the third heart sound. This study investigated if the third heart sound could be identified in patients with heart failure using this detection method. The method was also compared with auscultation using conventional phonocardiography and with characterisation of the patients with echocardiography. In the first study, 87% of the third heart sounds were detected using the wavelet method, 12% were missed, and 6% were false positive. In study 2, the wavelet-detection method identified 87% of the patients using the third heart sound, and regular phonocardiography identified two (25%) of the subjects. © IFMBE: 2005.

  • 127.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Fjällbrant, Tore
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Wranne, Bengt
    Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Linköpings universitet, Hälsouniversitetet.
    Engdahl, O.
    Linköpings universitet, Institutionen för medicin och hälsa, Anestesiologi med intensivvård. Linköpings universitet, Hälsouniversitetet.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    An improved bioacoustic method for monitoring of respiration2004Ingår i: Technology and Health Care, ISSN 0928-7329, E-ISSN 1878-7401, Vol. 12, nr 4, s. 323-332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reliable monitoring of respiration plays an important role in a broad spectrum of applications. Today, there are several methods for monitoring respiration, but none of them has proved to be satisfactory in all respects. We have recently developed a bioacoustic method that can accurately time respiration from tracheal sounds. The aim of this study is to tailor this bioacoustic method for monitoring purposes by introducing dedicated signal processing. The method was developed on a material of ten patients and then tested in another ten patients treated in an intensive care unit. By studying the differences in the variation of the spectral content between the different phases of respiration, the described method can distinguish between inspiration and expiration and can extract respiration frequency, and respiration pause periods. The system detected 98% of the inspirations and 99% of the expirations. This method for respiration monitoring has the advantage of being simple, robust and the sensor does not need to be placed closed to the face. A commercial heart microphone was used and we anticipate that further improvement in performance can be achieved trough optimization of sensor design.

  • 128.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Oscarsson, Marcus
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Rattfält, Linda
    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.
    A platform for patient monitoring in home health care including an interpretation tool for heart failure patients2009Ingår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, VOL 25, PT 5, ISSN 1680-0737, Vol. 25, nr 5, s. 157-160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    About 2% of the population suffer from heart failure, which is a disease associated with high mortality. We have developed a measurement platform including an interpretation tool for heart failure patients where physiological signals can be acquired and on which 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. In this platform, we have implemented a tool for interpretation support of the data measured from the patient. This tool are intended for use in home health care as an aid for monitoring and follow up heart failure patients.

  • 129.
    Hult, Peter
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Filosofiska fakulteten.
    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.
    A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency.2000Ingår i: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 22, nr 6, s. 425-433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well known that the flow of air through the trachea during respiration causes vibrations in the tissue near the trachea, which propagate to the surface of the body and can be picked up by a microphone placed on the throat over the trachea. Since the vibrations are a direct result of the airflow, accurate timing of inspiration and expiration is possible. This paper presents a signal analysis solution for automated monitoring of breathing and calculation of the breathing frequency. The signal analysis approach uses tracheal sound variables in the time and frequency domains, as well as the characteristics of the disturbances that can be used to discriminate tracheal sound from noise. One problem associated with the bioacoustic method is its sensitivity for acoustic disturbances, because the microphone tends to pick up all vibrations, independent of their origin. A signal processing method was developed that makes the bioacoustic method clinically useful in a broad variety of situations, for example in intensive care and during certain heart examinations, where information about both the precise timing and the phases of breathing is crucial.

  • 130. HULTEN, J
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    A DEVICE FOR BLADDER PRESSURE MONITORING DURING TRANS-URETHRAL RESECTION1984Ingår i: Scandinavian Journal of Urology and Nephrology, ISSN 0036-5599, E-ISSN 1651-2065, nr 82, s. 75-80Artikel i tidskrift (Refereegranskat)
  • 131.
    Hurtig-Wennlof, A.
    et al.
    Hurtig-Wennlöf, A., School of Health and Medical Sciences/Clinical Medicine, Örebro University, SE-701 82 Örebro, Sweden.
    Ahlström, Christer
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Egerlid, R.
    Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Resare, M.
    Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Rask, P.
    Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Heart sounds are altered by open cardiac surgery2009Ingår i: Experimental and Clinical Cardiology, ISSN 1205-6626, Vol. 14, nr 2, s. 18-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND AND OBJECTIVE: Patients have reported that they perceive their own heart sounds differently after open cardiac surgery than before the surgery. The present study was designed to investigate whether changes in heart sounds can be quantitatively measured. METHOD: Heart sounds were recorded from 57 patients undergoing coronary artery bypass graft (CABG) surgery and from a control group of 10 subjects. The so-called Hjorth descriptors and the main frequency peak were compared before and after surgery to determine whether the characteristics of the heart sounds had changed. RESULTS: At a group level, the first heart sound was found to be significantly different after CABG surgery. Generally, the heart sounds shifted toward a lower frequency after surgery in the CABG group. No significant changes were found in the control group. CONCLUSIONS: Heart sounds are altered after CABG surgery. The changes are objectively quantifiable and may also be subjectively perceived by the patients.

