实验性部分兔脑组织切除术后早期影像学与病理学对照研究

目的　探讨正常脑组织部分切除术后早期的MRI特点和病理学基础。方法　选取 36只健康新西兰大白兔 ,按术后 1～ 10d的不同时间将动物分成 10个组 ,3、5、7、10d组各 6只动物 ,其余各组为 2只动物。 3%戊巴比妥耳缘静脉注射麻醉 ,无菌状态下切除右顶枕部分脑组织分别在术后1～ 10d行平扫及增强MR检查 ,随后立即取材 ,电子显微镜及普通光学显微镜下观察组织病理改变。结果　 (1)术后 2 4h术区边缘出现正常脑组织的反应性增强 ;(2 )术后一直到第 5天反应性强化程度逐渐加重 ,5d之后变化不明显 ;(3)术后 3d之内反应性增强为血脑屏障的破坏所致 ,3d之后为新生小血管和破坏的血脑屏障共同起作用 ,主要机制是新生血管数量的增加。结论　正常脑组织在术后早期反应性强化特点表现出明显的时间过程 ,在不同时间 ,血脑屏障的破坏和新生血管的数量对反应性增强所起的作用是不同的。

Correlation of MRI and histopathology after partial resection of normal brain: an experimental study in rabbits

Objective To investigate the manifestations of MR imaging and histopathology of early postoperative normal brain, and to define the correlation between MRI and histopathology. Methods Thirty six New Zealand rabbits weighing 2.0 to 3.0 kg were divided into 10 groups according to the different postoperative days: 1 to 10 day. Six animals were in groups 3, 5, 7, 10, and 2 were in the other groups. A partial resection of the parietooccipital region was performed under the usual aseptic conditions after the animals were anesthetized intravenously with 3% pentobarbital (30 mg/kg). MR imaging procedures consisted of pre and postcontrast scanning were carried out on postoperative 1 to 10 day respectively. Brain tissue samples were obtained to be prepared for examinations immediately after MR scanning. Histopathological study was made under microscope and electron microscope. The findings of MRI were compared with pathology findings. Results (1) Surgical margin contrast enhancement on MR images could be seen 24 hours after surgery. (2) The degree of contrast enhancement increased gradually before 5 days postoperatively, and no remarkable changes were present from 5 to 10 days. (3) The disruption of blood brain barrier(BBB) is the main cause of contrast enhancement during the postoperative 3 days. After that period, mechanism responsible for contrast enhancement is the formation of neovascularity and broken BBB, an increase in the number of neovascularity play a predominant role in the contrast enhancement in normal postoperative brain tissue. Conclusion The characteristics of enhanced MRI present at the surgical margin followed a typical time course during the early postoperative period. The role of neovascularity and BBB disruption in the formation of contrast enhancement at surgical margin vary with time. Knowledge of the characteristics on postoperative MR images of the normal brain can help in differentiating benign changes from malignant gliomas residual.