| 1. |
- Dyrby, Tim B, et al.
(författare)
-
Segmentation of age-related white matter changes in a clinical multi-center study.
- 2008
-
Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119. ; 41:2, s. 335-45
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 2. |
- Ropele, Stefan, et al.
(författare)
-
Quantitation of brain tissue changes associated with white matter hyperintensities by diffusion-weighted and magnetization transfer imaging: the LADIS (Leukoaraiosis and Disability in the Elderly) study.
- 2009
-
Ingår i: Journal of magnetic resonance imaging : JMRI. - : Wiley. - 1053-1807 .- 1522-2586. ; 29:2, s. 268-74
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To explore the value of diffusion-weighted imaging (DWI) and magnetization transfer imaging (MTI) for the improved detection and quantification of cerebral tissue changes associated with ageing and white matter hyperintensities (WMH). MATERIALS AND METHODS: DWI (n = 340) and MTI (n = 177) were performed in nine centers of the multinational Leukoaraiosis And DISability (LADIS) study investigating the impact of WMH on 65- to 85-year-old individuals without prior disability. We assessed the apparent diffusion coefficient (ADC) and magnetization transfer ratio (MTR) of normal appearing brain tissue (NABT) and within WMH and related them to subjects' age and WHM severity according to the Fazekas score. RESULTS: ADC and MTR values showed a significant inter-site variation, which was stronger for the MTR. After z-transformation multiple regression analysis revealed WMH severity and age as significant predictors of global ADC and MTR changes. Only lesional ADC, but not MTR was related to WMH severity. CONCLUSION: ADC and MTR are both sensitive for age and WMH related changes in NABT. The ADC is more sensitive for tissue changes within WMH and appears to be more robust for multicenter settings.
|
|
| 3. |
|
|
