| 1. |
- Bjällmark, Anna, et al.
(författare)
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A system to quantify and visualize ventricular rotation pattern of the heart
- 2009
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Patent (populärvet., debatt m.m.)abstract
- Different modalities have been used to describe the rotational motion of the ventricles of the heart and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes and timings of rotation have been reported, whereas no method is available to fully describe the rotation pattern of the ventricles. The object of the present application is to achieve a system that presents a novel way to quantify and visualize the ventricular rotation pattern of the heart. We present a novel method that assesses and describes the rotation pattern by calculating the rotation axis of the ventricle. Non- invasive image acquisition is required to collect rotation values from different positions of the myocardium. Thereafter, a kinematic model of a ventricle is constructed to determine the rotation planes at different levels of the heart. The motion of the rotation planes are visualized by plotting the normal vectors of the planes over time, i.e. the rotation axis of the planes. This new method is different to all other methods used today for assessing cardiac function, as it does not describe the amplitude of a motion but the relationship in motion between different parts within a ventricle. Preliminary results indicate that the rotation axis is more sensitive to changes in the rotation pattern than conventional measurements of ventricular rotation. This new method could be used for early detection of cardiac diseases and for selection of patients for and optimization of cardiac resynchronization therapy.
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| 2. |
- Bjällmark, Anna, et al.
(författare)
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Differences in myocardial velocities during supine and upright exercise stress echocardiography in healthy adults
- 2009
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 29:3, s. 216-223
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Bjällmark, Anna, et al.
(författare)
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Velocity tracking - a novel method for quantitative analysis of longitudinal myocardial function
- 2007
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Ingår i: Journal of the American Society of Echocardiography. - : Elsevier. - 0894-7317 .- 1097-6795. ; 20:7, s. 847-856
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Tidskriftsartikel (refereegranskat)abstract
- Doppler tissue imaging is a method for quantitative analysis of longitudinal myocardial velocity. Commercially available ultrasound systems can only present velocity information using a color Dopplerbased overlapping continuous color scale. The analysis is time-consuming and does not allow for simultaneous analysis in different projections. We have developed a new method, velocity tracking, using a stepwise color coding of the regional longitudinal myocardial velocity. The velocity data from 3 apical projections are presented as static and dynamic bull's-eye plots to give a 3-dimensional understanding of the function of the left ventricle. The static bull's-eye plot can display peak systolic velocity, late diastofic tissue velocity, or the sum of peak systolic velocity and early diastolic tissue velocity. Conversely, the dynamic bull's-eye plot displays how the myocardial velocities change over one heart cycle. Velocity tracking allows for a fast, simple, and hituitive visual analysis of the regional longitudinal contraction pattern of the left ventricle with a great potential to identify characteristic pathologic patterns.
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| 4. |
- Brodin, Lars-Åke, et al.
(författare)
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Global and local detection of blood vessel elasticity
- 2006
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Patent (populärvet., debatt m.m.)abstract
- The present invention is a non-invasive analysis system for detection of global and local blood vessel elasticity. The analysis system comprises two subsystems where subsystem 1 is data collecting unit and subsystem 2 is an analysis unit. The data collecting unit comprises one or many non-invasive image generating systems, or the data collecting system makes the registration possible of movement parameters that quantifies the dynamics of the blood vessel wall in longitudinal and radial directions. Subsystem 2 performs Wave Intensity Analysis which is an analysis method using co-related parts of the circulation system by measuring the intensity change (dl) of the blood vessel during a heart cycle. The intensity change is calculated as the product of the pressure derivate and the flow velocity derivate. In subsystem 2 the changes of pressure and flow are approximated by the deformation velocity or velocity of the radial and longitudinal direction, respectively. By calculating time constants and amplitudes of the intensity change graph a measure is obtained of the local and global elasticity of the blood vessel and atherosclerotic constrictions of arterial vessels may then be identified at an early stage.
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| 5. |
- Falkmer, Torbjörn, et al.
(författare)
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Fixation identification in centroid versus start-point modes using eye-tracking data
- 2008
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Ingår i: Perceptual and Motor Skills. - : Sage Publications. - 0031-5125 .- 1558-688X. ; 106:3, s. 710-724
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Tidskriftsartikel (refereegranskat)abstract
- Fixation-identification algorithms, needed for analyses of eye movements, may typically be separated into three categories, viz. (i) velocity-based algorithms, (ii) area-based algorithms, and (iii) dispersion-based algorithms. Dispersion-based algorithms are commonly used but this application introduces some difficulties, one being optimization. Basically, there are two modes to reach this goal of optimization, viz., the start-point mode and the centroid mode. The aim of the present study was to compare and evaluate these two dispersion-based algorithms. Manual inspections were made of 1,400 fixations in each mode. Odds ratios showed that by using the centroid mode for fixation detection, a valid fixation is 2.86 times more likely to be identified than by using the start-point mode. Moreover, the algorithm based on centroid mode dispersion showed a good interpretation speed, accuracy, robustness, and ease of implementation, as well as adequate parameter settings.
