Physics Bucharest 2017

Issues?

How to manage uncertainties? Can we use the PTV concept?

• In particle therapy target alignment is only a partial solution!

• PTV works for photons since the spatial nature of photon dose distributions is minimally perturbed by uncertainties –( Maleike et al PMB 2006 ) Hp: the CTV will BE 95% of the times INSIDE the PTV → the PTV dose distribution and DVH are the worst case scenario for the CTV

• Patient misalignment + density heterogeneities → dose SHIFT+ DISTORSION

→ Particle dose distribution is significantly perturbed (DEFORMED) not only distally or proximally, but within and outside the target volume → The PTV-based optimization do not consider range uncertainties. It considers setup uncertainties implicitly but ignores the deformation of dose distributions caused by them.