Demonstrating Microstructural Environment of the Brain in Neonatal Bilirubin Encephalopathy with Diffusion Kurtosis Imaging

Abstract

Background: Magnetic resonance spectroscopy (MRS) of infants with bilirubin encephalopathy shows abnormal changes in the metabolite concentrations in various parts of the brain. Diffusional kurtosis imaging (DKI) is an extension of diffusion tensor imaging (DTI), which includes non-Gaussian diffusion effects, thereby allowing more comprehensive characterization of microstructural changes in pathological analysis. Objectives: Our study retrospectively analyzed DKI data to determine whether the DKI profiles of newborns with bilirubin encephalopathy can evaluate microstructural changes and illustrate related mechanisms. This study also verified whether DKI parametrics can serve as an in vivo marker for neonatal bilirubin encephalopathy. Patients and Methods: A total of 17 patients with neonatal bilirubin encephalopathy and 21 healthy, age-matched control newborns were included in this study. Conventional MRI and DKI were performed for all patients and controls. The mean kurtosis (MK), axial kurtosis (AK), radial kurtosis (RK), fractional anisotropy (FA), and mean diffusion (MD) were obtained from the voxels of interest (VOIs) within the bilateral globus pallidus, putamen, and thalamus. Results: Compared with the control group, the MK, AK, RK, and FA in all VOIs were significantly decreased in neonatal bilirubin encephalopathy, whereas MD increased. Among the kurtosis tensor parameters, RK had the largest change between groups (reduced 15.2% in globus pallidus, 8.8% in putamen and 9.0% in thalamus, respectively). Between neonatal bilirubin encephalopathy and control newborns, the values of MK, AK, RK, and MD more markedly varied in the globus pallidus than in the putamen and thalamus. However, FA more obviously changed in the thalamus than in the globus pallidus and putamen. Conclusions: DKI detects significant microstructural changes, which are consistent with known patterns of neurological damage in neonatal bilirubin encephalopathy. DKI parametrics can comprehensively evaluate microstructural changes and may serve as an in vivo marker for neonatal bilirubin encephalopathy.