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| 6. |
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| 7. |
- Johnell, Matilda, et al.
(författare)
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The influence of different heparin surface concentrations and antithrombin-binding capacity on inflammation and coagulation
- 2005
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 26:14, s. 1731-1739
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The corline heparin surface (CHS) used in the extracorporeal circuit during coronary artery bypass grafting is shown to decrease the activation of inflammation and coagulation. Synchrotron radiation studies have shown that a single layer of the CHS may not completely cover the substrate surface. However, a double layer of CHS results in a uniform surface. We investigated the effect of surfaces with different surface concentrations of heparin on cell activation and coagulation compared to an uncoated surface. The CHS is prepared by a conditioning layer of polymeric amine onto which a macromolecular heparin conjugate is attached. We used PVC tubing, uncoated or modified with a single or double layer of the CHS, and circulated fresh whole blood from healthy volunteers in a loop model system at 37 degrees C up to 4 h. Blood was drawn from the loops at different times and activation of inflammation and coagulation was studied by real-time PCR, flow cytometry and ELISA. The activation of leukocytes and platelets and formation of leukocyte-platelet aggregates were reduced by use of the single-layered CHS compared to the uncoated surface. Use of double-layered CHS resulted in significantly reduced cell activation and thrombin generation. Development of the CHS obtained by the double layer of the coating has improved the biocompatibility of the surface.
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| 8. |
- Larsson, Matilda, 1981-
(författare)
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Quantification and Visualization of Cardiovascular Function using Ultrasound
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is a large need for accurate methods detecting cardiovascular diseases, since they are one of the leading causes of mortality in the world, accounting for 29.3% of all deaths. Due to the complexity of the cardiovascular system, it is very challenging to develop methods for quantification of its function in order to diagnose, prevent and treat cardiovascular diseases. Ultrasound is a technique allowing for inexpensive, noninvasive imaging, but requires an experienced echocardiographer. Nowadays, methods like Tissue Doppler imaging (TDI) and Speckle tracking imaging (STI), measuring motion and deformation in the myocardium and the vessel walls, are getting more common in routine clinical practice, but without a proper visualization of the data provided by these methods, they are time-consuming and difficult to interpret. Thus, the general aim of this thesis was to develop novel ultrasound-based methods for accurate quantification and easily interpretable visualization of cardiovascular function. Five methods based on TDI and STI were developed in the present studies. The first study comprised development of a method for generation of bull’s-eye plots providing a color-coded two-dimensional visualization of myocardial longitudinal velocities. The second study proposed the state diagram of the heart as a new circular visualization tool for cardiac mechanics, including segmental color-coding of cardiac time intervals. The third study included development of a method describing the rotation pattern of the left ventricle by calculating rotation axes at different levels of the left ventricle throughout the cardiac cycle. In the fourth study, deformation data from the artery wall were tested as input to wave intensity analysis providing information of the ventricular – arterial interaction. The fifth study included an in-silico feasibility study to test the assessment of both radial and longitudinal strain in a kinematic model of the carotid artery. The studies showed promising results indicating that the methods have potential for the detection of different cardiovascular diseases and are feasible for use in the clinical setting. However, further development of the methods and both quantitative comparison of user dependency, accuracy and ease of use with other established methods evaluating cardiovascular function, as well as additional testing of the clinical potential in larger study populations, are needed.
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| 9. |
- Larsson, Matilda, 1981-, et al.
(författare)
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State diagrams of the heart - a new approach to describing cardiac mechanics
- 2009
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Ingår i: Cardiovascular Ultrasound. - : BMC. - 1476-7120. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Larsson, Matilda, 1981-, et al.
(författare)
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Ultrasound-based 2D Strain Estimation of the Carotid Artery : an in-silico feasibility study
- 2009
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Ingår i: Ultrasonics Symposium (IUS), 2009 IEEE International. - : IEEE. - 9781424443895 ; , s. 5441992-
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Konferensbidrag (refereegranskat)abstract
- Ultrasound based estimation of arterial wall properties is commonly used to assess vessel wall stiffness in studies of vascular diseases. Recently, it was shown that the longitudinal motion of the vessel during systole can be measured using speckle tracking. However, the assessment of longitudinal strain in the vessel wall has to be further investigated. The aim of this study was to test the feasibility of simultaneous assessment of radial and longitudinal strain in the carotid artery using computer simulations. A kinematic cylindrical model of the carotid artery with realistic dimensions was constructed. The model was deformed radially according to temporal distention measured in-vivo while longitudinal deformation was the result of conservation of volume. Moreover, longitudinal motion was superimposed based on profiles obtained in-vivo. Ultrasound long axis images were simulated using a generalized convolution model (COLE) with realistic image properties. Four models with different scatterer distributions were built. For each of them, longitudinal and radial motion were estimated using normalized cross-correlation with spline interpolation to detect sub-sample motion. Radial and longitudinal strains, obtained by linear regression were compared with the ground truth from the model. The maximal systolic radial strain was estimated to be -12.77 ± 0.4% (ground truth -13.89%) while longitudinal strain was 5.21 ± 0.67% (ground truth 5.3%). This study shows the feasibility of simultaneously measuring radial and longitudinal strain in the carotid artery by making use of currently available hardware.