  • 132. Imura, M
    et al.
    Kuroda, T
    Oshiro, O
    Chihara, K
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    3-D flow visualization for construction of the model of the blood flow in the heart2000Ingår i: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 39, nr 5 B, s. 3246-3251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The authors have been developing a model of blood flow in the heart. The flow model of the heart enables us to estimate the entire blood flow of the heart from a couple of 2-D color Doppler images. Therefore, the load on patients is expected to be reduced. To develop the model of the heart, precise observation and an understanding of the blood flow are indispensable, because the flow is strongly related to the diagnosis of heart diseases. The visualization method must have the following features: (1) 3-D (2) objectivity (3) interactivity and (4) multi-aspect. The authors have developed visualization methods to meet the above-mentioned requirements and evaluated the proposed methods with the in-vitro flow data set. The results clearly reveal that the proposed system enables the researchers of the modeling group to obtain the state of entire flow, such as the occurrence of turbulence.

  • 133.
    Imura, M
    et al.
    Nara Inst of Science and Technology Nara, Japan.
    Kuroda, T
    Nara Inst of Science and Technology Nara, Japan.
    Oshiro, O
    Nara Inst of Science and Technology Nara, Japan.
    Chihara, K
    Nara Inst of Science and Technology Nara, Japan.
    Brandberg, Joakim
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    In-vitro blood flow visualization using 3-D reconstructionn of color doppler images2000Ingår i: Image and Graphic Technology toward 21 Century and Beyound,2000, 2000, s. 496-Konferensbidrag (Refereegranskat)
  • 134. Imura, Masataka
    et al.
    Kuroda, Tomohiro
    Oshiro, O
    Chihara, Kunihiro
    Brandberg, John
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Blood flow visualization in immersive environment based on color Doppler images2001Ingår i: PROCEEDINGS OF THE 23RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-4: BUILDING NEW BRIDGES AT THE FRONTIERS OF ENGINEERING AND MEDICINE, 2001, Vol. 23, s. 3167-3170Konferensbidrag (Refereegranskat)
    Abstract [en]

    An accurate grasp of blood flow patterns in a human heart is important to evaluate cardiac diseases of patients. Doppler ultrasound method is widely used to visualize blood flow patterns and has obtained excellent results in diagnosis. However, the output from Doppler ultrasound method is usually represented as a two-dimensional image, though blood flow patterns have three-dimensional complex structure and change dynamically. Therefore, improvement of both data acquisition and data visualization techniques is indispensable to diagnosis of cardiac faculty. It is worth mentioning that visualization also dominates the level of understanding as data acquisition, because poor visualization ruins the value of the most accurate result of measurement as if it were nothing. The authors construct an interactive visualization system suitable for three-dimensional blood flow, utilizing the immersive projection display. With the developed visualization system, which possesses interactivity and a wide field of view, users can easily understand the state of entire flow, such as the occurrence of turbulence, and the patterns of blood flow.

  • 135.
    Janerot-Sjöberg, Birgitta
    et al.
    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.
    Subaortic flow profile in aortic valve disease - a two dimensional color Doppler study1994Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 7, s. 276-284Artikel i tidskrift (Refereegranskat)
  • 136.
    Johansson, Anders
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Ahlström, Christer
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Länne, Toste
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Thorax-kärlkliniken.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Pulse wave transit time for monitoring respiration rate2006Ingår i: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 44, nr 6, s. 471-478Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring. © International Federation for Medical and Biological Engineering 2006.

