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syngo CT 2007E Emotion Operator Manual
02/2008
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Low Contrast Test (Optional) Quality Assurance
F.5-6
Evaluating the test
F.5
Normally one scan is sufficient to discern the pins in the row
with the smallest diameter (3 mm). However, the procedure
may be repeated if desired. Low contrast measurements are
directly effected by the level of noise (“sigma”) in the CT system,
which may vary from scan to scan within a specified range. Low
contrast estimations involve visual verification methods that
are somewhat subjective. It is normal to expect some variations
in assessing low contrast of the smallest (3 mm) pins.
F.5
✧ Adjust the window width and center to improve visualiza-
tion (adequate starting values: 40 width / 90 center).
✧ Observe the region where the small pins are located just
below the two 20 mm measurement areas.
i
.5
F
It may help to observe the image in a semi-darkened room and
from distance of up to 5 feet.
F.5
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