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| 11. |
- Larsson, Matilda, et al.
(författare)
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Wave intensity wall analysis: a novel noninvasive method to measure wave inntensity
- 2009
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Ingår i: Heart and Vessels. - : Springer Science and Business Media LLC. - 0910-8327 .- 1615-2573. ; 24, s. 357-365
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Tidskriftsartikel (refereegranskat)abstract
- Wave intensity analysis is a concept providing information about the interaction of the heart and the vascular system. Originally, the technique was invasive. Since then new noninvasive methods have been developed. A recently developed ultrasound technique to estimate tissue motion and deformation is speckle-tracking echocardiography. Speckle tracking-based techniques allow for accurate measurement of movement and deformation variables in the arterial wall in both the radial and the longitudinal direction. The aim of this study was to test if speckle tracking-derived deformation data could be used as input for wave intensity calculations. The new concept was to approximate changes of flow and pressure by deformation changes of the arterial wall in longitudinal and radial directions. Flow changes (dU/dt) were approximated by strain rate (sr, 1/s) of the arterial wall in the longitudinal direction, whereas pressure changes (dP/dt) were approximated by sign reversed strain rate (1/s) in the arterial wall in the radial direction. To validate the new concept, a comparison between the newly developed Wave Intensity Wall Analysis (WIWA) algorithm and a commonly used and validated wave intensity system (SSD-5500, Aloka, Tokyo, Japan) was performed. The studied population consisted of ten healthy individuals (three women, seven men) and ten patients (all men) with coronary artery disease. The present validation study indicates that the mechanical properties of the arterial wall, as measured by a speckle tracking-based technique are a possible input for wave intensity calculations. The study demonstrates good visual agreement between the two systems and the time interval between the two positive peaks (W1-W2) measured by the Aloka system and the WIWA system correlated for the total group (r = 0.595, P < 0.001). The correlation for the diseased subgroup was r = 0.797, P < 0.001 and for the healthy subgroup no significant correlation was found (P > 0.05). The results of the study indicate that the mechanical properties of the arterial wall could be used as input for wave intensity calculations. The WIWA concept is a promising new method that potentially provides several advantages over earlier wave intensity methods, but it still has limitations and needs further refinement and larger studies to find the optimal clinical use.
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| 12. |
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| 13. |
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| 14. |
- Westholm, Carl, et al.
(författare)
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Velocity tracking, a new and user independent method for detecting regional function of the left ventricle
- 2009
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 29:1, s. 24-31
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Tidskriftsartikel (refereegranskat)abstract
- The use of two-dimensional echocardiography (2D echo) for detection of ischaemia is limited due to high user dependency. Longitudinal motion is sensitive for ischaemia and usable for quantitative measurement of longitudinal myocardial function but time consuming. Velocity tracking (VeT) is a new method that gives an easy three-dimensional understanding of both systolic and diastolic regional motion, using colour coded bull's eye presentation of longitudinal velocity, derived from colour coded tissue Doppler. The aim of this study was to test the accuracy of VeT in detecting ischaemia in non-ST-segment elevation myocardial infarction (NSTEMI) patients bedside. Twenty patients with NSTEMI and 10 controls were included. Echocardiography was performed within 24 h of symptoms and prior to coronary angiography. Bull's eye plots presenting the peak systolic velocity (PSV) and the sum of PSV and the E-wave-velocity (PSV+E) were created using our developed software. VeT was compared to expert wall motion scoring (WMS) and bedside echo. We used the clinical conclusion based on ECG, angiography and clinical picture as 'gold standard'. Sensitivity for ischaemia with VeT (PSV+E) was 85% and specificity 60%. The corresponding sensitivities for expert WMS were 75% (specificity 40%). For regional analysis VeT and WMS showed comparable results with correct regional outcome in 11/20 of patients both superior to bedside echo. Velocity tracking is a promising technique that provides an easily understandable three-dimensional bull's eye plot for assessment of regional left ventricular longitudinal velocity with great potential for detection of regional dysfunction and myocardial ischaemia.
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