  • 137. Johansson, K E
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Boeryd, B
    Fransson, S G
    Tibbling, Lita
    Oesophagitis, signs of reflux, and gastric acid secretion in patients with symptoms of gastro-oesophageal reflux disease.1986Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 21, nr 7, s. 837-847Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a study comprising 100 patients referred to a surgical clinic with symptoms suggestive of gastro-oesophageal reflux disease the value of different diagnostic procedures was investigated. Positive acid perfusion and 24-h pH tests were the commonest findings. Forty-nine per cent showed a normal oesophageal mucosa or diffuse oesophagitis at endoscopy. The severity of heartburn and regurgitation did not differ between patients with normal oesophageal mucosa and oesophagitis of various severities. The severity of macroscopic oesophagitis was significantly correlated to the total reflux time, the presence of reflux or a hiatal hernia at radiology, an open cardia or reflux at endoscopy, pressure transmission or reflux and low lower oesophageal sphincter pressure at manometry. Gastric hypersecretion was found in 66% of the patients. Gastric acid secretion was not correlated to the severity of oesophagitis or to the findings at 24-h pH test. In patients with severe oesophagitis the sensitivity for radiologic, manometric, and endoscopic signs of incompetence of the gastro-oesophageal junction was 94%.

  • 138.
    Johansson, K. E.
    et al.
    Östergötlands Läns Landsting.
    Ask, Per
    Östergötlands Läns Landsting.
    Boeryd, B.
    Östergötlands Läns Landsting.
    Fransson, Sven-Göran
    Östergötlands Läns Landsting.
    Tibbling, L.
    Östergötlands Läns Landsting.
    Oesophagitis, signs of reflux, and gastric acid secretion in patients with symptoms of gastro-oesophageal reflux disease1986Ingår i: Scandinavian Journal of Gastroenterology, ISSN 0036-5521, E-ISSN 1502-7708, Vol. 21, nr 7, s. 837-847Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a study comprising 100 patients referred to a surgical clinic with symptoms suggestive of gastro-oesophageal reflux disease the value of different diagnostic procedures was investigated. Positive acid perfusion and 24-h pH tests were the commonest findings. Forty-nine per cent showed a normal oesophageal mucosa or diffuse oesophagitis at endoscopy. The severity of heartburn and regurgitation did not differ between patients with normal oesophageal mucosa and oesophagitis of various severities. The severity of macroscopic oesophagitis was significantly correlated to the total reflux time, the presence of reflux or a hiatal hernia at radiology, an open cardia or reflux at endoscopy, pressure transmission or reflux and low lower oesophageal sphincter pressure at manometry. Gastric hypersecretion was found in 66% of the patients. Gastric acid secretion was not correlated to the severity of oesophagitis or to the findings at 24-h pH test. In patients with severe oesophagitis the sensitivity for radiologic, manometric, and endoscopic signs of incompetence of the gastro-oesophageal junction was 94%.

  • 139. JOHANSSON, KE
    et al.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    EDWALL, G
    Tibbling, Lita
    A PORTABLE UNIT FOR 24-HOUR ESOPHAGEAL PH MONITORING WITH ANTIMONY ELECTRODES1981Ingår i: ACTA CHIRURGICA SCANDINAVICA, ISSN 0001-5482, nr 506Artikel i tidskrift (Refereegranskat)
  • 140. Karlsson, M
    et al.
    Brandberg, J
    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.
    Loyd, Dan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Computer simulation for improved assessment of mitral regurgitation.1997Ingår i: COMPUTERS IN CARDIOLOGY 1997, VOL 24, 1997, Vol. 24, s. 169-170Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since valvular regurgitation is one of the most common malfunctions of the heart the quantification of valvular regurgitation by means of non-invasive methods is desired. However existing methods for quantitative assessment is far from perfect. The aim of this paper is to study the proximal velocity field for non-stationary flow and non-planar geometries by computer simulation, which were performed using the FIDAP package to numerically solve the governing equations. A plexiglass in-vitro model similar to the computer model was used for comparison and the same results were obtained. We have found that it is possible to refine the PISA method and standardize flow calculations. Further improvements will hopefully create a tool for the echocardiographer that will facilitate evaluation and clinical applicability of the PISA approach.

