Question

A radiobiology experiment is performed in the porcine model. The tumor cells can be assumed to be spherical and have a diameter of 20 microns on average, and they occupy 20 cm3. This volume is exposed to a uniformly distributed radiation that deposits a dose 2 Gy per fraction. The energy of the radiation is such that an active event corresponds to about 80 eV. The tumor cells obey the linear-quadratic survival model. It is observed that at a dose of 1 Gy the relation between the two constants α and β is α = 2β. Calculate the relative significance of the chromosome breaks due to a single charged particle vs due to two separate charged particles expressed in terms of the survival fraction?

Answer 1

According to linear-quadratic survival model,

S = exp (D+ D ² )

D + D ² = D _{1 +} D ₁² = E

E/ = n d ( 1+ d/  / )

where, d – dose per fraction, n – number of fractions, will be evaluated separately for tumor cells.

E/ = 2 1 ( 1+ 2 / 2 )