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10
Tolerances δ for the local dose deviation d%(i)
Warsaw 2017
Region
Homogenous,
simple geometry
Complex geometry
(wedge, inhomogeneity,
asymmetry, blocks / MLC)
More complex
geometries****
δ
1
Central beam axis data
– high
dose, low dose gradient
2%
3%
4%
δ
2
*
Build-up region of central axis
beam, penumbra region of the
profiles -
high dose, high dose
gradient
2 mm
or
10%
3 mm
or
15%
3 mm
or
15%
δ
3
Outside central beam axis
region
- high dose, low dose
gradient
3%
3%
4%
δ
4
**
Outside beam edges
– low
dose, low dose gradient
30% (3%)
40% (4%)
50% (5%)
RW
50
***
Radiological width
– high
dose, high dose gradient.
2 mm or 1%
2 mm or 1%
2 mm or 1%
δ
50-90
Beam fringe
– high dose,
high dose gradient
2 mm
3 mm
3 mm
Adopted from Venselaar, 2001
(normalized at central axis same depth)
The tolerances, if applied to the confidence
limit, can be exceeded in two ways; either
because the mean deviation of all points is too
large
or because a few data points show extreme
deviations and therefore the SD is too large.