T2 mapping动态定量监测兔腰椎间盘退变模型

Quantitative T2 mapping to monitor the process of lumbar intervertebral disc degeneration in a rabbit model

目的提高T2 mapping技术动态定量监测兔腰椎间盘退变模型的认识。材料与方法 18只新西兰大白兔,从脊柱侧后方手术入路暴露腰椎间盘,18 G穿刺针抽吸12只L2~3、L3~4、L4~5髓核,各约5 mg,正常L1~2、L5~6和另6只L2~5间椎间盘分别为组内和组间对照。术后第4、8、12周行MR矢状面T2WI和T2-mapping序列检查,取正中矢状面观察各椎间盘的信号,测量T2弛豫时间并与正常组比较。相应各时间点取2只L1~6间椎间盘行HE和Masson染色,观察纤维环形态、髓核细胞及基质的变化并与正常组比较。结果 18 G穿刺针经脊柱旁路于横突根部可成功穿刺抽吸髓核。6只正常兔及12只实验兔组内对照椎间盘T2WI序列为均匀高信号,12只实验兔椎间盘随术后时间延长信号逐渐降低,第4周呈稍低信号,第8周明显降低,第12周完全呈低信号。正常对照组及术后第4、8、12周组T2弛豫时间的单因素方差分析结果（F=38.82,P〈0.05）,造模术后第8周T2弛豫时间有显著差异（P〈0.05）。术后随时间进展,HE和Masson染色示椎间盘细胞和胶原逐渐减少,纤维环和髓核分界不清;第8周髓核基质退变纤维化,几乎被纤维组织取代;第12周椎间盘纤维软骨化,局部形成软骨。结论 T2mapping技术可实时定量监测腰椎间盘的退变进程。

Objective： To improve the recognition of quantitative T2 mapping to dynamically monitor the process of lumbar intervertebral disc degeneration in a rabbit model. Materials and Methods： The nucleus pulposus of L2—3, L3—4 and L4—5 discs of 12 rabbits were aspirated by using a 18 G needle and the normal L1—2, L5—6 discs of each rabbit and the discs between L2—5 vertebral body of 6 rabbits acted as the normal intra and inter control groups, respectively. The rabbits were performed with sagittal MR T2 WI and T2 mapping sequences scanning at the pre-and-postoperative 4 th, 8 th, 12 th week, respectively. The signal intensity of each disc was evaluated and T2 relaxation time was measured carefully. The discs between L1—6 were dissected and then performed with HE and Masson trichrome staining to evaluate the form of discs, content change of nucleus pulposus cells and matrix between normal and experimental groups. Results： The nucleus pulposus could be punctured successfully with a 18 G needle in the root of transverse process via spinal bypass. The normal discs manifested with uniform high signal in T2 WI. The signal intensity decreased sharply at the 8 th week and became completely low signal intensity at the12 th week post-operation. The significant difference of T2 relaxation time foundbetween normal control groups and experimental groups after 4, 8 and 12 weeks was analysed by one-way ANOVA, and the result was F=38.82（P〈0.05）. The T2 relaxation time at the 8 th week post-operation was significantly different（P〈0.05）. The results of HE and Masson staining showed that the cells and matrix decreased gradually, moreover, the boundary between annulus fibrosus and nucleus pulposus became obscure. The nucleus pulposus displayed the process of fibrosis and was almost replaced by fibrous tissue at 8 th week. The discs was fibrocartilage and local cartilage can be observed at the 12 th week. Conclusions： T2 mapping can be used to dynamically monitor the process of lumbar intervertebral disc degeneration.