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Parameters for clinical outcome: Brain

Irradiation type (partial organ unless otherwise stated)

Dose (Gy), or dose/volume parameters

Volume segmented

Notes on dose/volume parameters Data at 72 and 90 Gy, extrapolated from BED models

Endpoint

Rate (%)

Dmax <60 Dmax = 72 Dmax = 90

<3 5 10

Symptomatic necrosis

Whole organ

3D-CRT

Whole organ

SRS (single fraction) Symptomatic necrosis

V12 <5–10 cc

Rapid rise when V12 > 5–10 cc

<20

   + = 1 2 2

   α d dN BED + 1 / 1 β

  

  

120

⋅ =

D

Gy 60 2/ 120

D

=

=

1

1

1

• High sensitivity for fraction doses > 2 Gy • High sensitivity for multi fractions per day treatments • Evidence for neurocognitive injury is weak in adults • For children the cutoff for neurocognitive injury is about 18-24 Gy (whole brain irradiation for medulloblastoma)