The X-ray tube (open or sealed) produces a conic beam of electron that penetrates the object to be analyzed, and a digital signal is interpreted by the 2D detector as a Digital Radiograph image.
The object is positioned on a precision rotational stage and an image is acquired during the rotation at a constant step. The step is usually 0.25 degree to 1 degree (1440 to 360 images). The scan usually covers a rotation of 360 degrees, but for specific applications a limited angle scan can be performed.

From a series of 2D Radiographs and after calibration, the CT reconstruction software provides 3D volume results using Filtered Back-Projection algorithm (Feldkamp). 3D CT data are rendered as voxels (volume element) with three-dimensional resolution from a few micrometers (microCT) to hundreds of micrometers depending on X-ray detector pixel size.
3D volume results can then be exported as:

• 2D CT slices, for high resolution slice by slice inspection, measurements, density analysis, or
• 3D surface model (triangles, point clouds), for Reverse Engineering, Rapid Prototyping, CAD comparison, modeling.

CT brings more data than any other NDT technique available in the industry.

Steps :

Video:Acquisition

Video: Reconstruction

Video: Slices

For more information see CT Applications