Diffusion Tensor Imaging In Neonatal Hypoxic-ischemic Encephalopathy, Clinical Correlation Study

PartⅠScan parameters of diffusion tensor imaging for neonatal and infantile brainPurpose:To search the proper scan parameters of diffusion tensor imaging(DTI) for neonatal and infantile brain.Materials and Methods:36 term neonates and infants were investigated by DTI with different scan parameters.Their perinatal medical records and nervous system examinations were nothing remarkable.Alterable scan parameters were b value,the number of diffusion sensitive gradient direction and slice thickness/gap.The image quality was divided into three levels.The images of the first and second level were acceptable,the images of the third level were not acceptable. Proper scan parameters were discussed according to the image quality.Results:14 parameter combinations were acceptable.The quality of images acquired by using low b value was higher than that of images acquired by using high b value.The more the number of diffusion sensitive,the higher the image quality was.The thicker the thickness/gap was,the higher the image quality was.Among these three parameters, thickness/gap had the most influence on image quality(P＜0.01),number of diffusion sensitive took second place(P＜0.01),b value had the least influence on image quality(P＞0.05).Conelusion:Image quality is determined by scan parameters.With the precondition of acceptable image quality,we should adjust scan parameters according to different clinical instance.The optimal scan parameters of DTI for neonatal and infantile brain in this study are b=1000 s/mm~2,12 diffusion sensitive gradient directions and thickness 4mm/gap 1mm.PartⅡDiffusion tensor imaging for normal neonatal and infantile brainPurpose:To discuss the changes of apparent diffusion coefficient(ADC)/fractional anisotropy(FA) values in developing brain of normal neonates and infants and the diversity of ADC/FA values in various brain regions,establish normal parameters for follow-up study.Materials and Methods:97 term neonates and infants were investigated by diffusion weighted imaging(DWI) and DTI.Their perinatal medical records and nervous system examinations were nothing remarkable.They were divided into 7 groups according to the age.The first group was from birth to 28 days, the second group was from 29 days to 3 months,the third group was from 3 months to 6 months,the fourth group was from 6 months to 12 months,the fifth group was from 12 months to 18 months,the sixth group was from 18 months to 24 months,the seventh group was from 24 months to 36 months.ADC/FA values in bilateral white matter of cerebellar hemisphere(WMCH),posterior brain stem(PBS),anterior limb of internal capsule(ALIC),posterior limb of internal capsule(PLIC),genu of corpus callosum(Genu),splenium of corpus callosum(Splenium),head of caudate nucleus(HCN),lentiform nucleus(LN),ventrolateral nuclei of the thalamus(VLN), frontal white matter(FWM),parietal white matter(PWM),central centrum semiovale(CCSO) were analyzed.Results:ADC/FA values in the same regions of interest(ROI) had no statistic difference between left and right hemisphere and between male and female(P＞0.05).Accompanied with the increase of age,ADC values in various ROIs decreased(P＜0.01),while FA values in ROIs except LN increased(P＜0.01).In the first 3 months after birth,the change rate of ADC/FA values was the fastest.The decreasing rate of ADC values was faster than the increasing rate of FA values.In the same age group,ADC/FA values and their change range in various regions were different.Conclusion:ADC/FA values in the same brain regions of neonatal and infantile brain have no statistic difference between left and right hemisphere and between male and female.Accompanied with the increase of age, ADC values in various brain regions decrease while FA values increase except LN. The change of ADC/FA values in the first 3 months after birth is the fastest.The change range of ADC/FA values in different brain regions is different and ADC/FA values in various brain regions are different,it reflects the myelination time,white matter fiber arrangement and the features of myelin sheath.ADC/FA values can analyze myelination process quantitatively and evaluate brain white matter development.PartⅢDiffusion tensor imaging in neonatal hypoxic-ischemic encephalopathy Purpose:To discuss the role of ADC/FA value in brain WM injury assessment and prognosis evaluation on neonates born at term with hypoxic-ischemic encephalopathy(HIE).Materials and Methods:44 term neonates diagnosed with HIE and 16 controls were investigated with conventional magnetic resonance imaging(MRI),DWI and DTI.They were divided into≤7d group and＞7d group according to the scan time.ADC/FA values in bilateral WMCH,PBS,ALIC,PLIC, Genu,Splenium,HCN,LN,VLN,FWM,PWM,CCSO and neonatal behavioral neurological assessment(NBNA) scores were analyzed.Results:Of the 44 cases,12 were mild HIE,15 were moderate HIE,17 were severe HIE.On convention MRI,4 cases were normal,35 cases had cortex and subcortex lesions,26 cases had deep white matter lesions,17 cases had basal ganglia,thalamus and internal capsule lesions, 13 cases had ventricles,subarachnoid and subdural space lesions.For≤7d group, ADC values in various ROIs decreased accompanied with the severity of HIE.ADC values in PLIC,Genu,Splenium,FWM,PWM,CCSO of severe HIE were lower(P＜0.05),ADC values in PLIC of moderate HIE were