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  • 251.
    Thulesius, Olav
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Thermal reactions of blood vessels in vascular stroke and heatstroke2006In: Medical principles and practice, ISSN 1011-7571, E-ISSN 1423-0151, Vol. 15, no 4, p. 316-321Article in journal (Refereed)
    Abstract [en]

    Research on the pathophysiology and treatment of brain damage with special focus on thermal vascular responses is the subject of this minireview. Interruption of cerebral blood supply by vascular obstruction, temporary cardiac arrest or hyperthermia causes a sudden attack of vascular stroke or heatstroke with serious consequences. It may not induce immediate cell death, but can precipitate a complex biochemical cascade leading to a delayed neuronal loss. When testing thermal vasomotor responses by stepwise cooling of isolated carotid arteries, a temperature-proportional dilatation was observed while heating induced the opposite response: a marked vasoconstriction. General hyperthermia with an increased oxygen demand combined with a reduction of blood supply therefore is a serious consequence. At the cellular level an important mechanism involving hyperthermia is the temperature-dependent regulation of K+ channel tone of vascular smooth muscle. Further, their inhibition through temperature elevation causes vasoconstriction. In heatstroke, which can induce platelet aggregation and the release of the vasoconstrictor serotonin, arterial cooling attenuates this response. General hypothermia is induced to prevent or attenuate neurological damage in stroke. The procedure is not without serious side effects. Therefore, rapid institution of selective brain cooling has been considered in adults and in infants with postpartum encephalopathy. Copyright © 2006 S. Karger AG.

  • 252.
    Thulesius, Olav
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Waddell, William J
    Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, KY USA.
    Human exposures to acrylamide are below the threshold for carcinogenesis2004In: Human and Experimental Toxicology, ISSN 0960-3271, E-ISSN 1477-0903, Vol. 23, no 7, p. 357-358Article in journal (Refereed)
    Abstract [en]

    Dose-response calculations for a threshold of carcinogenesis in animal studies do not support the notion that acrylamide (ACR) with the present status of consumption in food is carcinogenic for humans. This is in agreement with the recent reassuring epidemiological studies which have shown a lack of correlation between exposure to ACR in food and the incidence of cancer. © Arnold 2004.

  • 253.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Accuracy and reproducibility in phase contrast imaging using SENSE2003In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 50, no 5, p. 1061-1068Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to evaluate the accuracy and reproducibility of phase contrast imaging using the sensitivity encoding (SENSE) method at different reduction factors. Analytical expressions were derived that state how reproducibility is influenced for velocity and flow measurements. Computer simulations, and in vitro and in vivo studies were performed in order to validate these expressions and to assess how accuracy is affected when different reduction factors are applied. It was shown that reproducibility depends on the reduction and geometry factors. Since the geometry factor varies spatially, so does the reproducibility for phase contrast imaging. In areas with high geometry factors, the standard deviation (SD) may become so large that aliasing occurs. The accuracy of phase contrast imaging is not influenced directly when SENSE is used, but may be indirectly influenced due to high SDs of the measured phase that may subsequently cause aliasing. The current results show that it is possible to achieve accurate flow measurements even at high reduction factors. By taking the geometry factor into account, it may be possible to find areas where phase contrast imaging is accurate even at high reduction factors.

  • 254.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Comparison of different methods for combining phase-contrast images obtained with multiple coils2005In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 23, no 7, p. 795-799Article in journal (Refereed)
    Abstract [en]

    The ability to determine coil sensitivities implies that a method optimized in terms of maximized signal-to-noise ratio (SNR) can be applied to the combination of multiple coil images. An optimization of SNR subsequently results in a minimized variance in quantitative velocity measurements using phase-contrast imaging. When coil sensitivities are unknown, the weighted mean method, utilizing the square of the signal magnitude as weights, is suitable for combination of multiple phase images. In this study, the optimized method using estimated coil sensitivities was compared to the weighted mean method both theoretically and experimentally. It is shown that absence of noise correlation between the different coil images implies no difference between the methods regarding the variance of the phase. In the practical situation, noise correlation does exist, implying an opportunity for further reduction of phase variance using the optimized method. In vitro and in vivo studies showed, however, no significant difference between the two methods studied.

  • 255.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Optimization of gradient waveforms for velocity measurements and concurrent reduction of displacement artifacts in phase contrast imagingManuscript (preprint) (Other academic)
    Abstract [en]

    The purpose of the present study was to develop gradient waveforms for phase contrast magnetic resonance imaging that provides concurrent reduction of displacement artifacts. A framework was developed which was based on a linear combination of three individual gradients, each gradient having a trapezoidal shape. The amplitude of each gradient trapezoid was determined by the desired values of the zeroth, first and second moments of the combined tripolar waveform. All calculations of moments of the tripolar gradient waveform were performed with the expansion point set equal to the echo time. The times of spatial and velocity encoding are simultaneous in all three encoding directions, implying elimination of the displacement artifact. The proposed phase contrast pulse sequence using tripolar gradients was compared to a conventional phase contrast pulse sequence based on bipolar gradients. The echo time increased with the use of tripolar gradients compared to the conventional pulse sequence. Compensation for the increase in scan time can be achieved with the use of parallel imaging techniques.

