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Input data – “general” to PB electron
calculations
❑
Measured Depth–Dose Distributions
o
Depth dose distributions for electron beams of a given E
0
are extremely
dependent on the particular beam transport system (scattering foils or
scanning system, applicator design. etc.) of the user’s accelerator. The
Fermi–Eyges model requires central-axis depth– dose distributions for
a number of different rectangular field sizes –
g
(
z
)
❑
Dose Profiles
o
A dose profile is required in order to derive the weighting factor W (x,y).
This should be measured at or near d
max
in a principal plane across the
larger field dimension for each field for which the CAXD (z ) is required.
❑
Mean Energy at the Surface, E
0
❑
The Initial Angular Spread
o
This parameter can be determined from in-air measurements of the
penumbra at different distances from the collimator using film
(Hogstrom et al. 1981).
Dublin 2018
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