Evolution of Micro-CT


depending on the type of material, or a requirement to use higher x-ray energy, oſten at the cost of a larger spot size and thus decreased resolu- tion. For the most part micro-CT, where spatial resolutions below 10 μm are possible, will use ener- gies below ∼240 kV. Additionally, mixed material systems, especially ones with a wide variance in atomic weight (that is, metal wires in a rub- ber matrix), may create imaging artifacts due to the vastly different x-ray attenuations of the materi- als relative to one another. Several examples of static (non-dynamic) CT data are shown in Figure 2.


From 3D to 4D: Adding the Temporal Component In general, the greatest advan-


tage of micro-CT worth comes from its non-destructive nature. Te abil- ity to investigate internal structures of a sample without cutting it open has been extremely beneficial in several areas, for instance, failure analysis and quality control in com- mon industrial applications [10]. Te continued development of cor- relative workflows, where CT data are used to better educate an inves- tigator on where to examine a part at higher resolution through physi- cal cross section techniques, that is, FIB-SEM, has also become a very valuable tool


in materials and life


science characterization [11]. How- ever, one of the most exciting uses for micro-CT over the last several years has been to leverage the non- destructive nature to investigate temporal events, allowing one to track the 3D evolution of a structure as it undergoes some type of change. Whether through applying an exter- nal load, that is, compression/ten- sion, inducing a change in material through thermal effects, or mixing and interaction of fluids in a porous network, the ability to understand these changes in 3D will be a great boon to scientists and researchers across many fields.


Dynamic versus Time-Lapse In situ experimentation with


micro-CT has led to a great num- ber of new insights into how things change when subjected to different


30


Figure 2: Examples of CT data. (Clockwise from top left) Segmented AA alkaline battery, metal in an integrated cir- cuit (IC) package, weathered concrete, Rhinoceros beetle, and an entire human skull. Scale bars for reference only.


www.microscopy-today.com • 2021 May


Figure 1: Top: basic schematic of typical micro-CT system with an x-ray source (left), rotating sample (center), and detector (right). Bottom: 2D projections (left) are collected at multiple angles and processed by a recon- struction algorithm to produce 2D slices through the sample (center), which can then be visualized and analyzed in 3D (right).


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