Quantifying Brain Myelin Water Fraction in a Guinea Pig Model of Spontaneous Intrauterine Growth Restriction

Background Intrauterine growth restriction (IUGR) is an obstetrical condition where a fetus has not achieved its genetic potential. A consequence of IUGR is a decrease in brain myelin content. Myelin water imaging (MWI) has been used to assess fetal myelin water fraction (MWF) and might potentially assess myelination changes associated with IUGR. Purpose To quantify and compare the MWF of non‐IUGR and IUGR fetal guinea pigs (GPs) in late gestation. Study Type Prospective animal model. Animal Model Dunkin‐Hartley GP model of spontaneous IUGR (mean ± SD: 60 ± 1.2 days gestation; 19 IUGR, 52 control). Field Strength/Sequence Eight spoiled gradient‐recalled (SPGR) gradient echo volumes (flip angles [ α ]: 2°–16°), and two sets of eight balanced steady‐state free precession (bSSFP) gradient echo volumes ( α : 8° – 64°), at 0° and 180° phase increments, at 3.0 T. Assessment MWF maps were generated for each fetal GP brain using multicomponent driven equilibrium single pulse observation of T 1 /T 2 (mcDESPOT). MWF was quantified in the fetal corpus callosum (CC), fornix (FOR), parasagittal white matter (PSW), and whole fetal brain. Statistical Tests Linear regression was performed between five fetal IUGR markers (body volume, body‐to‐pregnancy volume ratio, brain‐to‐liver volume ratio, brain‐to‐placenta volume ratio, and brain‐to‐body volume ratio) and MWF (coefficient of determination, R 2 ). A t ‐test with a linear mixed model compared the MWF of non‐IUGR and IUGR fetal GPs (significance was determined at α < 0.05). Results The MWF of the control fetuses are (mean ± SD): 0.23 ± 0.02 (CC), 0.31 ± 0.02 (FOR), 0.28 ± 0.02 (PSW), and 0.20 ± 0.01 (whole brain). The MWF of the IUGR fetuses are (mean ± SD): 0.19 ± 0.02 (CC), 0.27 ± 0.01 (FOR), 0.24 ± 0.03 (PSW), and 0.16 ± 0.01 (whole brain). Significant differences in MWF were found between the non‐IUGR and IUGR fetuses in every comparison. Data Conclusion The mean MWF of IUGR fetal GPs is significantly lower than non‐IUGR fetal GPs.