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Beam Modifiers Approximations
A line can be drawn from a sub-
source through the MLC to the
isocenter plane
In the MLC this line is split up into
many short intervals. For each
end point of an interval it is
determined whether the point
falls inside or outside tungsten
One simply sums the geometric
path lengths
X
1
and
X
2
in the leaf
material to apply an attenuation
correction
X
1
X
2
yx
e
,