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目的建立恒河猴腰椎间盘缺血性退变模型并通过T1ρ自旋锁定成像和T2-mapping技术验证其可靠性。方法选取12只健康雌性恒河猴,年龄4~6岁,体重4.4~6.1 kg。每只设L5、6椎间盘作为实验组,L4、5椎间盘作为对照组。实验组于椎间盘相邻的上、下软骨终板下骨各缓慢注射平阳霉素(2 mg/mL)1 mL,对照组各注射生理盐水1 mL。于术前及术后1、4、12周采用MRI T1ρ和T2-mapping技术量化评估退变进程,术后4、12周取材行HE染色观察。结果对照组手术前后各时间点T1ρ、T2 map弛豫时间值均无明显变化,差异无统计学意义(P>0.05)。实验组T1ρ弛豫时间值于术后4周明显下降,4、12周与术前及术后1周比较差异有统计学意义(P<0.05);T2 map弛豫时间值于术后12周明显下降,与其余时间点比较差异均有统计学意义(P<0.05)。对照组与实验组间除术后4、12周T1ρ弛豫时间值及术后12周T2 map弛豫时间值比较差异有统计学意义(P<0.05)外,其余时间点两组间比较差异均无统计学意义(P>0.05)。对照组及实验组手术前后各时间点间比较以及各时间点两组间比较T2WI轴位髓核高信号区面积占整个椎间盘面积百分比,差异均无统计学意义(P>0.05)。组织学观察示,对照组各时间点椎间盘髓核及纤维环结构未见异常。实验组术后4周椎间盘髓核细胞数目减少、排列不规则;12周椎间盘髓核纤维化,内层纤维环出现裂隙改变。结论经椎体终板下骨注射平阳霉素可获得可靠的恒河猴腰椎间盘缺血性退变模型,T1ρ自旋锁定成像和T2-mapping可作为椎间盘早期退变的量化评价指标。
Objective To establish a model of lumbar intervertebral disc degeneration in rhesus monkey and verify its reliability by T1ρ spin-lock imaging and T2-mapping. Methods Twelve healthy female rhesus monkeys aged 4 to 6 years and weighing 4.4 to 6.1 kg were selected. Each set of L5, 6 intervertebral disc as the experimental group, L4, 5 intervertebral disc as a control group. In the experimental group, 1 mL of pingyangmycin (2 mg / mL) was slowly injected into the upper and lower cartilage end-plate adjacent to the disc, and 1 mL of normal saline was injected into the control group. The degeneration process was quantified using MRI T1ρ and T2-mapping techniques at preoperative and 1,4,12 weeks postoperatively. HE staining was performed at 4 and 12 weeks postoperatively. Results Before and after operation, there was no significant difference in T1 time and T2 time between two groups (P> 0.05). T1ρ relaxation time in experimental group decreased significantly at 4 weeks after operation, and there was significant difference at 4, 12 weeks before and after 1 week (P <0.05). T2 relaxation time at 12 weeks after operation Decreased significantly compared with the other time points were statistically significant (P <0.05). There was significant difference between the control group and the experimental group in T1ρ relaxation time at 4 and 12 weeks and T2 relaxation time at 12 weeks after operation (P <0.05) No statistical significance (P> 0.05). There was no significant difference in the area of disc area between the control group and the experimental group at various time points before and after surgery and at each time point between the two groups in terms of the area of the high signal area of the nucleus pulposus in T2WI (P> 0.05). Histological observation showed that there was no abnormality in nucleus pulposus and annulus fibrosus structure in control group at each time point. At 4 weeks after operation, the number of nucleus pulposus cells in the experimental group decreased and arranged irregularly. The nucleus pulposus fibrosis was found in the experimental group and the fissure in the inner annulus fibrosus was changed in the experimental group. Conclusions The reliable model of lumbar intervertebral disc degeneration can be obtained by injecting pingyangmycin into the lower end of vertebral endplate. T1ρ spin-lock imaging and T2-mapping can be used as a quantitative evaluation index of early degeneration of intervertebral disc.