A 3D Atlas of MR Diffusion Parameters in the Preterm Neonatal Brain

Every year fifteen million infants are born prematurely in the whole world. The maturation of the brain occurs mainly during the third trimester (24-40 weeks of gestational age). Therefore extremely preterm infants (infants born before 25 weeks of gestational age) are vulnerable to brain injuries (perinatal asphyxia and perinatal stroke being the most common) and are more likely to develop behavioral problems, learning disabilities or functional consequences later in life. Magnetic resonance imaging (MRI) has good spatial resolution and soft-tissue contrast, providing a highly detailed anatomical image of the developing brain. Additionaly, Diffusion Tensor Imaging (DTI) allows visualization and quantification of the micro-architecture of brain structures in vivo. Abnormal values of diffusion tensor measures in preterm infants can indicate abnormal brain development caused by e.g. haemorrhage. To use MRI and DTI effectively in clinical practice, it is necessary to have an atlas of the neonatal brain, consisting of a structural MRI template segmented in anatomically relevant regions and providing reference values for diffusion parameters in healthy preterms (showing normal development). Most existing atlases either include only a structural MRI template, without DTI information, or, when they do include a DTI atlas, they are based on term infants rather than preterm infants. Therefore, we conclude that there is no atlas that can be used as a reference for the diffusion parameters in the preterm developing brain. We constructed an atlas consiting of a structural template and a diffusion template encoding mean and standard deviation of DTI parameters in a population of healthy preterms. The method to construct such a template is explained. For the construction of the structural template we performed intersubject pair-wise image registration and for the construction of the diffusion template intra-subject registration was additionally used. Image registration depends on several settings and parameters. Those parameters were optimized to minimize registration errors. Manual segmentation is used to segment several areas of the brain, to allow for region-based analysis. In addition, we present an example of how the template can be used in clinical practice. The parameter optimization was performed using 9 preterm infants without evidence of focal lesions on conventional magnetic resonance imaging. The template is based on 19 preterm infants without evident brain abnormalities. An independent set of 16 premature born infants (12 with evident abnormalities and 4 without evident abnormalities) is used for evaluation. Based on the results, we conclude that the proposed interactive atlas of diffusion MR parameters may aid in early recognition of subjects with a high risk of abnormal development.BMEBioMechanical EngineeringMechanical, Maritime and Materials Engineerin