  • 256.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Ebbers, Tino
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Correction for displacement artifacts in 3D phase contrast imaging2002In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 16, no 5, p. 591-597Article in journal (Refereed)
    Abstract [en]

    Purpose

    To correct for displacement artifacts in 3D phase contrast imaging.

    Materials and Methods

    A 3D phase contrast pulse sequence was modified so that displacements of velocity measurements were restricted to one direction. By applying a postprocessing method, displaced measurements could be traced back to their accurate positions. Flow studies were performed using a phantom that generated flow through a stenosis, directed oblique relative to the phase and frequency encoding directions. Velocity profiles and streamline visualization were used to compare displaced and corrected velocity data to a reference.

    Results

    Velocity profiles obtained from the original measurement showed skewed profiles due to the displacement artifact, both at close proximity to the orifice as well as further downstream. After correction, concordance with the reference improved considerably.

    Conclusion

    The displacement artifact, which restricts the accuracy of phase contrast measurements, can be corrected for using the proposed method. Correction of the phase contrast velocity data may improve the accuracy of subsequent flow analysis and visualization.

  • 257.
    Thunberg, Per
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wigström, Lars
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Engvall, Jan
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Correction for acceleration-induced displacement artifacts in phase contrast imaging2000In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 43, no 5, p. 734-738Article in journal (Refereed)
    Abstract [en]

    The acceleration-induced displacement artifact impairs the accuracy of MR velocity measurements. This study proposes a post processing method for correction of this artifact. Velocity measurements were performed in a flow phantom containing a constriction. Velocity curves were obtained from streamlines parallel to the frequency, phase, and slice directions, respectively. The acceleration-induced displacement artifact was most prominent when the frequency encoding direction was aligned with the flow direction. After correction, velocity assignment improved and a more accurate description of the flow was obtained. In vivo measurements were performed in the aorta in a patient with a repaired aortic coarctation. The correction method was applied to velocity data along a streamline parallel to the frequency encoding direction. The result after correction was a new location of the peak velocity and improved estimates of the velocity gradients.

  • 258.
    Thyberg, Mikael
    Linköping University, Department of health and environment. Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Department of Medical and Health Sciences, Rehabilitation Medicine. Linköping University, Faculty of Health Sciences.
    Urodynamic evaluation of detrusor pressure and blood pressure reaction in patients with a reflux urinary bladder after spinal cord injury1994Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on urodynamic evaluation of variables that are associated with the risk of upper urinary tract dysfunction and autonomic dysreflexia in patients with a reflex urinary bladder after spinal cord injury. The detrusor pressure was measured with suprapubic catheters during 24 or 12 hours of physiological filling (diuresis) and during consecutive cystometries. Within the ftlled volumes the bladder compliance was high. During contractions the maximum detrusor pressure and its duration varied both interand intraindividually. Thus, mean values from a series of contractions seem to be necessary in order to characterize a patient. There was no difference between mean values during physiological filling compared with 10 rnl/min or 50 ml/min fill cystometry and there was no systematic change during a series of four consecutive cystornetries with a 10 min interval. When a closed 12F urethral catheter was added in order to mimick a transurethral urodynamic techrtique, there was an increase of the amplitude and duration of the detrusor pressure and a decrease of the average flow rate, indicating an obstructive effect. In patients with a high level spinal cord injury, the blood pressure was also measured every 30 s, during a series of four consecutive cystometries. In each cystometry there was an elevation of the systolic and diastolic blood pressure. The maximum blood pressure was always observed during the detrusor contraction. The amplitude of the blood pressure response varied intraindividually but did not change in any particular direction during the series of cystometries. When 10 mg rtifedipine was given sublingually, and a series of four cystometries was repeated, there was a sigrtificant decrease of the maximum blood pressure.

