磁共振弥散张量成像在早产儿脑白质发育及脑损伤中的应用

脑白质损伤及发育异常是导致早产儿在儿童期及青春期出现神经发育障碍的主要原因.弥散张量成像利用水分子弥散技术,可以研究早产儿脑白质成熟发育的特征,并进一步揭示早产儿脑损伤的类型及发病机制.     

弥散张量成像在早产儿脑白质损伤神经发育评价中的应用

脑白质损伤是早产儿最常见的脑损伤形式,是造成神经和智力损伤以及后期脑性瘫痪的主要原因.影像学检查在脑白质损伤的早期诊断及后期随访中发挥着重要的作用.其中核磁共振因为其安全准确的特点已成为目前应用最普遍的影像学检查.有别于传统的核磁共振技术,弥散张量成像可以在活体内观察和定量分析脑白质纤维束,现已成为评价脑白质损伤的有力工具.该文对弥散张量成像在早产儿脑白质损伤神经发育评价中的应用进行综述.     

NBNA评分联合磁共振弥散张量成像在早产儿脑白质发育评价中的作用及相关性分析

目的 探讨早产儿磁共振弥散张量成像中的各向异性分数(fractional anisotropy,FA)与新生儿行为神经测定(Neonatal Behavioral Neurological Assessment,NBNA)评分的相关性,从影像学角度评价FA在早产儿脑白质发育中的诊断价值.方法 前瞻性选择2016年10月...     

磁共振弥散张量成像定量评价生长受限胎儿脑白质发育的研究

目的探讨胎儿生长受限(FGR)是否对胎儿脑白质发育造成不良影响。方法选择28例足月小于胎龄儿(SGA)为研究对象,15例足月适于胎龄儿(AGA)为对照组,均行头颅磁共振及磁共振弥散张量成像(DTI),将颅脑白质分为122个脑区,比较两组不同脑区各向异性分数(FA)、平均弥散系数(MD)、平行弥散系数(λ_//)及垂直弥散系数(λ_⊥)的差异。结果 SGA儿16个脑区的FA值低于对照组(P0.01);7个脑区的MD值高于对照组(P0.05);8个脑区的λ_//值高于对照组(P0.05);16个脑区的λ_⊥值高于对照组(P0.05)。结论宫内生长受限可导致脑白质纤维束成熟度及完整性异常。     

磁共振弥散张量成像在新生儿胆红素血症所致神经功能障碍中的应用

目的 探讨磁共振弥散张量成像（DTI）感兴趣区（ROI）各向异性分数（FA）值在新生儿高胆红素血症所致神经功能障碍（BIND）中的价值。方法 收集2017年1月至2018年1月住院的高胆红素血症新生儿91例,根据血清总胆素峰值分为轻-中度增高组（n=45）、重度增高组（n=35）、极重度增高组（n=11）。根据是否存在异常神经系统表现分为神经功能障碍组（n=20）、非神经功能障碍组（n=71）。选择同期正常健康足月儿10例为对照组。所有新生儿完成头部DTI检查,测量并比较双侧苍白球、内囊前肢、内囊后肢、小脑齿状核的FA值。结果 极重度增高组苍白球FA值低于对照组、轻-中度增高组及重度增高组（P < 0.05）,重度增高组苍白球FA值低于对照组（P < 0.05）。极重度增高组内囊后肢FA值低于对照组、轻-中度增高组及重度增高组（P < 0.05）。神经功能障碍组苍白球、内囊后肢FA值低于非神经功能障碍组（P < 0.05）。结论 血清胆红素水平结合DTI在苍白球区、内囊后肢FA值的变化,推测BIND患儿可能同时存在神经核团及脑白质纤维损伤。     

