Ex vivo fetal brain MRI: Recent advances, challenges, and future directions.

During early development, the fetal brain undergoes dynamic morphological changes. These changes result from neurogenic events, such as neuronal proliferation, migration, axonal elongation, retraction, and myelination. The duration and intensity of these events vary across species. Comparative assessments of these neurogenic events give us insight into evolutionary changes and the complexity of human brain development. Recent advances in magnetic resonance imaging (MRI), especially MRI, permit characterizing and comparing fetal brain development across species. Comparative MRI studies support the detection of species-specific differences that occur during early brain development. In this review, we provide a comprehensive overview of MRI studies that characterize early brain development in humans, monkeys, cats, as well as rats/mice. Finally, we discuss the current advantages and limitations of fetal brain MRI.