The Value Of MRI And CT In Diagnosis Of Neonatal Hypoxic-ischemic Encephalopathy

OBJECTIVE: By comparing and analyzing the difference of image grade of using MRI and CT in response to brain-injured levels caused by hypoxic-ischemic encephalopathy(HIE) in neonates to discuss the utility of using diffusion weighted MR imaging and diffusion tensor imaging in HIE.METHODS: We have synchronously examined 40 HIE neonates (Including 35 full term infants and 5 preterm infants) using MRI and CT in 11 days after birth, and compared with clinical grade. MRI was used to observe abnormal signal of T1WI and T2WI and make image grades. DWI was used to measurement and quantitative analysis apparent diffusion coefficient(ADC) values in brain lobes, and DTI was used to measurement Fractional Anisotropy(FA) values in brain white matter fibre bundles. CT was applied to observe CT values, low density range, morphological condition and hemorrhage condition.RESULTS: There was highly correlation among MRI image grade, old and new CT image grade to compare with clinical grade in 35 full term HIE infants (contingency coefficient was 0.725, 0.731, and 0.723, respectively). HIE clinical diagnosis was set as a standard; therefore, CT scan had 91.4% detection rate and false negative rate was 8.6%. However, MRI had 100% detection rate. In 26 slight HIE infants (grade I ) that image grade appear equivalent and the coincident rate was 26.9%( CT old image grade) 46.2%( CT new image grade) and 61.5%( MRI image grade). In 8 medium HIE infants (grade ) that MRI and CT scan showed 6 and 5 infants have equal image grade. In 34 HIE infants with grade I and II that MRI showed 2 cases have basal ganglia hemorrhage(occur rate was 5.9%) and CT scan showed 9 HIE infants have subarachnoid hemorrhage(in which 1 case combine with intraventricular hemorrhage, occur rate was 26.5%). One serious HIE infant (grade) that MRI and CT scan show complex hemorrhage. In all full term HIE infants that brain lobes ADC values from the higher value to the grassroots were bilateral parietal lobes, frontal lobes, occipital lobes and temporal lobes, respectively. The infants with grade and HIE group that bilateral parietal lobes ADC values were lower than the infants with grade I HIE group and have significantly different (P= 0.004). In addition, we detected that infants with grade II andlll HIE group have lower ADC value in 3~5d after birth than 1-2 days (P= 0.026) and lower than after 5 days, as well (P= 0.020). The FA values from the higher value to the grassroots were posterior limb of the internal capsule(0.467), splenium of corpus callosum(0.429), genu of corpus callosum(0.399), genu of the internal capsule(0.284) and anterior limb of the internal capsule (0.258), respectively. Five slight HIE preterm infants (grade ) had similar trend of brain lobes ADC value and myelination development FA value to the HIE term infants. Even there was no significantly different in the FA value between preterm infants and full term infants, the preterm infants had higherbrain lobes ADC value than full term infants especially on bilateral occipital lobes (P =0.049 ).CONCLUSION: Many image grage methods need further study to estimate their accuracy. When the pediatricians make HIE diagnosis who must first consider clinical manifestation then consulting with image manifestation and image grade. MRI is proved superior than CT scan in detecting brain hypoxic-ischemic injury, and MRI in detecting basal ganglia injury is earlier than CT scan. However, CT scan is more sensitive in detecting subarachnoid hemorrhage. In addition to T1WI and T2WI, we can use DWI and ADC value to quantitatively analyze HIE condition and use DTI and FA value to understand myelination development and pathological changes conditions.