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Assessment of Myocardial Function using Phase Based Motion Sensitive MRI
Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Clinical Physiology . Linköping University, Faculty of Health Sciences.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quantitative assessment of myocardial function is a valuable tool for clinical applications and physiological studies. This assessment can be acquired using phase based motion sensitive magnetic resonance imaging (MRI) techniques. In this thesis, the accuracy of these phase based motion sensitive MRI techniques is investigated, and modifications in acquisition and post-processing are proposed.

The strain rate of the myocardium can be used to evaluate the myocardial function. However, the estimation of strain rate from the velocity data acquired with phase-contrast MRI (PC-MRI) is sensitive to noise. Estimation using normalized convolution showed, however, to reduce this sensitivity to noise and to minimize the influence of non-myocardial tissue which could impair the result.

Strain of the myocardium is another measure to assess myocardial function. Strain can be estimated from the myocardial displacement acquired with displacement encoding with stimulated echo (DENSE). DENSE acquisition can be realized with several different encoding strategies. The choice of encoding scheme may make the acquisition more or less sensitive to different sources of error. Two potential sources of errors in DENSE acquisition are the influence of the FID and of  the off-resonance effects. Their influence on DENSE were investigated to determine suitable encoding strategies to reduce their influence and thereby improve the measurement accuracy acquired.

The quality of the DENSE measurement is not only dependent on the accuracy, but also the precision of the measurement. The precision is affected by the SNR and thereby depends on flip angle strategies, magnetic field strength and spatial variation of the receiver coil sensitivity. A mutual comparison of their influence on SNR in DENSE was therefore performed and could serve as a guideline to optimize parameters for specific applications.

The acquisition time is often an important factor, especially in clinical applications where it affects potential patient discomfort and patient through-put. A multiple-slice DENSE acquisition was therefore presented, which allows the acquisition of strain values according to the 16-segment cardiac model within a single breath-hold, instead of the conventional three breath-holds.

The DENSE technique can also be adapted toward comprehensive evaluation of the heart in the form of full three-dimensional three-directional acquisition of the displacement. To estimate the full strain tensor from these data, a novel post-processing technique using a polynomial was investigated. The method yielded accurate results on an analytical model and \textit{in-vivo} strains obtained agreed with previously reported myocardial strains in normal volunteers.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2010. , 53 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1341
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-60027ISBN: 978-91-7393-302-5 (print)OAI: oai:DiVA.org:liu-60027DiVA: diva2:359503
Public defence
2010-11-12, Conrad, Universitetssjukhuset, Campus US, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2010-11-16 Created: 2010-10-04 Last updated: 2016-03-14Bibliographically approved
List of papers
1. Improved estimation and visualization of two-dimensional myocardial strain rate using MR velocity mapping
Open this publication in new window or tab >>Improved estimation and visualization of two-dimensional myocardial strain rate using MR velocity mapping
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2008 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 28, no 3, 604-611 p.Article in journal (Refereed) Published
Abstract [en]

Purpose: To estimate regional myocardial strain rate, with reduced sensitivity to noise and velocities outside the region of interest, and provide a visualization of the spatial variation of the obtained tensor field within the myocardium. Materials and Methods: Myocardial velocities were measured using two-dimensional phase contrast velocity mapping. Velocity gradients were estimated using normalized convolution and the calculated 2D strain rate tensor field was visualized using a glyph representation. Validation utilized a numerical phantom with known strain rate distribution. Strain rate glyph visualizations were created for normal myocardium in both systole and diastole and compared to a patient with an anteroseptal infarction. Results: In the phantom study the strain rate calculated with normalized convolution showed a very good agreement with the analytic solution, while traditional methods for gradient estimation were shown to be sensitive to both noise and surrounding velocity data. Normal myocardium showed a homogenous strain rate distribution, while a heterogeneous strain rate can be clearly seen in the patient data. Conclusion: The proposed approach for quantification and visualization of the regional myocardial strain rate can provide an objective measure of regional myocardial contraction and relaxation that may be valuable for the assessment of myocardial heart disease. © 2008 Wiley-Liss, Inc.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-43136 (URN)10.1002/jmri.21471 (DOI)000259106900007 ()71981 (Local ID)71981 (Archive number)71981 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
2. Influence of the FID and off-resonance effects in dense MRI
Open this publication in new window or tab >>Influence of the FID and off-resonance effects in dense MRI
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2011 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 65, no 4, 1104-1112 p.Article in journal (Refereed) Published
Abstract [en]

