Ring artifact on low dose CT
Incidental finding on low dose noncontrast screening chest CT.
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Concentric, alternating hypo- and hyperdense ring artifacts are emanating from the isocenter of the scan in the depicted abdomen. Note that apart from the inevitable Poisson noise resulting from the low dose scan protocol the chest (where absolute amount of soft tissue and thus beam attenuation is much lower) is unaffected by this artifact.
(Depicted are: nodular hyperplasia of bilateral adrenals, steatosis and enlargement of the liver, severe atherosclerosis)
The ring artifact can be encountered even with properly functioning detectors at low dose settings. Since this is a lung screening study the protocol was optimized for the chest.