1. Automated segmentation of multifocal basal ganglia T2*-weighted MRI hypointensities
- Author
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Glatz, Andreas, Bastin, Mark E., Kiker, Alexander J., Deary, Ian J., Wardlaw, Joanna M., and Valdés Hernández, Maria C.
- Subjects
Male ,Aging ,Mineralization ,Cognitive Neuroscience ,Magnetic Resonance Imaging ,Article ,Basal Ganglia ,Cohort Studies ,Ageing ,Automated segmentation ,Neurology ,Image Interpretation, Computer-Assisted ,Focal T2*-weighted MRI hypointensities ,Outlier detection ,Humans ,Female ,Magnetic resonance imaging (MRI) ,Aged - Abstract
Multifocal basal ganglia T2*-weighted (T2*w) hypointensities, which are believed to arise mainly from vascular mineralization, were recently proposed as a novel MRI biomarker for small vessel disease and ageing. These T2*w hypointensities are typically segmented semi-automatically, which is time consuming, associated with a high intra-rater variability and low inter-rater agreement. To address these limitations, we developed a fully automated, unsupervised segmentation method for basal ganglia T2*w hypointensities. This method requires conventional, co-registered T2*w and T1-weighted (T1w) volumes, as well as region-of-interest (ROI) masks for the basal ganglia and adjacent internal capsule generated automatically from T1w MRI. The basal ganglia T2*w hypointensities were then segmented with thresholds derived with an adaptive outlier detection method from respective bivariate T2*w/T1w intensity distributions in each ROI. Artefacts were reduced by filtering connected components in the initial masks based on their standardised T2*w intensity variance. The segmentation method was validated using a custom-built phantom containing mineral deposit models, i.e. gel beads doped with 3 different contrast agents in 7 different concentrations, as well as with MRI data from 98 community-dwelling older subjects in their seventies with a wide range of basal ganglia T2*w hypointensities. The method produced basal ganglia T2*w hypointensity masks that were in substantial volumetric and spatial agreement with those generated by an experienced rater (Jaccard index = 0.62 ± 0.40). These promising results suggest that this method may have use in automatic segmentation of basal ganglia T2*w hypointensities in studies of small vessel disease and ageing., Highlights • A novel method segmented focal T2*-weighted MRI hypointensities automatically. • The method was validated with MRI of a novel phantom and 98 elderly subjects. • The subject masks from the method and an experienced rater overlapped substantially. • The method is potentially useful for research into small vessel disease and ageing.
- Published
- 2015