MRI示踪成像探讨隐球菌颅内感染大鼠脑细胞外间隙扩散变化

MRI tracer imaging explore the diffusion changes of brain extracellular space in a rat model of intracranial cryptococcal infection

目的应用MRI示踪成像技术定量分析新型隐球菌颅内感染大鼠模型信号强度,探讨示踪剂在感染大鼠脑细胞外间隙扩散变化。材料与方法30只成年SD大鼠颅内原位接种A型新型隐球菌悬液建立感染模型,20只设立对照组,不做任何处理。模型组分别于造模后2、3、4周行MRI T2WI扫描,监测模型建立情况,建模成功大鼠纳入病例组。病例组和对照组大鼠颅内微穿刺注入10 mmol/L浓度的钆喷酸葡胺,于注射前(T_(0))及注射后15、45、90、120、180、240 min分别采集T1加权三维磁化强度预备梯度回波(T1 weighted imaging three dimensional magnetization prepared rapid acquisition gradient echo,T1WI 3D MP-RAGE)序列图像,动态观察示踪剂在两组大鼠脑细胞外间隙(extracellular space,ECS)扩散特点。使用ITK-SNAP软件获取扫描图像最大层面信号强度统计量,以x^(-)±s表示,比较病例组与对照组标准差之间差异,取均数及标准差平均值与时间线性关系绘制时间-信号曲线,观察两组曲线形态及走行趋势,使用独立样本t检验比较两组样本均数差异,推测ECS扩散参数λ改变及其病理生理机制。结果至造模后4周,隐球菌颅内感染模型建立成功率为73.3%。两组大鼠示踪剂注射完成后15 min图像信号强度分布均数及标准差最大,且病例组显著高于对照组。示踪扫描各时间段信号强度均数及标准差服从正态分布,T_(0)、T_(15)、T_(45)、T_(90)、T_(120)、T_(180)、T_(240)时刻两组间均值差异P值分别为:0.019、0.048、0.150、0.878、0.845、0.603、0.819,标准差差异P值分别为:0.285、0.017、0.327、0.308、0.891、0.298、0.486。结论MRI T1WI 3D MP-RAGE信号强度参数可以揭示颅内新型隐球菌感染ECS引流变化,T_(15)时刻信号强度均值及标准差可辨别隐球菌颅内感染ECS改变。

Objective:To quantitatively analyze the signal intensity of the intracranial cryptococcal infection rat model by using MRI tracer imaging,and explore the changes of the tracer diffusion in the extracellular space of the infected rats brain.Materials and Methods:A total of 30 adult SD rats were intracranial in situ inoculated with cryptococcus type A suspension to establish infection models,and 20 rats were set up as control group without any treatment.In the model group,MRI T2WI scanning was performed at 2,3 and 4 weeks after modeling to monitor the establishment of the model,and the rats successfully modeled were included in the case group.The rats in the case and control group were microinjected with 10 mmol/L of gadolinium-diethylene triaminepentaacetic acid(Gd-DTPA).T1 weighted imaging three dimensional magnetization prepared rapid acquisition echo(T1WI 3D MP-RAGE)images of before(T_(0))and 15,45,90,120,180,240 min after the injection were collected respectively.The diffusion characteristics of the tracer in the brain extracellular space(ECS)of the two groups were dynamically observed.x^(-)±s in maximum level signal strength statistic of the acquired images were extracted by ITK-SNAP software.Differences of standard deviation between case group and control group were compared.The mean,the mean of the standard deviation and their linear relation with time were taken to draw the time signal curve and the curve form and trend of the two groups were observed.The independent sample t test was used to compare the difference of mean between the two groups and the changes of ECS diffusion parametersλand pathophysiological mechanisms were speculated.Results:The success rate of modeling was73.3%.The mean and standard deviation of intensity distribution of image obtained at 15 min after injection were the largest,and the mean and standard deviation of the case group was significantly higher than that of the control group.The mean and standard deviation of each time period followed the normal distribution,and the P-values of independent sample t-test at T_(0),T_(15),T_(45),T_(90),T_(120),T_(180)and T_(240)were0.019,0.048,0.150,0.878,0.845,0.603,0.819 for mean and 0.285,0.017,0.327,0.308,0.891,0.298,0.486 for standard deviation.Conclusions:The MRI T1WI 3D MP-RAGE signal intensity parameters can reveal the changes of ECS drainage in intracranial cryptococcus neoformans infection,and the mean and standard deviation of signal intensity at T_(15)can distinguish the changes of brain ECS in in intracranial cryptococcus neoformans infection.