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  • 1. Beyene, Ayne A.
    et al.
    Welemariam, Tewelle
    Persson, Marie
    Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik.
    Lavesson, Niklas
    Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik.
    Improved concept drift handling in surgery prediction and other applications2015In: Knowledge and Information Systems, ISSN 0219-1377, E-ISSN 0219-3116, Vol. 44, no 1, p. 177-196Article in journal (Refereed)
    Abstract [en]

    The article presents a new algorithm for handling concept drift: the Trigger-based Ensemble (TBE) is designed to handle concept drift in surgery prediction but it is shown to perform well for other classification problems as well. At the primary care, queries about the need for surgical treatment are referred to a surgeon specialist. At the secondary care, referrals are reviewed by a team of specialists. The possible outcomes of this review are that the referral: (i) is canceled, (ii) needs to be complemented, or (iii) is predicted to lead to surgery. In the third case, the referred patient is scheduled for an appointment with a surgeon specialist. This article focuses on the binary prediction of case three (surgery prediction). The guidelines for the referral and the review of the referral are changed due to, e.g., scientific developments and clinical practices. Existing decision support is based on the expert systems approach, which usually requires manual updates when changes in clinical practice occur. In order to automatically revise decision rules, the occurrence of concept drift (CD) must be detected and handled. The existing CD handling techniques are often specialized; it is challenging to develop a more generic technique that performs well regardless of CD type. Experiments are conducted to measure the impact of CD on prediction performance and to reduce CD impact. The experiments evaluate and compare TBE to three existing CD handling methods (AWE, Active Classifier, and Learn++) on one real-world dataset and one artificial dataset. TBA significantly outperforms the other algorithms on both datasets but is less accurate on noisy synthetic variations of the real-world dataset.

  • 2.
    Bjällmark, Anna
    et al.
    KTH, Huddinge, Sweden.
    Larsson, M.
    KTH, Huddinge, Sweden.
    Lundback, S.
    Inovacor AB, Vaxholm, Sweden.
    Johnsson, J.
    GrippingHeart AB, Stockholm, Sweden.
    Winter, R.
    Karolinska University Hospital, Huddinge, Sweden.
    Brodin, L.-A.
    Karolinska University Hospital, Huddinge, Sweden.
    A new graphical user interface module generating state diagrams of the heart2006In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 7, no suppl_1, p. S46-Article in journal (Refereed)
  • 3.
    Bjällmark, Anna
    et al.
    KTH, Medicinsk teknik.
    Larsson, Matilda
    KTH, Medicinsk teknik.
    Brodin, Lars-Åke
    KTH, Medicinsk teknik.
    Nowak, Jacek
    Lind, Britta
    KTH, Medicinsk teknik.
    Hayashi, Shirley
    Mazza do Nascimento, Marcelo
    Riella, Miquel
    Seeberger, Astrid
    Effects of hemodialysis on the cardiovascular system: Quantitative analysis using wave intensity wall analysis and tissue velocity imaging2010In: Heart and Vessels, ISSN 0910-8327, E-ISSN 1615-2573Article in journal (Refereed)
    Abstract [en]

    Cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD). The aim of this study was to investigate the changes in cardiovascular function induced by a single session of hemodialysis (HD) by the analysis of cardiovascular dynamics using wave intensity wall analysis (WIWA) and of systolic and diastolic myocardial function using tissue velocity imaging (TVI). Grey-scale cine loops of the left common carotid artery, conventional echocardiography and TVI images of the left ventricle were acquired before and after HD in 45 patients (17 women, mean age 54) with ESRD. The WIWA indexes, W1 preload-adjusted W1, W2 and preload-adjusted W2, and the TVI variables, isovolumic contraction velocity (IVCV), isovolumic contraction time (IVCT), peak systolic velocity (PSV), displacement, isovolumic relaxation velocity (IVRV), isovolumic relaxation time (IVRT), peak early diastolic velocity (E’) and peak late diastolic velocity (A’), were compared before and after HD. The WIWA measurements showed significant increases in W1 (p < 0.05) and preload-adjusted W1 (p < 0.01) after HD. W2 was significantly decreased (p < 0.05) after HD, whereas the change in preload-adjusted W2 was not significant. Systolic velocities, IVCV (p < 0.001) and PSV (p < 0.01), were increased after HD, whereas the AV-plane displacement were decreased (p < 0.01). For the measured diastolic variables, E’ was significantly decreased (p < 0.01) and IVRT was significantly prolonged (p < 0.05), after HD. A few correlations were found between WIWA and TVI variables. The WIWA and TVI measurements indicate that a single session of HD improves systolic function. The load dependency of the diastolic variables seems to be more pronounced than for the systolic variables. Preload-adjusted wave intensity indexes may contribute in the assessment of true LV contractility and relaxation.

