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Multidimensional magnetic resonance imaging: new methods for analysis of cardiovascular dynamics
Linköping University, Department of Biomedical Engineering. Linköping University, Department of Medicine and Care. Linköping University, The Institute of Technology.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular flow and motion occur in three-dimensional (3D) space and vary dynamically over the cardiac cycle. The description of these complicated patterns using non-invasive imaging requires new tools for data acquisition, processing and visualization. In this thesis, a number of techniques are presented, all of which aim at improving the description of multidimensional cardiovascular flow and motion.

For the study of cardiac motion, a new M-mode method was developed that uses time-resolved image data to retrospectively calculate an M-mode image along an arbitrary line. This reduces the dimensionality of the acquired image data to one dimension plus time, which facilitates the analysis of the motion of cardiac structures. In order to describe flow patterns within the heart and great vessels, phase contrast magnetic resonance imaging (MRI) can be used to accurately measure velocities. Existing techniques for the acquisition of phase contrast data were extended in order to acquire time-resolved 3D image data that contain information about all three velocity components in each voxel. A number of possible approaches for reducing the scan time required were applied. Reducing the scan time in MRI often results in images with a poor signal-to-noise ratio (SNR). Image processing techniques were therefore investigated that utilize adaptive filtering in order to reduce the noise level, while still preserving the details of small structures. Once multidimensional image data are acquired, there is an immediate need to visualize the data in a comprehensible way. Particle trace visualization of velocity vector data was applied in order to study flow patterns in the human heart. Using these methods, completely new insights into the patterns of blood flow within the left atrium were achieved. This and future applications are made possible by the powerful combination of massive multidimensional data sets and tools developed specifically for the complicated conditions of cardiovascular flow.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2003. , 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 807
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-29438Local ID: 14784ISBN: 91-7373-616-3 (print)OAI: oai:DiVA.org:liu-29438DiVA: diva2:250253
Public defence
2003-04-29, Föreläsningssal Conrad, Universitetssjukhuset, Linköping, 13:15 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-01-04
List of papers
1. M-mode magnetic resonance imaging: a new modality for assessing cardiac function
Open this publication in new window or tab >>M-mode magnetic resonance imaging: a new modality for assessing cardiac function
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1995 (English)In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 15, no 4, 397-407 p.Article in journal (Refereed) Published
Abstract [en]

Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.

Keyword
cardiac motion, heart, image processing, MRI, M-mode
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-79469 (URN)10.1111/j.1475-097X.1995.tb00529.x (DOI)
Available from: 2012-08-02 Created: 2012-08-02 Last updated: 2017-12-07Bibliographically approved
2. Temporally resolved 3D phase-contrast imaging
Open this publication in new window or tab >>Temporally resolved 3D phase-contrast imaging
1996 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 36, no 5, 800-803 p.Article in journal (Refereed) Published
Abstract [en]

A conventional 3D phase contrast acquisition generates images with good spatial resolution, but often gives rise to artifacts due to pulsatile flow. 2D cine phase contrast, on the other hand, can register dynamic flow, but has a poor spatial resolution perpendicular to the imaging plane. A combination of both high spatial and temporal resolution may be advantageous in some cases, both in quantitative flow measurements and in MR angiography. The described 3D cine phase contrast pulse sequence creates a temporally resolved series of 3D data sets with velocity encoded data.

Keyword
retrospective gating, flow imaging, velocity mapping, magnetic resonance angiography
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-86800 (URN)10.1002/mrm.1910360521 (DOI)
Available from: 2013-01-04 Created: 2013-01-04 Last updated: 2017-12-06
3. Particle trace visualization of intracardiac flow using time-resolved 3D phase contrast MRI
Open this publication in new window or tab >>Particle trace visualization of intracardiac flow using time-resolved 3D phase contrast MRI
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1999 (English)In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 41, no 4, 793-799 p.Article in journal (Refereed) Published
Abstract [en]

