Assertion: metal artifact | /r/HasProperty | severe
Facets:
Source sentences:
text: However, three major difficulties can be pointed out for that methods: (1) the well-formatted original raw projection data are often unavailable because the leading manufacturers of CT imaging devices are often reluctant to provide it; (2) the involved high computational cost of iterative algorithms often requires an implementation on specialized processor units; (3) the iterative algorithm still need to be combined with sinogram correction method when the metal artifacts are rather severe.