The Application Of Conventional MRI And ASL Perfusion-Weighted Imaging In Neonatal Hypoxic Ischemic Encephalopathy

Purposel.To analyze the appearance of neonatal hypoxic ischemic encephalopathy in conventional MRI sequences with T1WI, T2WI, T2FLAIR and DWI, and discuss the value of each sequence in different type of brain injury.2. To study the change of relative cerebral blood flow (rCBF) at different positions in HIE neonates and evaluate the influence of birth age to rCBF by measuring rCBF of full-term HIE neonates with arterial spin-labeled perfusion weighted imaging, and explore the pathogenesis of HIE.PART I The application of conventional MRI sequences in neonatal hypoxic ischemic encephalopathyMaterials and Methods1. Subjects56neonatal cases which were clinically diagnosed HIE (30cases of full-term and26cases of premature) were carried out conventional MRI examination from September2011to October2013. MRI performance of48cases (male26, female22) diagnosed HIE by MRI were analyzed.2. MR scanning MRI examination was performed by using the Siemens3.0T MRI scanner. Axial images were applied in all sequences. Scan sequences included:T1-and T2-weighted imaging, T2fluid-attenuated inversion recovery (FLAIR) sequence and diffusion weighted imaging (DWI).3. Image analysisThe features of morphology and signal change in each MRI sequence on all HIE neonates were observed and analyzed by one high qualification doctor using blind method independently. Other cerebral diseases were rule out. According to the positions and characteristics of abnormal signal, HIE brain injuries were divided into the following seven types:basal ganglia/thalamic damage, deep white matter lesions, cortex and subcortical white matter lesions, posterior limb of internal capsule injury, corpus callosum injury, cerebral hemorrhage and cerebromalacia.4. Data analysisNumbers of lesion in different sequence of various types of brain damage were counted respectively. The number of all the lesions were considered as the total number. The display rate of each sequence to different brain injury types was calculated, and the advantages of each sequence showing different types of brain damage were compared.1case of cerebromalacia was not included in data analysis because the MRI appearance was abnormal on all sequences.Result1. The number of cases with different type:7cases of basal ganglia/thalamic injury,13of deep white matter lesions,17of cortical and subcortical white matter damage,5of posterior limb of internal capsule injury,6cases of corpus callosum injury,6of cerebral hemorrhage,1case of cerebromalacia were observed. Some cases suffered from various types of brain damage.2.316lesions were detected with all MRI sequences. T1WI was better for basal ganglia/thalamic damage, cortex and subcortical white matter damage and cerebral hemorrhage with display rate of44.44%,38.53%and35.29%respectively. T2WI was better for deep white matter lesions with display rate of28.76%, and shown the same display rate as T1WI on brain hemorrhage. T2FLAIR was the best to detect deep white matter lesions with a display rate of33.33%, and it was sensitive to show cortical and subcortical white matter lesions with a display rate of29.36%. DWI displayed damage on corpus callosum and posterior limb of internal capsule with display rate of54.55%and50.00%respectively, which was better than other sequences.ConclusionT1WI, T2WI, T2FLAIR and DWI sequence displays different advantage for various type of HIE respectively. Conventional MRI sequences are very important for diagnosis of neonatal HIE.PART II Application of MRI ASL perfusion-weighted imaging in the diagnosis of full-term neonatal hypoxic ischemic encephalopathy1. Subjects1.1Experimental group:46HIE full-term neonates with HIE diagnosed clinically were carried out MRI from October2011to September2013，including22males and24females,whose birth age were1to15days, an average of8.7days. The average birth weight was3.3kg. The gestational age was37to41weeks, an average of39.6weeks.1.2Control group:13cases of full-term neonates who had no history of hypoxic ischemic and diagnosed clinically as physiological hyperbilirubinemia were incorporated in control group, including7male and6female. The average birth weight was3.1kg. The gestational age was37to41weeks, an average of38.5weeks. Birth age was1to15days, an average of8.3days.2. MR scaningMRI ASL was performed with the Siemens3.0T MRI scanner. Children were supine, Cotton ball was plugged into neonates’ ears for hearing protection. Head fixed with craniocerebral foam model when checking, and be sure to keep warm. Injecting5% chloral hydrate (50mg/kg) through the stomach tube for composed before MRI scanning15to20minutes. Inspection was operated after sleeping. MRI conventional sequences were carried out, followed by ASL perfusion scanning. The ASL scan range was from thalamus to the superior border of lateral ventricle. Total scanning time was5minutes and45seconds.3. Image and data analysis3.1rCBF pseudo-color image was acquired automaticly after collecting and processing data at the end of ASL scanning. The color of rCBF map was adjusted manually on the workstation with color difference stands for the perfusion variance.In this study,low perfusion area on rCBF map was blue, middle perfusion area was green and high perfusion was red color. Region of interest were chosen bilaterally at frontal white matter (superior border on the lateral ventricle), the head of caudate nucleus, thalamus and lentiform nucleus. Region of interest on rCBF map was acquired by reference of ASL original images. The same size and location at bilateral region of interest was made as far as possible by using the mirror image method.3.2rCBF values of region of interest were measured bilateral for three times, then the six numbers added and the average rCBF value was acquired. The difference of rCBF value between experimental and control group was analysed.3.3According to birth age, experimental group was divided into three subgroups with1to3days,4to7days and8to15days to analyze the influence of birth age to rCBF value.4. Statistical analysisrCBF value was expressed by x±s. SPSS16.0statistical software was used to analyze the difference of rCBF value between HIE group and control group by using two independent sample t test and analyze the influence of birth age to rCBF value by Adopt One-Way ANOVA and SNK-q statistical methods. P<0.05was considered as the significant difference statistically.Result1. rCBF value of the thalamus and lentiform nucleus in experimental group is obviously higher than that of the control group (P=0.01). rCBF value of frontal white matter in experimental group was lower than that of the control group (P=0.02). There was no significant difference in rCBF value of head of caudate nucleus between the two groups (P=0.53).2. The rCBF value increased significantly in HIE subgroup of1to3days than that of4to7days and8to15days, with a statistically significant difference (P=0.01, P=0.01, P=0.03,P=0.01)Conclusion1. The rCBF value of thalamus and lentiform nucleus are increased and rCBF value of the frontal white matter decreased in experimental group than that in control group. ASL could provide useful information for the diagnosis of HIE and can evaluate cerebral blood flow perfusion quantitatively.2. rCBF value is increased significantly in HIE subgroup of1to3days than that of4to7days and8to13days subgroups, which could reflect the evolution process of the CBF, may help to expound the pathogenesis of HIE. SummaryConventional MRI sequences and ASL technology are noninvasive methods for neonatal HIE. Conventional sequences could display the location and extent of HIE lesions clearly, ASL perfusion imaging can measure rCBF value quantitatively. The combination of two technologies is better to evaluate the severity of hypoxic-ischemic injury and could provide valuable information for clinical treatment.