  • 259. Tuchnitz, A
    et al.
    Schmitt, C
    von Bibra, H
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Schneider, MA
    Plewan, A
    Schörmig, A
    Non-invasive localization of accessory in patients with Wolff-Parkinson - with syndrome using myocardial doppler imaging.1999In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 12, p. 32-40Article in journal (Refereed)
  • 260. Turesson, C
    et al.
    Jacobsson, L
    Rydén Ahlgren, Å
    Sturfelt, G
    Wollmer, P
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Increased stiffness of the abdominal aorta in women with rheumatoid arthritis2005In: Rheumatology, ISSN 1462-0324, E-ISSN 1462-0332, Vol. 44, no 7, p. 896-901Article in journal (Refereed)
    Abstract [en]

    Objective. To study the distensibility and the diameter of the abdominal aorta and the common carotid artery (CCA) in patients with rheumatoid arthritis (RA), and investigate the relation between mechanical properties of these arteries and disease severity. Methods. One hundred and one patients with RA (33 consecutive cases with extra-articular manifestations, and 68 subjects with non-extra-articular disease, matched for age, sex and disease duration) were investigated. Echo-tracking ultrasonography was used to measure stiffness and mean diameter of the abdominal aorta and the CCA. The patients were compared with healthy individuals from the corresponding age group (n=74 for measurements of the aorta, n = 64 for the CCA). Predicted values for stiffness and mean diameter, based on age and sex, were calculated. Results. Stiffness of the abdominal aorta was increased in women with RA [mean percentage of predicted value (% predicted) 180, 95% confidence interval (95% CI) 150-211] but not in men (% predicted 99, 95% CI 75-122). CCA stiffness was less markedly increased, and mean diameters of the aorta and the CCA were not different from the expected. In the RA cohort, patients with extra-articular manifestations tended to have greater stiffness of the aorta (P = 0.11), and disability, as indicated by a higher Health Assessment Questionnaire score, was associated with increased aortic stiffness (P = 0.04). Conclusion. RA is associated with decreased distensibility of the abdominal aorta in females, and such changes seem to correlate with disease severity. We suggest that arterial stiffness is an important factor in cardiovascular co-morbidity in RA. © The Author 2005. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.

  • 261.
    Valladares, Carlos
    et al.
    Kardiologiska kliniken Hjärtcentrum.
    Broqvist, Mats
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Nylander, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Callander, Margarita
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Neuroscience and Locomotion, Neurology. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Var det paradoxal embolism? Cerebellär infarkt, öppetstående foramen ovale och APC-resistens - en kontroversiell kombination och terapeutisk utmaning2006In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 103, p. 845-848Article in journal (Other academic)
  • 262.
    Voigt, Jens-Uwe
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Arnold, Martina
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Hübbert, Laila
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Kukulski, Tomasz
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Hatle, Liv
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology.
    Sutherland, George
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Assessment of regional longitudinal myocardial strain rate derived from Doppler myocardial imaging indexes in normal and infarcted myocardium.2000In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 13, p. 588-598Article in journal (Refereed)
  • 263. von Bibra, Helene
    et al.
    Bone, D
    Voigt, Jens-Uwe
    Niklasson, U
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ryden, Lars
    Contrast echocardiography2000In: Zeitschrift für Kardiologie, ISSN 0300-5860, E-ISSN 1435-1285, Vol. 89, p. 86-96Article in journal (Refereed)
    Abstract [en]

    The intravenous application of an ultrasound contrast agent induces enhanced display of blood in all its pathways. Within cardiology, this principle is mainly utilized for signal enhancement of color Doppler and spectral Doppler in order to improve quantification of congenital and acquired valvular lesions and also for improved endocardial delineation during stress tests and in the evaluation of LV function. The new domaine of myocardial perfusion imaging by contrast echocardiography, however, needed profound technical developments before realization of the clinical potential could even be conceived. These are based on the complex reactions of microbubbbles in the acoustic field in order to allow the sensitive and bubble specific display of intramyocardial contrast effects. The presently available acquisition techniques, second harmonic imaging and harmonic power Doppler, demonstrate significant improvements if compared to traditional fundamental 2-d echocardiography, however, they are still subjected to important limitations. There are many anatomical, physiological, and technical reasons for insufficient display of intramyocardial microbubbles, the most important one being attenuation. It is hoped that the most recently developed imaging modality, pulse inversion technique, allows the necessary diagnostic accuracy and reproducibility in myocardial perfusion imaging.

  • 264.
    von Bibra, Helene
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Voigt, J-U
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Fröman, M
    Bone, D
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Juhlin-Dannfeldt, A
    Interaction of microbubbles with ultrasound.1999In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 16, p. 733-741Article in journal (Refereed)
  • 265.
    Vánky, Farkas
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Håkansson, Erik
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Anaesthesiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Szabó, Zoltán
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Nylander, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Jorfeldt, Lennart
    Svedjeholm, Rolf
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Thoracic Surgery. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Myocardial metabolism and energetics before and after valve replacement for aortic stenosis2005In: Scandinavian Association for Thoracic Surgery,2005, 2005Conference paper (Other academic)
  • 266.
    Walker, Andrew
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Olsson, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ringqvist, Ivar
    Centrallasarettet i Västerås.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    Accuracy of spectral Doppler flow and tissue velocity measurements in ultrasound systems2004In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 30, no 1, p. 127-132Article in journal (Refereed)
    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.

