Dosimetric Characteristic of Enhanced Dynamic Wedges used in Radiation Therapy

Modern linear accelerators are equipped with a dynamic wedge option. It is a form of dose distribution which makes use of dynamic movement pairs of collimator jaws to improve the dose uniformity from the target. The aim of this study is to compare the calculated and measured dosimetric properties of enhanced dynamic wedges used in radiation therapy. The effect of enhanced dynamic wedge on the photon beam produced by Varian 2100C accelerator was studied with the EGSnrc Monte Carlo code. Depth doses and beam profiles for wedged photon beams were obtained for 6 and 15 MV. Four standard wedge angles of 15o, 30o, 45o and 60o were modelled in this study. Various field sizes were defined at 100 SSD in water phantom. Data calculated with our simulation model and measurements agreed well within 2 % for all wedges. The calculated wedge dose profiles matched very well with the measurement, except at the toe area of 60o wedge angle for 2020 cm2. The observed wedged PDD increased with increasing wedge angle, field size and decreasing the beam energy. The results evidently showed that the Monte Carlo simulation is a useful method for evaluating the dosimetric properties of enhanced dynamic wedge.