磁共振弥散加权成像在早产儿脑室周围白质软化早期的预测价值

目的 探讨磁共振弥散加权成像(DWI)早期评价和预测早产儿脑室周围白质软化(PVL)的作用及意义.方法 回顾分析2005年8月至2007年4月,在我院新生儿科住院,且经头部MRI确诊的12例PVL早产儿生后7 d内、2 w和4 w的DWI及常规MRI资料.结果 初次检查(平均生后4.5 d)全部病例DWI均显示双侧脑室周围脑白质对称性、弥漫性高信号,常规MRI基本正常;出生后2周DWI示脑白质内不规则高、低混杂信号,而常规MRI则显示相应部位小片状或点状T1WI高信号,T2WI稍低信号;出生后4W DWI示侧脑室后角、枕部三角区大小不等的囊性低信号,常规MRI显示相应病灶的T1WI低信号,T2WI高信号(即囊性PVL改变);出生后4个月常规MRI示囊腔逐渐变小、消失,脑白质减少、脑室扩大.结论 DWI显示的双侧脑室周围白质对称性弥漫性高信号是PVL的最早期表现;所提供的影像学异常变化与晚期常规MRl所证实PVL发生的高度相关性,表明了DWI可能是早期评价脑白质损伤及预测早产儿PVL发生的重要检测手段.

Values of diffusion-weighted magnetic resonance imaging in the early detection of periventricular leukomalacia in preterm infants

Objective Periventricular leukomalacia(PVL),the principal form of brain injury in the premature infant.is characterized by overt focal necrotic lesions in periventricular white matter and diffuse cerebral white matter injury.The early detection of the disease is not consistently possible with cranial uhrasonography or conventional magnetic resonance imaging(MRI).Recently,diffusion-weighted imaging (DWI)has been shown to be highly sensitive in detecting acute ischemic cerebral injury.This study aimed to evaluate possible role of DWI in early diagnosis of PVL Methods Images and elinical data from 12 preterm infants with PVL diagnosed in our NICU from August,2005 to April,2007 were reviewed.MRI using conventional and diffusion-weighted imaging,as well as the assays of blood routine test,sertun bilirubin,C-reactive protein(CRP),blood culture,blood gas analysis,blood sugar and serum ions were performed in these pretenn infants.All examinations were performed on a 3.0-T MRI system (Philips Intera Acheva Magnetom Vision)with echo-planar imaging capability with the use of a standard protocol.The imaging protocol for all the patients contained diffuse weighted images(EPI-SE,TR=2144 ms,TE=56 ms),T1-weighted images(TR=389 ms;TE=15 ms;slice thickness=4 mm) as well as T2-weighted images(TR=3035 ms;TE=100 ma;slice thickness=4mm).The first MR examinations were performed in all these twelve preterm infants (mean age 4.5 days,range 2-7 days).Conventional MRI and DWI sequences obtained in the acute phase were compared.All the neonates underwent another two MRI examinations up to 2 and 4 weeks after delivery;five subjects also underwent MRI follow-up for up to 4-8 months(in 3 for 4 months,in 1 for 7 months,and in another for 8 months).Oualitative evalnations were performed to assess the presence of DWI changes compatible with PVL Results The gestational ages of these twelve patients were from 31 to 35 weeks.None of them had intrauterine distress or birth asphyxia.None of the patients had localized neurological signs in the early course except for abnormal mnscular tone of some extent,but seizure and apnea were their major symptoms.No other positive signs of nervous system was found in these preterm infants with PVL First DWI detection(on the average of 4.5 days)in all these infants showed bilateral,symmetric,diffuse high aignal intensity (including genu and plenum of corpuscallosum),while conventional MBI showed normal images on both T1-and T2-weighted imaging;two weeks later,DWI showed irregularly high,low mixed signals while conventional MRI showed puncmte high signal intensity on T1-weighted imaging and slighdy lower signal on T2-weighted imaging.Four weeks later,DWI showed cystic low signal intensit where conventional MBI showed low signal intensity on T1-weighted imaging and high signal intensity on T2-weighted imaging(cystic PVL).Four months later,DWI showed that the cystic cava became diminished and disappeared,while conventional MRI shewed reduced cerebral white matter and dilation of ventricle.Condusion Bilateral,symmetric,diffuse high signal intensity on DWI seenls to he the earliest evidence of PVL;diffusion-weighted imaging performed in the acute phase of the disease may have a higher correlation with later evidence of PVL than does conventional MR imaging.DWI is likely to be a considerable technique in the early assessment of white matter injury and later PVL in preterm infants.