Siemens SOMATOM Spirit Operator's Manual page 429

Quality Assurance
Evaluating the test
04/2012
Normally one scan is sufficient to discern the pins in the row
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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.
Adjust the window width and center to improve visualiza-
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tion (adequate starting values: 30 width / 90 center).
Observe the region where the small pins are located just
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below the two 20 mm measurement areas.
i
It may help to observe the image in a semi-darkened room and
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from distance of up to 5 feet.
Enter the resolution in the corresponding entry field of the
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content area.
Click Continue.
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Low Contrast Test (Optional)
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