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目的通过对比性研究大鼠在微波辐射后的功能磁共振影像技术(fMRI)获取的海马影像表征参数与空间记忆能力及海马脑区病理结构改变之间的关联性,探讨将fMRI应用于微波辐射脑损伤效应研究的可行性。方法以30 mW/cm~2的微波一次辐射27只Wistar雄性大鼠15 min,对照组24只,于辐射后6 h、1 d、2 d、3 d、4 d、7 d、14 d分别采用Morris水迷宫检测大鼠空间记忆能力改变;光镜和电镜观察海马脑区病理变化;并应用fMRI的扩散加权成像(DWI)、动脉自旋标记(ASL)和磁共振波谱(MRS)等技术动态扫描海马脑区的表观扩散系数(ADC)、血流灌注(CBF)、代谢物质等变化。结果微波辐射后1~3 d大鼠平均逃避潜伏期(AEL)显著延长(P<0.05或P<0.01);海马神经元出现变性、凋亡(核染色质凝聚、边集)、坏死;线粒体肿胀空化、血管周间隙增宽。fMRI扫描成像显示,辐射后3~14 d分别海马脑区ADC值升高,血流灌注(CBF)减少,MRS显示海马脑区代谢物质N-乙酰天门冬氨酸与肌酸的比值(NAA/Cr)、谷氨酸类化合物与肌酸的比值(Glx/Cr)显著增加,胆碱化合物与肌酸的比值(Cho/Cr)显著降低,上述海马区病变及行为认知障碍等损伤效应与fMRI显示的特征参数在辐射后1~7 d呈现明显的一致性。结论微波辐射致大鼠海马损伤的fMRI特征与其行为认知障碍、组织结构病变及生物代谢指标变化具有良好的关联性。
OBJECTIVE: To compare the correlation between hippocampal imaging parameters acquired by fMRI and spatial memory and pathological changes in the hippocampus of rats after a comparative study of the effects of fMRI on microwave radiation Feasibility of study on brain injury. Methods A total of 27 Wistar male rats were irradiated with 30 mW / cm ~ (-2) microwaves for 15 min at a time and 24 in the control group at 6 h, 1 d, 2 d, 3 d, 4 d, 7 d and 14 d after radiation Morris water maze was used to detect the change of spatial memory in rats. The pathological changes in the hippocampus were observed under light microscope and electron microscope. Diffusion weighted imaging (fMRI), ASL and MRS Dynamic scanning of hippocampus brain area apparent diffusion coefficient (ADC), blood flow perfusion (CBF), metabolites and other changes. Results The mean escape latency (AEL) of rats after 1 ~ 3 days of microwave irradiation was significantly prolonged (P <0.05 or P <0.01). The hippocampal neurons were degenerated and apoptotic (nuclear chromatin condensation, marginal set), necrosis and mitochondrial swelling Cavitation, vascular perimeter gap widened. fMRI scan imaging showed that the ADC value of hippocampal brain area increased and blood flow perfusion (CBF) decreased from 3 to 14 days after radiation. MRS showed that the ratio of NAA / Cr), glutamate to creatine ratio (Glx / Cr) significantly increased, the ratio of choline compound to creatine (Cho / Cr) was significantly reduced, the lesion and behavioral cognitive impairment in the above hippocampus and other lesion effects and The characteristic parameters displayed by fMRI showed significant agreement between 1 and 7 days after irradiation. Conclusion The fMRI characteristics of hippocampus in rats exposed to microwave radiation have a good correlation with cognitive impairment, histopathological changes and changes of bio-metabolic indexes.