ESTRO 2024 - Abstract Book

S4844

Physics - Quality assurance and auditing

ESTRO 2024

The abutting fields tab examines field junctions’ images and evaluates the percentage dose difference at junctions compared to the homogenous surrounding dose. A background image can be subtracted to normalize the picket and fence pattern. We saw that a 9% difference corresponds to a 0.5 mm displacement at the junction. AAPM recommends a tolerance of 1 mm. We decided to set stricter values with attention level at 8% and action level at 9% (Figure2).