新生儿低血糖性脑损伤磁共振成像动态变化研究

目的探讨弥散加权成像（DWI）、常规磁共振成像（MRI）在新生儿低血糖性脑损伤不同阶段的动态变化。方法回顾分析了2005年9月至2008年9月,中国医科大学附属盛京医院新生儿科收治的经MRI确诊的20例低血糖性脑损伤患儿（病例组）的临床资料,并随机选取同期住院MRI正常的20例单纯性低血糖患儿为对照组。 结果病例组平均最低血糖值低于对照组（P < 0.01）,低血糖持续时间长于对照组（P < 0.01）。病例组于低血糖发生后3.8（1～11）d完成首次MRI检查,受累部位主要为枕叶11例、枕顶叶8例,顶叶1例,受累部位在DWI均表现为高信号,常规MRI相应部位12例表现为T1加权成像（T1WI）、T2加权成像（T2WI）正常信号,仅6例表现为T1WI低信号、T2WI高信号;11例于首次检查后11.4（8～15）d完成第2次MRI检查,首次检查受累部位DWI 7例转为正常信号,4例低信号,常规MRI均表现为T1WI低信号、T2WI高信号。3例于6个月随访,提示枕叶DWI正常信号,T1WI低信号、T2WI高信号。结论新生儿低血糖性脑损伤早期DWI表现为异常高信号的部位,与晚期常规MRI表现为T1WI低信号、T2WI高信号的部位一致,这种一致性提示DWI异常高信号对于低血糖性脑损伤早期病情判断具有一定价值。     

磁共振弥散张量成像在足月窒息新生儿预后评估中的作用

目的 探讨磁共振弥散张量成像(DTI)在轻、重度足月窒息新生儿预后评估中的作用。方法 收集2013年1月至2015年12月在南通大学附属常州儿童医院新生儿科住院的25例窒息新生儿,其中轻度窒息组11例和重度窒息组14例;另将10例无脑损伤的足月儿设为对照组。所有患儿行颅脑常规磁共振和DTI检查,获取研究对象的7个感兴趣区(ROI)的表观弥散系数分数(ADC)值、各向异性(FA)值和体素量,以及白质纤维数量,分析不同程度窒息之间的差异,并对FA值与新生儿神经行为测定(NBNA)评分相关性进行分析。结果 1.丘脑FA值在对照组左、右两侧为0.54±0.08、0.56±0.15,在轻度窒息组为0.45±0.03、0.44±0.10,在重度窒息组为0.21±0.11、0.25±0.13;内囊后肢FA值在对照组左、右两侧为0.49±0.09、0.48±0.08,在轻度窒息组为0.37±0.08、0.38±0.03,在重度窒息组为0.20±0.04、0.19±0.13;丘脑和内囊后肢FA值在3组间差异有统计学意义(F＝9.12、9.11、8.18、8.55,均P<0.05)。上纵束体素量在对照组左、右两侧为1 094±112、1 123±113,在轻度窒息组为986±111、1 009±144,在重度窒息组为450±116、671±126;内囊前肢体素量在对照组左、右两侧为947±104、1 237±184,在轻度窒息组为854±118、799±114,在重度窒息组为324±110、311±126;内囊后肢体素量在对照组左、右两侧为2 047±129、2 137±238,在轻度窒息组为1 843±233、1 753±247,在重度窒息组为867±118、999±167;上纵束、内囊前肢和内囊后肢体素量在3组间差异有统计学意义(F＝10.11、9.45、7.33、8.45、12.65、11.23,均P<0.05)。扣带回白质纤维数量在对照组左、右两侧为245±72、405±94,在轻度窒息组为225±52、365±114,在重度窒息组为145±62、185±84;上额枕束白质纤维数量在对照组左、右两侧为56±19、212±33,在轻度窒息组为49±22、197±33,在重度窒息组为33±12、156±39;内囊后肢白质纤维数量在对照组左、右两侧为284±112、988±233,在轻度窒息组为234±67、678±234,在重度窒息组为114±67、188±84;扣带回、上额枕束和内囊后肢白质纤维数量在3组间差异有统计学意义(F＝3.11、3.45、9.88、9.12、7.45、8.88,均P<0.05)。2.FA值与NBNA评分相关性分析：内囊后肢FA值与NBNA评分的等级相关系数r_s为0.666,高于其他部位,以NBNA评分≥35作为预后良好的标准,可得内囊后肢FA值评估预后的ROC曲线,曲线下面积为0.816,P＝0.005。当内囊后肢FA值≥0.375时,患儿预后良好,其敏感度为73.1%,特异度为77.8%。结论 部分ROI的FA值、体素量和白质纤维的数量能定量反映窒息新生儿的脑白质损伤情况,其中内囊后肢FA值与NBNA评分相关性最显著,具有更加重要的意义,能为窒息患儿提供较为准确和客观的预后评估。     

