基于显微CT的骨微观三维变形场测量系统的研究

目的初步构建一套集成显微CT与力学加载装置的测试系统,结合数字体相关技术(digital volume correla-tion,DVC)实现骨组织内部微观三维变形场的测量。方法选用微型力学加载装置进行单轴压缩试验,维持载荷不变的同时对试样进行CT扫描;采用DVC方法对连续CT图像序列进行相关匹配和搜索计算,测量载荷变化前后试样内部结构沿三维方向的微观位移值;通过零位移重复扫描和刚体平移评价该系统的测量精度及准确度;利用该系统测试牛松质骨块的三维位移场分布。结果零位移重复扫描结果显示该系统测量加载方向的位移准确度最高,测量精度低于CT扫描分辨率的1/10;刚体平移结果显示计算位移标准差为0.001～0.002μm;松质骨块测试区域在600 N载荷作用下沿加载方向的微观位移范围为100.35～110.25μm,位移场呈现多层逐级分布。结论该系统能够满足数字体相关法测量位移的准确度及精度要求,能够实现骨组织内部微观结构的三维变形场测量,可以作为进一步研究骨组织内部变形分布与结构成分响应关系的测量平台。

Three-dimensional deformation field measurement system based on micro-CT images

Objective To develop a novel measurement system composed of micro-CT,mechanical loading device and digital volume correlation(DVC) technique,so as to measure the three-dimensional microstructural deformation field in bone tissue.Methods Uniaxial compression was applied on the specimen with the micromechanical loading device,and CT scans were also conducted while maintaining the same loads;then sequential CT images were matched and searched accordingly by DVC method to calculate the micro-displacement in the specimen along three directions before and after loading;repeated scanning of zero-displacement and rigid body translation were used to evaluate the accuracy and precision of the system.The three-dimensional distribution of displacement field in bovine cancellous bone was measured by the system.Results The result from repeated scanning of zero-displacement showed that the highest accuracy of measurement was performed in the loading direction and the precision was less than tenth of the CT resolution.The result of rigid body translation showed that the standard deviation was 0.001-0.002 μm.For cancellous bone specimen under the load of 600 N,the range of micro-displacement was 100.35-110.25 μm,with multilayer field distribution.Conclusions The accuracy and precision of this measurement system can meet the requirement of DVC method.It is proved that this system can be used for measuring the three-dimensional micro-deformation field in the cancellous bone and as a measurement platform for investigating the relationship between deformation distribution and structural response in bone tissue for the future research.