X线计算机体层摄影术、磁共振成像和脑磁图描记术在急性脑梗死诊断中的应用

急性脑梗死是临床常见的缺血性脑血管疾病，具有高发病率、高死亡率及高致残率的特点，早诊断、早治疗是及早阻止疾病发展、改善预后的关键。笔者主要就急性脑梗死在X线计算机体层摄影术(CT)、磁共振成像(MRI)、脑磁图描记术(MEG)等神经影像中的早期表现及相关原理进行阐述。常规CT普及率高、经济、便捷，对脑出血敏感度高，是急性脑梗死与脑出血鉴别首选，缺点是成像对比度差，对脑梗死早期诊断精确性差。CT灌注成像对急性脑梗死的早期诊断和缺血半暗带定位具有更大的优势。MRI是具有多种扫描序列，可对不同状态下脑组织内水分子状态精确分辨，对脑梗死的诊断、分期具有极高的应用价值。临床常规的T1、T2、FLAIR加权像可在起病后数小时观测到异常信号，而DWI序列在局部脑组织缺血后5min即可见信号增强。SWI序列可以检测CT、常规MRI无法显示的微出血灶。MRS成像可以检测多种细胞内化合物成分，这些化合物对急性脑梗死不同时期、不同程度的细胞损伤具有特定意义。MEG可以灵敏检测大脑神经元细胞的异常放电，并能对异常信号发生源精确定位，时间分辨率达ms级，空间分辨率达mm级。MEG通过监测不同功能区的诱发磁场，可以定位病灶，同时灵敏客观反映脑功能损伤情况。但其昂贵的价格、低普及率、对被检查者的配合要求都限制了MEG的应用。目前神经影像学技发展快，随着设备及软件的进一步开发，急性脑梗死诊治水平会有进一步的提高。

Application of computed tomography,magnetic resonance imaging,magnetoencephalography in the diagnosis of acute cerebral infarction

As a common type of cerebrovascular disease, acute cerebral infarction has higher incidence, mortality and morbidity.Earlier diagnosis and treatment is a key to prevent the development of diseases and improve prognosis.The author mainly focus on the different roles of CT, MRI and MEG in early stage of acute cerebral infarction.CT has high penetration and quick scanning speed and could accurately identify cerebral hemorrhage and infarction, while low precision limits its use in the early diagnosis of acute cerebral infarction.CT perfusion imaging has the advantage of establishing early diagnosis and infarction position.MRI sequence could separate different kinds of tissue edema, which enhances the applied value of diagnosis and installment of acute cerebral infarction.Normal sequences like T1, T2 and FLAIR can detect abnormal signal in several hours after disease onset, while DWI sequence can see signal enhancement after 5min.Latently, SWI sequence is able to find micro bleeding in the area of perfusion after ischemia, which is difficult to be detected by CT or MRI.MRS can exam different metabolisms to find different type cell damage, but it is unable to locate.MEG is used to monitor neurons′ abnormal discharge, which even more accurate than EEG.Somatosensory evokedmagnetic fields can help locate infarction area, showing function loss through brain damage at the same time.However, its high price and high degree of patient′s adaptability limit its applications.The further development of diagnosis and treatment in acute cerebral infarction will benefit from the progress of neuroimaging.