MRI-based spatio-temporal atlas of ganglionic eminence

Objective: Fetal brain magnetic resonance imaging (MRI) provides insights into the architecture of the human brain. Recently, an increasing interest has been posed on transient brain structures, such as the ganglionic eminence (GE), to better understand potential derailments or anomalies in neurodevelopment. In this work, we define a spatio-temporal atlas of the GE from 19 to 36 gestational weeks (GW) in a 0.5-mm isotropic resolution. Materials and methods: We extended the T2-weighted developing Human Connectome Project atlas with 19 and 20 GW and generated GE label maps spanning 19–36 GW. The GE label maps were generated via an averaging ensemble strategy of the segmentations performed by three expert neuroradiologists. Results: The segmentations conducted by the experts achieved 0.91 ± 0.06 Dice similarity coefficient throughout the whole range of GW, indicating a strong agreement in this task. The GE reached its maximum volume expansion at around 21 GW, followed by a pronounced reduction throughout pregnancy (R2 = 0.98, ranged 40‒500 mm3), highlighting an inverse relationship to the whole brain volume and cortical gray matter. This is accompanied by an increased number of small and fragmented components, correlating with known dynamics of GE migration toward target structures. Conclusion: The proposed spatio-temporal GE MRI atlas supports the monitoring during pregnancy of this fascinating brain structure. It may aid in better understanding prodromic signs of potential future clinical conditions attributable to GE alterations. Moreover, it could be used as a repository of knowledge to develop innovative atlas-based deep learning models for biometric, volumetric, and shape analysis. Relevance statement: The spatio-temporal fetal MRI atlas of the GE allows researchers to study its evolution and potential future clinical conditions attributable to GE alterations in pregnancy. The GE reached its maximum volume expansion around 21 GW, followed by a pronounced reduction throughout the pregnancy. Key Points: The development of GE is a resource for monitoring pregnancy. We propose a spatio-temporal GE MRI atlas from 19 to 36 weeks of gestation. The GE reached its maximum expansion at around 21 weeks of gestation, followed by a progressive decline throughout pregnancy.