  • 267.
    Walker, Andrew
    et al.
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Olsson, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ringqvist, Ivar
    Västerås.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering.
    Time delays in ultrasound systems can result in fallacious measurements.2002In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 28, p. 259-263Article in journal (Refereed)
    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.

  • 268.
    Wall, Kent
    et al.
    Department of Clinical Physiology, Örebro University Hospital, Örebro, Sweden.
    Oddsson, Hjörtur
    Department of Internal Medicine, Örebro University Hospital, Örebro, Sweden.
    Ternestedt, Britt-Marie
    Department of Health Care Science, Ersta Sköndal University College, Stockholm, Sweden.
    Jonzon, Anders
    Department of Pediatrics, Uppsala University Hospital, Uppsala, Sweden.
    Nylander, Eva
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Schollin, Jens
    Department of Pediatrics, Örebro University Hospital, Örebro, Sweden.
    Thirty-year electrocardiographic follow-up after repair of tetralogy of Fallot or atrial septal defect2007In: Journal of Electrocardiology, ISSN 0022-0736, E-ISSN 1532-8430, Vol. 40, no 2, p. 214-217Article in journal (Refereed)
    Abstract [en]

    Background and Purpose Knowledge about long-term electrocardiographic changes after surgery for congenital heart disease is limited.

    Methods Eleven patients with corrected tetralogy of Fallot (ToF) and 14 with corrected atrial septal defect (ASD) were followed up at 20 and 30 years after surgery.

    Results Approximately 50% of the ASD group developed prolonged QRS duration. In the ToF group, 7 increased QRS duration by more than 20 milliseconds. Nearly all had right bundle-branch block, and 30% of them also had bifascicular block. Two in the ASD group developed first grade atrioventricular block. Five ASD and 6 ToF had prolonged corrected QT duration in the late postoperative phase.

    Conclusions Even after primarily good results of surgery in congenital heart disease, unknown late effects may occur not only in complex lesions such as ToF but also after ASD correction. Regular medical checkups are important after surgical correction in congenital heart disease.

  • 269.
    Wandt, Birger
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Mitral Ring Motion in Assessment of Left Ventricular Function1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The motion of the mitral ring was studied with M-mode echocardiography using the apical four- and two-chamber views.

    With the purpose of obtaining adequate reference materials for mitral ring motion, 70 healthy subjects were studied. Stepwise multiple regression analysis with age, gender, height, weight, body i surface area and heart rate as independent variables, showed that ring motion amplitude (mm) is best i described as 2.2 + 0.078 x height (cm) (SD = 1.0 mm) in subjects under age 18, and as 12.7- 0.060 [ x age (years)+ 0.031 x height (cm) (SD = 1.2 mm) in subjects over age 18, or if only age is taken ! into account as 18.4-0.065 x age (SD = 1.2 mm).

    Both in children and adults the atrial contribution to the total mitral ring motion was best described as 0.15 + 0.0039 x age (SD = 0.027).

    Comparison between the four sites of measuring showed that the mitral ring "tilts" slightly during the systolic motion towards the apex. The septal point moved significantly less than the lateral point (p<O.OOl).

    In 20 healthy subjects changes in mitral ring motion and in short axis contractions with respiration was studied. It was shown that the decrease in left ventricular stroke volume on inspiration is a net effect of decrease in diastolic short axis diameter by 4.8% (p<0.001) and an increase in mitral ring motion by 5.5% (p<0.001).

    In 40 healthy subjects aged 18 - 70 years changes in long axis and short axis contraction with increasing age was studied. It was shown that from age 18 to age 70 the long axis systolic shortening[ decreases by 20% (p<0.001) and minor axis shortening increases by 18% (p=0.012). These findings have important implications for the calculation of ejection fraction (EF) from M-mode measurements.

    In 16 patients with left ventricular hypertrophy because of hypertension or hypertrophic cardiomyopathy, ejection fraction calculations were made by Teichholz' formula, by the equation EF 1'[ (%)=mitral ring motion (mm) x 5 and by Simpson .. s rule. Radionuclide angiography was used as , gold standard for ejection fraction. The study showed that in patients with hypertrophy Teichholz .. formula overestimates ejection fraction by 10% (6.7 EF%) (p--Q.002). Calculation by using mitral ring motion x 5 underestimates the ejection fraction by 19.3% ( 12.9 EF%) (p=0.002). Compared to healthy controls the hypertrophy group had 28.9% decreased mitral ring motion (p<O.OOl), while there was no significant difference in short axis systolic diameter shortening.

    Maximal longitudinal diastolic relaxation velocity was investigated in 22 patients on day 3-21 after first transmural myocardial infarction. The maximal diastolic slope was measured on the M-mode recording from the mitral ring motion. Compared to healthy controls the patients had significantly decreased relaxation velocity (p<O.OOl), while there was no significant difference in the E/A ratio of inflow over the mitral valve by pulsed Doppler.