应用弥散张量成像评价支气管肺发育不良早产儿脑白质发育的研究

目的 应用磁共振弥散张量成像（DTI）的各项异性分数（FA）和表观弥散系数（ADC）评价支气管肺发育不良（BPD）早产儿的脑白质发育。方法 以2016年8月至2019年4月生后24 h内收住NICU的出生胎龄≤32周、出生体重<1 500 g,且出院前完成头颅MRI及DTI检查的96例早产儿为研究对象。根据出院诊断分为BPD组（n=48）和非BPD组（n=48）,比较两组DTI相同感兴趣区的FA值和ADC值。结果 两组早产儿脑室周围-脑室内出血、脑室周围白质软化、局灶性脑白质损伤等发生率差异无统计学意义（P > 0.05）。BPD组早产儿内囊后肢、胼胝体压部、枕叶白质、小脑、大脑脚的FA值低于非BPD组（P < 0.05）,各ADC值高于非BPD组（P < 0.05）。与非BPD组相比,BPD组早产儿呼吸暂停次数更多、肺炎发生率和机械通气比例更高、辅助通气时间更长（P < 0.05）。结论 BPD对早产儿脑白质发育具有潜在影响,可导致脑白质发育延迟,因此,需关注该类患儿的神经功能。     

应用弥散张量成像评价支气管肺发育不良早产儿脑白质发育的研究

目的 应用磁共振弥散张量成像（DTI）的各项异性分数（FA）和表观弥散系数（ADC）评价支气管肺发育不良（BPD）早产儿的脑白质发育。方法 以2016年8月至2019年4月生后24 h内收住NICU的出生胎龄≤32周、出生体重<1 500 g,且出院前完成头颅MRI及DTI检查的96例早产儿为研究对象。根据出院诊断分为BPD组（n=48）和非BPD组（n=48）,比较两组DTI相同感兴趣区的FA值和ADC值。结果 两组早产儿脑室周围-脑室内出血、脑室周围白质软化、局灶性脑白质损伤等发生率差异无统计学意义（P > 0.05）。BPD组早产儿内囊后肢、胼胝体压部、枕叶白质、小脑、大脑脚的FA值低于非BPD组（P < 0.05）,各ADC值高于非BPD组（P < 0.05）。与非BPD组相比,BPD组早产儿呼吸暂停次数更多、肺炎发生率和机械通气比例更高、辅助通气时间更长（P < 0.05）。结论 BPD对早产儿脑白质发育具有潜在影响,可导致脑白质发育延迟,因此,需关注该类患儿的神经功能。     

新生儿低血糖脑损伤临床特征与磁共振成像动态变化

目的：探讨新生儿低血糖性脑损伤的影像特征与临床及预后关系,为低血糖性脑损伤的诊断及预防提供依据。方法：16例低血糖性脑损伤新生儿于入院24~48小时（n=16）,生后2周左右（n=11）,1~5月(n=3)进行了常规的MRI 与MRI-DWI动态观察与临床随访。结果：惊厥、嗜睡、肌张力减低为常见的症状和体征,昏迷和呼吸衰竭5例。低血糖脑损伤时最低血糖值为0.98±0.43 mmol/L,5例重者血糖为0.72±0.42 mmol/L。脑电图提示轻者为间断低电压,重者电压平坦,甚至电静息。16例均有顶枕部皮层受累,合并脑室周围白质损伤2例,弥漫性皮层受累5例,其中1例合并广泛的脑白质损伤,2例合并丘脑基底节受累。弥漫性皮层受累5例和顶枕部合并脑白质损伤2例血糖明显低于仅有顶枕部受累者（0.71±0.35 mmol/L vs 1.19±0.42 mmol/L,t=2.4124,P<0.05）。早期信号改变在DWI表现最明显为高信号。4例弥漫性脑水肿者再次检查已发生广泛性脑萎缩和多发脑软化;顶枕部受累者7例接受了再次检查,5例T1WI与T2WI信号异常,而DWI信号异常3例。临床表现轻者以顶枕部皮层受累为主,重者弥漫性皮层受累为主。顶枕部受累1例随访发现髓鞘发育落后;合并白质受累1例发生双下肢痉挛性瘫痪;弥漫性皮层受累1例发生广泛脑软化。结论：新生儿低血糖性脑损伤与低血糖的严重程度密切相关,顶枕部皮层是易损区,但重度的损伤可表现为弥漫性皮层受累甚至合并广泛的白质或基底节丘脑受损,DWI可以早期反映脑损伤情况。     

