Shape and curvedness analysis of brain morphology using human fetal magnetic resonance images in utero

The 3-D morphological change has gained increasing significance in recent investigations on human fetal brains. This study uses a pair of new indices, the shape index (SI) and curvedness index (CVD), to quantify 3-D morphological changes in developing brains from 22 to 33 weeks of gestation. The SI was used to automatically locate the gyral nodes and sulcal pits, and the CVD was used to measure the degree of deviation of cortical shapes from a flat plane. The CVD values of classified regions were compared with two traditional biomarkers: cerebral volume and cortical surface area. Because the fetal brains dramatically deform with age, the age effect was controlled during the comparison between morphological changes and volume and surface area. The results show that cerebral volume, the cortical surface area, and the CVD values of gyral nodes and sulcal pits increased with gestational age. However, with age controlled, the CVD values of gyral nodes and sulcal pits did not correlate with cerebral volume, but the CVD of gyral nodes increased slightly with the cortical surface area. These findings suggest that the SI, in conjunction with the CVD, provides developmental information distinct from the brain volumetry. This approach provides additional insight into 3-D cortical morphology in the assessment of fetal brain development.