Abstract
Structural (also known as anatomical) and diffusion MRI provide complimentary anatomical and microstructural characterization of early brain maturation. However, the existing models of the developing brain in time include only either structural or diffusion MRI channels. Furthermore, there is a lack of tools for combined analysis of structural and diffusion MRI in the same reference space. In this work, we propose a methodology to generate a multi-channel (MC) continuous spatio-temporal parametrized atlas of the brain development that combines multiple MRI-derived parameters in the same anatomical space during 37–44 weeks of postmenstrual age range. We co-align structural and diffusion MRI of 170 normal term subjects from the developing Human Connectomme Project using MC registration driven by both T2-weighted and orientation distribution functions channels and fit the Gompertz model to the signals and spatial transformations in time. The resulting atlas consists of 14 spatio-temporal microstructural indices and two parcellation maps delineating white matter tracts and neonatal transient structures. In order to demonstrate applicability of the atlas for quantitative region-specific studies, a comparison analysis of 140 term and 40 preterm subjects scanned at the term-equivalent age is performed using different MRI-derived microstructural indices in the atlas reference space for multiple white matter regions, including the transient compartments. The atlas and software will be available after publication of the article1.
Highlights
In addition to being a routine diagnostic tool in neonatal brain imaging (Rutherford et al, 2010), MRI has been widely used for quantification and interpretation of neonatal brain development in term- and preterm-born infants
We investigated six scenarios of registration of individual developing Human Connectome Project (dHCP) subjects to the templates Ycref (t) based on different combinations of channels: (I) T2w, (II) T2w + Mcortex, (III) T2w + Mcortex + fractional anisotropy (FA), (IV) T2w + Mcortex + orientation distribution functions (ODF)(LAC), (V) T2w + ODF(LAC) and (VI) ODF(LAC)
The multi-channel registration pipeline implemented in MRtrix3 employs the novel local angular correlation similarity metric for ODF channels, LNCC metric for structural T2w and weighted fusion of the updates to the displacement fields
Summary
In addition to being a routine diagnostic tool in neonatal brain imaging (Rutherford et al, 2010), MRI has been widely used for quantification and interpretation of neonatal brain development in term- and preterm-born infants. The structural MRI-derived metrics most commonly used in neonatal brain studies include tissue- and structure-specific volumetry (Kuklisova-Murgasova et al, 2011; Makropoulos et al, 2016; Thompson et al, 2019) and surface measurements such as cortical thickness and curvature (Bozek et al, 2018; Fenchel et al, 2020) that can be extracted from automated segmentations (Makropoulos et al, 2014). Automated segmentation of T2w images has been applied for quantification of the volume of myelinated regions (Wang et al, 2019). Quantitative and semi-quantitative metrics applied to developing neonatal brains include the T1w/T2w signal ratio associated with myelin content (Bozek et al, 2018) and T2 relaxometry (Pannek et al, 2013; Kulikova et al, 2015; Wu et al, 2017; Knight et al, 2018)
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