扩展生物医学微计算机断层扫描的动态范围以应用于地质材料。

Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada.

Department of Earth Sciences, Western University, London, ON, Canada.

J Xray Sci Technol. 2019;27(5):919-934. doi: 10.3233/XST-190511.

BACKGROUND

X-ray computed tomography (CT) can non-destructively examine objects by producing three-dimensional images of their internal structure. Although the availability of biomedical micro-CT offers the increased access to scanners, CT images of dense objects are susceptible to artifacts particularly due to beam hardening.

OBJECTIVE

This study proposes and evaluates a simple semi-empirical correction method for beam hardening and scatter that can be applied to biomedical scanners.

METHODS

Novel calibration phantoms of varying diameters were designed and built from aluminum and poly[methyl-methacrylate]. They were imaged using two biomedical micro-CT scanners. Absorbance measurements made through different phantom sections were fit to polynomial and inversely exponential functions and used to determine linearization parameters. Corrections based on the linearization equations were applied to the projection data before reconstruction.

RESULTS

Correction for beam hardening was achieved when applying both scanners with the correction methods to all test objects. Among them, applying polynomial correction method based on the aluminum phantom provided the best improvement. Correction of sample data demonstrated a high agreement of percent-volume composition of dense metallic inclusions between using the Bassikounou meteorite from the micro-CT images (13.7%) and previously published results using the petrographic thin sections (14.6% 8% metal and 6.6% troilite).

CONCLUSIONS

Semi-empirical linearization of X-ray projection data with custom calibration phantoms allows accurate measurements to be obtained on the radiodense samples after applying the proposed correction method on biomedical micro-CT images.

背景

X 射线计算机断层扫描（CT）可以通过生成物体内部结构的三维图像来对物体进行无损检测。虽然生物医学用微 CT 的普及为扫描仪提供了更多的使用机会，但由于束硬化，致密物体的 CT 图像容易出现伪影。

目的

本研究提出并评估了一种简单的半经验束硬化和散射校正方法，可应用于生物医学扫描仪。

方法

设计并制造了新颖的不同直径的校准体模，由铝和聚甲基丙烯酸甲酯制成。使用两种生物医学微 CT 扫描仪对其进行成像。通过不同体模部分进行的吸收测量拟合到多项式和逆指数函数，并用于确定线性化参数。在重建之前，将基于线性化方程的校正应用于投影数据。

结果

当使用校正方法对所有测试对象应用这两种扫描仪时，实现了对束硬化的校正。其中，基于铝体模的多项式校正方法提供了最佳的改进效果。对样本数据的校正表明，使用 Bassikounou 陨石的微 CT 图像（13.7%）和先前使用岩相薄片（14.6%8%金属和 6.6%硫铁矿）进行的研究结果在致密金属夹杂物的体积百分比组成方面具有高度一致性。