[Metal artefact on head and neck cone-beam CT images].

There are only a few factors, where the properties of the CBCT is inferior compared to conventional CT. One of these properties is the low contrast resolution, which has an importance in the discrimination of different soft tissues. Another difference is the image quality degrading effect by metal objects. This latter factor has much higher importance in head and neck region CBCT application. The metal artifact is closely related to other types of artifacts, like beam-hardening and x-ray photon scattering artifacts. In some of the cases, metal artifacts can be avoided by the proper adjustment of the scanning parameters, but sometimes the problem overgrows the possibilities. The current pre- and post-processing algorithms used for the correction of different artifacts can improve the image quality, but these algorithms are not the ultimate solution to the problem. The introduction of iterative reconstruction algorithms into the CBCT market will effectively reduce the most CT artifacts, however, the spread of this algorithms are set back because of the insufficient computational power of today's PCs. Another advantage of the use of iterative algorithms is that the patient dose could be significantly reduced.