Harmonization of slice thickness through resampling improves comparability of MRI-derived neonatal brain volumes.

Purpose: To assess reliability and agreement of brain volume measurements from neonatal T2-weighted magnetic resonance imaging (MRI) scans acquired with different slice thickness settings (i.e., 2 mm, 3 mm and 3 mm resampled). Methods: We used term-equivalent (38-45 weeks postmenstrual age) T2-weighted MRI scans with slice thicknesses of 2 mm and 3 mm from a subset of 40 preterm and term infants (27-40 weeks' gestation) from two existing neonatal imaging cohorts. Resampling of the 2 mm scans to a 3 mm grid provided a third set of scans, referred to as "3 mm resampled". Automated brain segmentation provided intracranial volume, total brain volume, and volumes for eight brain structures. Reliability and agreement of volume measurements were assessed using intraclass correlation coefficients (ICC) and Bland-Altman plots, respectively. Results: For all volumes, inter-scan reliability was higher for 3 mm vs. 3 mm resampled scans (mean observer ICC >0.92) compared to 2 mm vs. 3 mm scans (mean observer ICC >0.87). Bland-Altman plots revealed smaller mean volume differences between 3 mm and 3 mm resampled scans than between 2 mm and 3 mm scans. However, a proportional bias was found for deep gray matter volume for 3 mm vs. 3 mm resampled scans. Conclusion: Slice thickness influences brain volume measurements from neonatal MRI. Harmonization of imaging data acquired with different settings through image resampling improves reliability and agreement of brain volume measurements.