Basic Clinical Radiobiology 2017

Craniospinal irradiation case

• What is the physical dose in the overlap zone?

- D = 7 x 3,1 Gy + 2 x 6,2 = 33,9 Gy

• Do we exceed the spinal cord tolerance, regarding the biological dose in the overlap zone? (α/β is assumed to be 2 Gy for spinal cord late toxicity)

- EQD 2 - EQD 2 - EQD 2

= D

= 21,7 x = 12,4 x

= 27,67 Gy (7 fractions)

= 25,42 Gy (2 overlap fractions)