Comparison Between Physical Wedges And Virtual Wedges In Linac
Loading...
Date
2015-02
Authors
ZI XIANG, TAN
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Wedge is commonly used in radiotherapy to modify isodose distribution and
reduce intensity across the radiation field. There are two types of wedge for
SIEMENS linear accelerator, physical wedge and virtual wedge. Virtual wedge
replaces the procedure to mount on the physical wedge when a wedged isodose is
needed. The aim of this study is to facilitate the clinical application of the virtual
wedge in the radiotherapy. Comparison for beam profiles and percentage depth dose
of both wedges at four angles of 15°, 30°, 45° and 60° are done. Beam profiles of
field size 10 x 10 cm2 and 20 x 20 cm2 for both type of wedges is measured at 5.0 cm
depth. Percentage depth dose of both wedges for field size 10 x 10 cm2 is measured.
For beam profile comparison, the virtual wedge has similar profile gradient with the
physical wedge. For field size 10 x 10 cm2, the physical wedge exhibits lower dose
than the virtual wedge by 3.6%, 1.6%, 2.0% and 4.7% for angle 15°, 30°, 45° and
60° at 5.0 cm thin end of the wedge. Away from field size 10 x 10 cm2, at 7.4 cm
thin end of the wedge, the physical wedge shows higher dose by 7.6%, 15.8%, 26.1%
and 25.5% for angle 15°, 30°, 45° and 60°. Whereas for field size 20 x 20 cm2, the
physical wedge shows lower dose by 3.3%, 1.1%, 2.2% and 3.9% for angle 15°, 30°,
45° and 60° at 5.0 cm thin end of the wedge. For depth dose profile comparison, the
physical wedge is showing lower dose by 0.5%, 0.9%, 2.0% and 1.8% in angle 15°,
30°, 45° and 60° at 1.0 cm depth but higher dose by 1.3%, 1.6%, 2.5% and 2.2% in
angle 15°, 30°, 45° and 60° at 10.0 cm depth. In conclusion, the virtual wedge
profiles are almost similar with the physical wedge but less hardening effect and less
scatter dose outside of radiation field.
Description
Keywords
Comparison Between Physical Wedges , And Virtual Wedges In Linac