大鼠脑内血肿继发性损伤7T核磁共振影像学研究

Secondary injury in rats with intra-cerebral hematoma： a 7 Tesla high-field strength MRI study

目的应用高场强7T核磁共振影像仪动态分析脑出血大鼠脑水肿吸收演化过程及局部脑铁含量演变情况，探讨脑出血后继发性损伤病程特点及机制。方法SD成年大鼠16只，按随机数字表法分为实验组（n=10）和对照组（n=6）。实验组右侧尾状核注入自体静脉血50μL，对照组同部位等量注入生理盐水。建模后1、2、3、7及14d对2组大鼠分别行7T头颅核磁共振成像T2及T2-star序列扫描，对比分析影像学变化特点。结果实验组成功建模9只，术毕死亡1只。早期（3dN）T2加权成像清晰，血肿周边T2弛豫时间上升迅速，3d后逐渐平缓，7d达高峰；建模后损害范围吸收减小，3d时转而出现扩大趋势，7d左右达峰值。建模3d后T2-star值迅速出现峰值，后缓和下降。对照组除针道损伤外，未见其他明显信号改变。结论脑出血后继发性损伤呈现短期内快速进展．平稳后再次加剧的演变趋势，病灶局部铁含量变化趋势与继发性损伤变化趋势同步，提示铁在继发性脑损伤发生机制中起重要作用。

Objective To dynamically analyze the evolutionary process of cerebral edema absorption and the level of local iron in rats with intra-cerebral hematoma by high-field strength 7 Tesla MRI and explore the characteristics and mechanism of secondary injury after intra-cerebral hematoma. Methods Sixteen adult SD rats （about 150 g） were randomly divided into experimental group （n=10） and control group （n=6）. Rat models in the experimental group were established by performing injection of 50 ~L their own venous blood into their right eaudate nucleus accurately. Rats in the control group were used normal saline, instead. After that, head MRI （T2 and T2-star scans） was performed 1, 2, 3, 7 and 14 d after the injection; their imaging features were compared. Results Nine rats in the experimental group survived and 1 died after the operation; in the early days （within 3 d）, the T2 weighing imaging showed that the time of relaxation surrounding the hematoma was longer than that in control group, suggesting that the zone of the edema surrounding the hematoma became more clearly. In the early days （within 3 d）, T2-weighted imaging was clear, and the time of relaxation surrounding the hematoma increased rapidly, steadily improved 3 d after the operation and reached its peak level 7 d after the operation; the damage area absorption decreased steadily but turned widening 3 d later and reached the peak 7 d later. T2-star value reached the peak rapidly 3 d after the operation, and then, moderated the downturn. The rats in the control group showed no obvious signal changes under MRI, except those with needle tract injury. Conclusion Secondary injury after intra-cerebral hemorrhage shows a rapidly injury progress in the short term at first, and then, has intensify again after a stable period; the local iron diffusion trend is synchronized to the secondary injury, suggesting that iron may play a key role in the mechanism of secondary brain edema.