X-Ray Computed Tomography Applications in Dimensional Metrology

X-Ray Computed Tomography (XCT) has emerged as a transformative tool in dimensional metrology, offering non-destructive three-dimensional measurement of both external and internal features of complex components. By acquiring a series of radiographic projections and reconstructing a volumetric dataset, XCT enables comprehensive characterisation of geometries that are inaccessible to conventional tactile or optical coordinate-measuring machines. The voxel-based nature of XCT affords the simultaneous capture of fine surface details and subsurface structures, supporting applications in additive manufacturing, assembly inspection, materials science and biomedical device evaluation. Advances in detector technology, image reconstruction algorithms and calibration protocols have steadily improved dimensional accuracy and measurement uncertainty, allowing XCT to supplement or replace established metrology methods. Key challenges remain in addressing artefacts such as beam hardening, scatter and detector geometry distortions, as well as in defining standardised procedures for surface determination and uncertainty estimation. Recent progress has focused on subvoxel surface extraction, uncertainty quantification for lattice structures and integration of XCT into quality-control workflows for high-value components.

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X-Ray Computed Tomography Applications in Dimensional Metrology publication trend

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Technical terms

Voxel: The smallest volumetric element in an XCT dataset, analogous to a pixel in two-dimensional imaging.

Beam hardening: An artefact wherein lower-energy X-rays are preferentially absorbed, leading to non-uniform attenuation and reconstruction errors.

Mechanical filtering effect: The smoothing of surface features caused by the finite size of a tactile probe in coordinate-measuring machines.

Subvoxel accuracy: The ability to resolve surface or feature positions with precision finer than the nominal voxel dimension.

Re-entrant feature: A geometric element, such as an overhang or internal cavity, that cannot be accessed by line-of-sight measurement methods.

References

1. Comparison of X-ray computed tomography and coordinate-measuring system dimensional measurement for additive manufacturing parts using physical and simulation methods. Measurement (2024).
2. Progress toward the Definition of X-ray Computed Tomography Accuracy in the Characterization of Polymer-Based Lattice Structures. Polymers (2024).
3. A Surface Determination Technique for Dimensional and Geometrical Analysis in Industrial X-ray Computed Tomography. Nanomanufacturing and Metrology (2024).