Allen Mouse Brain CCFv3 segmentations transformed to P21 population-averaged serial two-photon tomography data (v1)

This dataset contains two segmentation volumes for the postnatal day (P) 21 mouse brain. These correspond to the adult Allen Mouse Brain atlas Common Coordinate Framework version 3 (Allen CCFv3) 2017 and 2022 segmentations. This P21 segmentation dataset, together with a corresponding serial two-photon tomography (STPT) reference dataset ([Carey et al., 2024](https://doi.org/10.25493/2FMJ-152)), constitute the Developing Mouse Brain Atlas P21 (DeMBA P21). The DeMBA P21 is part of a series of atlases for the developing mouse brain, with STPT templates available from postnatal day 4, 7, 14, 21, 28, and 56 and synthetic, interpolated templates for all days in between. The DeMBA segmentations were created by transforming the Allen CCFv3 segmentations to fit the respective DeMBA template. The result is a developmental mouse brain atlas that is fully compatible with the Allen Mouse Reference Atlas Ontology, which can be used for spatial registration and analysis of data from postnatal mouse brains.