显微CT分辨率对松质骨微观结构及生物力学测量的影响

目的:探究不同分辨率对显微CT测量腰椎松质骨显微结构及显微有限元分析松质骨生物力学参数精确性的影响。方法:以人腰椎L5椎体标本为对象,通过显微CT扫描得到松质骨显微CT数据,扫描分辨率为14μm,通过对合并像素点将分辨率降低至28μm~224μm等,分别测量不同分辨率下,松质骨标本的结构参数;利用不同分辨率下的显微CT数据建立显微有限元模型,计算各正交异性的弹性模量,应用统计学分析比较结构参数和力学参数的在不同分辨率下的差异。结果:各参数与分辨率间相关性不尽相同,BV/TV(骨体积分数)和Tb.Th(平均骨小梁厚度)的数值大小随着分辨率的降低呈增高趋势,Conn.D(骨小梁连接度),BS/BV(骨表面积体积比),Tb.N(平均骨小梁密度)和Tb.Sp(平均骨小梁间距)随着分辨率的降低呈降低趋势。分辨率的改变对SMI(结构模型指数)和DA(骨小梁各向异性度)没有显著影响。在三个轴向上,弹性模量均随着分辨率的降低呈增高趋势,当分辨率大于126μm时,该分辨率下的弹性模量和对照组存在显著性差异(P<0.05)。结论:该实验证实了不同分辨率对显微CT测量腰椎松质骨显微结构和生物力学参数有显著影响。提示在研究腰椎松质骨显微结构和生物力学参数时,采用126μm以上分辨率,可以在不降低准确度的情况下提高运算效率。

The Effect of micro-CT Resolution on Measuring Microstructure and Mechanical Parameters of Human Lumbar Vertebral Trabecular Bone

Objective:To determine the effect of different resolution on the accuracy of the micro-CT, when measuring the microarchitectural parameters and the microscopic finite element analysis to measure the mechanical parameters of the lumbar cancellous bone.Methods:The fifth human lumbar vertebrae was scanned by micro-CT with the scanning resolution of 14 um, decreasing the resolution to 28 um~224 um through the study of the multiplication of resolution so as to obtain the reduced-resolution micro-CT data. Then, the microstructural parameters were calculated by these images and the orthotropic elastic modulus was calculated by the microscopic finite element model. Then the differences of structural parameters and calculated mechanical parameters by these micro-CT data of different resolution were analyzed.Results:Different parameters had different correlations with variations of the resolution. The value of BV / TV and Tb.Th increased, while the value of Conn.D, BS / BV, Tb.N and Tb.Sp declined when decreasing the resolution. In addition, there was no effect on the SMI and DA with variations of the resolution. The elastic modulus increased with the down regulation of the resolution in all the three axial directions, and when the resolution was above 126 um, there was a significant difference of the elastic modulus compared with the control group.Conclusion:There is a significant effect of different resolutions on the accuracy of the micro-CT, when measuring the microarchitectural parameters and the microscopic finite element analysis to measure the mechanical parameters of the lumbar cancellous bone. This study indicates that the calculating efficiency can be improved without decreasing the accuracy of measurement when the resolution is higher than 126 um.