ARRS 2022 Abstracts


2054. Fetal DTI Demonstrates Microstructural Changes in the Emerging White Matter
Authors * Denotes Presenting Author
  1. Fedel Machado Rivas; Boston Children's Hospital; Harvard Medical School
  2. Camilo Calixto *; Bogota Hospital
  3. Sebastian Gallo Bernal; Harvard Medical School; Massachusetts General Hospital
  4. Clemente Velasco-Annis; Boston Children's Hospital
  5. Simon Warfield; Boston Children's Hospital; Harvard Medical School
  6. Ali Gholipour; Boston Children's Hospital; Harvard Medical School
  7. Camilo Jaimes Cobos; Boston Children's Hospital; Harvard Medical School
Cytoarchitectonic changes and myelination reshape the macro and microstructure of the fetal white matter. We aim to characterize spatiotemporal changes in fractional anisotropy (FA) and mean diffusivity (MD) in the late second and third trimester.

Materials and Methods:
We acquired motion corrected fetal DTI (124 MRIs) and a spatiotemporal atlas was created using a non-rigid diffeomorphic registration. A total of 15 templates were generated, one per week of development (range: 24-38w). For all templates, we placed ROIs in the corpus callosum (CC), external capsule (EC), and posterior limb of the internal capsule (PLIC). For third trimester templates, we placed ROIs in the white matter (WM) of each lobe (frontal, parietal, occipital, temporal), spanning the subcortical and deep WM. For second trimester templates, we placed ROIs in the subplate and intermediate zone of each lobe. Segmentations were reviewed by a neuroradiologist. A regression analysis with linear and quadratic terms (if non-linear) were used to model the relationship between FA and MD, with GA.

In the CC, FA decreased with GA (P=.038). MD showed an increase with GA in the second trimester (P=.002) and decrease in the third (P=.001). The EC and PLIC showed significant increase in FA and a decrease in MD with GA (P<.001). For all lobes, the FA in the WM reached a nadir at in the early third trimester and subsequently showed a significant increase (P<.001). The MD showed a peak in the early Third trimester, followed by a significant decrease with GA (P<.001). Comparing the WM by lobes (GA adjusted), the mean FA in the temporal lobe was higher (P<.001) and the mean MD in the occipital lobe was lower (P<.001). Analysis of the SP in the second trimester showed that the FA was significantly lower (P<.001) than in the intermediate zone; the MD was higher in the subplate, but the difference was not significant (P=.196). Lobar analysis showed that the frontal lobe had the highest subplate FA, IZ FA, and lowest IZ MD.

Fetal DTI shows differences in WM microstructure as a function of transient WM zones and large WM tracts.