Micro CT检测小鼠骨微结构指标受标本通量影响的方案设计

Design of a micro-CT detection scheme for mouse bone microstructural indicators influenced by scanning sample flux

在过去几十年中,Micro CT已成为评估小动物骨骼微结构的金标准。然而Micro CT得到的定量指标会受到很多因素影响,如成像参数、重建像素大小和图像分割阈值等。为了提高相关实验准确性和可重复性,以及在各个研究间进行更可靠的比较,结合小鼠离体股骨的Micro CT实验,设计不同通量的标本及组合方案来验证骨微结构测量结果是否受其影响。结果表明,标本通量及组合方式的不同对骨微结构指标测量没有产生显著性影响,但高通量扫描会降低输出图像的质量,可能会减弱组间差异的检测能力,仍需注意其产生的影响。因此在确定实验方案前需探讨标本通量对实验结果是否产生影响,或者在整个研究中保持标本通量和标本摆放方式的一致性。

[Objective]As a nondestructive three-dimensional imaging technique,micro-computed tomography(micro-CT)is the gold standard for evaluating the microstructure of the bone cortex and trabeculae.Many factors,such as scanning,processing,and evaluation of micro-CT,may affect the measurement results of the bone cortex and trabecular microstructure.However,it is not entirely clear how these factors affect the results.Scientific research often requires a large number of specimens.Micro-CT scanning is usually time-consuming,and it is common to increase the scanning flux by simultaneously scanning multiple bone specimens(such as mouse femurs).This study investigated the effects of different scanning sample fluxes on bone morphology and trabecular microstructure parameters.In addition,the study also investigated the effects of different placement methods of specimens with the same flux on cortical and trabecular microstructure parameters and the impact on the qualities of the image.[Methods]Right leg femurs were obtained from thirty 2-month-old male CD-1(IGS)mice.One,three,and five specimen fluxes combined with parallel and circular placement methods were used to perform micro-CT scans and reconstructions under the same settings.The obtained bone trabecular parameters were bone volume fraction,bone trabecular thickness,bone trabecular number,and bone trabecular gap.The cortical bone parameters obtained were cortical bone area,cortical bone thickness,and cortical bone volume fraction.The signal-to-noise ratio of the image was calculated by comparing the signal intensities of the bone cortex and background.To analyze the impact of sample flux and sample placement on the data and the degree of impact,other data were compared with the data obtained from single scanning as the control group.[Results]The experimental results showed the following:1)Different sample fluxes affected the measurement values of the microstructure parameters in the bone cortex and trabeculae.As the sample flux increased,the volume fraction of trabeculae decreased,the thickness of trabeculae decreased,and the number of trabeculae increased.In addition,changes in trabecular space and trabecular density demonstrated no clear trend.2)The same sample flux but different sample placement methods affected the measurement values of the above parameters.However,there was no significant difference in the first and second situations.3)Although the quality of the single scanning image was the best,as the sample flux increased,the image quality decreased.Under the same sample flux,although the distance between the samples in horizontal placement was smaller than that between the samples in circular placement,the image quality of the former was better than that of the latter.[Conclusions]The sample flux and placement methods did not have a significant impact on the microstructure parameters of the bone cortex and trabeculae,however,high-flux scanning can reduce the quality of the output images,and the sample placement methods can also affect image quality.Therefore,to provide the most accurate estimation possible of bone structure,low-flux and parallel placement methods should be used for scanning.High-flux scanning may weaken the ability to detect intergroup differences.To improve the accuracy and reproducibility of the experiments,the flux and the placement method of the sample should be described in the methods.