  • 270.
    Wandt, Birger
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Bojö, L
    Tolhagen, K
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Echocardiographic assessment of ejection fraction in left ventricular hypertrophy.1999In: Heart, ISSN 1355-6037, E-ISSN 1468-201X, Vol. 82, p. 192-198Article in journal (Refereed)
  • 271.
    Warntjes, J.B.M.
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Novel method for rapid, simultaneous T1, T*2, and proton density quantification2007In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 57, no 3, p. 528-537Article in journal (Refereed)
    Abstract [en]

    An imaging method called “quantification of relaxation times and proton density by twin-echo saturation-recovery turbo-field echo” (QRAPTEST) is presented as a means of quickly determining the longitudinal T1 and transverse T relaxation time and proton density (PD) within a single sequence. The method also includes an estimation of the B1 field inhomogeneity. High-resolution images covering large volumes can be achieved within clinically acceptable times of 5–10 min. The range of accuracy for determining T1, T, and PD values is flexible and can be optimized relative to any anticipated values. We validated the experimental results against existing methods, and provide a clinical example in which quantification of the whole brain using 1.5 mm3 voxels was achieved in less than 8 min.

  • 272.
    Wernstedt, Pernilla
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Sjöstedt, Camilla
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Ekman, Inger
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Du, Hongkai
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Thuomas, Karl Åke
    Sabbatsberg.
    Areskog, Nils Holger
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Nylander, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Adaptation of cardiac morphology and function to endurance and strength training: A comparative study using MR imaging and echocardiography in males and females2002In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Vol. 12, no 1, p. 17-25Article in journal (Refereed)
    Abstract [en]

    Left ventricular (LV) dimensions and function and maximal oxygen uptake (VO2 max) were measured in endurance-trained (10 male, m, 10 female, f), strength-trained athletes (8 m, 10 f) and untrained subjects (9 m, 10 f). LV dimensions were measured using magnetic resonance imaging (MRI) and echocardiography and the results were equal irrespective of method. Endurance-trained m and f had significantly higher LV volumes and mass than both strength-trained and controls. No VO2 max or dimensional differences were seen between strength-trained and untrained subjects. In endurance-trained males, LV volumes and mass/kg bw were higher than in endurancetrained females. There was no significant gender difference for strength-trained or untrained subjects regarding body weight-related heart dimensions. It is concluded that LV dimensions and volumes are strongly dependent on oxygen transport capacity in normal subjects practising different modes of training, and that the gender differences, if LV dimensions are related to aerobic work capacity, are smaller than previously reported.

  • 273.
    Westin, Carl-Fredrik
    et al.
    Surgical Planning Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
    Wigström, Lars
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Health Sciences.
    Loock, Tomas
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Department of Medicine and Care, Radiology. Linköping University, Faculty of Health Sciences.
    Sjöqvist, Lars
    Linköping University, Department of Medicine and Care, Radio Physics. Linköping University, Department of Medicine and Care, Radiology. Linköping University, Faculty of Health Sciences.
    Kikinis, Ron
    Surgical Planning Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
    Knutsson, Hans
    Linköping University, Department of Biomedical Engineering. Linköping University, Faculty of Health Sciences.
    Three-dimensional adaptive filtering in magnetic resonance angiography2001In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 14, no 1, p. 63-71Article in journal (Refereed)
    Abstract [en]

    In order to enhance 3D image data from magnetic resonance angiography (MRA), a novel method based on the theory of multidimensional adaptive filtering has been developed. The purpose of the technique is to suppress image noise while enhancing important structures. The method is based on local structure estimation using six 3D orientation selective filters, followed by an adaptive filtering step controlled by the local structure information. The complete filtering procedure requires approximately 3 minutes of computational time on a standard workstation for a 256 × 256 × 64 data set. The method has been evaluated using a mathematical vessel model and in vivo MRA data (both phase contrast and time of flight (TOF)). 3D adaptive filtering results in a better delineation of small blood vessels and efficiently reduces the high-frequency noise. Depending on the data acquisition and the original data type, contrast-to-noise ratio (CNR) improvements of up to 179% (8.9 dB) were observed. 3D adaptive filtering may provide an alternative to prolonging the scan time or using contrast agents in MRA when the CNR is low.

