Characterisation of the neonatal brain using myelin-sensitive magnetisation transfer imaging

Area of Science:

• Neuroimaging
• Developmental Neuroscience
• Pediatric Radiology

Background:

• Encephalopathy of prematurity involves white matter dysmaturation and hypomyelination.
• Magnetisation transfer imaging (MTI) provides surrogate markers for myelination, including magnetisation transfer ratio (MTR) and magnetisation transfer saturation (MTsat).
• Understanding white matter development in neonates is crucial for identifying neurodevelopmental impairments.

Purpose of the Study:

• To characterize MTR and MTsat in the developing brain of neonates.
• To investigate the effects of gestational age at scan and preterm birth on MTI markers.
• To explore correlations between MTI metrics and conventional MRI markers of white matter integrity (FA, RD, T1w/T2w ratio).

Main Methods:

• Analysis of MTR and MTsat in 105 neonates using voxel-wise and tract-of-interest approaches.
• Comparison of MTI metrics between preterm infants at term-equivalent age and term controls.
• Correlation analysis with fractional anisotropy (FA), radial diffusivity (RD), and T1w/T2w ratio.

Main Results:

• MTR and MTsat positively correlate with gestational age at scan.
• Preterm infants at term-equivalent age exhibit lower MTsat in specific corpus callosum regions and altered MTR in central white matter tracts.
• Strong correlations were observed between MTI metrics and RD, with moderate correlations with FA and T1w/T2w ratio.

Conclusions:

• MTI metrics reflect increased myelin density during early postnatal development.
• Preterm infants show evidence of reduced myelination and cellular/axonal density compared to term-born infants.
• MTI-derived features offer valuable insights into myelination's contribution to conventional MRI metrics in early brain development.