| 1. |
- Damangir, Soheil, et al.
(författare)
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Multispectral MRI segmentation of age related white matter changes using a cascade of support vector machines
- 2012
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Ingår i: Journal of the Neurological Sciences. - : Elsevier BV. - 0022-510X .- 1878-5883. ; 322:1-2, s. 211-216
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Tidskriftsartikel (refereegranskat)abstract
- White matter changes (WMC) are the focus of intensive research and have been linked to cognitive impairment and depression in the elderly. Cumbersome manual outlining procedures make research on WMC labor intensive and prone to subjective bias. We present a fast, fully automated method for WMC segmentation using a cascade of reduced support vector machines (SVMs) with active learning. Data of 102 subjects was used in this study. Two MRI sequences (T1-weighted and FLAIR) and masks of manually outlined WMC from each subject were used for the image analysis. The segmentation framework comprises pre-processing, classification (training and core segmentation) and post-processing. After pre-processing, the model was trained on two subjects and tested on the remaining 100 subjects. The effectiveness and robustness of the classification was assessed using the receiver operating curve technique. The cascade of SVMs segmentation framework outputted accurate results with high sensitivity (90%) and specificity (99.5%) values, with the manually outlined WMC as reference. An algorithm for the segmentation of WMC is proposed. This is a completely competitive and fast automatic segmentation framework, capable of using different input sequences, without changes or restrictions of the image analysis algorithm.
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| 2. |
- Damangir, Soheil
(författare)
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The matter of white and gray matter in cognitive impairment
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cognitive impairment spans from minor subjective cognitive impairment to disabling dementia. Many biomarkers have been developed to monitor different aspects of cognitive impairment. Magnetic resonance imaging is the most used neuroimaging biomarker in research and can measure gray matter (GM) and white matter (WM) changes. Although there is a consensus that atrophy in GM is a marker for neuronal loss, there is little evidence assessing the role of WM changes. The aim of this thesis is to first develop a tool to reliably measure the changes in WM in the form of white matter hyperintensities (WMH) and second to evaluate the role of WM and GM changes in the early stages of cognitive decline. In Study I and Study II, a fully automated method for segmentation of WMH has been developed and validated. Validation results indicated that the WMH segmentation was performed with high similarity to manual delineation and with superb reproducibility. In Study III, coronary heart disease (CHD) and hypertension, which are known to contribute to WM damage, were examined and their effect on GM and WM changes was investigated on a group of 69 individuals with 30-year follow-up. We showed that CHD and hypertension indeed affect the GM volume and thickness and the effect of CHD is partially independent of hypertension. However, the results indicate no significant effect on WMH, which we believe is due to the fact that WMH were measured as a crude total volume. In Study IV, a pipeline was developed to isolate the WM tract connecting each GM region to the rest of the brain and to measure the burden of WMH on each tract, hereinafter tractbased WMH. We used a cohort of 257 cognitively normal (CTL), 87 subjective cognitive impairment (SCI) and 124 mild cognitive impairment (MCI) subjects and examined their GM volume, tract-based WMH and cognitive performance. Our results indicated that the fraction of variance in GM volume that can be explained by tract-based WMH in SCI subjects is significantly higher than in both CTL and MCI subjects. The results also showed that in subjects with high and low cognitive performance, tract-based WMH can barely explain any GM volume change. However, in subjects with slight cognitive impairment tract-based WMH can explain the changes in GM volume. In summary, we investigated different ways of measuring the damage of WMH and showed that the role of WMH is more pronounced when measuring them in relation to the WM tract they affect. The effect of WMH on GM has been shown to be mainly in the earlier stages of cognitive impairment.
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| 3. |
- Nylander, Ruta, et al.
(författare)
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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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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 59:5, s. 612-618
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Tidskriftsartikel (refereegranskat)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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