  • 274.
    Wigström, Lars
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Ebbers, Tino
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
    Fyrenius, Anna
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Karlsson, Matts
    Linköping University, Department of Biomedical Engineering. Linköping University, Department of Mechanical Engineering. Linköping University, The Institute of Technology.
    Engvall, Jan
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Bolger, Ann F.
    Division of Biomedical Science, University of California at Riverside, Riverside, California.
    Particle trace visualization of intracardiac flow using time-resolved 3D phase contrast MRI1999In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 41, no 4, p. 793-799Article in journal (Refereed)
    Abstract [en]

    The flow patterns in the human heart are complex and difficult to visualize using conventional two-dimensional (2D) modalities, whether they depict a single velocity component (Doppler echocardiography) or all three components in a few slices (2D phase contrast MRI). To avoid these shortcomings, a temporally resolved 3D phase contrast technique was used to derive data describing the intracardiac velocity fields in normal volunteers. The MRI data were corrected for phase shifts caused by eddy currents and concomitant gradient fields, with improvement in the accuracy of subsequent flow visualizations. Pathlines describing the blood pathways through the heart were generated from the temporally resolved velocity data, starting from user-specified locations and time frames. Flow trajectories were displayed as 3D particle traces, with simultaneous demonstration of morphologic 2D slices. This type of visualization is intuitive and interactive and may extend our understanding of dynamic and previously unrecognized patterns of intracardiac flow.

  • 275.
    Wigström, Lars
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Fyrenius, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Karlsson, Matts
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation .
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Bolger, Ann F
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    The effects of maxwell terms on particle traces calculated from 3D cine phase contrast images1999In: Journal of Cardiovascular Magnetic Resonance,1999, 1999, p. 93-93Conference paper (Other academic)
  • 276.
    Wigström, Lars
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Lindström, Lena
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Sjöqvist, Lars
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Thuomas, K. Å.
    Linköping University, Department of Medicine and Care, Radiology. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    M-mode magnetic resonance imaging: a new modality for assessing cardiac function1995In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 15, no 4, p. 397-407Article in journal (Refereed)
    Abstract [en]

    Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.

  • 277.
    Wigström, Lars
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Sjöqvist, Lars
    Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Faculty of Health Sciences.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Temporally resolved 3D phase-contrast imaging1996In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 36, no 5, p. 800-803Article in journal (Refereed)
    Abstract [en]

    A conventional 3D phase contrast acquisition generates images with good spatial resolution, but often gives rise to artifacts due to pulsatile flow. 2D cine phase contrast, on the other hand, can register dynamic flow, but has a poor spatial resolution perpendicular to the imaging plane. A combination of both high spatial and temporal resolution may be advantageous in some cases, both in quantitative flow measurements and in MR angiography. The described 3D cine phase contrast pulse sequence creates a temporally resolved series of 3D data sets with velocity encoded data.

  • 278.
    Wijkman, Magnus
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology.
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lindström, Torbjörn
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Internal Medicine. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Östgren, Carl-Johan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Department of Health and Society, General Practice. Östergötlands Läns Landsting, Local Health Care Services in the West of Östergötland.
    Arterial stiffness in patients with type 2 diabetes correlates with both ambulatory and central blood pressure but not with glycemic control2007In: 17th meeting on Hypertension,2007, 2007Conference paper (Other academic)
  • 279.
    Wijkman, Magnus
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology.
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Lindström, Torbjörn
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Internal Medicine. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Östgren, Carl-Johan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Department of Health and Society, General Practice. Östergötlands Läns Landsting, Local Health Care Services in the West of Östergötland.
    Correlations between left ventricular mass and conventional, ambulatory and central blood pressure in patients with type 2 diabetes.2007In: 17th meeting on Hypertension,2007, 2007Conference paper (Other academic)
  • 280.
    Wilkenshoff, UM
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Hatle, Liv
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Sovany, A
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Sutherland, George R
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Cardiology. Östergötlands Läns Landsting, Heart Centre, Department of Cardiology.
    Age-dependent changes in regional diastolic function evaluated by color Doppler myocardial imaging: A comparison with pulsed Doppler indexes of global function.2001In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 14, no 10, p. 959-969Article in journal (Refereed)
    Abstract [en]

    The goals of this study were to evaluate possible normal age-related changes in regional myocardial relaxation as detected by color Doppler myocardial imaging (CDMI) velocities and to compare the extent of any such changes with age-induced changes in global diastolic function. In 80 healthy subjects (aged 21 to 72 years, equally subdivided by decades) the mitral flow velocities in early diastole (E) and atrial contraction (A) were recorded as were the velocities of left ventricular (W) motion of early (EDV) and late diastole (LDV) in the 16 standard LV segments, and their ratios were calculated. in healthy persons younger than 40 years, all segments showed an EDV/LDV ratio > 1, whereas in healthy persons aged 40 years or older the mean EDV of all segments decreased, and the mean LDV increased, resulting in a significant decrease of the mean EDV/LDV ratio with age. Values of EDV/LDV ratios were higher than E/A ratios (P < .0001), but their changes with age correlated well with each other (r = 0.805). With increasing age, an EDV/LDV ratio <1 was observed more often in basal segments (P < .001, compared with mid and apical segments) and less often in segments of anteroseptal and posterior walls viewed from the parasternal window. The presence of > 50% segments with an EDV/LDV ratio <1 was associated with an E/A ratio <1. Regional diastolic function indexes as evaluated by CDMI changed with increasing age in a heterogeneous way and influenced global diastolic function parameters.