lower(P＜0.05),there was no statistic difference between mild HIE group and controls(P＞0.05).For＞7d group, ADC values in all of the ROIs had no statistic difference between HIE group and controls(P＞0.05).FA values in cerebral WM regions decreased accompanied with the severity of HIE.For≤7d group,FA values in PLIC,Splenium,FWM,PWM,CCSO, VLN of moderate/severe HIE were lower(P＜0.05),there was no statistic difference between mild HIE group and controls(P＞0.05).For＞7d group,FA values in above ROIs of moderate/severe HIE were still lower(P＜0.05),FA values in Genu of severe HIE and PLIC,Splenium of mild HIE were lower too(P＜0.05),among them 4 mild HIE cases had normal conventional MRI appearance.The diagnostic accuracy of ADC values in several WM regions of＞7d group were lower than that of≤7d group, its ability of finding WM lesions was not as good as conventional MRI.While the diagnostic accuracy of FA values of＞7d group were higher than that of≤7d group,its ability of finding WM lesions was better than ADC value and conventional MRI, especially in mild and moderate HIE group.More severe the lesion degree,more lower the NBNA scores(P＜0.01).FA values in PLIC,Splenium,FWM,PWM,CCSO, VLN were correlative with NBNA scores(P＜0.05).The diagnostic accuracy of FA value in PLIC and the correlation between FA value in PLIC and NBNA scores were the highest.When FA value in PLIC≥0.488,the patients had good prognosis,the sensitivity of prognosis prediction was 88%,specificity was 65%,Youden index was 0.53.Conclusion:Relationship exists between ADC/FA value in the brain of HIE neonates and the stage of disease,the site and severity of lesion and the time of imaging examination.FA values can reflect the brain WM injury of HIE neonates quantitatively,its diagnostic veracity is better than ADC value and conventional MRI during the subacute phase of HIE,especially for mild and moderate HIE neonates.FA values can evaluate the prognosis of HIE neonates quantitatively.The diagnostic veracity of FA values in PLIC is the highest.The correlation between FA value in PLIC and NBNA scores is the highest.When FA value in PLIC≥0.488,patients maybe have good prognosis.PartⅣDiffusion tensor imaging on infants born at term with hypoxic-ischemic encephalopathyPurpose:To evaluate the role of ADC/FA value in brain myelination assessment and prognosis evaluation on infants born at term with HIE.Materials and Methods:37 infants,18 months to 3 years old,who were born at term,diagnosed with HIE were investigated with conventional MRI,DWI and DTI.ADC/FA values in bilateral WMCH,PBS,ALIC,PLIC,Genu,Splenium,HCN,LN,VLN,FWM,PWM,CCSO were measured.Clinical references,developmental quotient(DQ) were also used as a basis of comparison to a group of controls of the same age and gender distribution. Results:Of the 37 cases,9 were mild HIE,16 were moderate HIE,12 were severe HIE.Correlation existed between DQ and the degree of HIE(P＜0.01).On conventional MRI,4 cases were normal,3 cases had widening of sulci only,21 cases had external hydrocephalus,17 cases had enlargement of ventricles,15 cases had abnormal myelination,21 cases had decreased white matter,17 cases had periventricular leukomalacia,5 cases had dysplasia of corpus callosum,2 cases had brain atrophy.ADC values in various ROIs except the WMCH and PBS increased accompanied with the severity of HIE.Compared with control group,ADC values in ALIC,PLIC,Genu,Splenium,HCN,VLN,FWM,PWM,CCSO of the severe HIE group had statistic difference(P＜0.05).ADC values in ALIC,PLIC,Genu,Splenium, VLN,PWM,CCSO of the moderate HIE group had statistic difference(P＜0.05). ADC values in all of the ROIs of the mild HIE group had no statistic difference(P＞0.05).FA values in various ROIs except the WMCH,HCN and LN decreased accompanied with the severity of HIE.Compared with control group,FA values in PBS,ALIC,PLIC,Genu,Splenium,VLN,FWM,PWM,CCSO of the severe HIE group had statistic difference(P＜0.05).FA values in ALIC,PLIC,Genu, Splenium,FWM,PWM,CCSO of the moderate HIE group had statistic difference (P＜0.05).FA values in PLIC and Splenium of the mild HIE group had statistic difference(P＜0.05),among them 4 cases were normal on conventional MRI scan.FA values in PLIC and Splenium had statistic difference between all of the HIE group and controls(P＜0.05).The ability of WM injury detection of ADC/FA values was higher than that of conventional MRI,the same ability of FA values was higher than that of ADC values(P＜0.05).Correlation existed between the ADC value in CCSO and DQ(P＜0.05).Higher correlation existed between the FA values in various ROIs except WMCH,HCN,LN and DQ(P＜0.01).The highest correlation was between the FA value in PLIC and DQ.When FA value in PLIC≥0.677,the patients had good prognosis even they had irreversable brain damages,the sensitivity of this prognosis prediction was 90%,specificity was 85%,Youden index was 0.75.Conclusion:FA values can evaluate the myelination of HIE patients quantitatively,reflect the severity and range of WM lesions,its role is better than ADC values and conventional MRI. FA values in PLIC and Splenium are more sensitive to mild injury,reflect the lesion severity best.FA value has huge advantage in evaluation of the prognosis of HIE patients.FA values in cerebral WM are correlative with prognosis,FA value in PLIC has the highest correlation with prognosis.For 18 months to 3 years old HIE patients, when FA value in PLIC≥0.677,their prognosis is good.