Neurodevelopment assessment of newborns with combined fMRI and DTI

Functional Magnetic Resonance Imaging (fMRI) provides the location and regional extent of a task correlated activation in the brain. Recently we have demonstrated, that fMRI of passive sensory tasks (visual, auditory, motor) can be successfully used to map cortical activation in the newborn brain. However the interpretation of the functional response in the immature brain is difficult, as the blood oxygen level dependent (BOLD) physiological signal and location of the activation is quite different compared to adult fMRI responses of similar tasks. We expect, that the major reason for these differences are primarily caused by the immature myelination of the white matter tracts at this age. Diffusion tensor imaging (DTI) can be used to measure the white matter tract development in the newborn brain. The purpose of this paper is to report how to obtain and to combine fMRI and DTI data processing to enhance functional brain mapping in newborns. We obtained simultaneous fMRI and DTI data of 18 newborns, post-conceptional age (gestational age at study) between 34-week and 52-week, which were referred for clinical indicated MRI. 16 out of 18 subjects have been successfully investigated with combined fMRI and DTI and functional activation could be obtained. Fiber tracking was successfully in the visual and auditory cortex, but proofed difficult in the motor-cortex. The additional tract information supported the functional findings and the interpretation in the immature brain. The novel functional imaging in newborn is challenging because of the yet unknown physiological response and location of activation in the newborn brain. Therefore one need additional evidence that the functional findings are valid in the context of structural development. The maturation of myelination is an essential information to compare and to interpret fMRI in newborns. We conclude that the proposed method of combined fMRI and DTI, derived from adult neuroimaging, will be most relevant to understand the physiological response and thus the neurodevelopment of the newborn brain.