Dose Course 2018_Flipping book

EPID CALIBRATION Correction factors (at this moment to be used for pretreat verifications and linac QA)

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.

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