| 1. |
- Bergvall, Erik, et al.
(författare)
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Regularization of phase contrast magnetic resonance images using optical flow and smoothness constraints
- 2005
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Ingår i: Computers in Cardiology. - 0276-6574. ; 32, s. 33-36
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Konferensbidrag (refereegranskat)abstract
- This paper presents a post processing strategy for myocardial velocity fields obtained by phase contrast magnetic resonance imaging. Such data can be used to track cardiac motion and to calculate strain. The method combines data regularization with optical flow estimation to overcome the partial volume effect in the image acquisition. Validation is performed both in vitro and in vivo and it is shown that the method improves the accuracy of cardiac motion tracking.
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| 2. |
- Bergvall, Erik, et al.
(författare)
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Spline-based cardiac motion tracking using velocity-encoded magnetic resonance imaging.
- 2008
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Ingår i: IEEE Transactions on Medical Imaging. - 1558-254X. ; 27:8, s. 1045-1053
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the problem of tracking cardiac motion and deformation using velocity-encoded magnetic resonance imaging. We expand upon an earlier described method and fit a spatiotemporal motion model to measured velocity data. We investigate several different spatial elements both qualitatively and quantitatively using phantom measurements and data from human subjects. In addition, we also use optical flow estimation by the Horn-Schunk method as complementary data in regions where the velocity measurements are noisy. Our results show that it is possible to obtain good motion tracking accuracy in phantoms with relatively few spatial elements, if the type of element is properly chosen. The use of optical flow can correct some measurement artifacts but may give an underestimation of the magnitude of the deformation. In human subjects the different spatial elements perform quantitatively in a similar way but qualitative differences exists, as shown by a semiquantitative visual scoring of the different methods.
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| 3. |
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| 4. |
- Markenroth Bloch, Karin, et al.
(författare)
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Quantifying coronary sinus flow and global LV perfusion at 3T
- 2009
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Ingår i: BMC Medical Imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 9:9, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Background: Despite the large availability of 3T MR scanners and the potential of high field imaging, this technical platform has yet to prove its usefulness in the cardiac MR setting, where 1.5T remains the established standard. Global perfusion of the left ventricle, as well as the coronary flow reserve (CFR), can provide relevant diagnostic information, and MR measurements of these parameters may benefit from increased field strength. Quantitative flow measurements in the coronary sinus (CS) provide one method to nvestigate these parameters. However, the ability of newly developed faster MR sequences to measure coronary flow during a breath-hold at 3T has not been evaluated. Methods: The aim of this work was to measure CS flow using segmented phase contrast MR (PC MR)on a clinical 3T MR scanner. Parallel imaging was employed to reduce the total acquisition time. Global LV perfusion was calculated by dividing CS flow with left ventricular (LV) mass. The repeatability of the method was investigated by measuring the flow three times in each of the twelve volunteers. Phantom experiments were performed to investigate potential error sources. Results: The average CS flow was determined to 88±33 ml/min and the deduced LV perfusion was 0.60±0.22 ml/min·g, in agreement with published values. The repeatability (1-error) of the three repeated measurements in each subject was on average 84%. Conclusions: This work demonstrates that the combination of high field strength (3T), parallel imaging and segmented gradient echo sequences allow for quantification of the CS flow and global perfusion within a breath-hold.
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| 5. |
- Nilsson, Christer, et al.
(författare)
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Tracking the neurodegeneration of parkinsonian disorders - A pilot study
- 2007
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Ingår i: Neuroradiology. - : Springer Science and Business Media LLC. - 1432-1920 .- 0028-3940. ; 49:2, s. 111-119
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to explore the possibilities of using diffusion tensor imaging (DTI) and tractography (DTT) for the differential diagnosis and monitoring of disease progression in idiopathic Parkinson's disease (IPD), compared with the atypical parkinsonian disorders multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A 3.0-T MR scanner was used. DTI was acquired using a single-shot EPI sequence with diffusion encoding in 32 directions and a voxel size of 2×2×2 mm3. DTI data were analysed and DTT was performed using the PRIDE fibre tracking tool supplied by the manufacturer. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) within each tract were determined. DTI and DTT images in patients with moderate to advanced MSA demonstrated degeneration of the middle cerebellar peduncles and pontine crossing tracts, with decreased FA and increased ADC. This accounted for most of the pontine and cerebellar atrophy characteristic of this disease. In contrast, patients with PSP showed a selective degeneration of the superior cerebellar peduncle. Three-dimensional images of whole-brain white matter tracts demonstrated a reduction of cortical projection fibres in all patients with PSP. Visualization of the selective degeneration of individual fibre tracts, using DTI and DTT, adds qualitative data facilitating the differential diagnosis of parkinsonian disorders. Repeated measurements of FA and ADC values in a whole fibre tract might be used for monitoring disease progression and studying the effect of treatment in neuroprotective trials. The results are preliminary considering the small number of subjects in the study. © Springer-Verlag 2007.
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| 6. |
- Persson, M, et al.
(författare)
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Phase contrast MRI segmentation using multiple cues
- 2005
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Ingår i: SSBA Symposium on Image Analysis.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a method for three-dimensional (3D) segmentation of blood vessels, using a combination of velocity data and magnitude images obtained using phase contrast MRI. In addition to standard MRI images, phase contrast MRI gives velocity information for blood and tissue. The proposed method uses a variational formulation of the segmentation problem which combines different cues; velocity and magnitude. Experiments on phantom and clinical data support the proposed method.
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