Accurate functional measurement in cardiovascular diseases is important as inaccuracy may compromise diagnostic decisions. Cardiac function can be assessed using displacement encoding with stimulated echoes, resulting in three signal components. The free induction decay (FID), arising from spins undergoing T1-relaxation, is not displacement encoded and impairs the displacement acquired. Techniques for suppressing the FID exist; however, a residual will remain. The effect of the residual is difficult to distinguish and investigate in vitro and in vivo. In this work, the influence of the FID as well as of off-resonance effects is evaluated by altering the phase of the FID in relation to the stimulated echo. The results show that the FID and off-resonance effects can impair the accuracy of the displacement measurement acquired. The influence of the FID can be avoided by using an encoded reference. We therefore recommend the assessment of this influence of the FID for each displacement encoding with stimulated echoes protocol.

Place, publisher, year, edition, pages
Wiley, 2011
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-60266 (URN)10.1002/mrm.22692 (DOI)000288612000023 ()
Available from: 2010-10-08 Created: 2010-10-08 Last updated: 2017-12-12
3.
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4. Single Breath Hold Multiple Slice DENSE MRI
Open this publication in new window or tab >>Single Breath Hold Multiple Slice DENSE MRI
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2010 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 63, no 5, 1411-1414 p.Article in journal (Refereed) Published
Abstract [en]

A method to acquire multiple displacement encoded slices within asingle breath hold is presented. Efficiency is improved overconventional Displacement ENcoding with Stimulated Echoes (DENSE) without compromising image quality by read-out of multiple slices inthe same cardiac cycle, thus utilizing the position encoded stimulatedecho available in the whole heart. The method was evaluated bycomparing strain values obtained using the proposed method to strainvalues obtained by conventional separate breath hold single-sliceDENSE acquisitions. Good agreement (Lagrangian E2 strainbias=0.000, 95% limits of agreement ±0.04,root-mean-square-difference 0.02 (9.4% of the mean end-systolic E2)) was found between the methods, indicating that the proposedmethod can replace a multiple breath hold acquisition. Eliminating theneed for multiple breath holds reduces the risk of changes in breathhold positions or heart rate, results in higher patient comfort andfacilitates inclusion of DENSE in a clinical routine protocol.

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd, 2010
Keyword
DENSE, strain, multi-slice, breath hold, cardiac function
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-51974 (URN)10.1002/mrm.22305 (DOI)000277098100030 ()
Available from: 2009-11-25 Created: 2009-11-25 Last updated: 2017-12-12Bibliographically approved
5. Myocardial strains from 3D DENSE magnetic resonance imaging
Open this publication in new window or tab >>Myocardial strains from 3D DENSE magnetic resonance imaging
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D transmural kinematic analyses of human myocardium possible in the clinic and for research purposes. As data acquisition technologies improve, quantification methods for cardiac kinematics need to be adapted and validated on the new types of data. In the present paper, a previously presented polynomial method for cardiac strain quantification is extended to quantify 3D strains from DENSE magnetic resonance imaging data. The method yields accurate results when validated against an analytical standard, and is applied to in vivo data from a healthy  human heart. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains agree

Keyword
Strain, 3D, myocardium, DENSE, transmural
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-60201 (URN)
Available from: 2010-10-07 Created: 2010-10-07 Last updated: 2016-03-14

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