  • 141.
    Karlsson, Matts
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Engvall, Jan
    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.
    Wranne, Bengt
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och vård, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Orifice flow in stenotic and regurgitant valve lesions - Modelling and computer simulations1994Ingår i: Biofluid mechanics, Southhampton: Computational Mechanics Publications , 1994Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 142.
    Karlsson, Matts
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk modellering och simulering.
    Loyd, Dan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanisk värmeteori och strömningslära.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Lindström, K
    Elmqvist, Håkan
    CORTECH tutor - a distributed biomedical engineering graduate training initiative1999Ingår i: The 1st Joint Meeting of BMES and EMBS,1999, 1999Konferensbidrag (Övrigt vetenskapligt)
  • 143.
    Kvikliene, Adriana
    et al.
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Jurkonis, Rytis
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Ressner, Marcus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Hoff, Lars
    Faculty of Science and Engineering, Vestfold University College, P.O. Box 2243, N-3103 Tønsberg, Norway.
    Jansson, Tomas
    Department of Electrical Measurements, Lund University, P.O. Box 118, SE-221 00, Lund, Sweden.
    Janerot Sjöberg, Birgitta
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för medicin och hälsa, Klinisk fysiologi. Östergötlands Läns Landsting, Hjärtcentrum, Fysiologiska kliniken.
    Lukosevicius, Arunas
    Institute of Biomedical Engineering, Kaunas University of Technology, K. Donelaicio st. 73, Kaunas LT-3006, Lithuania.
    Ask, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik.
    Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment2004Ingår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 42, nr 01-Sep, s. 301-307Artikel i tidskrift (Refereegranskat)
    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.

  • 144. Lepper, W
    et al.
    Flachskampf, F A
    Köhler, J
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hanrath, P
    [Overestimation of regurgitation velocities of intact mechanical heart valve prostheses and other small orifices with 10 mm2 Doppler echocardiography].1997Ingår i: Zeitschrift für Kardiologie, ISSN 0300-5860, E-ISSN 1435-1285, Vol. 86, nr 5, s. 354-362Artikel i tidskrift (Refereegranskat)
    Abstract [de]

    A systematic evaluation of the accuracy of continuous wave echo Doppler measurements across prosthetic valve leakages and regurgitant lesions has not been performed. Continuous echo Doppler velocity measurements in an in vitro, steady flow model, across the leaks of 12 intact mechanical prostheses and across six circular nozzles (area, 0.5-20 mm2) at pressure drops between 30 and 105 mm Hg were analyzed and compared to the velocities predicted by the modified Bernoulli equation. Laser Doppler anemometry of flow velocities through the nozzles was performed in addition. Despite excellent correlation, there was substantial overestimation of "Bernoulli predicted"-velocities by echo Doppler in the prosthetic leaks (mean +12.3 +/- 9.4%; range, 90.3-143.4%). Also in nozzles < or = 10 mm2, but not in those > 20 mm2, an overestimation of the "Bernoulli predicted"-velocities was observed (mean +6.2 +/- 2%). Laser Doppler anemometry of flow velocities through the nozzles showed slightly lower values than predicted by the Bernoulli equation. This effect apparently is due to transit time effects leading to spectral broadening and should be taken into account when using echo Doppler measurements in very small (< 10 mm2) orifices, such as mild to moderate regurgitant lesions and prosthetic valve leakage.

  • 145.
    Ljungvall, Ingrid
    et al.
    Swedish University of Agriculture Science.
    Ahlström, Christer
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Hoglund, Katja
    Swedish University of Agriculture Science.
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Kvart, Clarence
    Swedish University of Agriculture Science.
    Borgarelli, Michele
    Kansas State University.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Haggstrom , Jens
    Swedish University of Agriculture Science.
    Use of signal analysis of heart sounds and murmurs to assess severity of mitral valve regurgitation attributable to myxomatous mitral valve disease in dogs2009Ingår i: AMERICAN JOURNAL OF VETERINARY RESEARCH, ISSN 0002-9645 , Vol. 70, nr 5, s. 604-613Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective-To investigate use of signal analysis of heart sounds and murmurs in assessing severity of mitral valve regurgitation (mitral regurgitation [MR]) in dogs with myxomatous mitral valve disease (MMVD).

    Animals-77 client-owned dogs.

    Procedures-Cardiac sounds were recorded from dogs evaluated by use of auscultatory and echocardiographic classification systems. Signal analysis techniques were developed to extract 7 sound variables (first frequency peak, murmur energy ratio, murmur duration > 200 Hz, sample entropy and first minimum of the auto mutual information function of the murmurs, and energy ratios of the first heart sound [S1] and second heart sound [S2]).

