Palanca Marco, Bodey Andrew J, Giorgi Mario, Viceconti Marco, Lacroix Damien, Cristofolini Luca, Dall'Ara Enrico
Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Terracini 24/28, Bologna 40131, Italy.
Diamond Light Source, Oxfordshire OX11 0QX, UK.
J Biomech. 2017 Jun 14;58:27-36. doi: 10.1016/j.jbiomech.2017.04.007. Epub 2017 Apr 20.
Understanding bone mechanics at different hierarchical levels is fundamental to improve preclinical and clinical assessments of bone strength. Digital Volume Correlation (DVC) is the only experimental measurement technique used for measuring local displacements and calculating local strains within bones. To date, its combination with laboratory source micro-computed tomography (LS-microCT) data typically leads to high uncertainties, which limit its application. Here, the benefits of synchrotron radiation micro-computed tomography (SR-microCT) for DVC are reported. Specimens of cortical and trabecular bovine bone and murine tibiae, were each scanned under zero-strain conditions with an effective voxel size of 1.6μm. In order to consider the effect of the voxel size, analyses were also performed on downsampled images with voxel size of 8μm. To evaluate displacement and strain uncertainties, each pair of tomograms was correlated using a global DVC algorithm (ShIRT-FE). Displacement random errors for original SR-microCT ranged from 0.024 to 0.226μm, depending on DVC nodal spacing. Standard deviation of strain errors was below 200 microstrain (ca. 1/10 of the strain associated with physiological loads) for correlations performed with a measurement spatial resolution better than 40μm for cortical bovine bone (240μm for downsampled images), 80μm for trabecular bovine bone (320μm for downsampled images) and murine tibiae (120μm for downsampled images). This study shows that the uncertainties of SR-microCT-based DVC, estimated from repeated scans, are lower than those obtained from LS-microCT-based DVC on similar specimens and low enough to measure accurately the local deformation at the tissue level.
了解不同层次水平的骨力学对于改善骨强度的临床前和临床评估至关重要。数字体积相关技术（DVC）是唯一用于测量骨内局部位移和计算局部应变的实验测量技术。迄今为止，它与实验室源微型计算机断层扫描（LS - microCT）数据的结合通常会导致高度不确定性，这限制了其应用。在此，报告了同步辐射微型计算机断层扫描（SR - microCT）用于DVC的优势。对皮质和小梁牛骨以及小鼠胫骨的标本在零应变条件下进行扫描，有效体素大小为1.6μm。为了考虑体素大小的影响，还对体素大小为8μm的下采样图像进行了分析。为了评估位移和应变的不确定性，使用全局DVC算法（ShIRT - FE）对每对断层图像进行相关性分析。原始SR - microCT的位移随机误差范围为0.024至0.226μm，具体取决于DVC节点间距。对于皮质牛骨（下采样图像为240μm）测量空间分辨率优于40μm、小梁牛骨（下采样图像为320μm）和小鼠胫骨（下采样图像为120μm）进行的相关性分析，应变误差的标准偏差低于200微应变（约为与生理负荷相关应变的1/10）。这项研究表明，基于重复扫描估计的基于SR - microCT的DVC的不确定性低于基于类似标本的基于LS - microCT的DVC的不确定性，并且低到足以准确测量组织水平的局部变形。
