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目的:通过立体定位仪向裸小鼠脑内直接注入MR对比剂(Gd-DTPA)和/或美蓝试剂,形成假肿瘤灶,探讨1.5TMR机显示裸小鼠脑内病变的可行性,进行相关MR信号分析,为建立1.5TMR接种胶质瘤的裸小鼠脑研究模型作准备。材料与方法:30只裸小鼠,雌雄各半,体重约20g,随机分成注射Gd-DTPA1组(1μl)、注射Gd-DTPA2组(2μl)、注射美蓝试剂1组(1μl)、注射美蓝试剂2组(2μl)、注射Gd-DTPA和美蓝试剂混合液1组(1μl)和注射Gd-DTPA和美蓝试剂混合液2组(2μl),每组各5只。裸小鼠腹腔麻醉后,固定于立体定位仪上,经颅骨缺口,用微注射器往一侧大脑尾状核部注入相应制剂,注完后行MR检查。MR扫描采用Siemens1.5T超导型MR机,头部线圈,用水模作为裸小鼠支架,将裸小鼠置于线圈中心,分别行T1WI、T2WI横断面、矢状面和冠状面扫描,SE序列。观察各组裸小鼠脑内是否可见明确异常信号及位置,测量异常信号灶的大小及信号强度,分析异常信号成因。结果:除注射美蓝试剂的2组外,其他各组裸小鼠注射侧脑内相应部位见明确可辨的假肿瘤样异常信号改变。各扫描平面假肿瘤灶均呈类圆形,分界清楚,T1WI呈周围环形高信号,中心低信号,T2WI呈低信号。假肿瘤灶与周围及对侧正常脑组织对比鲜明,两者信号强度差别有统计学意义(P>0.05)。结论:①1.5TMR机可明确显示裸小鼠脑内异常信号灶。②美蓝试剂不引起裸小鼠脑信号强度改变。③裸小鼠脑内假肿瘤灶的T1WI特征性信号改变源于对比剂浓度差别。
OBJECTIVE: To establish a pseudotumor tumor by injection of MR contrast agent (Gd-DTPA) and / or methylene blue reagent directly into the brain of a nude mouse by stereotactic apparatus and to investigate the feasibility of 1.5T MR imaging in displaying brain lesions in nude mice. Relevant MR signal analysis was used to prepare a model of a nude mouse brain for 1.5TMR inoculation of glioma. MATERIALS AND METHODS: Thirty nude mice, weighing about 20 g, were randomly divided into 2 groups: injection of Gd-DTPA1 (1μl), injection of Gd-DTPA2 (injection 2μl), injection of methylene blue (2μl) of Gd-DTPA and methylene blue reagent mixture (1μl) and 2 groups (2μl) of Gd-DTPA and methylene blue reagent mixture injection were injected in the same way. After intraperitoneal anesthesia, the nude mice were fixed on the stereotaxic instrument, and the cranial notch was used. The microinjector was injected into the caudate nucleus of the cerebellum on the side to inject the corresponding preparation. After the injection, MR examination was performed. MR scanning using Siemens1.5T superconducting MR machine, the head coil, water model as a nude mouse scaffold, the nude mice placed in the coil center, respectively, T1WI, T2WI cross-section, sagittal and coronal scan, SE sequence. Observe the naked brain in each group can be seen clearly abnormal signal and location, measure the size and signal intensity of abnormal signal focus, analyze the cause of abnormal signal. RESULTS: In addition to the 2 groups injected with methylene blue reagent, the corresponding parts of the injected brain in other groups of nude mice showed clearly identifiable false tumor-like abnormal signal changes. Each scan plane pseudophakic tumor were round, clear boundaries, T1WI showed a ring around the high signal, the center of low signal, T2WI showed a low signal. Pseudo-neoplastic tumor and surrounding and contralateral normal brain tissue contrast, the difference between the two signal intensity was statistically significant (P> 0.05). Conclusion: ① 1.5 TMR machine can clearly show the abnormal signal in the brain of nude mice. ② methylene blue reagent does not cause changes in brain signal intensity in nude mice. ③ The characteristic signal changes of T1WI in the nude mice false brain tumor originated from the difference of contrast agent concentration.