Constant dose rate VMAT in Raystation
New White Paper from RaySearch Laboratories
In 2008, both Varian and Elekta received FDA clearances for their VMAT solutions. Today VMAT is a widely used treatment technique and it is usually preferred for its ability to deliver dose distributions of similar plan quality as IMRT, but with a much shorter delivery time.
The linac vendors argue that an expensive hardware upgrade is needed to be able to deliver VMAT. This upgrade includes the ability to vary the dose rate of the beam while moving the gantry and the leaves. Long before 2008 it was possible to deliver conformal arcs, where the leaves moved to maintain the target projection from all angles while the gantry rotated around the
These conformal arcs were delivered using constant dose rate and constant gantry speed. If the plan is optimized using inverse planning it is possible to utilize the ability to move the leaves to
create modulated arcs, instead of conformal arcs, even though the dose rate and gantry speed are constant
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