Diffusion tensor imaging of the inferior colliculus and brainstem auditory-evoked potentials in preterm infants

Background  Preterm and low-birth-weight infants have an increased risk of sensorineural hearing loss. Brainstem auditory-evoked potentials (BAEP) are an effective method to detect subtle deficits in impulse conduction in the auditory pathway. Abnormalities on diffusion tensor imaging (DTI) have been shown to be associated with perinatal white-matter injury and reduced fractional anisotropy (FA) has been reported in patients with sensorineural hearing loss. Objectives  To evaluate the possibility of a correlation between BAEP and DTI of the inferior colliculus in preterm infants. Materials and methods  DTI at term age and BAEP measurements were performed on all very-low-birth-weight or very preterm study infants (n=56). FA and apparent diffusion coefficient (ADC) of the inferior colliculus were measured from the DTI. Results  Shorter BAEP wave I, III, and V latencies and I–III and I–V intervals and higher wave V amplitude correlated with higher FA of the inferior colliculus. Conclusion:  The association between the DTI findings of the inferior colliculus and BAEP responses suggests that DTI can be used to assess the integrity of the auditory pathway in preterm infants.     

Principles and implementation of diffusion-weighted and diffusion tensor imaging

We review the physiological basis of diffusion-weighted imaging and discuss the implementation of diffusion-weighted imaging pulse sequences and the subsequent postprocessing to yield quantitative estimations of diffusion parameters. We also introduce the concept of directionality of “apparent” diffusion in vivo and the means of assessing such anisotropy quantitatively. This in turn leads to the methodological application of diffusion tensor imaging and the subsequent postprocessing, known as tractography. The following articles deal with the clinical applications enabled by such methodologies.     

Clinical applications of diffusion tensor imaging and tractography in children

Diffusion tensor imaging (DTI) is a relatively new addition to routine MR imaging. DTI exploits the preferential movement of water protons within the brain along the axis of the axons. This anisotropic diffusion provides information about the immature brain prior to myelination, during maturation, and in normal and disease states, information that MRI cannot provide. By virtue of sensitivity to anisotropic movement of protons, DTI allows the core of larger individual white matter tracts to be visualized as discreet anatomic structures. DTI can also provide information about the microarchitecture of white matter in the form of metrics referred to as fractional anisotropy and diffusivity. The information contained within the diffusion tensor data can be used to create 3-D mathematical renderings of white matter or tractography. This article is an introduction to DTI for pediatric radiologists interested in exploring potential applications in children.     

Diffusion-weighted and diffusion tensor imaging for pediatric musculoskeletal disorders

Diffusion-weighted imaging (DWI) is a powerful tool that has recently been applied to evaluate several pediatric musculoskeletal disorders. DWI probes abnormalities of tissue structure by detecting microscopic changes in water mobility that develop when disease alters the organization of normal tissue. DWI provides tissue characterization at a cellular level beyond what is available with other imaging techniques, and can sometimes identify pathology before gross anatomic alterations manifest. These features of early detection and tissue characterization make DWI particularly appealing for probing diseases that affect the musculoskeletal system. This article focuses on the current and future applications of DWI in the musculoskeletal system, with particular attention paid to pediatric disorders. Although most of the applications are experimental, we have emphasized the current state of knowledge and the main research questions that need to be investigated.     

