Validation of Motorized Wedge Effective Isodose Angle with a 2D Array Detector

Abstract

Introduction: Elekta Versa HD linear accelerator is equipped with a universal wedge filter which is a single large physical wedge driven by motors; in other words, motorized wedge. It provides a nominal wedge isodose angle of 60° for the field size of 30×40 sq. cm. Motorized wedge isodose distribution generated is a combination of open and wedged beam segments. With this background in mind, the present study aimed to validate the planned wedge effective isodose angle. Material and Methods: The current study validated the planned wedge effective isodose angle for  15°, 30°, 45°, and 60°  with 6MV and 15MV for 10x10 sq. cm and 20x20 sq. cm field size. To this end, an analytical formula was applied against a 2D array detector using PTW MultiCheck software. Results: As illustrated by the obtained results, the calculated, measured, and planned wedge effective isodose angle in this work represented a maximum deviation from its pre-set angle (a nominal wedge angle) of  9° for a 6MV photon energy and 5° for 15MV for field sizes of 10×10 sq. cm and 20×20 sq. cm. Conclusion: In the present study, we validated the planned wedge effective isodose angle for field sizes of 10x10sq. cm and 20x20sq. cm for 6MV and 15MV photon energies using an analytical method and 2D array detector with a reasonable agreement.