Primary Application Of Susceptibility Weighted Imaging (SWI) In Neonatal Intracranial Hemorrhage

Objective:1.To explore the SWI appearance and differential diagnosis of neonatal intracranial hemorrhage(NICH) and advantages of SWI for detecting NICH,correlated it with conventional MR sequences;the relevant documents were reviewed to study the pathological change and MR imagings of all kinds of NICH in this study.2.Combine the coincidence of NICH with its correlation with clinical variables (gestational age,Apgar Scores,etiological factor and so on),by which way the relationships of NICH with gestational age and Apgar Scores were discussed.We summarize the pathogenesis of NICH in the setting of this study.Material and Method:1.Study population97 cases of neonate(55 male and 42 female) were born at 28 through 41 weeks gestational age.26 cases of preterm neonates and 71 cases of full-term neonates were included.They were obtained from neonatal intensive care unit for conventional MRI and SWI based on the clinical assessment of high risk for neurologic damage.Clinical data include estimated asphyxia,gestational age,Apgar Scores,birth weight and age at MR imaging.All but 6 patients had estimated Apgar Scores,which was utilized to evaluate asphyxial degree of neonates.49 cases of normal Apgar Scores and 42 cases of abnormal Apgar Scores were admitted to this study.The age at MR imaging ranges 2 from 32 days.88 cases were suffered form perinatal asphyxia,19 cases were low birth weight preterm infant,3 very low birth weight preterm infant,2 syphilis congenita, 1 acetomorphine withdrawal syndrome.2.Main instrument or equipment3.0T SIGNA EXITE GE MR Scanner with 8 channel phased-array coil were used and post-processing work was done through GE AW workstation.3.Preparations before examinationAll neonates were fed their routine enteral feeding and sedated with 10%chloral hydate(30 to 40 mg/kg of body weight) per os and Phenobarbital(2 to 4 mg/kg of body weight) i.m.pro re nate.All neonates,swaddled in blankets,were transported by physician or neonatal nurse clinician who remained in attendance throughout the procedure.They were arrived in radiology department about 10 minutes ahead of schedule.All neonates were fitted with ear protection and had their heads secured with plastic sponge.The imaging room was equipped with oxygen,compressed air,and suctioning sources,where the temperature,humidity and ventilation is suitable for neonates. 4.Examination technique and image processingThe space of the MR imaging coil was filled with the plastic sponge which close proximity to neonatal head.The conventional MRI scan was performed with the position line located between superciliary arches.Imaging approach include:T1WI(axial and sagittal plane),T2WI,T2Flair,and SWI.SWI scan was performed after the T1WI and T2WI sequence.The parameter of SWI scan were: TR:35ms,TE:25ms,FOV:24X24cm,Matrix:512X512,slice thick3.0mm, 56 slices.The data obtained from SWI scan then was transformed to AW workstation, in which the SWI image was reconstructed as follow parameter:high pass background frequency filter bandwidth:32,mask times 4,low quality channel removal index:9.4.Statistical analysisData analyses were performed by using SPSS 13.0 software in this study.The statistical difference between two groups was analyzed with Chi-Square nonparametric test.The Chi-Square test's statistical differences were considered as statistically significant when P values＜.05.Result46 cases of neonatal intracranial hemorrhage(NICH) were found in total 97 cases of neonatal intensive care unit(NICU).NICH presented with typical paramagnetic material in SWI and the phase image.In SWI image the lesion had mottling,oval-shape,irregular casting shape.The largest dimension of lesion was no more than 30mm,and the smallest less than 0.5mm.NICH was difficult to be detected in conventional MR sequence examination(include T1WI,T2WI,FLAIR).NICH mainly located in:subependyma,intraventricle,intraparenchyma, intracerebellum,subarachnoid cavity,subdural space.36 cases of total 46 cases of NICH were found in conventional MR sequences,the appearance of hemorrhage underwent characteristic evolution with time.The appearance of hemorrhage in routine MR can make reference to the discussion.However,10 cases of NICH were unable to be detected in routine MR,in which did not show the dimension of lesion of less than 5 mm.SWI respectively revealed SAH and SDH in 12 and 27 patients.On conventional MR images,the SAH and SDH respectively exhibited signal changing in 12 and 19 patients.SWI also revealed more hemorrhagic focus of NICH than did conventional MRI,with the total number of hemorrhagic focus in subependyma, intraventricle,intraparenchyma and intracerebellum revealed by SWI of 104 versus 13 revealed by routine MRI.Therefore,SWI have significant advantages over routine MRI for the diagnosis of NICH and the detection of hemorrhagic focus.All cases of NICH had case history of prenatal asphyxia.NICH occurred in 13 cases of the total 49 cases of normal Apgar Score and in 27 cases of the total 42 cases of abnormal Apgar Score in this study.The NICH had a lower rate in group with normal Apgar scores which more than 8 at 1min and with ascending Apgar scores at 5,10 min.NICH occurred in 10 cases of the total 26 cases of preterm neonates and in 35 cases of the total 71 cases of full-term neonates in this study.The rate of preterm neonates with findings of NICH seems to be higher than that of the full-term.SWI able to detect 1 of 4 cases of normal birth weight preterm infant,6 of 19 low birth weight preterm infant,2 of 3 very low birth weight preterm infant.ConclusionCompared with conventional MRI,SWI was more sensitive in detection of intracranial hemorrhage of neonates.The comparison SWI versus routine MR had the most significant discriminating power(χ~2=8.1,P＜0.005).More and larger lesions were showed on SWI.On SWI magnitude image,intracranial hemorrhage of neonates had mottling,oval-shape,irregular casting shape and represented with low signal.The main distributions of NICH were subependyma,intraventricle,intraparenchyma, intracerebellum,subarachnoid cavity,subdural space,as demonstrated on SWI. Therefore,the study of 97 neonates showed that SWI had significant advantages over conventional MRI for the detection of intracranial hemorrhage in neonates with prenatal asphyxia.All neonates with unfavorable NICH had case history of prenatal asphyxia.The comparison abnormal Apgar Scores(group with asphyxia) versus control group had the most significant discriminating power(χ~2=13.086,P＜0.01).The rate of NICH in group with asphyxia was higher than control group.Thus,the system of Apgar Scores still plays a important role in evaluating the conditions of neonates,also provides a significant evidence for the diagnosis of NICH with prenatal asphyxia.In the control group of normal Apgar Scores,13/49(26.5%) neonates had ICH on SWI and/or routine MRI,this indicated that the sensitivity and specificity of the system of Apgar Scores for evaluating NICH after prenatal asphyxia are likely to be poor.No difference in gestational age was found between the group of preterm neonates and the group of full-term neonates(χ~2=0.898,P=0.343＞0.05).The majority difference between these 2 groups was the maturity of brain,which means the maturity of brain could not be considered as unique etiopathogenisis for NICH.In a word,as for neonates with prenatal asthyxia,we did not consider full-term gestational age and normal Apgar Sores respectively as an unique factor which preclude them from NICH.