    Results-Significant associations were detected between severity of MR and all sound variables, except the energy ratio of S1. An increase in severity of MR resulted in greater contribution of higher frequencies, increased signal irregularity, and decreased energy ratio of S2. The optimal combination of variables for distinguishing dogs with high-intensity murmurs from other dogs was energy ratio of S2 and murmur duration > 200 Hz (sensitivity, 79%; specificity, 71%) by use of the auscultatory classification. By use of the echocardiographic classification, corresponding variables were auto mutual information, first frequency peak, and energy ratio of S2 (sensitivity, 88%; specificity, 82%).

    Conclusions and Clinical Relevance-Most of the investigated sound variables were significantly associated with severity of MR, which indicated a powerful diagnostic potential for monitoring MMVD. Signal analysis techniques could be valuable for clinicians when performing risk assessment or determining whether special care and more extensive examinations are required.

  • 146.
    Ljungvall, Ingrid
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska högskolan.
    Ahlström, Christer
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Höglund, Katja
    Hult, Peter
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Kvart, Clarence
    Borgarelli, Michele
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. Linköpings universitet, Tekniska högskolan.
    Häggström, Jens
    Assessing mitral regurgitation attributable to myxomatous mitral valve disease in dogs using signal analysis of heart sounds and murmurs2008Artikel i tidskrift (Refereegranskat)
  • 147.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. 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.
    Doppler prediction of transvalvular gradient and stenotic orifice area.1988Ingår i: American Journal of Cardiology, ISSN 0002-9149, E-ISSN 1879-1913, Vol. 61, nr 11, s. 958-959Artikel i tidskrift (Refereegranskat)
  • 148.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. 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.
    MITRAL PRESSURE HALF-TIME TECHNIQUE FOR ASSESSING SEVERITY OF MITRAL-STENOSIS - ESSENTIAL PARAMETERS1989Ingår i: IMAGES OF THE TWENTY-FIRST CENTURY, PTS 1-6, 1989, Vol. 11Konferensbidrag (Refereegranskat)
    Abstract [en]

    The flow through a stenotic mitral valve, which is mainly determined by the cross-sectional area of the valve and the pressure difference across it, is discussed. The gradient half-time is an attempt to describe the area from the decline in transmitral pressure difference alone. The gradient half-time increases with increasing severity of the stenosis. Besides the area of the mitral valve, there are other factors influencing the gradient half-time. Such factors are the transported volume and the initial pressure gradient. The compliance of the cardiac chambers and the pulmonary venous flow also influence the gradient half-time, but through changes in the pressure difference across the valve. The problem can therefore be analyzed either with or without inclusion of compliance in the calculations

  • 149.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. 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.
    Pressure half-time does not always predict mitral valve area correctly.1988Ingår i: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 1, nr 5, s. 313-321Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A theory is presented elucidating factors that influence the pressure half-time. By combining the Bernoulli and continuity equations and making certain assumptions about the shape of the atrioventricular pressure difference decay, it can be shown that valve area, volume transported across that area, and initial pressure difference influence the pressure half-time according to a formula in which the pressure half-time is related to V/(Ao square root of delta po), where V is the transported volume across the orifice with the area Ao, and delta po is the initial pressure difference across that area. In a subsequent hydraulic model experiment pressure half-time was determined for three different hole areas, with various initial volumes and initial pressure gradients. We did not obtain a unique relation between the pressure half-time and area. Instead the results supported our theory, and we found a close linear relationship between area and V/(T0.5 square root of delta po) (correlation coefficient [r] = 0.998), as predicted in the theory (T0.5 = pressure half-time). Clinical examples in which the pressure half-time may be misleading in the assessment of severity of mitral stenosis are presented.

  • 150.
    Loyd, Dan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    BARCLAY, SA
    XIONG, Changsheng
    ANDERSSON, Gunnar
    Ask, Per
    Linköpings universitet, Institutionen för medicinsk teknik, Fysiologisk mätteknik. 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.
    ECHOCARDIOGRAPHIC ASSESSMENT OF HEART-VALVE REGURGITANT FLOW USING THE FLOW CONVERGENCE METHOD1991Ingår i: PROCEEDINGS OF THE ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOL 13, PTS 1-5, 1991, s. 191-192Konferensbidrag (Refereegranskat)
12345 101 - 150 av 208
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf