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目的探讨3.0 T MRI水-脂成像动态评估原发性骨质疏松鼠模型骨髓脂肪含量的可行性。方法 18只12周龄雌性SD大鼠随机分为假手术组(SHAM)及去卵巢组(OVX),每组9只。分别在基线(0周)、6、12周行MRI水-脂分离成像及骨密度(BMD)扫描,获取骨髓脂肪分数(FF)及BMD值。第12周时行ELISA测定血清17β雌二醇及骨转换标记物(BALP及CTX-Ⅰ)。评价两次扫描FF测量的可重复性及不同观察者的一致性。结果两次MRI扫描FF值变异系数为2.95%。两位独立观察者测量FF值,组内相关系数为0.928(95%CI为0.841~0.967,P<0.001)。第6、12周时,OVX组FF较基线时分别增高40.0%、69.4%(P值均<0.001)。第6周始组间FF差异有统计学意义,而组间BMD至第12周时差异有统计学意义(P值均<0.001)。OVX组血清17β雌二醇降低67.2%,且BALP及CTX-Ⅰ标记物均较SHAM组增高,呈高转换型。结论大鼠去势12周骨质疏松模型可建立,MRI水-脂成像可动态评估骨髓脂肪含量。
Objective To investigate the feasibility of dynamic evaluation of bone marrow fat content in primary osteoporosis rat model by 3.0 T MRI-H2O imaging. Methods Eighteen 12-week-old female Sprague-Dawley rats were randomly divided into sham-operated group (SHAM) and ovariectomized group (OVX), 9 in each group. The bone marrow fat fraction (FF) and BMD were obtained at baseline (0 week), 6,12 weeks respectively by MRI water-fat separation imaging and bone mineral density (BMD) scan. Serum 17β-estradiol and bone turnover markers (BALP and CTX-Ⅰ) were determined by ELISA at week 12. Evaluate the repeatability of two scan FF measurements and the consistency of different observers. Results The coefficient of variation of FF value of two MRI scans was 2.95%. Two independent observers measured FF values with a correlation coefficient of 0.928 (95% CI 0.841 to 0.967, P <0.001). At the 6th and 12th week, FF in OVX group increased by 40.0% and 69.4% respectively compared with baseline (P <0.001). There was a significant difference in FF between the 6th week and the 12th week after BMD (P <0.001). Serum estradiol 17β decreased 67.2% in OVX group, and BALP and CTX-Ⅰ markers were higher than SHAM group, showing high conversion type. Conclusion The model of osteoporosis can be established in rats after ovariectomized for 12 weeks. MRI-lipid-lipid imaging can dynamically assess the content of fat in bone marrow.