The flow patterns in the human heart are complex and difficult to visualize using conventional two-dimensional (2D) modalities, whether they depict a single velocity component (Doppler echocardiography) or all three components in a few slices (2D phase contrast MRI). To avoid these shortcomings, a temporally resolved 3D phase contrast technique was used to derive data describing the intracardiac velocity fields in normal volunteers. The MRI data were corrected for phase shifts caused by eddy currents and concomitant gradient fields, with improvement in the accuracy of subsequent flow visualizations. Pathlines describing the blood pathways through the heart were generated from the temporally resolved velocity data, starting from user-specified locations and time frames. Flow trajectories were displayed as 3D particle traces, with simultaneous demonstration of morphologic 2D slices. This type of visualization is intuitive and interactive and may extend our understanding of dynamic and previously unrecognized patterns of intracardiac flow.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26701 (URN)10.1002/(SICI)1522-2594(199904)41:4<793::AID-MRM19>3.0.CO;2-2 (DOI)11291 (Local ID)11291 (Archive number)11291 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2016-03-14
4. Three-dimensional flow in the human left atrium
Open this publication in new window or tab >>Three-dimensional flow in the human left atrium
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2001 (English)In: Heart, ISSN 1355-6037, Vol. 86, no 4, 448-455 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Abnormal flow patterns in the left atrium in atrial fibrillation or mitral stenosis are associated with an increased risk of thrombosis and systemic embolisation; the characteristics of normal atrial flow that avoid stasis have not been well defined.

OBJECTIVES: To present a three dimensional particle trace visualisation of normal left atrial flow in vivo, constructed from flow velocities in three dimensional space.

METHODS: Particle trace visualisation of time resolved three dimensional magnetic resonance imaging velocity measurements was used to provide a display of intracardiac flow without the limitations of angle sensitivity or restriction to imaging planes. Global flow patterns of the left atrium were studied in 11 healthy volunteers.

RESULTS: In all subjects vortical flow was observed in the atrium during systole and diastolic diastasis (mean (SD) duration of systolic vortex, 280 (77) ms; and of diastolic vortex, 256 (118) ms). The volume incorporated and recirculated within the vortices originated predominantly from the left pulmonary veins. Inflow from the right veins passed along the vortex periphery, constrained between the vortex and the atrial wall.

CONCLUSIONS: Global left atrial flow in the normal human heart comprises consistent patterns specific to the phase of the cardiac cycle. Separate paths of left and right pulmonary venous inflow and vortex formation may have beneficial effects in avoiding left atrial stasis in the normal subject in sinus rhythm.

Keyword
atrium, blood flow, magnetic resonance imaging, haemodynamics
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-14554 (URN)10.1136/heart.86.4.448 (DOI)
Available from: 2007-06-04 Created: 2007-06-04 Last updated: 2016-03-14
5. Three-dimensional adaptive filtering in magnetic resonance angiography
Open this publication in new window or tab >>Three-dimensional adaptive filtering in magnetic resonance angiography
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2001 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 14, no 1, 63-71 p.Article in journal (Refereed) Published
Abstract [en]

In order to enhance 3D image data from magnetic resonance angiography (MRA), a novel method based on the theory of multidimensional adaptive filtering has been developed. The purpose of the technique is to suppress image noise while enhancing important structures. The method is based on local structure estimation using six 3D orientation selective filters, followed by an adaptive filtering step controlled by the local structure information. The complete filtering procedure requires approximately 3 minutes of computational time on a standard workstation for a 256 × 256 × 64 data set. The method has been evaluated using a mathematical vessel model and in vivo MRA data (both phase contrast and time of flight (TOF)). 3D adaptive filtering results in a better delineation of small blood vessels and efficiently reduces the high-frequency noise. Depending on the data acquisition and the original data type, contrast-to-noise ratio (CNR) improvements of up to 179% (8.9 dB) were observed. 3D adaptive filtering may provide an alternative to prolonging the scan time or using contrast agents in MRA when the CNR is low.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26713 (URN)10.1002/jmri.1152 (DOI)11307 (Local ID)11307 (Archive number)11307 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2013-08-28

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