X-Ray Micro Computed Tomography (Micro-CT)
Technique:
Similar to a hospital CAT scanning system, Micro Computed Tomography (Micro-CT) is a non-destructive 3D imaging technique (4-D with time-based measurements) that uses a highly energetic X-Ray beam to create a series of 2D projections, whose greyscales vary with the volume’s internal density and atomic number variations. These projections are reconstructed to create a virtual 3D model, allowing users to “see” inside the sample without preparing, sectioning or destroying the sample.
In principal, Micro-CT directs onto a sample a beam of X-Rays that are generated within an X-Ray source; these X-Rays are transmitted through the sample. The efficiency of transmission is dependent on density and atomic number variations within the sample volume, such that higher atomic number materials will transmit less X-Rays than low atomic number materials. The transmitted X-Rays are then magnified onto and recorded by a planar detector as a 2D projection. The sample is rotated by a fraction of a degree and another 2D cross-section image is recorded, which is repeated up to 360 degrees. This series of images is then computed and “reconstructed” into a high-resolution 3D volume, showing internal density variations within the sample.
Instrument:
Zeiss Xradia 410 Versa Micro-CT
System Capabilities:
- Minimum spatial resolution of 0.9 µm and a minimum voxel size of 100 nm at larger working distances
- Variable X-Ray voltage from 0 to 150 kV
- Variable X-Ray power from 0 to 10 W
- Automated objective carousel, with objectives: 0.4x, 4x, 10x, 20x
- Advanced absorption and phase contrast capability (for soft or low atomic number materials) overcomes the limitations on traditional computer tomography
- Vertical stitching mode enables the analysis of taller samples by joining tomographies from different sections of the sample
- The in-situ tensile stage (500 N) enables measurements while the samples are under tensile or compression stresses
Selected Applications in Industry:
- Corrosion analysis within an alloy
- Distribution of porosities in metals, oil reservoir rocks, and other samples
- Phase contrast analysis of internal phases
- Failure analysis of large intact circuit boards and other 3-D packages
- Non-destructive reverse engineering of obsolete Integrated Circuit packages
- Defects in polymers and paint coatings
- Imaging/mapping of biological, pathological, and neural networks