常规MRI正常的新生儿缺氧缺血性脑病弥散张量成像初探

Diffusion-tensor MR imaging in neonates with hypoxic-ischemic encephalopathy but normal brain conventional MR imaging results:Preliminary findings

目的研究弥散张量MRI(diffusion-tensorMRimaging,DTI)对于临床诊断为新生儿缺氧缺血性脑病(hypoxic-ischemicencephalopathy,HIE)而常规MRI所见为正常病例的评估能力。方法选择20例常规MRI所见为正常的足月HIE患儿,以10例正常新生儿为对照,分组进行常规MRI、DTI扫描,测定两组新生儿相同感兴趣区(regionofinterest,ROI)的平均弥散度(meandiffusivity,Da)、分数各向异性(fractionalanisotropy,FA)和相对各向异性值(relativeanisotropy,RA)。用Studentt-test法检验两组患儿各项指标,并观察比较两组新生儿的彩色FA图和彩色编码张量图。结果两组新生儿的Da在侧脑室前角前外侧白质、内囊后肢,放射冠各个感兴趣区均无显著性差异,而FA和RA值各感兴趣区则有明显差异,表现为HIE患儿FA值和RA值的下降,并且Da的高低与孕龄的长短有一定相关性。结论FA和RA是HIE患儿白质损伤或功能障碍的敏感指标,结合彩色FA图和彩色编码张量图可对患儿白质髓鞘的损伤作出较为准确、客观的评价,并可能在今后评估患儿的预后转归方面起重要作用。

Objective To determine whether diffusion-tensor magnetic resonance (MR) imaging can depict abnormalities in term neonates with a diagnosis of hypoxic-ischemic encephalopathy (HIE) but normal brain MR imaging results.Methods Twenty term neonates who received a diagnosis of HIE but normal brain MR imaging results underwent brain MR examinations,including diffusion-tensor MR imaging.The MR findings in these patients were compared with those in ten healthy term neonates.Mean diffusivity (D_a) and fractional anisotropy (FA) and relative anisotropy (RA) were measured bilaterally in predefined regions in the two groups.A student t -test was performed for each region of interest (ROI) and color-coded FA images and color-coded tensor images were reconstructed to compare the control group with the other group.Results D_a values of the two groups were not significantly different in white matter of anterolateral to the anterior horn of the lateral ventricle and posterior limb of internal capsule and corona radiata,while FA and RA values were significantly different in the same ROIs.In term neonates with HIE,diffusion-tensor MR imaging depicted decreases in FA and RA in the white matter fiber tracts,which appeared to be normal at conventional MR imaging.Values of D_a showed statistically significant correlations with gestational age.It didn't appeared yellow or red color on color-coded FA images because of lower FA and appeared mixed color and thinner in the posterior limb of internal capsules in the neonates with HIE.Conclusion FA and RA are sensitive markers of white matter injury or disruption in term neonates with HIE.Diffusion-tensor MR imaging combined with color-coded FA images and color-coded tensor images can improve conspicuity of hypoxic-ischemic injury.Calculation of anisotropy values may provide an objective measure of hypoxic-ischemic injury and evaluate prognosis.