Abstract

The aim of radiotherapy is to deliver optimal dose to the tumour and a minimal dose to the normal tissues. So, in order to achieve homogenous dose distributions various devices are used among which wedge filters are the most common in external beam radiotherapy. Wedge can be classified into two types: Physical Wedge (PW) & Non-Physical Wedge (NPW). The Physical Wedge can be further divided into two types: individualized and universal wedge. On the other hand, NPW have been used on both Varian and Siemens’ accelerators as the Varian Dynamic Wedge (DW) and Siemens Virtual Wedge (VW). Later, Varian introduced the Enhanced Dynamic Wedge (EDW) to add more functionality to this modality. Varian’s Trilogy is equipped with two types of wedge filters: PW (i.e.,15⁰, 30⁰, 45⁰ and 60⁰) and EDW wedges (i.e.,10⁰, 15⁰, 20⁰, 25⁰, 30⁰, 45⁰ and 60⁰). The PW can be inserted in the treatment head in four different orientations (Left, right, in and out) whereas in EDW, dose distributions can be achieved by the motion of collimating jaw in two directions (in and out). A dosimetric comparison between PW (15⁰, 30⁰, 45⁰ and 60⁰) and EDW wedges (15⁰, 30⁰, 45⁰ and 60⁰) for two different energies (6 MV & 15 MV) at 10cm water equivalent depth were studied. Beam profiles were obtained using MatriXX Evolution (IBA Dosimetry). Isodose curves & monitor units for both type of wedges was calculated using Eclipse Treatment Planning System. The result shows higher beam hardening effect for PW compared to EDW through the thick end of the wedge. Moreover, the number of MUs used to deliver a particular dose using a non-physical wedge field is less than that used for a physical wedge field. No differences were observed in isodose curves for both type of wedges.

Keywords: Wedge, Physical Wedges, Enhanced Dynamic Wedge, Dosimetry, MatriXX Evolution.