【作者】 陈浩；

【导师】 蒋震；

【作者基本信息】 苏州大学 ， 影像医学与核医学（专业学位）， 2018， 硕士

【摘要】 目的:利用磁共振成像（Magnetic Resonance Imaging,MRI）兼容的OxyLite^TM荧光淬灭氧电极验证稳态自由进动功能磁共振成像技术（Steady-State Free Precession functional MRI,SSFP fMRI）检测肿瘤组织内氧含量变化的可靠性。材料与方法:30只雄性SD大鼠接受皮下C6胶质瘤细胞悬液接种。选择肿瘤长径大于3cm的荷瘤鼠,麻醉固定后在瘤体内置入带有金属标记的磁共振兼容的OxyLite^TM荧光淬灭氧电极（Oxford Optronix,Oxford,UK）。采用荷兰Philips公司生产的Ingenia 3.0 T超导磁共振成像设备及8通道全数字光纤传输小关节包裹线圈,在空气及Carbogen气体间断性呼吸激励时行SSFP fMRI扫描的过程中,同步记录氧电极所在肿瘤组织内的局部氧分压（pO₂）值的动态变化。将SSFP图像导入Linux系统,经AFNI软件（Analysis of Functional NeuroImages,https://afni.nimh.nih.gov/）进行非血流动力学响应函数（non-hemodynamic response function,non-HRF）图像后处理。在SSFP图像上依据金属标记定位出氧电极尖端,并以此为圆点定义直径为2mm的球形ROI。提取该观测点ROI的SSFP信号在Carbogen气体吸入前后的变化显著性参数T值及信号强度变化百分率PSC值,并与氧电极记录并计算得到的该观测点在吸入Carbogen气体前后氧分压均数的差值（ΔpO₂）进行相关性检验。结果:最终共顺利记录了19只肿瘤的24个观测点的SSFP fMRI数据及同步的pO₂变化数据。以“中位数（四分位间距）”表示的结果如下:pO_2-air=0.495（5.350）mmHg,pO₂-car=0.490（14.898）mmHg,ΔpO₂=0.550（5.130）mmHg,,T value=2.326（6.735）,PSC value=0.857（3.269）%。Carbogen吸入后pO₂的平均值显着增加（Wilcoxonz=3.329,p=0.001）。24个测量点的ΔpO₂值与其相应ROI区测得的T值（Spearmanr=0.474,p=0.019）和PSC值（Spearmanr=0.463,p=0.023）均呈显著性相关。结论:SSFP fMRI技术可以较可靠地评估大鼠C6胶质瘤组织内部氧含量变化,具有间接的检测肿瘤内乏氧情况的潜在价值。更多还原

【Abstract】 Objective: Tumor hypoxia is one of the key factors that affect the efficacy of radiotherapy.Thus,the ability to detect dynamic changes in oxygen saturation level within tumor is of great importance.Steady-state free precession(SSFP)sequence has recently been employed for functional MRI(fMRI).In our study,we aim to verify the reliability of SSFP fMRI for detecting oxygen saturation level changes.To achieve this,we compare image signal variations with direct measurements obtained from rat C6 glioma using MRI compatible fiber-optic microprobes.Materials and Methods: A total of 30 male Sprague-Dawley rats were used to establish the subcutaneous C6 glioma model.MRI compatible OxyLiteTM fiber-optic microprobes were embedded in the tumor after anesthesia.The rats were then examined in the prone position using a clinical 3.0 T whole-body MRI system(Ingenia,Philips Healthcare,the Netherlands).A dStream small extremity 8-channel coil was used for signal reception.Acquisition parameters were as follows: TR/TE=6.9ms/3.4ms;flip angle=70°;FOV=80mm×80mm;acquisition matrix=136×134;slice thickness=2mm(four slices);number of dynamic scans=100.SSFP fMRI scans were performed with Carbogen inhalation while a series of tissue pO2 values were recorded simultaneously in real time using the fiber-optic microprobes.Image data was processed using non-hemodynamic response function(non-HRF)analysis provided by AFNI software.A spherical region of interest(ROI)with a 2mm diameter was placed at the tip of the fiber-optic microprobe to determine the T value and percentage signal change(PSC).The mean difference of pO2(ΔpO2)before(pO2-air)and after(pO2-car)Carbogen inhalation in the ROI was calculated.The difference between pO2-air and pO2-car was tested by Wilcoxon matched-pair signed rank test.Lastly,we investigated the correlation between ΔpO2 and T value,as well as between ΔpO2 and PSC.Results: We obtained p O2 values before and after Carbogen inhalation at 24 different locations in the tumor region during SSFP fMRI scan.The experimental results,shown in the format of [median(interquartile range)],were as follows: pO2-air= 0.495(5.350)mmHg,pO2-car=0.490(14.898)mmHg,Δp O2=0.550(5.130)mmHg,T value=2.326(6.735),PSC value=0.857(3.269)%.The mean value of p O2 significantly increased after Carbogen inhalation(z=3.329,p=0.001).The mean value of ΔpO2 measured at all of the 24 tumor locations correlated positively both to T value(Spearman’ r=0.474,p=0.019)and PSC value(Spearman’ r=0.463,p=0.023).Conclusions:To conclude,fMRI using steady-state free precession(SSFP)is able to track changes in oxygen saturation level in rat glioma,and hence has the potential to detect tumor hypoxia.更多还原