Segmentation of the thalamus in MRI based on T1 and T2

• Published in: NeuroImage (Orlando, Fla.) Fla.), 2011-06, Vol.56 (3), p.939-950
• Main Authors: Traynor, Catherine R., Barker, Gareth J., Crum, William R., Williams, Steve C.R., Richardson, Mark P.
• Format: Article
• Language: English
• Subjects: Algorithms; Brain Mapping - methods; Cluster Analysis; Computer Simulation; Data Interpretation, Statistical; Datasets; Diffusion Tensor Imaging; Functional Laterality - physiology; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging - methods; Male; Methods; Models, Statistical; NMR; Nuclear magnetic resonance; Population; Reproducibility of Results; Thalamic Nuclei - anatomy & histology; Thalamus - anatomy & histology; Young Adult
• ISSN: 1053-8119; 1095-9572
• DOI: 10.1016/j.neuroimage.2011.01.083

Reliable identification of thalamic nuclei is required to improve positioning of electrodes in Deep Brain Stimulation (DBS), and to allow the role of individual thalamic nuclei in health and disease to be fully investigated. In this work, a previously proposed method for identifying sub-regions within the thalamus based on differences in their T1 and T2 values is explored in detail. The effect on the segmentation of T1 and T2 dependence weighted against priors for spatial position and extent was investigated. When T1 and T2 dependence was highly weighted, good distinction between identified regions was obtained in T1/T2 feature-space, but no contiguous anatomically distinct regions were identified within the thalamus. Incorporating spatial priors was necessary to ensure anatomically distinct regions were defined. Optimal values for segmentation parameters were obtained by assessing performance on a ‘synthetic thalamus’. Using these optimum input parameters, within- and between-subjects reproducibility was assessed. Good reproducibility was obtained when six regions were specified to be identified in the thalamus. The six regions identified were similar in the majority of the normal subject group. However, intriguingly these regions were different from those obtained in the same subjects using a well-known connectivity-based segmentation technique. This method shows promise to identify intrathalamic structures on the basis of T1 and T2 signal. A comprehensive characterisation of thalamic nuclei may require a fully multi-modal approach. ► Thalamic nuclei are not readily discerned using structural MRI. ► Previous work showed quantitative T1 and T2 images can be used to segment thalamus. ► The dependence of segmentation on T1/T2 versus anatomical priors was investigated. ► Within- and between-subjects reliability was shown to be good. ► The resulting segmentation was different to an established DTI-based method.