Barkovich A J, Miller S P, Bartha A, Newton N, Hamrick S E G, Mukherjee P, Glenn O A, Xu D, Partridge J C, Ferriero D M, Vigneron D B
Department of Radiology, University of California at San Francisco, San Francisco, Calif 94143-0628, USA.
AJNR Am J Neuroradiol. 2006 Mar;27(3):533-47.
Although the imaging, spectroscopic, and diffusion characteristics of brains of infants with neonatal encephalopathy have been described, the time course during which these changes evolve is not clear. The results of sequential MR imaging studies--including anatomic MR imaging, proton MR spectroscopy, and diffusion tensor imaging (DTI)--of 10 patients enrolled prospectively in a study of neonatal encephalopathy are reported to help to clarify the time course of changes in different brain regions during the first 2 weeks of life.
Ten neonates were prospectively enrolled in a study of the evolution of MR findings in neonatal encephalopathy and were studied 2 (8 patients) or 3 (2 patients) times within the first 2 weeks of life. The MR examination included spin-echo T1 and T2-weighted images, DTI, and long echo time (288 milliseconds) proton MR spectroscopy. Diffusion parameters (diffusivity [D(av)], fractional anisotropy [FA], and individual eigenvalues) were calculated for 10 1-cm2 regions of interest in each hemisphere that were placed based on anatomic landmarks. D(av) and FA were then measured manually in the same areas on a workstation. Metabolite ratios (NAA/Ch, Cr/Ch, Cr/NAA, Lac/Ch, and Lac/NAA) were calculated in 7 regions of interest. Imaging appearance, diffusion parameters, and metabolite ratios were then evaluated longitudinally (comparing with other studies on the same patient at different times) and cross-sectionally (comparing all studies performed on the same postnatal day).
In most of the patients a characteristic evolution of DTI and MR spectroscopy parameters was seen during the first 2 weeks after birth. Although the anatomic images were normal or nearly normal on the first 2 days after birth in most patients, abnormalities were detected on DTI (both visually and by quantitative interrogation of D(av) maps) and proton MR spectroscopy (abnormal metabolite ratios). These parameters tended to worsen until about day 5 and then normalize, though in several patients abnormal metabolite ratios persisted. Of interest, as areas of abnormal diffusivity pseudonormalized within one region of the brain they would develop in other areas. Therefore, the pattern of injury looked very different when imaging was performed at different times during this evolution.
Patterns of injury detected by standard anatomic imaging sequences, DTI sequences, and proton MR spectroscopy varied considerably during the first 2 weeks after injury. The appearance of new areas of reduced diffusion simultaneous with the pseudonormalization of areas that had reduced diffusion at earlier times can result in an entirely different pattern of injury on diffusivity maps acquired at different time points. Awareness of these evolving patterns is essential if studies are performed and interpreted during this critical period of time.
尽管已对患有新生儿脑病的婴儿大脑的成像、光谱和扩散特征进行了描述，但这些变化演变的时间过程尚不清楚。本文报告了对10例前瞻性纳入新生儿脑病研究的患者进行的系列磁共振成像研究结果，包括解剖磁共振成像、质子磁共振波谱和扩散张量成像（DTI），以帮助阐明出生后前2周不同脑区变化的时间过程。
10例新生儿前瞻性纳入新生儿脑病磁共振成像结果演变的研究，并在出生后前2周内接受了2次（8例患者）或3次（2例患者）检查。磁共振检查包括自旋回波T1和T2加权图像、DTI以及长回波时间（288毫秒）质子磁共振波谱。基于解剖标志在每个半球放置10个1平方厘米的感兴趣区，计算扩散参数（扩散率[D(av)]、各向异性分数[FA]和各个本征值）。然后在工作站上手动测量同一区域的D(av)和FA。在7个感兴趣区计算代谢物比率（NAA/Ch、Cr/Ch、Cr/NAA、Lac/Ch和Lac/NAA）。然后纵向（与同一患者在不同时间的其他研究进行比较）和横向（比较在同一出生后天数进行的所有研究）评估成像表现、扩散参数和代谢物比率。
在大多数患者中，出生后前2周内DTI和磁共振波谱参数呈现出特征性演变。尽管大多数患者在出生后前两天的解剖图像正常或接近正常，但在DTI（通过视觉检查和对D(av)图进行定量分析）和质子磁共振波谱（代谢物比率异常）上检测到了异常。这些参数往往在第5天左右恶化，然后恢复正常，不过在一些患者中，异常的代谢物比率持续存在。有趣的是，当大脑一个区域内异常扩散区域伪正常化时，其他区域会出现异常扩散。因此，在这一演变过程中不同时间进行成像时，损伤模式看起来非常不同。
标准解剖成像序列、DTI序列和质子磁共振波谱检测到的损伤模式在损伤后前2周内有很大差异。新出现的扩散降低区域与早期扩散降低区域的伪正常化同时出现，可能导致在不同时间点获取的扩散率图上出现完全不同的损伤模式。如果在这一关键时期进行研究和解读，了解这些不断演变的模式至关重要。