  • 281.
    Wranne, Bengt
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Hök, B
    Inte så lätt att anvanda stetoskopet på rätt sätt. Auskultationens svåra konst bör ha stort utrymme i läkarutbildningen.1999In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 96, no 24, p. 2981-2984Article in journal (Refereed)
    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.

  • 282.
    Wranne, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Hök, Bertil
    Inte så lätt att använda stetoskopet på rätt sätt: Askulationens svåra konst bör ha stort utrymme i läkarutbildningen.1999In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 96, p. 2981-2984Article in journal (Other (popular science, discussion, etc.))
  • 283.
    Wranne, Bengt
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Analysis of different methods of assessing the stenotic mitral valve area with emphasis on the pressure gradient half-time concept.1990In: American Journal of Cardiology, ISSN 0002-9149, E-ISSN 1879-1913, Vol. 66, no 5, p. 614-620Article in journal (Refereed)
    Abstract [en]

    There are 2 different theoretical models that analyze factors influencing the transmitral pressure gradient half-time (T1/2), defined as the time needed for the pressure gradient to reach half its initial value. In this report the models and the assumptions inherent in them were summarized. One model includes left heart chamber compliance, the other does not. Although the models at a superficial glance seem to be contradictory, the conclusions drawn from them are similar: i.e., T1/2 is influenced not only by valve area, but also by initial maximal pressure gradient and by flow. Different clinical situations in which the T1/2 method for valve area estimation has been shown not to work are analyzed in the 2 models. It is concluded that these models have contributed to our understanding of the T1/2 concept and when it should not be used. We also advocate use of the continuity equation in these situations, since no assumptions then need be made.

  • 284.
    Wranne, Bengt
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Problems related to the assessment of fluid velocity and volume flow in valve regurgitation using ultrasound Doppler technique.1987In: European Heart Journal, ISSN 0195-668X, E-ISSN 1522-9645, Vol. 8 Suppl C, p. 29-33Article in journal (Refereed)
    Abstract [en]

    Understanding of the factors affecting regurgitant flow through a heart valve and of the inherent limitations of the Doppler technique is needed to interpret correctly the information obtained during an ultrasound Doppler examination. This paper describes the flow conditions at the leaking valve and limitations of the Doppler technique which become important in the case of valve regurgitation. The flow conditions can be described in the following terms: contraction of the flow, core flow dimensions, friction, and intrusion and width of the jet flow. Contraction occurs at the entrance to the orifice and causes the width of the jet at the orifice to be smaller than the orifice itself. This contraction should be taken into account when calculating volume flow. The jet reaches a minimal area at the vena contracta where the flow velocity is close to that expected from the Bernoulli equation. The area of the vena contracta relative to the area of the hole can vary between 0.6 and 1.0; the lowest value is seen at a sharp-edged orifice and the highest value, at a hole with an ideally rounded inlet. Friction has a marginal role on flow velocity at the vena contracta. The velocity at the vena contracta persists in a region called the core flow region. This region has a length of 4-8 hole diameters. The total jet intrusion and the width of the jet are related to both the flow velocity at the hole and the diameter of the hole.(ABSTRACT TRUNCATED AT 250 WORDS)

  • 285.
    Wranne, Bengt
    et al.
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Quantification of heart valve regurgitation: a critical analysis from a theoretical and experimental point of view.1985In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 5, no 1, p. 81-88Article in journal (Refereed)
    Abstract [en]

    A theoretical analysis is presented regarding factors of importance for the determination of distance of intrusion of the regurgitant jet in heart valve regurgitation. The analysis is based on hydrodynamic theory. In the idealized model situation, for a circular hole, the intrusion of the regurgitant jet is linearly related to the product of the fluid mean velocity in the orifice and the diameter of the orifice. This was also shown to be true in an experimental fluid model. Thus, volume regurgitation cannot be quantified by the measurement of distance of intrusion of the regurgitant jet alone. On the other hand, an estimate of volume regurgitation can, in the idealized situation, be obtained if mean fluid velocity in the orifice, distance of intrusion of the jet and regurgitation time are known.

