| 1. |
- Clement, Patricia, et al.
(author)
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Variability of physiological brain perfusion in healthy subjects : A systematic review of modifiers. Considerations for multi-center ASL studies
- 2018
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In: Journal of Cerebral Blood Flow and Metabolism. - 0271-678X .- 1559-7016. ; 38:9, s. 1418-1437
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Research review (peer-reviewed)abstract
- Quantitative measurements of brain perfusion are influenced by perfusion-modifiers. Standardization of measurement conditions and correction for important modifiers is essential to improve accuracy and to facilitate the interpretation of perfusion-derived parameters. An extensive literature search was carried out for factors influencing quantitative measurements of perfusion in the human brain unrelated to medication use. A total of 58 perfusion modifiers were categorized into four groups. Several factors (e.g., caffeine, aging, and blood gases) were found to induce a considerable effect on brain perfusion that was consistent across different studies; for other factors, the modifying effect was found to be debatable, due to contradictory results or lack of evidence. Using the results of this review, we propose a standard operating procedure, based on practices already implemented in several research centers. Also, a theory of ' deep MRI physiotyping' is inferred from the combined knowledge of factors influencing brain perfusion as a strategy to reduce variance by taking both personal information and the presence or absence of perfusion modifiers into account. We hypothesize that this will allow to personalize the concept of normality, as well as to reach more rigorous and earlier diagnoses of brain disorders.
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| 2. |
- Dyrby, Tim B, et al.
(author)
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Segmentation of age-related white matter changes in a clinical multi-center study.
- 2008
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In: NeuroImage. - : Elsevier BV. - 1053-8119. ; 41:2, s. 335-45
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Journal article (peer-reviewed)abstract
- Age-related white matter changes (WMC) are thought to be a marker of vascular pathology, and have been associated with motor and cognitive deficits. In the present study, an optimized artificial neural network was used as an automatic segmentation method to produce probabilistic maps of WMC in a clinical multi-center study. The neural network uses information from T1- and T2-weighted and fluid attenuation inversion recovery (FLAIR) magnetic resonance (MR) scans, neighboring voxels and spatial location. Generalizability of the neural network was optimized by including the Optimal Brain Damage (OBD) pruning method in the training stage. Six optimized neural networks were produced to investigate the impact of different input information on WMC segmentation. The automatic segmentation method was applied to MR scans of 362 non-demented elderly subjects from 11 centers in the European multi-center study Leukoaraiosis And Disability (LADIS). Semi-manually delineated WMC were used for validating the segmentation produced by the neural networks. The neural network segmentation demonstrated high consistency between subjects and centers, making it a promising technique for large studies. For WMC volumes less than 10 ml, an increasing discrepancy between semi-manual and neural network segmentation was observed using the similarity index (SI) measure. The use of all three image modalities significantly improved cross-center generalizability compared to neural networks using the FLAIR image only. Expert knowledge not available to the neural networks was a minor source of discrepancy, while variation in MR scan quality constituted the largest source of error.
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| 3. |
- Falk, Anna, et al.
(author)
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Discrimination between glioma grades II and III in suspected low-grade gliomas using dynamic contrast-enhanced and dynamic susceptibility contrast perfusion MR imaging : a histogram analysis approach
- 2014
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In: Neuroradiology. - : Springer Science and Business Media LLC. - 0028-3940 .- 1432-1920. ; 56:12, s. 1031-1038
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Journal article (peer-reviewed)abstract
- IntroductionPerfusion magnetic resonance imaging (MRI) can be used in the pre-operative assessment of brain tumours. The aim of this prospective study was to identify the perfusion parameters from dynamic contrast-enhanced (DCE) and dynamic susceptibility contrast (DSC) perfusion imaging that could best discriminate between grade II and III gliomas.MethodsMRI (3 T) including morphological ((T2 fluid attenuated inversion recovery (FLAIR) and T1-weighted (T1W)+Gd)) and perfusion (DCE and DSC) sequences was performed in 39 patients with newly diagnosed suspected low-grade glioma after written informed consent in this review board-approved study. Regions of interests (ROIs) in tumour area were delineated on FLAIR images co-registered to DCE and DSC, respectively, in 25 patients with histopathological grade II (n = 18) and III (n = 7) gliomas. Statistical analysis of differences between grade II and grade III gliomas in histogram perfusion parameters was performed, and the areas under the curves (AUC) from the ROC analyses were evaluated.ResultsIn DCE, the skewness of transfer constant (k trans) was found superior for differentiating grade II from grade III in all gliomas (AUC 0.76). In DSC, the standard deviation of relative cerebral blood flow (rCBF) was found superior for differentiating grade II from grade III gliomas (AUC 0.80).ConclusionsHistogram parameters from k trans (DCE) and rCBF (DSC) could most efficiently discriminate between grade II and grade III gliomas.
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| 4. |
- Nylander, Ruta, et al.
(author)
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Quantitative and qualitative MRI evaluation of cerebral small vessel disease in an elderly population : a longitudinal study
- 2018
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In: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 59:5, s. 612-618
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Journal article (peer-reviewed)abstract
- Background: Cerebral white matter hyperintensities (WMHs), lacunes, and microbleeds are seen on magnetic resonance imaging (MRI) in small vessel disease (SVD).Purpose: To assess SVD on MRI and its evolution over five years in an elderly population and to investigate whether relative cerebral blood flow (rCBF) at baseline was related to the progression of white matter (WM) lesions.Material and Methods: In a population-based study, 406 participants aged 75 years underwent morphological MRI of the brain and 252 of them again at age 80 years. At age 75 years, a perfusion scan was also done. WMHs were evaluated qualitatively (visual scoring) and quantitatively (CASCADE software). Lacunes and microbleeds were counted.Results: A significant progression of the WMH score and WMH volume occurred over five years (P < 0.0001). New lacunes were seen in 10%. Participants with new lacunes at age 80 years showed a more pronounced increase in WMHs (P < 0.0001). Microbleeds were present in 14% at age 75 years. The visual WMH score was significantly associated with the presence of microbleeds (P < 0.0001). There was no relationship between total WM rCBF and WMH volume at age 75 years, and no significant associations between regional or total rCBF at age 75 years and changes in WMH volume over five years. The total WM and GM volume decreased significantly between the ages of 75 and 80 years (P < 0.0001).Conclusion: MRI manifestations of SVD progressed over five years in an elderly population (age range=75-80 years). rCBF was not associated with WMH volume or progression of WMH volume.
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