Surface fluid registration and multivariate tensor-based morphometry in newborns - the effects of prematurity on the putamen

Abstract

Many disorders that affect the brain can cause shape changes in subcortical structures, and these may provide biomarkers for disease detection and progression. Automatic tools are needed to accurately identify and characterize these alterations. In recent work, we developed a surface multivariate tensor-based morphometry analysis (mTBM) to detect morphological group differences in subcortical structures, and we applied this method to study HIV/AIDS, William's syndrome, Alzheimer's disease and prematurity. Here we will focus more specifically on mTBM in neonates, which, in its current form, starts with manually segmented subcortical structures from MRI images of a two subject groups, places a conformal grid on each of their surfaces, registers them to a template through a constrained harmonic map and provides statistical comparisons between the two groups, at each vertex of the template grid. We improve this pipeline in two ways: first by replacing the constrained harmonic map with a new fluid registration algorithm that we recently developed. Secondly, by optimizing the pipeline to study the putamen in newborns. Our analysis is applied to the comparison of the putamen in premature and term born neonates. Recent whole-brain volumetric studies have detected differences in this structure in babies born preterm. Here we add to the literature on this topic by zooming in on this structure, and by generating the first surface-based maps of these changes. To do so, we use a dataset of manually segmented putamens from T1-weighted brain MR images from 17 preterm and 18 term-born neonates. Statistical comparisons between the two groups are performed via four methods: univariate and multivariate tensor-based morphometry, the commonly used medial axis distance, and a combination of the last two statistics. We detect widespread statistically significant differences in morphology between the two groups that are consistent across statistics, but more extensive for multivariate measures.

Fig. 1

The proposed system. The putamen is segmented from T1-weighted images (a). A conformal grid is built on the surface (b), and fluidly registered to a common template (c,d). Surface mTBM is applied to analyze morphometric changes (e)

Fig. 2

Surface-based statistics. Top panel: P-values for the comparison of two groups, for 4 different statistics. The meaning of the different colors is shown in the colorbar. Whole map p-values were: (a) ρ: 0.0966; (b) S: 0.0206; (c) (ρ, S): 0.0177; (d) detJ:0.1021.

Fig. 3

Comparison of Fluid and constrained harmonic registrations Top panel: P-values for the comparison of S with the two registration methods. Bottom panel: P-values for the comparison of ρ with the two methods. The left column represents the fluid registration, while the right one is for the constrained harmonic mapping. The meaning of the different colors is shown in the colorbar. Whole map p-values for the constrained harmonic maps were: (a) ρ: 0.0889; (b) S: 0.055; (c) (ρ, S): 0.0362; (d) detJ: 0.0974.