Fundamentals of fetal brain MRI: indications, technique, and normal anatomy

Magnetic resonance imaging (MRI) evaluation of the fetal central nervous system (CNS) is a well-established imaging modality that improves detection of fetal neuro anomalies. The utilization of rapid imaging acquisition sequences allows for the high-resolution evaluation of the developing fetus with decreased impact from fetal motion. MRI is often performed after a prenatal screening ultrasound (US) demonstrates an abnormality or if there are known risk factors. The most common neurological indications for fetal MRI include ventriculomegaly, absent cavum septum pellucidum, and enlarged cisterna magna followed by hemorrhagic lesions and intracranial cysts. Knowledge of normal fetal anatomy and development of CNS structures is key for accurate interpretation of fetal brain MRI.