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Quantification and Visualization of Cardiovascular Function using Ultrasound
KTH, School of Technology and Health (STH), Medical Engineering.ORCID iD: 0000-0002-5795-9867
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , x, 72 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2009:6
Keyword [en]
Ultrasound, Tissue Doppler imaging, Speckle tracking imaging, cardiovascular function, visualization, quantification
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:kth:diva-11762ISBN: 978-91-7415-524-2 (print)OAI: oai:DiVA.org:kth-11762DiVA: diva2:280838
Public defence
2010-01-22, 3-221, Alfred Nobels Alle 10, Huddinge, 08:30 (Swedish)
Opponent
Supervisors
Note
QC 20100727Available from: 2009-12-14 Created: 2009-12-11 Last updated: 2010-10-04Bibliographically approved
List of papers
1. Velocity tracking - a novel method for quantitative analysis of longitudinal myocardial function
Open this publication in new window or tab >>Velocity tracking - a novel method for quantitative analysis of longitudinal myocardial function
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2007 (English)In: Journal of the American Society of Echocardiography, ISSN 0894-7317, E-ISSN 1097-6795, Vol. 20, no 7, 847-856 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2007
Keyword
coronary-artery-disease; tissue doppler; stress echocardiography; diastolic dysfunction; heart-failure; diagnosis; motion; wall
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-11756 (URN)10.1016/j.echo.2006.11.024 (DOI)000248738600008 ()2-s2.0-34347386268 (Scopus ID)
Note

QC 20100727

QC 20151223

Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2017-12-12Bibliographically approved
2.
The record could not be found. The reason may be that the record is no longer available or you may have typed in a wrong id in the address field.
3. The rotation axis of the left ventricle - A new concept derived from ultrasound data in healthy individuals
Open this publication in new window or tab >>The rotation axis of the left ventricle - A new concept derived from ultrasound data in healthy individuals
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Abstract [en]

Different modalities have been used to describe the circumferential motion of the left ventricle (LV) and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes of rotation have been reported, whereas the rotation pattern of the LV has not been fully described. However, data from a previous study on regional rotation have indicated that the axis around which the LV rotates, is not congruent to the longitudinal axis of the LV. The aim of the present study was to develop an ultrasound-based method to calculate the rotation axis of the LV in a three-dimensional aspect throughout the cardiac cycle and to apply it in a group of healthy individuals. An algorithm for calculation of rotation axes at the basal, mid-, apical and transitional levels of the LV was developed. By constructing a simplified model of the LV, based on rotation amplitudes measured at the basal, mid- and apical levels, rotation planes with similar values of rotation could be calculated at each level. The transition plane was defined as where the rotation values shifted from positive to negative. An overview of the rotation pattern was achieved by displaying data on deflection (angle between the rotation axis and the longitudinal axis of the LV) and direction (defined as the angle in a short-axis view of the LV with zero degrees at the lateral wall and increasing angles counterclockwise) of the rotation axes throughout the cardiac cycle. The deflection differed significantly from zero in all tested time points, i.e. the rotation axis was not congruent to the longitudinal axis of the LV. Rayleigh’s test for uniformity demonstrated a significant mean direction for each of the axes for the majority of the tested time points. Thus, the axis of rotation at different levels of the LV displayed a physiological pattern, where also stability of rotation could be assessed. Furthermore, the angle and level of the transition plane could be described over time. This new way of assessing rotational function provides further insight into the complexity of LV mechanics. The method has acceptable reproducibility but the potential clinical use of this method needs to be validated in further studies.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-11749 (URN)
Note
QC 2010727Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2010-10-04Bibliographically approved
4. Wave intensity wall analysis: a novel noninvasive method to measure wave inntensity
Open this publication in new window or tab >>Wave intensity wall analysis: a novel noninvasive method to measure wave inntensity
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2009 (English)In: Heart and Vessels, ISSN 0910-8327, E-ISSN 1615-2573, Vol. 24, 357-365 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Wave intensity; Ultrasound; Speckle tracking; Arterial stiffness
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:kth:diva-11743 (URN)10.1007/s00380-008-1112-3 (DOI)000270225400007 ()19784819 (PubMedID)2-s2.0-70349641505 (Scopus ID)
Note

QC 20100624

Available from: 2009-12-14 Created: 2009-12-11 Last updated: 2017-12-12Bibliographically approved
5. Ultrasound-based 2D Strain Estimation of the Carotid Artery: an in-silico feasibility study
Open this publication in new window or tab >>Ultrasound-based 2D Strain Estimation of the Carotid Artery: an in-silico feasibility study
2009 (English)In: Ultrasonics Symposium (IUS), 2009 IEEE International, IEEE , 2009, , 4 p.5441992- p.Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
IEEE, 2009. 4 p.
Series
Proceedings of the IEEE Ultrasonics Symposium, ISSN 1051-0117 ; 2009
Keyword
Carotid artery, Strain imaging, Ultrasound
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-11759 (URN)10.1109/ULTSYM.2009.5441992 (DOI)2-s2.0-77952790716 (Scopus ID)978-142444389-5 (ISBN)
Conference
2009 IEEE International Ultrasonics Symposium, IUS 2009; Rome; 20 September 2009 through 23 September 2009
Note
QC 20100727Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2012-01-13Bibliographically approved

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