  • 4.
    Bjällmark, Anna
    et al.
    KTH, Medicinsk teknik.
    Larsson, Matilda
    KTH, Medicinsk teknik.
    Shahgaldi, Kambiz
    Lind, Britta
    KTH, Skolan för teknik och hälsa (STH).
    Winter, Reidar
    Brodin, Lars-Ake
    KTH, Medicinsk teknik.
    Differences in myocardial velocities during supine and upright exercise stress echocardiography in healthy adults2009In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 29, no 3, p. 216-223Article in journal (Refereed)
    Abstract [en]

    Tissue Velocity Imaging (TVI) is a method for quantitative analysis of longitudinal myocardial velocities, which can be used during exercise and pharmacological stress echocardiography. It is of interest to evaluate cardiac response to different types of stress tests and the differences between upright and supine bicycle exercise tests have not been fully investigated. Therefore, the aim of this study was to compare cardiac response during supine and upright exercise stress tests. Twenty young healthy individuals underwent supine and upright stress test. The initial workload was set to 30 W and was increased every minute by a further 30 W until physical exhaustion. Tissue Doppler data from the left ventricle were acquired at the end of every workload level using a GE Vivid7 Dimension system (> 200 frames s(-1)). In the off-line processing, isovolumic contraction velocity (IVCV), peak systolic velocity (PSV), isovolumic relaxation velocity (IVRV), peak early diastolic velocity (E') and peak late diastolic velocity (A') were identified at every workload level. No significant difference between the tests was found in PSV. On the contrary, E' was shown to be significantly higher (P < 0.001) during supine exercise than during upright exercise and IVRV was significantly lower (P < 0.001) during supine exercise compared to upright exercise. Upright and supine exercise stress echocardiography give a comparable increase in measured systolic velocities and significant differences in early diastolic velocities.

  • 5.
    Bjällmark, Anna
    et al.
    KTH, Medicinsk teknik.
    Lind, Britta
    KTH, Medicinsk teknik.
    Brodin, Lars-Åke
    KTH, Medicinsk teknik.
    Peolsson, Michael
    KTH, Skolan för teknik och hälsa (STH).
    Shahgaldi, Kambiz
    KTH, Medicinsk teknik.
    Nowak, Jacek
    Ultrasonographic strain imaging is superior to conventional non-invasive measures of vascular stiffness in the detection of age-dependent differences in the mechanical properties of the common carotid artery2010In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 11, no 7, p. 630-636Article in journal (Refereed)
    Abstract [en]

    Aims: Elastic properties of large arteries have been shown to deteriorate with age and in the presence of atherosclerotic vascular disease. In this study, the performance of ultrasonographic strain measurements was compared to conventional measures of vascular stiffness in the detection of age-dependent differences in the elastic properties of the common carotid artery.

    Methods and results: In 10 younger (25-28 years, 4 women) and 10 older (50-59 years, 4 women) healthy individuals, global and regional circumferential and radial strain variables were measured in the short-axis view of the right common carotid artery using ultrasonographic two-dimensional (2D) strain imaging with recently introduced speckle tracking technique. Conventional elasticity variables, elastic modulus (Ep) and β stiffness index, were calculated using M-mode sonography and non-invasive blood pressure measurements. Global and regional circumferential systolic strain and strain rate values were significantly higher (p < 0.001, p < 0.01 for regional late systolic strain rate) in the younger individuals, whereas the values of conventional elasticity variables in the same group were lower (p < 0.05). Among all strain and conventional elasticity variables, principal component analysis and its regression extension identified only circumferential systolic strain variables as contributing significantly to the observed discrimination between the younger and older age groups.

    Conclusion: Ultrasonographic 2D-strain imaging is a sensitive method for the assessment of elastic properties in the common carotid artery, being in this respect superior to conventional measures of vascular elasticity. The method has potential to become a valuable non-invasive tool in the detection of early atherosclerotic vascular changes.

  • 6.
    Fagerlind, Anna
    Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Spruttransporten2010Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 7.
    Filipsson, Emma
    et al.
    Jönköping University, School of Health and Welfare, HHJ, Dep. of Natural Science and Biomedicine.
    Olsson, Cecilia
    Jönköping University, School of Health and Welfare, HHJ, Dep. of Natural Science and Biomedicine.
    Interobserver variability when measuring the abdominal aorta with ultrasound: A comparison using the longitudinal and transverse axes2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A rupturing abdominal aortic aneurysm (AAA) has a mortality rate of 50% while an elective repair has a mortality rate of 3-8%. Screening programmes with ultrasound are used in some countries to detect AAA at an early stage. Ultrasound is however very observer bias and dependent on the observer's experience. The study was performed in Vietnam, a country that have experienced exceptional economic growth with increasing risk factors for cardiovascular diseases but has no national screening programme. The aim of this study was to examine the interobserver variability when measuring the abdominal aorta with ultrasound on young adults in Vietnam. The abdominal aorta was measured in the longitudinal and the transverse axis by two different observers using the leading edge to leading edge method. Participants in this study were 31 voluntary students, 16 men and 15 women in the ages 18-26 years, from the Da Nang university of medical technology and pharmacy and the design was a cross-sectional study with a quantitative approach. The study showed a significant difference between the longitudinal measurements but not between the transverse measurements. Despite this statistical significance, the observers' differences were within the recommended limit of 5 mm.

