定量DCE-MRI和QCT评价兔糖尿病模型骨髓微血管渗透性和骨小梁改变的相关性

Quantitative DCE-MRI and QCT were used to evaluate the bone marrow microvascular permeability and trabecular changes in diabetic rabbit models induced by alloxan

目的采用动态对比增强磁共振成像(dynamic contrast enhanced MRI,DCEMRI)与定量计算机断层扫描(quantitative computed tomography,QCT)定量评价四氧嘧啶诱导兔糖尿病模型骨髓微血管渗透性和骨小梁改变。材料与方法 24只3.0 kg左右雄性日本大耳白兔随机分为糖尿病组(14只)和对照组(10只)。造模成功后各时间点(0、4、8、12、16周)对所有兔腰椎行矢状位FSE-T1WI、FSE-T2WI、DCE-MRI检查与CT成像。通过拟合药代动力学模型获得腰椎骨髓DCE-MRI定量渗透参数,包括容量转移常数(volume transfer constant,K^trans)、速率常数(efflux rate constant,Kep)和容积分数(extracellular extravascular volume fraction,Ve)。同时用QCT软件测量腰椎骨密度(bone mineral density,BMD)。16周取腰椎体标本行苏木精-伊红染色法(hematoxylineosinstaining,HE)计算骨小梁形态计量学参数,包括骨小梁数量(Tb.N)、骨小梁面积(Tb.Ar)。结果不同时间点渗透参数Kep、Ve在对照组差异分别具有统计学意义(P均<0.001),而在糖尿病组差异均无统计学意义(P值均>0.05)。对照组腰椎Kep在第4周到12周呈下降趋势,Ve在第4周到12周呈上升趋势,第16周下降。不同时间点BMD在对照组及糖尿病组差异均不具有统计学意义(P>0.05)。第16周糖尿病组腰椎HE染色显示骨小梁数量、面积减小。糖尿病组骨小梁面积、骨小梁数低于对照组(t=12.472;t=4.961;P<0.001)。Pearson相关分析结果显示Tb.N与K^trans、Kep、Ve均无相关性(r值分别为0.135、0.093、-0.118;P>0.05),Tb.Ar与K^trans、Kep、Ve均无相关性(r值分别为0.233、-0.008、-0.095;P>0.05)。BMD与K^trans、Kep、Ve均无相关性(r值分别为0.497、0.513、-0.310;P>0.05)。结论四氧嘧啶兔糖尿病早期腰椎骨髓微血管渗透性参数变化与骨密度和骨小梁形态计量学参数无相关性,QCT测量的骨髓BMD变化晚于骨小梁形态计量学的变化。

Objective:To quantitatively evaluate the bone marrow microvascular permeability and trabecular changes induced by alloxan in diabetic rabbit model via dynamic contrast enhanced MRI (DCE-MRI) and quantitative CT (QCT).Materials and Methods:Eighteen rabbits were randomly divided into the diabetes group (n=14) and the control group (n=10).Fse-T1WI,Fse-T1WI,DCE-MRI examination and CT imaging were performed at each time point (0,4,8,12 and 16 weeks) after the model had been established successfully.DCEMRI quantitative perfusion parameters of lumbar bone marrow were obtained by fitting the pharmacokinetic model,including volume transfer constant (K^trans),efflux rate constant (Kep) and extracellular extravascular volume fraction (Ve).QCT software was applied to measure Lumbar vertebral density (BMD).Lumbar vertebral specimens were collected at week 16 for HE staining to calculate the morphometric parameters of bone trabeculae,including the number of bone trabeculae (Tb.N) and the area of bone trabeculae (Tb.Ar).Results:Osmotic parameters Kep and Ve at different time points indicated statistically significant differences in the control group (P<0.001),which was not significant different in the diabetes group (P>0.05).In the control group,the Kep of lumbar spine showed a descending trend from week 4 to week 12,while Ve displayed an rising trend from week 4 to week 12 and declined from week 16.There was no significant difference in BMD between the control group and the diabetes group at different time points (P> 0.05).The results of HE staining exhibited that the number and area of bone trabeculae were decreased in the diabetic group at week 16.The trabecular bone area and trabecular bone count was lower than that of the control group (t=12.472,t=4.961,P<0.001).Pearson correlation analysis results showed that there was no correlation between Tb.N and K^trans,Kep and Ve (r values:0.135,0.093 and -0.118),as well as Tb.Ar and K^trans,Kep and Ve (r values:0.233,-0.008 and -0.0.095,P>0.05).No significant correlation was observed between BMD with K^trans,Kep and Ve (r values:0.497,0.513 and -0.310,P>0.05).Conclusions:The changes of bone marrow microvascular permeability parameters of the lumbar spine in diabetes mellitus rabbits induced by alloxan in the early stage of disease were not correlated with bone mineral density and trabecular morphometrics parameters,and the differences of bone marrow BMD measured by QCT were later than those of bone trabecular morphometrics.