Ring artefacts in cranial CT

Description 

A ring or arc artefact in a CT is a hardware related artefact that occurs due to a defective or miscalibrated detector. It is more common with third-generation CT scanners with solid-state detectors. It appears as complete circles (sequential scans), annular rings (multiple circles) or partial rings (helical/multislice CT) at the same spot near the isocentre in multiple sections.1 2 Recognising this artefact is important as it may be subtle and misinterpreted as a pathological entity by the novice clinician.3 This artefact is usually more clearly visualised in the soft-tissue window of CT scans (video 1) than in the bone window (video 2).

Video 1

Serial sections of the scan (soft-tissue window) showing ring artefact.

Video 2

Serial sections of the scan (bone window) showing ring artefact.

Presented here is a case where an...

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