Automated segmentation of multifocal basal ganglia T2*-weighted MRI hypointensities

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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 and appearance on T1w MRI. 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.
Original languageEnglish
Pages (from-to)332-346
Number of pages15
JournalNeuroImage
Volume105
Early online date14 Oct 2014
DOIs
Publication statusPublished - 15 Jan 2015

Keywords

  • Magnetic resonance imaging (MRI)
  • Basal ganglia
  • Mineralization
  • Ageing
  • Focal T2*-weighted MRI hypointensities
  • Automated segmentation
  • Outlier detection
  • MAGNETIC-RESONANCE
  • BRAIN IRON
  • TRANSVERSE RELAXATION
  • IMAGES
  • ROBUST
  • AGE
  • BIRTH
  • MINERALIZATION
  • OPTIMIZATION
  • DEPOSITS

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