DIAGNOSTIC IMAGING
Lastly, the IP must be exposed to a high-intensity
(white light) lamp, which erases any remaining energy
from a previous exposure. The IP is then replaced into
the cassette and then can be re-used for the next
x-ray acquisition. 4
Artefact classification
Artefacts can be roughly classified according to the
stage of imaging where they occurred. This may
be prior to image acquisition (storage and handling
of the cassette), during image acquisition (making
of the radiograph by the user or radiographer), or
during image processing (from extraction of the IP
into the reader, to the computer processing on the
workstation). 3,4 By identifying the step where the
artefact occurred, it can be more easily corrected.
The most logical classification system may be that
utilised by Jiménez and Armbrust 3,5 who divides the
artefacts into pre-exposure, exposure, post-exposure,
reading, and workstation artefacts.
cassettes if they have not been used for a period of
time, as storage scatter can accumulate over time.
Damage to the imaging plate, “cracks” or “roller
artefacts”
Physical damage to the IP plate is usually seen as
focal or linear white artefacts on the image, and are
referred to as “cracks” or “kinks” (Figure 2). Damage
may arise from wear-and-tear over time, as the IP
is removed from the cassette during the reading
process and transported with rollers through the
reader over and over with use. Damage can also
occur if the IP is removed from the cassette during
maintenance or cleaning.
Pre-exposure artefacts
These artefacts occur before the cassette is used for
a study, and may occur with something as innocuous
as storage of the cassette.
Storage scatter
Exposure of the cassette to extraneous radiation,
such as storing the cassette nearby the x-ray unit
when it is in use, will result in a degree of exposure
of the IP. This is likened to “fogging” in film-screen
radiography. It may result in a generalised increase
in darkening of the image and may be difficult
to identify, or may result in a distinct pattern of
exposure, which may occur if the cassette was
stored behind/under a structure that attenuates
the beam (a shelf or table as examples) (Figure
1). Ways to avoid this artefact include storing the
cassettes away from the x-ray unit, and erasing the
Figure 1: Note the marked generalised increased image
darkening, as result of multiple small grey opacity speckles
on the imaging plate. There are also patterns seen within
the image, because the cassette was stored behind an
unknown object when radiographs were made.
Figure 2: Damaged imaging plate. Note the interrupted
vertical white lines on the image, medial to the right
femur, as well as two curved artefacts are also seen on
either side of the image, in the left and right-had bottom
corners. Roller marks may be similar in appearance, and
may span the entire length of the image.
Figure 3: Partial erasure artefact. The imaging plate was
not adequately erased prior to obtaining the next image.
Note the faint body marker disk visible in the left caudal
hemithorax over the cardiac silhouette as indicated by
arrow.
Issue 02 | MAY 2018 | 17