Figure 1.

T₂-weighted in utero MRI of human and rhesus macaque fetal brain. (A) T₂-weighted axial image of a human fetal brain at 23 weeks gestation. In (B), an enlarged view of the occipital and parietal region is shown. From the ventricular to pial surfaces, three tissue zones are apparent: germinal matrix (white arrows) is a dark zone proximal to the ventricular surface, the SP is a zone with higher intensity adjacent to the germinal matrix, and the CP (red arrows) is the superficial layer with the lowest intensity. For a G90 rhesus macaque fetus, T₂-weighted images (0.5 mm isotropic) sagittal (C), coronal (D), and axial (E–G) views are shown. Axial views of the occipital region at the positions of the red dashed lines in (C,D) are shown in (E–G). The three tissue zones apparent in human fetal MRI can also be observed in the fetal rhesus brain.