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11

Tolerances δ for the local dose deviation d%(i)

Dublin 2018

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.