The X-ray tomography system belongs to the “hard-field” tomography system. The
path of measurements signal between source and detector is constant, it does not change
under the influence of material distribution in measurements space (as took place for ECT
tomography). X-ray radiation generated by source is going through object (in our case silo)
and achieves detector. During this way radiation is attenuated by the object and number of
photon on detector is smaller than emitted by source. The information about level of X-ray
radiation attenuated allows to distinguish area of object with lower and higher density. The
basic equation describing the attenuation of X-ray radiation determines Beer-Lambert law
[1, 7], presented in equation (6):