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目的探讨骨质疏松SD大鼠模型的骨密度(bone mineral density,BMD)、MR化学位移率(chemical shiftratio,CSR)变化与骨髓脂肪含量变化的相关性。材料与方法将60只12周龄SD大鼠(雌雄各30只)等分成A、B、C、D4组,分别进行去势手术和假手术。每组大鼠随机等分成两组,分别于手术后12周、16周行双能X线(dual-energy X-ray absorptiometry,DXA)BMD检测,多层螺旋定量CT(quantitative CT,QCT)BMD检测和MR化学位移成像(chemical shift imaging,CSI)计算CSR。所有动物均在MR实验研究后进行髂骨区域松质骨取样,标本行细胞成分分析,计算脂肪百分含量(FF%)。结果去势12周,雌性大鼠去势组与假手术组之间全身DXA-BMD差异有统计学意义(P=0.028<0.05),QCT-BMD差异有显著统计学意义(P=0.007<0.01);去势16周时,全身DXA-BMD、QCT-BMD差异均无统计学意义(P>0.05)。去势12周、16周时,雄性大鼠去势组与假手术组之间全身DXA-BMD、QCT-BMD差异均有明显统计学意义(P<0.01)。雌、雄大鼠不同组别间CSR差异无统计学意义(P>0.05)。大鼠松质骨QCT-BMD与FF%呈负相关关系(r=-0.587,P<0.001),CSR与FF%呈负相关关系(r=-0.358,P=0.011),CSR与QCT-BMD呈正相关关系(r=0.338,P=0.016)。结论骨质疏松状态下,松质骨脂肪含量增加、BMD减少,CSR随着容积骨量的减少而减少。
Objective To investigate the relationship between changes of bone mineral density (BMD) and chemical shiftratio (CSR) in the rat model of osteoporosis and bone marrow fat content. Materials and Methods Sixty 12-week-old SD rats (30 males and 30 females) were equally divided into groups A, B, C and D4 for castration and sham surgery respectively. The rats in each group were randomly divided into two groups. BMD was detected by dual-energy X-ray absorptiometry (DXA) at 12 weeks and 16 weeks after operation. BMD was detected by quantitative CT (QCT) MR Chemical shift imaging (CSI) calculates CSR. All animals were sampled in cancellous bone of iliac region after MR experimental study. Specimens were analyzed for cell composition and percent fat (FF%) was calculated. Results The whole body DXA-BMD in ovariectomized and sham-operated groups was significantly different at 12 weeks after ovariectomy (P = 0.028 <0.05). There was significant difference in QCT-BMD (P = 0.007 <0.01) ). There were no significant differences in DXA-BMD and QCT-BMD between the two groups at the 16th week (P> 0.05). At 12 weeks and 16 weeks after ovariectomy, there were significant differences in the whole body DXA-BMD and QCT-BMD between castration group and sham operation group (P <0.01). There was no significant difference in CSR among different groups of female and male rats (P> 0.05). There was a negative correlation between QCT-BMD of cancellous bone and FF% (r = -0.587, P <0.001), negative correlation between CSR and FF% (r = -0.358, P = 0.011) There was a positive correlation (r = 0.338, P = 0.016). Conclusion In the condition of osteoporosis, the contents of cancellous bone fat increased, BMD decreased and CSR decreased with the decrease of volume bone mass.