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Example 3: Modelling the MLC in Raystation by Raysearch
RayPhysics Manual v4.7
Leaf Ends and leaf position
•
Leaf-end shape is modelled
flat
.
•
The position of each MLC leaf pair
is calculated using a
method based on three user specified parameters: offset,
gain, curvature. Their values are derived iteratively based on
comparisons against measured data.
Transmission and Tongue & Groove effect
•
The width of the T&G area is the adjustable parameter. The
transmission under this is set to the square root of the
transmission through the leaves.
•
T&G effect only accounted for if the MLC leaf edge is exposed
into the beam the MLC portal
•
Interleaf leakage modelling is considered part of the overall
average MLC transmission
•
MLC leaf ends are modelled straight (No explicit ray-tracing
through leaf ends)
•
The MLC leaf tip position off-axis is corrected to account for
difference in nominal position and radiation field edge
•
T&G modelled using an adjustable parameter (no ray tracing)
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