In computed tomography, a three-dimensional image is generated by rotating the object in very small steps (<1°) 360 °around a single axis of rotation while taking a series of two-dimensional X-ray images. Afterwards, the final three-dimensional image is numerically reconstructed based on the two- dimensional images and is displayed either as a series of sectional images or a three-dimensional image.(see Applications.
There are two conditions essential to precise reconstruction of volume data. Firstly, the sample must remain within the beam cone at all times so that each projection image shows the complete sample. Secondly, at all times during the 360° rotation, the entire sample geometry must be 100% irradiated and imaged at the set X-ray parameters.