X-ray Micro Tomography

X-ray Tomography allows a 3D reconstruction from a series of 2D radiographs, each for a different angular position of the sample, and this can be done even down to sub-micron resolution.

Typically, a full tomographic data set will require in the order of few hundreds to a few 1000s radiographs using 3D reconstruction and the Feldkamp algorithm. Optical Cone beam / fan beam reconstruction is used, with the sample rotating in a fixed plane / helicoidally around an axis perpendicular to the beam.

The total acquisition time is in the range of few seconds per frame, and this can be dependent very much on the source brilliance / geometry. 100% duty cycle detectors with simultaneous read out / exposure allows to save up to 50% of the scanning time. Resolution down to a few hundred nanometres can be achieved by using a small focal spot source and reasonable geometric magnification. The recorded data is often several Gigabytes and can be processed using the massively parallel calculation capacity of GPUs.

Micro tomography can be combined with phase contrast imaging, either in a qualitative way (“edge enhancement”) or, more quantitatively, including phase retrieval (“holotomography”). Very high-resolution cameras allow the build of scanners with sub micrometre spatial resolution whilst keeping compact dimensions and good sensitivity.

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