The study was approved by the Medical Ethics Review Committee of our institute and the relevant informed consent was obtained in accordance with the Helsinki Declaration. 30 newborns with hyperbilirubinemia were enrolled as the hyperbilirubinemia group and 10 normal newborns as the control group from February 2019 to February 2020. They were assessed by the bilirubin-induced neurological dysfunction (BIND) score, brainstem auditory evoked potential (BAEP) and amplitude integrated electroencephalogram (aEEG) tests. The total serum bilirubin (TSB), gender, gestational age, and the days from birth to MRI examination were also recorded.
30 newborns of the hyperbilirubinemia group were enrolled according to the following criteria: 1) full-term newborns whose gestational ages range from 37 to 42 weeks; 2) TSB > 221 μmol/L; 3) with jaundice as the chief complaint. The exclusion criteria included: 1) severe genetic/metabolic diseases, neonatal asphyxia, severe infection, acidosis, hypoglycemia, congenital abnormality or organic pathological changes of CNS; 2) liver function abnormality, biliary atresia or drug-induced bilirubin increase; 3) gestational age < 37 weeks.
The hyperbilirubinemia group was divided into two subgroups by BIND score: 1) non-BIND group (BIND score = 0, without neurologic dysfunction): 17 cases, include 8 females and 9 males; 2) BIND group, (BIND score ≥1, with neurologic dysfunction)：13 cases, including 6 females and 7 males.
10 healthy newborns of control group were selected, including 5 males and 5 females, according to the following criteria included:1) with no jaundice; 2) full-term newborns whose gestational ages range from 37 to 42 weeks; 3) BIND score was 0. The exclusion criteria included: 1) there were neurological symptoms or signs, a history of dystocia, ischemic hypoxic encephalopathy, intracranial infection, hypoglycemia, chromosomal disease, and congenital nervous system disease; 2) there were abnormalities was found in brain MRI; 3) gestational age < 37 weeks.
All newborns underwent MRI examinations. A 3 T MR scanner (MAGNETOM Verio, SIEMENS Healthcare, Erlangen, Germany) with an 8-channel head-neck combined coil was used in the present study. All the newborns were sedated by enema with 5% chloral hydrate and the dose was adjusted by body weight (0.5ml / kg). MRI was performed within 30 minutes after sedation.
Conventional MRI sequences, DTI and ASL were performed with following parameters. 1) Axial T1WI: TR 350ms, TE 8.4ms, slice number 19, slice thickness 4.5 mm, intersection gap 1.35 mm, field of view (FOV) 220 mm × 220 mm, voxel size 0.9 mm × 0.9 mm×4.5 mm, scanning time 2min 39s; 2）Axial T2WI: TR 4950ms, TE 101ms, slice number 19, slice thickness 4.5 mm, intersection gap 1.35 mm, field of view (FOV) 230 mm × 230 mm, voxel size 1.0 mm × 0.7 mm×4.5 mm，scanning time 1min 14s; 3）Axial T2-flair: TR 8500ms, TE 94ms, scanning number 19, slice thickness 4.5 mm, intersection gap 1.35 mm, field of view (FOV) 230 mm × 230 mm, voxel size 1.3 mm × 0.9 mm×4.5 mm, scanning time 2min 39s; 4）DTI: TR 8900ms, TE 84ms, slice number 35, slice thickness 3 mm without intersection gap, FOV 220 mm × 220 mm, number of excitations (NEX) 2, matrix 128×128, b value 1000s /mm2, with 20 gradient directions, voxel size 1.7 mm × 1.7 mm×3.0 mm, scanning time 6min 42s; 5）ASL: TR 4500ms, TE 12ms, slice thickness 2 mm, intersection gap 0.5 mm, slice number 4, flip angle 90 °, voxel size 3.1 mm × 3.1 mm×2.0 mm scanning time 7min 50s. The ASL was acquired to cover globus pallidus.
Data measurement of MRI
Two experienced attending radiologists, blinded to the clinical information, separately reviewed and measured the data of MR images on workstation processing. The regions of interest (ROIs) were manually defined on the layer with the largest area of globus pallidus in axial T1WI, DTI and ASL images, and three symmetrical ROIs were located on both sides of the globus pallidus respectively from anteromedial to posterolateral, as showed in Figure 1. The area of the ROI was between 20mm2-30mm2. The signal values of each ROI on T1WI, DTI and ASL image, were recorded. The mean values of these parameters from six ROIs were calculated, and the final mean value was calculated by the mean value from the two radiologists.
The statistical analysis was performed by Statistical Product and Service Software (SPSS ver. 26.0). The data of T1WI, DTI parameters and rCBF were measured by two radiologists and averaged. The normality of data was tested by Shapiro-Wilk. The gender, gestational age, and days from birth to MRI examination differences among groups were analyzed by chi-square test and analysis of variance (ANOVA) respectively. The parameters values of globus pallidus among groups were analyzed by ANOVA. A p-value less than 0.05 was considered statistically significant and each p-value was adjusted using Bonferroni correction. The correlation between the parameters (FA, RA, VR, ADC, rCBF) and serum bilirubin was evaluated by the Pearson correlation coefficient. To evaluate the diagnostic accuracy of T1WI and DTI, the receiver operating characteristic (ROC) analysis was performed and the area under the curve (AUC) was calculated by MedCalc (MedCalc statistical software, ver.19.7).