AbstractID: 6673 Title: Comparision of contralateral breast dose using physical
wedge and virtual wedge in the tangential treatment technique
Studies have shown that the scatter radiation to the contralaeral breast may play
an important role in the induction of secondary breast cancers. Reports have shown
that standard wedges are used to improve the dose distribution in the treated breast,
but unfortunately introduce an increasing scatter dose outside the treatment field, in
particular to the contralateral breast. The virtual wedge, which could decrease the
scatter dose in theory, is created by moving jaw through the treatment field with
varying dose rates during dose delivery.
The data collected are measurements with a Rando Phantom using Siemens Primus
Linac equipped with both standard wedge and virtual wedge. TLD chips were placed
at predetermined location outside the treatment field, in particular to the location
within the contralateral breast. The treatment technique used is isocentric method with
a half beam technique. A comparison of the dose to the contralateral breast is then
made with the virtual wedge vs standard wedge.
The measurement shows a significant reduction in the contralaterial breast dose with
the virtual wedge as compared to that with the standard wedge. The average dose,
ranging from 1 to 7 cm to the geometric field edge, was 3.7% which is lower than that
of the standard wedge. The virtual wedge is a effective clinical device which
improves the dose distribution in patients undergoing breast treatment while at the
same time minimizing dose to the contralateral breast, thereby reducing the potential
of carcinogenic effects.