Items tagged “artefact”

Ring artifacts are a CT phenomenon that occurs due to miscalibration or failure of one or more detector elements in a CT scanner. Less often, it can be caused by insufficient radiation dose or contrast material contamination of the detector cover 2. They occur close to the isocenter of the scan ...

RF overflow artifact causes a nonuniform, washed-out appearance to an image. This artifact occurs when the signal received by the scanner from the patient is too intense to be accurately digitized by the analog-to-digital converter. Autoprescanning usually adjusts the receiver gain to prevent th...

The CT stair-step artifact is found in straight structures which are oriented obliquely with respect to movement of the table and appear around the edges of sagittal and coronal reformatted images when wide collimations and non-overlapping reconstruction intervals are used. It is also seen in c...

Speed displacement artifact, also known as propagation velocity artifact, is a gray scale ultrasound finding that can be identified as an area of focal discontinuity and displacement of an echo deeper than that its actual position in an imaged structure. Depth determination by an ultrasound mach...

Oxygen masks are commonly visible on chest imaging, as they are generally not removed before the examination is performed.  Radiographic features Plain radiograph Oxygen masks are of soft-tissue density and may mimic lung lesions. A nebuliser mask with liquid in its cup causing an air-fluid l...