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Multidimensional MRI of Cardiac Motion: Acquisition, Reconstruction and Visualization
Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology.
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Methods for measuring deformation and motion of the human heart in-vivo are crucial in the assessment of cardiac function. Applications ranging from basic physiological research, through early detection of disease to follow-up studies, all benefit from improved methods of measuring the dynamics of the heart. This thesis presents new methods for acquisition, reconstruction and visualization of cardiac motion and deformation, based on magnetic resonance imaging.

Local heart wall deformation can be quantified in a strain rate tensor field. This tensor field describes the local deformation excluding rigid body translation and rotation. The drawback of studying this tensor-valued quantity, as opposed to a velocity vector field, is the high dimensionality of the tensor. The problem of visualizing the tensor field is approached by combining a local visualization that displays all degrees of freedom for a single tensor with an overview visualization using a scalar field representation of the complete tensor field. The scalar field is obtained by iterated adaptive filtering of a noise field.

Several methods for synchronizing the magnetic resonance imaging acquisition to the heart beat have previously been used to resolve individual heart phases from multiple cardiac cycles. In the present work, one of these techniques is extended to resolve two temporal dimensions simultaneously, the cardiac cycle and the respiratory cycle. This is combined with volumetric imaging to produce a five-dimensional data set. Furthermore, the acquisition order is optimized in order to reduce eddy current artifacts.

The five-dimensional acquisition either requires very long scan times or can only provide low spatiotemporal resolution. A method that exploits the variation in temporal bandwidth over the imaging volume, k-t BLAST, is described and extended to two simultaneous temporal dimensions. The new method, k-t2 BLAST, allows simultaneous reduction of scan time and improvement of spatial resolution.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2006. , 51 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1262
Keyword [en]
MRI, cardiac, motion, reconstruction
National Category
Computer Vision and Robotics (Autonomous Systems)
Identifiers
URN: urn:nbn:se:liu:diva-7468Local ID: LIU-TEK-LIC-2006:43ISBN: 91-85523-37-2 (print)OAI: oai:DiVA.org:liu-7468DiVA: diva2:22463
Presentation
2006-09-15, Wrannesalen, CMIV, Huvudblocket, Universitetssjukhuset, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2013-08-28
List of papers
1. Tensor Field Visualisation using Adaptive Filtering of Noise Fields combined with Glyph Rendering
Open this publication in new window or tab >>Tensor Field Visualisation using Adaptive Filtering of Noise Fields combined with Glyph Rendering
2002 (English)In: IEEE Visualization 2002 Conference, IEEE , 2002, 371-378 p.Conference paper, Published paper (Refereed)
Abstract [en]

While many methods exist for visualising scalar and vector data, visualisation of tensor data is still troublesome. We present a method for visualising second order tensors in three dimensions using a hybrid between direct volume rendering and glyph rendering.

An overview scalar field is created by using three-dimensional adaptive filtering of a scalar field containing noise. The filtering process is controlled by the tensor field to be visualised, creating patterns that characterise the tensor field. By combining direct volume rendering of the scalar field with standard glyph rendering methods for detailed tensor visualisation, a hybrid solution is created.

A combined volume and glyph renderer was implemented and tested with both synthetic tensors and strain-rate tensors from the human heart muscle, calculated from phase contrast magnetic resonance image data. A comprehensible result could be obtained, giving both an overview of the tensor field as well as detailed information on individual tensors.

Place, publisher, year, edition, pages
IEEE, 2002
Keyword
Tensor, Visualisation, Volume rendering, Glyph rendering, Hybrid rendering, Strain-rate
National Category
Medical and Health Sciences Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14011 (URN)
Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2013-09-03Bibliographically approved
2. Five-dimensional MRI Incorporating Simultaneous Resolution of Cardiac and Respiratory Phases for Volumetric Imaging
Open this publication in new window or tab >>Five-dimensional MRI Incorporating Simultaneous Resolution of Cardiac and Respiratory Phases for Volumetric Imaging
2006 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 25, no 1, 113-121 p.Article in journal (Refereed) Published
Abstract [en]

Purpose

To develop a new volumetric imaging method resolved over both the cardiac and respiratory cycles, to enable future physiological and pathophysiological studies of respiratory-related cardiac motion.

Materials and Methods

An acquisition scheme is proposed whereby the k-space acquisition order is controlled in real-time by the current cardiac and respiratory phases. To reduce eddy-current effects induced by sudden jumps in k-space, the acquisition order is further optimized by the use of a Hilbert curve trajectory in the ky-kz plane. A complete three-dimensional (3D) k-space is acquired for all combinations of cardiac and respiratory phases, yielding a five-dimensional (5D) data set after retrospective reconstruction.

Results

Left (LV) and right ventricular (RV) wall excursion was measured in a healthy volunteer. Diastolic LV diameter was shown to increase during expiration and decrease during inspiration, as expected from previous echocardiography studies. The LV volume was estimated for all cardiac and respiratory phases with the use of a fully 3D segmentation tool. The results confirmed that the diastolic LV volume increased during expiration and decreased during inspiration.

Conclusion

With its ability to measure motion anywhere in the heart, the described technique provides a promising approach for in-depth description of interventricular coupling, including 3D ventricular volumes, during both the cardiac and respiratory cycles.

Keyword
respiration, septal motion, interventricular coupling, volumetric MRI, cine imaging
National Category
Medical and Health Sciences Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-14012 (URN)10.1002/jmri.20820 (DOI)000243250800014 ()
Available from: 2006-10-04 Created: 2006-10-04 Last updated: 2017-12-13Bibliographically approved
3. k-t2 BLAST: Exploiting spatiotemporal structure in simultaneously cardiac and respiratory time-resolved volumetric imaging
Open this publication in new window or tab >>k-t2 BLAST: Exploiting spatiotemporal structure in simultaneously cardiac and respiratory time-resolved volumetric imaging
2007 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 58, no 5, 922-930 p.Article in journal (Refereed) Published
Abstract [en]

Multidimensional imaging resolving both the cardiac and respiratory cycles simultaneously has the potential to describe important physiological interdependences between the heart and pulmonary processes. A fully five-dimensional acquisition with three spatial and two temporal dimensions is hampered, however, by the long acquisition time and low spatial resolution. A technique is proposed to reduce the scan time substantially by extending the k-t BLAST framework to two temporal dimensions. By sampling the k-t space sparsely in a lattice grid, the signal in the transform domain, x-f space, can be densely packed, exploiting the fact that large regions in the field of view have low temporal bandwidth. A volumetric online prospective triggering approach with full cardiac and respiratory cycle coverage was implemented. Retrospective temporal interpolation was used to refine the timing estimates for the center of k-space, which is sampled for all cardiac and respiratory time frames. This resulted in reduced reconstruction error compared with conventional k-t BLAST reconstruction. The k-t2 BLAST technique was evaluated by decimating a fully sampled five-dimensional data set, and feasibility was further demonstrated by performing sparsely sampled acquisitions. Compared to the fully sampled data, a fourfold improvement in spatial resolution was accomplished in approximately half the scan time.

Keyword
Cine imaging, k-t BLAST, Respiration, Volumetric MRI
National Category
Engineering and Technology Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-47833 (URN)10.1002/mrm.21295 (DOI)000250560000009 ()
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13Bibliographically approved

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Sigfridsson, Andreas

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