  • 8.
    Larsson, Matilda
    et al.
    School for Technology and Health, Royal Institute of Technology, Sweden.
    Bjällmark, Anna
    School for Technology and Health, Royal Institute of Technology, Sweden.
    Johnson, Jens
    School for Technology and Health, Royal Institute of Technology, Sweden.
    Winter, Reidar
    Department of Clinical Physiology, Karolinska University Hospital, Sweden.
    Brodin, Lars-Åke
    School for Technology and Health, Royal Institute of Technology, Sweden.
    Lundbäck, Stig
    Gripping Heart AB, KTH Business Lab, Sweden.
    State diagrams of the heart – a new approach to describing cardiac mechanics2009In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 7, no 22Article in journal (Refereed)
    Abstract [en]

    Background: Cardiac time intervals have been described as a measure of cardiac performance, where prolongation, shortening and delay of the different time intervals have been evaluated as markers of cardiac dysfunction. A relatively recently developed method with improved ability to measure cardiac events is Tissue Doppler Imaging (TDI), allowing accurate measurement of myocardial movements.

    Methods: We propose the state diagram of the heart as a new visualization tool for cardiac time intervals, presenting comparative, normalized data of systolic and diastolic performance, providing a more complete overview of cardiac function. This study aimed to test the feasibility of the state diagram method by presenting examples demonstrating its potential use in the clinical setting and by performing a clinical study, which included a comparison of the state diagram method with established echocardiography methods (E/E' ratio, LVEF and WMSI). The population in the clinical study consisted of seven patients with non ST-elevation myocardial infarction (NSTEMI) and seven control subjects, individually matched according to age and gender. The state diagram of the heart was generated from TDI curves from seven positions in the myocardium, visualizing the inter- and intraventricular function of the heart by displaying the cardiac phases.

    Results: The clinical examples demonstrated that the state diagram allows for an intuitive visualization of pathological patterns as ischemia and dyssynchrony. Further, significant differences in percentage duration between the control group and the NSTEMI group were found in eight of the totally twenty phases (10 phases for each ventricle), e.g. in the transition phases (Pre-Ejection and Post-Ejection). These phases were significantly longer (> 2.18%) for the NSTEMI group than for the control group (p < 0.05). No significant differences between the groups were found for the established echocardiography methods.

    Conclusion: The test results clearly indicate that the state diagram has potential to be an efficient tool for visualization of cardiac dysfunction and for detection of NSTEMI.

  • 9.
    Mårtensson, Mattias
    et al.
    KTH, Medicinsk bildteknik.
    Bjällmark, Anna
    KTH, Medicinsk teknik.
    Brodin, Lars-Åke
    KTH, Medicinsk teknik.
    Evaluation of tissue Doppler-based velocity and deformation imaging: a phantom study of ultrasound systems.2011In: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 12, no 6, p. 467-476Article in journal (Refereed)
    Abstract [en]

    AIMS: The objective of this study was to test the accuracy and diagnostic interchangeability of tissue Doppler-based displacement, velocity, strain, and strain rate measurements in commercially used ultrasound (US) systems. METHODS AND RESULTS: Using an in-house made phantom, four different US scanner models were evaluated. Two different scanners of the same model were tested, and one scanner acquisition was tested twice with two generations of the same workstation giving six test results in total. The scanners were in active clinical use and are subject to regular maintenance checks. There were three displacement and four velocity results that stood out from the rest and could be regarded as accurate and interchangeable. Among the deformation measurements, three acceptable strain results were found while there were no acceptable strain rate results. Furthermore, the study showed that measurements from scanners of the same model, same acquisition post-processed on different workstations and repeated measurements from the same scanner, can yield disparate results. CONCLUSION: Measurements that are accurate and of interchangeable use can be found for displacement and velocity measurements, but are less likely to be found for strain and strain rate measurements. It is strongly recommended that the ability of each individual US scanner to measure displacement, velocity, strain, and strain rate is evaluated before it is introduced into clinical practice, and it must always be evaluated together with the workstation the scanner is intended to be used in conjunction with.

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