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EPID CALIBRATION
Correction factors (at this moment to be used for pretreat verifications and linac QA)
DEPENDING ON THE DETECTOR: DIFFERENT CORRECTION FACTORS CAN BE EXPECTED
Field size
Backscatter from the EPID arm (Varian aS500, aS1000).
Not needed for aS1200 (backscatter shielding added)
EPID SAG if used at different gantry angles
THE INTENSITY AT EACH POINT IN THE IMAGE MUST BE CALIBRATED IN A
QUANTITATIVE SENSE
The dose response of each pixel point must be known
The effects of scattered radiation in the detector must be understood
The temporal stability of the detector must be known.