Siemens on Artefacts in CT scans

12/22/1989, Erlangen

So-called dubious ring structures/artefacts in brain CT

The undersigned have elaborated the following eight exclusion criteria to eliminate the possibility of ring artefacts:

The following preclude the possibility of a ring artefact:

• if there is a similar ring formation clearly visible in the MRI,
• if the rings are not round, but 'dented', i.e. obviously co-existing space-occupying masses,
• if there are deposits of glial tissue in the circular formation
• if one or more rings are not in the centre of rotation of the apparatus ("paracentral target configuration")
• if there are more circles simultaneously adjacent to each other, only one of the ring formations at most could be one ring artefact,
• if the ring formations have a clinical-radiological 'course', i.e. the sequential follow-up CTs show them at the same locations but changed.
• The device-dependent artefacts are circular or circle-segment-shaped structures around the rotation centre of the system. If such structures could possibly represent real anatomical structures, it is recommended to repeat the scan with a lateral or vertical displacement of the patient position. If the repeated tomography clearly shows the structures without relative displacement, then these are not artefacts.

Siemens AG
Medical Technology Department
Mr. Feindor
Dr. Hamer

Translated by El Glauner