Novel diffusion tensor imaging findings in Krabbe disease

BackgroundKrabbe disease is a lysosomal disorder that primarily affects myelin. Diffusion tensor imaging (DTI) provides quantitative information about the white matter organization and integrity. Radial diffusivity (RD) reflects myelin injury selectively.PurposeTo report on quantitative DTI findings (including axial diffusivity (AD) and RD, not previously reported) in two children with Krabbe disease compared to controls.MethodsA quantitative region of interest (ROI) based DTI analysis was performed for the patients and age- and gender-matched controls. Fractional anisotropy (FA), mean diffusivity, AD and RD values as well as variation ratios between the patients' and controls' values were calculated for nine brain regions.ResultsTwo boys with Krabbe disease were included in this study. DTI data were acquired at the ages of 6.25 years and 6.5 months. For all regions, FA ratios were negative, while RD and MD ratios positive. The most elevated variation ratios were found for RD. Variation ratios were greater in the centrum semiovale, corpus callosum, and middle cerebellar peduncles than in other anatomical regions, especially in the older patient in comparison with the younger patient. The AD ratios, however, were much lower and close to zero.ConclusionsDTI allows a quantitative evaluation of white matter damage in Krabbe disease. RD seems to be the most sensitive DTI parameter in agreement with the histopathological findings in Krabbe disease, a primary myelin disorder. This may be important in the early detection of the onset of demyelination.     

Magnetic resonance imaging in neonatal stroke

Neonatal stroke occurs in 1 in 2300–5000 live births, the incidence of which is lower than that in adults, but still higher than that in childhood. The higher incidence of perinatal stroke in preterm and term infants compared to stroke in childhood may be partly explained by higher detection rates using routine fetal ultrasound and postnatal cranial sonography. In addition, there is greater availability of magnetic resonance imaging (MRI) for neuroimaging in preterm and full-term infants, which is due in part to the availability of MR-compatible incubators and MR systems at or near the neonatal intensive care unit. In addition, the wide range of MR techniques, such as T2-, diffusion- and susceptibility-weighted imaging allows improved visualization and quantification of neonatal stroke or hypoxic–ischemic injury. This chapter reviews the MR neuroimaging modalities that actually assist the clinician in the detection of neonatal stroke.     

Microstructural development of human brain assessed in utero by diffusion tensor imaging

Background Diffusion-weighted MR imaging (DWI) has been shown to be a great tool to assess white matter development in normal infants. Comparison of cerebral diffusion properties between preterm infants and fetuses of corresponding ages should assist in determining the impact of premature ex utero life on brain maturation. Objective To assess in utero maturation-dependent microstructural changes of fetal cerebral white matter using diffusion tensor MR imaging. Materials and methods An echoplanar sequence with diffusion gradient (b=700 s/mm²) applied in six non-colinear directions was performed between 31 and 37⁺³ weeks of gestation in 24 fetuses without cerebral abnormality on T1- and T2-weighted images. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in the white matter. Results Mean ADC values were 1.8 μm²/ms in the centrum semiovale, 1.2 μm²/ms in the splenium of the corpus callosum and 1.1 μm²/ms in the pyramidal tract. The paired Wilcoxon rank test showed significant differences in ADC between these three white matter regions. Mean FA values were 1.1%, 3.8% and 4.7%, respectively, in the centrum semiovale, corpus callosum and pyramidal tract. A significant age-related decrease in ADC and an increase in FA towards term were demonstrated in the pyramidal tract and corpus callosum. Conclusion Diffusion tensor imaging in utero can provide a quantitative assessment of the microstructural development of fetal white matter. Anisotropic parameters of the diffusion tensor should improve with technical advances.     

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.     

MRI neurography and diffusion tensor imaging of a sciatic perineuroma in a child

Perineuroma, rare in children, presents as a painless mononeuropathy of a major nerve trunk. Resection of the lesion with end-to-end sural nerve grafting appears to be the treatment of choice. This technique is not recommended if the unhealthy segment of nerve is too long or if spinal roots are involved. However, in children, reports of direct MR evaluation of nerve trunks and of the exiting nerve roots are limited. We report a 7-year-old girl with an intramural sciatic nerve perineuroma in whom the diagnosis was made by MRI and confirmed by biopsy. The MR protocol combining 3-D T2-W STIR SPACE, fat-saturated gadolinium-enhanced T1-W images, and diffusion tensor imaging with tractography was a valuable tool for depicting peripheral nerve and roots in order to plan surgical treatment.