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虽然最近一些关于恶性脑肿瘤间质性近距离放射治疗的研究表明，与常规治疗相比，这种治疗方式的临床效果很好，但正常大脑对这种治疗方式的反应的生物学数据很少。因此，我们建立了正常大鼠脑间质照射模型系统，并从组织学上研究了对正常脑组织的影响。以成年雌性SD大鼠为研究对象。将头部固定在立体定位框架内，垂直植入右半球内一根聚乙烯导管（od =1.2 mm，长5mm），导管内含有一对Ir-192种子或假种子。辐照时间为7-10天，每粒长度为3mm的Ir-192粒子平均活度为0.5 mCi或1.0 mCi，辐照剂量分别为100 Gy或200 Gy，照射至距导管轴线3mm的参考点。用假种子进行假治疗。动物分别于辐照后立即、4周、12周和12周处死。照射后立即在照射超过400gy的区域出现凝固性坏死，水肿液外渗沿胼胝体扩散，伴有反应性星形胶质细胞。照射后4周，坏死组织内可见小的钙化灶，坏死周围的照射半球也可见明显的脱髓鞘。辐照后12周内，坏死灶未扩大，辐照量小于200gy的区域未见坏死灶。在血脑屏障通透性研究中，在献祭前15分钟静脉注射HRP （100 mg/kg）。辐照后通透性增加最为普遍，在辐照超过50 Gy的区域可见HRP在血管外积聚。电镜显示脑毛细血管内皮胞饮增多，星形细胞过程受损。综上所述，这些结果表明，间质性照射后，辐照剂量超过50 Gy的区域血脑屏障受损，而辐照剂量低于200 Gy的区域未观察到凝固性坏死。少

Although some recent studies of interstitial brachytherapy of malignant brain tumors have shown good clinical results comparing conventional therapy alone, the biological data of normal brain response to this treatment modality are scarce. Therefore, we have developed a model system for interstitial irradiation using normal rat brain, and then studied the effects on normal brain tissue histologically.Adult female SD rats were subjected to this study. With the head fixed in stereotaxic frame, a polyethylene catheter (O.D.=1.2 mm, 5 mm length) containing a pair of Ir-192 seeds or dummy seeds, was implanted in right hemisphere perpendicularly. Irradiation was performed with Ir-192 seeds of 3 mm length each with a mean activity of 0.5 mCi or 1.0 mCi, during 7-10 days, the radiation dose of 100 Gy or 200 Gy delivered to the reference point, at a 3 mm distance from the axis of the catheter, respectively. Sham treatment was performed with dummy seeds.Animals were sacrificed at immediately, 4 … More and 12 weeks after irradiation. Immediately after irradiation, coagulative necrosis was observed in the region irradiated more than 400 Gy and extravasated edema fluid had spread along the corpus callosum with reactive astrocytes. Four weeks after irradiation, small calcified foci were observed in the necrotic tissue and demyelination was also observed marked in the irradiated hemisphere around the necrosis. Within 12 weeks after irradiation, the necrotic lesion was not enlarged and not seen in the area had irradiated less than 200 Gy.In blood-brain barrier permiability study, HRP (100 mg/kg) was given intravenously 15 minutes before sacrifice. Increased permiability was most widespread at immediately after irradiation, extravascular accumulation of HRP was seen in the area had irradiated more than 50 Gy. Electron microscopy showed increased pinocytosis of the endothelium of cerebral capillary and impaired astrocytic processes.In summary these findings suggest that after interstitial irradiation, blood-brain barrier is impaired in the region irradiated more than 50 Gy and coagulative necrosis is not obserbed in the area irradiated less than 200 Gy. Less