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13.2
Gain Calibration
To compensate for non-uniformities in the X-ray detector, a gain reference image (flat field) is
used by the Corrections module to correct all images. The software must capture the flat field
image prior to acquiring images. The process of capturing the flat field image is known as gain
calibration.
Caution
IMPORTANT
13.2.1
Performing a gain calibration with Viva Pro:
Click the Gain Calibration button
1
Follow the on-screen prompts and expose when prompted. See the Viva Pro User Manual,
2
Gain Calibration, for detailed instructions.
The gain calibration sequence is shown in
Table 12
Gain Calibration Sequence
Step
Offset calibration
X-ray radiation
Repeat
18
Offset calibration should not be performed during X-ray.
For optimal results, Varex recommends 128 frames for offset calibration.
Varex recommends refreshing the offset calibration as often as possible for
optimal image quality.
The offset varies as a function of detector temperature and frame rate.
A different offset reference image is necessary for each operating mode, so each
mode should be calibrated before each acquisition.
Gain calibration requires the production of X-rays. Certain safety
precautions must be taken by the operator.
Gain calibration requires a current offset calibration. Therefore,
offset calibration should always be performed directly prior to gain
calibration.
Table
Offset Calibration must be run without X-ray beam active.
A uniform flat field with no obstructions in the path of the X-ray beam.
The radiation should ideally be at a level and technique representative
of the typical radiation dose for the X-ray detector during typical
procedures, keeping in mind the general considerations outlined above.
The preceding steps must be repeated for each imaging mode.
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Azure 3131Z - 4131Z Reference Manual
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12.
Description
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