Accurate Measurement of Small Features in X‐Ray CT Data Volumes, Demonstrated Using Gold Grains
Accurate Measurement of Small Features in X‐Ray CT Data Volumes, Demonstrated Using Gold Grains
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DOI：
10.1029/2018jb017083
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发表时间：
2019-04
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影响因子：
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通讯作者：
R. Ketcham;A. Mote
中科院分区：
文献类型：
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作者：
R. Ketcham;A. Mote
我们提出了一种测量接近X射线计算机断层扫描（CT）数据量分辨率极限的小的离散特征的方法，目的是在仪器和数据分辨率之间提供一致的答案。由于数据点扩散函数，小特征的外观受到部分体积效应和模糊的影响，我们称我们的方法为部分体积和模糊（PVB）方法。特征被分割以包含其总衰减信号，然后将其转换为体积，进而允许使用体素的子集来测量形状和方向。我们演示了一组金颗粒的方法，用两台仪器在一系列的分辨率和各种周围介质扫描。我们准确地恢复体积超过27个范围的颗粒体积和5个范围的数据分辨率的因素，成功地表征颗粒小到5.4体素的真实体积。形状指标受分辨率效应的影响较小，并且基于基于图像的卡尺测量比周长或表面积更可靠。当最大或最小轴长度与中间轴充分不同时，方向可再现。校准需要我们凭经验获得的感兴趣材料的端元CT数;我们描述了第一原理计算并讨论了其挑战。PVB方法是准确的，可重复的，分辨率不变的，和客观的，所有重要的改进，任何基于全局阈值的方法。
We present a method for measuring small, discrete features near the resolution limit of X‐ray computed tomography (CT) data volumes with the aim of providing consistent answers across instruments and data resolutions. The appearances of small features are impacted by the partial volume effect and blurring due to the data point‐spread function, and we call our approach the partial‐volume and blurring (PVB) method. Features are segmented to encompass their total attenuation signal, which is then converted to a volume, in turn allowing a subset of voxels to be used to measure shape and orientation. We demonstrate the method on a set of gold grains, scanned with two instruments at a range of resolutions and with various surrounding media. We recover volume accurately over a factor of 27 range in grain volume and factor of 5 range in data resolution, successfully characterizing particles as small as 5.4 voxels in true volume. Shape metrics are affected variably by resolution effects and are more reliable when based on image‐based caliper measurements than perimeter length or surface area. Orientations are reproducible when maximum or minimum axis lengths are sufficiently different from the intermediate axis. Calibration requires end‐member CT numbers for the materials of interest, which we obtained empirically; we describe a first‐principles calculation and discuss its challenges. The PVB method is accurate, reproducible, resolution invariant, and objective, all important improvements over any method based on global thresholds.