目的：磁化传递效应成像是一种新的磁共振成像技术，是目前分子影像学领域的热门研究方向，核奥氏效应（Nuclear overhauser enhancement，NOE）以及酰胺质子转移（APT）是两种特殊的MT成像方法。本研究在7.0T磁共振上探究NOE及APT加权成像。方法：将生鸡蛋清、胎牛血清白蛋白（BSA）、柠檬汁置于试管，将C6胶质瘤细胞接种至大鼠右侧基底节区，7.0T磁共振扫描仪在连续波预饱和下的PRESS序列用不同的预饱和能量进行扫描，射频能量分别为0.6、0.8、1.0、1.3、1.6、2.0、3.0 μT。同时用连续被预饱和下的EPI序列扫描出正常鼠以及胶质瘤大鼠的MT图。以上偏置频率为5～-5 ppm，其中扫描参数：TR 6 000 ms，TE 26.51 ms，RF持续时间为4 s。结果：生鸡蛋清以及BSA均可以观察到比较明显的NOE及APT效应，而柠檬汁则观察不到NOE效应，只能观察到APT效应。且随着能量的增大，APT效应明显增强，而NOE效应明显减弱；在RF预饱和能量<1.0 μT时，NOE效应相对较大，而APT效应相对较小，当能量>1.0 μT时则表现为相反的结果。对于大鼠而言，表现为相同趋势。NOE及APT加权图（NOER及APTR）提示大鼠胶质瘤肿瘤中心区域NOE效应下降，APT效应增强。结论：NOE及APT的观察需要较恰当的参数，其中预饱和能量的大小对两种效应的影响较大。太小及太大的预饱和能量都会影响两种效应。本实验首先证实了富含蛋白质的物质可以观测到两种效应，并且观测到胶质瘤大鼠肿瘤区域NOE效应下降而APT效应增强，从而猜测肿瘤区域的效应变化可能与蛋白质分子的浓度有关。
Abstract
Objective: Magnetization transfer(MT) imaging has recently emerged as a new and hot field for MRI in cellular and molecular imaging. Nuclear overhauser enhancement(NOE) and amide proton transfer(APT) are two special types of MT imaging. Our study is to image NOE and APT weighted MT imaging at 7.0T. Methods: Fresh egg white, bovine serum albumin(BSA), fresh lemon juice were put in tubes respectively for pre-experiment. C6 glioma cells were cultivated to plant in the rats’ right basal ganglia for making tumor models. We scanned these tubes and rats using a continuous wave pre-saturating PRESS sequence(CW-PRESS sequence). B1 was 0.6, 0.8, 1.0, 1.3, 1.6, 2.0, 3.0 μT. At the same time, we acquired rats’ MT imaging using CW-EPI sequence. The RF offset ranges from 5～-5 ppm. The parameters were set up as follows: TR 6 000 ms, TE 26.51 ms, RF duration time 4 s. Results: NOE and APT effect were obviously observed in egg white and BSA, but NOE effect wasn’t observed in lemon juice. NOE signal declined and the APT signal heightened with the increase of B1, particularly when B1<1.0 μT, NOE signal was relatively strong and APT signal was relatively small. When B1> 1.0 μT, these showed the opposite results. This tendency corresponds to that of glioma rats whose NOE signal declined and APT signal heightened. Conclusion: There must be proper parameters to acquire NOE and APT images. B1 makes a big contribution to them, even too big or too little B1 can’t get clear NOE and APT images. We firstly demonstrated the protein made contribution to NOE and APT effect and then got the decision that NOE signal declined and the APT signal heightened in glioma. Hence, we suspected that these variations were related to protein concentration.
关键词
神经胶质瘤 /
磁共振成像
Key words
Glioma /
Magnetic resonance imaging
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基金
国家自然科学基金重点项目（编号：30930027）。
