To be able to measure the shape and position of a measured object with sufficient precision, it is necessary to correct systematic errors in tomography. Several process-related effects lead to these systematic deviations. Common to all of them is the dependence on various parameters, such as cathode voltage of the X-ray tubes, the radiation spectrum that depends on it, as well as material and geometry of the measured object itself.

An example of this is beam hardening. This effect can be traced to the fact that the radiation spectrum of an X-ray tube is made up of various frequencies. Due to their higher energy, high-frequency radiation components are absorbed by the irradiated material at a lower proportion than the low-frequency ones. As shown in Figure 41, this has the effect that for a large material thickness, low-energy sections of the X-ray spectrum can even be completely absorbed, and thus only high-energy radiation impinges on the detector. Since the mathematical algorithm for 3-D reconstruction is based on the thickness dependent absorption of the entire X-ray spectrum, material areas with large radiographic length will systematically be measured as too large. This effect is known as a beam hardening artifact.