Advanced fetal MRI

Abstract

Abstract Magnetic resonance imaging (MRI) is widely used during the fetal period when fetal abnormalities are identified, or diagnostic doubts remain after prenatal ultrasonography. In vivo fetal MRI can improve the diagnostic accuracy for fetal brain abnormalities, leading to better prenatal counseling and clinical management. MRI of the fetus in utero is extremely challenging due to nonpredictable fetal motion, small brain size, and low tissue contrast. Especially, fetal motion disrupts the spatial encoding needed for 3D image acquisition. Therefore, fast structural fetal MRI is typically performed using single-shot fast spin echo T2-weighted sequences and inter-slice motion correction methods have been developed. In vivo diffusion-weighted and functional MRI are also used after fetal motion correction for quantitative microstructural evaluation and examination of structural and functional connectivity development in the fetal brain. Recently, advanced fetal MRI analysis techniques have been proposed, enabling the quantitative assessment of brain volumetric growth; cortical surface areal growth and folding; global sulcal folding pattern; tissue microstructure; white matter structural connectivity; and functional connectivity and networks in healthy fetuses and fetuses with developmental brain disorders. Prior in vivo fetal MRI studies show great potential to not only help us better understand normal and abnormal brain development but also improve the management of high-risk pregnancies and the diagnosis and treatment of congenital anomalies. For future work, it is necessary to improve both spatial resolution and contrast of fetal MRI, to decrease its sensitivity to motion, reduce the total acquisition time, and to develop more advanced image processing and analysis technologies.