  • 286.
    Wranne, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Wallentin, Ingemar
    Ekokardiografi - En oundgänglig metod i kardiovaskulär diagnostik2000In: Läkartidningen, ISSN 0023-7205, E-ISSN 1652-7518, Vol. 97, no 42, p. 4712-4720Article in journal (Other academic)
    Abstract [sv]

    [No abstract available]

  • 287. Wulff, John
    et al.
    Lönn, Urban
    Keck, Karl Yngve
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Peterzén, Bengt
    Casimir-Ahn, Henrik
    Flow characteristics of the Hemopump: an experimental in vitro study.1997In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 63, no 1, p. 162-166Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The Hemopump (DLP/Medtronic) has been in clinical use for about 7 years. There is still no adequate way of determining actual output from the three available pump systems in the clinical situation. If the pump is completely stopped during weaning from the device, there is a possibility of back-leakage through the pump, endangering the patient from regurgitation into the left ventricle. It can also make it more difficult to judge the recovery of heart function because of a volume load of the left ventricle. The aim of this study was to evaluate in a standardized, experimental in vitro model the output from three different-sized Hemopump catheters at various pressure levels and to quantify the back-flow through the pumps.

    METHODS: The Hemopump models were tested in an in vitro study regarding total outflow at various speeds at three pressure levels. The back-flow through the pumps was also measured with the pumps at a complete stop.

    RESULTS: The outflow from the Hemopumps ranged from 0.4 to 4.5 L/min, depending on which pump and speed were used. Variations in total output, depending on speed and various pressure settings, could be up to 0.4 L/min. Back-flow through the pump into the left ventricle may be as great as 1.6 L/min.

    CONCLUSIONS: The flow outputs from the different Hemopump models were reproducible over time and were closely related to the resistance of the model. The Hemopump, if not running, can induce substantial regurgitation through the pump into the left ventricle.

  • 288. Xiong, C
    et al.
    Hök, Bertil
    Strömberg, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation.
    Loyd, Dan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Applied Thermodynamics and Fluid Mechanics.
    Wranne, Bengt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Ask, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements.
    A bioacoustic method for timing of respiration at cardiac investigations1995In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 15, p. 151-157Article in journal (Refereed)
  • 289. Xiong, Changsheng
    et al.
    Sjöberg, Birgitta Janero
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Sveider, Per
    Linköping University, Department of Biomedical Engineering.
    Ask, Per
    Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wranne, Bengt
    Linköping University, Department of Medicine and Care, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Problems in timing of respiration with the nasal thermistor technique.1993In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 6, no 2, p. 210-216Article in journal (Refereed)
    Abstract [en]

    When one analyzes transvalvular and venous flow velocity patterns, it is important to relate them to respiration. For this reason a nasal thermistor technique is often used, although it is known that this signal is delayed in relation to intrathoracic pressure changes. The magnitude and variation in delay have not been investigated previously and were, therefore, studied in a model experiment in 10 normal subjects, in 10 patients with obstructive, and in 10 patients with restrictive pulmonary disease. Esophageal pressure variations measured with an air-filled balloon served as a gold standard for intrathoracic pressure changes. During basal conditions there was, for both patient groups and normal subjects, a considerable delay of the thermistor signal. The average delay for all subjects was 370 msec with a wide variation (from 120 to 720 msec). At higher breathing frequencies the delay shortened to 310 msec (P < 0.01) but there was still a wide variation (ranging from 200 to 470 msec). Theoretic calculations show that the delay caused by the respiratory system accounts for only a minor portion of the total delay. Model experiments confirmed that the response characteristics of the thermistor probes limit the accuracy in timing of respiration. The total delay with the investigated thermistor technique is too long and variable to fulfil clinical demands.

  • 290. Yang, P C
    et al.
    Santos, J M
    Nguyen, P K
    Scott, G C
    Engvall, Jan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    McConnell, M V
    Wright, G A
    Nishimura, D G
    Pauly, J M
    Hu, B S
    Dynamic Real-Time Architecture in Magnetic Resonance Coronary Angiography - A Prosepctive Clinical Trial2004In: Journal of Cardiovascular Magnetic Resonance, ISSN 1097-6647, E-ISSN 1532-429X, Vol. 6, p. 885-894Article in journal (Refereed)
  • 291.
    Zachrisson, Helene
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Carotisstenos, logistik. Vilka opereras och när.2007In: Svenska Neurologmötet,2007, 2007Conference paper (Other academic)
  • 292.
    Zachrisson, Helene
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    Duplexundersökning med måltidsprovokation vid bukangina2006In: Kardiovaskulära vårmöte,2006, 2006Conference paper (Other academic)
  • 293.
    Åstrand, Håkan
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Ryden Ahlgren, A
    Sandgren, T
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Väggstress i bukaorta hos människa - in vivo studier undersökt med ultraljud2004In: Svenska Läkaresällskapets Riksstämma,2004, 2004Conference paper (Other academic)
  • 294.
    Åstrand, Håkan
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology.
    Ryden Ahlgren, A
    Sundkvist, G
    Länne, Toste
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Thoracic and Vascular Surgery.
    Reduced aortic wall stress in diabetes mellitus - a contributor for the low incidence of abdominal aortic aneurysm2004In: 14th meeting on hypertension,2004, 2004Conference paper (Other academic)
3456 251 - 294 of 294
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