Field output correction factors of stereotactic cones for a diode detector: Dependence on cone size, measurement setup, reference field size and photon energy.

This study investigated if field output correction factors (FOCFs) of Varian stereotactic cones for Edge detectorTM had dependence on cone size, measurement setup, reference field size and/or photon energy. Field output factors (FOFs) of stereotactic cones were measured at three depths (1.5 cm, 5 cm and 10 cm) in two different setups (source-to-surface distance (SSD) and source-to-axis distance (SAD)) with two photon energies (6 MV and 6 MV flattening filter free) using the Edge detector and Exradin_® W2 scintillator. Two reference fields (10 × 10 cm² and 4 × 4 cm²) were chosen. FOCFs for the Edge detector were determined by calculating FOF_W2/FOF_Edge and compared among cones and between depths, setups, reference fields and energies. It is concluded that FOCFs for the Edge detector have dependence on cone size, SSD/SAD setup and energy for small cones, but do not have dependence on depth and reference field size.