152 MI-42-0001 Rev. 19
MAINTENANCE: Daily Gain Calibration
7.3 Daily Gain Calibration
7.3.1 Overview
Calibrate Calibrations should be performed daily or according to the responsible organization’s procedure.
A gain calibration scan consists of a scan of the air. Gain calibrations auto-correct gain and offset
settings for 120 kV, 100 kV, and 80 kV scans before diagnostic scans begin.
NOTES:
• Performance checks are not a substitute for scheduled periodic maintenance performed by
an authorized service technician.
• Systems with the Pediatrics feature disabled only run 120 kV Daily Gain Calibration.
This section describes the steps for performing gain calibration.
Definition Calibration is an image correction procedure to preserve image quality. Calibration corrects for
inherent pixel-to-pixel gain variations, non-uniform background or offset signals, and non-linearities
in the response of the scanner to the X-ray dose. The non-uniformity of the X-ray beam is corrected
to provide a lower noise image across the detector array. [Source: ASTM WK7492 2008]
CT numbers are NOT absolute; misdiagnosis is possible. System and patient
variables may effect CT Number accuracy. If you rely solely upon CT numbers without
taking the following variables into consideration you could mis-diagnose an image.
The following variables effect CT Number accuracy:
• Partial volume effects of anatomy
• X-ray tube deterioration
• Improperly calibrated system (poorly centered phantom, used wrong phantom, replace current
calibration files with extremely old calibration files).
• Beam hardening due to patient anatomy, especially bone.
To reduce CT Number variations:
• Warm-up the X-ray tube whenever the system recommends it.
• Center the patient anatomy of interest in the Ring opening. Select a Field of View that
encompasses the patient.
7.3.2 Preparing for Calibration
How to Prepare for
Calibration
Steps See
1.
Move AIRO to an area suitable
for performing CT scans.
3.3.8
2.
Ensure that no objects, including
the table, are in the scan area.
• MI-42-0167 AIRO Original Trumpf Column
Supplement section 3.3.2.
Or
:
• MI-42-0165 AIRO Updated Trumpf Column
Supplement section 3.3.2
For information about which integrated column your
AIRO features, see chapter 4 COLUMN AND TABLE.
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