In external radiation therapy we use wedges for beam modification. The virtual wedge factor is 0.9 or we can say approximately equal to 1 so then how we can replace it by Physical/external wedges? If the physical wedge factor is 0.7 and virtual wedge factor is 0.9 then there is 20% difference. So how we can replace physical wedge by virtual wedge?
Dear Siddique Shah
I assume that by "virtual wedge" you refer to the Virtual Wedge feature on a Siemens linac. Siemens effectively renormalised the definition of monitor units with the aim of geting a wedge factor of 1.00, although in practice they can be 5% either way from that. If you are measuring a wedge factor of 0.9, I suspect that something has gone wrong with your machine - possibly the calibration of the MON2, since that is used by VW. This can affect both wedge factor and wedge angle.
Once you have determined that the VW is behaving correctly, I agree that modelling both the VW and the physical wedge in your planning system is the best way to predict the effect of changing wedges.
best wishes
Simon
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