Feasibility of MRI Quantification of Myelin Water Fraction in the Fetal Guinea Pig Brain.

ABSTRACT

BACKGROUND: Fetal myelination assessment is important for understanding neurodevelopment and neurodegeneration. Myelin water imaging (MWI) quantifies myelin water fraction (MWF), a validated marker for myelin content, and has been used to assess brain myelin in children and neonates. PURPOSE: To demonstrate that MWI can quantify MWF in fetal guinea pigs (GPs). STUDY TYPE Animal model. ANIMAL MODEL Nine pregnant, Dunkin-Hartley GPs with 31 fetuses (mean ± standard deviation = 60 ± 1.5 days gestation). FIELD STRENGTH/SEQUENCE 3D spoiled gradient echo and balanced steady-state free precession sequences at 3.0 T. ASSESSMENT MWF maps were reconstructed for maternal and fetal GP brains using the multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) approach. Myelin basic protein (MBP) stain provided histological validation of the MWF. Regions of interest were placed in the maternal corpus callosum (CC), maternal fornix (FOR), fetal CC, and fetal FOR in MWF maps and MBP stains. STATISTICAL TESTS Linear regression between MWF and MBP stain intensity (SI) of all four regions (coefficient of determination, R2 ). A paired t-test compared the MWF of maternal and mean fetal CC, MBP SI of maternal and mean fetal CC, MWF of maternal and mean fetal FOR, MBP SI of maternal and mean fetal FOR. A paired t-test with a linear mixed model compared the MWF of fetal CC and fetal FOR, and MBP SI of fetal CC and fetal FOR. A  P value < 0.0083 was considered statistically significant. RESULTS: The mean MWF of the analyzed regions are as follows (mean ± standard deviation) 0.338 + 0.016 (maternal CC), 0.340 ± 0.017 (maternal FOR), 0.214 ± 0.016 (fetal CC), and 0.305 ± 0.025 (fetal FOR). MWF correlated with MBP SI in all regions (R2  = 0.81). Significant differences were found between MWF and MBP SI of maternal and fetal CC, and MWF and MBP SI of fetal CC and fetal FOR. DATA CONCLUSION: This study demonstrated the feasibility of MWI in assessing fetal brain myelin content. EVIDENCE LEVEL 2 Technical Efficacy Stage 1.